4,646 research outputs found

    From Skew-Cyclic Codes to Asymmetric Quantum Codes

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    We introduce an additive but not F4\mathbb{F}_4-linear map SS from F4n\mathbb{F}_4^{n} to F42n\mathbb{F}_4^{2n} and exhibit some of its interesting structural properties. If CC is a linear [n,k,d]4[n,k,d]_4-code, then S(C)S(C) is an additive (2n,22k,2d)4(2n,2^{2k},2d)_4-code. If CC is an additive cyclic code then S(C)S(C) is an additive quasi-cyclic code of index 22. Moreover, if CC is a module θ\theta-cyclic code, a recently introduced type of code which will be explained below, then S(C)S(C) is equivalent to an additive cyclic code if nn is odd and to an additive quasi-cyclic code of index 22 if nn is even. Given any (n,M,d)4(n,M,d)_4-code CC, the code S(C)S(C) is self-orthogonal under the trace Hermitian inner product. Since the mapping SS preserves nestedness, it can be used as a tool in constructing additive asymmetric quantum codes.Comment: 16 pages, 3 tables, submitted to Advances in Mathematics of Communication

    Daily and seasonal variations in the spatial distribution of zooplankton populations in relation to the physical structure in the Ligurian Sea Front

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    Results from five hydrographic and biological surveys at different seasons across the Ligurian Sea front, using horizontal continuous measurements and vertical profiles are presented. The vertical circulation across the front is described, and two divergences and one convergence are identified as permanent features from data. The key to find their location for each survey is given. The spatial patterns of 14 zooplankton taxa along the transect are established using variance analysis, principal component and correspondence analyses. The spatial distribution of each taxon is related to the physical structure, and the convection cells evidenced by the scheme appear as different biotopes. The daily variability of the spatial distributions is negligible compared to the annual variability. Distinctions are made between coastal species always inhabiting the peripheral (coastal zone) and others with distinct coastal, frontal and offshore distributions varying with the season. For the latter species the frontal zone is a preferential biotope during their seasonal growth period. Consequently the accumulation of organisms near the convergence cannot be created by only the dynamic causes. The role of biological processes in the observed distributions is discussed

    A magnetic model for the incommensurate I phase of spin-Peierls systems

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    A magnetic model is proposed for describing the incommensurate I phase of spin-Peierls systems. Based on the harmonicity of the lattice distortion, its main ingredient is that the distortion of the lattice adjusts to the average magnetization such that the system is always gapful. The presence of dynamical incommensurabilities in the fluctuation spectra is also predicted. Recent experimental results for CuGeO_3 obtained by NMR, ESR and light scattering absorption are well understood within this model.Comment: 8 pages, 3 figures, Latex with EPL style files all include

    Introducing the Dark Energy Universe Simulation Series (DEUSS)

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    In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series (DEUSS) which aim at investigating the imprints of realistic dark energy models on cosmic structure formation. It represents the largest dynamical dark energy simulation suite to date in term of spatial dynamics. We first present the 3 realistic dark energy models (calibrated on latest SNIa and CMB data): LambdaCDM, quintessence with Ratra-Peebles potential, and quintessence with Sugra potential. We then isolate various contributions for non-linear matter power spectra from a series of pre-DEUSS high-resolution simulations (130 million particles). Finally, we introduce DEUSS which consist in 9 Grand Challenge runs with 1 billion particles each thus probing scales from 4 Gpc down to 3 kpc at z=0. Our goal is to make these simulations available to the community through the "Dark Energy Universe Virtual Observatory" (DEUVO), and the "Dark Energy Universe Simulations" (DEUS) consortium.Comment: 6 pages, 3 figures, to appear in the AIP proceedings of the 'Invisible Universe International Conference', UNESCO-Paris, June 29-July 3, 200

    On the Asymptotic Stability of De-Sitter Spacetime: a non-linear perturbative approach

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    We derive evolution and constraint equations for second order perturbations of flat dust homogeneous and isotropic solutions to the Einstein field equations using all scalar, vector and tensor perturbation modes. We show that the perturbations decay asymptotically in time and that the solutions converge to the De-Sitter solution. By induction, this result is valid for perturbations of arbitrary order. This is in agreement with the cosmic no-hair conjecture of Gibbons and Hawking.Comment: 11 pages, 2 figure

    Quantum internal modes of solitons in 1d easy-plane antiferromagnet in strong magnetic field

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    In presence of a strong external magnetic field the dynamics of solitons in a one-dimensional easy-plane Heisenberg antiferromagnet exhibits a number of peculiarities. Dynamics of internal soliton degrees of freedom is essentially quantum, and they are strongly coupled to the "translational" mode of soliton movement. These peculiarities lead to considerable changes in the response functions of the system which can be detected experimentally.Comment: 8 pages, RevTeX, 6 figures, uses psfig.sty, submitted to PR

    A Cosmological No-Hair Theorem

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    A generalisation of Price's theorem is given for application to Inflationary Cosmologies. Namely, we show that on a Schwarzschild--de Sitter background there are no static solutions to the wave or gravitational perturbation equations for modes with angular momentum greater than their intrinsic spin.Comment: 9 pages, NCL94 -TP4, (Revtex
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