1,600 research outputs found
Generalized partition functions and interpolating statistics
We show that the assumption of quasiperiodic boundary conditions (those that
interpolate continuously periodic and antiperiodic conditions) in order to
compute partition functions of relativistic particles in 2+1 space-time can be
related with anyonic physics. In particular, in the low temperature limit, our
result leads to the well known second virial coefficient for anyons. Besides,
we also obtain the high temperature limit as well as the full temperature
dependence of this coefficient.Comment: 12 pages, Latex, updated and enlarged versio
Virial coefficients from 2+1 dimensional QED effective actions at finite temperature and density
From spinor and scalar 2+1 dimensional QED effective actions at finite
temperature and density in a constant magnetic field background, we calculate
the corresponding virial coefficients for particles in the lowest Landau level.
These coefficients depend on a parameter theta related to the time-component of
the gauge field, which plays an essential role for large gauge invariance. The
variation of the parameter theta might lead to an interpolation between
fermionic and bosonic virial coefficients, although these coefficients are
singular for theta=pi/2.Comment: 10 Latex pages, no figures. Version to appear in MPL
Scaling of excitations in dimerized and frustrated spin-1/2 chains
We study the finite-size behavior of the low-lying excitations of spin-1/2
Heisenberg chains with dimerization and next-to-nearest neighbors interaction,
J_2. The numerical analysis, performed using density-matrix renormalization
group, confirms previous exact diagonalization results, and shows that, for
different values of the dimerization parameter \delta, the elementary triplet
and singlet excitations present a clear scaling behavior in a wide range of
\ell=L/\xi (where L is the length of the chain and \xi is the correlation
length). At J_2=J_2c, where no logarithmic corrections are present, we compare
the numerical results with finite-size predictions for the sine-Gordon model
obtained using Luscher's theory. For small \delta we find a very good agreement
for \ell > 4 or 7 depending on the excitation considered.Comment: 4 pages, 4 eps figures, RevTeX 4 class, same version as in PR
FFLO oscillations and magnetic domains in the Hubbard model with off-diagonal Coulomb repulsion
We observe the effect of non-zero magnetization m onto the superconducting
ground state of the one dimensional repulsive Hubbard model with correlated
hopping X. For t/2 < X < 2t/3, the system first manifests
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) oscillations in the pair-pair
correlations. For m = m1 a kinetic energy driven macroscopic phase separation
into low-density superconducting domains and high-density polarized walls takes
place. For m > m2 the domains fully localize, and the system eventually becomes
a ferrimagnetic insulator.Comment: IOP RevTeX class, 18 pages, 13 composite *.eps figure
Pion and Vector Meson Form Factors in the Kuperstein-Sonnenschein holographic model
We study phenomenological aspects of the holographic model of chiral symmetry
breaking recently introduced by Kuperstein and Sonnenschein (KS). As a first
step, we calculate the spectrum of vector and axial-vector mesons in the KS
model. We numerically compute various coupling constants of the mesons and
pions. Our analysis indicates that vector meson dominance is realized in this
model. The pion, vector meson and axial-vector meson form factors are obtained
and studied in detail. We find good agreement with QCD results. In particular,
the pion form factor closely matches available experimental data.Comment: v1: 27 pages, 9 figures, 4 tables; v2: minor changes, added more
general discussion of vector meson dominance; v3: minor changes and
additions, version accepted for publication in JHE
Scattering and Bound State Green's Functions on a Plane via so(2,1) Lie Algebra
We calculate the Green's functions for the particle-vortex system, for two
anyons on a plane with and without a harmonic regulator and in a uniform
magnetic field. These Green's functions which describe scattering or bound
states (depending on the specific potential in each case) are obtained exactly
using an algebraic method related to the SO(2,1) Lie group. From these Green's
functions we obtain the corresponding wave functions and for the bound states
we also find the energy spectra.Comment: 21 Latex pages. Typos corrected. Results unchanged. Version to appear
in JM
Entangling operations and their implementation using a small amount of entanglement
We study when a physical operation can produce entanglement between two
systems initially disentangled. The formalism we develop allows to show that
one can perform certain non-local operations with unit probability by
performing local measurement on states that are weakly entangled.Comment: 4 pages, no figure
Efficiency of informational transfer in regular and complex networks
We analyze the process of informational exchange through complex networks by
measuring network efficiencies. Aiming to study non-clustered systems, we
propose a modification of this measure on the local level. We apply this method
to an extension of the class of small-worlds that includes {\it declustered}
networks, and show that they are locally quite efficient, although their
clustering coefficient is practically zero. Unweighted systems with small-world
and scale-free topologies are shown to be both globally and locally efficient.
Our method is also applied to characterize weighted networks. In particular we
examine the properties of underground transportation systems of Madrid and
Barcelona and reinterpret the results obtained for the Boston subway network.Comment: 10 pages and 9 figure
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