4,100 research outputs found

    A convenient criterion under which Z_2-graded operators are Hamiltonian

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    We formulate a simple and convenient criterion under which skew-adjoint Z_2-graded total differential operators are Hamiltonian, provided that their images are closed under commutation in the Lie algebras of evolutionary vector fields on the infinite jet spaces for vector bundles over smooth manifolds.Comment: J.Phys.Conf.Ser.: Mathematical and Physical Aspects of Symmetry. Proc. 28th Int. colloq. on group-theoretical methods in Physics (July 26-30, 2010; Newcastle-upon-Tyne, UK), 6 pages (in press

    Lifetimes of Xi_{bc}^{+} and Xi_{bc}^{0} baryons

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    Estimates of lifetimes and partial branching ratios for the baryons Ξbc+\Xi_{bc}^{+} and Ξbc0\Xi_{bc}^{0} are presented using the inverse heavy quark mass expansion technique carried out in the Operator Product Expansion approach. We take into account both the perturbative QCD corrections to the spectator contributions and, depending on the quark contents of hadrons, the Pauli interference and weak scattering effects between the constituents, using a potential model for the evaluation of the non-perturbative parameters.Comment: 15 pages, LATEX file, 2 eps-figure

    On the variational noncommutative Poisson geometry

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    We outline the notions and concepts of the calculus of variational multivectors within the Poisson formalism over the spaces of infinite jets of mappings from commutative (non)graded smooth manifolds to the factors of noncommutative associative algebras over the equivalence under cyclic permutations of the letters in the associative words. We state the basic properties of the variational Schouten bracket and derive an interesting criterion for (non)commutative differential operators to be Hamiltonian (and thus determine the (non)commutative Poisson structures). We place the noncommutative jet-bundle construction at hand in the context of the quantum string theory.Comment: Proc. Int. workshop SQS'11 `Supersymmetry and Quantum Symmetries' (July 18-23, 2011; JINR Dubna, Russia), 4 page

    Bimodule structure of the mixed tensor product over Uqsℓ(2∣1)U_{q} s\ell(2|1) and quantum walled Brauer algebra

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    We study a mixed tensor product 3⊗m⊗3‾⊗n\mathbf{3}^{\otimes m} \otimes \mathbf{\overline{3}}^{\otimes n} of the three-dimensional fundamental representations of the Hopf algebra Uqsℓ(2∣1)U_{q} s\ell(2|1), whenever qq is not a root of unity. Formulas for the decomposition of tensor products of any simple and projective Uqsℓ(2∣1)U_{q} s\ell(2|1)-module with the generating modules 3\mathbf{3} and 3‾\mathbf{\overline{3}} are obtained. The centralizer of Uqsℓ(2∣1)U_{q} s\ell(2|1) on the chain is calculated. It is shown to be the quotient Xm,n\mathscr{X}_{m,n} of the quantum walled Brauer algebra. The structure of projective modules over Xm,n\mathscr{X}_{m,n} is written down explicitly. It is known that the walled Brauer algebras form an infinite tower. We have calculated the corresponding restriction functors on simple and projective modules over Xm,n\mathscr{X}_{m,n}. This result forms a crucial step in decomposition of the mixed tensor product as a bimodule over Xm,n⊠Uqsℓ(2∣1)\mathscr{X}_{m,n}\boxtimes U_{q} s\ell(2|1). We give an explicit bimodule structure for all m,nm,n.Comment: 43 pages, 5 figure

    Electron Spin Relaxation under Drift in GaAs

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    Based on a Monte Carlo method, we investigate the influence of transport conditions on the electron spin relaxation in GaAs. The decay of initial electron spin polarization is calculated as a function of distance under the presence of moderate drift fields and/or non-zero injection energies. For relatively low fields (a couple of kV/cm), a substantial amount of spin polarization is preserved for several microns at 300 K. However, it is also found that the spin relaxation rate increases rapidly with the drift field, scaling as the square of the electron wavevector in the direction of the field. When the electrons are injected with a high energy, a pronounced decrease is observed in the spin relaxation length due to an initial increase in the spin precession frequency. Hence, high-field or high-energy transport conditions may not be desirable for spin-based devices.Comment: 4 pages, 3 figures, one table. Scheduled for publication in the May 26, 2003 issue of Applied Physics Letters (039321APL
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