Ref HAL: hal-02302517_v1
DOI: 10.1016/j.sse.2019.03.004
WoS: WOS:000466840600002
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Résumé:

- A classical computer with N bits at any given moment is in one of its possible 2N states. - In contrast, the state of the hypothetical quantum computer with N qubits is defined by the values of 2N continuous parameters, the quantum amplitudes. - To beat your laptop in performing some special tasks, like factoring very large numbers, one needs ∼1000 qubits. - Accordingly, the number of continuous variables that should be under our control is at least 21000 ∼ 10300. - Thus the answer to the question in the title is: as soon as physicists and engineers will learn to control thus number of degrees of freedom, which means NEVER.

Ref HAL: hal-02302374_v1
DOI: 10.1002/andp.201800486
WoS: WOS:000471714300003
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The screened Coulomb potential plays a crucial role in the binding energies of excitons in a thin dielectric slab. The asymptotic behavior of this potential is studied when the thickness of the slab is very small as compared to the exciton Bohr radius. A regularized expression is given and the exact effective 2D potential is derived. These expressions may be useful for the computation of the exciton binding energy in 2D or quasi‐2D materials.

Ref HAL: hal-02302300_v1
Ref Arxiv: 1905.08179
DOI: 10.1063/1.5113477
WoS: WOS:000483889300020
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
9 Citations
Résumé:

We perform stringent tests of thermodynamic theories of the glass transition over the experimentally relevant temperature regime for several simulated glass-formers. The swap Monte Carlo algorithm is used to estimate the configurational entropy and static point-to-set lengthscale, and careful extrapolations are used for the relaxation times. We first quantify the relation between configurational entropy and the point-to-set lengthscale in two and three dimensions. We then show that the Adam-Gibbs relation is generally violated in simulated models for the experimentally relevant time window. Collecting experimental data for several supercooled molecular liquids, we show that the same trends are observed experimentally. Deviations from the Adam-Gibbs relation remain compatible with random first order transition theory, and may account for the reported discrepancies between Kauzmann and Vogel-Fulcher-Tammann temperatures. Alternatively, they may also indicate that even near $T_g$ thermodynamics is not the only driving force for slow dynamics.

Commentaires: 13 pages, 8 figures. Réf Journal: J. Chem. Phys. 151, 084504 (2019)

Ref HAL: hal-02291288_v1
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Ref HAL: hal-02290852_v1
PMID 31433423
Ref Arxiv: 1812.08736
DOI: 10.1039/c9sm01092k
WoS: 000486046800009
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
36 Citations
Résumé:

Understanding the difference between universal low-temperature properties of amorphous and crystalline solids requires an explanation of the stronger damping of long-wavelength phonons in amorphous solids. A longstanding sound attenuation scenario, resulting from a combination of experiments, theories, and simulations, leads to a quartic scaling of sound attenuation with the wavevector, which is commonly attributed to Rayleigh scattering of the sound. Modern computer simulations offer conflicting conclusions regarding the validity of this picture. We simulate glasses with an unprecedentedly broad range of stabilities to perform the first microscopic analysis of sound damping in model glass formers across a range of experimentally relevant preparation protocols. We present a convincing evidence that quartic scaling is recovered for small wavevectors irrespective of the glass's stability. With increasing stability, the wavevector where the quartic scaling begins increases by approximately a factor of three and the sound attenuation decreases by over an order of magnitude. Our results uncover an intimate connection between glass stability and sound damping.

Commentaires: 8 pages, 8 figures. Réf Journal: Soft Matter 15, 7018 (2019)

Ref HAL: hal-02289228_v1
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Controlled motion and positioning of colloids and macromolecular complexes in a fluid, as well as catalytic particles in active environments, are fundamental processes in physics, chemistry and biology. Here we focus on an active biological system for which precise experimental results are available. Our work is fully inspired by studies of one of the most widespread and ancient mechanisms of liquid phase macromolecular segregation and positioning known in nature: bacterial DNA segregation systems. Efficient bacterial chromosome segregation typically requires the coordinated action of a three-component, fueled by adenosine triphosphate machinery called the partition complex. We can distinguish two steps: (i) a process of phase transition [2,3] to built a membraneless region of high protein concentration (partition complex) (ii) the action of molecular motor action upon the complex to create a chemical force. We present a phenomenological model [1] accounting for the dynamics of this system that is also relevant for the physics of catalytic particles in active environments. The model is obtained by coupling simple linear reaction-diffusion equations with a volumetric chemophoresis force field that arises from protein-protein interactions and provides a physically viable mechanism for complex translocation. This description captures experimental observations: dynamic oscillations of complex components, complex separation and symmetrical positioning. The predictions of our model are in agreement with and provide substantial insight into recent experiments. From a non-linear physics view point, this system explores the active separation of matter at micrometric scales with a dynamical instability between static positioning and travelling wave regimes triggered by the dynamical spontaneous breaking of rotational symmetry. We also discuss the phase transition mechanism giving rise to macromolecular assembly of proteins. Our predictions are compared to Super Resolution microscopy and microbiology experiments [1,2,3].[1] Walter J.-C., Dorignac J., Lorman V., Rech J., Bouet J.-Y., Nollmann M., Palmeri J., Parmeggiani A. and Geniet F., Phys. Rev. Lett. 119, 028101 (2017).[2] Debaugny R., Sanchez A., Rech J., Labourdette D., Dorignac J., Geniet F., Palmeri J., Parmeggiani A., Boudsocq, Leberre V., Walter* J.-C. and Bouet* J.-Y Mol. Syst. Biol. 14, e8516 (2018)[3] David G., Walter J.-C., Broedersz C., Dorignac J., Geniet F., Parmeggiani A., Walliser N.-O. and Palmeri J., submitted to Phys. Rev. Lett. [arXiv/1811.09234] (2019).

Ref HAL: hal-02285107_v1
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I'll show how twistorial description of quaternionic geometries combined with string theory dualities helped to solve a long standing mathematical problem - to understand modular properties of indefinite theta series. Then I'll use the solution of this problem to describe the modular behavior of the generatingfunction of degeneracies of BPS black holes appearing in Calabi-Yau compactifications of string theory.