5,792 research outputs found
Quaternionic Electroweak Theory
We explicitly develop a quaternionic version of the electroweak theory, based
on the local gauge group . The need of a complex
projection for our Lagrangian and the physical significance of the anomalous
scalar solutions are also discussed.Comment: 12 pages, Revtex, submitted to J. Phys.
Partial ovoids and partial spreads in symplectic and orthogonal polar spaces
We present improved lower bounds on the sizes of small maximal partial ovoids and small maximal partial spreads in the classical symplectic and orthogonal polar spaces, and improved upper bounds on the sizes of large maximal partial ovoids and large maximal partial spreads in the classical symplectic and orthogonal polar spaces. An overview of the status regarding these results is given in tables. The similar results for the hermitian classical polar spaces are presented in [J. De Beule, A. Klein, K. Metsch, L. Storme, Partial ovoids and partial spreads in hermitian polar spaces, Des. Codes Cryptogr. (in press)]
Relevant market delineation with the use of strategic business information.
In his paper a, overview of methods used in antitrust analysis to delineate relevant markets is provided and shortcomings are pointed out. A practical methodology to delineate relevant geographical and product markets is developed, starting from the theoretical definition of a relevant antitrust market. Based on criteria used by business strategists in segmenting markets, the new methodology makes use of strategic information on the position of a company and its competitors in a specific industry sector to delineate relevant markets. The usefulness of the new methodology is illustrated from the European truck industry.
Imaginary in all directions: an elegant formulation of special relativity and classical electrodynamics
A suitable parameterization of space-time in terms of one complex and three
quaternionic imaginary units allows Lorentz transformations to be implemented
as multiplication by complex-quaternionic numbers rather than matrices.
Maxwell's equations reduce to a single equation.Comment: 8 page
Thermodynamics of the three-dimensional Hubbard model: Implications for cooling cold atomic gases in optical lattices
We present a comprehensive study of the thermodynamic properties of the
three-dimensional fermionic Hubbard model, with application to cold fermionic
atoms subject to an optical lattice and a trapping potential. Our study is
focused on the temperature range of current experimental interest. We employ
two theoretical methods - dynamical mean-field theory and high-temperature
series - and perform comparative benchmarks to delimitate their respective
range of validity. Special attention is devoted to understand the implications
that thermodynamic properties of this system have on cooling. Considering the
distribution function of local occupancies in the inhomogeneous lattice, we
show that, under adiabatic evolution, the variation of any observable (e.g.,
temperature) can be conveniently disentangled into two distinct contributions.
The first contribution is due to the redistribution of atoms in the trap during
the evolution, while the second one comes from the intrinsic change of the
observable. Finally, we provide a simplified picture of the cooling procedure
recently proposed in J.-S. Bernier et al., Phys. Rev. A 79, 061601 (2009) by
applying this method to an idealized model.Comment: 17 pages, 27 figures, version published in PR
Stability and distortions of liquid crystal order in a cell with a heterogeneous substrate
We study stability and distortions of liquid crystal nematic order in a cell
with a random heterogeneous substrate. Modeling this system as a bulk xy model
with quenched disorder confined to a surface, we find that nematic order is
marginally unstable to such surface pinning. We compute the length scale beyond
which nematic distortions become large and calculate orientational correlation
functions using the functional renormalization-group and matching methods,
finding universal logarithmic and double-logarithmic distortions in two and
three dimensions, respectively. We extend these results to a finite-thickness
liquid crystal cell with a second homogeneous substrate, detailing crossovers
as a function of random pinning strength and cell thickness. We conclude with
analysis of experimental signatures of these distortions in a conventional
crossed-polarizer-analyzer light microscopy.Comment: 27 pages, 15 figures, Published in PRE, with minor typos correcte
Universality of transport properties of ultra-thin oxide films
We report low-temperature measurements of current-voltage characteristics for
highly conductive Nb/Al-AlOx-Nb junctions with thicknesses of the Al interlayer
ranging from 40 to 150 nm and ultra-thin barriers formed by diffusive oxidation
of the Al surface. In the superconducting state these devices have revealed a
strong subgap current leakage. Analyzing Cooper-pair and quasiparticle currents
across the devices, we conclude that the strong suppression of the subgap
resistance comparing with conventional tunnel junctions originates from a
universal bimodal distribution of transparencies across the Al-oxide barrier
proposed earlier by Schep and Bauer. We suggest a simple physical explanation
of its source in the nanometer-thick oxide films relating it to strong local
barrier-height fluctuations which are generated by oxygen vacancies in thin
aluminum oxide tunnel barriers formed by thermal oxidation.Comment: revised text and a new figur
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