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.

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After a review of the spectrum of superstrings on the AdS3 WZW background, I will use a conjecture positing the existence of a phase transition, when the AdS radius becomes of order of the string length, to propose a holographic dual CFT that matches exactly the entire continuous spectrum of the superstring. I will conclude with a few observations on the role of interactions amd discrete, short-string states.

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In this talk I will reexamine the classification of BPS Wilson loops in 3d super Chern-Simons-matter theories. Over the last several years a large class of increasingly intricate constructions of such operators have been found. They involve both discrete and continuous parameters chosen to satisfy varied conditions. In my talk I will explain that the discrete parameters are related to choosing a graded quiver diagram, which may be a subquiver or a cover of the one defining the theory. The continuous parameters are then a singular limit of the variety, a complex manifold, associated to that quiver.

I will first provide a bird-eye view upon the infrared structure of gravity. I will shortly describe the relationship between BMS symmetry, soft theorems and memory effects at leading and subleading orders in the large radius expansion, while emphasizing the specificities of super-Lorentz symmetries. Secondly, I will present a no-go result on the soft hair conjecture: supertranslations induced by matter creating and falling inside black holes do not affect Hawking radiation, though they do affect scattering amplitudes. I will start by proving that Unruh radiation is unaffected by supertranslations induced by a shockwave and then show that Hawking radiation is mathematically related to this system, as a consequence of the principle of equivalence. Third, I will explain how BMS symmetry is associated to flux-balance laws that provide constraints upon the motion of binary compact mergers. Finally, I will present the extension of the BMS group to asymptotically de Sitter spacetimes.

I will describe thermodynamics and calculation of real time correlators in CFTs with extended W-symmetries, dual to AdS_3 gravity with a finite number of higher spin fields. I will point out mechanisms, including the appearance of a novel effective temperature, by which the proposed chaos bound due to Maldacena-Shenker-Stanford is violated in these theories.