2,111 research outputs found
Thermodynamics of the one-dimensional SU(4) symmetric spin-orbital model
The ground state properties and the thermodynamics of the one-dimensional
SU(4) symmetric spin system with orbital degeneracy are investigated using the
quantum Monte Carlo loop algorithm. The spin-spin correlation functions exhibit
a 4-site periodicity, and their low temperature behavior is controlled by two
correlation lengths that diverge like the inverse temperature, while the
entropy is linear in temperature and its slope is consistent with three gapless
modes of velocity . The physical implications of these results are
discussed.Comment: 4 pages, 4 figures, RevTe
RR LYRAE VARIABLE STARS: PULSATIONAL CONSTRAINTS RELEVANT TO THE OOSTERHOFF CONTROVERSY
A solution to the old Oosterhoff controversy is proposed on the basis of a
new theoretical pulsational scenario concerning RR Lyrae cluster variables
(Bono and coworkers). We show that the observed constancy of the lowest
pulsation period in both Oosterhoff type I (OoI) and Oosterhoff type II (OoII)
prototypes (M3, M15) can be easily reproduced only by assuming the canonical
evolutionary horizontal-branch luminosity levels of these Galactic globular
clusters and therefore by rejecting the Sandage period shift effect (SPSE).Comment: postscript file of 7 pages and 2 figures; one non postcript figure is
available upon request; for any problem please write to
[email protected]
X-Ray Resonant Scattering as a Direct Probe of Orbital Ordering in Transition-Metal Oxides
X-ray resonant scattering at the K-edge of transition metal oxides is shown
to measure the orbital order parameter, supposed to accompany magnetic ordering
in some cases. Virtual transitions to the 3d-orbitals are quadrupolar in
general. In cases with no inversion symmetry, such as VO, treated in
detail here, a dipole component enhances the resonance. Hence, we argue that
the detailed structure of orbital order in VO is experimentally
accessible.Comment: LaTex using RevTex, 4 pages and two included postscript figure
Multifractality: generic property of eigenstates of 2D disordered metals.
The distribution function of local amplitudes of eigenstates of a
two-dimensional disordered metal is calculated. Although the distribution of
comparatively small amplitudes is governed by laws similar to those known from
the random matrix theory, its decay at larger amplitudes is non-universal and
much slower. This leads to the multifractal behavior of inverse participation
numbers at any disorder. From the formal point of view, the multifractality
originates from non-trivial saddle-point solutions of supersymmetric
-model used in calculations.Comment: 4 two-column pages, no figures, submitted to PRL
The role of the central limit theorem in the heterogeneous ensemble of Brownian particles approach
The central limit theorem (CLT) and its generalization to stable distributions have been widely described in literature. However, many variations of the theorem have been defined and often their applicability in practical situations is not straightforward. In particular, the applicability of the CLT is essential for a derivation of heterogeneous ensemble of Brownian particles (HEBP). Here, we analyze the role of the CLT within the HEBP approach in more detail and derive the conditions under which the existing theorems are valid
Low-energy sector of the S=1/2 Kagome antiferromagnet
Starting from a modified version of the the S=1/2 Kagome antiferromagnet to
emphasize the role of elementary triangles, an effective Hamiltonian involving
spin and chirality variables is derived. A mean-field decoupling that retains
the quantum nature of these variables is shown to yield a Hamiltonian that can
be solved exactly, leading to the following predictions: i) The number of low
lying singlet states increase with the number of sites N like 1.15 to the power
N; ii) A singlet-triplet gap remains in the thermodynamic limit; iii) Spinons
form boundstates with a small binding energy. By comparing these properties
with those of the regular Kagome lattice as revealed by numerical experiments,
we argue that this description captures the essential low energy physics of
that model.Comment: 4 pages including 3 figure
Epoxy/ graphene nanocomposites – processing and properties: a review
Graphene has recently attracted significant academic and industrial interest because of its excellent performance in mechanical, electrical and thermal applications. Graphene can significantly improve physical properties of epoxy at extremely small loading when incorporated appropriately. Herein, the structure, preparation and properties of epoxy/graphene nanocomposites are reviewed in general, along with detailed examples drawn from the key scientific literature. The modification of graphene and the utilization of these materials in the fabrication of nanocomposites with different processing methods have been explored. This review has been focused on the processing methods and mechanical, electrical, thermal, and fire retardant properties of the nanocomposites. The synergic effects of graphene and other fillers in epoxy matrix have been summarised as well
Action for IIB Supergravity in 10 dimensions
We review the construction of a manifestly covariant, supersymmetric and
SL(2R) invariant action for IIB supergravity in D=10.Comment: 9 pages, LaTeX, Talk given at "Quantum Aspects of Gauge Theories,
Supersymmetry and Unification", Greece, September 199
Causally consistent reversible choreographies: a monitors-as-memories approach
Under a reversible semantics, computation steps can be undone. This paper addresses the integration of reversible semantics into a process model of multiparty protocols (choreographies). Building upon the monitors-as-memories approach that we developed in prior work for reversible binary protocols, we present a reversible process framework for multiparty communication, which improves on prior models by seamlessly integrating asynchrony, decoupled rollbacks, and process passing. As main technical result, we prove that our multiparty, reversible semantics is causally-consistent
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