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(75) Production(s) de l'année 2016


Multiple D3instantons and mock modular forms I
Auteur(s): Alexandrov S., Banerjee S., Manschot Jan, Pioline Boris
(Document sans référence bibliographique)
Ref HAL: cea01318414_v1
Ref Arxiv: 1605.05945
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We study D3instanton corrections to the hypermultiplet moduli space in type IIB string theory compactified on a CalabiYau threefold. In a previous work, consistency of D3instantons with Sduality was established at first order in the instanton expansion, using the modular properties of the M5brane elliptic genus. We extend this analysis to the twoinstanton level, where wallcrossing phenomena start playing a role. We focus on the contact potential, an analogue of the Kähler potential which must transform as a modular form under Sduality. We show that it can be expressed in terms of a suitable modification of the partition function of D4D2D0 BPS black holes, constructed out of the generating function of MSW invariants (the latter coincide with DonaldsonThomas invariants in a particular chamber). Modular invariance of the contact potential then requires that, in case where the D3brane wraps a reducible divisor, the generating function of MSW invariants must transform as a vectorvalued mock modular form, with a specific modular completion built from the MSW invariants of the constituents. Physically, this gives a powerful constraint on the degeneracies of BPS black holes. Mathematically, our result gives a universal prediction for the modular properties of DonaldsonThomas invariants of pure twodimensional sheaves.
Commentaires: 33 pages




Theory of morphological transformation of viral capsid shell during the maturation process in the HK97 bacteriophage and similar viruses
Auteur(s): Konevtsova O., Lorman V., Rochal S.B.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 93 p.052412 (2016)
Ref HAL: hal01319073_v1
DOI: 10.1103/PhysRevE.93.052412
Exporter : BibTex  endNote
Résumé: We consider the symmetry and physical origin of collective displacement modes playing a crucial role in the morphological transformation during the maturation of the HK97 bacteriophage and similar viruses. It is shown that the experimentally observed hexamer deformation and pentamer twist in the HK97 procapsid correspond to the simplest irreducible shear strain mode of a spherical shell. We also show that the icosahedral faceting of the bacteriophage capsid shell is driven by the simplest irreducible radial displacement field. The shear field has the rotational icosahedral symmetry group I while the radial field has the full icosahedral symmetry Ih . Thisdifference makes their actions independent. The radial field sign discriminates between the icosahedral and the dodecahedral shapes of the faceted capsid shell, thus making the approach relevant not only for the HK97like viruses but also for the parvovirus family. In the frame of the LandauGinzburg formalism we propose a simple phenomenological model valid for the first reversible step of the HK97 maturation process. The calculated phase diagram illustrates the discontinuous character of the virus shape transformation. The characteristics of the virus shell faceting and expansion obtained in the in vitro and in vivo experiments are related to the decrease in the capsid shell thickness and to the increase of the internal capsid pressure.



Nonequilibrium CasimirLifshitz force between gratings
Auteur(s): Guizal B., Antezza M.
Conférence invité: Casimir and van der Waals Physics: Progress and Prospects (HongKong, CN, 20160425)
Ref HAL: hal01318653_v1
Exporter : BibTex  endNote
Résumé: I will present our studies of the CasimirLifshitz interaction in a system consisting of two different onedimensional dielectric lamellar gratings at two different temperatures, immersed in an environment having a third temperature [1]. The calculations are based on the knowledge of the scattering operators, obtained through the Fourier modal method. It will be shown that the interplay between nonequilibrium effects and geometrical periodicity offers a rich scenario for the manipulation of the force. Finally I will present our latest results on a spheregrating system at equilibrium [2].



Heat transfer and CasimirLifshitz interactions between diffraction gratings: numerical methods
Auteur(s): Guizal B., Antezza M.
Conférence invité: Heat transfer at the nanoscale (Bad Honnef, DE, 20160410)
Ref HAL: hal01318643_v1
Exporter : BibTex  endNote
Résumé: Heat transfer or between bodies and CasimirLifshitz (CL) interactions between them share in common the fact that they can be characterized by the electromagnetic response of these bodies. It has been shown, in the framework of a general theory [1], that the knowledge of the socalled scattering matrix of an object is sufficient to perform its thermal of Casimir interaction with another body. Among the different configurations studied experimentally, those involving gratings and spheres are of special interest. From the theoretical point of view, when one is equipped with the scattering matrix based theory [1], it is “in principle” straightforward to compute the heat transfer or the CL force. In reality, it turns out that computing the Smatrices is not that easy, especially when it has to be determined for a huge number of modes. It is thus of fundamental importance to use extremely efficient methods. We will discuss the different families of existing approaches for diffraction gratings and examine in more details one of the most efficient ones: the Fourier Modal Method that we used recently to compute CL interactions between gratings out of thermal equilibrium [2] and between a sphere and a grating [3].



Structure of aluminasilica nanoparticles grafted withalkylphosphonic acids in poly(ethylacrylate) nanocomposites
Auteur(s): Schmitt pauly Céline, Genix A.C., Alauzun Johan G., Jestin Jacques, Sztucki Michael, Mutin P. Hubert, Oberdisse J.
(Article) Publié:
Polymer, vol. 97 p.138146 (2016)
Ref HAL: hal01317973_v1
DOI: 10.1016/j.polymer.2016.04.073
Exporter : BibTex  endNote
Résumé: Aluminacoated silica nanoparticles (NPs) grafted with phosphonic acids of different hydrophobicitywere used as filler in poly(ethylacrylate) nanocomposites. Phosphonic acids bearing short alkyl chains ora diethylene glycol group have been grafted at densities up to 3.2 P/nm2 on NPs (20 nm) dispersed inwater. Nanocomposites at particle fractions up to 10 vol% have been formulated by casting from thecolloidal mixtures of modified NPs and nanolatex in water. The dispersion of the NPs in the polymermatrix has been studied by TEM combined with smallangle scattering, evidencing aggregation of NPs.TEM shows micrometerscale inhomogeneities depending on the surface/polymer matrix compatibility.For the local interparticle correlations, a quantitative analysis of the intensity based on the mapping ontothe effective structure factor of polydisperse hard spheres is developed. This mapping allows the modelfreedetermination of the internal volume fraction of aggregates, termed compacity k, to between 10%and 30%, compatible with the TEM analysis. k is found to increase for the higher particle volume fractions,to decrease with grafting density, and to be mostly independent of the nature and mass of thegraft. Preliminary evidence for an improved compatibility of grafted with respect to bare NPs is found, asopposed to their aqueous precursor suspensions where some preaggregation is induced by grafting.



Multiple D3instantons and mock modular forms I
Auteur(s): Alexandrov S., Banerjee S., Manschot Jan, Pioline Boris
(Document sans référence bibliographique) 20160519
Ref Arxiv: 1605.05945
Ref. & Cit.: NASA ADS
Résumé: We study D3instanton corrections to the hypermultiplet moduli space in type IIB string theory compactified on a CalabiYau threefold. In a previous work, consistency of D3instantons with Sduality was established at first order in the instanton expansion, using the modular properties of the M5brane elliptic genus. We extend this analysis to the twoinstanton level, where wallcrossing phenomena start playing a role. We focus on the contact potential, an analogue of the Kahler potential which must transform as a modular form under Sduality. We show that it can be expressed in terms of a suitable modification of the partition function of D4D2D0 BPS black holes, constructed out of the generating function of MSW invariants (the latter coincide with DonaldsonThomas invariants in a particular chamber). Modular invariance of the contact potential then requires that, in case where the D3brane wraps a reducible divisor, the generating function of MSW invariants must transform as a vectorvalued mock modular form, with a specific modular completion built from the MSW invariants of the constituents. Physically, this gives a powerful constraint on the degeneracies of BPS black holes. Mathematically, our result gives a universal prediction for the modular properties of DonaldsonThomas invariants of pure twodimensional sheaves.
Commentaires: 33 pages



Intrinsic limitation of cavityenhanced Faraday detection of spin noise in quantum wells and quantum dots
Auteur(s): Scalbert D.
(Article) Publié:
Superlattices And Microstructures, vol. 92 p.348352 (2016)
Ref HAL: hal01316527_v1
DOI: 10.1016/j.spmi.2016.02.014
Exporter : BibTex  endNote
Résumé: Spin noise spectroscopy is a quite attractive experimental tool for studying unperturbed spin dynamics and magnetic resonance in semiconductor nanostructures. However in some cases its practical interest maybe severely limited by the weakness of the spin noise signal to be detected. In this paper we examine by how much the detection of spin noise of magnetic atoms or of nuclei, in quantum wells or quantum dots, can be improved by making use of cavityenhanced Faraday rotation. The conditions for optimized cavities are first determined. In reflection geometry it corresponds to tune the cavity to the critical point of impedance matching. It is shown that even for optimized cavities the enhancement in spin noise detection is intrinsically limited by absorption. It turns out that the cavity effect improves the spin noise detection only when the inhomogeneous broadening of the involved optical resonance is large compared to its radiative broadening.
