12,402 research outputs found
A new non-perturbative approach to Quantum Brownian Motion
Starting from the Caldeira-Leggett (CL) model, we derive the equation
describing the Quantum Brownian motion, which has been originally proposed by
Dekker purely from phenomenological basis containing extra anomalous diffusion
terms. Explicit analytical expressions for the temperature dependence of the
diffusion constants are derived. At high temperatures, additional momentum
diffusion terms are suppressed and classical Langivin equation can be recovered
and at the same time positivity of the density matrix(DM) is satisfied. At low
temperatures, the diffusion constants have a finite positive value, however,
below a certain critical temperature, the Master Equation(ME) does not satisfy
the positivity condition as proposed by Dekker.Comment: 5 page
The Quantum Effective Mass Hamilton-Jacobi Problem
In this article, the quantum Hamilton- Jacobi theory based on the position
dependent mass model is studied. Two effective mass functions having different
singularity structures are used to examine the Morse and Poschl- Teller
potentials. The residue method is used to obtain the solutions of the quantum
effective mass- Hamilton Jacobi equation. Further, it is shown that the
eigenstates of the generalized non-Hermitian Swanson Hamiltonian for Morse and
Poschl-Teller potentials can be obtained by using the Riccati equation without
solving a differential equation
Dynamical order, disorder and propagating defects in homogeneous system of relaxation oscillators
Reaction-diffusion (RD) mechanisms in chemical and biological systems can
yield a variety of patterns that may be functionally important. We show that
diffusive coupling through the inactivating component in a generic model of
coupled relaxation oscillators give rise to a wide range of spatio-temporal
phenomena. Apart from analytically explaining the genesis of anti-phase
synchronization and spatially patterned oscillatory death regimes in the model
system, we report the existence of a chimera state, characterized by spatial
co-occurrence of patches with distinct dynamics. We also observe propagating
phase defects in both one- and two-dimensional media resembling persistent
structures in cellular automata, whose interactions may be used for computation
in RD systems.Comment: 6 pages, 4 figure
Two-charge small black hole entropy: String-loops and multi-strings
We investigate the inclusion of 10-dimensional string loop corrections to the
entropy function of two-charge extremal small black holes of the heterotic
string theory compactified on S^1 x T^5 and show that the entropy is given by
\pi\sqrt{a q_1 q_2+b q_1} where q_1 and q_2 are the charges with q_1 >> q_2 >>
1 and a and b are constants. Incorporating certain multi-string states into the
microstate counting, we show that the new statistical entropy is consistent
with the macroscopic scaling for one and two units of momentum (winding) and
large winding (momentum). We discuss our scaling from the point of view of
related AdS_3 central charge and counting of chiral primaries in superconformal
quantum mechanics as well.Comment: 18 page
Characterization of the cyclic behavior of dry masonry joints
Dry masonry mechanics received little attention from research community, when compared with resources invested in traditional (mortar joint) masonry. Nevertheless, a large number of historical stone constructions use dry masonry joints, while, in constructions originally built with weak lime mortar, mortar deterioration leads to a behavior similar to dry masonry. Therefore, the objective of this paper is to contribute to the knowledge of the behavior of dry masonry joints under cyclic loading, which is a key aspect for seismic actions.
The work focuses on the characterization of Coulomb failure criterion and the load-displacement behavior of dry masonry joints under cyclic loading, including aspects as surface roughness, dilatancy and inelastic behavior. A displacement controlled test set-up using masonry couplets is used for this purpose. Besides providing a basis for understanding the behavior of masonry joints in tension, the experiments contribute also to the definition and parameterization of advanced non-linear numeric models
Entropy Function for Non-Extremal Black Holes in String Theory
We generalize the entropy function formalism to five-dimensional and
four-dimensional non-extremal black holes in string theory. In the near horizon
limit, these black holes have BTZ metric as part of the spacetime geometry. It
is shown that the entropy function formalism also works very well for these
non-extremal black holes and it can reproduce the Bekenstein-Hawking entropy of
these black holes in ten dimensions and lower dimensions.Comment: 19 pages, no figure, JHEP3 style, to appear in JHE
Non-isospectrality of the generalized Swanson Hamiltonian and harmonic oscillator
The generalized Swanson Hamiltonian with , can be transformed into an equivalent Hermitian Hamiltonian
with the help of a similarity transformation. It is shown that the equivalent
Hermitian Hamiltonian can be further transformed into the harmonic oscillator
Hamiltonian so long as constant. However, the
main objective of this paper is to show that though the commutator of
and is constant, the generalized Swanson
Hamiltonian is not necessarily isospectral to the harmonic oscillator. Reason
for this anomaly is discussed in the frame work of position dependent mass
models by choosing as the inverse square root of the mass function.Comment: Accepted in Journal of Physics A. Comments are welcom
Simple theory of extremely overdoped HTS
We demonstrate the existence of a simple physical picture of
superconductivity for extremely overdoped CuO2 planes. It possesses all
characteristic features of HTS, such as a high superconducting transition
temperature, the symmetry of order parameter, and the
coexistence of a single electron Fermi surface and a pseudogap in the normal
state. Values of pseudogap are calculated for different doping levels. An
orbital paramagnetism of preformed pairs is predicted.Comment: 7 pages, 1 figur
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