Quantum field theory meets gravity

24 Sept 2019, 12:45 → 27 Sept 2019, 13:00 Europe/Berlin

Main Auditorium (DESY Hamburg)

The annual DESY Theory Workshop is organized by the elementary particle physics community in Germany. The focus is on a topical subject in theoretical particle physics and related fields. This year workshop will have a focus on particle phenomenology. More details can be found on the conference homepage .

The workshop features:

• Four half-day plenary sessions of specialized talks by invited speakers.
• Two half-days of parallel sessions, allowing young researchers to present their work (on Wednesday and Thursday afternoons).
• The DESY Heinrich-Hertz-Lecture on Physics for public outreach

Tuesday 24 September

Registration

Welcome

1 Welcome

Speaker: Joachim Mnich

Video https://webcast.desy.de/?recID=1043

Plenary Session

Convener: Jan Plefka (HU-Berlin)

2 Quantum Gravity and the Swampland

Speaker: Gary Shiu (U. W. Madison)

Slides DESY_2019.pdf

Video https://webcast.desy.de/?recID=1045

3 Towards Classical de Sitter Solutions

Speaker: Clay Cordova (IAS)

Slides dsShort.pdf

Video https://webcast.desy.de/?recID=1044

4 Microscopic origin of the Bekenstein-Hawking entropy of supersymmetric AdS5 black holes

Speaker: Dario Martelli (King's College London)

Slides DESY_talk_2019.pdf

Video https://webcast.desy.de/?recID=1046

15:45 Coffee break

Plenary Sessions

Convener: Astrid Eichhorn (U. Heidelberg)

5 On tensor field theories

I will present a brief introduction to tensor field theories and their large N limit. I will in particular focus on the renormalization group fixed points and the conformal field theories describing them in a particular model.

Speaker: Razvan Gurau (CPHT)

Slides Desy2019.pdf

Video https://webcast.desy.de/?recID=1047

6 Asymtotic safety

Speaker: Daniel Litim (Sussex)

Slides 2019_Desy.pdf

Video https://webcast.desy.de/?recID=1048

17:30 Welcome reception

Wednesday 25 September

Plenary Session

Convener: Elli Pomoni (DESY)

7 From scattering amplitudes to gravitational waves

Speaker: Zvi Bern (UCLA)

Slides Hamburg_2019.pdf

Video https://webcast.desy.de/?recID=1048

8 Complexity, quantum fields and geometry

Speaker: Michal P. Heller (AEI MPG)

Slides michal_heller-DESY-TH-2019_v3.pdf

Video https://webcast.desy.de/?recID=1050

9 Tensor networks as a numerical tool for FQT

Speaker: Mari Carmen Banuls (MPQ MPQ)

Slides TNandQFT_DESY_Sept19.pdf

Video https://webcast.desy.de/?recID=1052

10:30 Coffee break

Plenary Session

Convener: Thomas Thiemann

10 Bootstrap Methods for Quantum Gravity

Speaker: Alexander Zhiboedov (CERN)

Slides Hamburg_2019_zhiboedov.pdf

Video https://webcast.desy.de/?recID=1051

11 Black holes in N=4 Super-Yang-Mills

Speaker: Francesco Benini (SISSA)

Slides AdS5_BHentropy_1909_DESY(short).pdf

Video https://webcast.desy.de/?recID=1053

12 Towards a unitary and renormalizable quantum theory of gravity

Speaker: Christian Steinwachs (Uni. Freiburg)

Slides 190925_DESY_Hamburg_Steinwachs.pdf

Video https://webcast.desy.de/?recID=1054

12:30 Lunch

Parallel Session: Cosmology & Astroparticle Physics

13 Searches for right-handed neutrinos at accelerators

Extensions to the SM featuring a low-scale seesaw can be used to to explain the observation of neutrino oscillations, baryogenesis and dark matter. I present the potential to search for right-handed neutrinos using current experiments. I compare the reach of the main detectors at the LHC when a displaced vertex signature in proton collisions is used. Additionally, I show the potential to improve on that using heavy ion collisions. Finally, I present the reach of the fixed target experiment NA62.

Speaker: Dr Jan Hajer (UCLouvain)

Slides Searches_for_right-handed_neutrinos_at_accelerators

14 Neutrino Portal Dark Matter via Freeze-In

We investigate a model of neutrino portal dark matter where a right-handed neutrino both generates the observed neutrino masses and mediates between the SM and a dark sector, consisting of a fermion and a boson. We explore the parametrics and different constraints on the neutrino portal to dark matter. In contrast to earlier work, we focus on regions of the parameter space where DM is generated via freeze-in instead of freeze-out.

Speaker: Mr Mathias Becker (TU Dortmund)

Slides Hamburg.pdf

15 Common origin of baryon asymmetry, dark matter and neutrino mass

In this work, we explain three beyond standard model (BSM) phenomena, namely neutrino masses, the baryon asymmetry of the Universe and Dark Matter, within a single model and in each explanation the right handed (RH) neutrinos play the prime role. Indeed by just introducing two RH neutrinos we can generate the neutrino masses by the Type-I seesaw mechanism. The baryon asymmetry of the Universe can arise from thermal leptogenesis from the decay of lightest RH neutrino before the decoupling of the electroweak sphaleron transitions, which redistribute the $ B-L $ number into a baryon number. At the same time, the decay of the RH neutrino can produce the Dark Matter (DM) as an asymmetric Dark Matter component. The source of CP violation in the two sectors is exactly the same, related to the complex couplings of the neutrinos. By determining the comoving number density for different values of the CP violation in the DM sector, we obtain a particular value of the DM mass after satisfying the relic density bound. We also give prediction for the DM direct detection (DD) in the near future by different ongoing DD experiments.

Speaker: Mr Sarif Khan (Goettingen University)

Slides desy-talk.pdf

16 All-in-one Relaxion

We present a unified relaxion solution to the five major outstanding issues in particle physics: the hierarchy problem, dark matter, matter-antimatter asymmetry, neutrino masses and the strong CP problem. The only additional field content in our construction with respect to standard relaxion models is an up-type vector-like fermion pair and three right-handed neutrinos charged under the relaxion shift symmetry.

Speaker: Sandeepan Gupta (Durham)

17 Relativistic and spectator effects in leptogenesis with heavy sterile neutrinos

For leptogenesis with heavy sterile neutrinos above the Casus-Ibarra bound, asymmetries produced by relativistic sterile neutrinos at early times can be relevant in the case of weak washout or if the asymmetry is partly protected from washout by being transferred to partially equilibrated spectator fields. We thus study the relevance of relativistic effects for leptogenesis in a minimal seesaw model with two strongly hierarchical sterile neutrinos. Starting from first principles, we derive a set of relativistic momentum averaged boltzman equations to compute the final B-L asymmetry at order one accuracy for various initial conditions. Assuming fully equilibrated spectator fields, we find that relativistic corrections lead to a sign flip and an enhancement of the final asymmetry for weak washouts and a vanishing initial abundance of sterile neutrinos. As an example for the effect of partially equilibrated spectators, we consider b-Yukawa and weak sphaleron interactions for sterile neutrinos with masses 5 * 10^12 GeV. For strong washouts and a vanishing initial abundance of sterile neutrinos, this can give another sign flip and an absolute enhancement of the final asymmetry by up to two orders of magnitude relative to the cases with either negligible or fully equilibrated spectator interactions.

Speaker: Mr Philipp Klose (Université Catholique de Louvain)

Slides klose_desy_workshop_2019.pdf

18 CP violating effects in coherent elastic neutrino-nucleus scattering processes

Assuming light vector mediators, we discuss the effects of CP violation on the coherent elastic neutrino-nucleus scattering (CEvNS) process in the COHERENT sodium-iodine, liquid argon and germanium detectors. We show that in some regions of the parameter space, the presence of a dip in the event rate spectrum can be used to constraint CP violating effects. In other regions, we find that CP violating parameters can mimic the Standard Model CEvNS spectra induced by real parameters. We point out that the interpretation of CEvNS data in terms of a light vector mediator should take into account possible CP violating effects.

Speaker: Valentina De Romeri (IFIC (CSIC-Univ. Valencia))

Slides De_Romeri.pdf

19 Constraints on effective dark matter-nucleon interactions from 3-year IceCube observations of the Sun

Dark matter particles from the galactic halo can be captured by the sun and can then annihilate into Standard Model particles which makes the sun a source of GeV neutrinos. One goal of the IceCube Neutrino Observatory (IceCube) is to detect these neutrinos. In this work, we present the constraints on the DM-nucleon interactions which we obtain from 3-year IceCube observations of the Sun.

Speaker: Ms Anja Brenner (Technische Universität München)

Slides Anja_Brenner_DESY_2019.pdf

20 The Effective Field Theory of Large Scale Structureat Three Loops

We study the power spectrum of dark matter density fluctuations in the framework of the Effective Field Theory of Large Scale Structures (EFTofLSS) up to three loop orders. In principle, several counter-terms may be needed to handle the short-distance sensitivity in perturbation theory. However, we show that a small number of extra coefficients are sufficient to match numerical simulations with percent accuracy when a generic renormalization prescription is implemented (allowing for running of the individual counter-terms). We show that the level of accuracy increases with respect to the two loop results, up to $k \simeq 0.4\, h$~Mpc$^{-1}$ at redshift $z=0$, although the overall improvement is somewhat marginal. At the same time, we argue there is evidence that the behavior of the loop expansion in the EFTofLSS is typical of an asymptotic series, already on the brink of its maximum predictive power (at $z=0$). Hence, the inclusion of higher orders will likely deteriorate the matching to data, even at moderate values of $k$. Part of the reason for this behavior is due to large contributions to the (renormalized) power spectrum at three loop order from mildly non-linear scales, even after the UV counter-terms are included. In conclusion, the EFTofLSS to three loop orders provides the best approximation to the (deterministic part of the) power spectrum in the weakly non-linear~regime at $z=0$, and higher loops are not expected to improve our level of accuracy.

Speaker: Mr Henrique Rubira (DESY)

Slides RUBIRA_DESY_2019_09_25.pdf

Parallel Session: Particle Phenomenology

Convener: Ayan Paul

21 Quantum gravity and the Standard Model

Much progress has been made in recent years towards a field-theoretic understanding of quantum gravity within the asymptotic safety conjecture. In this talk, I report progress towards the inclusion of Standard Model matter. We perform an extensive fixed point search in theories involving Ricci scalar and tensor, and Riemann tensor invariants alongside SM matter, up to high polynomial orders in curvature. In this large space of curvature invariants, we identify stable UV fixed points and UV-IR connecting trajectories. We emphasize the role of Ricci and Riemann tensor interactions, the impact of SM matter fields, and highlight differences with fixed points in purely gravitational settings. Implications for quantum gravity model building are discussed.

Speaker: Gustavo Medina Vazquez (University of Sussex)

Slides qg_sm_talk.pdf

22 Asymptotically Safe Extensions of the MSSM

Despite its many successes the Standard Model can at best be viewed as a low energy approximation to a more fundamental theory of nature. Supersymmetry provides a theoretically attractive extension of the Standard Model while the idea of asymptotic safety leads to field theories which can be regarded as being fundamental. In this talk I investigate whether and how the minimal supersymmetric version of the Standard model can be extended in a way such that it becomes asymptotically safe without including gravity. Implications for the field content and on the scale of susy breaking are discussed.

Speaker: Mr Kevin Moch (TU Dortmund)

Slides DESY2019_KevinMoch.pdf

23 Asymptotic safety and phenomenology in extensions of the Standard Model

I will discuss asymptotically safe extensions of the Standard Model with new matter fields at the TeV scale. The BSM sector contains singlet scalars and vector-like fermions in representations which permit Yukawa interactions with the Standard Model leptons and a Higgs portal coupling. UV safety is explored up to the Planck regime in dependence of the BSM couplings. Moreover, phenomenological implications are investigated including production and decay mechanisms, charged lepton flavour violation, electric dipole moments, Drell-Yan processes and lepton anomalous magnetic moments. Scenarios are highlighted which avoid Landau poles, stabilise the Higgs sector and accommodate for the muon and electron anomalous magnetic moments.

Speaker: Mr Tom Steudtner (U Sussex)

Slides presentation_steudtner.pdf

24 Machine learning in particle physics - overview

Speaker: Gregor Kasieczka

Slides DeepLearning_DESY_Theory_Autumn2019.pdf

25 Leptogenesis in the model with modular symmetry

We discuss the model with the modular $A_4$ invariance. It has been shown that this model can explain neutrino masses and mixing angles observed by oscillation experiments. We investigate the leptogenesis in this model. It is found that the leptogenesis by decay of right-handed neutrinos works well. Especially, we show that the Dirac and Majorana CP-phases in the PMNS matrix and right-handed neutrino masses are predicted in a restricted region in order to explain the baryon asymmetry of the universe.

Speaker: Mr Takahiro Yoshida (Niigata University)

Slides yoshida_desy20190925.pdf

Parallel Session: String & Mathematical Physics

26 Three-dimensional bosonization duality from Higher Spin Gravity

Three-dimensional bosonization duality is one of the remarkable dualities discovered recently in three-dimensional conformal field theories. At least in the large-N limit the duality is tightly linked to higher spin symmetries and, therefore, to Higher Spin Gravities that are AdS/CFT dual to these CFT's. We propose a new approach to solve conformal field theories and apply it to the three-dimensional bosonization duality. All three-point correlation functions of single-trace operators are obtained in the large-N as a simple application. The idea is to construct, as an effective theory, a nonlinear realization of the conformal algebra in terms of physical, gauge-invariant, operators. The efficiency of the method is also in the use of an analog of the light-cone gauge and of the momentum-space on the CFT side. The uniqueness of the nonlinear realization manifests the three-dimensional bosonization duality at this order. We also find two more non-unitary solutions which should be analogous to the recently discovered fishnet theories. The gravitational dual description of these non-unitary CFT's is explicitly constructed - chiral Higher Spin Gravities. The latter theories are UV complete and give the first example of quantum consistent Higher Spin Gravities.

Speaker: Dr Evgeny Skvortsov (AEI, Potsdam)

Slides 2019_DESY_Skvortsov.pdf

27 G2 manifolds and String Dualities

I will review recent progress in the role of G2 manifolds in various string dualities. This includes the dualities between heterotic strings, type IIA and M-Theory, as well as mirror symmetries for type II strings.

Speaker: Dr Andreas Braun (University of Oxford)

Slides Andreas_Braun_g2.pdf

28 Hidden exceptional symmetry in the pure spinor superstring

In the pure spinor formulation of the superstring, in addition to the spacetime bosons and fermions the string worldsheet theory includes a ghost sector described by pure spinor fields. I will discuss the existence of a hidden action of an affine E6 Lie algebra on this sector, which arises from enhancement of SO(10) spacetime rotations together with a U(1) ghost symmetry, and whose representations encode the ghost spectrum.

Speaker: Dr Guglielmo Lockhart (University of Amsterdam)

Slides DESY_Talk_Lockhart.pdf

29 Walls of Marginal Stability and the Swampland Distance Conjecture

In this talk we will investigate the Swampland Distance Conjecture in type IIB string theory compactified on K3 x T2. As conjectured one indeed finds a tower of exponentially light states using the Hodge-Deligne splitting of the middle homology in the degeneration limit. This tower, however, consists of quarter-BPS states, which can potentially decay into a pair of half-BPS states at walls of marginal stability. We investigate the presence of these walls in the context of the degenerations.

Speaker: Dr Markus Dierigl (Utrecht University)

Slides DESY_Theory_Workshop_Dierigl.pdf

30 Modularity from Monodromy

We discuss the relation between certain auto-equivalences of the category of B-branes on elliptic Calabi-Yau threefolds and modular properties of the corresponding topological string partition function. This suggests a geometric explanation and generalization of recent conjectures on the appearance of lattice Jacobi forms. In particular, we will shed light on the special case where the fibration does not have a section but only multi-sections.

Speaker: Dr Thorsten Schimannek (University of Vienna)

Slides schimannek.pdf

31 Seiberg-like dualities for gauge theories with a boundary

We analyse certain 2d supersymmetric gauge theories (GLSMs) with a boundary which in the IR flow to SCFTs that are relevant for string compactifications with D-branes. Certain non-abelian GLSMs exhibit Seiberg-like dualities which relate seemingly different UV gauge theories with the same IR physics. We extend the analysis of such dualities to theories with boundaries and propose the action of the duality on the boundary degrees of freedom. We further support our proposal by performing non-trivial checks using a mathematical formulation of D-branes.

Speaker: Ms Urmi Ninad (Doctoral student)

Slides Desy_Theory_19.pdf

16:00 Coffee break

Parallel Session: Cosmology & Astroparticle Physics

32 Can high-scale axion models have a viable cosmological history?

High-scale axion models are sensitive to CMB isocurvature bounds, which are thought to rule out scenarios with an axion decay constant fA above 10^14 GeV. This would be incompatible with grand unification scenarios featuring an axion with fA related to the unification scale, which could otherwise be primary targets for future experiments like CASPER and ABRACADABRA. In view of the above, we re-examine the cosmological history of axion perturbations during inflation and reheating in high-scale axion models in which the axion is mostly aligned with the phase of the field which drives inflation.

Speaker: Dr Carlos Tamarit (Technische Universität München)

Slides GUT_axion.pdf

33 Large radiative effects on dark matter annihilation resummed

A particularly promising prediction of several wimp DM models is the quasi-monochromatic emission of gamma rays due to their pair-annihilation in e.g. the innermost part of the Milky Way. High energy gamma-ray fluxes due to such annihilation processes are naively suppressed by the inverse-squared dependence on the heavy DM mass and by the fact that the cross section is loop-suppressed. However, non-perturbative effects (Sommerfeld) can play the opposite role of enhancing the signal by several orders of magnitude. Relatedly, the different scale hierarchies present in the problem pose an additional technical difficulty. Namely, the appearance of large (Sudakov) logarithms that -on top of the Sommerfeld effect- break the validity of the perturbative expansion. In order to resum these, we employ soft-collinear effective-field-theory (SCET) methods. By means of process-specific factorization theorems, we are able to make very precise (Next-to-Leading Log prime) predictions for the relevant annihilation cross sections. Focusing, for concreteness, on the pure-wino model I will give in this talk a short overview of these methods and their application to indirect DM detection with gamma-ray telescopes.

Speaker: Dr Martin Vollmann (TUM)

Slides vollmanndesythworkshop2019.pdf

34 Wino potential and Sommerfeld effect at NLO

For heavy electroweak dark matter, the resummation of large quantum corrections due to long-range potentials (the "Sommerfeld effect") is crucial in determining the precise annihilation cross-section. In this talk, I will consider the one-loop correction to the potential which provides the leading non-relativistic correction to the Sommerfeld effect in the case of wino or wino-like dark matter particles $\chi_0$. I will discuss the impact of this correction on the $\chi_0 \chi_0$ annihilation cross-section relevant for indirect detection and the resulting shifts on the zero-energy S-wave resonances.

Speaker: Kai Urban (TUM)

Slides desy2019urban.pdf

35 Rapid bound-state formation of Dark Matter via inelastic Standard Model particle scattering

The thermal decoupling description of multi-TeV scale dark matter (and co-annihilating partners) is reconsidered. In several works it has been pointed out that the inclusion of quantum mechanical effects in the computation of the thermal relic abundance is in certain cases required in order to make a precise determination of the upper bound on the DM mass. One of these quantum mechanical effects is the existence of meta-stable bound-state solutions in the two-particle spectrum of the WIMPs, caused by attractive (SM) force-carriers. The formation of these bound states and their subsequent decay into SM particles gives a significant effect in the relic density computation on top of the Sommerfeld enhancement, typically allowing for heavier DM masses. So far, only the single mediator emission (W, Z, H, g, photon or exotic) was considered as the formation process of the bound states. In this talk, I show that bound-state formation via inelastic bath particle scattering, i.e. the mediator instead in the t-channel and connected to the SM plasma particles, can be the dominant conversion process. For a vector mediator we find that bound-state formation via bath particle scattering at the freeze-out temperature exceeds the single mediator bound-state formation cross-section by several orders of magnitude. More generally, bound-state formation via inelastic bath particle scattering has obviously no kinematical block if the mediator is massive (e.g. W, Z, H), whereas the single mediator emission is highly suppressed for temperature smaller than the mediator mass. The implications of these findings are that bound-state effects become more pronounced and consequently dark matter could be even more heavier than expected.

Speaker: Mr Tobias Binder (Kavli IPMU)

Slides talk_DESY_tbinder.pdf

36 Conversion driven freeze-out

Chemical equilibrium is a commonly made assumption in the freeze-out calculation of coannihilating dark matter. We explore the possible failure of this assumption and find a new conversion-driven freeze-out mechanism. Considering a representative simplified model inspired by supersymmetry with a neutralino- and sbottom-like particle we find regions in parameter space with very small couplings accommodating the measured relic density. In this region freeze-out takes place out of chemical equilibrium and dark matter self-annihilation is thoroughly inefficient. The relic density is governed primarily by the size of the conversion terms in the Boltzmann equations. Due to the small dark matter coupling the parameter region is immune to direct detection but predicts an interesting signature of disappearing tracks or displaced vertices at the LHC. Unlike freeze-in or superWIMP scenarios, conversion-driven freeze-out is not sensitive to the initial conditions at the end of reheating.

Speaker: Dr Stefan Vogl (Max-Planck-Institut für Kernphysik)

Slides conversion_driven.pdf

37 Accurate relativistic treatment of cosmological Evolution of real scalar DM

We ilustrate an accurate numerical Analysis of the scenario of real scalar dark matter with negligible coupling with the SM states. Assuming that the DM is produced during inflation and can reach at least kinetic Equilibrium due to its self-coupling, we illustrate a fully relativistic analysis of dark matter evolution, thermalization conditions and different freeze– out regimes, including the chemical potential effects.

Speaker: Dr Giorgio Arcadi (University of Rome 3)

Slides arcadi_desy2019.pdf

38 BBN constraints on MeV-scale dark sectors

Meta-stable dark sector particles decaying into electrons or photons may non-trivially change the Hubble rate, lead to entropy injection into the thermal bath of Standard Model particles and may also photodisintegrate light nuclei formed in the early universe. We study generic constraints from Big Bang Nucleosynthesis on such a setup, with a particular emphasis on MeV-scale particles which are neither fully relativistic nor non-relativistic during all times relevant for Big Bang Nucleosynthesis. These constraints turn out to be very relevant for a number of well-studied models, e.g. in the context of self-interacting dark matter with light mediators. We then further apply our calculations to the case of MeV-scale dark matter annihilating into electromagnetic radiation. We show that, for p-wave suppressed annihilations, these constraints turn out to be significantly stronger than the ones from CMB observations, and are even competitive with the strongest bounds from other indirect searches.

Speaker: Mr Marco Hufnagel (DESY Hamburg)

Slides Marco_Hufnagel_DTW_2019.pdf

39 Neutron Star Mergers Chirp About Vacuum Energy

Speaker: Cem Eroncel

Parallel Session: Particle Phenomenology

Convener: Goutam Das

40 Precision calculation for the LHC

The large quantity of data expected from the Large Hadron Collider (LHC) will allow detailed investigations of the Higgs boson, as well as searches for Beyond the Standard Model (BSM) physics through small deviations in Standard Model (SM) signatures. In order to take full advantage of this dataset, it is essential to confront the measurements with high precision theoretical predictions. These require complicated calculations in the quantum field theories that comprise the SM. I will review the current status and future prospects of these computations, focusing on next-to-next-to-leading order (and higher) calculations in perturbative QCD.

Speaker: Raoul Roentsch (CERN)

Slides roentsch_DESY.pdf

41 High precision Higgs Phenomenology at the LHC

Fiducial differential cross sections are reliable observables at the LHC. Precision measurements are providing unprecedented data which reveals the detailed structure of the Standard Model. From the theory point of view, event generators could simulate the underlying scattering processes and apply the same experimental selection criterions to reduce systematical errors when comparing with data. I will introduce some of the implementations and simulations in NNLOJET package with the-state-of-the-art theory precisions at NNLO QCD and above then illustrate their applications when comparing with LHC measurements of the Higgs boson.

Speaker: Dr Xuan Chen (University of Zurich)

Slides DESY2019XuanChen.pdf

42 Generalized Wilson lines and next-to-soft emissions

Recently, several groups have investigated the possibility to extend the traditional soft gluon factorization and resummation framework at subleading power. In particular, for processes with colourless final state particles, resummation has been achieved at the leading-log accuracy. In this talk, after introducing the general set up, I focus on a particular ingredient for such factorization known as generalized Wilson line, that takes into account next-to-soft emissions at all orders.

Speaker: Domenico Bonocore (Universität Münster)

Slides Bonocore_DESY.pdf

43 New physics searches at the LHC: the SMEFT approach

I will give a brief introduction to the Standard Model Effective Field Theory (SMEFT) and discuss how its parameters can be constrained with global analyses of LHC data, allowing to extract information on physics beyond the SM with a minimum bias. As a case study, I will present the preliminary results of a fit to top quark measurements and illustrate some interesting features of this analysis.

Speaker: Ilaria Brivio (Univ. Heidelberg)

Slides slides_DESY_thWorkshop.pdf

44 Flavour Constraints on MFV SMEFT

The one-loop matching between the Standard Model Effective Field Theory (SMEFT) and FCNC operators of the Weak Effective Theory enables the incorporation of high-precision flavour data in Electroweak global fits of SMEFT at high energies. We explore the flavour bounds on the linear combination of the SMEFT Wilson coefficients given by the one-loop matching with a Minimal Flavour Violation assumption.

Speaker: Rafael Aoude (Mainz)

Slides Aoude_DESY2019.pdf

Parallel Session: String & Mathematical Physics

45 Magnetic Quivers, Higgs Branches, and 6d N=(1,0) Theories

The physics of M5 branes placed near an M9 plane on an A-type ALE singularity exhibits a variety of phenomena that introduce additional massless degrees of freedom. There are tensionless strings whenever two M5 branes coincide or whenever an M5 brane approaches the M9 plane. These systems do not admit a low-energy Lagrangian description so new techniques are desirable to shed light on the physics of these phenomena. The 6-dimensional N=(1,0) world-volume theory on the M5 branes is composed of massless vector, tensor, and hyper multiplets, and has two branches of the vacuum moduli space where either the scalar fields in the tensor or hyper multiplets receive vacuum expectation values. Focusing on the Higgs branch of the low-energy theory, previous works suggest the conjecture that a new Higgs branch arises whenever a BPS-string becomes tensionless. Consequently, a single theory admits a multitude of Higgs branches depending on the types of tensionless strings in the spectrum. The two main phenomena discrete gauging and small E8 instanton transition can be treated in a concise and effective manner by means of Coulomb branches of 3-dimensional N=4 gauge theories. After a brief reminder of the set-up, a formalism is introduced that allows to derive a novel object from a brane configuration, called the magnetic quiver. Focusing one the two main phenomena, I will demonstrate the derivation of the magnetic quiver for 6d N=(1,0) theories from multiple M5 branes transverse to an A-type singularity. Thereafter, equipped with the necessary derivation rules, I will discuss magnetic quivers for M5 branes near an M9 plane. The main features of this formalism are as follows: (i) the 3d Coulomb branch of the magnetic quiver yields the Higgs branch of the 6d system, (ii) all discrete gauging and E8 instanton transitions have an explicit brane realisation, and (iii) exceptional symmetries arise directly from brane configurations. The formalism facilitates the description of Higgs branches at finite and infinite gauge coupling as spaces of dressed monopole operators.

Speaker: Dr Marcus Sperling (Yau Mathematical Sciences Center, Tsinghua University)

Slides Talk_Sperling.pdf

46 Localization of N=1 Theories on D2 x T2

We consider 4d N=1 gauge theories with R-symmetry on a hemisphere times a torus. We apply localization techniques to evaluate the exact partition function through a cohomological reformulation of the supersymmetry transformations. Our results represent the natural elliptic lifts of the lower dimensional analogs as well as a field theoretic derivation of the conjectured 4d holomorphic blocks, from which partition functions of compact spaces with diverse topology can be recovered through gluing. We also analyze the different boundary conditions which can naturally be imposed on the chiral multiplets, which turn out to be either Dirichlet or Robin-like. We show that different boundary conditions are related to each other by coupling the bulk to 3d N=1 degrees of freedom on the boundary three-torus, for which we derive explicit 1-loop determinants. The talk is based on arXiv 1906.02051 .

Speaker: Dr Antonio Pittelli (Uppsala University)

Slides 2019_talk_DESY.pdf

47 The Λ-BMS4 group of dS4 and new boundary conditions for AdS4

In this talk, I will discuss the solution space of general relativity in Bondi gauge, with non-vanishing cosmological constant. Using the dictionary between Bondi and Fefferman-Graham gauges, the analogues of the Bondi news, Bondi mass and Bondi angular momentum aspects at the boundary of generic asymptotically locally dS4 spacetimes will be identified. Then, I will introduce the Λ-BMS4 group as the residual symmetry group of Bondi gauge after boundary gauge fixing. This group consists in infinite dimensional non-abelian supertranslations and superrotations and it reduces in the asymptotically flat limit to the extended BMS4 group. Furthermore, I will present new boundary conditions for asymptotically locally AdS4 spacetimes which admit R times the group of area-preserving diffeomorphisms as the asymptotic symmetry group.

Speaker: Mr Romain Ruzziconi (ULB and International Solvay Institutes)

Slides Lambda-BMS-v3.pdf

48 BPS and non-BPS supergravity solutions through bi-spinors

Spinor bilinears have played an important role in classification of supergravity vacuum solutions. In this talk I will present a novel reformulation of supersymmetry conditions for type II theories in terms of spinor bilinears without assuming any factorization of space-time. These bispinors can be used to define brane calibrations, namely differential forms whose integrals measure minimal energies, and I will show how supersymmetry can be rephrased in terms of calibration conditions. I will continue by presenting an application of these techniques to the classification of Mink$_4 \times S^2$ solution in type II and M-theory, which is a preliminary step to find new compact solutions which overcame Maldacena-Nunez no-go theorem. In the end I will discuss how the bispinors reformulation can be used in the classification of non supersymmetric solutions.

Speaker: Mr Andrea Legramandi (University of Milano-Bicocca)

Slides Legramandi.pdf

49 Entanglement in CFTs with Discrete Gauge Symmetry and Bulk Reconstruction in AdS3

Due to the non-factorization of the Hilbert space into tensor products, the definition of entanglement entropy in gauge theories is subtle. It can be defined either by resorting to an algebraic approach or by embedding the state into an enlarged factorizing Hilbert space. The equivalence of these two approaches will be shown for entanglement between spatial degrees of freedom in 2d CFTs with $\mathbb{Z}_N$ gauge symmetry. Furthermore, the generalization to entanglement between non-spatially organized degrees of freedom (entwinement) will be considered. Lastly, holographic duals to both types of entanglement entropies will be constructed and the implications for the reconstruction of the bulk AdS$_3$ geometry will be explained.

Speaker: Marius Gerbershagen (Universität Würzburg)

Slides DESY_2019_Folien.pdf

50 Interface Flows in D1/D5 Holography

We construct Kondo-like flows in the D1/D5 system. Within CFT, the Kondo effect is described via branes which acquire additional dimensions. Starting from the D1/D5 system, we have found the BPS solutions to the DBI system describing Kondo-like RG flows between D1- and D3-brane solutions. Using a class of half BPS solutions we find corresponding backreacted supergravity interface solutions for at both fixed points and confirm the g-theorem. Our approach provides an explicit example of a Kondo-like CFT defect, with an explicit gravitational dual.

Speaker: Mr Christian Northe (Universität Würzburg)

Slides Desy_September19.pdf

51 Complexity for Quantum Fields: Quenches, Gaussian States and Purifications

We apply the recently developed notion of complexity for field theory to a quantum quench through a critical point in 1+1 dimensions. We begin with a toy model consisting of a quantum harmonic oscillator, and show that complexity exhibits universal scalings in both the slow and fast quench regimes. We then generalize our results to a one-dimensional harmonic chain, and show that preservation of these scaling behaviors in free field theory depends on the choice of norm. Applying our setup to the case of two oscillators, we quantify the complexity of purification associated with a subregion. We find that the complexity of subregions is subadditive, and comment on potential implications for holography.

Speaker: Mr Hugo Camargo (Max Planck Institute for Gravitational Physics)

Slides Slides for Parallel Session: String & Mathematical Physics on Complexity for Quantum Fields by H. Camargo (AEI)

Thursday 26 September

Plenary Session

Convener: Gleb Arutyunov (UHH)

52 Fundamental Aspects of Asymptotic Safety

Speaker: Frank Saueressig (Nijmegen U.)

Slides DESY_2019.pdf

Video https://webcast.desy.de/?recID=1055

53 Canonical Quantum Gravity in the Wilson Loop Representation

Speaker: Thomas Thiemann (IQG Erlangen-Nürnberg)

Video https://webcast.desy.de/?recID=1056

54 Cosmological perturbations in hybrid quantum cosmology

Speaker: Beatriz Elizaga de Navascues (FAU)

Slides BeatrizElizagaNavascues.pdf

Video https://webcast.desy.de/?recID=1057

10:30 Coffee break

Plenary Sessions

Convener: Holger Gies (U. Jena)

55 Perturbative supergravity and gauge theory

Speaker: Henrik Johansson (Uppsala)

Video https://webcast.desy.de/?recID=1058

56 Celestial operator products of gluons and gravitons.

Speaker: Andrew Strominger (Harvard)

Slides Desycelestial.pdf

Video https://webcast.desy.de/?recID=1059

12:30 Lunch

Parallel Session: Cosmology & Astroparticle Physics

57 Time-dependence of primordial power spectrum

Inflationary models based on particle physics naturally involve multiple fields in addition to the inflaton field. Consequently these multiple fields may contribute to inflaton correlation functions via loop corrections. We study the quantum corrections to the inflaton two-point correlation functions due to massive scalar and fermion fields, employing the Schwinger-Keldysh formalism. We shall first describe the model and the generic framework. We then discuss time-dependent features of the primordial power spectrum.

Speaker: Dr Jinsu Kim (Georg-August University Goettingen)

Slides JinsuKIM_DESYth2019.pdf

58 Nonlinear Dynamics of Preheating after Multifield Inflation with Nonminimal Couplings

We study particle production after multifield inflation with nonminimal couplings to gravity. A comparison between a linearized treatment and lattice simulations allows us to determine when nonlinear effects, such as rescattering and backreaction, become important. We track the equation of state on the lattice and show that it relaxes to 1/3. We also show that the spectra of the produced particles relax to thermal spectra. The duration of reheating depends on the value of the nonminimal coupling. For large values, reheating completes almost instantaneously, whereas for smaller values the energy density remains mostly in the inflaton field and some perturbative decay process is needed for reheating to complete.

Speaker: Jorinde Van de Vis (NIKHEF Amsterdam)

59 Dynamical Emergence of Scalaron in Higgs Inflation

We point out that a light scalaron dynamically emerges if scalar fields have a sizable non-minimal coupling to the Ricci scalar as in the Higgs inflation model. We support this claim in two ways. One is based on the renormalization group equation; the non-minimal coupling inevitably induces a Ricci scalar quadratic term due to the renormalization group running. The other is based on scattering amplitudes; a scalar four-point amplitude develops a pole after summing over a certain class of diagrams, which we identify as the scalaron. Our result implies that the Higgs inflation is actually a two-field inflationary model. Another implication is that the Higgs inflation does not suffer from the unitarity issue since the scalaron pushes up the cut-off scale to the Planck scale.

Speaker: Yohei Ema (DESY)

Slides DESY19_Ema.pdf

60 Towards a first principles treatment of warm inflation

“Warm Inflation” is an alternative to the standard inflationary paradigm in cosmology. It is characterized by a quasi-equilibrium between the dissipation due to particle production and the dilution due to the Hubble expansion, which keeps a thermal bath of radiation at a constant high temperature during inflation. We derive a quantum kinetic equation of motion for a slowly-rolling scalar field coupled to a thermal bath from first principles to address the question whether Warm Inflation can be realized consistently in the framework of quantum field theory. We employ the Schwinger-Keldysh formalism to systematically study thermal and quantum corrections to the effective potential that drives the dynamics of the field as well as to the dissipation coefficient that slows down its motion. While the effective potential is shown to have an expected parametric dependence, we show that the main contribution to the dissipation coefficient decreases with the temperature, which contradicts what is assumed in most phenomenological studies of Warm Inflation.

Speaker: Gilles Buldgen (UC Louvain)

Slides buldgen_slides.pdf

61 Primordial SU(2) Gauge fields and Particle Production in the Early Universe

Primordial SU(2) gauge fields coupled to axions can contribute to the physics of inflation. Their rich phenomenology and unique observational features, e.g., chiral primordial gravitational waves, turned this class of models to a hot topic of study since their discovery in 2011. In this talk, I will briefly review the models in this class, which so far have been studied in the literature. Then, I will talk about the three different types of particles produced by the SU(2) gauge field in this setup, i.e., scalar, fermion, and spin-2 particles. I will explain how the size of the backreaction constrains the parameter space of the models. Next, I will talk about the chiral gravitational waves and how it is produced by the extra spin-2 particle, which is the generic feature of this class of models. Finally, I will finish my talk by the natural inflationary leptogenesis setting provided by this class as their yet another generous opportunity!

Speaker: Azadeh Maleknejad (MPA Garching)

62 Axion Gauge Field Inflation

I will talk about early Universe inflation driven by an axion-like particle interacting with (non-) Abelian gauge fields. In the case of a non-Abelian gauge group, this can lead to the formation of a stable, homogeneous and isotropic gauge field background. However this only happens significantly after the relevant CMB scales left the horizon. This makes the model practically indistinguishable to Abelian axion inflation -- bringing non-Abelian axion inflation back as a viable inflation candidate. I will also discuss UV completions of the setup. This leads to significant parameter space restrictions. The remaining parameter space can be divided into three regimes. (i) For small gauge couplings we recover natural inflation. For large gauge couplings the non-Abelian gauge theory either (ii) mimics the Abelian theory over the whole inflationary dynamics or (iii) nonlinear interactions prohibit a linear analysis of the gauge field perturbations.

Speaker: Mr Stefan Sandner (IFIC / CSIC)

Slides presentation_desy_th_19_short.pdf

Parallel Session: Particle Phenomenology

Convener: Henning Bahl

63 Feebly interacting dark matter: from freeze-in to freeze-out

In my talk I will discuss the dependence of the dark matter production mechanism in the early universe on its coupling to the Standard Model and mediator. For illustration, I will focus on the case of compressed mass spectrum dark matter scenario and show that we can continuously go from freeze-in to freeze-out with an intermediate stage of conversion driven freeze-out. In the latter case, the feeble couplings involve give rise to the possibility to exploit the macroscopic decay length of charged mediators to study the resulting long-lived-particle signatures at collider. I will discuss the experimental reach of such searches on the viable portion of the parameter space.

Speaker: Laura Lopez Honorez (Université Libre de Bruxelles)

Slides Lopez-Honorez-DESY19.pdf

64 Strongly interacting dark sectors in the early Universe and at the LHC

I will discuss the cosmology and LHC phenomenology of a consistent strongly interacting dark sector coupled to Standard Model particles through a generic vector mediator. I will lay out the requirements for the model to be cosmologically viable, consider the dominant freeze-out processes and discuss bounds from direct detection. At the LHC the model predicts dark showers, which can give rise to semi-visible jets or displaced vertices. I will first focus on constraints from existing LHC searches and then discuss the sensitivity of proposed dedicated analyses for semi-visible jets. I will also emphasize the complementarity of different search strategies.

Speaker: Elias Bernreuther (RWTH-Aachen)

Slides strongdm_desy.pdf

65 Inelastic dark matter nucleus scattering

Speaker: Christian Doering (MPIK)

Slides InelasticDM.pdf

66 Finding hints of New Physics in Tritium molecular spectra

We are studying the effects of light New Physics that can materialise in deviations from the Coulomb potential on the length scale of molecules. Precision molecular spectroscopy thus sets complementary constraints on parameters that are not accessible in other type of experiments. We compare an estimate of the theoretical uncertainties to the available experimental precision in order to constrain classes of New Physics (light /pseudo/scalar, dark photon, neutrino force) and discuss how competitive this method is.

Speaker: Dr Wolfgang Gregor Hollik (KIT)

Slides NP_tritium.pdf

16:00 Coffee break

67 Constraining the MSSM Higgs sector in the low tanb region

We review recent progress in the calculation of the MSSM Higgs boson masses for low $M_A$ and $\tan\beta$ using the THDM as low-energy EFT. As an application of this calculation, we present two new Higgs benchmark scenarios valid in the region of low $\tan\beta$. While all SUSY masses are chosen relatively heavy in the first scenario, the second scenario features light neutralinos and charginos. Both scenarios are largely compatible with recent LHC results. We also discuss their main phenomenological features relevant for future LHC searches.

Speaker: Mr Henning Bahl (DESY Hamburg)

Slides DESY_theory_workshop_2019_Henning_Bahl.pdf

68 Event Generation with Deep Learning

Speaker: Sydney Otten (NIKHEF)

Parallel Session: String & Mathematical Physics

69 Quantum Gravity from Timelike Liouville

The Euclidean path integral of quantum gravity requires a proper definition because the kinetic term for the conformal factor of the metric comes with an additional minus sign. We propose a definition of two-dimensional quantum gravity with a cosmological constant based on the conformal bootstrap results of timelike Liouville theory coupled to matter. For the spectrum, we prove a no-ghost theorem for the states in the BRST cohomology. We then show that the crossing symmetric 4-point function constructed by gluing the timelike 3-point function with the Ribault-Santachiara contour for internal momenta, is well-defined when the external momenta are analytically continued to correspond to the physical states in the BRST cohomology.

Speaker: Dr Teresa Bautista (Max Planck Institute for Gravitational Physics)

Slides Bautista_-_DESYH_19.pdf

70 d=4 as the critical dimensionality of asymptotically safe interactions

After a short introduction to asymptotically safe quantum gravity, I explore the question why our universe is four dimensional from an asymptotically safe vantage point. I present indications that asymptotically safe quantum fluctuations of gravity could only solve the $U(1)$ Landau-pole problem in the Standard Model in four dimensions. This could single out the observed dimensionality of the universe, once the requirement of a minimalistic description of the microscopic building blocks of our universe in terms of Standard Model fields together with a quantum-field theoretic description of quantum gravity is made. Based on **Phys.Lett. B793 (2019) 383-389**.

Speaker: Marc Schiffer (Heidelberg University)

Slides DESY.pdf

71 Exact structure constants of determinant operators

In this talk, based on [1906.07733] with Y. Jiang and S. Komatsu, we derive the first non-perturbative result for the structure constants of two determinant operators and a non-BPS single-trace operator of finite length in planar $\mathcal{N}=4$ SYM. First, we introduce a new method based on large-N collective fields, which efficiently computes correlators of such non-single-trace operators in free theory and also realizes an example of Gopakumar's "open-closed-open" string triality. The form of the result supports the interpretation of the three-point function as an overlap between an integrable boundary state, which we determine using symmetry and integrability, and the state describing the single-trace operator. Second, we use thermodynamic Bethe ansatz to derive a non-perturbative expression for such overlap with an excited state in the SL(2) sector. Finally, we briefly discuss some interesting applications that could be addressed with the present methods.

Speaker: Dr Edoardo Vescovi (Imperial College London)

Slides Vescovi.pdf

72 Yangian Symmetry and Box Integrals

We report on progress in exploring the constraining power of the conformal Yangian symmetry that was recently found to be a feature of fishnet Feynman integrals. In particular, we explicitly investigate the four-point box and the six-point double-box integrals.

Speaker: Dr Florian Loebbert (Humboldt University Berlin)

73 Five-point functions of N=4 SYM at strong coupling

In this talk I consider five-point functions of N=4 SYM, which at strong coupling become AdS amplitudes in type IIB supergravity. I will show how to exploit symmetries and self-consistency conditions to bootstrap these amplitudes, which are naturally written in Mellin space. Finally, I will highlight the new data obtained and comment on generalizations of this work.

Speaker: Dr Raul Pereira (Trinity College Dublin)

Slides DESY_Raul.pdf

15:30 Coffee break

15:40 Coffee break

Parallel Session: Cosmology & Astroparticle Physics

74 Baryogenesis from axion inflation

The coupling of an axion-like particle driving inflation to the Standard Model particle content through a Chern-Simons term generically sources a dual production of massless helical gauge fields and chiral fermions. We demonstrate that the interplay of these two components results in a highly predictive baryogenesis model, which requires no further ingredients beyond the Standard Model. If the helicity stored in the hyper magnetic field and the effective chemical potential induced by the chiral fermion production are large enough to avoid magnetic diffusion from the thermal plasma but small enough to sufficiently delay the chiral plasma instability, then the non-vanishing helicity survives until the electroweak phase transition and sources a net baryon asymmetry which is in excellent agreement with the observed value. If any of these two conditions is violated, the final baryon asymmetry vanishes. The observed baryon asymmetry can be reproduced if the energy scale of inflation is around Hinf $\sim 10^{10}$ - $10^{12}$ GeV with a moderate dependence on inflation model parameters.

Speaker: Kyohei Mukaida (DESY)

Slides kmukaida.pdf

75 Measuring the Helicity of Intergalactic Magnetic Fields with Numerical Simulations in Astroparticle Physics

The origin of the first magnetic fields in the Universe is a standing problem in cosmology. Intergalactic Magnetic Fields (IGMFs) may be an untapped window to the primeval Universe, providing further constrains on magnetogenesis. We demonstrate the feasibility of using gamma rays from electromagnetic cascades originating from TeV blazars and Ultra-High-Energy Cosmic Rays (UHECRs) to constrain the helicity of IGMFs by performing simulations of their propagation in simple magnetic field and source configurations. We show that the arrival directions of the respective particles may be used to measure the absolute value of the helicity and its sign.

Speaker: Dr Andrey Saveliev (Immanuel Kant Baltic Federal University)

Slides Saveliev_TWS.pdf

76 Primordial Gravitational Waves in Standard and Non-standard Cosmologies

Using the quantum chromodynamics (QCD) equation of state (EoS) from lattice calculations we investigate effects from QCD on primordial gravitational waves (PGWs) produced during the inflationary era. We also consider different cases for vanishing and nonvanishing lepton asymmetry where the latter one is constrained by cosmic microwave background experiments. Also, we investigate scenarios that inflation is succeeded by a phase where the energy density of the Universe was dominated by a component with a general equation of state, we evaluate the spectrum of primordial gravitational waves induced in the post-inflationary Universe. We show that if the energy density of the Universe was dominated by some specific fluid 𝜙 before Big Bang Nucleosynthesis (BBN), its equation of state could be constrained by gravitational wave experiments.

Speaker: Dr Fazlollah Hajkarim (Goethe University Frankfurt)

Slides desy-hajkarim-2019.pdf

77 A closer look to the global shape of the scalar potential with gravitational waves

I will discuss the dependence of the parameters describing the gravitational waves produced in a first order phase transition (Tn, alpha, beta/H) on the global properties (e.g. height of the barrier) of the scalar that spontaneously tunnels between two vacua. Particularizing on the Higgs field, I will show the potential of gravitational wave observatories to unravel its global shape even when collider experiments are completely insensitive. Other aspects of the complementarity between colliders and gravitational wave experiments as well as connections to fundamental theories will be also discussed.

Speaker: Dr Mikael Chala (UGR & IPPP)

Slides Chala.pdf

78 Self-consistent gradient corrections to false vacuum decay for a U(1) gauge theory

Following previous work on self-consistent methods geared towards dealing with false vacuum decay in quantum field theory; a $U(1)$-gauge theory with a complex scalar is considered together with a polynomial potential which presents a metastable vacuum at tree level. Fluctuations around an inhomogeneous bounce-type background interpolating between vacua are studied and computed within a 1-PI effective action treatment and through a self-consistent prescription in order to incorporate gradients of the background. The self-consistent methodology also includes renormalization of the theory: coupling counterterms in a MS-like scheme and the wave-function renormalization obtained through a gradient expansion methodology. Corrections to the life-time of the metastable vacuum comprise: leading order contribution from the action at the tree-level bounce, plus self-energy corrections, counterterm contributions and corrections to the bounce background.

Speaker: Mr Juan S. Cruz (TUM)

Slides DESY2019Vacuum.pdf

79 Vacuum stability of Froggatt-Nielsen models

We discuss vacuum stability in Froggatt-Nielsen (FN) models. One concern in FN models is that for large flavon VEVs the running of the quartic Higgs coupling is enhanced what might lead to a more severe instability compared to the Standard Model (SM). We study this issue using the renormalization-group improved scalar potential. Another issue is that the mixing between the Higgs and the flavon can potentially destabilize the potential. However, taking current bounds on the flavon phenomenology, we find that both effects do not lead to an instability that is more severe than in the SM.

Speaker: Mr Felix Giese (DESY/Hamburg U.)

Slides DESYtheoryWorkshop2019Giese2.pdf

Parallel Session: String & Mathematical Physics

80 Scattering Amplitudes: Spinning Black Holes vs Soft Theorems

Motivated by the advent of LIGO and Virgo measurements, it has been observed that scattering amplitudes can be used to derive perturbative observables appearing in the collision of two black holes. In this talk we will cover recent progress in obtaining such quantities for the phenomenologically relevant setup of spinning black holes, focusing on radiation and the spin multipole expansion. These can be constructed via an exponentiated version of the Soft Theorem appearing in the classical limit of minimally coupled amplitudes. Time permitting, we will elaborate on the so-called classical double copy as an output of this construction.

Speaker: Mr Alfredo Guevara (Perimeter)

Slides QFTMG_slides.pdf

81 Unraveling conformal gravity amplitudes

Conformal supergravities are an intriguing class of theories; although they contain ghost-like states suggesting non-unitary behavior, they may have exceptionally good behavior in the ultraviolet regime. In this talk I will describe aspects of their tree-level scattering amplitudes, showing how they can be understood from double copy, Lagrangian, and string theory perspectives.

Speaker: Dr Gustav Mogull (Uppsala University)

Slides desy19.pdf

82 Using number theory to go from open- to closed string amplitudes at one-loop

When tree-level scattering amplitudes in open string theory are expanded in $\alpha'$, the coefficients are multiple zeta values (MZVs). These are mapped to a subset by the single-valued map from analytic number theory. As was proven recently, the corresponding MZVs in closed string amplitudes are just the single-valued image of the open string MZVs, therefore removing the need to calculate tree-level closed string amplitudes entirely. At one-loop, the expansion coefficients are functions of the modular parameters of the genus-one worldsheets associated to open or closed strings. Currently, several groups are working on finding an elliptic generalization of the single-valued projection to these objects which would make also the one-loop closed string calculation unnecessary. In particular, first promising results were obtained for four-point scattering in type-IIB. I will outline steps towards a generalization of these results which reveal more of the structure of the elliptic single-valued map.

Speaker: Mr Jan Gerken (Max Planck Institute for Gravitational Physics)

Slides TalkDESY2019.pdf

83 The Grand Slam of IIB Supergravity: 4pt @ 1-Loop.

We explore the structure of supergravity on AdS5xS5 at one loop, by constructing multi-channel four-point correlators for Kaluza Klein modes on the five-sphere. We do so by insisting on the consistency of the OPE of N=4 SYM, and using analytical bootstrap techniques. In particular, the presence of 1/N^4 contributions from protected double trace operators at the unitarity bound is a novel effect, and requires a careful multiplet recombination, unlike the tree level case. Since both the double discontinuity and (partially) the single discontinuity are predicted independently, the bootstrap problem is overconstrained. Will supergravity be able to find the solution? We show indeed that for a number of KK correlators there exists a unique solution, up to contact terms, such that all 1/N^4 predictions are correctly reproduced. This is work done in collaboration with James Drummond and Paul Heslop.

Speaker: Mr Francesco Aprile (Milano Bicocca University)

Slides Aprile_Hamburg.pdf

Hertz Lecture by Prof. Andrew Strominger (Harvard)

84 Probing the Edges of the Universe: Black Holes, Horizons and Strings

19:00 Conference dinner

Friday 27 September

Plenary Sessions

Convener: Johanna Erdmenger (U. Würzburg)

85 Gravitational Waves Meet Quantum Field Theory

Speaker: Alessandra Buonanno (AEI MPG)

Video https://webcast.desy.de/?recID=1060

86 The relativistic binary problem: theoretical challenges

Speaker: Jan Steinhoff (AEI MPG)

Slides steinhoff_desy_19.pdf

Video https://webcast.desy.de/?recID=1061

87 Precision Gravity: From the LHC to LISA

Speaker: Rafael Porto (DESY)

Slides DESYth.pdf

Video https://webcast.desy.de/?recID=1062

10:45 Coffee break

Plenary Sessions

Convener: Volker Schomerus (DESY)

88 The Landscape of Supersymmetric Symmetric Product Orbifolds

Speaker: Alejandra Castro (Amsterdam U.)

Slides DESY2019-ACastro.pdf

Video https://webcast.desy.de/?recID=1063

89 Dynamic of Tensor and SYK Models

Speaker: Igor Klebanov (Princeton)

Slides DESY-Klebanov.pdf

Video https://webcast.desy.de/?recID=1065

Closing