Inflation is now the paradigmatic theory of the Big Bang. But is it deserved? I will describe the conceptual and theoretical challenges that Inflation is still facing, argue that we should keep an open mind. In particular, I will argue that while it is a theory that claims to be a theory of initial conditions of the Universe, successful inflation actually depends on an intimate interplay between its own initial conditions and the inflationary model. I will show how one might go about probing this interplay by testing whether inflation can begin if its own initial conditions are not homogenous. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.

We aim at formulating a higher-spin gravity theory around AdS2 relevant for holography. As a first step, we investigate its kinematics by identifying the low-dimensional cousins of the standard higher-dimensional structures in higher-spin gravity such as the singleton, the higher-spin symmetry algebra, the higher-rank gauge and matter fields, etc.

I will discuss recent progress towards understanding geometric and holographic aspects of electromagnetic duality in four-dimensional supergravity. More concretely, I will focus on the connection between electromagnetic duality and the existence of new classes of supersymmetric S-fold backgrounds of type IIB supergravity. These provide natural candidates to holographically describe new strongly coupled three-dimensional CFT’s which are localised on interfaces of N=4 super-Yang-Mills theory.

In this pedagogical talk I will discuss recent and ongoing work showing how quantum field theory problems can be embedded on to quantum annealers. The general method we use is a discretisation of the field theory problem into a general Ising model, with the continuous field values being encoded into Ising spin chains. To illustrate the method, and as a simple proof of principle, we have used a quantum annealer to recover the correct profile of various tunnelling solutions. Then I will discuss current work where we construct actual quantum tunnelling processes involving instantons. These methods are applicable to many nonperturbative problems. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi).

I will describe a class of supergravity solutions holographically dual to d-dimensional maximally supersymmetric SYM on S^d. Supersymmetric localization can be employed to calculate the partition function and the VEV of a 1/2-BPS Wilson lines in the planar limit of the SYM theory. I will present the results of this calculation and will show how they lead to a non-trivial precision test of holography in the context of non-conformal QFTs and space-times that are non asymptotically locally AdS.

Modified gravity models have been developed to try to explain the observed acceleration of the expansion of the Universe. Such models introduce and extra, fifth force, and usually employ a screening mechanism whereby the fifth force is screened in the solar system but unscreened cosmologically. Recent developments in laboratory experiments mean that such theories can now be tested and constrained using existing experiments. In particular innovative Casimir force experiments can be used to constrain such theories. This enables Einstein gravity to be tested on scales not previously explored. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.

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Non-abelian gauge theories underly particle physics, including collision processes at particle accelerators. Recently, quantum scattering probabilities in gauge theories have been shown to be closely related to their counterparts in gravity theories, by the so-called "double copy". This suggests a deep relationship between two very different areas of physics, and may lead to new insights into quantum gravity, as well as novel new computational methods. This talk will review the double copy for amplitudes, before discussing how it may be extended to describe exact classical solutions such as black holes. I will then look at recent work which aims to generalise the double copy yet further, and conclude with an outlook of current open problems. ----- Follow the usual link or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.

I will give a general overview of Higher Spin Gravities and also discuss the recent developments that give a class of models where UV-divergences of Einstein gravity cancel out thanks to the higher spin symmetry. At the end I will discuss the relation between Higher Spin Gravities and a class of conformal field theories in three dimensions that describe the physics of many second order phase transitions in the real world and have been recently conjectured to exhibit a number of remarkable dualities, in particular the three-dimensional bosonization duality. I will show how Higher Spin Gravity can help to prove the dualities and how it makes new predictions. The relation to QCD and self-dual Yang-Mills will also be discussed.

In this talk I will review the general ideas behind the recently developed relativistic effective field theories (EFTs) for different phases of matter (spontaneous symmetry breaking, Goldstone theorem, etc.). I will put particular emphasis on concretely building an EFT for the description of collective excitations in zero-temperature superfluids, which is the simplest of these theories. I will then argue that these methods, borrowed from high energy theory ideology, are mature enough to be successfully applied to phenomenologically relevant problems. In this direction, I will present two applications: (1) the calculation of the gravitational mass transported by a sound wave in a nonrelativistic medium (superfluid, fluid and solid), and (2) the study of the response of a He-4 detector to the passage of sub-MeV dark matter particle. ----- Follow the link in use since May 5th or contact the organisers (Antoine Bourget and Edoardo Vescovi). Student introduction at 13:00.

Inflation, an era of accelerated expansion of the universe prior to the radiation phase, constitutes the paradigm of primordial cosmology. Within this paradigm, the simplest single-field slow-roll models economically explain all current data. However, the sensitivity of inflation to Planck scale physics, and the fact that ultraviolet completions of inflation invariably involve extra fields coupled to the inflaton, indicate that these models constitute at best a phenomenological description that emerges from a more realistic physical framework. In this talk, I will describe recent works that aim at understanding the consequences of the presence of several degrees of freedom during inflation. In particular, I will highlight that realistic models are characterized not only by their potentials but also by the internal geometries in which the fields live in, and I will discuss related novel phenomena that have been studied in the past years. ----- Contact the organisers (Antoine Bourget and Edoardo Vescovi) for the link.

The past decade has seen an explosion of progress in our understanding of scattering amplitudes in gauge theory and gravity. New bootstrap methods have revealed hidden symmetries and new mathematical structures that are completely invisible in the standard approach of Lagrangians and Feynman diagrams. Inspired by these developments, the bootstrap philosophy has recently been applied to cosmology. In this talk, I will describe our work on the bootstrapping of cosmological correlations. The talk will have two parts: In the first part, I will describe the conceptual foundations of the "cosmological bootstrap" as developed together with Arkani-Hamed, Lee and Pimentel in [arXiv:1811.00024]. In the second part, I will describe the extension of these ideas to massless particles with spin, where locality provides important new constraints. This is work to appear with Duaso Pueyo, Joyce, Lee and Pimentel. ----- Contact the organisers (Antoine Bourget and Edoardo Vescovi) for the link.

Subregion duality is an idea in holography which states that every subregion of the boundary theory has a corresponding subregion in the bulk theory, called the 'entanglement wedge', to which it is dual. In the classical limit of the gravity theory, we expect the fields in the entanglement wedge to permit a Hamiltonian description involving a phase space and Poisson brackets. In this talk, I will describe how this phase space arises from the point of view of the boundary theory. In particular, I will explain how it emerges from measurements of a certain quantum information-theoretic quantity, known as the 'Uhlmann phase', in the boundary subregion.

In recent years the use of effective field theory techniques has come to the fore when studying the LHC data set. This approach constrains the possible effects of physics beyond the Standard Model, by constraining small modifications of Standard Model interactions in a theory known as the Standard Model Effective Field Theory. Although highly practical and agnostic, the presence of a Higgs field that takes on a background expectation value leads to some unique challenges in formulating this effective field theory and interfacing the SMEFT with the data. We will review some of the successes of this approach and some of the problems that have appeared. A growing understanding of the physics of the SMEFT as emerging from the geometry of Higgs field space offers great potential to tackle some of the remaining challenges. We will also introduce and discuss this approach.

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I will review the current status of the asymptotic safety program, focusing on the predictive power of scale invariance, followed by a collection of results on how the Standard-Model couplings may be used to constrain physics at the Planck scale. At a time in which collider measurements collect increasing evidence that the Standard Model as an effective field theory is consistent up to the Planck scale, its marginal couplings offer a unique opportunity to learn about quantum gravity. I will also briefly introduce a research program aimed at constraining the marginal couplings of the gravitational sector, i.e., curvature-squared terms, via black-hole stability and binary mergers.

The Quantum Spectral Curve (QSC) is a powerful integrability-based framework capturing the exact spectrum of planar N=4 SYM. We present first evidence that it should also play an important role for computing exact correlation functions. We compute the correlator of 3 scalar local operators connected by Wilson lines forming a triangle in the ladders limit, and show that it massively simplifies when written in terms of the QSC. The final all-loop result takes a very compact form, suggesting its interpretation via Sklyanin's separation of variables (SoV). We discuss work in progress on extending these results to local operators. We also derive, for the first time, the SoV scalar product measure for gl(N) compact and noncompact spin chains. Based on arXiv:1910.13442, 1907.03788, 1802.0423.

The large-charge approach consists in studying conformal field theories in sectors of fixed and large global charge. This allows performing a perturbative expansion of a generically strongly-coupled theory with the inverse charge acting as a controlling parameter. In this talk, I will present the basic idea of the large-charge expansion using the simplest example of the 3D O(2) model at the Wilson-Fisher fixed point, as well as its application to other models.

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A lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Motivated by this, I will present a feasible idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. I will show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. A prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, is also provided and can be measured through simple spin correlations. Further, I clarify the assumptions underpinning the above proposal such as our reasonable definition of "classicality", as well as the crucial aspect of the locality of physical interactions. The role of off-shell processes is also highlighted. How the experiment sits within relativistic quantum field theory is clarified. Lastly, the practical challenges are noted. Time permitting other applications of superpositions of nano-crystals, such as in sensing classical gravity and how to detect nonclassicalities of such crystals without preparing superpositions at first, will be discussed.