Le Centre de Physique Théorique (CPHT) réunit des chercheurs dont les activités couvrent un large spectre de la Physique, tant dans ses aspects fondamentaux qu'appliqués.
Le CPHT est une unité mixte de recherche (UMR 7644) du Centre National de la Recherche Scientifique (CNRS) et de l’Ecole polytechnique. Au niveau du CNRS, il est rattaché à l’Institut de physique. Le CPHT a également un partenariat avec le Collège de France.
Le CPHT, dirigé par Jean-René Chazottes, directeur de Recherche au CNRS, est implanté sur le campus de l’Ecole Polytechnique à Palaiseau, dans le bâtiment 6 et dans l'aile 0 du bâtiment 5. Le secrétariat se situe dans le Bâtiment 6, bureaux 06.1046 et 06.1045. 
 

Adresse postale : 
CPHT 
Ecole Polytechnique 
91128 Palaiseau cedex 
France

Tél. Secrétariat : 01 69 33 42 01

Pour écrire un email à un membre du laboratoire : prenom.nom@polytechnique.edu

 

Séminaires des Cordes
le mercredi 23 mars 2022
Salle de conférence Louis Michel, CPHT, Ecole Polytechnique

11h - 11h45
Luca Ciambelli
Universal symmetries of gravity

Abstract: I will derive the universal group of symmetries stemming from diffeomorphisms on a codimension-2 surface S at finite distance. I will then compute Noether charges in Einstein gravity and prove that, treating the embedding fields carefully, their algebra is a faithful representation of the aforementioned group of symmetries. This is then shown to be canonically realized on a suitably enlarged covariant field space, where one treats the embedding fields as part of the field space. This solves an old question in gravity, which is to find a field space where all gravitational charges are canonical, i.e. integrable, and thus represented through Poisson brackets.

12h - 12h45
Romain Ruzziconi
A Carrollian Perspective on Celestial Holography

Abstract: I will present a holographic description of gravity in 4d asymptotically flat spacetime in terms of a 3d sourced conformal Carrollian field theory. The external sources encode the leaks of gravitational radiation at null infinity. The Ward identities of this theory are shown to reproduce those of the 2d celestial CFT after relating Carrollian to celestial operators. This suggests a new set of interplays between gravity in asymptotically flat spacetime, sourced conformal Carrollian field theory and celestial CFT. 

Indéfini

 

Aspects of gravity, mathematics and physics
21-22 mars 2022 Palaiseau (France)

Amphithéâtre Becquerel, École Polytechnique

Cette conférence est organisée par le Centre de Mathématiques Laurent Schwartz et le Centre de Physique Théorique de Polytechnique.

Orateurs

Nicolas Besset (Paris Saclay) Guillaume Bossard (Polytechnique)
Eleonora Di Nezza (Polytechnique)
Grigorios Fournodavlos (Université de Crète et Université de Princeton)
Jose Luis Jaramillo (Université de Bourgogne Franche-Comté)
Leonhard Kehrberger (Université de Cambridge)
Blagoje Oblak (Polytechnique et Sorbonne Université)
Harvey Reall (Université de Cambridge)
Danièle Steer (Université de Paris)
Martin Taylor (Imperial College)
Michal Wrochna (Université de Cergy)
Zoe Wyatt (King's College London)

Organisateurs

Dietrich Häfner (UGA), Cécile Huneau (Polytechnique), Karim Noui (Paris Saclay), Marios Petropoulos (Polytechnique)

Inscription obligatoire ici

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Indéfini

 

Marcello Turtulici soutiendra publiquement ses travaux de thèse le 10 décembre 2021  au CPHT, Salle de conférence Louis Michel.

Titre de la thèse : "Ab-initio investigation of non-stoichiometric transition metal oxides"

Composition du Jury

Rapporteurs : Ferdi Aryasetiawan, Jan Martin Tomczak
Presidente : Lucia Reining
Examinateurs : Dipankar Das Sarma, Alaska Subedi
Directrice de these : Silke Biermann

Indéfini

 

Le 2éme séminaire des jeunes chercheurs du CPHT aura lieu le 9 décembre  2021 à 15h00 à la Salle de conférence Louis Michel avec trois présentations  :

Yorgo Pano : Celestial holography in a nutshell

Duifje van Egmond : A novel background field approach to the confinement-deconfinement transition

Benjamin Bacq-Labreuil : Into the physics of real copper oxide materials

Le séminaire sera suivi d'un goûter.

Français

 

Xiang ZHAO soutiendra publiquement ses travaux de thèse le jeudi 25 novembre 2021 à 10h00 au CPHT, Salle de conférence Louis Michel.

Titre de la thèse : "Aspects of Conformal Field Theories and Quantum Fields in AdS"
Directeur de thèse : Balt Van Rees

Participer à la réunion Zoom pour la soutenance de thèse :
https://us06web.zoom.us/j/87068486326?pwd=a0JMRkZBdEpkYzVDR0h4N2piQ1hNUT09
Meeting ID: 870 6848 6326
Passcode: 245657

Composition du Jury

(1) Christopher BEEM, Associate Professor, Oxford University (Rapporteur)
(2) Nikolay BOBEV, Associate Professor, KU Leuven (Rapporteur)
(3)Costas BACHAS, Directeur de Recherche, ENS (Examinateur)
(4) Christoph KOPPER, Professeur, Ecole Polytechnique (CPHT) (Examinateur)
(5) Eric PERLMUTTER, Assistant Professor, Saclay (IPHT) (Examinateur)
(6) Balt VAN REES, Professeur, Ecole Polytechnique (CPHT) (Directeur de thèse)

Abstract

"This thesis studies the structure and the space of conformal field theories (CFTs), and more generally various properties of conformal correlation functions. It extends into multiple directions, both perturbative and non-perturbative, local and non-local, with and without supersymmetry.
The first aspect concerns the conformal correlation functions in d-dimensional spacetime and their relation to flat-space S-matrices in (d+1)-dimensional spacetime. The connection is built up by considering a quantum field theory (QFT) in a fixed (d+1)-dimensional Anti-de Sitter (AdS) background and sending the radius of the AdS curvature to infinity. That is, the central object to study is the flat-space limit of QFT in AdS. The analysis starts from taking the flat-space limit of the building blocks of Witten diagrams, namely the bulk-boundary and bulk-bulk propagators. This analysis leads to conjectural generic prescriptions to extracting flat-space physics from conformal correlators. Interestingly, the intuitional picture that a Witten diagram simply reduces to the corresponding Feynman diagram does not always hold, and the origin of this discrepancy lies in the bulk-bulk propagators: they could have two different flat-space limits. One of the limits always exists and reduces to Feynman propagator, while the other, when present, can diverge in the flat-space limit. This observation is tested by explicit examples, including fourpoint scalar contact, exchange and triangle Witten diagrams and the conjectures are expected to work whenever the scattering energy is large enough.
The second aspect studies the classification problem of conformal defects. The goal is to partially answer the question: given a bulk CFT and consistency conditions such as crossing symmetry and unitarity, what are the allowed conformal defects with a non-trivial coupling to the bulk? Analytic bootstrap techniques are applied to study a simplified version of this problem where in the bulk only a single free scalar field is considered. Analysis of various three-point functions among bulk and defect fields leads to the conclusion that almost all the n-point correlation functions of defect fields are completely fixed up to a potentially unfixed one-point function. This analysis also leads to an intermediate result in which it is proven that the n-point correlation functions of a conformal theory with a generalised free spectrum must be those of the generalised free field theory."

The third aspect studies the interplay between analyticity in spin in CFTs and supersymmetry. Operator spectrum in a general unitary CFT is expected to be captured by a function analytic for spin J>1, and the operators are organised into various Regge trajectories. The presence of supersymmetry in general extends the region of analyticity in spin. The 6d N=(2,0) superconformal field theories (SCFTs) is considered as a concrete example, in which analyticity in spin is expected to hold down to J>−3. Detailed analysis of the four-point function of the the stress tensor supermultiplet uncovers an unexpected interplay between unprotected and protected multiplets: the stress tensor multiplet can be found on a long (unprotected) Regge trajectory when analytically continued to spin J=−2. In this study a general iterative bootstrap program is also established, which applies to all SCFTs that have a chiral algebra subsector.

 

Indéfini

La Journée des Thèses du CPHT a lieu à l'amphi Becquerel dans le grand hall le vendredi 26 novembre 2021.

Programme

9h - 10h30

Sabine Harribey (A quick review of melonic CFTs - visio)
Jean-Gabriel Thiriet (Non-modal hydrodynamic stability analysis of ablation flows relative to inertial confinement fusion)
Matthieu Vilatte (Geroch method from holography fluid/gravity)
Ephraim  Bernhardt (Topology and disorder)
Yorgo Pano (Celestial holography)
Frederick del Pozo (Quantum field theory for topological superconductors)
David Rivera Betancour (Aspects of fluids and flat holography)

11h - 12h30

Filippo Sottovia (Can hydrodynamics correctly describe instabilities in superfluids? A holographic approach)
Gabriele Casagrande (The Swampland program and SUGRA inflationary models)
Erik Linner (Electronic correlations in incommensurate materials)
Long Zou (Propagation of ultra-fast laser pulse and filamentation in the air)
Benjamin Bacq-Labreuil (Exploring the physics of strongly correlated copper oxyde systems)
James Boust (Magnetism in correlated f-electron intermetallics)
Mohamed Rekhis (Toroidal alfven eigenmodes destabilisation by energetic particles in tokamaks)

14h - 15h30

Julian Legendre (Topological properties of the kagome lattice and light-matter systems)
Majdouline Borji (Perturbative renormalization of the semi-infinite phi_4^4 theory with flow equations)
Adrien Loty (Constraints on effective theories of quantum gravity)
Renaud Garioud (Perturbation theory for symmetry-broken systems: application to the Néel phase transition)
Marcos Gonzalez (Jet quenching in heavy ion collisions)
Zhaoxuan Zhu (Two-dimensional cold atoms in a quasicrystal lattice)
Jan Schneider (Out-of-equilibrium dynamics in long-range interacting many-body physics)

16h -16h50

Nahuel Barrios (Perturbative study of long-distance non-abelian gauge theories - visio)
Balthazar de Vaulchier (Wavefunction of the universe)
William Focillon (Mechanical properties of the nucleon in the scalar diquark model.)
Pauline Besserve (Unraveling strongly-correlated materials’ properties with noisy quantum computers)

Goûter

Français

!! Changement de lieu : La soutenance aura finalement lieu dans la salle de conférence du Centre de Mathématiques Laurent Schwartz 

Anh-Dung Le soutiendra publiquement ses travaux de thèse le vendredi 19 novembre 2021 à 14h30 au CPHT, Salle de conférence Louis Michel.

Titre de la thèse : "Statistical properties of partonic configurations and diffractive dissociation in high-energy electron-nucleus scattering"
Directeur de thèse : Stéphane Munier

Composition du Jury

(1) Stéphane Munier, CNRS (France), Directeur de thèse
(2) Yuri Kovchegov, The Ohio State University (USA), Rapporteur
(3) Tuomas Lappi, Jyvaskyla University (Finland), Rapporteur
(4) Nestor Armesto, Universidade de Santiago de Compostela (Spain), Examinateur
(5) Cédric Lorcé, Ecole polytechnique (France), Examinateur
(6) Grégory Schehr, CNRS (France), Examinateur

Abstract

"In the high-energy scattering of a quark-antiquark color dipole off a hadron, the quantum states of the former are represented by a stochastic set of dipoles generated by a binary branching process, in the so-called color dipole model of quantum chromodynamics (QCD). It was found that there is a profound connection between this QCD description and the branching-diffusion processes studied in statistical physics from which different properties of the scattering in the high-energy regime are revealed. Our work in this thesis is aimed to exploit the cross-fertilization between QCD and statistical physics to study the detailed partonic content of the Fock states of a color dipole subject to high-energy evolution in the scattering off a large nucleus. We also produce predictions for diffractive dissociation in electron-ion collisions, based on the QCD dipole picture. In the first place, the scattering events of a color dipole, when parameters are set in such a way that the total cross section is small, are triggered by configurations containing large-transversesize dipoles. The latter are due to rare partonic fluctuations, which look different as seen from different reference frames, from the rest frame of the nucleus to frames in which the rapidity is shared between the projectile dipole and the target nucleus. It turns out that the freedom to select a frame allows to deduce an asymptotic analytic expression for the rapidity distribution of the first branching of the slowest parent dipole of the set of those which scatter, which provides an estimator for the correlations of the latter. In another aspect, the study implies the importance of the characterization of particle distribution near the extremal particles, referred to as the \tip", in the states generated by the QCD dipole branching, and more generally, by any one-dimensional branching random walk model. To this aim, we develop a Monte Carlo algorithm to generate the tip of a binary branching random walk on a real line evolving to a predefined time, which allows to study both rare and typical configurations. The above statistical description proves advantageous for calculating diffractive cross section demanding a minimal rapidity gap Y0 and the distribution of rapidity gaps Y_{gap} in the diffractive dissociation of a small dipole off a large nucleus, in a well-defined parametric region. They are the asymptotic solutions to the Kovchegov-Levin equation, which was established more than 20 years ago to describe the diffractive dipole dissociation at high energy. Additionally, we present predictions for the distribution of rapidity gaps in realistic kinematics of future electron-ion machines, based on the numerical solutions to the original Kovchegov-Levin equation and of its next-to-leading extension taking into account the running of the strong coupling. The outcomes for the former reflect in a qualitative way our asymptotic analytical result already at rapidities accessible at future electron-ion colliders."

Indéfini

 

Une collaboration internationale impliquant des chercheurs du CPHT a mis en évidence une nouvelle technique de génération d'impulsions brèves de lumière visible. En injectant un laser infrarouge dans une fibre creuse, des chercheurs de l'Institut National de la Recherche Scientifique (Canada) ont en effet pu créer des impulsions très courtes de lumière visible à la sortie, sans avoir besoin de les comprimer. Cette technique tire partie du caractère multimode de la fibre pour favoriser le transfert de l'énergie infrarouge vers le visible.

Arnaud Couairon, directeur de recherche CNRS au CPHT et Jeff Brown (post-doctorant au CPHT de 2016 à 2019) ont participé à élaborer le modèle théorique de ce phénomène avec leurs collaborateurs de l'Université de Louisiane (USA) et l'Université Heriot-Watt (Écosse). Leurs travaux ont été publiés dans la prestigieuse revue Nature Photonics.

Français

 

Le 1er séminaire des jeunes chercheurs du CPHT aura lieu le 27 octobre 2021 à 15h00 à la Salle de conférence Louis Michel avec trois présentations par les doctorants :

Majdouline Borji : Perturbative renormalization of the semi-infinite massive scalar field theory using the flow equations

Pauline Besserve : Unraveling correlated materials’ properties with noisy quantum computers

William Focillon : Potential Linear and Angular Momentum in the Scalar Diquark Model

Le séminaire sera suivi d'une goûter.

Français

 

Thibaut coudarchet soutiendra publiquement ses travaux de thèse le 30 septembre 2021 à 14h00 à l'Ecole polytechnique, Amphi Lagarrigue.

Titre de la thèse : Théorie des cordes : brisure de supersymétrie, stabilisation des modules et aspects cosmologiques
Directeur de thèse : Hervé Partouche

Mots-clés : Théorie des cordes,Brisure de supersymétrie,Modules,Cosmologie

Participer à la réunion Zoom pour la soutenance de thèse :
30 sept. 2021 02:00 PM Paris
Zoom link:
https://us02web.zoom.us/j/81787410532
ID: 817 8741 0532

Composition du Jury

M. Hervé PARTOUCHE, École polytechnique,Directeur de thèse
Mme Mariana GRAÑA,IPhT, CEA/Saclay, Rapporteure
M. Dan ISRAËL,LPTHE, Sorbonne Université, Rapporteur
M. Ignatios ANTONIADIS, LPTHE, Sorbonne Université, Examinateur
M. Augusto SAGNOTTI, École Normale Supérieure de Pise, Examinateur
M. Jan TROOST,LPENS, École Normale Supérieure, Examinateur
M. Toumbas NICOLAOS, Département de physique, Université de Chypre, Examinateur

Français

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