199 research outputs found
Nonequilibrium Microscopic Distribution of Thermal Current in Particle Systems
A nonequilibrium distribution function of microscopic thermal current is
studied by a direct numerical simulation in a thermal conducting steady state
of particle systems. Two characteristic temperatures of the thermal current are
investigated on the basis of the distribution. It is confirmed that the
temperature depends on the current direction; Parallel temperature to the
heat-flux is higher than antiparallel one. The difference between the parallel
temperature and the antiparallel one is proportional to a macroscopic
temperature gradient.Comment: 4 page
Deformation of Schild String
We attempt to construct new superstring actions with a -plet of Majorana
fermions , where is the dimensional space-time
index and is the two dimensional spinor index, by deforming the Schild
action. As a result, we propose three kinds of actions: the first is invariant
under N=1 (the world-sheet) supersymmetry transformation and the
area-preserving diffeomorphism. The second contains the Yukawa type
interaction. The last possesses some non-locality because of bilinear terms of
. The reasons why completing a Schild type superstring action
with is difficult are finally discussed.Comment: 12 pages, Latex, both title and abstract are changed, discussion of
some relations among our results, Nambu-Goto string and super Yang-Mills
theories, added. Results unchange
Divergent Thermal Conductivity in Three-dimensional Nonlinear lattices
Heat conduction in three-dimensional nonlinear lattices is investigated using
a particle dynamics simulation. The system is a simple three-dimensional
extension of the Fermi-Pasta-Ulam (FPU-) nonlinear lattices, in
which the interparticle potential has a biquadratic term together with a
harmonic term. The system size is , and the heat is made to
flow in the direction the Nose-Hoover method. Although a linear
temperature profile is realized, the ratio of enerfy flux to temperature
gradient shows logarithmic divergence with . The autocorrelation function of
energy flux is observed to show power-law decay as ,
which is slower than the decay in conventional momentum-cnserving
three-dimensional systems (). Similar behavior is also observed in
the four dimensional system.Comment: 4 pages, 5 figures. Accepted for publication in J. Phys. Soc. Japan
Letter
Higher Derivative Corrections to Eleven Dimensional Supergravity via Local Supersymmetry
In this paper we derive higher derivative corrections to the eleven
dimensional supergravity by applying the Noether method with respect to the N=1
local supersymmetry. An ansatz for the higher derivative effective action,
which includes quartic terms of the Riemann tensor, is parametrized by 132
parameters. Then we show that by the requirement of the local supersymmetry,
the higher derivative effective action is essentially described by two
parameters. The bosonic parts of these two superinvariants completely match
with the known results obtained by the perturbative calculations in the type
IIA superstring theory. Since the calculations are long and systematic, we
build the computer programming to check the cancellation of the variations
under the local supersymmetry. This is an extended version of our previous
paper hep-th/0508204.Comment: 67 pages, no figure, references added, typos correcte
Self-consistency and Symmetry in d-dimensions
Bethe approximation is shown to violate Bravais lattices translational
invariance. A new scheme is then presented which goes over the one-site Weiss
model yet preserving initial lattice symmetry. A mapping to a one-dimensional
finite closed chain in an external field is obtained. Lattice topology
determines the chain size. Using recent results in percolation, lattice
connectivity between chains is argued to be where is the
coordination number and is the space dimension. A new self-consistent
mean-field equation of state is derived. Critical temperatures are thus
calculated for a large variety of lattices and dimensions. Results are within a
few percent of exact estimates. Moreover onset of phase transitions is found to
occur in the range . For the Ising hypercube it yields the Golden
number limit .Comment: 16 pages, latex, Phys. Rev. B (in press
Chameleonic dilaton, nonequivalent frames, and the cosmological constant problem in quantum string theory
The chameleonic behaviour of the String theory dilaton is suggested. Some of
the possible consequences of the chameleonic string dilaton are analyzed in
detail. In particular, (1) we suggest a new stringy solution to the
cosmological constant problem and (2) we point out the non-equivalence of
different conformal frames at the quantum level. In order to obtain these
results, we start taking into account the (strong coupling) string loop
expansion in the string frame (S-frame), therefore the so-called form factors
are present in the effective action. The correct Dark Energy scale is recovered
in the Einstein frame (E-frame) without unnatural fine-tunings and this result
is robust against all quantum corrections, granted that we assume a proper
structure of the S-frame form factors in the strong coupling regime. At this
stage, the possibility still exists that a certain amount of fine-tuning may be
required to satisfy some phenomenological constraints. Moreover in the E-frame,
in our proposal, all the interactions are switched off on cosmological length
scales (i.e. the theory is IR-free), while higher derivative gravitational
terms might be present locally (on short distances) and it remains to be seen
whether these facts clash with phenomenology. A detailed phenomenological
analysis is definitely necessary to clarify these points
Transition between phantom and non-phantom phases with time dependent cosmological constant and Cardy-Verlinde formula
We investigate the transition phenomenon of the universe between a phantom
and a non-phantom phases. Particular attention is devoted to the case in which
the cosmological constant depends on time and is proportional to the square of
the Hubble parameter. Inhomogeneous equations of state are used and the
equation of motion is solved. We find that, depending on the choice of the
input parameters, the universe can transit from the non-phantom to the phantom
phase leading to the appearance of singularities. In particular, we find that
the phantom universe ends in the singularity of type III, unlike the case
without variable cosmological constant in which the phantom phase ends
exclusively in the big rip (singularity of type I). The Cardy-Verlinde formula
is also introduced for inhomogeneous equation of state and we find that its
equivalence with the total entropy of the universe, coming from the Friedmann
equations, occurs only for special choice of the input parameter at the
present time.Comment: 12 pages, 2 figure
Casimir effect in de Sitter and Anti-de Sitter braneworlds
We discuss the bulk Casimir effect (effective potential) for a conformal or
massive scalar when the bulk represents five-dimensional AdS or dS space with
two or one four-dimensional dS brane, which may correspond to our universe.
Using zeta-regularization, the interesting conclusion is reached, that for both
bulks in the one-brane limit the effective potential corresponding to the
massive or to the conformal scalar is zero. The radion potential in the
presence of quantum corrections is found. It is demonstrated that both the dS
and the AdS braneworlds may be stabilized by using the Casimir force only. A
brief study indicates that bulk quantum effects are relevant for brane
cosmology, because they do deform the de Sitter brane. They may also provide a
natural mechanism yielding a decrease of the four-dimensional cosmological
constant on the physical brane of the two-brane configuration.Comment: 37 pages, LaTeX, references added, some revision is done, version to
appear in PR
Conserved Charges in Einstein Gauss-Bonnet theory
Using Noether's identities, we define a superpotential with respect to a
background for the Einstein Gauss-Bonnet theory of gravity. As an example, we
show that its associated conserved charge yields the mass-energy of a
D-dimensional Gauss-Bonnet black hole in an anti-de Sitter spacetime.Comment: 17 pages, LaTeX, references added, typos corrected, version to appear
in Class. Quant. Gra
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