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Ref Arxiv: 1512.03540
DOI: 10.1063/PT.3.3052
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93 Citations
Résumé:

Glasses constitute a widespread form of solid matter, and glass production has been an important human technology for more than 3000 years. Despite that long history, new ways to understand the fundamental physics of glasses continue to emerge.

Commentaires: 13 pages, 5 figures. To appear in the January 2016 issue of Physics Today (in press). Réf Journal: Physics Today 69, 40 (2016)

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Ref Arxiv: 1511.07756
DOI: 10.1088/0953-8984/28/7/075201
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10 Citations
Résumé:

We introduce a temporal scheme for data sampling, based on a variable delay between two successive data acquisitions. The scheme is designed so as to reduce the average data flow rate, while still retaining the information on the data evolution on fast time scales. The practical implementation of the scheme is discussed and demonstrated in light scattering and microscopy experiments that probe the dynamics of colloidal suspensions using CMOS or CCD cameras as detectors.

Commentaires: Published in J. Phys.: Cond. Matter. 11 pages, 5 figures + Supporting Data (Python software to implement the method described in the manuscript)

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Ref Arxiv: 1512.03406
DOI: 10.1016/j.nuclphysbps.2016.02.021
WoS: WOS:000375626800021
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Our renormalization group consistent variant of optimized perturbation, RGOPT, is used to calculate the nonperturbative QCD spectral density of the Dirac operator and the related chiral quark condensate $\langle \bar q q \rangle$, for $n_f=2$ and $n_f=3$ massless quarks. Sequences of approximations at two-, three-, and four-loop orders are very stable and give $\langle \bar q q \rangle^{1/3}_{n_f=2}(2\, {\rm GeV}) = -(0.833-0.845) \bar\Lambda_2 $, and $ \langle \bar q q \rangle^{1/3}_{n_f=3}(2\, {\rm GeV}) = -(0.814-0.838) \bar\Lambda_3 $ where the range is our estimated theoretical error and $\bar\Lambda_{n_f}$ the basic QCD scale in the $\rm \bar{MS}$-scheme. We compare those results with other recent determinations (from lattice calculations and spectral sum rules).

Commentaires: 5 pages, talk given at 18th International Conference in Quantum Chromodynamics (QCD 15) Montpellier, published in the proceedings

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Ref Arxiv: 1512.03811
DOI: 10.1063/1.4943294
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Résumé:

We recall the relation between Zeta function representation of groups and two-dimensional topological Yang-Mills theory through Mednikh formula. We prove various generalisations of Mednikh formulas and define generalization of Zeta functions representations of groups. We compute some of these functions in the case of the finite group $GL(2, {\mathbb F}_q)$ and $PGL(2,{\mathbb F}_q).$ We recall the table characters of these groups for any $q$, compute the Frobenius-Schur indicator of their irreducible representations and give the explicit structure of their fusion rings

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Ref Arxiv: 1511.02892
DOI: 10.1007/s11005-016-0857-3
WoS: 000379609000002
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2 Citations
Résumé:

Motivated by mathematical structures which arise in string vacua and gauge theories with N=2 supersymmetry, we study the properties of certain generalized theta series which appear as Fourier coefficients of functions on a twisted torus. In Calabi-Yau string vacua, such theta series encode instanton corrections from $k$ Neveu-Schwarz five-branes. The theta series are determined by vector-valued wave-functions, and in this work we obtain the transformation of these wave-functions induced by Kontsevich-Soibelman symplectomorphisms. This effectively provides a quantum version of these transformations, where the quantization parameter is inversely proportional to the five-brane charge $k$. Consistency with wall-crossing implies a new five-term relation for Faddeev's quantum dilogarithm $\Phi_b$ at $b=1$, which we prove. By allowing the torus to be non-commutative, we obtain a more general five-term relation valid for arbitrary $b$ and $k$, which may be relevant for the physics of five-branes at finite chemical potential for angular momentum.

Commentaires: 26 pages

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Ref Arxiv: 1507.08399
DOI: 10.1103/PhysRevB.93.161114
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5 Citations
Résumé:

Due to the existence of open channels, light could theoretically be transmitted through disorderedmedia with 100% efficiency. However, because of the large number of channels to be controlledor measured, this has been never observed experimentally. To avoid this difficulty we considerobservables easier to handle experimentally. By measuring the correlations of the field transmittedthrough a disordered medium, we were able to count the number of channels involved in transmissionand to compare this number with theory. For a sample of transmission 1=25, we get a number ofmodes about 15 times smaller than for free space propagation. This figure is in good agreementwith theoretical prediction.

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PMID 26849585
Ref Arxiv: 1507.03508
DOI: 10.1103/PhysRevLett.116.031601
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11 Citations
Résumé:

We use the scalar model with quartic interaction to illustrate how a nonperturbative variational technique combined with renormalization group (RG) properties efficiently resums perturbative expansions in thermal field theories. The resulting convergence and scale dependence of optimized thermodynamical quantities, here illustrated up to two-loop order, are drastically improved as compared to standard perturbative expansions, as well as to other related methods such as the screened perturbation or (resummed) hard-thermal-loop perturbation, that miss RG invariance (as we explain). Being very general and easy to implement, our method is a potential analytical alternative to dealing with the phase transitions of field theories such as thermal QCD.

Commentaires: 5 pages, 1 figure