1,311 research outputs found
Exchange interaction in quantum rings and wires in the Wigner-crystal limit
We present a controlled method for computing the exchange coupling in
correlated one-dimensional electron systems based on the relation between the
exchange constant and the pair-correlation function of spinless electrons. This
relation is valid in several independent asymptotic regimes, including low
electron density case, under the general condition of a strong spin-charge
separation. Explicit formulas for the exchange constant are obtained for thin
quantum rings and wires with realistic Coulomb interactions by calculating the
pair-correlation function via a many-body instanton approach. A remarkably
smooth interpolation between high and low electron density results is shown to
be possible. These results are applicable to the case of one-dimensional wires
of intermediate width as well. Our method can be easily generalized to other
interaction laws, such as the inverse distance squared one of the
Calogero-Sutherland-Moser model. We demonstrate excellent agreement with the
known exact results for the latter model and show that they are relevant for a
realistic experimental setup in which the bare Coulomb interaction is screened
by an edge of a two-dimensional electron gas.Comment: 12 pages, 5 figure
Absorption in Ultra-Peripheral Nucleus-Atom Collisions in Crystal
The Glauber theory description of particle- and nucleus-crystal Coulomb
interactions at high-energy is developed. The allowance for the lattice thermal
vibrations is shown to produce strong absorption effect which is of prime
importance for quantitative understanding of the coherent Coulomb excitation of
ultra-relativistic particles and nuclei passing through the crystal.Comment: 8 pages, LaTe
Quark-hadron duality for mixing
Long distance contribution to the mixing is taken into account
consistently and the corrections to the naive duality result represented by the
famous box diagram are found to be small. Estimates are given in the leading
order of the chiral perturbation theory.Comment: 11 pages, Late
corrections to the correlator of finite mass baryon currents
We present analytical next-to-leading order results for the correlator of
baryonic currents at the three loop level with one finite mass quark. We obtain
the massless and the HQET limit of the correlator from the general formula as
particular cases. We also give explicit expressions for the moments of the
spectral density.Comment: 12 pages, 2 Postscript figure
Two-loop corrections to the correlator of tensor currents in gluodynamics
Results of evaluating the leading order corrections to the
correlator of tensor currents in pure gluodynamics are presented. These
corrections to the parton result for the correlator are not large numerically
that allows one to use perturbation theory for the analysis of the resonance
spectrum within the sum rules method.Comment: 10 pages, latex, no figure
Transcendental numbers and the topology of three-loop bubbles
We present a proof that all transcendental numbers that are needed for the
calculation of the master integrals for three-loop vacuum Feynman diagrams can
be obtained by calculating diagrams with an even simpler topology, the topology
of spectacles.Comment: 4 pages in REVTeX, 1 PostScript figure included, submitted to Phys.
Rev. Let
B0 - anti-B0 mixing beyond factorization
We present a calculation of the B0 - anti-B0 mixing matrix element in the
framework of QCD sum rules for three-point functions. We compute alpha_s
corrections to a three-point function at the three-loop level in QCD
perturbation theory, which allows one to extract the matrix element with
next-to-leading order (NLO) accuracy. This calculation is imperative for a
consistent evaluation of experimentally-measured mixing parameters since the
coefficient functions of the effective Hamiltonian for B0 - anti-B0 mixing are
known at NLO. We find that radiative corrections violate factorization at NLO;
this violation is under full control and amounts to 10%.Comment: 4 pages, 3 figures, LaTeX2
Analysis of and with QCD sum rules
In this article, we calculate the masses and the pole residues of the
heavy baryons and with the QCD
sum rules. The numerical values (or
) and (or ) are in good agreement
with the experimental data.Comment: 18 pages, 18 figures, slight revisio
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