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(64) Production(s) de l'année 2024
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Spontaneous breaking of time-reversal symmetry and time-crystal states in chiral atomic systems
Auteur(s): Antezza M.
Conférence invité: FQMT 2024 - Frontiers of Quantum and Mesoscopic Thermodynamics (Prague, CZ, 2024-07-22)
Résumé: We present a theoretical study of the interaction between an atom characterized by a degenerate ground state and a reciprocal environment, such as a semiconductor nanoparticle, without the presence of external bias. Our analysis reveals that the combined influence of the electron's intrinsic spin magnetic moment on the environment and the chiral atomic dipolar transitions may lead to either the spontaneous breaking of time-reversal symmetry or the emergence of time-crystal-like states with remarkably long relaxation times. The different behavior is ruled by the handedness of the precession motion of the atom's spin vector, which is induced by virtual chiral-dipolar transitions. Specifically, when the relative orientation of the precession angular velocity and the electron spin vector is as in a spinning top, the system manifests time-crystal-like states. Conversely, with the opposite relative orientation, the system experiences spontaneous symmetry breaking of time reversal symmetry. Our findings introduce a mechanism for the spontaneous breaking of time-reversal symmetry in atomic systems, and unveil an exciting opportunity to engineer a nonreciprocal response at the nanoscale, exclusively driven by the quantum vacuum fluctuations.
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On the different models of Graphene conductivity and its effects on Casimir forces and on radiative heat transfer in nanostructured systems
Auteur(s): Antezza M.
Conférence invité: META 2024 - The 14th International Conference on Metamaterials, Photonic Crystals and Plasmonics (Toyama, JP, 2024-07-17)
Résumé: We discuss different available models of graphene conductivity, and their effects on two main fluctuational electrodynamics phenomena in nanostructured systems.
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Spontaneous breaking of time-reversal symmetry and time-crystal states in chiral atomic systems
Auteur(s): Antezza M.
(Séminaires)
Department of Physics, National University of Singapore (NUS) (Singapour, SG), 2024-07-11
Résumé: We present a theoretical study of the interaction between an atom characterized by a degenerate ground state and a reciprocal environment, such as a semiconductor nanoparticle, without the presence of external bias. Our analysis reveals that the combined influence of the electron's intrinsic spin magnetic moment on the environment and the chiral atomic dipolar transitions may lead to either the spontaneous breaking of time-reversal symmetry or the emergence of time-crystal-like states with remarkably long relaxation times. The different behavior is ruled by the handedness of the precession motion of the atom's spin vector, which is induced by virtual chiral-dipolar transitions. Specifically, when the relative orientation of the precession angular velocity and the electron spin vector is as in a spinning top, the system manifests time-crystal-like states. Conversely, with the opposite relative orientation, the system experiences spontaneous symmetry breaking of time reversal symmetry. Our findings introduce a mechanism for the spontaneous breaking of time-reversal symmetry in atomic systems, and unveil an exciting opportunity to engineer a nonreciprocal response at the nanoscale, exclusively driven by the quantum vacuum fluctuations.
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Scaling Properties of Gelling Systems in Nonlinear Shear Experiments ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Louhichi A., Morel Marie-Hélène, Ramos L., Banc A.![Auteur correspondant (Corresp.)](plugins/aigle//images/corresponding.gif)
(Article) Publié:
Acs Macro Letters, vol. p.826-831 (2024)
Ref HAL: hal-04629902_v1
DOI: 10.1021/acsmacrolett.4c00121
Exporter : BibTex | endNote
Résumé: We study model near-critical polymer gelling systems made of gluten protein dispersions stabilized at different distances from the gel point. We impose different shear rates and follow the time evolution of the stress. For sufficiently large shear rates, an intermediate stress overshoot is measured before reaching the steady state. We evidence self-similarity of the stress overshoot as a function of the applied shear rate for samples with various distances from the gel point, which is related to the elastic energy stored by the samples, as for dense systems close to the jamming transition. In concordance with the findings for glassy and jammed systems, we also measure that the stress after flow cessation decreases as a power law with time, with a characteristic relaxation time that depends on the shear rate previously imposed. These features revealed in nonlinear rheology could be the signature of a mesoscopic dynamics, which would depend on the extent of gelation.
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Mock modularity of Calabi-Yau threefolds
Auteur(s): Alexandrov S.
Conférence invité: Workshop on Number Theory and Physics (Trieste, IT, 2024-06-24)
Résumé: : String theory predicts that generating functions of rank 0 Donaldson-Thomas invariants, realized physically as D4-D2-D0 BPS indices in type IIA string theory on a CalabiYau threefold, are (higher depth) mock moduar forms with a specific modular completion. I'll show how the modular anomaly equations can be solved to get the generating functions up to modular ambiguities. The solution is found in terms of indefinite theta series.
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Modular Bootstrap for BPS Black Holes
Auteur(s): Alexandrov S.
Conférence invité: BPS Dynamics and Quantum Mathematics (Florence, IT, 2024-05-20)
Résumé: I'll explain the modular properties of the generating functions of rank 0 Donaldson-Thomas invariants, equal to D4-D2-D0 BPS indices in Calabi-Yau compactifications of string theory, and their physical origin. These properties can be used to find generating functions up to a finite number of coefficients, the so-called polar terms, which in turn can be fixed using wall-crossing. I'll show how this program is realized for compact one-parameter Calabi-Yau threefolds and 2 units of D4-brane charge, leading to explicit mock modular forms encoding BPS indices. For higher charges, the polar terms remain so far inaccessibble, but I'll present a general solution of modular anomaly equations in terms of indefinite theta series.
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Direct Numerical Analysis of Dynamic Facilitation in Glass-Forming Liquids ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Herrero C., Berthier L.
(Article) Publié:
Physical Review Letters, vol. 132 p.258201 (2024)
Texte intégral en Openaccess : ![arxiv](plugins/aigle//images/logo-arxiv.png)
Ref HAL: hal-04623148_v1
Ref Arxiv: 2310.16935
DOI: 10.1103/PhysRevLett.132.258201
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We propose a computational strategy to quantify the temperature evolution of the timescales and length scales over which dynamic facilitation affects the relaxation dynamics of glass-forming liquids at low temperatures, which requires no assumption about the nature of the dynamics. In two glass models, we find that dynamic facilitation depends strongly on temperature, leading to a subdiffusive spreading of relaxation events which we characterize using a temperature-dependent dynamic exponent. We also establish that this temperature evolution represents a major contribution to the increase of the structural relaxation time.
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