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Sep 23, 2013
09/13

by
Zhe Chang

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Exponential regularization of orthogonal and Anti-de Sitter (AdS) space is presented based on noncommutative geometry. We show that an adequately adopted noncommutative deformation of geometry makes the holography of higher dimensional quantum theory of gravity and low dimensional theory possible. Detail counting for observable degrees of freedom of quantum system of gravity in the bulk of noncommutative space SO_q(3) and the classical limit of its boundary surface S^2 is discussed. Taking...

Source: http://arxiv.org/abs/hep-th/9904101v1

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Sep 21, 2013
09/13

by
Zhe Chang

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This is a self-contained review on the theory of quantum group and its applications to modern physics. A brief introduction is given to the Yang-Baxter equation in integrable quantum field theory and lattice statistical physics. The quantum group is primarily introduced as a systematic method for solving the Yang-Baxter equation. Quantum group theory is presented within the framework of quantum double through quantizing Lie bi-algebra. Both the highest weight and the cyclic representations are...

Source: http://arxiv.org/abs/hep-th/9508170v1

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Sep 23, 2013
09/13

by
Zhe Chang

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The quantum Anti-de Sitter (AdS) group and quantum AdS space is discussed. Ways of getting the quantum AdS group from real forms of quantum orthogonal group are presented. Differential calculus on the quantum AdS space are also introduced. In particular, reality of differential calculus are given. We set up explicit relationships between quantum group and quantum algebra, which can be refereed as the quantum counterpart of the classical exponential. By this way, quantum AdS algebra is deduced...

Source: http://arxiv.org/abs/hep-th/9904091v1

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Jun 30, 2018
06/18

by
Sai Wang; Zhe Chang

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We propose the gravity's rainbow scenario as a possible alternative of the inflation paradigm to account for the flatness and horizon problems. We focus on studying the cosmological scalar perturbations which are seeded by the quantum fluctuations in the very early universe. The scalar power spectrum is expected to be nearly scale-invariant. We estimate the rainbow index $\lambda$ and energy scale $M$ in the gravity's rainbow scenario by analyzing the Planck temperature and WMAP polarization...

Topics: High Energy Physics - Theory, Astrophysics, General Relativity and Quantum Cosmology, Cosmology and...

Source: http://arxiv.org/abs/1412.3600

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Sep 21, 2013
09/13

by
Zhe Chang; Xin Li

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Gravitational field equations in Randers-Finsler space of approximate Berwald type are investigated. A modified Friedmann model is proposed. It is showed that the accelerated expanding universe is guaranteed by a constrained Randers-Finsler structure without invoking dark energy. The geodesic in Randers-Finsler space is studied. The additional term in the geodesic equation acts as repulsive force against the gravity.

Source: http://arxiv.org/abs/0901.1023v1

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Sep 19, 2013
09/13

by
Xin Li; Zhe Chang

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The weak field approximation of geodesics in Randers-Finsler space is investigated. We show that a Finsler structure of Randers space corresponds to the constant and sunward anomalous acceleration demonstrated by the Pioneer 10 and 11 data. The additional term in the geodesic equation acts as "electric force", which provides the anomalous acceleration.

Source: http://arxiv.org/abs/0909.3713v2

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Sep 17, 2013
09/13

by
Xin Li; Zhe Chang

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Finsler geometry is a natural and fundamental generalization of Riemann geometry. The Finsler structure depends on both coordinates and velocities. It is defined as a function on tangent bundle of a manifold. We use the Bianchi identities satisfied by Chern curvature to set up a gravitation theory in Berwald-Finsler space. The geometric part of the gravitational field equation is nonsymmetric in general. This indicates that the local Lorentz invariance is violated. Nontrivial solutions of the...

Source: http://arxiv.org/abs/0711.1934v1

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Sep 23, 2013
09/13

by
Zhe Chang; Sai Wang

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Recently, the Planck 2013 results showed possible evidence for a dipolar power modulation of the CMB temperature fluctuations at low--(\ell) multipoles. This anomaly might imply certain deviations from statistical isotropy. To incorporate the Planck's data into standard cosmological model, we propose an inflation model of the very early universe in an anisotropic spacetime. A generalized Friedmann-Robertson-Walker (FRW) metric is presented in the Randers-Finsler spacetime. We obtain the...

Source: http://arxiv.org/abs/1303.6058v4

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Jun 30, 2018
06/18

by
Xin Li; Zhe Chang

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The vacuum field equation in Finsler spacetime is equivalent to vanishing of Ricci scalar. We present an exact solution of the Finslerian vacuum field equation. The solution is similar to the Schwarzschild metric. It reduces to Schwarzschild metric while the Finslerian parameter vanishes. We get solutions of geodesic equation in such a Schwarzschild-like spacetime, and show that the geodesic equation returns to the counterpart in Newton's gravity at weak field approximation. It is proved that...

Topics: Physics, General Physics

Source: http://arxiv.org/abs/1401.6363

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Jul 20, 2013
07/13

by
Xin Li; Zhe Chang

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This is our reply to "Critical remarks on Finslerian modifications of gravity and cosmology by Zhe Chang and Xin Li", Sergiu I. Vacaru, Phys. Lett. B 690 (2010) 224. It is pointed out that the Finslerian modifications of gravity and cosmology (Zhe Chang and Xin Li, Phys. Lett. B 676 (2009) 173; {\it ibid} 668 (2008) 453) is a suggestion on the generalization of Einstein's gravity and cosmology, but not a proof for theorems in geometry. False or true of the theory should be tested by...

Source: http://arxiv.org/abs/1007.3820v1

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Sep 23, 2013
09/13

by
Zhe Chang; Ping Wang

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The standard Landau-Ginzburg scenario of phase transition is broken down for quantum phase transition. It is difficult to find an order parameter to indicate different phases for quantum fluctuations. Here, we suggest a topological description of the quantum phase transition for the XY model. The ground states are identified as a specialized U(1) principal bundle on the base manifold $S^2$. And then different first Chern numbers of U(1) principal bundle on the base manifold $S^2$ are associated...

Source: http://arxiv.org/abs/0801.1400v1

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Sep 22, 2013
09/13

by
Zhe Chang; Ning Wu

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We study the evolution of nearest-neighbor entanglement in the one dimensional Ising model with an external transverse field. The system is initialized as the so called "thermal ground state" of the pure Ising model. We analyze properties of generation of entanglement for different regions of external transverse fields. We find that the derivation of the time at which the entanglement reaches its first maximum with respect to the reciprocal transverse field has a minimum at the...

Source: http://arxiv.org/abs/1001.0844v1

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Sep 18, 2013
09/13

by
Zhe Chang; Xin Li

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A modified Newton's gravity is obtained as the weak field approximation of the Einstein's equation in Finsler space. It is found that a specified Finsler structure makes the modified Newton's gravity equivalent to the modified Newtonian dynamics (MOND). In the framework of Finsler geometry, the flat rotation curves of spiral galaxies can be deduced naturally without invoking dark matter.

Source: http://arxiv.org/abs/0806.2184v2

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Jul 19, 2013
07/13

by
Xin Li; Zhe Chang

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Verlinde has suggested that the gravity has an entropic origin, and a gravitational system could be regarded as a thermodynamical system. It is well-known that the equipartition law of energy is invalid at very low temperature. Therefore, entropic force should be modified while the temperature of the holographic screen is very low. It is shown that the modified entropic force is proportional to the square of the acceleration, while the temperature of the holographic screen is much lower than...

Source: http://arxiv.org/abs/1005.1169v2

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Sep 22, 2013
09/13

by
Zhe Chang; Sai Wang

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The GRAAL experiment could constrain the variations of the speed of light. The anisotropy of the speed of light may imply that the spacetime is anisotropic. Finsler geometry is a reasonable candidate to deal with the spacetime anisotropy. In this paper, the Lorentz invariance violation (LIV) of the photon sector is investigated in the locally Minkowski spacetime. The locally Minkowski spacetime is a class of flat Finsler spacetime and refers a metric with the anisotropic departure from the...

Source: http://arxiv.org/abs/1302.5486v2

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Jul 20, 2013
07/13

by
Xin Li; Zhe Chang

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We investigate possible quantum gravity (QG) effects on the gravitational deflection of light. Two forms of deformation of the Schwarzschild spacetime are proposed. The first ansatz is a given Finslerian line element, it could be regarded as a weak QG effect on the Schwarzschild spacetime. Starting from this ansatz, we deduce the deflection angle of the light ray which passes a weak gravitational source. The second ansatz could be regarded as a strong QG effect on the Schwarzschild spacetime....

Source: http://arxiv.org/abs/1007.0319v1

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Sep 18, 2013
09/13

by
Zhe Chang; Sai Wang

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Standard model with intrinsic Lorentz and CPT violations is proposed in a Finsler geometric framework. We present explicitly Lorentz and CPT--breaking Lagrangians of the matter fields and the gauge fields in locally Minkowski spacetime. The Lorentz invariance violation is found to be originated from the spacetime background deviating from the Minkowski one. Similarly, the CPT violation is determined by the behaviors of the locally Minkowski metric under the parity and time reversal operations....

Source: http://arxiv.org/abs/1209.3574v2

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Sep 21, 2013
09/13

by
Zhe Chang; Sai Wang

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Recently, Kostelecky [V.A. Kostelecky, Phys. Lett. B 701, 137 (2011)] proposed that the spontaneous Lorentz invariance violation (sLIV) is related to Finsler geometry. Finsler spacetime is intrinsically anisotropic and induces naturally Lorentz invariance violation (LIV). In this paper, the electromagnetic field is investigated in locally Minkowski spacetime. The Lagrangian is presented explicitly for the electromagnetic field. It is compatible with the one in the standard model extension...

Source: http://arxiv.org/abs/1204.2478v3

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Sep 21, 2013
09/13

by
Xin Li; Zhe Chang

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It is believed that the modification of Newtonian dynamics (MOND) is possible alternate for dark matter hypothesis. Although Bekenstein's TeVeS supplies a relativistic version of MOND, one may still wish a more concise covariant formulism of MOND. In this paper, within covariant geometrical framwork, we present another version of MOND. We show the spacetime structure of MOND with properties of Tully-Fisher relation and Lorentz invariance violation.

Source: http://arxiv.org/abs/1204.2542v1

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Sep 19, 2013
09/13

by
Zhe. Chang; Xin. Li

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Consequences of Schr\"{o}dinger's antipodal identification on quantum field theory in de Sitter space are investigated. The elliptic $\mathbb{Z}_2$ identification provides observers with complete information. We show that a suitable confinement on dimension of the elliptic de Sitter space guarantees the existence of globally defined spinors and orientable $dS/\mathbb{Z}_2$ manifold. In Beltrami coordinates, we give exact solutions of scalar and spinor fields. The CPT invariance of quantum...

Source: http://arxiv.org/abs/hep-th/0701068v2

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Sep 17, 2013
09/13

by
Zhe Chang; Xin Li

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Lorentz Invariance violation is a common feature of new physics beyond the standard model. We show that the symmetry of Randers spaces deduces a modified dispersion relation with characteristics of Lorentz Invariance violation. The counterparts of the Lorentz transformation in the Einstein's Special Relativity are presented explicitly. The coordinate transformations are unitary and form a group. Generators and algebra satisfied by them are different from usual Lorentz ones. The Randersian line...

Source: http://arxiv.org/abs/0711.0056v2

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Sep 23, 2013
09/13

by
Xin Li; Zhe Chang

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By making use of the weak gravitational field approximation, we obtain a linearized solution of the gravitational vacuum field equation in an anisotropic spacetime. The plane-wave solution and dispersion relation of gravitational wave is presented explicitly. There is possibility that the speed of gravitational wave is larger than the speed of light and the casuality still holds. We show that the energy-momentum of gravitational wave in the ansiotropic spacetime is still well defined and...

Source: http://arxiv.org/abs/1111.1383v2

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Sep 18, 2013
09/13

by
Zhe Chang; Xin Li

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Kinematics in Finsler space is used to study the propagation of ultra high energy cosmic rays particles through the cosmic microwave background radiation. We find that the GZK threshold is lifted dramatically in Randers-Finsler space. A tiny deformation of spacetime from Minkowskian to Finslerian allows more ultra-high energy cosmic rays particles arrive at the earth. It is suggested that the lower bound of particle mass is related with the negative second invariant speed in Randers-Finsler...

Source: http://arxiv.org/abs/0809.4762v1

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Sep 21, 2013
09/13

by
Xin Li; Zhe Chang

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The surface density $\Sigma$-map and the convergence $\kappa$-map of Bullet Cluster 1E0657-558 show that the center of baryonic matters separates from the center of gravitational force, and the distribution of gravitational force do not possess spherical symmetry. This hints that a modified gravity with difference to Newtonian inverse-square law at large scale, and less symmetry is worth investigating. In this paper, we study the dynamics in Randers-Finsler spacetime. The Newtonian limit and...

Source: http://arxiv.org/abs/1108.3443v1

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Sep 19, 2013
09/13

by
Xin Li; Zhe Chang

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Within the framework of projective geometry, we investigate kinematics and symmetry in $(\alpha,\beta)$ spacetime-one special types of Finsler spacetime. The projectively flat $(\alpha,\beta)$ spacetime with constant flag curvature is divided into four types. The symmetry in type A-Riemann spacetime with constant sectional curvature is just the one in de Sitter special relativity. The symmetry in type B-locally Minkowski spacetime is just the one in very special relativity. It is found that...

Source: http://arxiv.org/abs/1010.2020v2

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Jul 20, 2013
07/13

by
Zhe Chang; Han-Ying Guo

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Two kinds of realizations of symmetry on classical domains or the Euclidean version of AdS space are used to study AdS/CFT correspondence. Mass of free particles is defined as an AdS group invariant, the Klein-Gordon and Dirac equations for relativistic particles in the AdS space are set up as a mimic in the case of Minkowskian space. The bulk-boundary propagator on the AdS space is given by the Poisson kernel. Theorems on the Poisson kernel guarantee the existence and sole of the bulk-boundary...

Source: http://arxiv.org/abs/hep-th/9910136v1

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Sep 20, 2013
09/13

by
Zhe Chang; Cheng-Bo Guan

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We discuss radiation fields in a compact space of finite size instead of that in a cavity for investigating the coupled atom-radiation field system. Representations of $T(1)\times SO(4)$ group are used to give a formulation for kinematics of the radiation fields. The explicit geometrical parameter dependence of statistical properties of radiation fields is obtained. Results show remarkable differences from that of the black-body radiation system in free space.

Source: http://arxiv.org/abs/quant-ph/0404035v1

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Sep 24, 2013
09/13

by
Zhe Chang; Xin-Bing Huang

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We calculate the vacuum energy density by taking account of different massive scalar fields in AdS spacetime. It is found that the mass spectrum of a scalar field in AdS spacetime is discrete because of a natural boundary condition. The results match well with the observed cosmological constant.

Source: http://arxiv.org/abs/astro-ph/0103437v3

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Jun 30, 2018
06/18

by
Zhe Chang; Hai-Nan Lin

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The polarimetric measurement on the prompt phase of GRB 100826A shows that the polarization angle changes $\sim 90^{\circ}$ between two adjacent time intervals. We will show that this phenomenon can be naturally interpreted in the framework of the magnetic-dominated jet (MDJ) model. The MDJ model suggests that the bulk Lorentz factor of the outflow increases as $\Gamma\propto r^{1/3}$, until reaching a saturated value $\Gamma_{\rm sat}$. Electrons move in the globally ordered magnetic field...

Topics: High Energy Astrophysical Phenomena, Astrophysics

Source: http://arxiv.org/abs/1405.0844

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Jun 30, 2018
06/18

by
Zhe Chang; Hai-Nan Lin

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Type-Ia supernovae (SNe Ia) are often used as the standard candles to probe the anisotropic expansion of the Universe. In this paper, we make a comprehensive comparison between the hemisphere comparison (HC) method and dipole-fitting (DF) method in searching for the cosmological preferred direction using the Union2 dataset, a compilation of 557 well-calibrated SNe Ia. We find that the directions of the faintest SNe Ia derived from these two methods are approximately opposite. Monte Carlo...

Topics: Astrophysics, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1411.1466

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Sep 20, 2013
09/13

by
Zhe Chang; Zhi-zhong Xing

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Possible effects of noncommutative geometry on weak CP violation and unitarity triangles are discussed by taking account of a simple version of the momentum-dependent quark mixing matrix in the noncommutative standard model. In particular, we calculate nine rephasing invariants of CP violation and illustrate the noncommutative CP-violating effect in a couple of charged D-meson decays. We also show how inner angles of the deformed unitarity triangles are related to CP-violating asymmetries in...

Source: http://arxiv.org/abs/hep-ph/0204255v2

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Sep 22, 2013
09/13

by
Zhe Chang; Shao-Xia Chen

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By making use of the double-time Green function technique, we study thermodynamics of a deformed Bose gas, which describes well properties of density intensive photonic gas and radiation fields of the early universe. General form of statistical distribution function is obtained. We show explicitly the expression of the distribution function in some limitation cases. The free energy, equation of state, specific heat and other thermodynamic properties of the deformed Bose gas are presented.

Source: http://arxiv.org/abs/cond-mat/0205208v2

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Jun 30, 2018
06/18

by
Zhe Chang; Hai-Nan Lin

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The high polarization observed in the prompt phase of some gamma-ray bursts (GRBs) arouses extensive studies on the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron-self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons...

Topics: High Energy Astrophysical Phenomena, Astrophysics

Source: http://arxiv.org/abs/1407.1651

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Sep 22, 2013
09/13

by
Xin Li; Zhe Chang; Xiaohuan Mo

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The Killing equation for a general Finsler space is set up. It is showed that the Killing equation of $(\alpha,\beta)$ space can be divided into two parts. One is the same with Killing equation of a Riemannian metric, another equation can be regarded as a constraint. The solutions of Killing equations present explicitly the isometric symmetry of Finsler space. We find that the isometric group of a special case of $(\alpha,\beta)$ space is the same with the symmetry of Very Special Relativity...

Source: http://arxiv.org/abs/1001.2667v2

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Sep 22, 2013
09/13

by
Xin Li; Zhe Chang; Minghua Li

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We investigate a matter dominated navigation cosmological model. The influence of a possible drift (wind) in the navigation cosmological model makes the spacetime geometry change from Riemannian to Finslerian. The evolution of the Finslerian Universe is governed by the same gravitational field equation with the familiar Friedmann-Robertson-Walker one. However, the change of space geometry from Riemannian to Finslerian supplies us a new relation between the luminosity distant and redshift. It is...

Source: http://arxiv.org/abs/1001.0066v2

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Jul 20, 2013
07/13

by
Zhe Chang; Xin Li; Sai Wang

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Recently, Cohen and Glashow [A.G. Cohen, S.L. Glashow, Phys. Rev. Lett. {\bf 107}, 181803 (2011)] pointed out that the superluminal neutrinos reported by the OPERA would lose their energy rapidly via the Cherenkov-like process. The Cherenkov-like process for the superluminal particles would be forbidden if the principle of special relativity holds in any frame instead violated with a preferred frame. We have proposed that the Finslerian special relativity could account for the data of the...

Source: http://arxiv.org/abs/1203.5569v1

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Sep 21, 2013
09/13

by
Zhe Chang; Sai Wang; Xin Li

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Recent observations on the quasar absorption spectra supply evidence for the variation of the fine structure constant $\alpha$. In this paper, we propose another interpretation of the observational data on the quasar absorption spectra: a scenario with spacetime inhomogeneity and anisotropy. Maybe the spacetime is characterized by the Finsler geometry instead of the Riemann one. The Finsler geometry admits fewer symmetries than the Riemann geometry does. We investigate the Finslerian geodesic...

Source: http://arxiv.org/abs/1106.2726v3

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Sep 18, 2013
09/13

by
Zhe Chang; Xin Li; Sai Wang

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The superluminal behaviors of neutrinos were reported by the OPERA collaboration recently. It was also noticed by Cohen and Glashow that, in standard quantum field theory, the superluminal neutrinos would lose their energy via the Cherenkov-like process rapidly. Finslerian special relativity may provide a framework to cooperate with the OPERA neutrino superluminality without Cherenkov-like process. We present clearly the symmetry, causal structure and superluminality in Finsler spacetime. The...

Source: http://arxiv.org/abs/1201.1368v1

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Jun 26, 2018
06/18

by
Xin Li; Sai Wang; Zhe Chang

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We suggest the universe is Finslerian in the stage of inflation. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. The primordial power spectrum is given for quantum fluctuation of the inflation field. It depends not only on the magnitude of wavenumber but also on the preferred direction. We derive the gravitational field equations in the perturbed Finslerian background spacetime, and obtain a conserved quantity outside the Hubble horizon. The angular...

Topics: Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology, Astrophysics

Source: http://arxiv.org/abs/1502.02256

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Sep 23, 2013
09/13

by
Zhe Chang; Xin Li; Sai Wang

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The OPERA collaboration recently reported that muon neutrinos could be superluminal. More recently, Cohen and Glashow pointed that such superluminal neutrinos would be suppressed since they lose their energies rapidly via bremsstrahlung. In this Letter, we propose that Finslerian nature of spacetime could account for the superluminal phenomena of particles. The Finsler spacetime permits the existence of superluminal behavior of particles while the casuality still holds. A new dispersion...

Source: http://arxiv.org/abs/1110.6673v1

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Sep 20, 2013
09/13

by
Zhe Chang; Hai-Nan Lin; Yunguo Jiang

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Recent observations by the Fermi-LAT showed that there are delayed arrivals of GeV photons relative to the onset of MeV photons in some GRBs. In order to avoid a large optical depth, the minimal value of the Lorentz factor has been estimated to be higher than 1000 in some brightest bursts. In this paper, we present a detailed calculation of the time delay between the MeV and GeV photons in the framework of the magnetic-dominated jet model. We find that the time delay strongly depends on the...

Source: http://arxiv.org/abs/1205.3572v3

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Jun 30, 2018
06/18

by
Duokui Yan; Rongchang Liu; Geng-zhe Chang

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In this paper, we study the multiple integral $ \displaystyle I= \int_0^1 \int_0^1 \dots \int_0^1 f(x_1+x_2 + \dots +x_n) \, dx_1 \, dx_2 \, \dots \, dx_n$. A general formula of $I$ is presented. As an application, the integral $I$ with $f(x)= \log \Gamma(x)$ is evaluated. We show that the values of $I$ share a common formula for all $n \in \mathbb{N}$. The subsidiary computational challenges are substantial and interesting in their own right.

Topics: Mathematics, Classical Analysis and ODEs

Source: http://arxiv.org/abs/1404.5143

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Sep 18, 2013
09/13

by
Zhe Chang; Yunguo Jiang; Hai-Nan Lin

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Possible Lorentz invariance violation (LIV) has been investigated for a long time based on observations of GRBs . These arguments relied on the assumption that photons with different energy are emitted at the same place and time. In this work, we try to take account of the intrinsic time delay $\Delta t_{\rm int}$ between emissions of low and high energy photons by using the magnetic jet model. The possible LIV effects are discussed in a unified scenario both for long and short {\it...

Source: http://arxiv.org/abs/1201.3413v3

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Sep 23, 2013
09/13

by
Zhe Chang; Ping Wang; Ying-Hong Zheng

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We propose an Ashkin-Teller like model for elastic response of DNA molecule to external force and torque. The base-stacking interaction is described in a simple and uniform way. We obtain the phase diagram of dsDNA, and in particular, the transition from B form to the S state induced by stretching and twisting. The elastic response of the ssDNA is presented also in a unified formalism. The close relation of dsDNA molecule structure with elastic response is shown clearly. The calculated folding...

Source: http://arxiv.org/abs/0801.1705v1

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Jun 29, 2018
06/18

by
Hai-Nan Lin; Xin Li; Zhe Chang

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The spectra of gamma-ray bursts (GRBs) in a wide energy range can usually be well described by the Band function, which is a two smoothly jointed power laws cutting at a breaking energy. Below the breaking energy, the Band function reduces to a cut-off power law, while above the breaking energy it is a simple power law. However, for some detectors (such as the Swift-BAT) whose working energy is well below or just near the breaking energy, the observed spectra can be fitted to cut-off power law...

Topics: Astrophysics, High Energy Astrophysical Phenomena, Cosmology and Nongalactic Astrophysics, High...

Source: http://arxiv.org/abs/1604.02285

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Jun 29, 2018
06/18

by
Hai-Nan Lin; Xin Li; Zhe Chang

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Linear polarization have been observed in both the prompt phase and afterglow of some bright gamma-ray bursts (GRBs). Polarization in the prompt phase spans a wide range, and may be as high as $\gtrsim 50\%$. In the afterglow phase, however, it is usually below $10\%$. According to the standard fireball model, GRBs are produced by synchrotron radiation and Compton scattering process in a highly relativistic jet ejected from the central engine. It is widely accepted that prompt emissions occur...

Topics: Astrophysics, High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1612.05324

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Jun 29, 2018
06/18

by
Hai-Nan Lin; Xin Li; Zhe Chang

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We use two different methods, i.e., dipole-fitting (DF) and hemisphere comparison (HC), to search for the anisotropic signals hiding in the Union2.1 data set. We find that the directions of maximum matter density derived using these two methods are about $114^{\circ}$ away from each other. We construct four Union2.1-like mock samples to test the statistical significance of these two methods. It is shown that DF method is statistically significant, while HC method is strongly biased by the...

Topics: Astrophysics, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1604.07505

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4.0

Jun 29, 2018
06/18

by
Yu Sang; Hai-Nan Lin; Zhe Chang

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Einstein's equivalence principle (EEP) can be tested by the time delay between photons with different energies passing through a gravitational field. As one of the most energetic explosions in the Universe, gamma-ray bursts (GRBs) provide an effective tool to test the accuracy of EEP. In this paper, we use the continuous spectra of 20 short GRBs detected by the Swift/BAT to test the validity of EEP. Taking the duration of GRBs as the upper limit of the time delay induced by EEP violation...

Topics: Astrophysics, High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1605.02834

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61

Sep 19, 2013
09/13

by
Zhe Chang; Ming-Hua Li; Xin Li

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In Verlinde's entropic force scenario of gravity, Newton's laws and Einstein equations can be obtained from the first pinciples and general assumptions. However, the equipartition law of energy is invalid at very low temperatures. We show clearly that the threshold of the equipartition law of energy is related with horizon of the universe. Thus, a one-dimension Debye (ODD) model in the direction of radius of the modified entropic force (MEF) maybe suitable in description of the accelerated...

Source: http://arxiv.org/abs/1009.1506v3

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46

Sep 19, 2013
09/13

by
Zhe Chang; Ming-Hua Li; Xin Li

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Gravitational field equations in Randers-Finsler space of approximate Berwald type are investigated. A modified Friedmann equation and a new luminosity distance-redshift relation is proposed. A best-fit to the Type Ia supernovae (SNe) observations yields that the $\Omega_{\Lambda}$ in the $\Lambda$-CDM model is suppressed to almost zero. This fact indicates that the astronomical observations on the Type Ia SNe can be described well without invoking any form of dark energy. The best-fit age of...

Source: http://arxiv.org/abs/1009.1509v2