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Alignment of Quasar Polarizations on Large Scales Explained by Warped cosmic strings

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Journal of Modern Physics 2016年第6期7卷 501-509页

作者： Reinoud Jan Slagter Asfyon Astronomisch Fysisch Onderzoek Nederland Bussum The Netherlands Department of Physics University of Amsterdam Amsterdam The Netherlands

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 .

关键词： Quasar Polarization cosmic strings Warped Brane World Models U(1) Scalar-Gauge Field Multiple-Scale Analysis

Cosmological interpretation for the stochastic signal in pulsar timing arrays

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 43-50页

作者： Yu-Mei Wu Zu-Cheng Chen Qing-Guo Huang School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Astronomy Beijing Normal UniversityBeijing 100875China Advanced Institute of Natural Sciences Beijing Normal UniversityZhuhai 519087China Department of Physics and Synergistic Innovation Center for Quantum Effects and Applications Hunan Normal UniversityChangsha 410081China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China

The pulsar timing array(PTA)collaborations have recently reported compelling evidence for a stochastic signal consistent with a gravitational-wave *** this paper,we combine the latest data sets from NANOGrav,PPTA,and EPTA to explore cosmological interpretations for the PTA signal from first-order phase transitions,domain walls,and cosmic strings,*** find that the domain wall model is strongly disfavored with the Bayes factors compared with the first-order phase transitions and cosmic strings being 1/90 and 1/189,respectively,breaking the degeneracy among these models in individual data *** also find that:(1)a strong phase transition at temperatures below the electroweak scale is favored,and the bubble collisions make the dominant contribution to the energy density spectrum;(2)a small reconnection probability pstrings in(super)string theory is favored at the 95%confidence level,and ground-based detectors can further constrain the parameter space.

关键词： puslar timing arrays gravitational-wave background first-order phase transitions domain walls cosmic strings

Demonstration of the Symmetry Properties of Gravitational Metric Fields

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Chinese Physics Letters 2002年第4期19卷 470-473页

作者：邵亮 H.HODA 等 GraduateSchoolofScienceandEngineering IbarakiUniversityMito310-8512Japan DepartmentofMathematicalSciences IbarakiUniversityMito310-8512Japan

We calculate some Wilson loop functionals in a static sphere-symmetrical diagonal metric field and a gravitational metric field established by a cosmic string. Using the direction change of vector when it is parallel ... 详细信息

关键词： Metric Symmetry Cloning Vectors Metronidazole Fields cosmic strings FUNCTIONALS

The Motion of Spinning Particles in the Spacetime of a Black Hole with a cosmic String Topological Defect

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Chinese Physics Letters 2014年第9期31卷 12-16页

作者：赖楚瑜陈菊华王永久 College of Physics and Information Science Hunan Normal University Changsha 410081

The geodesic motion of pseudo-classical spinning particles in the spacetime of a black hole with the topological defect of a cosmic string, is analyzed. The constants of motion are derived in terms of solving the generalized killing equations for spinning space. The bound state orbits in a plane are discussed. Our results are permitted to be regarded as a semiclassical approximation to the quantum Dirac theory which holds to first order in the spin. The existence of the cosmic string factor b distinguishes the case from the one in Schwarzschild spacetime. When one chooses b = 1, our results reduce to the case of the Schwarzschild spacetime.

关键词： SCHWARZSCHILD black holes RESEARCH SPACE & time cosmic strings BOUND states (Quantum mechanics) QUANTUM theory BLACK holes (Astronomy)

Topological String in Quantum-Chromodynamical Chiral Phase Transitions

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Chinese Physics Letters 2005年第5期22卷 1300-1302页

作者：李云德 DepartmentofPhysics YunnanUniversityKunming650091

It is pointed out that if in heavy ion collision processes, the quark-gluonplasma SU(2) chiral phase transition really takes place and the phase transition is a second *** the topological string, i.e., the pi string, will be formed. The main effect of this phenomenonis that there will be a number of pions produced by decay of the T string in the final state. Thepions from the decay of the 7 string lead to the same effect of decreasing the Hanbury-Brown-Twisspeak in two-pion spectra which is just as that of the long-lived hadronic resonances. Atrelativistic heavy-ion collision and large hadron collision energies, it is expected that thefactors are about alpha similar to 0.7 - 0.9 and alpha similar to 0.6 - 0.85, respectively.

关键词： COSMOLOGICAL EXPERIMENTS cosmic strings DEFECTS

Bianchi Type-Ⅲ String Cosmological Models with Time Dependent Bulk Viscosity

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Chinese Physics Letters 2007年第2期24卷 585-588页

作者： BALI Raj PRADHAN Anirudh Department of Mathematics University of Rajasthan Jaipur-302 004 India Department'of Mathematics Hindu Post-Graduate College Zamania-232 331 Ghazipur India

Bianchi type-Ⅲ string cosmological models with bulk viscous fluid for massive string are investigated. To obtain the determinate model of the universe, we assume that the coeffcient of bulk viscosity ξ is inversely proportional to the expansion θ in the model and expansion θ in the model is proportional to the shear g. This leads to B =lC^n, where l and n are constants. Behaviour of the model in the presence and absence of bulk viscosity is discussed. The physical implications of the models are also discussed in detail.

关键词： GENERAL-RELATIVITY cosmic strings VISCOUS-FLUID QUARK MATTER DUST

Bianchi Type-I Cosmology with cosmic String and Bulk Viscosity

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Chinese Physics Letters 2003年第10期20卷 1674-1677页

作者：王行翔 DepartmentofPhysics AnhuiNormalUniversityWuhu241000

Some locally rotationally symmetric Bianchi type-I cosmological solutions for a cloud string with bulk viscosity are presented. In the first case, an equation of state ρ = kλ and the relation between metric potentials R = ASn are considered, and the solution represents shearing non-rotating model with the bulk viscosity ζρ1/2, where ρ is the rest energy density of the cloud of strings with particles attached to them, λ is the tension density of the cloud of strings, ζ is the coefficient of the bulk viscosity, R and S are only the functions of time t, while A and k are constant. In the second case, the constant coefficient of bulk viscosity is considered.

关键词： TIME FUNCTIONS Bianchi cosmic strings bulk viscosity Cosmology

Black Hole Hair in Higher Dimensions

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Communications in Theoretical Physics 2010年第2期53卷 285-290页

作者：曹超陈一新李剑龙 Zhejiang Institute of Modern Physics Zhejiang University

We study the property of matter in equilibrium with a static, spherically symmetric black hole in D- dimensional spacetime. It requires that this kind of matter has an equation of state ω≡pr/ρ = -n/（n ＋ 2k）, k, n ∈ N （where n 〉 1 corresponds to a mixture of vacuum matter and ＂hair＂ matter）, which seems to be independent of D. However, when we associate this result with specific models, we find that these hairy black holes can live only in some special dimensional spacetime：（i） D = 2 ＋ 2k/n while the black hole is surrounded by cosmic strings, which requires D is even or D ∈ N, depending on the value of n, this is consistent with some important results in superstring theory, it might reveal the relation between cosmic string and superstring in another aspect; （ii） the black hole can be surrounded by linear dilaton field only in 4-dimensional spacetime. In both cases, D = 4 is special. We also present some examples of such hairy black holes in higher dimensions, including a toy model with negative energy density.

关键词： black holes extra dimensions cosmic strings

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

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Communications in Theoretical Physics 2011年第5期55卷 931-941页

作者： Anirudh Pradhan Department of Mathematics Hindu Post-graduate College

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.

关键词： cosmic strings Bianchi-I universe variable cosmological constant Hubble's parameter