Reduced-Order Modelling of the Bending of an Array of Torsional Micromirrors

Reduced-Order Modelling of the Bending of an Array of An array of micromirrors for beam steering optical switching has been designed in a thick polysilicon technology. A novel semi-analytical method to calculate the static characteristics of the micromirrors by taking into account the flexural deformation of the structure is presented. The results are compared with 3D coupled-field FEM simulation.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Density and spin response of a strongly-interacting Fermi gas in the attractive and quasi-repulsive regime

Recent experimental advances in ultra-cold Fermi gases allow for exploring response functions under different dynamical conditions. In particular, the issue of obtaining a "quasi-repulsive" regime starting from a Fermi gas with an attractive inter-particle interaction while avoiding the formation of the two-body bound state is currently debated. Here, we provide a calculation of the density and spin response for a wide range of temperature and coupling both in the attractive and quasi-repulsive regime, whereby the system is assumed to evolve non-adiabatically toward the "upper branch" of the Fermi gas. A comparison is made with the available experimental data for these two quantities.Comment: 8 pages, 7 figures, to appear on Phys. Rev. Let

Pairing effects in the normal phase of a two-dimensional Fermi gas

In a recent experiment [M. Feld et al., Nature 480, 75 (2011); B. Froehlich et al., Phys. Rev. Lett. 109,130403 (2012)], a pairing gap was detected in a two-dimensional (2D) Fermi gas with attractive interaction at temperatures where superfluidity does not occur. The question remains open as to whether this gap is a pseudogap phenomenon or is due to a molecular state. In this paper, by using a t-matrix approach, we reproduce quite well the experimental data for a 2D Fermi gas, and set the boundary between the pseudogap and molecular regimes. We also show that pseudogap phenomena occurring in 2D and 3D can be related through a variable spanning the BCS-BEC crossover in a universal way.Comment: 10 pages, 9 figures; final versio

On consistent solutions for strategic games

Nash equilibrium;game theory

Lack of NMDA receptor subunit exchange alters Purkinje cell dendritic morphology in cerebellar slice cultures

Early postnatal developmental changes in N-methyl-D-aspartate (NMDA) receptor (NR) subunits regulate cerebellar granule cell maturation and potentially Purkinje cell development. We therefore investigated Purkinje cell morphology in slice cultures from mice with genetic subunit exchange from NR2C to NP2B (NRX-2B). NR2C-2B Purkinje cells after 12 days in vitro showed a significantly impaired dendritic arbour complexity with reduced branching density as compared to wild-type cells, a phenotype that was reversed by NMDA treatment. These data support the concept that in cerebellar slice cultures, Purkinje cell dendritic outgrowth is regulated by granule cell inputs. (c) 2005 Elsevier B.V. All rights reserved

Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas

Physical properties of an ultracold Fermi gas in the temperature-coupling phase diagram can be characterized by the contact intensity C, which enters the pair-correlation function at short distances and describes how the two-body problem merges into its surrounding. We show that the local order established by pairing fluctuations about the critical temperature Tc of the superfluid transition considerably enhances the contact C in a temperature range where pseudogap phenomena are maximal. Our ab initio results for C in a trap compare well with recently available experimental data over a wide coupling range. An analysis is also provided for the effects of trap averaging on C.Comment: 5 pages, 5 figure

Popov approximation for composite bosons in the BCS-BEC crossover

Theoretical treatments of the BCS-BEC crossover need to provide as accurate as possible descriptions of the two regimes where the diluteness condition applies, either in terms of the constituent fermions (BCS limit) or of the composite bosons which form as bound-fermion pairs (BEC limit). This has to occur via a single fermionic theory that bridges across these two limiting representations. In this paper, we set up successive improvements of the fermionic theory, that result into composite bosons described at the level of either the Bogoliubov or the Popov approximations for point-like bosons. This work bears on the recent experimental advances on the BCS-BEC crossover with trapped Fermi atoms, which show the need for accurate theoretical descriptions of BEC side of the crossover.Comment: 13 pages, 4 figure

La descrizione del mondo. Reportage immaginari dalla città asiatica

Il volume elettronico raccoglie una selezione dei "reportage immaginari" elaborati negli anni 2011/12 e 2012/13 dagli studenti dell'atelier storia/progetto del Politecnico di Torino "Progettare la città asiatica", diretto da Michele Bonino e Filippo De Pieri. Con un'introduzione dei due curator

Competition between final-state and pairing-gap effects in the radio-frequency spectra of ultracold Fermi atoms

The radio-frequency spectra of ultracold Fermi atoms are calculated by including final-state interactions affecting the excited level of the transition, and compared with the experimental data. A competition is revealed between pairing-gap effects which tend to push the oscillator strength toward high frequencies away from threshold, and final-state effects which tend instead to pull the oscillator strength toward threshold. As a result of this competition, the position of the peak of the spectra cannot be simply related to the value of the pairing gap, whose extraction thus requires support from theoretical calculations.Comment: 4 pages, 3 figures, final version published in Phys. Rev. Let

Time-dependent Gross-Pitaevskii equation for composite bosons as the strong-coupling limit of the fermionic BCS-RPA approximation

The linear response to a space- and time-dependent external disturbance of a system of dilute condensed composite bosons at zero temperature, as obtained from the linearized version of the time-dependent Gross-Pitaevskii equation, is shown to result also from the strong-coupling limit of the time-dependent BCS (or broken-symmetry RPA) approximation for the constituent fermions subject to the same external disturbance. In this way, it is possible to connect excited-state properties of the bosonic and fermionic systems by placing the Gross-Pitaevskii equation in perspective with the corresponding fermionic approximationsComment: 4 pages, 1 figur