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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 | ||
| [ scheduler view ] | ||
| Tuesday 21 May 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Tuesday 21 May 2024, 11:00 at IHES, Centre de conférences Marilyn et James Simons | MATH-IHES (TBA) | math |
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| Tuesday 21 May 2024, 13:30 at IHES, Centre de conférences Marilyn et James Simons | MATH-IHES (TBA) | math |
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| Tuesday 21 May 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: | By tracking the arrival times of radio pulses from a collection of pulsars in the Milky Way, several pulsar timing array collaborations have found evidence for a background of gravitational waves permeating our galaxy. In this talk, I will present this evidence, review possible cosmological and astrophysical interpretations of the signal, and discuss ways to discriminate between them. | |
| Wednesday 22 May 2024, 11:00 at LKB, Amphi Budé – Collège de France – 11 Place Marcelin Berthelot – 75005 | SEM-LKB (Séminaire du Laboratoire Kastler Brossel) | quant-ph |
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| Abstract: | Topological phases of matter can be generated in cold-atom systems using periodic driving, also known as Floquet engineering. While conventional topological insulators exhibit exotic gapless edge or surface states, as a result of nontrivial bulk topological properties. In periodically-driven systems the bulk-boundary correspondence is fundamentally modified and knowledge about conventional bulk topological invariants is insufficient. While ultracold atoms provide excellent settings for clean realizations of Floquet protocols, the observation of real-space edge modes has so far remained elusive. Here, I report on recent results, where we have demonstrated an experimental protocol for realizing chiral edge modes in optical lattices, by creating a topological interface in the form of a potential step using a programmable optical potential. We efficiently prepared particles in chiral edge modes in three distinct Floquet topological regimes that are realized in a periodically-driven honeycomb lattice. Moreover, the properties of the edge mode can be modified by controlling the height and sharpness of the potential step. In addition, I will present preliminary results on the interplay between disorder and topology and show how quantum gas microscopy can be used to measure observables that go beyond the detection of on-site occupations, such as local currents which is indispensable for detecting complex topological many-body states with equilibrium currents, such as strongly-interacting Meissner-like phases in optical ladders with artificial magnetic flux. | |
| Wednesday 22 May 2024, 12:45 at LPENS, 3 rue d'Ulm | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Abstract: | At the mesoscopic scale, the equilibrium dynamics of a system are typically modeled as reversible and Markovian, preserving the Boltzmann measure. The macroscopic properties of the system are fully described by ensemble averages following this measure and they can be estimated by time expectations along a carefully chosen Markov processes. Designing efficient Markovian dynamics leaving invariant some target distribution comes down to finding how to design a global structure of probability flows from local information. In the general case, this is made possible by breaking the time-reversal symmetry of the usual detailed-balance dynamics. This presentation will discuss a collection of works pertaining to non-reversible Markov processes and explore the interplay between the invariance of the stationary probability distribution and certain key symmetries. These key symmetries now serve as the basis for necessary probability flow conservation, having replaced the time-reversal symmetry that is now broken. Notably, these investigations span both equilibrium and non- equilibrium systems. It is indeed possible to define the universality classes of some active particle systems based on the satisfaction or not of some skew-detailed symmetry. Interestingly, this reflection extends to reversible cluster algorithms as well, as it revolves around the same core concept of phase space extension. In such algorithms, the flip involutive symmetry plays a crucial role in ensuring correctness, and can be mapped to the conservation of random currents in the flow or loop graphical representation. | |
| Wednesday 22 May 2024, 14:00 at IJCLAB, 210/1-114 - Salle des Séminaires (IJCLab) | IJCLAB-COSM (Seminar of the Gravity and cosmology group of IJCLAB) | gr-qc |
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| Abstract: | Post-Newtonian (PN) theory for inspiraling compact binary systems has been extremely successful in generating waveforms in general relativity (GR). However, if we are interested in testing GR, it would be very useful to have a bank of waveform templates for alternative theories of gravity as well. This program has already begun in a class of massless scalar-tensor theories (equivalent to DEF gravity), which is arguably one of the simplest alternative to GR. Previously, the equations of motion have been computed up to 3PN order [1-3], and the orbital phase has been computed for circular orbits up to 2.5PN beyond the leading dipolar order [4-7]. With the objective of widening the parameter space modeled, I will present in this talk recent advances for the case of elliptic orbits. First, I will present the post-Keplerian parametrization for quasielliptic motion up to 2PN order in scalar-tensor theories [8], and discuss how this can straightforwardly be adapted to other theories. I will show how this easily leads to obtaining the gravitational waveform at 1PN relative order for eccentric orbits [8]. Then, I will present ongoing work [9] aiming at increasing the accuracy of the waveform model. I will focus on the computation of the flux (radiated at infinity) of energy and angular momentum up to 2.5PN order, relatively to the leading dipolar radiation. These quantities exhibit a number of new difficulties, among which the presence of tails and memory contributions. Finally, I will discuss how to combine the post-Keplerian parametrization and these fluxes to deduce the secular evolution of the orbital parameters (e.g. the semimajor axis and eccentricity) through 2.5PN order. These physically correspond to the (modulated) chirp in the waveform frequency, which is a key observable for gravitational wave detectors. [1] Mirshekari and Will, Phys. Rev. D 87, 084070 (2013), arXiv:1301.4680 [2] Bernard, Phys. Rev. D 98, 044004 (2018), arXiv:1802.10201 [2] Bernard, Phys. Rev. D 99, 044047 (2019), arXiv:1812.04169\\ [4] Lang, Phys. Rev. D 89, 084014 (2014), arXiv:1310.3320 [5] Lang, Phys. Rev. D 91, 084027 (2015), arXiv:1411.3073 [6] Sennett, Marsat and Buonanno, Phys.Rev.D 94, 084003 (2016), arXiv:1607.01420 [7] Bernard, Blanchet and Trestini, JCAP 08, 008 (2022), arXiv:2201.10924 [8] Trestini, Phys. Rev. D 109, 104003 (2024), arXiv:2401.06844 [9] Trestini (2024), in preparation | |
| Thursday 23 May 2024, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage | SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) | hep-th|math.DG |
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| Abstract: | In the last 50 years the study of the Monge-Ampère operator has played a central role in order to solve geometric problems, such as the existence of special metrics (e.g. Kähler-Einstein, cscK) on a compact Kähler manifold. In this talk I am going to present some recent developments in “singular” settings: we will work with a singular variety and we look for singular metrics. The talk is based on a series of joint papers with Támas Darvas and Chinh Lu. | |
| Thursday 23 May 2024, 14:00 at
LPTMC,
LPTMC seminar room, Jussieu, towers 12-13, 5th floor, room 523 ( [11] A.Jouan et al. Nature Elec. 3, 201–206 (2020). ) | SEM-EXCEP (Seminaire exceptionnel) | cond-mat |
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| Abstract: | [For the full abstract see the attached pdf]. A key feature of these electronic systems lies in the possibility to control their carrier density by electric field effect, which results in gate-tunability of both superconductivity and Rashba spin-orbit coupling. In this talk, I will review complementary dc and microwave transport measurements conducted on SrTiO3 and KTaO3-based interfaces employing both back-gate and top-gate configurations. I will discuss, in particular, gate-induced multigap superconductivity [8,9] and the role of phase fluctuations within the Berezinskii-Kosterlitz-Thouless model [10]. I will also present the realization of field effect devices whose physical properties, including superconductivity and Rashba spin-orbit coupling, can be tuned over a wide range of electrostatic doping, and discuss the potential of oxides interfaces for the realization of mesoscopic devices [11]. | |
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| Friday 24 May 2024, 11:00 at
IJCLAB,
100/2-A201 - Salle A201 (IJCLab) ( https://indico.ijclab.in2p3.fr/event/10664/ ) | IJCLAB-HEP (Particle Physics Seminars at IJCLab) | hep-ph|hep-th |
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| Abstract: | In this seminar, I will discuss the general strategy employed to extract collinear parton distribution functions (PDFs) from experimental data. In particular, I will discuss the different ingredients that enter a PDF determination, including theoretical and experimental inputs and methodological aspects and highlighting the most common choices. I will finally examine more in depth the question of accounting for theoretical uncertainties in a PDF determination. | |
| Monday 27 May 2024, 13:30 at LPENS, U209 (29 rue d'Ulm) | LPENS-MDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS) | cond-mat |
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| Tuesday 28 May 2024, 11:00 at LPTMS, LPTMS | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Wednesday 29 May 2024, 11:00 at LKB, Amphi Budé – Collège de France – 11 Place Marcelin Berthelot – 75005 | SEM-LKB (Séminaire du Laboratoire Kastler Brossel) | quant-ph |
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| Abstract: | This talk will present recent progress in realizing and detecting fractional quantum Hall (FQH) states in quantum simulators, setting the focus on ultracold atoms in optical lattices. I will start by describing the state of the art, introducing key theoretical notions and reporting on recent experimental results. I will then present several methods for extracting topological signatures in these settings, both in the bulk and on the edge of the FQH droplet. I will also discuss different preparation schemes, introducing a patchwork construction for growing FQH states and an open-system approach dubbed ‘cold-atom elevator’. While directly relevant to cold atoms, the ideas and results presented in this talk could have implications for a broad class of quantum settings. | |
| Wednesday 29 May 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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| Wednesday 29 May 2024, 15:00 at IMO, Online-only. Zoom link by subscribing at https://seedseminar.apps.math.cnrs.fr/ | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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| Thursday 30 May 2024, 15:00 at LPENS, E239 | LPENS-PH (LPENS Particle physics phenomenology and cosmology) | hep-ph |
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| Abstract: | The Bödeker-Moore thermal friction is usually used to determine whether or not a bubble wall can run away. However, the friction on the wall is not necessarily a monotonous function of the wall velocity and could have a maximum before it reaches the Bödeker-Moore limit. In this paper, we compare the maximal hydrodynamic obstruction, a frictional force that exists in local thermal equilibrium, and the Bödeker-Moore thermal friction. We study the former in a fully analytical way, clarifying its physical origin and providing a simple expression for its corresponding critical phase transition strength above which the driving force cannot be balanced out by the maximal hydrodynamic obstruction. We find that for large parameter space, the maximal hydrodynamic obstruction is larger than the Bödeker-Moore thermal friction, indicating that the conventional criterion for the runaway behavior of the bubble wall may have to be modified. We also explain how to apply efficiently the modified criterion to particle physics models and discuss possible limitations of the analysis carried out in this paper. (based on 2401.05911 ) | |
| Monday 3 June 2024, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-STA (Séminaire de Physique Statistique, CEA/Saclay) | cond-mat |
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| Abstract: | TBA | |
| Tuesday 4 June 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Tuesday 4 June 2024, 14:00 at IHES, Amphithéâtre Léon Motchane | PT-IHES (Séminaire de physique théorique de l'IHES) | hep-th |
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| Abstract: | We use holography to study the large spin J limit of the spectrum of low energy states with charge Q under a U(1) conserved current in CFTs in d>2 dimensions, with a focus on d=3 and d=4. For Q=2, the spectrum of such states is known to be universal and properly captured by the long-distance limit of holographic theories, regardless of whether the CFT itself is holographic. We study in detail the holographic description of such states at Q>2, by considering the contribution to the energies of Q scalar particles coming from single photon and graviton exchange in the bulk of AdS; in some cases, scalar exchange and bulk contact terms are also included. For a range of finite values of Q and J, we numerically diagonalize the Hamiltonian for such states and examine the resulting spectrum and wavefunctions as a function of the dimension Δ of the charge-one operator and the central charges cT, cJ of the stress tensor and U(1) current, finding multiple regions in parameter space with qualitatively different behavior. We discuss the extension of these results to the regime of parametrically large charge Q, as well as to what extent such results are expected to hold universally, beyond the limit of holographic CFTs. We compare our holographic computations to results from the conformal bootstrap for the 3d O(2) model at Q=3 and Q=4 and find excellent agreement. | |
| Wednesday 5 June 2024, 11:00 at LKB, Amphi Budé – Collège de France – 11 Place Marcelin Berthelot – 75005 | SEM-LKB (Séminaire du Laboratoire Kastler Brossel) | quant-ph |
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| Abstract: | In three-dimensional space, elementary particles are divided between fermions and bosons according to the properties of symmetry of the wave function describing the state of the system when two particles are exchanged. When exchanging two fermions, the wave function acquires a phase. On the other hand, in the case of bosons, this phase is zero, . This difference leads to deeply distinct collective behaviors between fermions, which tend to exclude themselves, and bosons which tend to bunch together. The situation is different in two-dimensional systems which can host exotic quasiparticles, called anyons, which obey intermediate quantum statistics characterized by a phase varying between and [1,2]. For example in the fractional quantum Hall regime, obtained by applying a strong magnetic field perpendicular to a two-dimensional electron gas, elementary excitations carry a fractional charge [3,4] and have been predicted to obey fractional statistics [1,2] with an exchange phase (where is an odd integer). Using metallic gates deposited on top of the electron gas, beam-splitters of anyon beams can be implemented. I will present how the fractional statistics of anyons can be revealed in collider geometries, where anyon sources are placed at the input of a beam-splitter [5,6,7]. The partitioning of anyon beams is characterized by the formation of packets of anyons at the splitter output. This results in the observation of strong negative correlations of the electrical current, which value is governed by the anyon fractional exchange phase [5,8]. [1] B. I. Halperin, Phys. Rev. Lett. 52, 1583–1586 (1984). [2] D. Arovas, J. R. Schrieffer, F. Wilczek, Phys. Rev. Lett. 53, 722–723 (1984). [3] R. de Picciotto et al., Nature 389, 162–164 (1997). [4] L. Saminadayar, D. C. Glattli, Y. Jin, B. Etienne, Phys. Rev. Lett. 79, 2526–2529 (1997) [5] B. Rosenow, I. P. Levkivskyi, B. I. Halperin, Phys. Rev. Lett. 116, 156802 (2016). [6] H. Bartolomei et al. Science 368, 173-177 (2020). [7] M. Ruelle et al., Phys. Rev. X 13, 011031 (2023). [8] Lee, JY.M., Sim, HS, Nature Communications 13, 6660 (2022). | |
| Wednesday 5 June 2024, 12:45 at LPENS, 3 rue d'Ulm | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Abstract: | TBA | |
| Wednesday 5 June 2024, 13:30 at DPT-PHYS-ENS, ConfIV (E244) - Dépt de Physique de l'ENS - 24 rue Lhomond 75005 PARIS | COLLOQUIUM-ENS (Colloquium of the Physics Department of ENS) | physics |
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| Abstract: | The presence of a supermassive compact object was envisaged fairly quickly after the detection of the radio source Sagittarius A* at the centre of the Milky Way in 1974. Confirmation of this hypothesis took several decades, thanks in particular to the development of high angular resolution techniques at optical wavelengths. The precise measurement of the orbit of the star S2, notably with the VLTI's GRAVITY interferometer, made it possible to carry out tests of general relativity, the results of which proved compatible with the hypothesis of a supermassive black hole. The measurement of heated plasma orbits close to Sgr A*, also by GRAVITY, made it possible to establish a maximum size for the central object that is also compatible with the black hole hypothesis, in agreement with the image made later by the Event Horizon Telescope at 1.3 mm wavelength. I will come back to these results during the seminar and describe the measurements currently underway and those to come in order to continue the tests of general relativity in the strong field regime and the test of the supermassive black hole hypothesis. | |
| Tuesday 11 June 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS, bâtiment Pascal n°530 | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Wednesday 12 June 2024, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) | hep-th |
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| Abstract: | TBD | |
| Wednesday 19 June 2024, 12:45 at LPENS, 3 rue dUlm | FORUM-ENS (Forum de Physique Statistique @ ENS) | cond-mat.stat-mech |
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| Abstract: | TBA | |
| Wednesday 19 June 2024, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774 | IPHT-MAT (Séminaire de matrices, cordes et géométries aléatoires) | hep-th |
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| Abstract: | TBD | |
| Tuesday 25 June 2024, 11:00 at LPTMS, Salle des séminaires du FAST et du LPTMS | LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay)) | cond-mat.stat-mech |
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| Wednesday 26 June 2024, 11:00 at LKB, Amphi Budé – Collège de France – 11 Place Marcelin Berthelot – 75005 | SEM-LKB (Séminaire du Laboratoire Kastler Brossel) | quant-ph |
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| Abstract: | Many-body correlations drive a variety of important quantum phenomena and quantum machines including superconductivity and magnetism in condensed matter as well as quantum computers. Understanding and controlling quantum many-body correlations is thus one of the central goals of modern science and technology. My research group has recently pioneered a novel pathway towards this goal with nearby ultracold atoms excited with an ultrashort laser pulse to a Rydberg state far beyond the Rydberg blockade regime [1-7]. We first applied our ultrafast coherent control with attosecond precision [2,3] to a random ensemble of those Rydberg atoms in an optical dipole trap, and successfully observed and controlled their strongly correlated electron dynamics on a sub-nanosecond timescale [1]. This new approach is now applied to arbitrary atom arrays assembled with optical lattices or optical tweezers that develop into a pathbreaking platform for quantum simulation and quantum computing on an ultrafast timescale [4-7]. In this ultrafast quantum computing, as schematically shown in Fig. 1, we have recently succeeded in executing a controlled-Z gate, a conditional two-qubit gate essential for quantum computing, in only 6.5 nanoseconds at quantum speed limit, where the gate speed is solely determined by the interaction strength between two qubits [5]. This is faster than any other two-qubit gates with cold-atom hardware by two orders of magnitude. It is also two orders of magnitude faster than the noise from the external environment and operating lasers, whose timescale is in general 1 microsecond or slower, and thus can be safely isolated from the noise. Moreover, this two-qubit gate is faster than the fast two-qubit gate demonstrated recently by “Google AI Quantum” with superconducting qubits [8]. References [1] N. Takei et al., Nature Commun. 7, 13449 (2016). Highlighted by Science 354, 1388 (2016); IOP PhyscisWorld.com (2016). [2] H. Katsuki et al., Acc. Chem. Res. 51, 1174 (2018). [3] C. Liu et al., Phys. Rev. Lett. 121, 173201 (2018). [4] M. Mizoguchi et al., Phys. Rev. Lett. 124, 253201 (2020). [5] Y. Chew et al., Nature Photonics 16, 724 (2022). (Front Cover Highlight) [6] V. Bharti et al., Phys. Rev. Lett. 131, 123201 (2023). [7] V. Bharti et al., arXiv:2311.15575 (2023). [8] B. Foxen et al., Phys. Rev. Lett. 125, 120504 (2020). | |
| Thursday 29 May 2025, 14:00 at IMO, Online-only. Zoom link by subscribing at https://seedseminar.apps.math.cnrs.fr/ | SEED (Seed Seminar of Mathematics and Physics) | math-ph |
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