Exact solution of the (1+2)-dimensional generalized Kemmer oscillator in the cosmic string background with the magnetic field

We study a two-dimensional generalized Kemmer oscillator in the cosmic string spacetime with the magnetic field to better understand the contribution from gravitational field caused by topology defects,and present the exact solutions to the generalized Kemmer equation in the cosmic string with the Morse potential and Coulomb-liked potential through using the Nikiforov-Uvarov(NU)method and biconfluent Heun equation method,respectively.Our results give the topological defect’s correction for the wave function,energy spectrum and motion equation,and show that the energy levels of the generalized Kemmer oscillator rely on the angular deficitαconnected with the linear mass density m of the cosmic string and characterized the metric’s structure in the cosmic string spacetime.

Alignment of Quasar Polarizations on Large Scales Explained by Warped Cosmic Strings

The recently discovered alignment of quasar polarizations on very large scales could possibly be explained by considering cosmic strings on a warped five dimensional spacetime. Compact objects, such as cosmic strings, could have tremendous mass in the bulk, while their warped manifestations in the brane can be consistent with general relativity in 4D. The self-gravitating cosmic string induces gravitational wavelike disturbances which could have effects felt on the brane, i.e., the massive effective 4D modes (Kaluza-Klein modes) of the perturbative 5D graviton. This effect is amplified by the time dependent part of the warp factor. Due to this warp factor, disturbances don’t fade away during the expansion of the universe. From a nonlinear perturbation analysis it is found that the effective Einstein 4D equations on an axially symmetric spacetime, contain a “back-reaction” term on the righthand side caused by the projected 5D Weyl tensor and can act as a dark energy term. The propagation equations to first order for the metric components and scalar-gauge fields contain -dependent terms, so the approximate wave solutions are no longer axially symmetric. The disturbances, amplified by the warp factor, can possess extremal values for fixed polar angles. This could explain the two preferred polarization vectors mod .

Alignment of Quasar Polarizations on Large Scales Explained by Warped Cosmic Strings. PART II: The Second Order Contribution

We find an azimuthal-angle dependent approximate wave like solution to second order on a warped five-dimensional manifold with a self-gravitating U(1) scalar gauge field (cosmic string) on the brane using the multiple-scale method. The spectrum of the several orders of approximation show maxima of the energy distribution dependent on the azimuthal-angle and the winding numbers n of the subsequent orders of scalar field. This breakup of the quantized flux quanta does not lead to instability of the asymptotic wavelike solution, due to the suppression of the n-dependency in the energy mo-mentum tensor components by the warp factor. This effect is triggered by the contribution of the five dimensional Weyl tensor on the brane. This con-tribution can be understood as dark energy and can trigger the self-acceleration of the universe without the need of a cosmological constant. There is a striking relation between the symmetry breaking of the Higgs field described by the winding number and the SO(2) breaking of the axially symmetric configuration into a discrete subgroup of rotations about 180°. The discrete sequence of non-axially symmetric deviations, cancelled by the emission of gravitational waves in order to restore the SO(2) symmetry, triggers the pressure Tzz for discrete values of the azimuthal-angle. There can be a possible relation between the recently discovered angle-preferences of polarization axes of quasars on large scales and our theoretical predicted angle-dependency and can be an evidence for the existence of cosmic strings. The discovery of the increase of polarization rate in smaller subgroups of the several large-quasar groups (LQGs), the red shift dependency and the relative orientation of the spin axes with respect to the major axes of their host LQGs, point at a fractional azimuthal structure, were also found in our cosmic string model. This peculiar discontinuous large scale structure, i.e., polarizations directions of multiples of, for example, π/2 orπ/4, can be explained by the spectrum of azimuthal-angle dependent wavelike modes without the need of conventional density perturbations in standard 4D cosmological models. Carefully com-parison of the spectrum of extremal values of the first and second order φ-dependency and the distribution of the alignment of the quasar polarizations is necessary. This can be accomplished when more observational data become available.

The nanohertz stochastic gravitational wave background from cosmic string loops and the abundant high redshift massive galaxies

Recently,pulsar timing array(PTA)experiments have provided compelling evidence for the existence of the nanohertz stochastic gravitational wave background(SGWB).In this work,we demonstrated that cosmic string loops generated from cosmic global strings offer a viable explanation for the observed nanohertz SGWB data,requiring a cosmic string tension parameter of log(Gμ)~-12 and a loop number density of log N~4.Additionally,we revisited the impact of cosmic string loops on the abundance of massive galaxies at high redshifts.However,our analysis revealed challenges in identifying a consistent parameter space that can concurrently explain both the SGWB data and observations from the James Webb Space Telescope.This indicates the necessity for either extending the existing model employed in this research or acknowledging distinct physical origins for these two phenomena.

Gravitational waves from cosmic strings associated with pseudo-Nambu-Goldstone dark matter

We study stochastic gravitational waves from cosmic strings generated in an ultraviolet-complete model for pseudo-Nambu-Goldstone dark matter with a hidden U(1)gauge symmetry.The dark matter candidate in this model can naturally evade direct detection bounds and easily satisfy other phenomenological constraints.The bound on the dark matter lifetime implies an ultraviolet scale higher than 10^(9)GeV.The spontaneous U(1)symmetry breaking at such a high scale would induce cosmic strings with high tension,resulting in a stochastic gravitational wave background with a high energy density.We investigate the constraints from current gravitational wave experiments as well as the future sensitivity.We find that most viable parameter points can be well studied in future gravitational waveexperiments.

Gravitational waves from cosmic strings after a first-order phase transition

We study the possibility of probing high scale phase transitions that are inaccessible by LIGO.Our study shows that the stochastic gravitational-wave radiation from cosmic strings that are formed after the first-order phase transition can be detected by space-based interferometers when the phase transition temperature is T_(n)~O(10^(8−11))GeV.

Radio jets and galaxies as cosmic string probes

The lensing effect of a cosmic string is studied, and some new methods are proposed to detect the cosmic string. The technique for using jets as extended gravitational lensing probes was first explored by Kronberg. We use the ＂alignment-breaking parameter＂ nc as a sensitive indicator of gravitational distortion by a wiggly cosmic string. Then, we applied the non-constant deflection angle to jets, and na of a specific jet is just related to the projected slope of the jet. At least three jets in the sample of Square Kilometer Array （SKA） would have significant signals （na 〉 10°） if the wiggly infinite cosmic string existed. The distortion of elliptical object is also studied and used to do a statistical research on the directions of axes and ellipticities of galaxies. In the direction of the string, we find that galaxies appear to be more elliptical for an observer and the distribution of apparent ellipticity changes correspondingly. The ellipticity distribution of current SDSS spiral sample has the signal- to-noise ratio up to 8.48 which is large enough for astronomical observations. The future survey, such as Large Synoptic Survey Telescope （LSST） and Dark Energy Survey （DES） would weaken the requirement of special geometry in the data processing. As a result, all kinds of distributions, including ellipticity axis distribution, would serve as probes to detect wiggly strings in the near future. In brief, if a wiggly cosmic string existed, these signals would be convenient to be observed with the future weak lensing survey or other surveys in the deep space. If there was no lensing signal in these distributions, it would give the upper limit of the abundance of infinite strings.

Thermodynamics of a Schwarzschild Black Hole With a Cosmic String or a Global Monopole

It is well known that thermodynamics of the black hole whose space-time isasymptotically flat obeys the four laws proposed by Bardeen, Carter and Hawking.But for the Schwarzschild type black hole whose space-time is no longerasymptotically flat, whether the Bardeen-Carter-Hawking laws are valid is worthstudying. We all know that certain gauge theories allow possibility of topological de-

LENSING EFFECTS OF A STRAIGHT COSMIC STRING

I. BENDING ANGLE OF LIGHT-RAYThe exterior gravitational field of a straight cosmic string written in units in which G/c^2=1

CLUSTERING IN A UNIVERSE WITH HOT DARK MATTER AND COSMIC STRINGS

Theories on the nucleosynthesis in the very early universe show that the baryonic matter is just a fraction of the cosmic matter. Moreover, the flatness of the space geometry of the universe shows that the cosmic density factor Ω= 1, this means that most of the cosmic matter exists in the form of dark matter. Confirmed by experiments up to the present, neutrino

Absorption/Scattering of Massless Dirac Wave from Black Hole Spacetimes with Cosmic String

In this paper we investigate the scattering of massless Dirac wave from several different black hole spacetimes(i.e. the Schwarzschild black hole, the RN extremal black hole, the Schwarzschild de Sitter black hole, and the extremal Schwarzschild de Sitter black hole) which are influenced by the cosmic string, respectively. All these cases show us that the total absorption cross sections oscillate around the geometric-optical limit and decrease with linear mass density μof the cosmic string. All of the total scattering cross sections exhibit that the main scattering angle becomes narrower for the high partial frequency wave. Due to the influence of cosmic string, the glory peak becomes wider for larger values of linear mass density μ of the cosmic string.

SECONDARY EFFECTS OF COSMIC STRING

The reionization and the large-scale structure formation of the universe are consi-dered as results of the secondary effects of cosmic string. Primordial supermassive (～10~6M_⊙) stars and star groups M(～10^(10)M_⊙) can be formed immediately after recombinationowning to the accretions of single-string loops. The ultraviolet radiation of the starscan reionize the interstellar medium around them. The explosions of the supermassivestars sweep the interstellar medium to the shock-wave front to form mass shells of largemass and high density; the fragmentations of the mass shells lead to formations of newstars and new explosions. It is shown, when Grand Unification Theory (GUT) stringsare taken to be the seeds, the observed high ionization and large-scale cellular structureof galaxy distribution in the universe can be realized. For the usually chosen parameters,this scenario seems reasonable and imperative.

源于宇宙弦的引力波暴及其电磁共振效应

引力波为宇宙学模型的检验提供了新方法,宇宙弦环震荡会激发较强的尖端引力辐射,甚高频波段的引力波可以通过电磁共振效应来探测.文章基于修正的宇宙弦模型,以p和?为自由参数,主要研究了宇宙弦环震荡产生的甚高频引力波特性h,以及在电磁共振方案中产生的物理效应.通过数值计算保守估计引力波暴的量纲为1的振幅强度可以达到10^(-28)~10^(-25).在电磁共振效应下产生的信号光子流强度N_(x)^(1)达到10^(4)~10^(8)s^(-1),信噪比强度S为10^(-20)~10^(-14).与其它类型的此频段引力波相比较,此类引力波更可能在未来被探测器探测到.

Anisotropic Bianchi Type-I Magnetized String Cosmological Models with Decaying Vacuum Energy Density A(t)

The present study deals with a spatially homogeneous and anisotropic Bianehi-I cosmological models representing massive strings with magnetic field and decaying vacuum energy density A. The energy-momentum tensor, as formulated by Letelier （1983）, has been used to construct massive string cosmological models for which we assume the expansion scalar in the models is proportional to one of the components of shear tensor. The Einstein＇s field equations have been solved by applying a variation law for generalized Hubble＇s parameter in Bianchi-I space-time. The variation law for Hubble＇s parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein＇s field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. We have made a comparative study of accelerating and decelerating models in the presence of string scenario. The study reveals that massive strings dominate in the decelerating universe whereas strings dominate in the accelerating universe. The strings eventually disappear from the universe for sufficiently large times, which is in agreement with current astronomical observations. The cosmological constant A is found to be a positive decreasing function of time which is corroborated by results from recent supernovae Ia observations. The physical and geometric properties of the models have been also discussed in detail.

String Cloud and Domain Walls with Quark Matter in Lyra Geometry

We have constructed cosmological models for string cloud and domain walls coupled with quark matter in Lyra geometry. For this purpose we have solved the field equations using anisotropy feature of the universe, special law of variation for Hubble’s parameter proposed by Berman [78] which yields constant deceleration parameter;and time varying displacement field . Further some properties of the obtained solutions are discussed.

Five Dimensional String Universes in Lyra Manifold

Considering five dimensional plane symmetric metric, we discuss a model universe with different situations, by solving the modified Einstein field equations within the framework of Lyra geometry. We obtain many interesting realistic solutions governing the present day model of the universe. Physical and kinematical properties of the models are discussed in detail.

曲面上的曲率在理论物理中的一些应用

In this survey article,we present two applications of surface curvatures in theoretical physics.The first application arises from biophysics in the study of the shape of cell vesicles involving the minimization of a mean curvature type energy called the Helfrich bending energy.In this formalism,the equilibrium shape of a cell vesicle may present itself in a rich variety of geometric and topological characteristics.We first show that there is an obstruction,arising from the spontaneous curvature,to the existence of a minimizer of the Helfrich energy over the set of embedded ring tori.We then propose a scale-invariant anisotropic bending energy,which extends the Canham energy,and show that it possesses a unique toroidal energy minimizer,up to rescaling,in all parameter regime.Furthermore,we establish some genus-dependent topological lower and upper bounds,which are known to be lacking with the Helfrich energy,for the proposed energy.We also present the shape equation in our context,which extends the Helfrich shape equation.The second application arises from astrophysics in the search for a mechanism for matter accretion in the early universe in the context of cosmic strings.In this formalism,gravitation may simply be stored over a two-surface so that the Einstein tensor is given in terms of the Gauss curvature of the surface which relates itself directly to the Hamiltonian energy density of the matter sector.This setting provides a lucid exhibition of the interplay of the underlying geometry,matter energy,and topological characterization of the system.In both areas of applications,we encounter highly challenging nonlinear partial differential equation problems.We demonstrate that studies on these equations help us to gain understanding of the theoretical physics problems considered.

Kähler Dark Matter, Dark Energy Cosmic Density and Their Coupling

We utilize homology and co-homology of a K3-Kähler manifold as a model for spacetime to derive the cosmic energy density of our universe and subdivide it into its three fundamental constituents, namely: 1) ordinary energy;2) pure dark energy and 3) dark matter. In addition, the fundamental coupling of dark matter to pure dark energy is analyzed in detail for the first time. Finally, the so-obtained results are shown to be in astounding agreement with all previous theoretical analysis as well as with actual accurate cosmic measurements.

中性流超导宇宙弦及W玻色子凝结

该文提出对中性流超导的宇宙弦,它可能影响到弱电真空,产生W玻色子凝结现象.

有限温度整体宇宙弦的引力场及其物质的吸积

本文讨论了有限温度整体宇宙弦的引力场及其物质的吸积，以及在有限温度运动整体宇宙弦对吸积物质的影响，其结果与零温整体宇宙弦的性质有区别。