Proposed in 1954 by Gell-Mann, Goldberger, and Thirring, crossing symmetry postulates that particles are indistinguishable from anti-particles traveling back in time. Its elusive proof amounts to demonstrating that scattering matrices in different crossing channels are boundary values of the same analytic function, as a consequence of physical axioms such as causality, locality, or unitarity. In this talk we report on the progress in proving crossing symmetry on-shell within the framework of perturbative quantum field theory. We derive bounds on internal masses above which scattering amplitudes are crossing-symmetric to all loop orders. They are valid for four- and five-point processes, or to all multiplicity if one allows deformations of momenta into higher dimensions at intermediate steps. As usual we will have our informal coffee meeting before the talk to simulate a coffee corner discussion. The zoom room will already be open from 3:30pm on. Feel free to join any time before the talk.

Although gauge redundancy is a fundamental feature of any gauge theory, any physical observable that we compute must be gauge invariant. One way to combat gauge redundancy is to reformulate the theory in terms of gauge invariant quantities, as is commonly done in cosmological perturbation theory. In this talk, I will discuss how to systematically formulate perturbation theory in gauge invariant variables to all orders in perturbations, via homotopy transfer in the framework of L-infinity algebras. In particular, I will show how this method can be applied to cosmological perturbation theory.

Dimensional reduction has played a central role in many of the developments in the understanding of string theory and M-theory. Some dimensional reductions are simple and easily understood, such as reduction on a circle or torus. Some are more subtle, such as the reduction of D=11 supergravity on S^7 to give four-dimensional gauged N=8 supergravity. It became clear that the consistency of such reductions was intimately associated with supersymmetry, and more recently, with double field theory. But it was conjectured in 1986, and proven in 2015, that non-trivial group manifold consistent reductions of the effective action for the bosonic string in any dimension also exist, and for these true supersymmetry obviously cannot play a role. The arbitrary-dimensional bosonic string can nevertheless be pseudo-supersymmetrised (i.e. supersymmetry modulo quartic fermion terms), and this can provide a way to understand the consistent reductions. In recent work, we have shown that the N=1 supersymmetric extension of DFT for the bosonic string extends also to a pseudo-supersymmetric DFT, in arbitrary dimension, which draws together the strands of the consistent truncation story.

W-algebras associated to simple Lie algebras are non-linear generalisations of the Virasoro algebra, from which certain CFTs can be defined. Using a formalism of Kontsevich and Soibelman and representation theory of W-algebras via free fields (when this exist), one can construct from them systems of PDEs whose solution is computed by a topological recursion. Such solutions carry information about 2d (worldsheet) geometry, and topological recursion mean this information is reached by induction on the Euler characteristic that resembles a cutting/pasting approach. They are sometimes expressible as integrals on the moduli space of complex curves or as topological string A-model amplitudes (for certain target spaces), and gives suitable definition of topological string B-model for certain type of complex 1d singularities. I will give an overview of these connections, and describe if time permits sketch a more recent link (ongoing work) to Nekrasov partition functions in 5d gauge theories (in which W-algebra are known to appear since Alday-Gaiotto-Tachikawa proposal). This is based on joint works with Andersen, Chekhov, Orantin, Bouchard, Chidambaram, Creutzig, Noshchenko, Kramer, Schüler.

The manifestly O(D,D) symmetric formulation known as Double Field Theory (DFT) has proven very useful in many contexts. I will address the problem of constructing higher derivative invariants in this formalism. In agreement with the literature we find that a quadratic Riemann invariant can be constructed, which can account for the first alpha' correction to the bosonic and heterotic string. However, we find that no cubic or quartic Riemann invariants can be constructed. This suggests that the quartic Riemann terms arising at order alpha'^3 in string theory do not have a DFT embedding.

Gopakumar, Ooguri and Vafa have related Chern-Simons invariants of the unknot to topological strings A-model on the resolved conifold, via geometric transitions. This has been extended to torus knots by Brini, Eynard, Marino. I will explain a further generalisation to basic knots in S^3/ADE. The relevant geometry on the B-side are spectral curves of relativistic Toda systems of type ADE, which can be accessed by a matrix model analysis, while on the A-side the candidate geometry is a non-toric CY3. One can then prove that the large N all-order expansion of HOMFLY invariants is described by a topological recursion on the B-model geometry. I will describe some current puzzles about extending this to Seifert spaces beyond S^3/ADE.

Drell-Yan production of a charged lepton pair is a key process at the Large Hadron Collider. The region of large invariant mass region is of particular interest for new physics searches, which motivates precise theory predictions at energies well above the Z resonance. In this talk, I discuss our recent calculation of the mixed electroweak-QCD two-loop amplitudes for the process qq->l+l- as a further step in this direction. I present the calculation in two different approaches, the ’t Hooft-Veltman-Breitenlohner-Maison (HVBM) gamma5 scheme and Kreimer's anticommuting gamma5 scheme, and discuss how one arrives at scheme-independent results. In the HVBM scheme, we restored chiral symmetry using local counter terms, where we found it essential to consistently calculate them to higher orders in (d-4).

At the J-PARC KOTO experiment, we are searching for a rare decay, KL -> pi0 nu nu-bar, to study new physics beyond the Standard Model. With the data taken from 2016 to 2018, we recently set an upper limit of 4.9E-9 (90% CL) on the branching ratio of the decay, based on 3 observed events and 1.22 +- 0.26 background events. At the KAON2019 Conference, we showed 4 events in the signal box because that is what we observed when we opened the box. Since we did not understand the origin of those events, we simply reported the facts, and did not present any physics results. However, many theorists called it “KOTO anomaly”. By studying further, we later discovered two new background sources. This talk presents experimental explanation of the KOTO anomaly

We will show how a real scalar quantum field theory (QFT) on the noncommutative Moyal space is approximated by a so-called matrix field theory (MFT). The advantage of these models is that we are able to give exact expressions for the expectation values which coincides with the renormalized perturbation theory. The most prominent example of a MFT is the Kontsevich Model (phi^3), which was introduced to prove Witten's conjecture on the generating series of intersection numbers of the moduli space of complex curves. The algebraic structure of the Kontsevich model is captured by Topolgical Recursion (TR), a structure appearing in different areas of mathematics and physics. We will discuss that the renormalization procedure of QFT preserves the TR structure of the Kontsevich model. We will continue with the phi^4 model known as the Grosse-Wulkenhaar model, which has a richer algebraic structure. The loop insertion operator is introduced with its perturbative action. We conclude that certain combinations of expectation values satisfy the enriched structure of Blobbed Topological Recusion, and finish with an example for the 2D QFT model on the Moyal space.

The canonical approach for tackling higher-order computations involves splitting up a finite quantity into two separately divergent ones. First, multiloop amplitudes are evaluated using (mostly) analytical techniques. Second, phase-space integrals are computed using numerical Monte-Carlo techniques with ad-hoc subtraction terms for regularising soft and/or collinear infrared divergences. We will present our recent work, Local Unitarity, in which we propose a radically different technique whereby the singularities in real-emission and virtual degrees of freedom directly cancel without the use of any counterterms and at any perturbative order. On the practical side, this allows for the fully numerical computation of differential corrections, potentially alleviating the complexity bottleneck analytical alternatives are facing. From a theoretical standpoint, our proof of the local cancellation of infrared singularities sheds new light on the exact mechanism by which it is realised.

I will describe the four-derivative corrections to four-dimensional N=2 minimal gauged supergravity and show that they are controlled by two constants. Interestingly, the solutions of the equations of motion in the two-derivative theory are not modified by the higher-derivative corrections. I will use this to arrive at a general formula for the regularized on-shell action for any asymptotically locally AdS_4 solution of the theory and show how the higher-derivative corrections affect black hole thermodynamic quantities in a universal way. I will employ these results in the context of holography to derive new explicit results for the subleading corrections in the large N expansion of supersymmetric partition functions on various compact manifolds for a large class of three-dimensional SCFTs arising from M2- and M5-branes. I will also briefly discuss possible extensions and generalizations of these results.

High energy particle collisions are an ideal framework for accessing new information on matter constituents and forces of Nature. Advances in Theoretical Physics depend on our ability to describe the scattering processes among elementary particles at very high accuracy. Theoretical Physicists calculate scattering amplitudes, numbers that are related to the probabilities of different aftermath of particle scattering, which encode the chance that a given set of particles will turn into certain other particles after an impact. Feynman graphs are a convenient way to represent particle collisions. The mathematical methods required to describe scattering events which take place from the smallest to the largest scale of the Universe benefit from concepts borrowed from the rich research in mathematical disciplines, such as (differential and algebraic) Geometry, Topology and Number Theory. In this seminar, I elaborate on the diagrammatic approach to Fundamental Interactions via Scattering Amplitudes and Feynman integrals, and on their algebraic properties which have been recently understood to be ruled by Intersection Numbers: a novel connection between Physics and Mathematics.

With null results in resonance searches at the LHC, the physics potential focus is now shifting towards the interpretation of non-resonant phenomena. An example of such shift is the increased popularity of the EFT programme. We can embark on such programme owing to good integrated luminosity and an excellent understanding of the detectors, which will allow these searches to become more intense as the LHC continues. In this talk I will explain a framework to perform this interpretation in terms of a diverse set of scenarios, including 1.) generic heavy new physics described at low energies in terms of a derivative expansion, such as in the EFT approach, 2.) very light particles with derivative couplings, such as axions or other light pseudo-Goldstone bosons, and 3.) the effect of a quasi-continuum of resonances, which can come from a number of strongly-coupled theories, extra-dimensional models, clockwork set-ups and their deconstructed cousins.

We will discuss the deformation theory of nearly G2-manifolds. After defining nearly G2-manifolds, we will describe some identities for 2 and 3-forms on such manifolds. We willintroduce a Dirac type operator which will be used to completely describe the cohomology of nearly G2-manifolds. Along the way, we will give a different proof of a result of Alexandrov-Semmelman on the space of infinitesimal deformation of nearlyG2structures. Finally, wewill prove that the infinitesimal deformations of the homogeneous nearly G2-structure on the Aloff–Wallach space are obstructed to second order. The talk is based on a joint workwith Ragini Singhal (University of Waterloo).

The analiticity properties of correlation functions and scattering amplitudes are tied to the causality of the physics these observables describe. In particular, an imprint of causality is provided by the validity of Steinmann relations, which require that the double discontinuities of scattering amplitudes in partially-overlapping momentum channels vanish in the physical region. However, our world is not flat but cosmological, and how causal time evolution is encoded in cosmological observables is far from being understood. In this talk, I will report on recent progress in addressing such an issue in the context of the class of scalar toy models whose wavefunctions of the universe admit an ab-initio description in terms of cosmological polytopes. A distinctive feature of this description is that the singularities of the wavefunction are associated with the facets of the cosmological polytopes, with the total energy singularity, notoriously related to the flat-space physics, related to the scattering facet. I will show that the combinatorics and geometry of the cosmological polytopes lead to the emergence of the Steinmann relations for the S-matrix on the scattering facet, as well as similar relations also hold for the wavefunction itself. Both this set of relations arise via the very same mechanism and rely on the intrinsic definition of the cosmological polytopes themselves.

String theory can be well-defined on spaces without a geometric description. A certain class of such backgrounds is called non-geometric and can be characterized in terms of non-geometric fluxes. Compactifying string theory in the presence of non-geometric fluxes may give rise to stable de-Sitter vacua, however, this is in conflict with the Swampland De-Sitter Conjecture which states that such vacua should not exist in any consistent theory of quantum-gravity. The main purpose of this talk is to address this issue: I will first briefly review non-geometric flux compactifications and revisit known de-Sitter constructions based on non-geometric fluxes. I will then argue for a condition on the tadpole contributions, which excludes known non-geometric de-Sitter vacua.

I will discuss the factorisation and the subtraction of infrared singularities for scattering amplitudes and cross sections relevant for collider phenomenology. In particular, I will focus on the relation between the factorisation of soft and collinear poles in fixed-angle scattering amplitudes and the construction of local counterterms for singular contributions to real radiation. This approach leads to general definitions of soft and collinear counterterms to all orders in perturbation theory, and suggests promising simplifications for the construction of subtraction algorithms beyond NLO.

We will start by discussing a flow of isometric G2-structures. We consider the negativegradient flow of the energy functional restricted to the class of G2-structures inducing agiven Riemannian metric. We will discuss various analytic aspects of the flow includingglobal and local derivative estimates, a compactness theorem and a monotonicity formulafor the solutions. After defining an entropy functional we will prove that low entropy initialdata lead to solutions that exist for all time and converge smoothly to a G2-structure with divergence free torsion. We will also discuss finite time singularities and the singular set ofthe solutions. Finally, we will discuss the isometric flow ”coupled with the Ricci flow of the underlying metric, which again is a flow of G2-structures (and is a specific example of a familyof flows of G2-structures which we have introduced), and discuss some of its properties. This is a based on two separate joint works with Panagiotis Gianniotis (University of Athens)and Spiro Karigiannis (University of Waterloo)

Parametric Feynman integrals are complicated objects and it is generally hard to evaluate them analytically. In contrast to that, these integrals are surprisingly well-suited for numerical evaluation: I will explain how an underlying (tropical) generalized permutahedron geometry, which the Symanzik polynomials respect, allows this very efficient numerical evaluation. I will also sketch how a parametric representation of renormalized Feynman integrals by Brown and Kreimer together with `tropical Dyson-Schwinger equations' indicates a way to similarly fast evaluations of whole Feynman amplitudes.

Over the next years, measurements at the LHC and the HL-LHC will provide us with a wealth of data. The best hope of answering fundamental questions like the nature of dark matter, is to adopt big data techniques in analyses and simulations to extract all relevant information. At the analysis level, machine learning methods have already shown impressive performance boosts in many areas like top tagging, jet calibration or particle identification. On the theory side, LHC physics crucially relies on our ability to simulate events efficiently from first principles. In the coming LHC runs, these simulations will face unprecedented precision requirements to match the experimental accuracy. Innovative ML techniques like generative models can help us overcome limitations from the high dimensionality of the parameter space. Such networks can be employed within established simulation tools or as part of a new framework. Since neural networks can be inverted, they also open new avenues in LHC analyses.

Entanglement and entropy are key concepts standing at the foundations of quantum and statistical mechanics. In the last decade the study of the non-equilibrium dynamics of isolated quantum systems revealed that these two concepts are intricately intertwined. Although the unitary time evolution ensuing from a pure initial state maintains the system globally at zero entropy, at long time after the quench local properties are captured by an appropriate statistical ensemble with non zero thermodynamic entropy, which can be interpreted as the entanglement accumulated during the dynamics. Therefore, understanding the post-quench entanglement evolution unveils how thermodynamics emerges in isolated quantum systems. Zoominar link: https://mpi-aei.zoom.us/j/97623339163

Efficient numerical algorithms for the construction of one-loop amplitudes have played a crucial role in the automation of NLO calculations, and similar algorithms at two-loop level are highly desirable in order to achieve the precision of theoretical predictions required for the LHC. Numerical tools construct the numerator of loop integrals in four dimensions, while the missing contributions stemming from the interplay of (D-4)-dimensional numerator parts with 1/(D-4) poles have to be reconstructed separately. At one-loop level a well-established method is to restore these contributions through process-independent rational counterterms. In this talk we extend the concept of rational terms of UV origin to two loops. We present a master formula for the computation of D-dimensional two-loop scattering amplitudes from amplitudes with four-dimensional numerators and a finite set of universal rational counterterms. A generic method to compute such rational terms from simple tadpole integrals will be discussed, as well as the renormalisation scheme dependence of rational terms. Finally, we present the complete set of two-loop rational terms in SU(N) and U(1) gauge theories in a generic renormalisation scheme.

Entanglement entropy quantifies the amount of uncertainty of a quantum state. For quantum fields in curved space, entanglement entropy of the quantum field theory degrees of freedom is well-defined for a fixed background geometry. In this paper, we propose a generalization of the quantum field theory entanglement entropy by including dynamical gravity. The generalized quantity named effective entropy, and its Renyi entropy generalizations, are defined by analytic continuation of a gravitational path integral on replica geometry with a co-dimension-2 brane at the boundary of region we are studying. We discuss different approaches to define the region in a gauge invariant way, and show that the effective entropy satisfies the quantum extremal surface formula. When the quantum fields carry a significant amount of entanglement, the quantum extremal surface can have a topology transition, after which an entanglement island region appears. Our result generalizes the Hubeny-Rangamani-Takayanagi formula of holographic entropy (with quantum corrections) to general geometries without asymptotic AdS boundary, and provides a more solid framework for addressing problems such as the Page curve of evaporating black holes in asymptotic flat spacetime. We apply the formula to two example systems, a closed two-dimensional universe and a four-dimensional maximally extended Schwarzchild black hole. We discuss the analog of the effective entropy in random tensor network models, which provides more concrete understanding of quantum information properties in general dynamical geometries. By introducing ancilla systems, we show how quantum information in the entanglement island can be reconstructed in a state-dependent and observer-dependent map. We study the closed universe (without spatial boundary) case and discuss how it is related to open universe. Zoom Link: https://mpi-aei.zoom.us/j/94382199742

Composite Higgs models are Beyond the Standard Model approaches involving a strongly coupled sector in which the Higgs particle is a Goldstone boson of a spontaneously broken symmetry, in analogy to pions in QCD. I will discuss gauge/gravity dual descriptions of explicit realizations of composite Higgs models using insights from non-conformal examples of the AdS/CFT correspondence. I will explain how to calculate particle masses and decay constants for proposed Sp(4) and SU(4) gauge theories. The results obtained compare favourably to lattice gauge theory studies and go beyond those due to a greater flexibility in choosing the fermion content. That content changes the running of the couplings and its choice can lead to sizable changes in the bound state masses. The `top partners’ present in composite Higgs are modelled by dual fermionic fields in the bulk. Including suitable higher dimension operators can ensure a top mass consistent with the Standard Model.

After a review of Batalin-Vilkovisky formalism and homotopy algebras, we discuss how these structures emerge in quantum field theory and gravity. We focus then on the application of these sophisticated mathematical tools to scattering amplitudes (both tree- and loop-level) and to the understanding of the dualities between gauge theories and gravity, highlighting generalizations of old results and presenting new ones. Password: 009633

The aim of this talk is to display some enumerative results that are directly applied in quantum field theory. We shall see how the number of connected chord diagrams can be used to count one-particle-irreducible (1PI) diagrams in Yukawa theory. This translation of Feynman diagrams simplified the process of calculating the asymptotic behaviour of the corresponding Green functions.

In this talk I will show how Generalised geometry provides a general framework to study consistent truncations of M-theory and string theory with different amount of supersymmetry, based on the notion of generalised G-structure. The generalised G-structure contains all the information about the truncated theory: field content. supersymmetry and gaugings. I will discuss in details the cases of half-maximal and one-quarter supersymmetric reduction and illustrate the general construction with a few examples.

In this talk, we outline the computational details and present the results for NNLO mixed EWxQCD corrections to on-shell production of Z boson at the LHC. We use the method of differential equation to obtain all the master integrals analytically, appearing in virtual and real-emission contributions. These results increase the accuracy of the predictions and contribute to reduce the theoretical uncertainties.

Superstring/M-theory compactified on compact Ricci flat manifolds have recently been conjectured to exhibit instabilities whenever the metrics do not have special holonomy. We use worldsheet conformal field theory to investigate instabilities of Type II superstring theories on compact, Ricci flat, spin 3-manifolds including a worldsheet description of their spin structures. The instabilities are signaled by the appearance of stringy tachyons at small radius and a negative (1-loop) vacuum energy density at large radius. We briefly discuss the extension to higher dimensions. Password: 009633

The analogue of Kontsevich's matrix Airy function, with the cubic potential Tr(Phi^3) replaced by a quartic term Tr(Phi^4), provides a toy model for quantum field theory. We indicate how all its Dyson-Schwinger equations can be solved exactly and explicitly. Thereby we encounter meromorphic differential forms conjectured to obey blobbed topological recursion.

I will review the status of the early and late universe from both a theoretical and observational point of view. In particular, LIGO has detected several gravitational wave signals from black holes with masses around 30 times the mass of the sun. Whereas, direct and indirect dark matter detection experiments have so far failed to detect any sign of dark matter particles. In this talk, we will explore whether the primordial formation of black holes - with properties like those detected by LIGO - could be part or all of the cosmological dark matter. It turns out the prediction of such black holes could be intimately connected to addressing the puzzle of a quantum theory of gravity and the end of cosmological inflation. That is, string theory may predict exactly such a dark matter candidate.

In this talk I will describe a model of (double) kinetic theory which paves the way to describe matter in a Double Field Theory background (2003.09588). In this approach, generalized diffeomorphisms acting on double phase space tensors are defined and the generalized covariant derivative is replaced by a generalized Liouville operator. The section condition is consistently extended and the closure of the generalized transformations is still given by the C-bracket. In this context I will introduce a generalized Boltzmann equation and compute the moments of the latter, obtaining an expression for the generalized energy-momentum tensor and its conservation law.

Using the Gelfand-Kapranov-Zelevinsk system for the primitive cohomology of an infinite series of complete intersection Calabi-Yau manifolds, whose dimension is the loop order minus one, we completely clarify the analytic structure of all banana amplitudes with arbitrary masses. In particular, we find that the leading logarithmic structure in the high energy regime, which corresponds to the point of maximal unipotent monodromy, is determined by a novel Γˆ-class evaluation in the ambient spaces of the mirror, while the imaginary part of the amplitude in this regime is determined by the Γˆ-class of the mirror Calabi-Yau manifold itself. We provide simple closed all loop formulas for the former as well as for the Frobenius κ-constants, which determine the behaviour of the amplitudes, when the momentum square equals the sum of the masses squared, in terms of zeta values. We extend our previous work from three to four loops by providing for the latter case a complete set of (inhomogenous) Picard-Fuchs differential equations for arbitrary masses. This allows to evaluate the amplitude as well as other master integrals with raised powers of the propagators in very short time to very high numerical precision for all values of the physical parameters. Using a recent p-adic analysis of the periods we determine the value of the maximal cut equal mass four-loop amplitude at the attractor points in terms of periods of modular weight two and four Hecke eigenforms and the quasiperiods of their meromorphic cousins.

A twisted Hopf algebra is a Hopf algebra in the category of linear species. The Fock functors allow to recover 'classical' Hopf algebras from twisted ones. Numerous constructions and results can be lifted to the level of twisted bialgebras, such that cofreeness, shuffle and quasi-shuffles products, etc. Using two tensor products in the category of species, we define the notion of cointeraction of twisted bialgebras. Examples on finite topologies and graphs allow to reconstruct Ehrahrt polynomials and chromatic polynomials in a canonical way from cointeraction of twisted bialgebras.

I will review how to incorporate alpha'-corrections in Double Field Theory, and show how these ideas can be applied to explore the higher derivative corrections to generalized T-dualities.

The anomalous magnetic moment of the muon serves as a low-energy precision test of the Standard Model of particle physics. The White Paper (arXiv:2006.04822) recently published in Physics Reports concludes that a tension of 3.7 standard deviations persists between the direct measurement and the Standard Model prediction of the anomalous magnetic moment of the muon. A new direct measurement is expected very soon by the E989 experiment at Fermilab. On the theory side, the uncertainty of the SM prediction is quasi-saturated by the hadronic contributions. I will focus on the effort by the lattice QCD community to compute these hadronic contributions and compare these calculations to phenomenological determinations.

I will describe the classical interaction between βγ-systems and sigma models displaying the underlying 2d sigma model geometry and the interpretation of the βγ-systems as arising from a quotient with respect to a null Kac-Moody isometry. The presentation will cover purely bosonic, (1,1), (1,2), (2,1) and (2,2) supersymmetric systems.

In this lecture, I would like to review recent progresses of holography for conformal field theories on manifolds with boundaries, which is called as AdS/BCFT. After we introduce the AdS/BCFT construction, we would like to introduce the holographic entanglement entropy and entanglement wedges in AdS/BCFT, which provided one of the important ideas behind the recent Island formula. Finally, we would like to explain our recent work about codimension two holography, called wedge holography as an application of AdS/BCFT.

Ever since the invention of General Relativity, Riemannian geometry has been privileged to be the mathematical paradigm for modern physics, which enables us to address the very basic notion of `spacetime'. By now, Double Field Theory has evolved to achieve its own autonomy statute as an alternative gravitational theory to GR. Postulating the O(D,D) symmetry as the fundamental principle, GR and the Einstein Field Equations are unambiguosly augmented. Further, it turns out that DFT encompasses not only the Riemannian geometry but also non-Riemannian ones where the notion of Riemannian metric ceases to exist. In this talk, after reviewing the above aspects of DFT, I will talk about my latest paper with Shigeki Sugimoto (arXiv:2008.03084), where we examined some quantum consistency of the non-Riemannian geometries as string theory novel backgrounds. The critical dimensions turn out to be the same as in the Riemannian cases (i.e. D=26 or 10). The BRST string spectrum differs, but still agrees with DFT or the Einstein Double Field Equations.

Cosmological surveys are believed to measure the future value of quantum correlators in a theory of gravity around quasi de Sitter spacetime. The goal of this talk is to develop a cosmological bootstrap, namely understand how general physical principles such as unitarity, locality and symmetries are encoded in these observables without a reference to the unobservable time evolution that generates them. I'll show that in single-clock inflation, the only correlators of curvature perturbations that are fully de Sitter isometric are those of the free theory. This provides a strong motivation to develop a 'Boostless' Bootstrap that does not assume invariance under de Sitter boosts (generally broken during inflation). I'll show how all tree-level bispectra for a massless scalar and graviton follow from a set of simple boundary Bootstrap Rules. To move beyond the bispectrum, I'll derive a Cosmological Optical Theorem, which expresses the consequences of unitary time evolution in the bulk for the boundary spatial correlations dictated by the wavefunction of the universe. This provides a very powerful relation between higher- and lower-order diagrams. As an example, I'll show who to compute the (exchange) trispectrum from a given bispectrum.

Particle physics processes are usually modeled with a chain of complex simulators. While these allow us to generate high-quality simulated data, they face a challenging inverse problem when we want to infer theory parameters from observed data because the relevant likelihood function cannot be evaluated. I will explain this problem, review what the field has traditionally done to circumvent it, and show how we can use machine learning methods together with matrix-element information to solve it efficiently. Finally I will discuss how the same methods can be useful in many other scientific fields from neuroscience to strong gravitational lensing.

A supernova natively emits neutrinos and antineutrinos of all flavors with different luminosities and energy spectra. I will show how the different neutrino flavors are brought closer to each other due to irreversible decoherence-like processes occurring at a Tera-Hz rate, determined by the large neutrino density. This new result allows detailed implementation of flavor-dependent neutrino transport in supernova simulations and paves the way for supernova neutrino phenomenology. From a more conceptual perspective, this concrete example will show how collective behaviour can be parametrically faster than that of its constituents, and how 'coarse-graining' leads to irreversible 'relaxation' even though the microscopic dynamics remains perfectly time-reversal invariant. This talk will be based on https://arxiv.org/abs/2009.03337

In the homotopy algebra formulation of field theory, the algebraic operation of "homotopy transfer" is a generalised Wilsonian effective field theory construction. I will outline how homotopy transfer applies to the construction of double field theory beyond cubic order (without the "strong constraint"), and discuss the relation to a proposal by A. Sen. I will also discuss certain apparently hitherto unknown subtleties of strings on tori which arise along the way, relating to (non)commutativity, sign factors, and the zero-mode sector.

Calculation of virtual scattering amplitudes involves dealing with several problems. The presence of numerical instabilities, as well as singularities, prevents straightforwardly obtaining precise results. And most of these problems are due to the particular structure of the integrand-level expressions. By using the Loop-Tree Duality (LTD) formalism, and exploring the novel nested residue strategy, we recently managed to obtain causal representations of multi-loop amplitudes and classify diagrams according to their topological complexity. We did some numerical simulations, and verified the stability of the calculations. Besides that, in this talk we will focus on the potential consequences of these discoveries.

We revisit the question whether the worldsheet theory of a closed string admits a global O(d,d,R) symmetry. We consider the truncation of the target space theory in which fields are independent of d coordinates, which is O(d,d,R) invariant. The worldsheet theory is not O(d,d,R) invariant, unless it is truncated by setting winding and center-of-mass momenta to zero. We prove consistency of this truncation and give a manifestly O(d,d,R) invariant action, generalizing a formulation due to Tseytlin by including all external and internal target space fields. It is shown that, due to chiral bosons, this symmetry is anomalous. The anomaly is cancelled by a Green-Schwarz mechanism that utilizes the external B-field.

I will present a generalization of the conventional Kerr-Schild (KS) formalism, a powerful tool for constructing exact solutions in general relativity, to the double field theory (DFT), exceptional field theory (ExFT) and supergravities. First, a universal structure of the KS ansatz for the generalized metric for DFT and ExFT will be introduced. I’ll show that their equations motion reduce to linear partial differential equations. Based on this formalism, I’ll discuss the exact double copy map, which represents solutions of the supergravity equations in terms of solutions of the Maxwell equation.

This talk describes an attempt to amend a scheme originally proposed by M. Gell-Mann to identify the spin-1/2 fermions of N=8 supergravity with the quarks and leptons of the Standard Model. This proposal relies in an essential way on embedding the SU(8) R symmetry into the infinite-dimensional `maximal compact' subgroup K(E10) of the conjectured duality symmetry E10. I will also mention more recentwork exploring the possible role and significance of the eight massive gravitinos in astrophysics.

Motivated by their potential to stabilise moduli, we inspect type II backgrounds with gaugino condensates on D-branes. We use the language of generalized complex geometry which is the most adapted to account for their back-reaction. After reviewing the effective 4d physics revealed by Kachru, Kallosh, Linde and Trivedi, as well as the basic concepts of generalized complex geometry, I will show in this talk how the gaugino condensates modify the action and the supersymmetry conditions, concentrating on compactifications to four dimensions, and discuss some of its salient features. We will show how the equations reproduce the phenomenon of moduli stabilisation, and comment on a local solution that matches the on-shell value obtained from the four-dimensional effective action.

S- and (abelian) T-duality play a central role in string theory, but their scope is limited to highly constrained spacetimes. Generalised T-dualities, which include non-abelian and Poisson-Lie T-duality, apply to a significantly larger class of target spaces with a wide range of applications. Classically they are on an equal footing with abelian T-duality, but their quantum corrections are much more mysterious and mostly unexplored. I will review the main problems which have to be solved to make progress in this direction. Afterwards, I demonstrate how recently explored connections between generalised T-dualities, double field theory, and consistent truncations allow to prove that two-loop RG flows are preserved under these dualities. We will discuss the implications of this result and emphasise how the intriguing mathematical structures that govern all the current applications influence quantum corrections in a highly non-trivial way.

We revisit a correspondence between toroidal compactifications of M-theory and del Pezzo surfaces, in which rational curves on the del Pezzo are related to 1/2-BPS branes of the corresponding compactification. We argue that curves of higher genus correspond to non-geometric backgrounds of the M-theory compactifications, which are related to exotic branes. In particular, the number of “special directions” of the exotic brane is equal to the genus of the corresponding curve. In addition to predicting three new non-geometric backgrounds, we discuss a relation between addition of curves in the del Pezzo and the brane polarization effect.

According to the theory of cosmic inflation, the large scale structures observed in our Universe (galaxies, clusters of galaxies, Cosmic Background Microwave - CMB - anisotropy...) are of quantum mechanical origin. They are nothing but vacuum fluctuations, stretched to cosmological scales by the cosmic expansion and amplified by gravitational instability. At the end of inflation, these perturbations are placed in a two-mode squeezed state with the strongest squeezing ever produced in Nature (much larger than anything that can be made in the laboratory on Earth). This article studies whether astrophysical observations could unambiguously reveal this quantum origin by borrowing ideas from quantum information theory. It is argued that some of the tools needed to carry out this task have been discussed long ago by J. Bell in a, so far, largely unrecognized contribution. A detailed study of his paper and of the criticisms that have been put forward against his work is presented. Although J. Bell could not have realized it when he wrote his letter since the quantum state of cosmological perturbations was not yet fully characterized at that time, it is also shown that Cosmology and cosmic inflation represent the most interesting frameworks to apply the concepts he investigated. This confirms that cosmic inflation is not only a successful paradigm to understand the early Universe. It is also the only situation in Physics where one crucially needs General Relativity and Quantum Mechanics to derive the predictions of a theory and, where, at the same time, we have high-accuracy data to test these predictions, making inflation a playground of utmost importance to discuss foundational issues in Quantum Mechanics. Link: https://mpi-aei.zoom.us/j/97623339163

I will discuss recent work with Ruben Minasian and Yi Zhang on six-dimensional exotic supermultiplets. The main focus of the talk will be on the relationship between these multiplets and exceptional symmetries. In particular I will discuss the non-existence of a standard spacetime "section" for these theories and how the exotic graviton appears in the SL(3,R) Ehlers symmetry term in algebraic decompositions to three dimensions. I will also present an overview of arguments suggesting that the dynamics of these theories may not reduce to those of supergravity in five dimensions and sketch a proposed construction which connects them to three-dimensional supergravity.

In this work we study the Tomita-Takesaki construction for a family of excited states that, in a strongly coupled CFT - at large N -, correspond to coherent states in an asymptotically AdS spacetime geometry. We compute the modular flow and modular Hamiltonian associated to these excited states in the Rindler wedge and for a ball shaped entangling surface. Using holography, one can compute the bulk modular flow and construct the Tomita-Takesaki theory for these cases. We also discuss generalizations of the entanglement regions in the bulk and how to estimate the modular Hamiltonian in a large N approximation. Finally we present a holographic formula, based on the BDHM prescription, to compute the modular evolution of operators in the corresponding CFT algebra. Zoom Link: https://mpi-aei.zoom.us/j/92597759251

Neutrinos are key particles in a wide range of astrophysical sources. Neutrinos affect the stellar dynamics, drive the formation of new elements, and carry information about the physics of the most energetic events in our Universe. Recent developments on the role of neutrinos in compact astrophysical sources and their detection perspectives will be reviewed. https://mpi-aei.zoom.us/j/91244673319

Kaluza-Klein spectra on string/M-theory solutions depend significantly on whether the solution can be obtained from uplift of a maximal gauged supergravity. For some solutions of M-theory, mIIA and IIB obtained from uplift, I will present the spectrum of KK gravitons and discuss a persistent form of universality when solutions with same (super)symmetry and supergravity spectrum are present in different theories. The masses thus found can be obtained from an SL(8)-covariant mass matrix whose trace provides the universal coefficients. In the second part of the talk, I will discuss the spectrum of KK gravitons around the N=2 AdS_4 solution that is dual to the IR of a cubic deformation of ABJM. This solution cannot be obtained from uplift of an N=8 D=4theory, and this seems to be linked to the fact that its metric cannot be isometrically embedded in R^8. Further, the allocation of modes with different spins in N=2 supermultiplets cannot be made KK level by KK level, but needs space invaders.

Exotic supergravities are six-dimensional theories with chiral maximal (4,0) and (3,1) supersymmetry, which instead of a graviton feature exotic gauge fields with non-standard Young tableaux representations, subject to selfduality constraints. After reduction to 5D they all share the field content of standard maximal supergravity. While so far these theories are only known in the free limit, their interacting versions were conjectured by C. Hull to exist and to describe strong coupling limits of N=8 theories in 5D. I present novel actions in a 5+1 split of coordinates whose field equations reproduce those of the free bosonic (4,0) and (3,1) theory, respectively, including the selfduality relations. I discuss evidence for a master exceptional field theory formulation with an extended section constraint that, depending on the solution, produces the (4,0), (3,1) or the conventional (2,2) theory.

Higher differential geometry is a generalization of differential geometry, where ordinary geometric structures are replaced by their L∞-versions (such as L∞groups and L∞algebras). This formalism let the concept of principal bundle be generalized to the one of "bundle gerbe". This geometric object can be equipped with a connection, whose parallel transport is defined on surfaces instead of on paths. This will be exactly the global formalization of the Kalb-Ramond field. We can then say that bundle gerbes are for strings what principal bundles are for gauge particles. Double Field Theory is often referred to as a generalization of Kaluza-Klein Theory that unifies a metric and a Kalb-Ramond field, instead of a gauge field. Can this statement be made geometrically precise? In this talk I will give a simple introduction to higher differential geometry, then I will explore the idea that DFT can be naturally globalized in this geometric formalism. Finally I will apply this construction to obtain some examples of T-duality.

In this talk I will review results obtained by our group over the last few years concerning the calculation of alpha' corrections of 4- and 5-dimensional stringy black-hole geometries and the computation of their Wald entropies, always in the context of the Heterotic Superstring effective action. First, I will describe the corrections to that action in the Bergshoeff-de Roo formalism and how we can compute the corresponding corrections to the simplest 5- and 4-dimensional (3- and 4-charge) stringy black holes. Then, I will comment on the problems surrounding the application of the Iyer-Wald prescription to the calculation of the Wald entropy of those black holes directly in terms of their 10-dimensional oxidized counterparts and I will argue that the calculation has to be done using the 4- and 5-dimensional actions. I will then show how to obtain these actions by direct dimensional reduction and how they provide us with alpha'-corrected T-duality rules. I will derive duality invariant Wald entropy formulas using the Iyer-Wald prescription and I will show that the entropies obtained satisfy the expected properties. Finally, I will comment on the many unresolved problems related to all these issues. See sites.google.com/view/egseminars for details on how to join the meeting"

The AdS3/CFT2 correspondence provides the best arena to test the holographic paradigm. This is simultaneously due to the relative tractability of 2d CFTs and the world sheet theory on AdS$_3$ backgrounds. Despite this, when compared to their higher dimensional counterparts, little effort has been made to construct AdS$_3$ string vacua. I will discuss an ongoing program to fill this gap. There exists a rich variety of superconformal algebras in 2d, with distinct options even for a fixed number of supercharges. This makes the problem of classifying holographic duals to CFTs realising these both interesting and broad. I will discuss how one may systematically realise the various algebras in supergravity, and make use of G-structure techniques to find new classes of solutions in 10 and 11 dimensions. Particular emphasis will be given to a class of solutions in massive IIA preserving small N=(4,0) supersymmetry, for which there is a concrete proposal for dual CFTs.

Exceptional field theory (ExFT) provides a framework where T and U-duality can be made manifest. In this talk, I will discuss how supersymmetry can also be made manifest in a superspace ExFT. In this approach, the fermionic coordinates are unified with the external spacetime coordinates, which together are acted on by external superdiffeomorphisms. The internal space and its section condition remain purely bosonic. This corresponds to the simplest way one might construct an exceptional superspace, but even this proves surprising: it cannot be done directly with the original supersymmetric formulations of ExFT, and one must instead relax or reformulate certain features (such as the vielbein postulates). I will sketch how this works for the case of E_7. The superspace Bianchi identities then lead to the explicit form of the on-shell p-form curvatures as well as their duality relations. Various applications will also be discussed.

Generalised geometry has proven to be a central framework to understand T- and U-duality. In particular it provides a critical language to understand two-dimensional deformations of non-linear sigma-models on group manifolds and coset spaces which admit Poisson-Lie symmetry. This latter can be seen as a relaxation of the notion of isometry allowing one to perform a generalised notion of T-duality. In this talk I will discuss joint work with F. Hassler, G. Piccinini, D. Thompson, where we studied integrable deformations of CPn background. Notwithstanding the à priori complexity of these deformations, we show how the deformed CPn background is an example of a bi-Hermitian or generalised Kähler geometry. In addition we explain how the generalised Kähler potential can be constructed for the deformed CPn geometry and provide explicit forms for n=1,2.

With the growing need for multi-loop multi-scale scattering amplitudes several approaches have been developed which aim at a more automated numerical computation of them. An example is the multi-loop numerical unitarity method with which we have computed the planar two-loop five-parton amplitudes in QCD, as well as the two-loop four-graviton amplitudes in Einstein gravity. In this talk we review those results and introduce the Caravel framework, a C++ library implementing algorithms required for numerical unitarity which we will make publicly available.

L-infinity algebras are a generalization of Lie algebras involving,besides a 2-bracket, a potentially infinite number of higher-order brackets which satisfy generalized Jacobi identities. In particular, the usual Jacobi identity for the 2-bracket is violated by terms involving a 3-bracket. Originally discovered in physics in the context of closed string field theory, it has since been understood that an L-infinity algebra can in fact be associated to any classical field theory; the Jacobi identities then encode gauge-invariance of the equations of motion, Noether identities and all that, in a way similar to the BRST-BV field-antifield formalism. In this talk, I will first review the definition of L-infinity algebras, in two complementary ways: 1) the original formulation involving an infinite number of brackets, which can be neatly packaged in a nilpotent coderivation, and 2) the dual picture, where L-infinity relations are encoded in a nilpotent derivation. (For field theories, this derivation is nothing but the BRST-BV differential.) Then, I will explain the mathematical notion of homotopy transfer: how, under certain conditions, the L-infinity structure can descend to a subspace of the original vector space. In the field theory context, this corresponds to the notion of (tree-level) integrating out of degrees of freedom, with the smaller L-infinity algebra encoding the algebraic structure of the effective theory. This is based on work in progress with Alex S. Arvanitakis, Chris Hull and Olaf Hohm. See sites.google.com/view/egseminars for details on how to join the meeting

In this talk, I will discuss the analytical calculation of cusp and collinear anomalous dimensions in four-loop QCD. Our approach is based on a direct calculation of four-loop quark and gluon form factors. I will explain how finite field and novel syzygy techniques facilitated the reduction of the relevant Feynman integrals to a basis of finite integrals, which could then be evaluated directly from their standard parametric representation.

I will explain how to use the quantum Ryu-Takayanagi formula to compute entanglement entropies in pure JT gravity, including all of the perturbative graviton corrections. I will also explain why it is not possible to factorize the gravity Hilbert space in a local way. The tension between defining a local and isometric factorization map motivates the insertion of a 'defect operator' into the standard definition of the Renyi entropy. The defect operator has a clear interpretation in the Euclidean replica calculation of the entropy. The contribution of the defect operator to the entanglement entropy matches the area term in the quantum Ryu-Takayanagi formula. Zoom Link: https://mpi-aei.zoom.us/j/95580327312 .

It has long been believed that progress in understanding the black hole information paradox would require coming to terms with microscopic details of quantum gravity - something beyond the reach of semiclassical effective field theory. In that light, one of the most surprising discoveries of the last year has been that signature features of the unitary evaporation of black holes can already be seen within effective field theory, albeit with the inclusion of 'euclidean wormholes'. However, these novel contributions are best understood when the gravitational theory is not a single microscopic theory, but an average over many different theories. To save unitarity must we then simultaneously throw it away? I will explain how the same story can be recovered within a single microscopic theory by thinking carefully about the right effective theory for finite-lifetime observers. Link: https://mpi-aei.zoom.us/j/97623339163

Hoffman‘s exponential is an isomorphism from the shuffle Hopf algebra to the quasi-shuffle Hopf algebra. In this talk we study it in the context of renormalisation of rough paths, which requires its arborification (in Ecalle’s sense) to the Connes-Kreimer Hopf algebra of rooted trees. This is joint work with Ch. Curry (NTNU) and Y. Bruned (Univ. Edinburgh).

The stringent bounds on the electric dipole moment (EDM) of the electron provide a powerful test of new physics. They can probe new dynamics at the TeV scale, even when contributions to the electron EDM arise at the two-loop level. I will discuss how to use the effective-field-theory (EFT) approach to classify these corrections, presenting the contributions to the anomalous dimension of the CP-violating dipole operator of the electron up to the two-loop level. Selection rules based on helicity and CP symmetry play an important role in simplifying the analysis. I will also show that the latest ACME bound pushes natural theories significantly more into fine-tune territory, unless they have a way to accidentally preserve CP.

Unlike transient gravitational signals generated by collisions of black holes and neutron stars, continuous waves allow repeated observations. But there is a catch - they are orders of magnitude weaker. The required sensitivity can be reached by integrating months of data, at the cost of an exponential increase in analysis complexity. This challenge has been met with Loosely Coherent algorithms. In this talk we will present an overview of the field, introduce Loosely Coherent approach and share exciting results from the Loosely Coherent all-sky search for neutron stars and other sources. Zoom Link: https://mpi-aei.zoom.us/j/6282782272

We first review the property of asymptotic freedom in various field theories and spacetime dimensions together with its connection to and consequence for fixed points. Several examples are discussed in order to introduce the study of a particular six dimensional scalar theory. Endowed with a bi-adjoint symmetry, this theory has the curious and unusual property that while being asymptotically free this is due to the sign of the two loop term of the beta-function. The consequences of this property are explored as well as an extension to a theory with a 4-adjoint symmetry that provides the clue as to why the bi-adjoint theory has this peculiar property.

We will review the two renormalisations used in regularity structures for singular SPDEs. The first one recenters distributions around a point such that they can be understood as recentered monomials. The second one cures divergences coming from ill-defined distributional products in a singular SPDE. We will consider them for the fractional phi^3_d models and explain how they can be interpreted via a Bogoliubov type recursion.

Heavy-ion collisions at RHIC and LHC produce quark-gluon plasma (QGP) whose bulk evolution is well described by relativistic hydrodynamics. However, to further explore the properties of QGP and the phase diagram of QCD, one typically has to go beyond this hydrodynamic paradigm. In this talk, I will present the development of a general dynamic framework which couples slow non-hydro. modes with hydro. modes, namely Hydro+. I will demonstrate the application of Hydro+ to describe off-equilibrium dynamics near the conjectured QCD critical point. If time permits, I will briefly report my recent attempt to explore the dynamic properties of QGP in the non-hydrodynamic yet non-perturbative regime. Link: https://mpi-aei.zoom.us/j/93714224687

We will discuss some aspects of scaling in quantum quench and its realization in holography. We then consider quantum quench in the singlet sector of the c=1 Matrix Model and map out the emergent dual space-time. As expected the late time space-time does not contain black holes. Rather, they generically have space-like regions of large coupling analogous to cosmological singularities. Link: https://mpi-aei.zoom.us/j/97623339163

In quantum information theory, relative von Neumann entropy gives a quantitative meaning for the distinguishability of states by measurements. In this talk, I will introduce a variant of relative entropy which is compatible with the existence of conserved charges. I will show how to compute this symmetry resolved relative entropy in quantum field theory and further present some analytic results for the free fermion CFT. Zoom link: https://mpi-aei.zoom.us/j/95399770035

The B_+ operatos of Connes and Kreimer are an essential tool in QFT. We give a theoretical, categorial version for regarding these operators as they appear in monoidal categories, especially Feynman categorie. We will then consider combinatorial examples, that in a simplicial context yield back the original B_+ operator in terms of trees and in a more complex example a fibration for permutahedra that is essential for E_2 operads, cohomology operations and Deligne's conjecture.

With Run II, the LHC experiment already reached an unprecedented level of precision compared to previous hadron colliders. The amount of data collected in Run III and the High-Luminosity run will increase quickly and dramatically. I will discuss specific challenges to theorists that must be overcome to provide predictions that have the precision necessary to match the accuracy of data. A few novel ideas to exploit this precision directly or indirectly will also be discussed.

I will first describe how we develop a systematic formalism to compute correlation functions of massless scalar fields in de Sitter space. Time permitting, I will then show how, using a combination of numerical techniques as well as techniques from differential geometry, we are shedding light on how inflation starts out of inhomogenous initial conditions. Link: https://mpi-aei.zoom.us/j/97623339163

The quantum complexity of a unitary or state is defined as the size of the shortest quantum computation that implements the unitary or prepares the state. The notion has far-reaching implications spanning computer science, quantum many-body physics, and high energy theory. Complexity growth in time is a phenomenon expected to occur in holographic theories and strongly-interacting many-body systems more generally, but explicitly computing the complexity of a given state or unitary is notoriously difficult. By considering an ensemble of systems, and establishing a rigorous relation between complexity and unitary designs, we will prove statements about complexity growth in various models. Specifically, we prove a linear growth of complexity in random quantum circuits, using a recent result about their design growth. Zoom link: https://mpi-aei.zoom.us/j/99064635917

The Hamilton-Jacobi action is a useful tool in Classical Mechanics. I will recall its construction, and a generalization due to Weinstein that works when constraints are present. I will then show how in certain examples, the generalized Hamilton-Jacobi action, without further quantum corrections, appears as the effective action of a topological quantum field theory on a cylinder. This has two interesting interpretations: First, the Hamilton-Jacobi action provides, in some sense, a 'holographic dual' to the original theory. Secondly, it can be interpreted as the kernel of a generalized Segal-Bargmann transform. This talk is based on ongoing joint work with P. Mnëv and A. Cattaneo.

I will discuss some basic features of non-relativistic gravity of which Newton-Cartan gravity, the frame-independent reformulation of Newtonian gravity, is the most prominent example. In particular, I will identify the non-relativistic geometry underlying non-relativistic string theory as a candidate theory of non-relativistic quantum gravity. Moreover, I will discuss some basic properties of non-relativistic string theory in a curved background such as it's quantum consistency, T-duality, the basic branes of non-relativistic string theory and their supersymmetric properties.

The rapid progress in analytic evaluation techniques for Feynman integrals in the recent years has been substantially driven by novel insights into the underlying mathematical structures. I will show how some of these structures can be used to accelerate numerical Feynman integral calculations. As a concrete example, I will introduce a new Monte-Carlo integration algorithm of Feynman parametric integrals whose run-time only scales polynomially in the number of edges of the underlying graph. This algorithm makes excessive use of Hepp's bound on Feynman integrals in its new tropical geometric formulation.

In this talk, I'll discuss a variety of applications in AdS/CFT that make use of CFTs living on spacetimes with boundaries. The applications include the construction of black hole microstates whose behind-the-horizon geometries can be understood explicitly, constructing models of evaporating black holes in which the Page curve can be understood through explicit CFT calculations, providing a microscopic descriptions of certain Randall-Sundrum scenarios, and providing a framework for holography where the CFT is replaced by a large number of non-interacting bits. Link: https://mpi-aei.zoom.us/j/92645118489?pwd=Y3ZSRTA0a1BEYk9pMkRydWhlTGZ0UT09z . This meeting is password-protected. The password will be sent out with the reminder on Wednesday.

On popular demand I will review my understanding of mathematical modelings for the present COVID-19 pandemic. I will review the so called S(E)IR type compartments models describing the dynamics of a pandemic disease. These are rather trivial models which are yet successful in describing reality, as it seems. Crucial is the determination of underlying parameters - including the famous R0. I will review some recent papers I read on the subject and point to interesting websites running simulations. This is not meant to be a highly scientific talk.

Wilson Lines are fundamental, non-local observables in any gauge theory. Recent efforts have been successful in constructing defect theories, whose fundamental fields are operators inserted on these lines. In models with an AdS/CFT dual, the strong coupling description of these operator insertions are small deformations of the minimal surface solution in the appropriate string background. I will present the perturbative calculation of four-point correlators in the defect CFT defined on the 1/2-BPS Wilson line of ABJM theory (arXiv:2004.07849). I will cover the Witten diagram calculation, obtaining the correlation functions of the deformations of the minimal surface. Using symmetry considerations, I will argue the matching of fields/operators as well as their natural organisation in superspace, which relates the family of correlators to a single function of the 1D invariant cross ratio. Subsequently, I will show that this result can be found in an independant manner by selecting the minimal bootstrapped solution. Finally, I will present the CFT data that can be extracted from this.

In recent years, the "tensor networks" used to describe condensed matter systems have been discovered to share many qualitative features in common with holographic theories of quantum gravity. Studying these features in tensor networks has helped us build intuition for how the corresponding features should work in quantum gravity; most importantly, tensor networks helped us develop a tractable framework for understanding holographic quantum error correction. A little over a year ago (1812.01171), my collaborators and I proved that every geometric state in a holographic theory of quantum gravity can be represented as a tensor network, explaining the success of the "toy model." I will explain this proof, comment on its implications, and discuss recent work from other authors on the tensor network/holography correspondence. The aim of the talk will be to communicate the lessons from tensor networks that should inform our general approach to quantum gravity research; it should be intelligible to an audience with little to no tensor-network experience.

The treatment of γ 5 in dimensional regularization has been an issue ever since the original ‘t Hooft-Veltman paper. By dropping cyclicity of traces involving γ 5, one can treat the d-dimensional γ5 as in four dimensions, at the cost of rendering certain Feynman integrals ambiguous. This ambiguity has been made manifest in the β4αS calculations of Bednyakov & Pikelner and Zoller, where the strong coupling, top Yukawa coupling and Higgs self-coupling have been taken into account, hence the ambiguity now has phenomenological consequences. In this talk, I will demonstrate how Weyl Consistency Conditions fix this particular ambiguity for a completely general theory, in a way that generalizes to higher orders. As an added bonus, given the 3-loop gauge β-function for a simple gauge group, I will indicate how the same method easily extends this result to the general case, including kinetic mixing.

The nascent field of gravitational wave (GW) science will be an interdisciplinary subject — enriching different branches of physics — yet the associated computational challenges are enormous. Faithful theoretical templates are a compulsory ingredient for data analysis and reliable physical interpretation of the signals. Yet, while current templates for compact binary sources may be sufficient for detection and crude parameter estimation, they are still too coarse for precision physics with GW data. We then find ourselves in a situation in which, for key processes within empirical reach, theoretical uncertainties may dominate. To move forward, and profit the most from GW observations, more accurate waveforms will be needed. This will be critical, as I will discuss, to study the equation of state of neutron stars and the nature of black holes; as well as potentially successful searches for exotic compact objects and putative ultra-light (dark matter) particles in the Universe. The ‘effective field theory approach’ to the binary inspiral problem in general relativity — which my collaborators and I have developed — has been instrumental for the construction of the state-of-the-art GW template bank. I will review how these and other novel techniques borrowed from particle physics have transformed the study of the two-body problem in gravity, providing key new results and paving the road forward to a new era of foundational investigations in physics through GW precision data.

In the last four years certain deformations of the famous N=4 SYM named strongly-twisted N=4 SYM have gained a reputation as being particularly simple. I will discuss the spectral problem - the problem of diagonalising the Dilatation operator - in the context of these theories. After showing how to find the Dilatation operator at one-loop level I proceed to find its eigenvalues in three steps. In a first step I present an observation that many states have zero anomalous dimensions and we only find non-trivial eigenvalues in subsectors of the whole theory. In the second step I find the eigenvalues in the simplest non-trivial sector and in a third step I find the eigenvalues in the largest non-trivial sector. Several peculiar features of the theories and their effect on the two-point functions are also discussed.

In this talk, I will discuss a framework to compute two-loop amplitudes that combines integrand reduction, integration-by-part identities, numerical evaluation over finite fields and analytic reconstruction techniques. Applications to the computation of planar two-loop five-parton and w+4 parton amplitudes in QCD will also be presented.

I will give a review of the status of Standard Model effective field theory (SMEFT) in the EW sector. The talk will showcasing some results from latest global fits, the state of the art in Monte Carlo tools and discuss some recent sensitivity studies from new processes at the LHC and beyond. The latter will focus first on the high energy behaviour of scattering amplitudes involving top quarks/ EW bosons and their embedding into collider processes as a new avenue for improving our understanding of the interactions of the electroweak symmetry breaking sector. Finally I will present a study of the ttbb final state as a probe of new four-fermion interactions between third generation fermions exploiting some multi-dimensional machine learning classifiers to optimise sensitivity.

In the talk, the energy-momentum (also "stress-energy") tensor will be presented as crucial current density for the gravitational field. With its property of being conserved it necessarily generates a massless spin-2 gauge field which, by considering gauge and coordinate transformations becomes part of the spacetime metric. Beyond, the energy-momentum tensor is delivering deep insight into gravitation in thermodynamics, particularly interrelations between heat current, viscosity, temperature, entropy and entropy production under themselves and with respect to gravity will be discussed.

This seminar talk is intended as an interactive session about machine learning (ML) techniques and their use cases for particle physics. No prior knowledge about machine learning is required. Depending on the feedback of the audience, we may briefly go through some basic building blocks of more advanced ML models. The benefit of ML for the particle physics community will be illustrated with several examples including cross section regression, learning an exclusion boundary, event generation and anomaly detection. With my presentation I want to stimulate discussions about issues and doubts as well as potentials and ideals regarding the incorporation of ML methods into the physics workflow and am happy to discuss whatever use-case you have been dreaming of.

I will review how Lie superalgebras can be used to describe the bosonic sector of supergravity theories. In particular, tensor hierarchy algebras have been introduced as a novel algebraic structure underlying the embedding tensor formulation of gauged supergravity. Recently, they have also turned out to play a crucial role in extended geometry, which is a universal framework unifying (and generalising) the internal sectors of double and exceptional field theory. In extended geometry, ordinary diffeomorphisms are unified with internal gauge transformations. The corresponding generalised Lie derivatives do not form a Lie algebra but a generalisation thereof, an L-infinity-algebra, which can be derived from the tensor hierarchy algebra.

QED radiative corrections to hadronic observables are generally rather small but they become phenomenologically relevant when the target precision is at the percent level. This is the case of leptonic and semileptonic decays of light and heavy pseudoscalar mesons. On the one hand, QED radiative corrections to hadronic observables can be calculated with the required non-perturbative accuracy by using lattice techniques. On the other hand, the inclusion of electromagnetic interactions in a lattice calculation is a challenging problem because QED is a long-range unconfined interaction and numerical simulations necessarily require a finite volume. The problem is particularly delicate in the case of QED radiative corrections to decay rates because of the appearance of infrared divergences (proportional to the logarithm of the lattice volume) at intermediate stages of the calculations. In this talk I will briefly review the recent theoretical advances that opened the way to realistic non-perturbative simulations of QCD+QED, discuss a method that allows to calculate QED radiative corrections to hadronic decay rates and present the results of a non-perturbative calculation of the leptonic decay rates P-> l nu (gamma) in the case of light (P=pi,K) and charmed (P=D,Ds) pseudoscalar mesons.

In this talk, we describe a novel framework to obtain higher-order corrections to physical observables in perturbative QFT. This method, called Four-Dimensional Unsubtraction (FDU), is based on the Loop-Tree Duality (LTD) theorem, which provides an alternative decomposition of virtual amplitudes. The strategy is valid to all loop orders, even if multiple powers of the propagators are present. Through the introduction of fully local counter-terms, we manage to cancel the UV singular behavior. Moreover, the whole framework is intended to perform an integrand level combination of the real and virtual contributions, using properly defined universal kinematical mappings, to achieve a complete point-by-point cancellation of IR divergences. The final result can be directly integrated in four space-time dimensions, applying standard numerical techniques. Some examples for NLO corrections and two-loop amplitudes will be discussed.

Proposed future electron-positron colliders would allow precise determinations of the mass of the top quark and the W boson from measuring the rise of the cross section near the pair-production threshold. At hadron colliders, the threshold region is not directly accessible but enhanced by rising parton luminosities. Near threshold, radiative corrections due to soft and Coulomb photons or gluons are enhanced and can be resummed to all orders in perturbation theory. The cross section is also sensitive to the finite decay width of the produced particles. I will discuss an effective-field theory framework to address these effects and present recent results for top-quark pair production at the LHC and W-pair production at future lepton colliders.

After the discovery of the Top quark, high energy physics community took 17 years to find the Higgs boson in 2012. Since then, all Standard Model predicted fundamental particles are confirmed in experiments. In the next 15 years, the Large Hadron Collider (LHC) will focus on precision measurements of the Higgs boson properties. The precise theory predictions as well as the measurements of Higgs boson transverse momentum distributions, decay width and trilinear couplings will be crucial for searching beyond Standard Model singles, determining the stability of our universe and inspiring the next generation colliders. In this seminar, I will first summarise the state-of-the-art theory precisions of each Higgs boson production channels at the LHC. Then I will analyse the challenges and opportunities for precision Higgs phenomenology in the next 15 years till the end of High-Luminosity-LHC period.

Novel lattice results reveal a tension between the measured direct CP violation in K→εε decays and the standard model theory prediction, with the theoretical uncertainty dominating. This inconsistency could have several sources, one of which could be the missing contribution of new particles in the theory predictions. However, a reliable standard model prediction is needed to disentangle possible new physics effects from the standard model background. As rapid progress on the lattice is bringing non-perturbative long-distance effects under control, a more precise knowledge of short-distance contributions is essential. We describe the first NNLO calculation for this observable and discuss future prospects, as well as issues of scheme dependence and the separation of perturbative and non-perturbative effects.

The status of string theory will be examined, and what is known and what is unknown about the theory will be discussed. String theory has special duality symmetries that do not occur in conventional field theories, and some of the implications of these will be explored, and the implications for the nature of space-time will be investigated.

When solving functional equations, we tend to look first for an explicit representation of the solution, i.e., for an expression built from the indepen- dent variable and some constants by means of various basic operations. In this talk we will consider the problem of finding explicit solutions of homogeneous linear recurrence equations with polynomial coefficients (LRE). Algorithms are known for finding polynomial solutions, rational solu- tions, hypergeometric solutions (whose consecutive-term ratio is rational), d’Alembertian solutions (representable as nested indefinite sums of hypergeometric sequences) and Liouvillian solutions (representable as interlacings of d’Alembertian sequences) of LRE. Alas, usually no such solutions exist (save for the zero solution). So it is natural to think of wider classes of explicitly representable sequences, properly including Liouvillian sequences. Such classes can be obtained by allowing basic operations under which the class of Liouvillian sequences is not closed. One important operation of this kind is convolution of sequences which corresponds to the product of their generating functions. A convolution has the form of a definite sum, so the question arises: How to find solutions of LRE represented as (nested) definite sums of simpler sequences? #We will make a very small first step towards answering this seemingly difficult question.

One of the corner stones of future lepton colliders are high precision measurements of the top quark mass and width. In the first part of this talk, I present a new method for top quark mass determination at lepton colliders using radiative events, which can determine the top quark mass with an accuracy of 110 MeV. It relies on the inclusive top quark pair production cross section, which is known to high accuracy at the production threshold (NNLL and NNNLO) and at higher center-of-mass energies in the continuum (NNNLO QCD). For our study on radiative events, we have constructed a matched cross section, which I present in the second part of this talk. It is valid in all regions from the threshold to the continuum and combines NNLL threshold with NNNLO continuum contributions.

Weak capture transfer occurs when a particle becomes captured into orbit about one of the primary mass points of the three or four-body problem, temporarily. Capture in this case is defined when the Kepler two-body energy of a particle with respect to the primary is negative. This was first numerically demonstrated by Belbruno (EB) in 1986. This capture occurs in a region about the primary called a weak stability boundary (WSB). It was proven by EB (2005) that the WSB contains within it a hyperbolic invariant set, giving rise to chaotic motion. Although crudely numerically estimated in 1986, numerical work by Gomez (2007) gave deeper insights into its makeup yielding surprising results as to its complexity. Further insights in the makeup of this region were made in a series of studies (Gidea,Topputo, EB). The relationship of weak capture to permanent capture and the work of Sitnikov in the 1960s is discussed. Weak capture transfer has important applications. One such transfer was used in 1991 by EB and Miller to rescue an errand Japanese lunar probe and successfully send it to the Moon. This same transfer class was used in 2011 for NASA’s lunar Grail mission and another type was used by ESAs lunar SMART 1 mission in 2004. One such transfer is currently being used in a mission to Mercury for ESA’s BepiColombo mission. A new result that is described is the existence of a weak capture transfer to Mars. This promises to have interesting applications. A lunar gateway is also discussed based on recent work. If there is time, an exciting new application of weak capture to quantum mechanics is discussed.

Gravitational wave observations provide a new and unique window into the early universe. I will start by explaining why this is the case, and give an overview of new physics scenarios that give rise to a stochastic gravitational wave background in the early universe, and therefore may be testable by future gravitational wave observations. Then I will focus on the audible axion scenario, a class of axion models whose cosmological evolution leaves an observable imprint in the gravitational wave background. This allows a new and unique probe of very high scale axions, with symmetry breaking scales close to the GUT or string scale.

The Swampland program aims to distinguish effective field theories that can be consistently completed into quantum gravity in the ultraviolet from those which cannot. It has lead to a number of proposals, or conjectures, regarding the required properties of effective theories. I will review some of the evidence for these and propose that they arise due to a particular aspect of duality where propagating fields in the infrared are emergent from the collective properties of infinite towers of states. Time permitting, I will discuss some applications of the conjectures, in particular to accelerating cosmologies and to massive spin-2 fields.

Dyson-Schwinger equations are the quantum analogues of the equations of motion and so are physically very important and useful. In their diagrammatic form they also show some nice discrete mathematical structures. For example, diagrammatically they generate certain classes of Feynman diagrams and so act like combinatorial specifications, and they are compatible with algebraic structures on Feynman diagrams, like renormalization Hopf algebras. In this colloquium I will overview the physics and the math of this and close with a different combinatorial expansion that can go beyond naive Feynman diagrammatics and solve some Dyson-Schwinger equations using an unusual expansion indexed by rooted connected chord diagrams.

Compact binaries composed of neutron stars and black holes are the most important source of grav-itational waves. The first observations of gravita-tional waves from binary black holes in 2015 was a landmark discovery for astrophysics and funda-mental physics. The detection of these waves and the extraction of the source’s parameters relies on accurate predictions for the gravitational waves. A combination of numerical and approximate analytical methods is needed for this. In this talk, I discuss how the binary dynamics and the emit-ted gravitational waves can be calculated within the post-Newtonian (weak-field and slow-motion) approximation. This can be formulated conveni-ently within an effective field-theory framework. The calculation can be performed by methods also used in particle physics (Feynman integrals) and be automated using computer algebra.

In the planar limit of a large number of colors, N=4 super Yang-Mills theory is integrable, and remarkable advances have been made in determining operator anomalous dimensions and more to all loop orders. In this talk I'll describe recent progress in constructing scattering amplitudes in this theory to high loop order. Planar N=4 amplitudes are dual to light-like polygonal Wilson-loops, and are only nontrivial for six or more gluons. The spaces of functions to which the amplitudes belong are so restrictive that only a few constraints are needed to simply write down the answer, through seven loops in the six-gluon case and four loops in the seven-gluon case. The results are multi-variate functions of the kinematics, which can be analyzed in various limits in order to study how high loop order amplitudes factorize. One can also extrapolate from weak to strong coupling, and compare with the AdS/CFT dual description available there.

This talk is about integrability of planar N=4 super Yang-Mills theory. I will review the notion of integrability in the AdS/CFT context and what it means for planar scattering and Wilson loops including selected results. I will then present a concrete notion of the corresponding Yangian symmetry in this model, show that it holds true, and discuss the (perturbative) implications for correlation functions and Wilson loops.