La journée des thèses du CPHT a lieu le jeudi 29 janvier 2026 dans la salle de conférence Jean Lascoux à partir de 9H00.

Programme

Speaker: André Pinheiro

Time: 14:00 pm, Jan 28th Wednesday  

Location: Salle de Conférence Louis Michel

Title:  Holographic fluids with higher-form symmetries

Abstract: Higher-form symmetries are ubiquitous in physics. In this talk, I focus on the case where they are continuous and encode the conservation of extended objects. Applications include elasticity, superfluidity and phases of electromagnetism. Using holography, we explore effective descriptions of systems with the simplest case of a single higher-form symmetry. For energies well below temperature, these descriptions admit a (potentially extended) hydrodynamic regime. We verify this explicitly by studying AlAdS black branes charged under higher-form potentials. In particular, we compute quasinormal modes, starting with the low-density limit. Then, we focus on the bulk dual of a viscoelastic system and analyse instabilities for different equilibrium states corresponding to isotropic crystalline phases.

Spaeker: Rodrigo Olea

Time: 14:30 pm, Jan 23th Friday  

Location: Salle de Conférence Louis Michel

Title: Holographic Weyl Anomaly and Kounterterms

Abstract: The addition of Kounterterms leads to a finite action for Einstein gravity for asymptotically AdS spaces with a conformally flat boundary. In that sense, it provides a partial renormalization scheme when compared to standard holographic techniques. However, Kounterterms method has the advantage that they can be written down in an arbitrary dimension. In this talk, we show how to extract holographic information on conformal anomalies from the variation of odd-dimensional Einstein-AdS plus Kounterterms.

Spaeker: Sebastian Waeber

Time: 15:30 pm, Jan 21th Wednesday  

Location: Salle de Conférence Louis Michel

Title: Driven holographic turbulence and random gravity

Abstract: The fluid/gravity correspondence, the duality between black hole dynamics in Anti-de Sitter space and hydrodynamics, may be used to geometrize turbulent flow. Our goal is to translate the long-standing problem of explaining anomalous scaling exponents of fluid velocity structure functions into a language of gravity. We study the fluid phase of conformal matter driven by a randomly fluctuating gravitational potential, numerically solving the evolution of a black hole in Anti-de Sitter space with a fluctuating, stochastic boundary metric. Subtleties regarding the fluid's compressibility in this set up are discussed. We observe a scaling behavior of the energy power spectrum that is consistent with compressible flow and compute the energy dissipation and the fluid velocity distribution. We identify observables in the dual gravity theory corresponding to higher moments of the averaged energy dissipation which help to map anomalous scaling exponents to covariant quantities defined on the dual horizon.

Time: 15:30 pm, Jan 14th Wednesday  

Location: Salle de Conférence Louis Michel

Martin Pico (Universidad Autonoma de Madrid)

Title: Classifying consistent truncations from Exceptional Generalised Geometry

Abstract: Consistent truncations have proven to be one of the main tools to study low-dimensional effective theories of string theories. In this talk, I will discuss how new U-duality covariant formulations of higher-dimensional supergravities, Exceptional Generalised Geometries (EGG) and Exceptional Field Theories (ExFT), can be used to classify the possible consistent truncations that can be obtained from such higher-dimensional supergravities.

Des chercheurs du Centre de Physique Théorique proposent un formalisme théorique qui offre une description de la gravité et des ondes gravitationnelles au « bord » de l’Univers.

Dans une Lettre récemment publiée dans Physical Review Letters [1], une équipe de chercheurs dirigée par Marios Petropoulos (directeur de recherches CNRS, CPHT), composée d’Adrien Fiorucci, Simon Pekar et Matthieu Vilatte (anciens ou actuels membres du CPHT), propose une dérivation intrinsèquement définie sur le bord des équations dynamiques de la gravitation d’Einstein dans le cadre de l’holographie en espace-temps plat. Cette approche repose sur la géométrie carrollienne et constitue l’aboutissement de méthodes développées de longue date au CPHT, où existe une expertise reconnue dans ce domaine. Cette avancée théorique ouvre de nouvelles perspectives vers l’unification de la relativité générale et de la mécanique quantique.

[1] Adrien Fiorucci, Simon Pekar, P. Marios Petropoulos and Matthieu Vilatte, Carrollian-Holographic Derivation of Gravitational Flux-Balance Laws, Phys.Rev.Lett. 135, 261602, https://journals.aps.org/prl/abstract/10.1103/qv17-ks32

Communiqué de presse de l’École polytechnique

Image : vue d'artiste d'un espace-temps émergeant de manière holographique. Crédit : A. Fiorucci.

Liam Rampon soutiendra publiquement ses travaux de thèse le jeudi 18 décembre 2025 à 14h00 au Collège de France à 9h30

Titre : "Étude des matériaux fortement corrélés avec des outils numériques modernes : de la théorie du champ moyen dynamique aux trains de tenseur"

Directeur de thèse : Michel Ferrero

Lien zoom : https://ecolepolytechnique.zoom.us/j/8629709572

Le séminaire des jeunes chercheurs du CPHT aura lieu le jeudi 11 décembre 2025 à 14h00 à la Salle de conférence Louis Michel avec deux présentations :

Anna Ritz-Zwilling, on Topological order in two dimensions at finite temperature

Thomas Pochart, The conformal bootstrap: A tale of fantastic hopes and results.

Le séminaire sera suivi d'un goûter.

The particle physics group will be hosting a seminar by mathematical physicist Adrien Florio (Bielefeld U.) on Friday December 19th at 1pm in salle Louis Michel.

Thermalization and entanglement structures of relativistic fields: explorations in low-dimensions

Past decades have revealed the crucial role played by the entanglement structure of quantum states in explaining both phases of matter and thermalization—the emergence of statistical physics from unitary time evolution. Yet our understanding of entanglement in relativistic field theories remains limited, largely confined to conformal and holographic settings. At the same time, we don't have a clear picture of how our universe actually reached thermal equilibrium after inflation. We do not understand why the quark-gluon plasma produced in heavy-ion collisions thermalizes so fast, or what the actual phase diagram of QCD is. In this talk, I illustrate how progress can be made in filling this gap starting from the study of one-dimensional relativistic field theories. I present results on the real-time dynamics of the massive Schwinger model, which shares key features with QCD. In this setup, the medium created by hard back-to-back particles thermalizes through entanglement production. I then move on to discuss how a refined understanding of entanglement in relation to symmetries can serve as a practical tool for detecting and characterizing different phases of matter. Indeed, the so-called "entanglement asymmetry" related to the chiral symmetry in the Schwinger model can be computed analytically in the massless limit, as a function of temperature. Remarkably, it is parametrically more sensitive to symmetry breaking than the corresponding local order parameter, the chiral condensate.

Séminaire conjoint LSI+CPHT+PMC = M4S

Jeudi 18 décembre à 11h00

Nouvelle salle de séminaire PMC (05-10-26A)

Yuimaro Kubo
(Principal Research Scientist à l'Okinawa Institute of Science and Technology au Japon)

Title: A near-quantum-limited diamond maser amplifier

Abstract: Microwave quantum technologies require amplification of weak signals with minimal added noise at millikelvin temperatures. This stringent demand has traditionally been met by superconducting parametric amplifiers. We demonstrate the first-ever non-superconducting microwave amplifier with near-quantum-limited noise performance, based on a maser operating at millikelvin temperatures. The active medium comprises substitutional nitrogen defects (P1 centers) in a diamond crystal, placed within a microwave resonator. Our device delivers over 30 dB of gain at 6.595 GHz, and the minimum noise temperature of about 1 K, corresponds to an added noise of 3 quanta. The amplifier features 20 to 30 dB higher compression points than the state-of-the-art superconducting devices.