2,082,058 research outputs found

    A Tight-Binding Investigation of the NaxCoO2 Fermi Surface

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    We perform an orthogonal basis tight binding fit to an LAPW calculation of paramagnetic Nax_xCoO2_2 for several dopings. The optimal position of the apical oxygen at each doping is resolved, revealing a non-trivial dependence of the band structure and Fermi surface on oxygen height. We find that the small eg_{g'} hole pockets are preserved throughout all investigated dopings and discuss some possible reasons for the lack of experimental evidence for these Fermi sheets

    Axial symmetry and conformal Killing vectors

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    Axisymmetric spacetimes with a conformal symmetry are studied and it is shown that, if there is no further conformal symmetry, the axial Killing vector and the conformal Killing vector must commute. As a direct consequence, in conformally stationary and axisymmetric spacetimes, no restriction is made by assuming that the axial symmetry and the conformal timelike symmetry commute. Furthermore, we prove that in axisymmetric spacetimes with another symmetry (such as stationary and axisymmetric or cylindrically symmetric spacetimes) and a conformal symmetry, the commutator of the axial Killing vector with the two others mush vanish or else the symmetry is larger than that originally considered. The results are completely general and do not depend on Einstein's equations or any particular matter content.Comment: 15 pages, Latex, no figure

    Stress-free Spatial Anisotropy in Phase-Ordering

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    We find spatial anisotropy in the asymptotic correlations of two-dimensional Ising models under non-equilibrium phase-ordering. Anisotropy is seen for critical and off-critical quenches and both conserved and non-conserved dynamics. We argue that spatial anisotropy is generic for scalar systems (including Potts models) with an anisotropic surface tension. Correlation functions will not be universal in these systems since anisotropy will depend on, e.g., temperature, microscopic interactions and dynamics, disorder, and frustration.Comment: 4 pages, 4 figures include

    Putative fishery-induced changes in biomass and population size structures of demersal deep-sea fishes in ICES Sub-area VII, Northeast Atlantic Ocean

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    This work was supported by a series of NERC grants to the principal investigators including NE/C512961/1. The results of the early joint SAMS and IOS surveys were digitized with support from EU MAST Contract MAS2-CT920033 1993–1995, and data analyses was supported by EU FP7 Projects HERMES and HERMIONE. We thank Alain Zuur from Highland Statistics Ltd. for advice with the statistical analyses and Odd Aksel Bergstad for valuable comments that helped to improve the manuscript. We thank the ships’ companies of the RRS Challenger and RRS Discovery.Peer reviewedPublisher PD

    Lax Operator for the Quantised Orthosymplectic Superalgebra U_q[osp(2|n)]

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    Each quantum superalgebra is a quasi-triangular Hopf superalgebra, so contains a \textit{universal RR-matrix} in the tensor product algebra which satisfies the Yang-Baxter equation. Applying the vector representation π\pi, which acts on the vector module VV, to one side of a universal RR-matrix gives a Lax operator. In this paper a Lax operator is constructed for the CC-type quantum superalgebras Uq[osp(2n)]U_q[osp(2|n)]. This can in turn be used to find a solution to the Yang-Baxter equation acting on VVWV \otimes V \otimes W where WW is an arbitrary Uq[osp(2n)]U_q[osp(2|n)] module. The case W=VW=V is included here as an example.Comment: 15 page
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