arXiv subjects

F. Zamani

Publications and source records attributed to F. Zamani.

6 recordsLinked to original sources

arXiv2016

Discrete-time analysis of traveling wave solutions and steady-state of PASEP with open boundaries

We consider the dynamics of a single shock in a partially asymmetric simple exclusion process (PASEP) on a finite lattice with open boundaries in the sublattice-parallel updating scheme. We then construct the steady state of the system by considering a linear superposition of these shocks. It is shown that this steady state can also be written in terms of a product of four non- commuting matrices. One of the main results obtained here is that these matrices have exactly the same generic structure as the matrices first introduced in Jafarpour and Masharian (2009 Phys. Rev. E 79 051124) indicating that the steady state of a one-dimensional driven-diffusive system can be written as a linear superposition of product shock measures. It is now easy to explain the two-dimensional matrix representation of the PASEP with parallel dynamics introduced in Essler and Rittenberg (1996 J. Phys. A: Math. Gen. 29 3375) and Honecker and Peschel (1997 J. Stat. Phys. 88 319).

cond-mat.stat-mech↗

arXiv2015

Steady-state dynamics and effective temperatures of quantum criticality in an open system

We study the thermal and non-thermal steady state scaling functions and the steady-state dynamics of a model of local quantum criticality. The model we consider, i.e. the pseudogap Kondo model, allows us to study the concept of effective temperatures near fully interacting as well as weak-coupling fixed points. In the vicinity of each fixed point we establish the existence of an effective temperature --different at each fixed point-- such that the equilibrium fluctuation-dissipation theorem is recovered. Most notably, steady-state scaling functions in terms of the effective temperatures coincide with the equilibrium scaling functions. This result extends to higher correlation functions as is explicitly demonstrated for the Kondo singlet strength. The non-linear charge transport is also studied and analyzed in terms of the effective temperature.

cond-mat.str-el↗

arXiv2006

Quantum Mechanics of Klein-Gordon Fields II: Relativistic Coherent States

We use the formulation of the quantum mechanics of first quantized Klein-Gordon fields given in the first of this series of papers to study relativistic coherent states. In particular, we offer an explicit construction of coherent states for both charged and neutral (real) free Klein-Gordon fields as well as for charged fields interacting with a constant magnetic field. Our construction is free from the problems associated with charge-superselection rule that complicated the previous studies. We compute various physical quantities associated with our coherent states and present a detailed investigation of their classical (nonquantum) and nonrelativistic limits.

quant-ph↗

arXiv2006

Quantum Mechanics of Klein-Gordon Fields I: Hilbert Space, Localized States, and Chiral Symmetry

We derive an explicit manifestly covariant expression for the most general positive-definite and Lorentz-invariant inner product on the space of solutions of the Klein-Gordon equation. This expression involves a one-parameter family of conserved current densities J_a^μ, with a\in(-1,1), that are analogous to the chiral current density for spin half fields. The conservation of J_a^μis related to a global gauge symmetry of the Klein-Gordon fields whose gauge group is U(1) for rational a and the multiplicative group of positive real numbers for irrational a. We show that the associated gauge symmetry is responsible for the conservation of the total probability of the localization of the field in space. This provides a simple resolution of the paradoxical situation resulting from the fact that the probability current density for free scalar fields is neither covariant nor conserved. Furthermore, we discuss the implications of our approach for free real scalar fields offering a direct proof of the uniqueness of the relativistically invariant positive-definite inner product on the space of real Klein-Gordon fields. We also explore an extension of our results to scalar fields minimally coupled to an electromagnetic field.

quant-ph↗

arXiv2004

Mid-Infrared Radiation as a Short-Term Earthquake Precursor

Recently it has been found by F. Freund that the granite under high pressure undergoes a phase transition from insulator to a p-type semiconductor. This phase transition is a key concept to understanding pre-earthquake phenomena. This effect accompanies with the radiation of the granite in the mid-infrared region. we were able to predict the recent earthquake in the south of Iran by monitoring this radiation.

physics.geo-ph↗

arXiv2003

Conserved Current Densities, Localization Probabilities, and a New Global Gauge Symmetry of Klein-Gordon Fields

For free Klein-Gordon fields, we construct a one-parameter family of conserved current densities $J_a^μ$, with $a\in(-1,1)$, and use the latter to yield a manifestly covariant expression for the most general positive-definite and Lorentz-invariant inner product on the space of solutions of the Klein-Gordon equation. Employing a recently developed method of constructing the Hilbert space and observables for Klein-Gordon fields, we then obtain the probability current density ${\cal J}_a^μ$ for the localization of a Klein-Gordon field in space. We show that in the nonrelativistic limit both $J_a^μ$ and ${\cal J}_a^μ$ tend to the probability current density for the localization of a nonrelativistic free particle in space, but that unlike $J_a^μ$ the current density ${\cal J}_a^μ$ is neither covariant nor conserved. Because the total probability may be obtained by integrating either of these two current densities over the whole space, the conservation of the total probability may be viewed as a consequence of the local conservation of $J_a^μ$. The latter is a manifestation of a previously unnoticed global gauge symmetry of the Klein-Gordon fields. The corresponding gauge group is U(1) if the parameter $a$ is rational. It is the multiplicative group of positive real numbers if $a$ is irrational. We also discuss an extension of our results to Klein-Gordon fields minimally coupled to an electromagnetic field.

quant-ph↗