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Kurosh Javidan

Publications and source records attributed to Kurosh Javidan.

31 records · Page 2Linked to original sources
arXiv2016

High energy density spots and production of kink-antikink pairs in particle collisions

The maximal energy density that can be achieved in the collisions of the particle-like wave trains in the $ϕ^4$ model has been investigated numerically for different wave train parameters. From these results the prediction is made on how many kink-antikink pairs can be produced in wave train collisions taking into account that in collision of $N$ kinks maximal energy density is equal to $N^2/2$ for even $N$. Our numerical results are in a reasonably good agreement with the predicted maximal number of kink-antikink pairs formed in wave train collisions.

nlin.PS↗
arXiv2015

Evolution of heavy quark distribution function in quark-gluon plasma: using the Iterative Laplace Transform Method

The "Iterative Laplace Transform Method" is used to solve the Fokker-Planck equation for finding the time evolution of the heavy quarks distribution functions such as charm and bottom in quark gluon plasma. These solutions will lead us to calculation of nuclear suppression factor RAA. The results have good agreement with available experiment data from the PHENIX collaboration.

hep-ph↗
arXiv2014

Kink scattering from a parity-time-symmetric defect in the $ϕ^4$ model

In this paper, we study the $ϕ^4$ kink scattering from a spatially localized $\mathcal{PT}$-symmetric defect and the effect of the kink's internal mode (IM) is discussed. It is demonstrated that if a kink hits the defect from the gain side, a noticeable IM is excited, while for the kink coming from the opposite direction the mode excitation is much weaker. This asymmetry is a principal finding of the present work. Similar to the case of the sine-Gordon kink studied earlier, it is found that the $ϕ^4$ kink approaching the defect from the gain side always passes through the defect, while in the opposite case it must have sufficiently large initial velocity, otherwise it is trapped by the loss region. It is found that for the kink with IM the critical velocity is smaller, meaning that the kink bearing IM can pass more easily through the loss region. This feature, namely the "increased transparency" of the defect as regards the motion of the kink in the presence of IM is the second key finding of the present work. A two degree of freedom collective variable model offered recently by one of the co-authors is shown to be capable of reproducing both principal findings of the present work. A simpler, analytically tractable single degree of freedom collective variable method is used to calculate analytically the kink phase shift and the kink critical velocity sufficient to pass through the defect. Comparison with the numerical results suggests that the collective variable method is able to predict these parameters with a high accuracy.

nlin.PS↗
arXiv2013

Interaction of double sine-Gordon solitons with external potentials: an analytical model

Interaction of Double sine-Gordon solitons with a space dependent potential wall and also a potential well has been investigated by employing an analytical model based on the collective coordinate approach. The potential has been added to the model through a suitable nontrivial metric for the background space-time. The model is able to predict most of the features of the soliton-potential interaction. It is shown that a soliton can pass through a potential barrier if its velocity is greater than a critical velocity which is a function of soliton initial conditions and also characters of the potential. It is interesting that the solitons of the double sine-Gordon model can be trapped by a potential barrier and oscillate there. This situation is very important in applied physics. Soliton-well system has been investigated using the presented model too. Analytical results also have been compared with the results of the direct numerical solutions.

hep-th↗
arXiv2012

Collective-coordinate analysis of inhomogeneous nonlinear Klein-Gordon field theory

Two different sets of collective-coordinate equations for solitary solutions of Nonlinear Klein-Gordon (NKG) model is introduced. The collective-coordinate equations are derived using different approaches for adding the inhomogeneities as exrernal potentials to the soliton equation of motion. Interaction of the NKG field with a local inhomogeneity like a delta function potential wall and also delta function potential well is investigated using the presented collective-coordinate equations and the results of two different models are compared. Most of the characters of the interaction are derived analytically. Analytical results are also compared with the results of numerical simulations.

nlin.PS↗
arXiv2012

Soliton-potential interaction in the nonlinear Klein-Gordon model

The interaction of solitons with external potentials in nonlinear Klein-Gordon field theory is investigated using an improved model. The presented model has been constructed with a better approximation for adding the potential to the Lagrangian through the metric of background space-time. The results of the model are compared with another model and the differences are discussed.

nlin.PS↗
arXiv2011

Measurement-induced nonlocality for an arbitrary bipartite state

Measurement-induced nonlocality is a measure of nonlocalty introduced by Luo and Fu [Phys. Rev. Lett \textbf{106}, 120401 (2011)]. In this paper, we study the problem of evaluation of Measurement-induced nonlocality (MIN) for an arbitrary $m\times n$ dimensional bipartite density matrix $ρ$ for the case where one of its reduced density matrix, $ρ^{a}$, is degenerate (the nondegenerate case was explained in the preceding reference). Suppose that, in general, $ρ^{a}$ has $d$ degenerate subspaces with dimension $m_{i} (m_{i} \leq m, i=1, 2, ..., d)$. We show that according to the degeneracy of $ρ^{a}$, if we expand $ρ$ in a suitable basis, the evaluation of MIN for an $m\times n$ dimensional state $ρ$, is degraded to finding the MIN in the $m_{i}\times n$ dimensional subspaces of state $ρ$. This method can reduce the calculations in the evaluation of MIN. Moreover, for an arbitrary $m\times n$ state $ρ$ for which $m_{i}\leq 2$, our method leads to the exact value of the MIN. Also, we obtain an upper bound for MIN which can improve the ones introduced in the above mentioned reference. In the final, we explain the evaluation of MIN for $3\times n$ dimensional states in details.

quant-ph↗
arXiv2010

Factorization Law for Two Lower Bounds of Concurrence

We study the dynamics of two lower bounds of concurrence in bipartite quantum systems when one party goes through an arbitrary channel. We show that these lower bounds obey the factorization law similar to that of [Konrad et al., Nat. Phys. 4, 99 (2008)]. We also, discuss the application of this property, in an example.

quant-ph↗
arXiv2009

Collective coordinate variable for soliton-potential system in sine-Gordon model

A Collective coordinate variable for adding a space dependent potential to the sine-Gordon model is presented. Interaction of solitons with a delta function potential barrier and also delta function potential well is investigated. Most of the characters of interaction are derived analytically. We will find that the behaviour of a solitonic solution is like a point particle which is moved under the influence of a complicated effective potential. The effective potential is a function of the field initial conditions and also parameters of added potential.

hep-th↗
arXiv2009

Analytical formulation for soliton-potential dynamics

An analytical model for the soliton-potential interaction is presented, by constructing a collective coordinate for the system. Most of the characters of the interaction are derived analytically while they are calculated by other models numerically. We will find that the behaviour of the soliton is like a point particle living under the influence of a complicated potential which is a function of soliton velocity and the potential parameters. The analytic model does not have a clear prediction for the islands of initial velocities in which the soliton may reflect back or escape over the potential well.

hep-th↗
arXiv2008

An analytical formulation for phi^4 field-potential dynamics

An analytical model for adding a space dependent potential to the phi^4 field is presented, by constructing a collective coordinate for solitary solution of this model. Interaction of the $ϕ^{4}$ field with a delta function potential barrier and also delta function potential well is investigated. Most of the characters of the interaction are derived analytically while they are calculated by other models numerically. We will find that the behaviour of the solitary solution is like a point particle 'living' under the influence of a complicated potential which is a function of the field initial conditions and the potential parameters.

hep-th↗
arXiv2006

Interaction of topological solitons with defects: using a nontrivial metric

By including potential into the flat metric, we study interaction of sine-Gordon soliton with potentials. We will show numerically that while the soliton-barrier system shows fully classical behaviour, the soliton-well system demonstrates non-classical behaviour. In particular, solitons with low velocities are trapped in the well and emit energy radiation.

hep-th↗