arXiv subjects

Kurosh Javidan

Publications and source records attributed to Kurosh Javidan.

At least 19 recordsLinked to original sources

arXiv2025

Kink dynamics in a high-order field model

We study various properties of topological solitons (kinks) of a field-theoretic model with a polynomial potential of the twelfth degree. This model is remarkable in that it has several topological sectors, in which kinks have different masses. We obtain asymptotic estimates for the kink-antikink and antikink-kink interaction forces. We also study numerically kink-antikink and antikink-kink collisions and observe a number of interesting phenomena: annihilation of a kink-antikink pair in one topological sector and the production in its place of a pair in another sector; resonance phenomena -- escape windows, despite the absence of vibrational modes in the kink excitation spectra.

nlin.PS↗

arXiv2025

Impact of momentum-dependent drag coefficient on energy loss of charm and bottom quarks in QGP

This paper investigates the influence of heavy-quark momentum on their interaction rate and the resulting drag coefficient in a quark-gluon plasma. To go beyond simplified treatments, we introduce a phenomenological extension of the drag coefficient by expressing the energy loss coefficients as polynomial expansions of momentum, thereby providing a flexible framework to test the sensitivity of heavy-quark observables to additional momentum dependence in transport coefficients. Furthermore, the effects of particle momentum on radiative and collisional energy loss are determined more accurately. The study focuses on calculating the nuclear modification factor ($R_{AA}$) of charm and bottom quarks in Pb-Pb collisions at $\sqrt{S_{NN}} = 5.02 \: TeV$. The initial distribution functions are evolved numerically using the Fokker-Planck equation. The results are compared with the latest experimental data from ALICE and ATLAS, collected in 2021 and 2022.

hep-ph↗

arXiv2025

Photon Blockade in Cavity Magnomechanical Systems using Phase-Controlled Feedback

In this paper, we optimize photon blockade in a cavity magnomechanical system using feedback by introducing optimized values for the phase and magnetic field coupling strength at each drive frequency. It is shown that the computed values significantly reduce the photon second-order correlation function in the dynamic Schrodinger equation. The Radau method, an implicit Runge-Kutta method, has been employed, which provides more accurate results. Furthermore, we demonstrate that a frequency detuning between the magnon and photon can result in deep values of photon blockade. Utilizing these optimized parameters outperforms scenarios that rely on constant, non-optimized values. This approach provides strong potential for applications in quantum sensing and quantum computation.

quant-ph↗

arXiv2024

Kinks scattering in deformed $φ^6$ model

The deformed model $\tildeφ^{(6)}$ is introduced based on the $φ^4$ model using a deformation functional $F[φ]$ including a free parameter $a$. The kink solutions in different sectors and their internal modes are obtained as functions of the deformation parameter and their characteristics are evaluated as well. It is shown that the kinks of the deformed model inherit some of their dynamical properties (like internal modes) from the standard $φ^4$ potential and some of their characteristics from the $φ^6$ model. The dynamics of kink-antikink (antikink-kink) scattering is investigated in different sectors with various kink initial conditions as well as different values of deformation parameter. According to the kinks' initial velocity, colliding kinks may be bound together or scatter from each other after the interaction. These two situations are distinguished by the critical velocity, which itself depends on the deformation parameter of the model. Due to the difference in the rest mass of kink solutions related to different sectors, interesting and sometimes rare phenomena are observed during the kink scattering and their interactions.

nlin.PS↗

arXiv2024

Dynamics of kink train solutions in deformed Multiple sine-Gordon models

This paper examines the effects of a thin layer of inhomogeneity on periodic solutions of the Multiple-sine-Gordon (MsG) model. We investigate the dynamics of the perturbed Double-sine-Gordon (DsG) system as a significant and more practical case of such configurations. The thin barrier acts as a potential well (potential barrier) and causes critical deformations in kink train solutions and some basic properties of the periodic solutions, such as the type of sub-kinks, their amplitude, energy and wavelength. Stability of the initial kink chain during the interaction with medium defects is analyzed using their phase diagram. Sudden changes in the profile of kink trains due to the disruption of their amplitude and wavelength are considered. The time evolution of moving kink chain solutions while interacting with medium fractures is also studied.

nlin.PS↗

arXiv2024

A comparative study of different approaches for heavy quark energy loss, based on the latest experimental data

This paper presents a comparative analysis of three distinct methods used to calculate the collisional energy loss of heavy quarks in Quark-Gluon Plasma. The study focuses on the calculation of the nuclear suppression factor of charm quarks in Pb-Pb collisions at $\sqrt{S_{NN}} = 5.02$ TeV. All three models are examined using the same numerical evolution based on the well-known Fokker-Planck equation by considering critical phenomena like a non-equilibrium state at the onset of heavy ion collision. The outcomes of each approach are compared with the latest data from ALICE and ATLAS experiments spanning from 2018 to 2022. This study aims to compare the degree of agreement between each approach and recently obtained experimental data, in the intermediate and high $P_T$ regions.

hep-ph↗

arXiv2023

Thick branes via higher order field theory models with exponential and power-law tails

In this work, we obtain exact thick brane models in $4+1$ dimensions generated by higher order field theory kinks, inspired by specific potentials for $ϕ^{10}$ and $ϕ^{18}$ models. We verify that the geodesic equation along the fifth dimension confirms the confining effects of the scalar field on the brane for all of these models. These models provide new solutions with exponential and power-law tails which live in different topological sectors. We show that the resulting branes of specific exponential law models do not possess $Z_2$-symmetry. Furthermore, we examine the stability of the thick branes, by determining the sign of the $w^2$ term in the expansion of the potential for the resulting Schrödinger-like equation. It turns out that two of the three models of the $ϕ^{10}$ brane are stable, while another contains unstable modes for certain ranges of the model parameters. We also show that the brane solution from the specific $ϕ^{18}$ models are stable, while the others involve neutral equilibrium. The asymptotic behaviour of the brane solutions are also discussed.

gr-qc↗

arXiv2021

Exotic Final States in the $φ^8$ Multi-Kink Collisions

We study final states in the scattering of kinks and antikinks of the $φ^8$ field-theoretic model. We use the initial conditions in the form of two, three or four static or moving kinks. In the numerical experiments we observe a number of different processes such as emergence of static and moving oscillons, change of the kink's topological sector, scattering of an oscillon by a kink, production of kink-antikink pairs in oscillon-oscillon collisions. In antikink-kink collisions for asymmetric kinks, we found resonance phenomena -- escape windows.

hep-th↗

arXiv2020

Fast and efficient deterministic quantum state transfer between two remote mechanical resonators

The main challenge in deterministic quantum state transfer in long-distance quantum communications is the transmission losses in the communication channel. To overcome this limitation, here we use the adiabatic theorem and find a lossless evolution path between two remote mechanical modes. By adiabatic variation of the effective coupling strengths between the two nodes and the intermediate optical channel modes, we engineer a transmission path for the quantum state transfer that is decoupled from the decaying fiber modes. Using our proposed method we show that one obtains a quantum state transfer with high efficiency. Furthermore, to bypass the slow nature of the adiabatic process and its sensitivity to the mechanical damping and noise as well as the strength of the driving pulses, we develop the shortcut to adiabatic passage protocol for our proposed quantum state transfer. Our results show that the shortcut to adiabaticity provides an efficient and fast quantum state transfer even for small values of the coupling strength. We show that the performance of our protocol for long-distance quantum communications remains efficient for transferring the quantum states between two remote mechanical resonators being hundred meters apart.

quant-ph↗

arXiv2020

Three-Spin Systems and the Pusey-Barrett- Rudolph Theorem

The fundamental nature of quantum wave function has been the topic of many discussions since the beginning of the quantum theory. It either corresponds to an element of reality $(Ψ-ontic)$ or it is a subjective state of knowledge about the underlying reality $(Ψ-epistemic)$. Pusey, Barrett, and Rudolph (PBR) have shown that epistemic interpretations of the quantum wave function are in contradiction with the predictions of quantum under some assumptions. In this paper, a laboratory protocol with a triple quantum dot will be introduced as a three-spin interaction system to study the PBR no-go theorem. By this experimental model, we show that the epistemic interpretation of the quantum state is in contradiction with quantum theory, based only on the assumption that measurement settings can be prepared freely and independently from each other.

quant-ph↗

arXiv2020

A Modified Dynamical Model of Cosmology I. Theory

Wheeler (1964) had formulated Mach's principle as the boundary condition for general relativistic field equations. Here, we use this idea and develop a modified dynamical model of cosmology based on imposing Neumann boundary condition on cosmological perturbation equations. Then, it is shown that a new term appears in the equation of motion, which leads to a modified Poisson equation. In addition, a modified Hubble parameter is derived due to the presence of the new term. Moreover, it is proved that, without a cosmological constant, such a model has a late time-accelerated expansion with an equation of state converging to $w < -1$. Also, the luminosity distance in the present model is shown to differ from that of the $ΛCDM$ model at high redshifts. Furthermore, it is found that the adiabatic sound speed squared is positive in radiation-dominated era and then converges to zero at later times. Theoretical implications of the Neumann boundary condition have been discussed, and it is shown that, by fixing the value of the conjugate momentum (under certain conditions), one could derive a similar version of modified dynamics. In a future work, we will confine the free parameters of the Neumann model based on hype Ia Supernovae, Hubble parameter data, and the age of the oldest stars.

gr-qc↗

arXiv2019

Entanglement Fidelity Ratio for Elastic Collisions in Non-Ideal Two-Temperature Dense Plasma

The quantum diffraction and symmetry effects on the entanglement fidelity (EF) of different elastic electron-electron, ion-ion and electron-ion interactions are investigated in non-ideal dense plasma. The partial wave analysis and an effective screened interaction potential including quantum mechanical diffraction and symmetry effects are employed to obtain the EF in a non-ideal dense plasma. We show that collision energy and temperatures of electron and ion have a destroying role in the entanglement. In fact, by decreasing the temperature of any kind of particles, the quantum effects become dominant and the entanglement grows up. Also, increase in the density of plasma leads to the enhancement of entanglement ratio.

physics.plasm-ph↗

arXiv2018

Phenomenology of leading nucleon production in $ep$ collisions at HERA in the framework of fracture functions

In recent years, several experiments at the $e^-p$ collider HERA have collected high precision deep inelastic scattering (DIS) data on the spectrum of leading nucleon carrying a large fraction of the proton's energy. In this paper, we have analyzed recent experimental data on the production of forward proton and neutron in DIS at HERA in the framework of a perturbative QCD. We propose a technique based on the fractures functions framework, and extract the nucleon fracture functions (nucleon FFs) ${\cal M}_2^{(n/p)} (x, Q^2; x_L)$ from global QCD analysis of DIS data measured by ZEUS collaboration at HERA. We have shown that an approach based on the fracture functions formalism allows us phenomenologically parametrize the nucleon FFs. Considering both leading neutron as well as leading proton production data at HERA, we present the results for the separate parton distributions for all parton species, including valence quark densities, the anti-quark densities, the strange sea distribution, and the gluon distribution functions. We proposed several parameterizations for the nucleon FFs and open the possibility of these asymmetries. The obtained optimum set of nucleon FFs is accompanied by Hessian uncertainty sets which allow one to propagate uncertainties to other observables interest. The extracted results for the $t$-integrated leading neutron $F_2^{\rm LN(3)} (x, Q^2; x_L)$ and leading proton $F_2^{\rm LP(3)} (x, Q^2; x_L)$ structure functions are in good agreement with all data analyzed, for a wide range of fractional momentum variable $x$ as well as the longitudinal momentum fraction $x_L$.

hep-ph↗

arXiv2017

Magnetohydrodynamic equations for cold quark gluon plasmas: Multi fluidity and Solitary wave stability

By means of magnetohydrodynamic equations in a non relativistic multi fluid framework, we study the behavior of small amplitude perturbations in cold Quark Gluon Plasmas (QGP). Magnetohydrodynamic equations, along with the QGP equation of state are expanded using the reductive perturbation method. It is shown that such a medium should be considered as multi fluid magnetohydrodynamic (MHD) system. The result is a nonlinear wave equation which complies with a modified form of the "derivative nonlinear Schrodinger" equation instead of the KdV equation. We show that the complete set of equations, by considering the magnetic field which is supported by the Maxwell's equations, create stable solitary waves. An interesting result is the existence of an electric field component along the direction of magnetic field which causes charge separability in the medium. Properties of this solitonic solution is studied by considering different values for the QGP characters such as background mass density and strength of the magnetic field (at the scale of compact stars).

hep-th↗

arXiv2017

Global analysis on determination of fracture functions considering sea quark asymmetries in the nucleon

Several experiments at the electron-proton ($ep$) collider HERA have collected high precision data on the spectrum of leading-proton and leading-neutron carrying a large fraction of the proton's energy. In this paper, we have analyzed recent experimental data on the production of leading-nucleon in deep inelastic scattering (DIS) processes at HERA in the framework of a perturbative QCD (pQCD). An approach based on the fractures functions framework has been used, and the nucleon fracture functions (nucleon FFs) ${\cal M}_2^{(n/p)} (x, Q^2, x_L)$ have been extracted from global QCD analysis of DIS data measured by ZEUS collaboration at HERA. We show that the approach of fracture functions formalisem allows us phenomenologically parametrize the nucleon FFs at the input scale, $Q_0^2$. Considering leading-nucleon production data in the DIS processes, we present the results for the separate parton distributions for all parton species. The extracted results from the $t$-integrated leading-baryon fracture functions, $F_2^{\rm LB(3)} (x, Q^2, x_L)$ are in good agreement with all DIS data analyzed, for a wide range of longitudinal momentum fraction $x_L$ as well as scaled fractional momentum variable $x$.

hep-ph↗

arXiv2017

QCD analysis of leading-neutron production at HERA: Determination of neutron fracture functions

The last two decades have seen a growing trend towards the experimental efforts at the electron-proton collider HERA in which have collected high precision data on the spectrum of leading neutron (LN) and leading-proton (LP) carrying a large fraction of the proton's energy. In our recent study [Phys. Rev. D \textbf{95} (2017), 074011], we have proposed an approach based on the Fractures Functions (FF) formalism and have extracted the neutron Fracture Functions (neutron FFs) from a global QCD analysis of LN production data measured by H1 and ZEUS collaborations at HERA. We have shown that considering the approach based on the framework of Fracture Functions, one could phenomenologically parametrize the neutron FFs at the input scale. In order to access the uncertainties for the obtained neutron FFs as well as the LN structure functions and cross section, associated with the uncertainties in the data, we have made an extensive use of the "Hessian method". Our theory predictions based on the obtained neutron FFs are in satisfactory agreement with all LN data analyzed, for a wide range of $β$ and $x_L$.

hep-ph↗

arXiv2017

Multi-kink collisions in the $ϕ^6$ model

We study simultaneous collisions of two, three, and four kinks and antikinks of the $ϕ^6$ model at the same spatial point. Unlike the $ϕ^4$ kinks, the $ϕ^6$ kinks are asymmetric and this enriches the variety of the collision scenarios. In our numerical simulations we observe both reflection and bound state formation depending on the number of kinks and on their spatial ordering in the initial configuration. We also analyze the extreme values of the energy densities and the field gradient observed during the collisions. Our results suggest that very high energy densities can be produced in multi-kink collisions in a controllable manner. Appearance of high energy density spots in multi-kink collisions can be important in various physical applications of the Klein-Gordon model.

hep-th↗

arXiv2017

Determination of neutron fracture functions from a global QCD analysis of leading neutron production at HERA

In this article, we present our global QCD analysis of leading neutron production in deep inelastic scattering at H1 and ZEUS collaborations. The analysis is performed in the framework of a perturbative QCD description for semi-inclusive processes which is based on the fracture functions approach. Modeling the non-perturbative part of the fragmentation process at the input scale Q$_0^2$, we analyze the Q$^2$-dependence of the leading neutron structure functions and obtain the neutron fracture functions (neutron FFs) from next-to-leading order (NLO) global QCD fit to data. We have also performed a careful estimation of the uncertainties using the "Hessian method" for the neutron FFs and corresponding observables originating from experimental errors. The predictions based on the obtained neutron FFs are in good agreement with all data analyzed, at small and large longitudinal momentum fraction $x_L$ as well as the scaled fractional momentum variable $β$.

hep-ph↗