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The SEMPARIS seminar webserver hosts annoucements of all seminars taking place in Paris area, in all topics of physics, mathematics and computer science. It allows registered users to receive a selection of announcements by email on a daily or weekly basis, and offers the possibility to archive PDF or Powerpoint files, making it available to the scientific community. [ More information ]
| Upcoming Seminars | [Next 30 ] | |
| [ scheduler view ] | ||
| Tuesday 10 December 2024, 10:45 at 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 |
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| Abstract: | Soliton gases represent infinite random ensembles of interacting solitons displaying nontrivial large-scale behaviours governed by the properties of the elementary two-soliton collisions. The dynamics of non-equilibrium soliton gases in integrable dispersive systems such as the Korteweg-de Vries and nonlinear Schrödinger equations is described by a nonlinear integro-differential kinetic equation for the density of states in the spectral (Lax) phase space. In my talk, I will outline the main ideas of the kinetic theory of soliton gases and its application within the context of integrable turbulence for the Korteweg-de Vries equation. | |
| Tuesday 10 December 2024, 14:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-HEP (Séminaire de physique des particules et de cosmologie) | hep-ph |
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| Abstract: | I will focus on scenarios involving heavy new physics that couples mostly to the third family of Standard Model fermions. After motivating this class of models, I will show what current electroweak, flavor, and collider data can teach us about them. I will also comment on the mid- and long-term prospects for constraining these models, with a focus on the Z-pole run of FCC-ee. | |
| Tuesday 10 December 2024, 14:00 at LPENS, L378, 24 Rue Lhomond | LPTENS-HE (Séminaire commun LPTENS-LPTHE) | hep-th |
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| Abstract: | It has been known that 2-dimensional supersymmetric sigma models admit symmetries generated by covariantly constant forms. For target spaces manifolds M n whose holonomy is included in U(n/2), SU(n/2), Sp(n/4), Sp(n/4) · Sp(1), G2(n = 7) and Spin(7)(n = 8), these symmetries close as a W-algebra. In heterotic sigma models, these symmetries are anomalous due to the presence of chiral worldsheet fermions in the action and must be cancelled to preserve the geometric interpretation of the theory. In this talk, I will consider sigma models with target spaces (10-dimensional) supersymmetric heterotic backgrounds with SU (2) and SU (3) holonomy. I will present the W-algebra generated by the covariantly constant forms of the theory, pointing out that it closes under the inclusion of additional generators which are identified. Requiring the chiral anomalies to satisfy the Wess-Zumino consistency conditions at one-loop in perturbation theory, I will provide their explicit expressions. Finally, I will discuss the cancellation of the anomalies at the same loop level either by adding suitable finite local counterterms in the sigma model effective action or by assuming a plausible quantum correction to the transformations. Based on arXiv:2305.19793 with G. Papadopoulos and E. Perez-Bolanos. | |
| Tuesday 10 December 2024, 14:00 at
LPTHE,
library and zoom link below ( https://cern.zoom.us/j/66414483345?pwd=4BtVql7Nw19hcYkIsHYQ0sLr34YtvQ.1 ) | LPTHE-PPH (Particle Physics at LPTHE) | hep-ph |
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| Abstract: | High-precision test has become the core direction of particle physics research, both now and for the foreseeable future. To achieve this goal, it is essential not only to conduct high-precision measurements experimentally but also to provide accurate theoretical predictions. The main bottleneck in obtaining high-precision theoretical predictions based on perturbative quantum field theory lies in the calculation of multi-loop multi-leg Feynman integrals. Although significant progress has been made in this area in recent years, the existing methods still fail to meet the urgent demands of particle physics experiments, particularly those at high-luminosity LHC. We have conducted long-term research on this issue and recently discovered that multi-loop multi-leg Feynman integrals can be expressed as integrals over a small number of parameters for one-loop-like Feynman integrals, with the number of parameters being 2 for two loops, 5 for three loops, and so on. One-loop-like Feynman integrals, which resemble one-loop Feynman integrals, can be computed in an extremely efficient and systematic manner; the remaining integrals over a small number of parameters can be processed using established methods developed in the study of Feynman integrals. This novel structure of Feynman integrals is expected to completely overcome the computational bottleneck of multi-loop multi-leg Feynman integrals, thus meeting the phenomenological needs of particle physics. | |
| Wednesday 11 December 2024, 11:00 at LKB, Sorbonne Université - 4 places Jussieu 75005 - Amphi Charpak | SEM-LKB (Séminaire du Laboratoire Kastler Brossel) | quant-ph |
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| Abstract: | In classical mechanics, a pendulum with time-modulated parameters serves as a standard example for introducing classical chaos, with the emergence of mixed or fully chaotic stroboscopic phase spaces. In quantum physics, although the Schrödinger equation remains fully linear, the same Hamiltonian enables the study of chaos-assisted tunneling and different regimes of matter wave localization. Experiments in this area require precise control over the initial wave function, and we will first explain how quantum control techniques can address this challenge. We will then present our recent results on quantum chaos, with a focus on multiple matter-wave interference effects related to strong (Anderson) localization. Beyond single-particle physics, we will also discuss the emergence of long-range order resulting from the engineering of Bogolubov instabilities. | |
| Wednesday 11 December 2024, 12:45 at LPENS, 3 rue dUlm, College de France | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Abstract: | Geometrical frustration is a simple yet profound concept in condensed matter physics that can give rise to exotic quantum matters like spin liquid. In this talk, I will propose a new source of geometrical frustration from the orbitals instead of the spins of the electrons. A concrete platform for realizing such orbital geometrical frustration is the twisted bilayer graphene (TBG) at fractional filling, where we can map the configurations of electrons to the tiling patterns of trimers. From this mapping, we can uncover novel charge fractionalization behavior. Furthermore, we find an emergent exact global symmetry, dubbed ``tile-invariant symmetry”. Quantum fluctuation can spontaneously break the tile-invariant symmetry, giving rise to an exotic, gapless Mott insulator. | |
| Wednesday 11 December 2024, 17:00 at
CPHT,
D'ALEMBERT LECTURE HALL, ROOM 1Z18, ENS PARIS-SACLAY ( Attention: unusual place and time! ) | SEM-EXCEP (Seminaire exceptionnel) | cond-mat.other |
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| Abstract: | Nonlinear Schrödinger equations (NLS) are a large class of partial differential equations, including Gross Pitaevskii equations as simple mean-field models of Bose Einstein Condensates. There is a large amount of work by «pure» mathematicians on increasingly refined analysis of NLS (e.g. studies of «blow up», «semi-classical analysis» etc), but few mathematicians tackle things where (experimental) physicists could need their help most: mathematical modeling - numerical methods - computer simulations. We present selected topics in our 15 years of cooperation of mathematicians with the experimental groups at AtomInstitut Wien (Jörg Schmiedmayer, Thorsten Schumm) in the frame of the Wolfgang Pauli Institute, like efficient numerics for the «time of flight» or «Generalized HydroDynamics». We conclude with general remarks on the increasing separation of mathematics from physics at (most) universities. | |
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| Thursday 12 December 2024, 11:00 at LPTHE, Library | SEM-LPTHE (Séminaire du LPTHE) | hep-th |
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| Abstract: | I will first give an introductory review of the concepts of Asymptotically Flat Spacetimes, IR triangle and Noether's theorems. I will then present what Asymptotic Higher Spin Symmetries are and how they were introduced as a candidate for an approximate symmetry of General Relativity and the S-matrix. Next, I'll move on to the recent developments of establishing these symmetries as Noether symmetries and describing how they are canonically and non-linearly realized on the asymptotic gravitational phase space. If time permits, I will discuss how the introduction of dual EOM encapsulates the non-perturbativity of the analysis. Based on 2409.12178 and 2410.15219. | |
| Thursday 12 December 2024, 11:00 at IHES, Amphithéâtre Léon Motchane | MATH-IHES (TBA) | math |
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| Abstract: | The space of finitely additive measures on compact convex bodies (also called convex valuations) is an infinite-dimensional vector space that shares many properties with the cohomology algebra of a compact Kaehler manifold. In particular it is a graded algebra that satisfies a version of Poincaré duality. In a recent work with Jan Kotrbatý (Prague) and Thomas Wannerer (Jena) we prove a version of the mixed hard Lefschetz theorem and mixed Hodge-Riemann relations. The latter can be translated into new higher-order versions of the famous Alexandrov-Fenchel inequality for mixed volumes. The proof combines techniques from differential geometry and functional analysis. | |
| Thursday 12 December 2024, 14:00 at 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 |
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| Abstract: | The study of moiré engineering started with the advent of van der Waals heterostructures, in which stacking 2D layers with different lattice constants leads to a moiré pattern controlling their electronic properties. The field entered a new era when it was found that adjusting the twist between two graphene layers led to strongly-correlated-electron physics [1] and topological effects associated with atomic relaxation [2]. A twist is now routinely used to adjust the properties of 2D materials. I will first discuss the effect of heterostrain where a layer is strained with respect to the other and its strong impact on electronic properties of twisted bilayer graphene near the magic angle [3.4]. I will then discuss a new type of moiré superlattice in bilayer graphene when one layer is biaxially strained with respect to the other—so-called biaxial heterostrain. Scanning tunneling microscopy measurements uncover spiraling electronic states associated with a novel symmetry-breaking atomic reconstruction at small biaxial heterostrain [5]. Atomistic calculations using experimental parameters as inputs reveal that a giant atomic swirl forms around regions of aligned stacking to reduce the mechanical energy of the bilayer. Tight-binding calculations performed on the relaxed structure show that the observed electronic states decorate spiraling domain wall solitons as required by topology. This study establishes biaxial heterostrain as an important parameter to be harnessed for the next step of moiré engineering in van der Waals multilayers. [1] Y.Cao et al. Nature 556 (2018) 43–50 [2] S. Huang et al. Phys. Rev. Lett 121 (2018) 077702 [3] L. Huder et al. Phys. Rev. Lett. 120 (2018) 156405 [3] F. Mesple et al. Phys. Rev. Lett. 127 (2021) 126405 [5] F. Mesple et al. Adv. Mater 35 (2023) 2306312 | |
| Friday 13 December 2024, 11:00 at
IJCLAB,
100/2-A201 - Salle A201 (IJCLab) ( https://indico.ijclab.in2p3.fr/event/11298/ ) | IJCLAB-HEP (Particle Physics Seminars at IJCLab) | hep-ph|hep-th |
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| Abstract: | We investigate a geometric approach to determining the complete set of numerators giving rise to finite Feynman integrals. Our approach proceeds graph by graph, and makes use of the Newton polytope associated to the integral's Symanzik polynomials. It relies on a theorem by Berkesch, Forsgård, and Passare on the convergence of Euler--Mellin integrals, which include Feynman integrals. We conjecture that a necessary in addition to a sufficient condition is that all parameter-space monomials lie in the interior of the polytope. We present an algorithm for finding all finite numerators based on this conjecture. | |
| Monday 16 December 2024, 13:30 at LPENS, U205 | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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| Abstract: | Most Josephson junctions used in superconducting circuits are tunnel junctions, characterized by a thin insulating barrier. In this talk, I will present two alternative approaches for making non-tunnel Josephson junctions, developed at the QCMX lab at École Polytechnique. These innovative designs not only deepen our understanding of the underlying microscopic phenomena but also hold significant promise for advancing quantum information technologies. The first type of junctions involves Superconductor / Carbon Nanotube / Superconductor structures. We have pioneered a novel technique [1] for integrating ultra-clean carbon nanotubes into superconducting circuits. Transport measurements in these junctions reveal hundreds of well-defined Coulomb diamonds, and I will demonstrate the coherent manipulation of a gate- tunable qubit based on this architecture. The second approach focuses on pinhole junctions, where transport is dominated by a few conduction channels with near-unity transmission. This is evidenced by the observation of Multiple Andreev Reflections in the current-voltage characteristics. Harnessing these high-transmission channels could enable the implementation of the highly sought-after cos(2φ) qubit [2]. [1] S. Annabi, et al., arXiV 2405.19192 (accepted in Phys. Rev. App.) [2] W. Smith, et al., npj Quantum Information 6 (2020) | |
| Monday 16 December 2024, 14:00 at LPNHE, Amphi Charpak | LPNHE (Séminaires du LPNHE) | physics |
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| Abstract: | Both weak and strong gravitational lensing have been used to constrain cosmology, via measurements of the clustering parameter S8 with cosmic shear, and measurements of the Hubble parameter H0 and dark energy equation of state w with strong lensing time delays. However, strong lensing images are themselves weakly lensed, and this `weak lensing of strong lensing' has the potential to become a powerful cosmic probe in its own right. In this talk, I will review the so-called line-of-sight formalism which describes the weak lensing of strong lensing, show how the line-of-sight shear escapes from degeneracies with other lens model parameters, and present the first measurement of this quantity in 50 strong gravitational lenses from the SLACS catalogue. | |
| Tuesday 17 December 2024, 10:45 at 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 |
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| Tuesday 17 December 2024, 11:30 at LPTHE, Library | SEM-LPTHE (Séminaire du LPTHE) | hep-th |
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| Tuesday 17 December 2024, 14:00 at IHES, Amphithéâtre Léon Motchane | PT-IHES (Séminaire de physique théorique de l'IHES) | hep-th |
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| Abstract: | I present the results of a new numerical conformal bootstrap study of the 3d Ising CFT involving mixed correlator constraints of the operators σ, ε, and the stress tensor T. These constraints produce new precise determinations of the scaling dimensions (∆σ, ∆ϵ) = (0.518148806(24), 1.41262528(29)) as well as the OPE coefficients involving σ, ε, T. In addition, with the subset of the system only involving the stress tensor, we find universal bounds (i.e. which apply to all local unitary CFTs in 3d) on similar data, as well as hints of universal structures in the space of CFT data. I will also present the variety of methodological and technical challenges that this work entailed which resulted in several improvements and upgrades to the algorithms and software of the numerical bootstrap. This talk is based on 2411.15300 of the same title as well as ongoing work, done in collaboration with Cyuan-Han Chang, Vasiliy Dommes, Alexandre Homrich, Petr Kravchuk, Aike Liu, Matthew S. Mitchell, David Poland, and David Simmons-Duffin. | |
| Wednesday 18 December 2024, 12:00 at
IHES,
Amphithéâtre Léon Motchane ( online talk ) | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Abstract: | A type of BPS q-series, proposed recently as a topological invariant which provides a non-perturbative completion of complex Chern-Simons theory on closed 3- dimensional manifolds, has mathematical definitions based for example on 3D topology, quantum groups and resurgence, and key properties their integrality and behaviour under surgery formulae. These q-series invariants have displayed relations to vertex operator algebras, and structurally, they have intriguing modular properties. Their mathematical formulation is nevertheless quite constrained, relying heavily on certain negative-definite conditions, and much effort has been devoted to extending this definition. This operation is called “going to the other side”, with different interpretations from the physics, vertex algebra, and 3D topology perspectives. I will discuss different approaches to this challenge, in particular through modularity and resurgence, with implications for the related vertex operator algebras. | |
| Wednesday 18 December 2024, 12:45 at LPENS, 3 rue dUlm College de France | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Thursday 19 December 2024, 11:45 at IHP, Grisvard (314) | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Thursday 9 January 2025, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | hep-th |
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| Monday 13 January 2025, 14:00 at LPNHE, Amphi Charpak | LPNHE (Séminaires du LPNHE) | physics |
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| Abstract: | The future TESSERACT experiment will search for individual galactic Dark Matter (DM) particles below down to 10 MeV. Multiple target materials will be used with varying detection strategies to actively reject the so-called low-energy excess and discriminate nuclear recoils against electron recoils. Nowadays, the TESSERACT project encompasses two US-based technologies, namely HeRALD using superfluid helium as a target material, and SPICE using polar crystals (Al2O3 and SiO2) and scintillating crystals such as GaAs. The possibility to host the future TESSERACT experiment at the Modane Underground Laboratory and to add a third French-based cryogenic semiconducting (Ge, Si) detector technology to the TESSERACT payload will be detailed. | |
| Tuesday 14 January 2025, 10:45 at 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 |
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| Tuesday 14 January 2025, 14:00 at LPTHE, Library and Zoom (link in the comments) | LPTHE-PPH (Particle Physics at LPTHE) | hep-ph |
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| Abstract: | TBA | |
| Thursday 16 January 2025, 10:00 at IHP, Grisvard (314) | RENC-THEO (Rencontres Théoriciennes) | hep-th |
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| Thursday 16 January 2025, 14:00 at LPTMC, Jussieu, towers 13-12, 5th floor, room 5-23, LPTMC seminar room | SEM-LPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée) | cond-mat |
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| Abstract: | Over the past 15 years, a dizzying array of noninteracting topological insulator (TI) and topological crystalline insulator (TCI) phases have been theoretically predicted and identified in real materials. While the TI states are well understood, the TCI states – which comprise the majority of topological materials in nature – exhibit more complicated classification groups and boundary states and carry more ambiguous response signatures. For earlier variants of interacting symmetry-protected topological states (SPTs), both the classification and response were clarified through the many-body quantum numbers of the 0D collective excitations bound to crystal and electromagnetic defects, such as magnetic fluxes and monopoles. In particular, when 0D defects exhibit fractionalized quantum numbers, or more generally projective representations of the local many-body symmetry group, this can indicate the presence of quantized responses in the bulk that are governed by long-wavelength topological field theories that are stable to symmetric interactions. In this talk, I will introduce numerical methods for computing defect quantum numbers in stable and fragile TCI states via the reduced density matrix, revealing a deep connection between defect quantum numbers and the entanglement spectrum. Surprisingly, we find that when crystal symmetries are included in the local symmetry group, defects can appear to transform projectively even in Wannierizable (fragile) insulators, casting doubt on the suitability of magnetic monopoles for characterizing the TCI states present in real 3D materials. Our results represent a crucial step towards describing TCIs beyond tight-binding models and frameworks like “higher- order topology,” and facilitate more direct connections between free-fermion TCIs and interacting SPTs. | |
| Thursday 23 January 2025, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | hep-th |
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| Thursday 30 January 2025, 17:00 at 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 |
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| Abstract: | TBA | |
| Thursday 6 February 2025, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | hep-th |
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| Thursday 6 February 2025, 14:00 at 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 |
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| Abstract: | TBA | |
| Monday 10 February 2025, 13:30 at LPENS, U209 | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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