Podcasts about floquet

durée : 00:04:08 - Une semaine dans leurs vies - Pour ce troisième épisode de notre série en compagnie de musiciens de bals populaires, nous continuons de suivre Dominique et Stéphanie Floquet. Le frère et la sœur jouent dans l'orchestre qui porte leur nom depuis 30 ans.

durée : 00:04:17 - Une semaine dans leurs vies - Pour ce deuxième épisode de notre série sur les musiciens de bals populaires dans le Berry, nous continuons à suivre l'orchestre Dominique et Stéphanie Floquet. Leur vie professionnelle, c'est sur la scène, mais aussi sur la route, et tout un travail de l'ombre.

durée : 00:04:04 - Une semaine dans leurs vies - Avec le printemps, c'est le retour des guinguettes. Nous partons donc toute cette semaine à la rencontre de musiciens de bals populaires, de dancings, de baloches, de bastringues... Bref, de ces hommes et de ces femmes qui passent leur vie à vous faire danser au son de l'accordéon.

Recent experiments suggest the phenomenon of light induced superconductivity above Tc in two different materials: fullerene superconductor K3C60 and high Tc cuprate YBCO. I will discuss the distinct phenomena taking place in these systems. In K3C60, the unusual character of electron-phonon interactions results in enhanced BCS pairing through optical driving and the slow relaxation of superconducting correlations after they have been created. In YBCO the light induced state is short lived and its properties can be explained from the perspective of a Floquet material. I will present a general theoretical framework for understanding Floquet materials, in which the pump-induced oscillations of a collective mode lead to the parametric generation of excitation pairs. This can result in features such as photo- induced edges in reflectivity, enhancement of reflectivity, and even light amplification.

No polititzem l'esport. En Cirici celebra el dia més feliç: ha vingut Pedro Sánchez. La Superilla agafa forma: en parlem amb en Roger Saperas.

Nalini AnantharamanGéométrie spectraleCollège de FranceAnnée 2022-2023Séminaire - Ergodicité et thermalisation des fonctions propres : Mobility Edge of Lévy MatricesIntervenant(s) : Charles Bordenave, Institut de Mathématiques de MarseilleRésuméI will discuss the problem of unreasonable effectiveness of random matrix theory for description of spectral fluctuations in extended quantum lattice systems. A class oflocally interacting spin systems has been recently identified where the spectral form factor is proven to match with gaussian or circular ensembles of random matrix theory, and where spatiotemporal correlation functions of local observables as well as some measures of dynamical complexity can be calculated analytically. These, so-called dual unitary systems, include integrable, non-ergodic, ergodic, and generically, (maximally) chaotic cases. After reviewing the basic properties of dual unitary Floquet circuits, I will argue that correlation functions of these models are generally perturbatively stable with respect to breaking dual-unitarity, and describe a simple result within this framework.

Nalini AnantharamanGéométrie spectraleCollège de FranceAnnée 2022-2023Séminaire - Ergodicité et thermalisation des fonctions propres : Exactly Solved Models of Many-Body Quantum ChaosIntervenant(s) : Tomaž Prosen, Université de LjubljanaRésuméI will discuss the problem of unreasonable effectiveness of random matrix theory for description of spectral fluctuations in extended quantum lattice systems. A class oflocally interacting spin systems has been recently identified where the spectral form factor is proven to match with gaussian or circular ensembles of random matrix theory, and where spatiotemporal correlation functions of local observables as well as some measures of dynamical complexity can be calculated analytically. These, so-called dual unitary systems, include integrable, non-ergodic, ergodic, and generically, (maximally) chaotic cases. After reviewing the basic properties of dual unitary Floquet circuits, I will argue that correlation functions of these models are generally perturbatively stable with respect to breaking dual-unitarity, and describe a simple result within this framework.

Mavric Floquet, comptable de formation, a quitté la France pour s'établir à Rouyn-Noranda pour étudier en création numérique. Juste après avoir expliqué la passion de son père pour le film Top Gun et Tom Cruise lui-même, on jase donc de ses projets numériques, de jeux vidéo non-genré, non-violent, de son projet dj… On jase aussi du processus d'un immigrant établi pour devenir citoyen canadien.

Adri Romeo e Ignasi Taltavull visitan el Museo de Cera de Barcelona. La Casa de Papel, King Kong y la vida de Floquet de Neu. Los cocineros enfrentados a los pintores. Las tardes aburridas de Einstein. La alfombra roja, los Beatles y el túnel del terror.

Topological Phases of Matter 2015

Topological Phases of Matter 2015

Topological Phases of Matter 2015

If we are interested in the propagation of waves around a small region of interest, like e.g. an obstacle inside a very big ("unbounded") domain, one way to bring such problems to the computer and solve them numerically is to cut that unbounded domain to a bounded domain. But to have a well-posed problem we have to prescribe boundary conditions on the so-called artificial boundary, which are not inherent in our original problem. This is a classical problem which is not only connected to wave phenomena. Sonia Fliss is interested in so-called transparent boundary conditions. These are the boundary conditions on the artificial boundaries with just the right properties. There are several classical methods like perfectly matched layers (PML) around the region of interest. They are built to absorb incoming waves (complex stretching of space variable). But unfortunately this does not work for non-homogeneous media. Traditionally, also boundary integral equations were used to construct transparent boundary conditions. But in general, this is not possible for anisotropic media (or heterogenous media, e.g. having periodic properties). The main idea in the work of Sonia Fliss is quite simple: She surrounds the region of interest with half spaces (three or more). Then, the solutions in each of these half spaces are determined by Fourier transform (or Floquet waves for periodic media, respectively). The difficulty is that in the overlap of the different half spaces the representations of the solutions have to coincide. Sonia Fliss proposes a method which ensures that this is true (eventually under certain compatibility conditions). The chosen number of half spaces does not change the method very much. The idea is charmingly simple, but the proof that these solutions exist and have the right properties is more involved. She is still working on making the proofs more easy to understand and apply. It is a fun fact, that complex media were the starting point for the idea, and only afterwards it became clear that it also works perfectly well for homogeneous (i.e. much less complex) media. One might consider this to be very theoretical result, but they lead to numerical simulations which match our expectations and are quite impressive and impossible without knowing the right transparent boundary conditions. Sonia Fliss is still very fascinated by the many open theoretical questions. At the moment she is working at Ecole Nationale Supérieure des Techniques avancées (ENSTA) near Paris as Maitre de conférence. Literature and additional material C. Besse, J. Coatleven, S. Fliss, I. Lacroix-Violet, K. Ramdani: Transparent boundary conditions for locally perturbed infinite hexagonal periodic media, arXiv preprint arXiv:1205.5345, 2012. S. Fliss, P. Joly: Exact boundary conditions for time-harmonic wave propagation in locally perturbed periodic media, Applied Numerical Mathematics 59.9: 2155-2178, 2009. L. Bourgeois, S. Fliss: On the identification of defects in a periodic waveguide from far field data, Inverse Problems 30.9: 095004, 2014.

If we are interested in the propagation of waves around a small region of interest, like e.g. an obstacle inside a very big ("unbounded") domain, one way to bring such problems to the computer and solve them numerically is to cut that unbounded domain to a bounded domain. But to have a well-posed problem we have to prescribe boundary conditions on the so-called artificial boundary, which are not inherent in our original problem. This is a classical problem which is not only connected to wave phenomena. Sonia Fliss is interested in so-called transparent boundary conditions. These are the boundary conditions on the artificial boundaries with just the right properties. There are several classical methods like perfectly matched layers (PML) around the region of interest. They are built to absorb incoming waves (complex stretching of space variable). But unfortunately this does not work for non-homogeneous media. Traditionally, also boundary integral equations were used to construct transparent boundary conditions. But in general, this is not possible for anisotropic media (or heterogenous media, e.g. having periodic properties). The main idea in the work of Sonia Fliss is quite simple: She surrounds the region of interest with half spaces (three or more). Then, the solutions in each of these half spaces are determined by Fourier transform (or Floquet waves for periodic media, respectively). The difficulty is that in the overlap of the different half spaces the representations of the solutions have to coincide. Sonia Fliss proposes a method which ensures that this is true (eventually under certain compatibility conditions). The chosen number of half spaces does not change the method very much. The idea is charmingly simple, but the proof that these solutions exist and have the right properties is more involved. She is still working on making the proofs more easy to understand and apply. It is a fun fact, that complex media were the starting point for the idea, and only afterwards it became clear that it also works perfectly well for homogeneous (i.e. much less complex) media. One might consider this to be very theoretical result, but they lead to numerical simulations which match our expectations and are quite impressive and impossible without knowing the right transparent boundary conditions. Sonia Fliss is still very fascinated by the many open theoretical questions. At the moment she is working at Ecole Nationale Supérieure des Techniques avancées (ENSTA) near Paris as Maitre de conférence. Literature and additional material C. Besse, J. Coatleven, S. Fliss, I. Lacroix-Violet, K. Ramdani: Transparent boundary conditions for locally perturbed infinite hexagonal periodic media, arXiv preprint arXiv:1205.5345, 2012. S. Fliss, P. Joly: Exact boundary conditions for time-harmonic wave propagation in locally perturbed periodic media, Applied Numerical Mathematics 59.9: 2155-2178, 2009. L. Bourgeois, S. Fliss: On the identification of defects in a periodic waveguide from far field data, Inverse Problems 30.9: 095004, 2014.

We present here an application of the recently developed hybrid coupled channels approach to study photo-ionization of noble gas atoms: Neon and Argon. We first compute multi-photon ionization rates and cross-sections for these inert gas atoms with our approach and compare them with reliable data available from R-matrix Floquet theory. The good agreement between coupled channels and R-matrix Floquet theory show that our method treats multi-electron systems on par with the well established R-matrix theory. We then apply the time dependent surface flux (tSURFF) method with our approach to compute total and angle resolved photo-electron spectra from Argon with linearly and circularly polarized 12 nm wavelength laser fields, a typical wavelength available from Free Electron Lasers (FELs)

Rueckriemen, R (Dartmouth College) Monday 26 July 2010, 17:30-17.45

Zaidenberg, M (Institut Fourier) Friday 30 July 2010, 10:30-11.15

La sala Charles Floquet Paris

We present an original method for the accurate quantum treatment of the planar three body Coulomb problem under electromagnetic driving. Our ab initio approach combines Floquet theory, complex dilation, and the representation of the Hamiltonian in suitably chosen coordinates without adjustable parameters. The resulting complex-symmetric, sparse banded generalized eigenvalue problem of rather high dimension is solved using advanced techniques of parallel programming. In the present thesis, this theoretical/numerical machinery is employed to provide a complete description of the bound and of the doubly excited spectrum of the field-free 2D helium atom. In particular, we report on frozen planet quantum states in planar helium. For the driven atom, we focus on the near resonantly driven frozen planet configuration, and give evidence for the existence of nondispersive two-electron wave packets which propagate along the associated periodic orbit. This represents a highly nontrivial qualitative confirmation of earlier calculations on a 1D model atom, though with important enhancements of the decay rate of these atomic eigenstates in the field, due to the transverse decay channel. The latter is already found to enhance the decay rates of the unperturbed frozen planet as compared to the 1D model, in surprisingly good quantitative agreement with 3D results.