4,100 research outputs found

### A convenient criterion under which Z_2-graded operators are Hamiltonian

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

Estimates of lifetimes and partial branching ratios for the baryons
$\Xi_{bc}^{+}$ and $\Xi_{bc}^{0}$ 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

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 $U_{q} s\ell(2|1)$ and quantum walled Brauer algebra

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

### Electron Spin Relaxation under Drift in GaAs

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

### Gold-plated Mode of CP-Violation in Decays of B_c Meson from QCD Sum Rules

The model-independent method based on the triangle ideology is implemented to
extract the CKM-matrix angle gamma in the decays of doubly heavy long-lived
meson B_c. We analyze a color structure of diagrams and conditions to
reconstruct two reference-triangles by tagging the flavor and CP eigenstates of
D^0 meson in the fixed exclusive channels. The characteristic branching ratios
are evaluated in the framework of QCD sum rules.Comment: 11 pages, RevTeX4 file, 4 eps-figure

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