Jeudi 13 Fevrier 2025, 10:00 à IHP, Pierre Grisvard	RENC-THEO (Rencontres Théoriciennes)	hep-th
Simone Giacomelli ( Milano-Bicocca )	TBA

Jeudi 13 Fevrier 2025, 11:00 à IJCLAB, 210/114	IJCLAB-PTH (Particle Theory Seminar of IJCLAB Orsay)	hep-ph
Wenqi Ke ( University of Minnesota )	Recursion relations and on-shell massive amplitudes
Abstract:	As an alternative to Feynman rules, on-shell formalism offers an efficient and elegant way to compute amplitudes with arbitrary numbers of particles. This construction is based on the so-called recursion relations and relies on the choice of the momentum shift. In this talk, I present a momentum shift in the massive on- shell formalism, which allows us to construct recursively amplitudes in QED, electroweak and supergravity theories. This momentum shift is then applied to examples of $e^+e^-$, $W^+W^-$ and gravitino scatterings. One recovers the Higgs and super-Higgs mechanisms from an on-shell perspective. Finally, some future directions on higher spin Compton scatterings will be outlined.

Jeudi 13 Fevrier 2025, 11:00 à IHES, Amphithéâtre Léon Motchane ( Séminaire de Géométrie Arithmétique )	MATH-IHES (TBA)	math
Takumi Watanabe ( Université de Tokyo & IHES )	On the (phi, Gamma)-modules Corresponding to Crystalline Representations, Semi-stable Representations and de Rham Representations
Abstract:	From the 1980s to the 1990s, Jean-Marc Fontaine introduced the theory of (phi, Gamma)-modules to study p-adic Galois representations. They are simpler than p-adic Galois representations, but he showed an equivalence between them. Among p-adic Galois representations, some classes are particularly important in number theory. Main examples are crystalline representations, semi-stable representations and de Rham representations. In this talk, I will explain how we can determine the (phi, Gamma)-modules corresponding to these representations. These results can be seen, in a sense, as generalizations of Wach modules.

Jeudi 13 Fevrier 2025, 14:00 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
Nicolas Regnault ( Flatiron institute )	Engineering quantum phases of matter through moire materials: The case of Fractional Chern insulators
Abstract:	Progress in stacking two dimensional materials, such as graphene or transition metal dichalcogenides (TMDs), has paved the way to engineer new structures relying on moire patterns. These patterns induced for example by slightly twisting one layer compared to the other, could lead to strongly correlated quantum phases such as superconductivity or the quantum anomalous Hall effects. In the realm of condensed matter physics, the fractional quantum Hall effect stands as a singular experimental manifestation of topological order, characterized by the presence of anyons—quasiparticles that bear fractional charge and exhibit exchange statistics diverging from conventional fermions and bosons. This phenomenon, observed over four decades ago, was still missing the direct observation of similar topological orders arising purely from band structure—without the application of strong magnetic fields. In 2023 within the span of a few months, several pioneering experiments have illuminated this once theoretical domain. Studies on twisted homobilayer MoTe2 and pentalayer rhombohedral graphene placed on hBN have finally unveiled the existence of fractional Chern insulators (FCIs), the zero-magnetic field analog of fractional quantum Hall states. The journey to this point, preceded by over a decade of theoretical frameworks and predictions surrounding FCIs, yet the experimental revelations have proved to be richer and more surprising than expected. In this talk, we will present how the combination of ab-initio and quantum many-body calculations can help us capture the different features observed in experiments. We will discuss the potential future for this exciting booming field, including the possible observation of fractional topological insulators, a yet-never observed topological ordered phase preserving the time reversal symmetry.

Mardi 18 Fevrier 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Dustin Clausen ( IHES )	Algebraic K-theory and Chromatic Homotopy Theory (1/4)
Abstract:	The most universal kind of linear algebra is based not on abelian groups, but on homotopy-theoretic objects known as spectra. According to chromatic homotopy theory, one can systematically organize spectra into periodic families. On the other hand, a natural source of spectra is provided by algebraic K-theory, a highly refined cohomological invariant of rings (or schemes, etc). This leads to the subject of this course: the interaction of the chromatic theory with algebraic K-theory. The story begins with classical theorems of Thomason, Mitchell, and Hesselholt-Madsen. Bold generalizations of these theorems were conjectured by Rognes and Ausoni-Rognes, under the umbrella term of "redshift". Several of these conjectures are now theorems due to recent work of many people. Remarkably, this work has applications to "pure" chromatic homotopy theory: Burklund-Hahn-Levy-Schlank used it to settle (in the negative) the "telescope conjecture", the last of Ravenel's conjectures. Lecture 1: Introduction to chromatic homotopy theory. Lecture 2: Descent and "soft redshift". Lecture 3: "Hard redshift", a.k.a. the Lichtenbaum-Quillen property. Lecture 4: The telescope conjecture.

Jeudi 20 Fevrier 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Dustin Clausen ( IHES )	Algebraic K-theory and Chromatic Homotopy Theory (2/4)
Abstract:	The most universal kind of linear algebra is based not on abelian groups, but on homotopy-theoretic objects known as spectra. According to chromatic homotopy theory, one can systematically organize spectra into periodic families. On the other hand, a natural source of spectra is provided by algebraic K-theory, a highly refined cohomological invariant of rings (or schemes, etc). This leads to the subject of this course: the interaction of the chromatic theory with algebraic K-theory. The story begins with classical theorems of Thomason, Mitchell, and Hesselholt-Madsen. Bold generalizations of these theorems were conjectured by Rognes and Ausoni-Rognes, under the umbrella term of "redshift". Several of these conjectures are now theorems due to recent work of many people. Remarkably, this work has applications to "pure" chromatic homotopy theory: Burklund-Hahn-Levy-Schlank used it to settle (in the negative) the "telescope conjecture", the last of Ravenel's conjectures. Lecture 1: Introduction to chromatic homotopy theory. Lecture 2: Descent and "soft redshift". Lecture 3: "Hard redshift", a.k.a. the Lichtenbaum-Quillen property. Lecture 4: The telescope conjecture.

Jeudi 20 Fevrier 2025, 11:00 à IJCLAB, 210/114	IJCLAB-PTH (Particle Theory Seminar of IJCLAB Orsay)	hep-ph
Rafael Aoude ( University of Edinburgh )	Amplitudes for Hawking Radiation
Abstract:	In this talk, I will show a new approach to compute Hawking radiation based on on-shell scattering amplitudes. The Hawking spectrum is obtained by exponentiating a series of Feynman diagrams describing a massless scalar field scattering through a collapse background. Using semiclassical methods, we obtain a generalized an in-in generalisation of an amplitude closely connected to the Bogoliubov coefficients. Finally, I will show how subdominant one-loop correction can be interpreted as finite-size corrections sensitive to the radius of the black hole.

Jeudi 20 Fevrier 2025, 11:00 à LPTHE, LPTHE library	SEM-LPTHE (Séminaire du LPTHE)	cond-mat.str-el
Clément Delcamp ( IHES )	TBA

Mardi 25 Fevrier 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Dustin Clausen ( IHES )	Algebraic K-theory and Chromatic Homotopy Theory (3/4)
Abstract:	The most universal kind of linear algebra is based not on abelian groups, but on homotopy-theoretic objects known as spectra. According to chromatic homotopy theory, one can systematically organize spectra into periodic families. On the other hand, a natural source of spectra is provided by algebraic K-theory, a highly refined cohomological invariant of rings (or schemes, etc). This leads to the subject of this course: the interaction of the chromatic theory with algebraic K-theory. The story begins with classical theorems of Thomason, Mitchell, and Hesselholt-Madsen. Bold generalizations of these theorems were conjectured by Rognes and Ausoni-Rognes, under the umbrella term of "redshift". Several of these conjectures are now theorems due to recent work of many people. Remarkably, this work has applications to "pure" chromatic homotopy theory: Burklund-Hahn-Levy-Schlank used it to settle (in the negative) the "telescope conjecture", the last of Ravenel's conjectures. Lecture 1: Introduction to chromatic homotopy theory. Lecture 2: Descent and "soft redshift". Lecture 3: "Hard redshift", a.k.a. the Lichtenbaum-Quillen property. Lecture 4: The telescope conjecture.

Mardi 25 Fevrier 2025, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Julio Parra-Martinez ( IHES )	Black-hole tides, running and matching
Abstract:	Tidal Love numbers quantify the finite-size properties of compact objects, such as absorption and their response to external fields. Perhaps surprisingly, even in classical general relativity, they undergo renormalization group running due to nonlinearities. In this talk I will explain some exact results about their running, which can be extracted using black-hole perturbation theory and point-particle effective theories (EFT). Due to the universality of the EFT, the results have applications to the physics of black holes, neutron stars, binaries and their signals in gravitational wave observatories. Our calculations can also provide the precise values of both static and dynamical Love numbers of black holes in various dimensions.

Jeudi 27 Fevrier 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Dustin Clausen ( IHES )	Algebraic K-theory and Chromatic Homotopy Theory (4/4)
Abstract:	The most universal kind of linear algebra is based not on abelian groups, but on homotopy-theoretic objects known as spectra. According to chromatic homotopy theory, one can systematically organize spectra into periodic families. On the other hand, a natural source of spectra is provided by algebraic K-theory, a highly refined cohomological invariant of rings (or schemes, etc). This leads to the subject of this course: the interaction of the chromatic theory with algebraic K-theory. The story begins with classical theorems of Thomason, Mitchell, and Hesselholt-Madsen. Bold generalizations of these theorems were conjectured by Rognes and Ausoni-Rognes, under the umbrella term of "redshift". Several of these conjectures are now theorems due to recent work of many people. Remarkably, this work has applications to "pure" chromatic homotopy theory: Burklund-Hahn-Levy-Schlank used it to settle (in the negative) the "telescope conjecture", the last of Ravenel's conjectures. Lecture 1: Introduction to chromatic homotopy theory. Lecture 2: Descent and "soft redshift". Lecture 3: "Hard redshift", a.k.a. the Lichtenbaum-Quillen property. Lecture 4: The telescope conjecture.

Mercredi 5 Mars 2025, 14:00 à LPENS, L378	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Felix Werner ( LKB )	TBA

Jeudi 6 Mars 2025, 11:00 à LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th
Sofia Tarricone ( IMJ-PRG )	TBA

Mercredi 12 Mars 2025, 13:30 à DPT-PHYS-ENS, salle ConfIV (Département de Physique de l'ENS - 24 rue Lhomond 75005 PARIS)	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Geoffrey Vallis	TBA
Abstract:	TBA

Mercredi 19 Mars 2025, 12:45 à LPENS, 3 rue dUlm (College de France)	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Dalimil Mazac ( IPHT )	TBA

Mardi 25 Mars 2025, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Per Berglund ( University of New Hampshire )	TBA

Jeudi 27 Mars 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Misha Gromov ( IHES )	Mathematical Description of Biological Structures (1/4)
Abstract:	We shall try to assign mathematical meaning to the language used by biologists for describing basic structures and processes in living organisms, from the (sub)cellular level up to evolutionary dynamics of populations. In particular, we shall elucidate the mathematical as well as biological meaning of the following concepts. - biological (non-Shannon) information, - descriptional (non-Kolmogorov) complexity, - biological structure, - biological function (performed by a particular structure), - biological purpose (of a function), - information/program encoded and stored by a material structure (DNA, RNA), - information/signal transmitted by a matter/energy process/flow, - information/program, which controls such a "flow", - biological structures build by (networks of) matter/energy flows, e.g transcription --> translation --> protein folding. Also we indicate a potential use of formalisation of biological language in genetic engineering, e.g. in the analysis/applications of CRISPR and of phage assisted continuous evolution.

Jeudi 27 Mars 2025, 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
Tarik Yefsah ( LKB )	TBA
Abstract:	TBA

Jeudi 27 Mars 2025, 17:00 à UFR-PHYS-SU, Amphi 25 Campus Pierre-et-Marie-Curie, Jussieu	CPMC (Colloquium Pierre et Marie Curie)	astro-ph|cond-mat|gr-qc|hep-ex|hep-lat|hep-ph|hep-th|physics|quant-ph
Lydéric Bocquet ( LPENS, Académie des Sciences )	La mécanique moléculaire des fluides
Abstract:	TBA

Mercredi 2 Avril 2025, 13:30 à DPT-PHYS-ENS, salle ConfIV (Département de Physique de l'ENS - 24 rue Lhomond 75005 PARIS)	COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS)	physics
Susana Huelga	TBA
Abstract:	TBA

Jeudi 3 Avril 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Misha Gromov ( IHES )	Mathematical Description of Biological Structures (2/4)
Abstract:	We shall try to assign mathematical meaning to the language used by biologists for describing basic structures and processes in living organisms, from the (sub)cellular level up to evolutionary dynamics of populations. In particular, we shall elucidate the mathematical as well as biological meaning of the following concepts. - biological (non-Shannon) information, - descriptional (non-Kolmogorov) complexity, - biological structure, - biological function (performed by a particular structure), - biological purpose (of a function), - information/program encoded and stored by a material structure (DNA, RNA), - information/signal transmitted by a matter/energy process/flow, - information/program, which controls such a "flow", - biological structures build by (networks of) matter/energy flows, e.g transcription --> translation --> protein folding. Also we indicate a potential use of formalisation of biological language in genetic engineering, e.g. in the analysis/applications of CRISPR and of phage assisted continuous evolution.

Jeudi 3 Avril 2025, 11:00 à LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage	SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques)	hep-th
Stavros Garoufalidis ( Shenzen University )	TBA

Vendredi 4 Avril 2025, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Daniel Tataru ( UC Berkeley )	Global Solutions for Nonlinear Dispersive Waves (1/4)
Abstract:	The key property of linear dispersive flows is that waves with different frequencies travel with different group velocities, which leads to the phenomena of dispersive decay. Nonlinear dispersive flows also allow for interactions of linear waves, and their long time behavior is determined by the balance of linear dispersion on one hand, and nonlinear effects on the other hand. The first goal of these lectures will be to present and motivate a new set of conjectures which aim to describe the global well-posedness and the dispersive properties of solutions in the most difficult case when the nonlinear effects are dominant, assuming only small initial data. This covers many interesting physical models, yet, as recently as a few years ago, there was no clue even as to what one might reasonably expect. The second objective of the lectures will be to describe some very recent results in this direction, in joint work with my collaborator Mihaela Ifrim from University of Wisconsin, Madison.

Lundi 7 Avril 2025, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Daniel Tataru ( UC Berkeley )	Global Solutions for Nonlinear Dispersive Waves (2/4)
Abstract:	The key property of linear dispersive flows is that waves with different frequencies travel with different group velocities, which leads to the phenomena of dispersive decay. Nonlinear dispersive flows also allow for interactions of linear waves, and their long time behavior is determined by the balance of linear dispersion on one hand, and nonlinear effects on the other hand. The first goal of these lectures will be to present and motivate a new set of conjectures which aim to describe the global well-posedness and the dispersive properties of solutions in the most difficult case when the nonlinear effects are dominant, assuming only small initial data. This covers many interesting physical models, yet, as recently as a few years ago, there was no clue even as to what one might reasonably expect. The second objective of the lectures will be to describe some very recent results in this direction, in joint work with my collaborator Mihaela Ifrim from University of Wisconsin, Madison.

Lundi 7 Avril 2025, 14:00 à LPENS, TBD	LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS)	cond-mat
Akashdeep Kamra ( RPTU Kaiserlautern )	TBA

Mardi 8 Avril 2025, 11:00 à IPHT, Salle Claude Itzykson, Bât. 774	IPHT-GEN (Séminaire général du SPhT)
Paolo Di Vecchia ( Niels Bohr Institute and Nordita )	TBA

Mercredi 9 Avril 2025, 14:00 à LPENS, 3 rue dUlm (College de France)	FORUM-ENS (Forum de Physique Statistique @ ENS)	cond-mat.stat-mech
Marylou Gabrie ( LPENS )	TBA

Mercredi 9 Avril 2025, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Daniel Tataru ( UC Berkeley )	Global Solutions for Nonlinear Dispersive Waves (3/4)
Abstract:	The key property of linear dispersive flows is that waves with different frequencies travel with different group velocities, which leads to the phenomena of dispersive decay. Nonlinear dispersive flows also allow for interactions of linear waves, and their long time behavior is determined by the balance of linear dispersion on one hand, and nonlinear effects on the other hand. The first goal of these lectures will be to present and motivate a new set of conjectures which aim to describe the global well-posedness and the dispersive properties of solutions in the most difficult case when the nonlinear effects are dominant, assuming only small initial data. This covers many interesting physical models, yet, as recently as a few years ago, there was no clue even as to what one might reasonably expect. The second objective of the lectures will be to describe some very recent results in this direction, in joint work with my collaborator Mihaela Ifrim from University of Wisconsin, Madison.

Jeudi 10 Avril 2025, 10:30 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Misha Gromov ( IHES )	Mathematical Description of Biological Structures (3/4)
Abstract:	We shall try to assign mathematical meaning to the language used by biologists for describing basic structures and processes in living organisms, from the (sub)cellular level up to evolutionary dynamics of populations. In particular, we shall elucidate the mathematical as well as biological meaning of the following concepts. - biological (non-Shannon) information, - descriptional (non-Kolmogorov) complexity, - biological structure, - biological function (performed by a particular structure), - biological purpose (of a function), - information/program encoded and stored by a material structure (DNA, RNA), - information/signal transmitted by a matter/energy process/flow, - information/program, which controls such a "flow", - biological structures build by (networks of) matter/energy flows, e.g transcription --> translation --> protein folding. Also we indicate a potential use of formalisation of biological language in genetic engineering, e.g. in the analysis/applications of CRISPR and of phage assisted continuous evolution.

Vendredi 11 Avril 2025, 14:00 à IHES, Amphithéâtre Léon Motchane ( Cours de l'IHES )	MATH-IHES (TBA)	math
Daniel Tataru ( UC Berkeley )	Global Solutions for Nonlinear Dispersive Waves (4/4)
Abstract:	The key property of linear dispersive flows is that waves with different frequencies travel with different group velocities, which leads to the phenomena of dispersive decay. Nonlinear dispersive flows also allow for interactions of linear waves, and their long time behavior is determined by the balance of linear dispersion on one hand, and nonlinear effects on the other hand. The first goal of these lectures will be to present and motivate a new set of conjectures which aim to describe the global well-posedness and the dispersive properties of solutions in the most difficult case when the nonlinear effects are dominant, assuming only small initial data. This covers many interesting physical models, yet, as recently as a few years ago, there was no clue even as to what one might reasonably expect. The second objective of the lectures will be to describe some very recent results in this direction, in joint work with my collaborator Mihaela Ifrim from University of Wisconsin, Madison.