Schrödinger equation for pair of two massless Dirac particles when magnetic field is applied in Landau gauge is solved exactly. In this case, the separation of center of mass and relative motion is obtained. L...Schrödinger equation for pair of two massless Dirac particles when magnetic field is applied in Landau gauge is solved exactly. In this case, the separation of center of mass and relative motion is obtained. Landau quantization ε = ±B/?l for pair of two Majorana fermions coupled via a Coulomb potential from massless chiral Dirac equation in cylindric coordinate is found. The root ambiguity in energy spectrum leads into Landau quantization for bielectron, when the states in which the one simultaneously exists are allowed. The tachyon solution with imaginary energy in Cooper problem (ε 2 < 0) is found. The continuum symmetry of Dirac equation allows perfect pairing between electron Fermi spheres when magnetic field is applied in Landau gauge creating a Cooper pair.展开更多
In this study,we investigate the expansion of the FRLW universe in the open,closed,and flat geometries.The universe is dominated by a scalar field(spatially homogeneous)as a source of dark energy.We consider the three...In this study,we investigate the expansion of the FRLW universe in the open,closed,and flat geometries.The universe is dominated by a scalar field(spatially homogeneous)as a source of dark energy.We consider the three different classes of scalar fields-quintessence,tachyonic,and phantom field-for our analysis.A mathematical analysis is carried out by considering these three scalar fields with exponential and power-law potentials.Both potentials give exponential expansion in the open,closed,and flat FRLW universes.It is found that quintessence,tachyonic,and phantom scalar fields are indistinguishable under the slow roll approximation.展开更多
We consider a tachyonic model of dark energy in which scalar field non-minimally coupled with curvature and kinetic part of its Lagrangian density.Additionally the model contains the Gauss–Bonnet coupling to the scal...We consider a tachyonic model of dark energy in which scalar field non-minimally coupled with curvature and kinetic part of its Lagrangian density.Additionally the model contains the Gauss–Bonnet coupling to the scalar field through an arbitrary function.The non-minimal Gauss–Bonnet coupling function and scalar field potential have been obtained for power-law solution and then for a dynamically varying equation of state.We have extracted the required condition for the so-called phantom divide line crossing in the model and represented such a crossing numerically.展开更多
In this study,the scenario of a two-component warm tachyon inflation is considered,where the tachyon field plays the role of the inflaton by driving the inflation.During inflation,the tachyon scalar field interacts wi...In this study,the scenario of a two-component warm tachyon inflation is considered,where the tachyon field plays the role of the inflaton by driving the inflation.During inflation,the tachyon scalar field interacts with the other component of the Universe,which is assumed to be photon gas,i.e.,radiation.The interacting term contains a dissipation coefficient,and the study is modeled based on two different and familiar choices of the coefficient that were studied in the literature.By employing the latest observational data,the acceptable ranges for the free parameters of the model are obtained.For any choice within the estimated ranges,there is an acceptable concordance between the theoretical predictions and observations.Although the model is established based on several assumptions,it is crucial to verify their validity for the obtained values of the free parameters of the model.It is found that the model is not self-consistent for all values of the ranges,and for some cases,the assumptions are violated.Therefore,to achieve both self-consistency and agreement with the data,the parameters of the model must be constrained.Subsequently,we consider the recently proposed swampland conjecture,which imposes two conditions on the inflationary models.These criteria rule out some inflationary models;however,warm inflation is among those that successfully satisfy the swampland criteria.We conduct a precise investigation,which indicates that the proposed warm tachyon inflation cannot satisfy the swampland criteria for some cases.In fact,for the first case of the dissipation coefficient,in which,there is dependency only on the scalar field,the model agrees with observational data.However,it is in direct tension with the swampland criteria.Nevertheless,for the second case,wherein the dissipation coefficient has a dependency on both the scalar field and temperature,the model exhibits acceptable agreement with observational data,and suitably satisfies the swampland criteria.展开更多
We have studied the tachyon intermediate and logamediate warm inflation in loop quantum cosmological background by taking the dissipative co-efficient Γ = Γ_0(where Γ_0 is a constant) in "intermediate" in...We have studied the tachyon intermediate and logamediate warm inflation in loop quantum cosmological background by taking the dissipative co-efficient Γ = Γ_0(where Γ_0 is a constant) in "intermediate" inflation and Γ = V(φ),(where V(φ) is the potential of tachyonic field) in "logamediate" inflation. We have assumed slow-roll condition to construct scalar field φ, potential V, N-folds, etc. Various slow-roll parameters have also been obtained.We have analyzed the stability of this model through graphical representations.展开更多
文摘Schrödinger equation for pair of two massless Dirac particles when magnetic field is applied in Landau gauge is solved exactly. In this case, the separation of center of mass and relative motion is obtained. Landau quantization ε = ±B/?l for pair of two Majorana fermions coupled via a Coulomb potential from massless chiral Dirac equation in cylindric coordinate is found. The root ambiguity in energy spectrum leads into Landau quantization for bielectron, when the states in which the one simultaneously exists are allowed. The tachyon solution with imaginary energy in Cooper problem (ε 2 < 0) is found. The continuum symmetry of Dirac equation allows perfect pairing between electron Fermi spheres when magnetic field is applied in Landau gauge creating a Cooper pair.
文摘In this study,we investigate the expansion of the FRLW universe in the open,closed,and flat geometries.The universe is dominated by a scalar field(spatially homogeneous)as a source of dark energy.We consider the three different classes of scalar fields-quintessence,tachyonic,and phantom field-for our analysis.A mathematical analysis is carried out by considering these three scalar fields with exponential and power-law potentials.Both potentials give exponential expansion in the open,closed,and flat FRLW universes.It is found that quintessence,tachyonic,and phantom scalar fields are indistinguishable under the slow roll approximation.
文摘We consider a tachyonic model of dark energy in which scalar field non-minimally coupled with curvature and kinetic part of its Lagrangian density.Additionally the model contains the Gauss–Bonnet coupling to the scalar field through an arbitrary function.The non-minimal Gauss–Bonnet coupling function and scalar field potential have been obtained for power-law solution and then for a dynamically varying equation of state.We have extracted the required condition for the so-called phantom divide line crossing in the model and represented such a crossing numerically.
基金The work of A.M.has been supported financially by‘Vice Chancellorship of Research and Technology,University of Kurdistan’under research Project No.98/10/34704The work of T.G.has been supported financially by‘Vice Chancellorship of Research and Technology,University of Kurdistan’under research Project No.98/11/2724。
文摘In this study,the scenario of a two-component warm tachyon inflation is considered,where the tachyon field plays the role of the inflaton by driving the inflation.During inflation,the tachyon scalar field interacts with the other component of the Universe,which is assumed to be photon gas,i.e.,radiation.The interacting term contains a dissipation coefficient,and the study is modeled based on two different and familiar choices of the coefficient that were studied in the literature.By employing the latest observational data,the acceptable ranges for the free parameters of the model are obtained.For any choice within the estimated ranges,there is an acceptable concordance between the theoretical predictions and observations.Although the model is established based on several assumptions,it is crucial to verify their validity for the obtained values of the free parameters of the model.It is found that the model is not self-consistent for all values of the ranges,and for some cases,the assumptions are violated.Therefore,to achieve both self-consistency and agreement with the data,the parameters of the model must be constrained.Subsequently,we consider the recently proposed swampland conjecture,which imposes two conditions on the inflationary models.These criteria rule out some inflationary models;however,warm inflation is among those that successfully satisfy the swampland criteria.We conduct a precise investigation,which indicates that the proposed warm tachyon inflation cannot satisfy the swampland criteria for some cases.In fact,for the first case of the dissipation coefficient,in which,there is dependency only on the scalar field,the model agrees with observational data.However,it is in direct tension with the swampland criteria.Nevertheless,for the second case,wherein the dissipation coefficient has a dependency on both the scalar field and temperature,the model exhibits acceptable agreement with observational data,and suitably satisfies the swampland criteria.
文摘We have studied the tachyon intermediate and logamediate warm inflation in loop quantum cosmological background by taking the dissipative co-efficient Γ = Γ_0(where Γ_0 is a constant) in "intermediate" inflation and Γ = V(φ),(where V(φ) is the potential of tachyonic field) in "logamediate" inflation. We have assumed slow-roll condition to construct scalar field φ, potential V, N-folds, etc. Various slow-roll parameters have also been obtained.We have analyzed the stability of this model through graphical representations.
