Mardi 10 Mars 2026, 10:45 à LPTMC, campus Jussieu, couloir 12-13, 5ème étage, salle 5-23	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Rémy Mosseri ( LPTMC )	Vers une phyllotaxie tridimensionnelle
Abstract:	Inspirés par l'observation de certaines croissances spirales de plantes, les arrangements phyllotactiques bidimensionnels sont des exemples très intéressants de structures homogènes non périodiques engendrées par des règles simples. En séparant les parties radiales et angulaires , ils peuvent par ailleurs être généralisés à des surfaces de courbure positive ou négative. Nous décrirons ici plusieurs essais de généralisation à trois dimensions de ce type d'arrangements. Un premier exemple reprend la modalité de construction des réseaux périodiques compacts à 3D par empilement itérés de réseaux triangulaires sur les espaces interstitiels des couches précédentes. Une seconde approche procède différemment, par croissance radiale, soit de façon automatique en suivant une règle simple, ou bien de façon numérique en minimisant un potentiel d'interaction. Deux autres modèles, pouvant également donner lieu à des structures intéressantes dans R3 seront présentés : un ensemble phyllotactique sur la sphere S3 construit autour d'une fibration de Hopf discrète, et un autre à 4 dimensions obtenu comme produit de deux structures phyllotactiques 2d. Reference : Some attempts toward 3-dimensional phyllotaxy, Rémy Mosseri and Jean-François Sadoc, Structural chemistry , vol 36, pages 1963–1972 (2025)

Mardi 10 Mars 2026, 11:00 à CPHT, Salle de Conférence Louis Michel	SEM-CPHT (Séminaire du CPHT)	hep-th
Nelson Merino Moncada ( Universidad Arturo Prat )	The Katz, Bicák and Lynden-Bell (KBL) regularization and its applications
Abstract:	The Katz boundary term provides a well-defined variational principle under Dirichlet boundary conditions and, when combined with a subtraction of the action evaluated on a background, known as the KBL regularization procedure, yields finite Noether charges and a finite on-shell action. This boundary term is constructed from the dynamical metric and the difference between the Christoffel symbols associated with the dynamical manifold and a reference background. So far, this method has been tested only for specific solutions. In this work (soon to be submitted for publication), using the Fefferman-Graham gauge, we show that the finiteness of conserved charges can be proven for families of asymptotically locally Anti–de Sitter spacetimes in general relativity. The finiteness of the charges can be established in arbitrary dimensions; however, the prescription for defining the background in this framework distinguishes between even and odd spacetime dimensions. Other possible applications and potential relations with the covariant phase space method will also be discussed.

Mardi 10 Mars 2026, 11:00 à IPHT, Amphi Claude Bloch, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Radu Roiban ( Penn State U. )	How Quantum Scattering Amplitudes Can Help With Precision Gravitational Wave Physics
Abstract:	The observation of gravitational waves by the LIGO/Virgo collaborations has opened a new window onto our Universe, and upcoming experiments promise increasingly precise measurements. In parallel developments, building on the insight that gravity is mediated by a massless spin-2 particle, quantum scattering amplitude methods?originally developed for particle physics?provide a novel framework to study gravity and have already impacted weak-field, fully relativistic predictions for gravitational-wave signals. After outlining the growing need for high-precision analytical predictions in light of current and future gravitational wave observations, we will review the scattering-amplitude-based approach to gravitational wave observables, highlighting both its recent successes and some of the remaining challenges for achieving the accuracy required by the expected experimental data.

Mardi 10 Mars 2026, 11:30 à LPTHE, LPTHE library	SEM-LPTHE (Séminaire du LPTHE)	hep-th
Ioannis Tsiares ( LPENS )	Quantum modularity aspects of the Virasoro Crossing Kernels in 2d CFTs
Abstract:	We will discuss recent analytic progress on the "non-rational" Virasoro Crossing Kernels that implement modular and crossing transformations on torus 1-point and sphere 4-point Virasoro blocks, respectively, in 2d CFTs. These kernels are realized as solutions to special difference equations arising, in turn, from the "non-rational" versions of the Moore-Seiberg polynomial relations. Using techniques from quantum topology and the so-called `state integrals', we will show that at rational values of the central charge in the regime (-\infty,1]U[25,+\infty), and generic Liouville momenta, there are new solutions to these difference equations that have the following features: (i) are non-meromoprhic as functions of the Liouville momenta, (ii) are non-reflection symmetric in the momenta, (iii) take a "semi-classical and one-loop" exact form. The last feature will lead us to propose a "quantum modularity" conjecture for these kernels as functions of the central charge. If there is time, we will discuss how these results lead us to prove analytically for the first time that Liouville theory with c < = 1 is modular covariant and crossing symmetric. Based on https://arxiv.org/pdf/2512.03172.

Mardi 10 Mars 2026, 14:00 à LPENS, LPENS Library - E239	LPENS-PH (LPENS Particle physics phenomenology and cosmology)	hep-th
Mehregan Doroudiani	Scattering amplitude of massless closed strings at genus one
Abstract:	Perturbative calculations of string amplitudes are twofold: an expansion in the string coupling (the genus expansion of the worldsheet) and a low-energy expansion in the momenta. In this talk, I will focus on the low-energy expansion of closed string amplitudes at genus one, specifically for four- and five-point massless states of type IIB superstrings in flat spacetime. Evaluating these amplitudes involves integrating over the moduli space of punctured tori. I will demonstrate how the formalism of equivariant iterated Eisenstein integrals can be used to systematically calculate these integrals. Additionally, I will discuss the implications of these results for the S-duality of type IIB.

Mercredi 11 Mars 2026, 11:00 à CPHT, Salle de Conférence Louis Michel	SEM-CPHT (Séminaire du CPHT)	hep-th
Wenqi Ke ( Minnesota University )	From spin-3/2 to supergravity: an on-shell reconstruction
Abstract:	The spin-3/2 field (the gravitino) arises as a consequence of local supersymmetry and appears as the superpartner of the graviton. This raises the converse question: can a consistent spin-3/2 theory lead to supersymmetry, and in turn require the presence of a graviton? Work from the 70s answered this in the affirmative for massless spin-3/2. In this talk, I will address the massive spin-3/2 case using the on-shell formalism, and show that interactions characteristic of spontaneously broken supergravity emerge naturally from consistency conditions such as Lorentz invariance and unitarity.

Mercredi 11 Mars 2026, 13:30 à DPT-PHYS-ENS, ConfIV (E244) - 24 rue Lhomond 75005 PARIS	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Vasiliki Pavlidou ( University of Crete, Institute of Astrophysics, FORTH )	Mapping the Milky Way: how a 3D atlas of our Galactic home can pave the way for new Physics and Astrophysics
Abstract:	More than just our cosmic “you are here” dot, the Milky Way is the environment that gave rise to the solar system, the Earth, and life itself, as well as the lens through which we obsere the Universe at large. Yet, despite being embedded within it, we still know surprisingly little about the true 3D structure of its components, which distort our view of both distant galaxies and of the local astrophysical metabolism. This problem hinders progress for both astrophysics and fundamental physics, as the luminous objects both inside and beyond the Milky Way are the tracers of the dark scaffolding of the cosmos, which lies beyond our standard models of particle physics, gravity, and cosmology. Combining latest and upcoming astronomical data with algorithms drawing from information field theory, our team is creating a self-consistent, uncertainty-aware 3D map of all Galactic components. This atlas can help illuminate key questions in cosmology, in the physics and astrophysics of ultra-high energy cosmic rays, and in the physical and chemical processes taking place throughout the interstellar medium - the arena of the transition from nuclei and atoms to complex prebiotic and transbiotic chemistry.

Mercredi 11 Mars 2026, 14:15 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	hep-th
Franz Ciceri ( ENS Lyon )	A supergravity dual for IKKT holography
Abstract:	A particularly interesting corner of holographic dualities is the correspondence between type II strings on Dp branes geometries and d = p+1 dimensional super Yang-Mills theories with sixteen supercharges. For the extremal case p = -1, this suggests a holographic duality for the IKKT matrix model. Despite intriguing and highly non-trivial results in the IKKT model, this duality has, until recently, received only limited attention. In this talk, I will consider the lowest supermultiplet of gauge invariant operators of the model and identify its states with the lowest Kaluza-Klein fluctuations of Euclidean IIB supergravity on the dual D(-1) instanton background. I will explain how to construct its holographic bulk realisation as a one-dimensional maximal supergravity with local SO(10) invariance, capturing the full non-linear dynamics. By analysing the one-dimensional Killing spinor equations, I will then present several classes of half-supersymmetric solutions that break SO(10), and discuss their ten-dimensional uplifts.

Mercredi 11 Mars 2026, 14:30 à IJCLAB, 100/-1-A900 - Auditorium Joliot Curie (IJCLab) ( https://indico.ijclab.in2p3.fr/event/13489/ )	IJCLAB-HEP (Particle Physics Seminars at IJCLab)	hep-ph
Pierre Vanhove ( IPhT CEA )	Hadronic vacuum polarization to three loops in chiral perturbation theory
Abstract:	In this talk we will report on the analytic evaluation of the hadronic vacuum polarisation in two-flavor chiral perturbation theory to three loops that's relevant for the calculation of the anomalous magnetic moment of the muon and electron. The three-loop amplitude gets contributions from polylogarithms and six elliptic master integrals, all derivable from the single-mass two-point sunset integral via differentiation or integration. Our result is intended to serve as a starting point for phenomenological studies, as well as the computation of finite-volume corrections in lattice QCD. Based on work [arXiv:2510.12885] and work in progress with Laurent Lellouch, Alessandro Lupo, Mattias Sjö and Kálmán Szabo.

Jeudi 12 Mars 2026, 10:00 à IHP, Choquet-Bruhat (bâtiment Perrin)	RENC-THEO (Rencontres Théoriciennes)	hep-th
Oscar Dias ( University of Southampton )	Localised thermal phases in BFSS quantum mechanics
Abstract:	We investigate the low-energy regime of BFSS quantum mechanics using its holographic dual. We identify three distinct thermodynamic phases (black holes) and analyze their thermodynamic properties extensively, including phase transitions amongst the several phases. While the properties of the canonical ensemble aligns with existing conjectures on BFSS thermodynamics, we uncover intriguing and unexpected behavior in the microcanonical ensemble. Specifically, for sufficiently low energies, we observe the dominance of the localized phase. Surprisingly, we also identify an energy range where the non-uniform phase becomes dominant.

Jeudi 12 Mars 2026, 11:30 à IHP, Y. Choquet Bruhat (in bâtiment Perrin)	RENC-THEO (Rencontres Théoriciennes)	hep-th
Piotr Tourkine ( LAPTh Annecy )	Regge trajectories in meromorphic amplitudes, gravity, and polynomial boundedness
Abstract:	In this talk I’ll present a theorem regarding meromorphic amplitudes describing the infinite exchange of stable massive higher-spin particles at tree-level. They appear in several context, as weakly coupled UV-complete S-matrices and particularly explicit amplitudes with non-perturbative flavour. For instance they describe large-N gauge theories and weakly-coupled UV completions in gravity. I will present the results of two papers regarding a no-go theorem showing that such amplitudes must always possess infinitely many Regge trajectories. In 2512.17828, we simplified our 2024 proof by ultimately connecting the tension to causality (polynomial boundedness), and extended it to graviton scattering in d=4. The physical interpretation of the results is clear: from a string’s worldsheet perspective, the sub-leading trajectories represent ripples on the worldsheet, hence our no-go suggests that such meromorphic UV-completions must always be stringy and cannot be frozen to only their leading trajectory. I’ll start the talk by reviewing basics of S-matrix theory and stringy meromorphic amplitudes. I’ll then present the proof in an elementary manner. I’ll finish by presenting some intriguing numerical results showing that extremal meromorphic amplitudes appear to present the emergence of a mysterious composite “sister” trajectory of slope 1/2. This trajectory dominates the amplitude and I’ll speculate how this might be related to recent studies in the literature that found single-trajectory like objects in large-N gauge theories and gravity, in apparent tension with the no-go.

Vendredi 13 Mars 2026, 13:00 à LPENS, E012 (salle des éléments)	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Sophie Bagur ( ESPCI )	Neural population representations of the temporal structure of sounds
Abstract:	The temporal structure of sensory inputs contains essential information for their interpretation. Sensory cortex represents these temporal cues through two codes: the temporal sequences of neuronal activity and the spatial patterns of neuronal firing rate. However, it is unknown which of these coexisting codes causally drives sensory decisions. To separate their contributions, we generated in the mouse auditory cortex optogenetically driven activity patterns differing exclusively along their temporal or spatial dimensions. Mice could rapidly learn to behaviorally discriminate spatial but not temporal patterns. Moreover, large-scale neuronal recordings across the auditory system revealed that the auditory cortex is the first region in which spatial patterns efficiently represent temporal cues on the timescale of several hundred milliseconds. This feature is shared by the deep layers of neural networks categorizing time-varying sounds. Moreover, neural networks allowed to explore the constraints on this process linked to neural architecture Therefore, the emergence of a spatial code for temporal sensory cues is a necessary condition to efficiently associate temporally structured stimuli with decisions.

Lundi 16 Mars 2026, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay)	physics
Eliran Subag	TBA

Mardi 17 Mars 2026, 11:30 à LPTHE, LPTHE library	SEM-LPTHE (Séminaire du LPTHE)	hep-th
Alex Simon ( ENS de Lyon )	The bootstrap approach to integrable quantum field theories in 1+1 dimensions
Abstract:	Quantum field theories (QFTs) provide a very effective framework for describing relativistic quantum systems with an infinite number of degrees of freedom. In particular, their setting allows one to provide expressions for the so-called correlation functions that are directly measured in experiments. However, even though a lot of progress has been made regarding the rigorous constructions of QFTs using various techniques, there are still numerous open questions remaining. In the 60s, Wightman proposed a scheme allowing one to construct a QFT from the knowledge of its correlation functions, satisfying specific properties called Wightman axioms. Since then, multiple approaches have been developed, leading to the constructions of several QFTs in various dimensions. In this talk, I will focus on one approach, based on the integrable bootstrap. This approach, applicable to general integrable quantum field theories in 1+1 dimensions, will be illustrated by the example of the Sinh-Gordon model, which is the simplest of such theories. Using this approach, we managed to derive fully explicit and well-defined expressions for appropriately regularized multi-point correlation fonctions, from which the regular correlation functions can be obtained and satisfy Wightman axioms, assuming some convergence properties. This is a joint work with K. Kozlowski.

Mardi 17 Mars 2026, 11:30 à IHES, Centre de conférences Marilyn et James Simons ( Séminaire Laurent Schwartz EDP et applications )	MATH-IHES (TBA)	math
Taoran He ( IHES )	On Kerr Black Hole Formation With Complete Apparent Horizon and a New Approach Toward Penrose Inequality

Mardi 17 Mars 2026, 14:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	physics
Alessandro Georgoudis	TBA

Mardi 17 Mars 2026, 14:00 à IHES, Centre de conférences Marilyn et James Simons ( Séminaire Laurent Schwartz EDP et applications )	MATH-IHES (TBA)	math
Antoine Gloria ( LJLL )	Kinetic-to-Diffusive Transition for the Discrete Lorentz Gas with Random Scatterers

Mardi 17 Mars 2026, 15:15 à IHES, Centre de conférences Marilyn et James Simons ( Séminaire Laurent Schwartz EDP et applications )	MATH-IHES (TBA)	math
Herbert Koch ( University of Bonn )	Unbounded Solutions to the Two Dimensional Euler Equations

Mercredi 18 Mars 2026, 11:00 à LKB, Institut des civilisations	SEM-LKB (Séminaire du Laboratoire Kastler Brossel)	quant-ph
Christophe Galland ( EPFL, Laboratory of Quantum and Nano-Optics )	Nonlinear optics and sensing at the nanoscale: from plasmonics to diamond photonics
Abstract:	Placing an emitter or a scatterer in a cavity modifies its local photonic environment. It boosts light-matter interaction, which can be used to improve the performance of single-photon sources [1] or to perform nonlinear spectroscopy on individual molecules [2,3]. I will first illustrate how to achieve ultra-broadband photonic engineering using self-assembled plasmonic nanocavities. We realize single-molecule Purcell factors of 10^5 and a giant enhancement of three-wave mixing by 10^12, enabling coherent vibrational spectroscopy at the few-molecule level [4-8]. The second part of the presentation will be devoted to diamond nanophotonics. I will present our platform for realizing suspended single-crystal diamond nanostructures and how it is used in two different contexts: for the study of nanoscale non-diffusive phonon heat transport probed by NV thermometers [9], and for the implementation of cavity-enhanced NV spin readout through the singlet transition absorption measurement at 1’042 nm [10]. References: [1] L. Husel, A., et al. “Cavity-enhanced photon indistinguishability at room temperature and telecom wavelengths.” [Nature Communications 15, 3989 (2024)](https://doi.org/10.1038/s41467-024-48119-1) [2] Schörner, C and Lippitz, M. “Single molecule nonlinearity in a plasmonic waveguide.” [Nano Letters 20, 2152-2156 (2020)](https://doi.org/10.1021/acs.nanolett.0c00196) [3] Maser, A., Gmeiner, B., Utikal, T., Götzinger, S., & Sandoghdar, V. “Few-photon coherent nonlinear optics with a single molecule.” [Nature Photonics, 10, 450-453 (2016)](https://doi.org/10.1038/nphoton.2016.63) [4] Verlekar, S. et al. “Giant Purcell broadening and Lamb shift for DNA-assembled near-infrared quantum emitters”, [ACS Nano 19, 3172–3184 (2025)](https://doi.org/10.1021/acsnano.4c09829) [5] Chen, W. et al. “Continuous-wave frequency upconversion with a molecular optomechanical nanocavity.” [Science 374, 1264-1267 (2021)](https://doi.org/10.1126/science.abk3106) [6] Hu, H. et al. “Plasmonic Nanoparticle-in-nanoslit Antenna as Independently Tunable Dual-Resonant Systems for Efficient Frequency Upconversion” (2025) [preprint: arXiv:2505.10668](https://doi.org/10.48550/arXiv.2505.10668) [7] Moradi Kalarde, F. et al, “Photon antibunching in single-molecule vibrational sum-frequency generation” [Nanophotonics 14, 59-73 (2025)](https://doi.org/10.1515/nanoph-2024-0469) [8] Xie, Z et al. “Continuous-wave, high-resolution, ultra-broadband mid-infrared nonlinear spectroscopy with tunable plasmonic nanocavities” arXiv:2508.12097 [9] Goblot, V. et al. “Imaging heat transport in suspended diamond nanostructures with integrated spin defect thermometers ”arXiv:2411.04065 [10] Zhu, Y. et al. “Fiber-Coupled Diamond Microcavities for Infrared Absorption Readout of NV Centers” CLEO 2025, paper SS114_5

Jeudi 19 Mars 2026, 11:00 à LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th
Viet Dang ( IRMA Strasbourg )	TBA

Jeudi 19 Mars 2026, 14:00 à LPTMC, Jussieu, LPTMC seminar room, towers 13-12, 5th floor, room 523	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Hugues Pothier ( SPEC CEA Saclay )	The Nobel Prize in Physics 2025: Quantum physics with electrical circuits
Abstract:	The Nobel Prize in Physics 2025 was awarded to John Clarke, Michel Devoret and John Martinis “for the discovery of macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit”. I will describe their experiments, which gave birth to the now flourishing domain of quantum electronics.

Vendredi 20 Mars 2026, 10:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires)	physics
Guilherme Pimentel ( SNS Pisa )	Cosmological Correlators: Theory and Phenomenology
Abstract:	Abstract:  All the information we will ever obtain from the early universe is imprinted in the spatial correlations of primordial fluctuations at the hot Big Bang. I will explain how an influx of ideas from various areas of fundamental physics is providing us with new conceptual and practical tools to decode the physics of these primordial fluctuations. A thorough understanding of the fluctuations will give us insight into particle physics at the highest energies and may provide a window into the nature of spacetime itself. In these lectures I will review the current status of the theory and phenomenology of cosmological correlators ? the observable which encodes the statistics of primordial fluctuations. I will give a broad overview of inflationary perturbation theory, the current observational status and future prospects for constraining inflation; Motivate the EFT perspective on primordial fluctuations, and propose ?cosmological collider physics? as a way to probe the UV completion of inflation; Explain the various methods to compute cosmological correlators: the in-in formalism, the wavefunction of the universe, and the cosmological bootstrap; Give a survey of recent theoretical developments that draw inspiration from the scattering amplitude and conformal field theory literature.

Vendredi 20 Mars 2026, 15:00 à IHES, Amphithéâtre Léon Motchane	PT-IHES (Séminaire de physique théorique de l'IHES)	hep-th
Aditya Hebbar ( ICTP, Trieste )	S-Matrix Bounds from the Conformal Bootstrap
Abstract:	Studying quantum field theories (QFTs) in anti-de Sitter (AdS) space naturally leads to boundary correlation functions that satisfy all the axioms of the conformal bootstrap. Upon taking the radius of the AdS space to infinity, one expects to recover flat space physics. We use this idea to extract bounds on the flat space S-matrix by taking the appropriate limit of numerical conformal bootstrap bounds.

Mardi 24 Mars 2026, 11:00 à IPHT, Amphi Claude Bloch, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Hyungjin Kim ( IPhT )	TBA
Abstract:	TBA

Mardi 24 Mars 2026, 14:00 à LPTHE, library ( Based on the works: https://arxiv.org/abs/2512.10015 https://arxiv.org/abs/2401.17365 https://arxiv.org/abs/1912.01725 )	LPTHE-PPH (Particle Physics at LPTHE)	hep-ph
Richard Ruiz ( IFJ PAN, Kraków )	The Many Polarizations of the W
Abstract:	LHC data and phenomenological estimates agree that polarization interference is inherently small for multiboson production at the LHC. In this talk, we show that this could be understood from kinematical arguments and angular momentum conservation, and is a non-trivial consequence of the (near) masslessness of initial- and final-state fermions coupling to intermediate, helicity-polarized weak bosons. Connections to electroweak factorization are discussed. We finish we a brief comment on minor adjustments to LHC search strategies can lead to more robust/stable definitions of polarization across different classes of gauge fixing.

Mercredi 25 Mars 2026, 11:00 à LPENS, L378	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Laura Foini ( IPHT )	TBA

Jeudi 26 Mars 2026, 11:30 à IHP, Choquet-Bruhat	RENC-THEO (Rencontres Théoriciennes)	hep-th
Guilherme Pimentel	TBA

Vendredi 27 Mars 2026, 13:00 à LPENS, E012 (salle des éléments)	ENS-BIOPHYS (ENS Biophysics Seminar)	physics.bio-ph
Jacopo Grilli ( ICTP )	TBA

Mardi 31 Mars 2026, 10:45 à LPTMC, campus Jussieu, couloir 12-13, 5ème étage, salle 5-23	SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)	cond-mat
Benjamin Rotenberg ( PHENIX )	TBA

Mercredi 1 Avril 2026, 11:00 à LPENS, L378	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Clément Hongler ( EPFL )	TBA