26 research outputs found
Bjorken sum rule with analytic coupling at low Q2 values
The experimental data obtained for the polarized Bjorken sum rule
\Gamma^{(p-n)}_1(Q^2) for small values of Q2 are approximated by the
predictions obtained in the framework of analytic QCD up to the 5th order
perturbation theory, whose coupling constant does not contain the Landau pole.
We found an excellent agreement between the experimental data and the
predictions of analytic QCD, as well as a strong difference between these data
and the results obtained in the framework of standard QCD.Comment: 9 pages, 1 figur
Level spacing distribution of pseudointegrable billiard
In this paper, we examine the level spacing distribution of the
rectangular billiard with a single point-like scatterer, which is known as
pseudointegrable. It is shown that the observed is a new type, which is
quite different from the previous conclusion. Even in the strong coupling
limit, the Poisson-like behavior rather than Wigner-like is seen for ,
although the level repulsion still remains in the small region. The
difference from the previous works is analyzed in detail.Comment: 11 pages, REVTeX file, 3 PostScript Figure
Spectral properties of quantized barrier billiards
The properties of energy levels in a family of classically pseudointegrable
systems, the barrier billiards, are investigated. An extensive numerical study
of nearest-neighbor spacing distributions, next-to-nearest spacing
distributions, number variances, spectral form factors, and the level dynamics
is carried out. For a special member of the billiard family, the form factor is
calculated analytically for small arguments in the diagonal approximation. All
results together are consistent with the so-called semi-Poisson statistics.Comment: 8 pages, 9 figure
Slow relaxation in weakly open vertex-splitting rational polygons
The problem of splitting effects by vertex angles is discussed for
nonintegrable rational polygonal billiards. A statistical analysis of the decay
dynamics in weakly open polygons is given through the orbit survival
probability. Two distinct channels for the late-time relaxation of type
1/t^delta are established. The primary channel, associated with the universal
relaxation of ''regular'' orbits, with delta = 1, is common for both the closed
and open, chaotic and nonchaotic billiards. The secondary relaxation channel,
with delta > 1, is originated from ''irregular'' orbits and is due to the
rationality of vertices.Comment: Key words: Dynamics of systems of particles, control of chaos,
channels of relaxation. 21 pages, 4 figure
Spin chains from super-models
We construct and study a class of N particle supersymmetric Hamiltonians with
nearest and next-nearest neighbor inverse-square interaction in one dimension.
We show that inhomogeneous XY models in an external non-uniform magnetic field
can be obtained from these super-Hamiltonians in a particular limit decoupling
the fermionic degrees of freedom from the kinematic ones. We further consider a
suitable deformation of these super-models such that inhomogeneous XXZ
Hamiltonians in an external non-uniform magnetic field are obtained in the same
limit. We show that this deformed Hamiltonian with rational potential is, (i)
mapped to a set of free super-oscillators through a similarity transformation
and (ii) supersymmetric in terms of a new, non-standard realization of the
supercharge. We construct many exact eigenstates of this Hamiltonian and
discuss about the applicability of this technique to other models.Comment: 36 pages, RevTeX, No figures, v1; Corrected typos, Added minor
clarifications, v2; Added discussions, version to appear in JPSJ, v