宇宙弦的弦张力

由宇宙弦的理想气体热力学模型出发,用鞍点近似方法,导出了宇宙弦的弦张力表达式.     

Spherically Symmetric Cosmic Strings in Bimetric Theory

Spherically symmetric space-time is considered in bimetric theory of gravitation formulated by Rosen (Gen. Relativ. Gravit. 4:435, [1973]) in the presence of perfect fluid, massive scalar field and cosmic string. It is shown that either macro cosmological model represented by perfect fluid or cosmic string do not exist and only a vacuum model can be constructed whereas in case of a micro cosmological model represented by a scalar field exists and the model is obtained.     

Cosmic Strings in a Model of Non-relativistic Gravity

Hořava proposed a non-relativistic renormalizable theory of gravitation, which is reduced to general relativity (GR) in large distances (infra-red regime (IR)). It is believed that this theory is an ultra-violet (UV) completion for the classical theory of gravitation. In this paper, after a brief review of some fundamental features of this theory, we investigate it for a static cylindrical symmetric solution which describes Cosmic string as a special case. We have also investigated some possible solutions, and have seen that how the classical GR field equations are modified for generic potential V(g). In one case there is an algebraic constraint on the values of three coupling constants. Finally as a pioneering work we deduce the most general cosmic string in this theory. We explicitly show that how the coupling constants distort the mass parameter of cosmic string. We deduce an explicit function for mass per unit length of the space-time as a function of the coupling constants. We compare this function with another which Aryal et al. (Phys. Rev. D 34:2263, 1986) have found in GR. Also we calculate the self-force on a massive particle near Hořava-Lifshitz straight string and we give a typical order for the coupling constant g ₉. This order of magnitude proposes a cosmological test for validity of this theory.     

On the Dynamics of Two Oscillating Cosmic Strings

We present the spacetime interval of thenonradiated cosmic string oscillating as standing waves.The influence of string oscillations on the dynamics ofa probe cosmic thread that performs free oscillations and moves in its vicinity, isdiscussed.     

Cosmic Strings in Realistic Particle Physics Theories and Baryogenesis

Grand unified theories can admit cosmic stringswith fermion zero modes. Such zero modes result in thestring being current-carrying and the formation ofstable remnants, vortons. However, the string zero modes do not automatically survive subsequentphase transitions. In this case the vortons dissipate.It is possible that the dissipating cosmic vortonscreate the observed baryon asymmetry of the universe. We show that fermion zero modes are anautomatic consequence cosmic strings in supersymmetrictheories. Since supersymmetry is not observed in nature,we consider possible supersymmetry-breaking terms. Some of these terms result in the zero modesbeing destroyed. We calculate the baryon asymmetrygenerated by the consequent dissipating cosmic vortons.If the supersymmetry-breaking scale is high enough, then the dissipating cosmic vortons couldaccount for the observed baryon asymmetry.     

The Importance of Quantum Effects in Superconducting Cosmic Strings

Classical current-carrying cosmic string loopmotion is investigated by means of a numericalsimulation making explicit use of the Carter formalismand the Carter-Peter rational and logarithmic equations of state. The class of initial configurationsconsists of elliptic loops far from the vortonequilibrium state with constant state parameter alongthe loop. Thus, the relevant parameters, apart fromthose describing the equation of state itself, arethe ellipticity and the initial state parameter. It isfound that for most of the parameter space, the loopmotion is quasiperiodic, but that this result is actually irrelevant to the treatment of anarbitrary loop motion: indeed, almost systematically,the loops develop kinks and cusps, and in the case ofspacelike currents, there are segments of the loop that escape the elastic regime. It is thenargued that quantum effects resulting from thesesituations will in practice provide the dominantevolution mechanisms.     

Destruction of Fermion Zero Modes on Cosmic Strings

I examine the existence of zero-energy fermionsolutions (zero modes) on cosmic strings in an SO (10)grand unified theory. The current-carrying capability ofa cosmic string formed at one phase transition can be modified at subsequent phasetransitions. I show that the zero modes may be destroyedand the conductivity of the string altered. I discussthe cosmological implications of this, and show that it allows vorton bounds to be relaxed.     

Cosmic Strings Coupled with a Massless Scalar Field

A scalar field generalization of Xanthopoulos's cylindrically symmetric solutions of the vacuum-Einstein equations is obtained. The obtained solution preserves the properties of the Xanthopoulos solution, which are regular on the axis, asymptotically flat, and free from the curvature singularities. The solution describes a stable, rotating cosmic string of infinite length interacting with gravitational and scalar waves.     

Local Cosmic Strings from Pseudo-Anomalous U(1)

Local cosmic strings solutions are introduced ina model with a peudo-anomalous U(1) gauge symmetry. Sucha symmetry is present in many superstringcompactification models. The coupling of those strings with the axion necessary in order to cancel theanomalies does not prevent them from being local, eventhough their energy per unit length is found to divergelogarithmically. I discuss briefly the formation of such strings and the phenomenologicalconstraints that apply to their parameters.     

On Axially Symmetric Domain Walls and Cosmic Strings in Bimetric Theory

It is shown that the axially symmetric thick domain walls and cosmic strings do not survive in the frame work of bimetric theory of gravitation proposed by Rosen (Gen. Relativ. Gravit. 4:435, 1973). Hence vacuum models are presented and studied.     

Cosmic Strings in the Universe: Achievements and prospects of research

Cosmic strings are linear structures of cosmological scales whose search has been actively conducted in recent years. Progress in constructing theoretical models and investigating the properties of cosmic strings and a significant growth of observational resources provide extensive possibilities for the search of such objects by several independent observational methods. These methods include searching for the events of gravitational lensing of distant background sources by strings and searching for the distinctive cosmic micro-wave background anisotropy structures induced by strings. We discuss these techniques and propose the methods of searching for strings oriented toward the latest spacecraft, including the Planck project.     

Cosmic Strings and Domain Walls in a Scale-Covariant Theory of Gravitation

Axially symmetric space-time is considered in the presence of cosmic string source and thick domain walls in the frame work of a scale-covariant theory of gravitation. A relation between metric potential is assumed to get a determinate solution of the field equations of this theory. In this particular case, it is observed that the geometric (Nambu) string p-string (Takabayasi string) and Reddy string do not survive. It is also seen that the stiff (self-gravitating) domain walls do not exist in this theory.     

Bianchi Type-III Cosmic Strings and Domain Walls Cosmological Model in General Relativity

Bianchi type-III space time is considered in the presence of cosmic strings and thick domain walls source in the frame work of general relativity. Exact cosmological models using various cases of ρ=α λ and p=γ ρ are presented. It is observed that the behavior of these models (with cosmic strings and domain walls), based on their physical and kinematical properties, is found to be identical.     

Kaluza-Klein Universe with Cosmic Strings and Bulk Viscosity in a Scalar-Tensor Theory of Gravitation

A five dimensional Kaluza-Klein space-time is considered in the frame work of a scalar-tensor theory proposed by Saez and Ballester (Phys. Lett. A 113, 467, 1985) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional strings. A barotropic equation of state for the pressure and density is assumed to get a determinate solution of the field equations. Also the bulk viscous pressure is assumed to be proportional to the energy density. The physical and kinematical properties of the model are also discussed.     

On Fermionic Entangled State Representation and Fermionic Entangled Wigner Operator

By analogy with the bosonic bipartite entangled state we construct fermionic entangled state with the Grassmann numbers. The Wigner operator in the fermionic entangled state representation is introduced, whose marginal distributions are understood in an entangled way. The technique of integration within an ordered product （IWOP） of Fermi operators is used in our discussion.     

Fermionic atom laser

An output coupling of a magnetically trapped two-species Fermi gas to a untrapped species is considered which can be implemented using rf or optical Raman transitions. The process can be used to produce an intense output beam of fermionic atoms once the device reaches a threshold in the zero-temperature case. For finite temperatures there is no threshold, as the output current grows smoothly. This behavior, which is reminiscent of conventional optical and cavity-QED lasers, suggests the name fermionic atom laser for this device. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 1, 13–17 (10 July 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.