Laboratoire de Physique Théorique et Hautes Energies
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80294Propositions de stage ou thèse au LPTHE
http://www.lpthe.jussieu.fr/spip/spip.php?article223
http://www.lpthe.jussieu.fr/spip/spip.php?article22320200329T17:14:07Ztext/htmlfrPietro SlavichActualité du laboratoire
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Matière Condensée et Physique Statistique
http://www.lpthe.jussieu.fr/spip/spip.php?article63
http://www.lpthe.jussieu.fr/spip/spip.php?article6320121107T18:01:14Ztext/htmlfrAdmin LPTHEPhysique Statistique et Matière Condensée
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Quantum out of equilibrium dynamics
http://www.lpthe.jussieu.fr/spip/spip.php?article213
http://www.lpthe.jussieu.fr/spip/spip.php?article21320121106T22:38:38Ztext/htmlfrAdmin LPTHEPhysique Statistique et Matière Condensée
<p>Besides their experimental relevance and possible technological application, the behavior of quantum systems out of equilibrium is a topic of fundamental interest, the understanding of which is still at an early stage. Some techniques of classical dissipative systems have been generalized to the quantum case but important questions remain to be answered such as which would be the meaning of the effective temperature appearing in fluctuationdissipation relations out of equilibrium. The (...)</p>

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<div class='rss_texte'><p>Besides their experimental relevance and possible technological application, <br class='autobr' />
the behavior of quantum systems out of equilibrium is a topic of fundamental<br class='autobr' />
interest, the understanding of which is still at an early stage.<br class='autobr' />
Some techniques of classical dissipative systems have been generalized to the quantum case but important questions remain to be answered such as which would be the meaning of the effective temperature appearing in fluctuationdissipation relations out of equilibrium. <br class='autobr' />
The timedependent (second and higher order) correlation functions and the (linear and nonlinear) responses of systems evolving close to equilibrium satisfy a number of model independent relations. In classical dynamics these fluctuationdissipation theorems are Ward identities of a symmetry of the, generically nonMarkovian, dynamic generating functional. The quantum version is work in progress. We studied the effect of a drive, realized in the form of the coupling to <br class='autobr' />
two fermion reservoirs at different chemical potentials, on the phase transition and coarsening dynamics of coupled quantum rotors. In experimental systems the coupling to an environment is usually unavoidable. We studied the effect of a nonOhmic classical bath on the critical (Langevin) dynamics of the classical —phi4, O(N) model in the large N limit by using the dynamic renormalizationgroup. We showed that although the critical temperature and critical dimensions <br class='autobr' />
are not altered by the bath, the dynamic critical exponent is, for sufficiently subOhmic baths. As a step towards understanding impurity motion in one dimensional ultra cold quantum liquids, we derived the non equilibrium correlation function of a quantum Brownian particle with general Gaussian<br class='autobr' />
nonfactorizing initial conditions. We studied the possible emergence of thermal behavior long after the quench of a closed quantum system by studying fluctuationdissipation relations in which parameters replace the equilibrium temperature. We analyzed these relations in the stationary regime after a quench in the transverse field of the quantum Ising chain. <br class='autobr' />
The lack of thermalization to a Gibbs ensemble became apparent with this approach.</p></div>
Dynamics through phase transitions
http://www.lpthe.jussieu.fr/spip/spip.php?article212
http://www.lpthe.jussieu.fr/spip/spip.php?article21220121106T22:33:51Ztext/htmlfrAdmin LPTHEPhysique Statistique et Matière Condensée
<p>Subcritical coarsening is the process whereby a macroscopic system in contact with an equilibrium reservoir orders after a rapid change in a parameter that takes it from a disordered phase into an ordered one in its equilibrium phase diagram. Closely related is critical coarsening, the process whereby a critical state is approached by quenching a disordered system right to the critical point. One of our goals is to characterize the geometry of coarsening phenomena in distribution. We (...)</p>

<a href="http://www.lpthe.jussieu.fr/spip/spip.php?rubrique12" rel="directory">Physique Statistique et Matière Condensée</a>
<div class='rss_texte'><p>Subcritical coarsening is the process whereby a macroscopic system in contact with an equilibrium reservoir orders after a rapid change in a parameter that takes it from a disordered phase into an ordered one in its equilibrium phase diagram. Closely related is critical coarsening, the process whereby a critical state is approached by quenching a disordered system right to the critical point. <br class='autobr' />
One of our goals is to characterize the geometry of coarsening phenomena in distribution. We studied analytically the statistical and geometric properties of ordered structures in planar curvature driven coarsening. The results provide the first analytic proof of dynamic scaling in more than one dimension for a finite dimensional order parameter. We studied numerically 2d phase separation, domain growth <br class='autobr' />
in the random bond ferromagnetic Ising model and the Potts model. Experiments in a liquid crystal film confirmed our predictions and demonstrated that monitoring the timeevolution of structures can be a very efficient way to determine the dynamic universality class. More recently, we analyzed these same questions after a quench to a critical point. We studied the relaxation of the 2d kinetically constrained spiral model. We showed that any unblocked state decorrelates in finite times in the full phase diagram and we proved that the dynamics occur via coarsening of vacancy lines.<br class='autobr' />
Quenches at very slow rates attracted a lot of attention in the cosmology and the condensed matter communities. A proposal for the coolingrate dependence is given by the KibbleZurek (KZ) mechanism. We revisited these ideas in phase ordering systems across a second order phase transition and we revealed the limitations of the KZ mechanism. Next, we extended the analysis to the KT transition in the 2d XY model.</p></div>
Fluctuations in glassy systems
http://www.lpthe.jussieu.fr/spip/spip.php?article211
http://www.lpthe.jussieu.fr/spip/spip.php?article21120121106T22:28:54Ztext/htmlfrAdmin LPTHEPhysique Statistique et Matière Condensée
<p>Glassy dynamics occur out of equilibrium with special properties such as physical aging, memory effects and dynamic heterogeneities, that is to say, regions of particles rearranging cooperatively at the nanometer scale, at very different rates compared with the bulk. Such features have been observed in a wide variety of materials including vortex matter in highTc superconductors. The symmetry that captures the universal fluctuating aging dynamics of glassy systems should be the (...)</p>

<a href="http://www.lpthe.jussieu.fr/spip/spip.php?rubrique12" rel="directory">Physique Statistique et Matière Condensée</a>
<div class='rss_texte'><p>Glassy dynamics occur out of equilibrium with special properties such as physical aging, memory effects and dynamic heterogeneities, that is to say, regions of particles rearranging cooperatively at the nanometer scale, at very different rates compared with the bulk. Such features have been observed in a wide variety of<br class='autobr' />
materials including vortex matter in highTc superconductors. <br class='autobr' />
The symmetry that captures the universal fluctuating aging dynamics of glassy systems should be the invariance of an effective dynamical action under uniform reparametrizations of the timescales.<br class='autobr' />
This scenario was put to the test with Monte Carlo simulations of the 3d<br class='autobr' />
EdwardsAnderson spinglass, the 3d random field Ising model, and confocal <br class='autobr' />
microscopy data on dense (supercooled liquid and glassy) colloidal suspensions. <br class='autobr' />
We constructed restricted averages to obtain objects with a better statistics than the<br class='autobr' />
completely fluctuating ones. The outcome of these studies is that while truly glassy systems conform to the consequences of the hypothesis, simple coarsening does not with timereparametrization invariance being reduced to time rescaling at the heart of the difference. This result suggests that the fluctuations are intimately related to the global effective temperature.<br class='autobr' />
A directed elastic manifold in random media is a system with many glassy aspects due to the competition between elasticity and disorder. The study of the EdwardsWilkinson and a disordered elastic line, confirmed the growth of a coherence length that controls the scaling properties of averaged observables. A set of regimes going from normal diffusive aging to saturation a la FamilyVicsek for finitelength lines passing through activated aging have been exhibited. The fluctuations of twotime quantities behave has also been analyzed.<br class='autobr' />
As a first step towards a successful field theory of Brownian particles in interaction, we studied exactly the Brownian gas. Even though the particles do not interact, the field theory contains an interaction term that enforce the constraint of a strictly positive density field. In this paper we determined nonperturbatively the Poissonian nature of the ground state.</p></div>
Electronic systems in low dimensions.
http://www.lpthe.jussieu.fr/spip/spip.php?article210
http://www.lpthe.jussieu.fr/spip/spip.php?article21020121106T22:25:02Ztext/htmlfrAdmin LPTHEPhysique Statistique et Matière Condensée
<p>1) Onedimensional interacting electrons. An important class of multiloop diagrams (beyond the DzyaloshinskiiLarkin theorem) has been related to the equilibration of onedimensional interacting electrons. The remarkable result is the derivation of a T3law for the energy relaxation of thermal carriers.<br class='autobr' />
2) Reduced quantum electrodynamics (RQED). We have computed radiative corrections, up to 2 loop, for a general RQED. Remarkable results have been found : when the gauge field is (...)</p>

<a href="http://www.lpthe.jussieu.fr/spip/spip.php?rubrique12" rel="directory">Physique Statistique et Matière Condensée</a>
<div class='rss_texte'><p>1) Onedimensional interacting electrons. An important class of multiloop diagrams (beyond the DzyaloshinskiiLarkin theorem) has been related to the equilibration of onedimensional interacting electrons. The remarkable result is the derivation of a T3law for the energy relaxation of thermal carriers.</p> <p>2) Reduced quantum electrodynamics (RQED). We have computed radiative corrections, up to 2 loop, for a general RQED. Remarkable results have been found : when the gauge field is fourdimensional, its beta function is zero (as in the Luttinger liquid case). Moreover, the 2loop interaction correction numerical constant to the polarization operator (conductivity) has been computed. It's smallness may be an indication that interaction correction are (still) diffcult to observe experimentally for (nonrelativistic) graphene.</p> <p>3) Skyrmion lattices for integer quantum Hall systems. We have studied quantum Hall ferromagnets with topologically charged spin textures in the presence of internal degrees of freedom such as spin, valley, or layer indices, so that the system is parametrised by a dcomponent complex spinor field.<br class='autobr' />
In particular we have computed analytically the complete lowlying excitation spectrum, which separates into d^21 gapless acoustic magnetic modes and a magnetophonon.</p></div>
Publications du LPTHE sur INSPIRE
http://www.lpthe.jussieu.fr/spip/spip.php?article189
http://www.lpthe.jussieu.fr/spip/spip.php?article18920111006T15:58:22Ztext/htmlfrAdmin LPTHEPublications du LPTHE sur INSPIRE

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partie de
http://www.lpthe.jussieu.fr/spip/spip.php?article6
http://www.lpthe.jussieu.fr/spip/spip.php?article620080424T15:59:22Ztext/htmlfrAdmin LPTHEA noter
<p>Le laboratoire fait partie<br class='autobr' />
de l'ILP <br class='autobr' /> (Institut Lagrange de Paris)<br class='autobr' /> <br class='autobr' />
Le laboratoire fait partie<br class='autobr' />
de la FRIF <br class='autobr' /> (Fédération de Recherche Interactions Fondamentales)</p>

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(Fédération de Recherche Interactions Fondamentales)</p></div>
Dernières publications
http://www.lpthe.jussieu.fr/spip/spip.php?article176
http://www.lpthe.jussieu.fr/spip/spip.php?article17620080424T15:38:49Ztext/htmlfrAdmin LPTHEA noter
<p>Dernières publications ] Report of the GDR worki... ano.nymous@ccsd.cnrs.fr.invalid (R. Barbier) Sdual Inflation and the ... ano.nymous@ccsd.cnrs.fr.invalid (Luis A. Anchordoqui) Modulidependent KK tower... ano.nymous@ccsd.cnrs.fr.invalid (Anthony Ashmore) Expectation management... ano.nymous@ccsd.cnrs.fr.invalid (Johannes Braathen) Multicentered black hole... ano.nymous@ccsd.cnrs.fr.invalid (Guillaume (...)</p>

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<div class='rss_texte'><p>Dernières publications<br/></p>
<ul><li><a href="http://hal.in2p3.fr/in2p300003414" onclick="window.open(this.href); return false;">] Report of the GDR worki...</a><br/>
ano.nymous@ccsd.cnrs.fr.invalid (R. Barbier)</li>
<li><a href="https://hal.archivesouvertes.fr/hal03186218" onclick="window.open(this.href); return false;">Sdual Inflation and the ...</a><br/>
ano.nymous@ccsd.cnrs.fr.invalid (Luis A. Anchordoqui)</li>
<li><a href="https://hal.archivesouvertes.fr/hal03186187" onclick="window.open(this.href); return false;">Modulidependent KK tower...</a><br/>
ano.nymous@ccsd.cnrs.fr.invalid (Anthony Ashmore)</li>
<li><a href="https://hal.archivesouvertes.fr/hal03186154" onclick="window.open(this.href); return false;">Expectation management...</a><br/>
ano.nymous@ccsd.cnrs.fr.invalid (Johannes Braathen)</li>
<li><a href="https://hal.archivesouvertes.fr/hal03178618" onclick="window.open(this.href); return false;">Multicentered black hole...</a><br/>
ano.nymous@ccsd.cnrs.fr.invalid (Guillaume Beaujard)</li>
</ul></div>
Bibliothèque
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