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Production scientifique
(408) Production(s) de l'année 2015
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Non-perturbative effects in Calabi-Yau compactifications
Auteur(s): Alexandrov S.
(Séminaires)
CERN (Geneve, SZ), 2015-06-30
Résumé: I'll review the current understanding of the low energy effective theory resulting from compactifications of Type II superstrings on Calabi-Yau manifolds. The effective action can be encoded into the metric on a moduli space which is known to receive quantum stringy corrections, both perturbative and non-perturbative. I'll show how the non-perturbative geometry of this moduli space can be described using twistorial techniques. In the end, I'll argue that the instanton effects coming from NS5-branes, whose understanding is still very incomplete, might be related to a quantization of a certain integrable structure.
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Non-perturbative effects in string theory compactifications
Auteur(s): Alexandrov S.
(Séminaires)
Trinity College (Dublin, IE), 2015-03-25
Résumé: I'll review the current understanding of the low energy effective
theory resulting from compactifications of Type II superstrings on
Calabi-Yau manifolds. The effective action can be encoded into the
metric on a moduli space which is known to receive quantum stringy
corrections, both perturbative and non-perturbative. I'll show how
the non-perturbative geometry of this moduli space can be
described using twistorial techniques. In the end, I'll argue that
the instanton effects coming from NS5-branes, whose understanding
is still very incomplete, might be related to a quantization of a
certain integrable structure.
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Processes controlling the diameter distribution of single-walled carbon nanotubes grown by catalytic CVD
Auteur(s): Jourdain V.
Conference: NanoteC 15 (Oxford, GB, 2015-09-14)
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Evolution of the diameter distribution of single-walled carbon nanotubes during catalytic CVD and underlying processes
Auteur(s): Jourdain V.
Conference: GDR Graphene and Nanotubes (Aussois, FR, 2015-12-02)
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Thermally activated nonlocal amplification in quantum energy transport
Auteur(s): Antezza M.
Conférence invité: META15: International Conference on Metamaterials (New York, US, 2015-08-05)
Ref HAL: hal-01909536_v1
Exporter : BibTex | endNote
Résumé: We will discuss the behavior of one or more elementary quantum systems (atoms, molecules, quantum dots,etc) interacting with a stationary, simple and rich electromagnetic environment out of thermal equilibrium. Particularattention will be devoted to the new features that this system offers toward the possibility to manipulatecollective atomic states and leading to improved performances in: creation and protection of entanglement,quantum thermal machines, transport of excitations.
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Quantum thermal machines with single nonequilibrium environments
Auteur(s): Antezza M.
Conférence invité: FQMT15 “Frontiers of Quantum and Mesoscopic Thermodynamics” (Prague, CZ, 2015-07-28)
Ref HAL: hal-01909535_v1
Exporter : BibTex | endNote
Résumé: We will discuss the behavior of one or more elementary quantum system (atom, molecules,quantum dot, . . . ) interacting with a stationary, simple and rich electromagnetic environmentout of thermal equilibrium: The electromagnetic field is produced by a simple configuration ofmacroscopic objects held at thermal equilibrium at different temperatures. We will show howthe internal atomic dynamics can be deeply affected by the non equilibrium configurationleading to unexpected phenomena like a spontaneous inversion of population, new coolingmechanisms obtained by heating the system [1], and the possibility to create and protect entanglementin a stationary and robust way [2]. Finally, we will discuss how this system maydirectly allow the realization of atomic quantum thermal machines, with high efficiency and agenuine quantum behavior [3].------------[1] B. Bellomo, R. Messina, and M. Antezza, Europhys. Lett. 100, 20006 (2012)[2] B. Bellomo and M. Antezza, Europhys. Lett. 104, 10006 (2013)[3] B. Leggio, B. Bellomo, and M. Antezza, Phys. Rev. A 91, 012117 (2015)
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Spectroscopic studies of supramolecular organization in bridged silsesquioxanes via Self-Assembly through Hydrogen Bonding
Auteur(s): Freitas Vânia, Le Parc R., Wong Chi Man M., Cattoën Xavier, Creff G., Ferreira Rute A. S., Carlos Luis D., Bantignies J.-L.
Conference: XIV Encontro da SBPMat (Rio de Janeiro, BR, 2015-09-27)
Ref HAL: hal-01909533_v1
Exporter : BibTex | endNote
Résumé: Nanostructuring and control over morphology in hybrid solids are of great interest for the design of polyfunctional materials. For appropriately designed bridged silsesquioxanes, the bridging organic unit is able to self-direct the structure of the solid network independently of any external structure-directing agent. Indeed anisotropic organization due to interactions between organic substructure units was demonstrated with urea functional groups capable of self-assembly via H-bonding (1). We previously showed that H-bonding interactions between precursor molecules during the hydrolysis–condensation of trialkoxysilanes can deeply influence kinetic parameters of the gelation and modify the texture and morphology of the resulting silsesquioxane (2).Considering that the bridging unit plays a key role on controlling the arrangement of the material over a long-range, we developed new hybrid precursors (fig 1) liable to exhibit modulated hydrogen-bonding properties via organic substructures with either two urea groups (UU) or two thiourea groups (TT). It is expected that the strength of the H bonding decreases from urea to thiourea links.We here report our studies on the influence of H-bonding strength on the self-organization properties of the organic substructures and corresponding hybrid solids using vibrational spectroscopies (Raman, Far and Middle Infrared spectroscopies coupled with DFT calculations). Far infrared domain probing directly the intermolecular H-bonding vibrations is shown to be very sensitive to long range arrangement of organic substructure. Besides, as amide vibrations are very sensitive to intermolecular H bonding strength and dispersion, temperature dependence studies of the vibrational dynamic of the internal modes, likely to give insights into the supramolecular interactions, were performed. Additionally, in-situ high pressure infrared studies of intra- and intermolecular interactions demonstrate the role of supramolecular interactions on the mechanical response of hybrid materials towards compression.Following these studies, we propose a mechanistic model for the self-assembling process in H-bonded bridged silsesquioxanes.
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