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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241001T140000
DTEND;TZID=Europe/Paris:20241001T153000
DTSTAMP:20260417T110847
CREATED:20240923T063437Z
LAST-MODIFIED:20240925T080132Z
UID:10987-1727791200-1727796600@fermi.univ-tlse3.fr
SUMMARY:Facteurs de forme effectifs pour l’asymptotique des déterminants de Fredholm à température finie. - (Oleksandr Gamayun / LPT / Seminar). - 1/10/2024\, 14H
DESCRIPTION:Oleksandr Gamayun (London Institute for Mathematical Sciences) \nSeminar LPT\, 1/10/2024\, 14H\, 3R1\, seminar room\, 3rd floor \nAbstract \nThe behavior of correlation functions in one-dimensional quantum systems at zero temperature is now very well understood in terms of linear and non-linear Luttinger models. The « microscopic » justification of these models consists in the exact accounting for soft-mode excitations around the vacuum state and at most few high-energy excitations. At finite temperature\, or more generically for finite entropy states\, this direct approach is not strictly applicable due to the different structure of « soft » excitations. We focus on physical systems where the strong interaction makes it possible to present correlation functions in terms of Fredholm determinants of the generalized sine kernels. Based on « microscopic » resummations\, we develop a phenomenological approach of the effective form factors that allow us to describe the asymptotic behavior of these Fredholm determinants. We demonstrate how this works for correlation functions in the XY model\, mobile impurity\, and the generic Toeplitz determinants.
URL:https://fermi.univ-tlse3.fr/event/facteurs-de-forme-effectifs-pour-lasymptotique-des-determinants-de-fredholm-a-temperature-finie-oleksandr-gamayun-lpt-seminar-1-10-2024-14h/
LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241014T103000
DTEND;TZID=Europe/Paris:20241014T120000
DTSTAMP:20260417T110847
CREATED:20241008T083108Z
LAST-MODIFIED:20241009T091613Z
UID:10947-1728901800-1728907200@fermi.univ-tlse3.fr
SUMMARY:Réaliser la matière fractonique : De la théorie à l’information quantique\, en passant par les plateformes expérimentales. - (Andriy Nevidomskyy / LPT / Seminar). - 14/10/2024\, 10H30
DESCRIPTION:Andriy Nevidomskyy(Université Rice) \nSeminar LPT\, 14/10/2024/2024\, 10H\, 3R1\, seminar room\, 3rd floor
URL:https://fermi.univ-tlse3.fr/event/realiser-la-matiere-fractonique-de-la-theorie-a-linformation-quantique-en-passant-par-les-plateformes-experimentales-andriy-nevidomskyy-lpt-seminar-14-10-2024-10h30/
LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241022T140000
DTEND;TZID=Europe/Paris:20241022T153000
DTSTAMP:20260417T110847
CREATED:20241015T065156Z
LAST-MODIFIED:20241017T065442Z
UID:11067-1729605600-1729611000@fermi.univ-tlse3.fr
SUMMARY:Exploiter les symétries dans la physique quantique à plusieurs corps. - (Lukas Devos / LPT / Seminar). - 22/10/2024\, 14H
DESCRIPTION:Lukas Devos (Université de Gand) \nSeminar LPT\, 22/10/2024\, 14H\, 3R1\, seminar room\, 3rd floor \nAbstract :\nIn the study of quantum many-body systems\, symmetries play a crucial role in understanding emergent phenomena and reducing computational complexity. Here I will explore how exploiting symmetries within the tensor network formalism can provide more insights into the properties of these complex systems. We will discuss how tensor networks serve as powerful tools for efficiently representing and simulating quantum states. By incorporating global symmetries in a local manner into these frameworks\, we can significantly enhance the efficiency of numerical algorithms and capture essential features of quantum phases and transitions. The goal is to briefly introduce how tensor networks serve as numerical tools to study condensed matter systems\, and then shed some light on the additional steps required to include symmetries\, hinting at the underlying mathematical structures.
URL:https://fermi.univ-tlse3.fr/event/exploiter-les-symetries-dans-la-physique-quantique-a-plusieurs-corps-lukas-devos-lpt-seminar-12-11-2024-14h/
LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241025T140000
DTEND;TZID=Europe/Paris:20241025T170000
DTSTAMP:20260417T110847
CREATED:20241023T064253Z
LAST-MODIFIED:20241024T111732Z
UID:11065-1729864800-1729875600@fermi.univ-tlse3.fr
SUMMARY:Monte Carlo investigations of Dirac and chiral spin liquids. - (Sasank Budaraju / LPT / Thesis). - 25/10/2024\, 14H
DESCRIPTION:Thesis defense \nSasank Budaraju\, LPT\, 3R4 Fermi Seminar room \nAbstract: \nQuantum Spin Liquids (QSLs) are exotic states of matter characterized by their many-body quantum entanglement and emergent fractionalized excitations\, whose low energy physics is described using gauge theories. The experimental realization of QSLs in crystalline materials and their existence as stable ground states in spin models have been fundamental and widely studied questions in condensed matter physics in recent years. \nIn this thesis\, we employ quantum Monte Carlo simulations to investigate two questions related to QSLs in two dimensions: one focused on gapped spin liquids and the other on gapless spin liquids. The first question concerns whether Projected Entangled Pair States (PEPS\, a type of Tensor Network) can accurately represent Chiral Spin Liquids (CSL). Questions have been raised due to a no-go theorem preventing free fermion PEPS representations of chiral non-interacting states. We construct fermionic PEPS (fPEPS) approximants of Gutzwiller-projected Chern insulators (a type of CSL)\, and demonstrate that fPEPS (of finite bond dimension) can capture the correct topological ground-state degeneracy of the CSL. Further\, more general fPEPS are optimized to describe the CSL phase of a frustrated Heisenberg antiferromagnet\, and the chiral edge modes in the entanglement spectrum are shown to follow the predictions from conformal field theory. Consequently\, our work provides additional supporting evidence that PEPS can effectively\nrepresent CSL phases. \nThe second question focuses on the nature of low-energy excitations in gapless Dirac Spin Liquids (DSLs)\, which\, unlike gapped spin liquids\, lack well-defined fractionalized quasiparticle excitations. Since mean-field descriptions of DSLs may not fully capture their behavior\, it is crucial to account for gauge fluctuations beyond the mean-field level. Additionally\, the stability of DSLs as ground states in frustrated Heisenberg antiferromagnets remains an unsettled question. In this work\, we construct variational ansatzes for low-energy excitations of DSLs. Our results indicate that Heisenberg models on triangular and Kagome lattices support gapless monopole and spinon excitations even after Gutzwiller projection. We further demonstrate that the Dirac spin liquid is energetically stable against the formation of chiral spin liquid states generated by multiple monopole insertions. Moreover\, we analyze the momentum quantum numbers of the monopoles\, comparing the states before and after projection. Finally\, we construct flux excitations localized on (pairs of) individual plaquettes. They are gapped in the thermodynamic limit as expected\, but surprisingly have comparable (or even lower) energy than the monopoles for small clusters. Through these results\, we provide incremental insights in understanding the low energy excitations of U(1) spin liquids in two dimensions. \n\n \n \n 
URL:https://fermi.univ-tlse3.fr/event/monte-carlo-investigations-of-dirac-and-chiral-spin-liquids-sasank-budaraju-lpt-thesis-25-10-2024-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,HDR / Thesis,LPT
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