Isfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Particle simulation of forward Raman instability in a low-density plasmaParticle simulation of forward Raman instability in a low-density plasma231243928FAMChaboksavarSDarvish MollaMJamshidiMRRouhaniHHakimipajouhJournal Article20191126 Propagation of Electromagnetic wave in a plasma in the equilibrium state can cause instability. Investigating the situations in which this kind of instability occurs and grows is an important issue. In this paper, Raman instability in plasma is analyzed by particle simulation method. In terms of physical investigation, plasma is a very complicated environment and experimentally too expensive. Also, when such an environment is subjected experiment, it shows nonlinear behavior. To avoid these problems, we used particle simulation method to study Raman instability. Here, we model the mentioned instability with a nonrelativistic 2D electromagnetic PIC simulation code. As plasma consists of electrons and ions, it is simulated by particle method. It is supposed that ions for having a large potential form a uniform background, although electron’s dynamic is derived from Newton-Lorentz equations. In this article, it is shown that when a plane EM wave propagates in plasma, a longitudinal wave with adequately large amplitude starts to grow, which means Raman instability has occurred. The growth rate of longitudinal wave is in agreement with the theoretical results. Charge separation and bunching are observed by particles phase space investigation, which shows the accuracy of the written code in the creation and growth of longitudinal waves. Propagation of Electromagnetic wave in a plasma in the equilibrium state can cause instability. Investigating the situations in which this kind of instability occurs and grows is an important issue. In this paper, Raman instability in plasma is analyzed by particle simulation method. In terms of physical investigation, plasma is a very complicated environment and experimentally too expensive. Also, when such an environment is subjected experiment, it shows nonlinear behavior. To avoid these problems, we used particle simulation method to study Raman instability. Here, we model the mentioned instability with a nonrelativistic 2D electromagnetic PIC simulation code. As plasma consists of electrons and ions, it is simulated by particle method. It is supposed that ions for having a large potential form a uniform background, although electron’s dynamic is derived from Newton-Lorentz equations. In this article, it is shown that when a plane EM wave propagates in plasma, a longitudinal wave with adequately large amplitude starts to grow, which means Raman instability has occurred. The growth rate of longitudinal wave is in agreement with the theoretical results. Charge separation and bunching are observed by particles phase space investigation, which shows the accuracy of the written code in the creation and growth of longitudinal waves.https://ijpr.iut.ac.ir/article_928_6e15e23b2d515b34af38959f88f4919a.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Topological description of mechanical behavior of Cu, Ag and Au: A first-principle studyTopological description of mechanical behavior of Cu, Ag and Au: A first-principle study245257929FAMSaghayezhianSJHashemifarHAkbarzadehJZarbakhshJournal Article20191126 Mechanical properties and stress-strain curves of Cu, Ag and Au single crystals are calculated using ab initio methods. Elastic and Plastic regions are scrutinized. Yield stress and slope of these curves can shed light on brittlenesss and ductility of these metals that prove Cu, despite its high ultimate tensile strength, is less ductile than Au and Ag. Analysis of topology of charge density along with stress-strain curves shows that the elastic-plastic transition accompanies topological transition and for these metals, both transitions occur in the same strain. Some charactristics of critical point, especially bond points, are inspected. Mechanical properties and stress-strain curves of Cu, Ag and Au single crystals are calculated using ab initio methods. Elastic and Plastic regions are scrutinized. Yield stress and slope of these curves can shed light on brittlenesss and ductility of these metals that prove Cu, despite its high ultimate tensile strength, is less ductile than Au and Ag. Analysis of topology of charge density along with stress-strain curves shows that the elastic-plastic transition accompanies topological transition and for these metals, both transitions occur in the same strain. Some charactristics of critical point, especially bond points, are inspected.https://ijpr.iut.ac.ir/article_929_21d4ea297fb30ab45b607d56dc0838b6.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126The vector fluctuations around the Wesson's solutionsThe vector fluctuations around the Wesson's solutions259263930FAMNadiFLoranJournal Article20191126 In Wesson's canonical model, the universe is assumed to be five dimensional (5D) empty space time. This model corresponds to a solution of the Einstein field equation in five dimensions which, from a four dimensional point of view, is equivalent to a universe with a positive cosmological constant. In this model, the fifth direction is perpendicular to the four dimensional space time and is not compacted. Furthermore, the mass of particles in the four dimensional space time is related to their distance from the origin in the fifth direction while all particles are assumed to be massless in the 5D space time. In this article, we show that the vector fluctuations around the Wesson's solutions are tachyonic, i.e. the Wesson's vacuum is unstable. The mass of tachyon is proportional to square root of cosmological constant which is consistant with the experimental upper bound on photon’s less mass. Furthermore, the geodesic equations in the 5D space time give the Lorentz force in four dimensions. In this model, all massive particles are electrically charged and the charge-to-mass ratio depends on the age of universe, which exponentially tends to one. In Wesson's canonical model, the universe is assumed to be five dimensional (5D) empty space time. This model corresponds to a solution of the Einstein field equation in five dimensions which, from a four dimensional point of view, is equivalent to a universe with a positive cosmological constant. In this model, the fifth direction is perpendicular to the four dimensional space time and is not compacted. Furthermore, the mass of particles in the four dimensional space time is related to their distance from the origin in the fifth direction while all particles are assumed to be massless in the 5D space time. In this article, we show that the vector fluctuations around the Wesson's solutions are tachyonic, i.e. the Wesson's vacuum is unstable. The mass of tachyon is proportional to square root of cosmological constant which is consistant with the experimental upper bound on photon’s less mass. Furthermore, the geodesic equations in the 5D space time give the Lorentz force in four dimensions. In this model, all massive particles are electrically charged and the charge-to-mass ratio depends on the age of universe, which exponentially tends to one.https://ijpr.iut.ac.ir/article_930_3f35bd58ecf7518cc6002eb2fd29f72a.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126g factor of the charged leptons in noncommutative spacetimeg factor of the charged leptons in noncommutative spacetime265272931FAMHaghighatNMortazaviJournal Article20191126 The g-factor of the charged leptons has always been considered by many physicists, both experimentaly as well as theoretically. In fact the electron and muon g-factor play the main role in testing the QED as well as the standard model. Meanwhile, there is a discrepancy between the standard model prediction of the muon anomalies magnetic moment and its experimental determination as large as (25.5±8.0)×10-10.Therefore the g-factor can be used as the best place to study the new physics beyond the standard model. In this article, we consider the g-factor of the lepton in the noncommutative space time as a new physics model. In the ordinary theory, Schwinger evaluated the first correction to the g-factor of free electron, which arises from the electron interaction with photon at one loop level in the QED. In noncommutative space time, we show that at one loop, there is an NC-contribution to the g-factor of leptons which leads to a new bound on the noncommutative parameter (NC parameter). The obtained bounds are comparable with the current bounds on the NC-parameters of the order TeV. The g-factor of the charged leptons has always been considered by many physicists, both experimentaly as well as theoretically. In fact the electron and muon g-factor play the main role in testing the QED as well as the standard model. Meanwhile, there is a discrepancy between the standard model prediction of the muon anomalies magnetic moment and its experimental determination as large as (25.5±8.0)×10-10.Therefore the g-factor can be used as the best place to study the new physics beyond the standard model. In this article, we consider the g-factor of the lepton in the noncommutative space time as a new physics model. In the ordinary theory, Schwinger evaluated the first correction to the g-factor of free electron, which arises from the electron interaction with photon at one loop level in the QED. In noncommutative space time, we show that at one loop, there is an NC-contribution to the g-factor of leptons which leads to a new bound on the noncommutative parameter (NC parameter). The obtained bounds are comparable with the current bounds on the NC-parameters of the order TeV.https://ijpr.iut.ac.ir/article_931_127d71b4ef75e90daac546a14a5c65d7.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Feynman rules in the Lorentz violating extension of the standard modelFeynman rules in the Lorentz violating extension of the standard model273285932FAABinandehMHaghighatJournal Article20191126 We consider the Lorentz violating extension of the standard model introduced by D. Colladay and V. A. Kostelecky. In this framework, we obtain all Feynman rules for the electroweak part of the standard model extension (SME), for the first time. Among the new obtained interactions one finds new vertices for the Higgs boson that is interesting in the phenomenology of the Higgs particle. We consider the Lorentz violating extension of the standard model introduced by D. Colladay and V. A. Kostelecky. In this framework, we obtain all Feynman rules for the electroweak part of the standard model extension (SME), for the first time. Among the new obtained interactions one finds new vertices for the Higgs boson that is interesting in the phenomenology of the Higgs particle.https://ijpr.iut.ac.ir/article_932_58dfbad42f5c1799597f9be1755d79d3.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126The phonon and thermal properties of a ladder nanostructureThe phonon and thermal properties of a ladder nanostructure287292933FAMMardaani0000-0002-6268-5311MMardaaniHRabaniMKeshavarzJournal Article20191126 In this paper, we study the phonon thermal properties of a ladder nanostructure in harmonic approximation. We present a model consisting of two infinite chains with different masses. Then, we investigate the effect of different masses on the phonon spectrum. Moreover, as a specific case, in the absence of the second neighbor interaction, we calculate the phonon density of states/modes. Finally, we consider the thermal conductivity of the system. The results show that the phonon spectrum shifts down to the lower frequencies by increasing the masses. Furthermore, a frequency gap appears in the phonon spectrum. By increasing the springs constants, the thermal conductance decreases. In this paper, we study the phonon thermal properties of a ladder nanostructure in harmonic approximation. We present a model consisting of two infinite chains with different masses. Then, we investigate the effect of different masses on the phonon spectrum. Moreover, as a specific case, in the absence of the second neighbor interaction, we calculate the phonon density of states/modes. Finally, we consider the thermal conductivity of the system. The results show that the phonon spectrum shifts down to the lower frequencies by increasing the masses. Furthermore, a frequency gap appears in the phonon spectrum. By increasing the springs constants, the thermal conductance decreases.https://ijpr.iut.ac.ir/article_933_9958a528a18778d9528e02eb158874d6.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Relation between non uniform magnetic field and close binary systems periodRelation between non uniform magnetic field and close binary systems period293296934FAMZahediDJassurJournal Article20191126 Magnetic activity of one or both components of close binary systems can cause orbital period variation of the systems.Variation in gravitational quadropole moment will change the orbital period of the systems. In this article, we suppose that magnetic field is poloidal-troidal according to dynamo theory, and finds its relation with period change in the systems. Magnetic activity of one or both components of close binary systems can cause orbital period variation of the systems.Variation in gravitational quadropole moment will change the orbital period of the systems. In this article, we suppose that magnetic field is poloidal-troidal according to dynamo theory, and finds its relation with period change in the systems.https://ijpr.iut.ac.ir/article_934_e9d209aa982a016a20a284c2a6178d30.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Nuclear fission problem and Langevin equationNuclear fission problem and Langevin equation297304935FAMSakhaeeSJahanfarJournal Article20191126 A combined dynamical and statistical model for fission was employed in our calculation. There is no doubt that a Langevin description plus a Monte Carlo treatment of the evaporation processes provide the most adequate dynamical description. In this paper, we would consider a strongly shaped dependent friction force and we use the numerical method rather than the analytical one. The objective of this article is to calculate the time dependent fission widths of the 224Th nucleus. The fission widths were calculated with both chaos-weighted wall friction (CWWF) and wall friction (WF) dissipations. The calculations are repeated for 100000 trajectories. The result was compared to the others' work. We use nuclear elongation coordinate with time and it is necessary to repeat the small steps many times to improve the accuracy. A combined dynamical and statistical model for fission was employed in our calculation. There is no doubt that a Langevin description plus a Monte Carlo treatment of the evaporation processes provide the most adequate dynamical description. In this paper, we would consider a strongly shaped dependent friction force and we use the numerical method rather than the analytical one. The objective of this article is to calculate the time dependent fission widths of the 224Th nucleus. The fission widths were calculated with both chaos-weighted wall friction (CWWF) and wall friction (WF) dissipations. The calculations are repeated for 100000 trajectories. The result was compared to the others' work. We use nuclear elongation coordinate with time and it is necessary to repeat the small steps many times to improve the accuracy.https://ijpr.iut.ac.ir/article_935_013b262b49cc877ed4710c1fcefc469b.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Synchronization of the Kuramoto model on a regular networkSynchronization of the Kuramoto model on a regular network305313936FARKouhi EsfahaniFShahbaziKAghababaei SamaniJournal Article20191126Stable solutions of the Kuramoto model on a regular network are investigated. It is shown that there are two stable states: a completely synchronized state with an order parameter equal to one and a completely incoherent state with an order parameter equal to zero. Also, the situation that could lead to the order parameter just equal to one is found out. Furthermore, it is shown that the phase difference of neighboring oscillators must be less than π/2 for a getting a stable state. It is also proved that by having the degree of each node more than half of the total number of nodes, we could only have the order parameter equal to one in (-π, π] for each initial phase condition.Stable solutions of the Kuramoto model on a regular network are investigated. It is shown that there are two stable states: a completely synchronized state with an order parameter equal to one and a completely incoherent state with an order parameter equal to zero. Also, the situation that could lead to the order parameter just equal to one is found out. Furthermore, it is shown that the phase difference of neighboring oscillators must be less than π/2 for a getting a stable state. It is also proved that by having the degree of each node more than half of the total number of nodes, we could only have the order parameter equal to one in (-π, π] for each initial phase condition.https://ijpr.iut.ac.ir/article_936_53771a4dccee4927c4be9e5309efd115.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Monte Carlo simulation algorithm for pileup effect of pulses in gamma spectroscopy and pileup distortion calculation on 137Cs pulse height spectrum in NaI(Tl) detectorMonte Carlo simulation algorithm for pileup effect of pulses in gamma spectroscopy and pileup distortion calculation on 137Cs pulse height spectrum in NaI(Tl) detector315320937FAAAMowlaviJournal Article20191126 In this paper, an algorithm base on Monte Carlo simulation for pileup effect in gamma spectrum of a detection system is presented whose its code was written in FORTRAN language. The code can be run in paralayzable and nonparalazable mode to obtain the pileup distortion and value of pulses pileup for any detection system. The result show, that the computed spectrum of 137Cs is in good agreement with the experimental spectrum in NaI(Tl) detector. The free of pileup free spectrum and sub-spectra with different degrees of pulses of pileup are calculated. Also, we can apply it to different sources and detectors for pileup correction. In this paper, an algorithm base on Monte Carlo simulation for pileup effect in gamma spectrum of a detection system is presented whose its code was written in FORTRAN language. The code can be run in paralayzable and nonparalazable mode to obtain the pileup distortion and value of pulses pileup for any detection system. The result show, that the computed spectrum of 137Cs is in good agreement with the experimental spectrum in NaI(Tl) detector. The free of pileup free spectrum and sub-spectra with different degrees of pulses of pileup are calculated. Also, we can apply it to different sources and detectors for pileup correction.https://ijpr.iut.ac.ir/article_937_08bf03f08dafb5afe8aecb8f81d9f6c3.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126High temperature series expansions for the susceptibility of Ising model on the Kagome lattice with nearest neighber interactionsHigh temperature series expansions for the susceptibility of Ising model on the Kagome lattice with nearest neighber interactions321328938FAZJalali MolaFShahbaziJournal Article20191126 The Ising model is one of the simplest models describing the interacting particles. In this work, we calculate the high temperature series expansions of zero field susceptibility of ising model with ferromagnetic, antiferromagnetic and one antiferromagnetic interactions on two dimensional kagome lattice. Using the Pade´ approximation, we calculate the susceptibility of critical exponent of ferromagnetic ising model γ ≈ 1.75, which is consistent with universality hypothesis. However, antiferromagnetic and one antiferromagnetic interaction ising model doesn’t show any transition at finite temperature because of the effect of magnetic frustration. The Ising model is one of the simplest models describing the interacting particles. In this work, we calculate the high temperature series expansions of zero field susceptibility of ising model with ferromagnetic, antiferromagnetic and one antiferromagnetic interactions on two dimensional kagome lattice. Using the Pade´ approximation, we calculate the susceptibility of critical exponent of ferromagnetic ising model γ ≈ 1.75, which is consistent with universality hypothesis. However, antiferromagnetic and one antiferromagnetic interaction ising model doesn’t show any transition at finite temperature because of the effect of magnetic frustration.https://ijpr.iut.ac.ir/article_938_f8b3010c3ee4a7e10eb1f35201a044fa.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Formalism of overlaps of valence bond states with any number of triplonFormalism of overlaps of valence bond states with any number of triplon329333939FAEGhorbaniSAJafariFShahbaziJournal Article20191126 Resonating valence bond (RVB) states are suitable candidates for ground state of the Heisenberg model on various two dimensional lattices. When a singlet valence bond is broken to produce a triplet state, the resulting excitation is called a triplon. In this paper, we obtain formulas for the overlap and also matrix elements of si.sj operator between states with arbitrary number of triplons . Our results are valid for any 2D lattice. Resonating valence bond (RVB) states are suitable candidates for ground state of the Heisenberg model on various two dimensional lattices. When a singlet valence bond is broken to produce a triplet state, the resulting excitation is called a triplon. In this paper, we obtain formulas for the overlap and also matrix elements of si.sj operator between states with arbitrary number of triplons . Our results are valid for any 2D lattice.https://ijpr.iut.ac.ir/article_939_0d75656261f63487ed9fac5eba84bf96.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Construction and testing of a hydrogen cracking cellConstruction and testing of a hydrogen cracking cell335335940FAFSahra GardJournal Article20191126A UHV atomic hydrogen-cracking cell has been constructed to produce atomic hydrogen in order to perform in-situ cleaning of semiconductor samples. The cell was calibrated and tested with the objective of cleaning the III-V semiconductor samples such as GaAs. Mass spectroscopy studies during the atomic hydrogen cleaning of the GaAs samples revealed the chemical process of the hydrogen cleaning. X-ray Photoemission Spectroscopy (XPS) was also carried out on the samples at different stages of cleaning. Desorption of the native oxide from GaAs samples resulted in a smooth surface, which was confirmed by Reflection High Energy Electron Diffraction (RHEED).A UHV atomic hydrogen-cracking cell has been constructed to produce atomic hydrogen in order to perform in-situ cleaning of semiconductor samples. The cell was calibrated and tested with the objective of cleaning the III-V semiconductor samples such as GaAs. Mass spectroscopy studies during the atomic hydrogen cleaning of the GaAs samples revealed the chemical process of the hydrogen cleaning. X-ray Photoemission Spectroscopy (XPS) was also carried out on the samples at different stages of cleaning. Desorption of the native oxide from GaAs samples resulted in a smooth surface, which was confirmed by Reflection High Energy Electron Diffraction (RHEED).https://ijpr.iut.ac.ir/article_940_62d3f1f555ad1d81ab1f611d28fb3a80.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Temperature dependence of continuum and time resolved photoluminescence of germanium nanostructuresTemperature dependence of continuum and time resolved photoluminescence of germanium nanostructures336336941FAMArdyanianSAKetabiJournal Article20191126 Germanium nanostructures were generated in the post annealed germanium oxide thin films. Visible and near infrared photoluminescence bands were observed in the samples annealed at 350°C and 400°C, respectively. These different luminescence ranges are attributed to the presence of the defects in oxide matrix and quantum confinement effect in the germanium nanostructures, respectively. Decay time and temperature dependence of the luminescence for different bands were investigated, which confirmed our idea about the origin of the luminescence. Germanium nanostructures were generated in the post annealed germanium oxide thin films. Visible and near infrared photoluminescence bands were observed in the samples annealed at 350°C and 400°C, respectively. These different luminescence ranges are attributed to the presence of the defects in oxide matrix and quantum confinement effect in the germanium nanostructures, respectively. Decay time and temperature dependence of the luminescence for different bands were investigated, which confirmed our idea about the origin of the luminescence.https://ijpr.iut.ac.ir/article_941_b60392d18e69e4aadf84ffdff1856d0d.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-695711320191126Field detection of CO and CH4 by NIR 2f modulation laser spectroscopyField detection of CO and CH4 by NIR 2f modulation laser spectroscopy337337942FAAKhorsandiSBagherianSGhavami SabouriCRomanoWSchadeJournal Article20191126 A novel compact fiber-coupled NIR system based on a DFB diode laser source is employed as a portable and sensitive gas sensor for trace detection of combustion pollutant molecules. We demonstrate the performance of such an NIR gas sensor by tracing the absorption lines of CO and CH4 using 2f-WMS technique at moderate temperature of T ~ 600°C in the recuperator channel of an industrial furnace provided by Mobarakeh steel company. This measurement shows the excellent sensitivity of the applied NIR gas sensor to the on-line and in-situ monitoring of such molecular species. A novel compact fiber-coupled NIR system based on a DFB diode laser source is employed as a portable and sensitive gas sensor for trace detection of combustion pollutant molecules. We demonstrate the performance of such an NIR gas sensor by tracing the absorption lines of CO and CH4 using 2f-WMS technique at moderate temperature of T ~ 600°C in the recuperator channel of an industrial furnace provided by Mobarakeh steel company. This measurement shows the excellent sensitivity of the applied NIR gas sensor to the on-line and in-situ monitoring of such molecular species.https://ijpr.iut.ac.ir/article_942_56ec8df1ff74f9a8cdf2b0baf885a634.pdf