arXiv subjects

X. Cai

Publications and source records attributed to X. Cai.

At least 883 records · Page 49Linked to original sources

arXiv2001

Extra Spin-Rotation Coupling Effect in a Radiating Kerr Space-time

Source-less wave equations are derived for massless scalar, neutrino and electromagnetic perturbations of a radiating Kerr space-time, and the Hawking radiation of massless particles with spin $s =0, 1/2$ and 1 in this geometry is investigated by using a method of the generalized tortoise coordinate transformation. An extra interaction between the spin of particles and the rotation of the hole displays in the thermal spectra of Hawking radiation of massless particles with spin $s = 1/2, 1$ in the evaporating Kerr space-time. The character of such effect is its obvious dependence on different helicity states of particles with higher spin.

gr-qc↗

arXiv2001

Asymmetry of Hawking Radiation of Dirac Particles in a Charged Vaidya - de Sitter Black Hole

The Hawking radiation of Dirac particles in a charged Vaidya - de Sitter black hole is investigated by using the method of generalized tortoise coordinate transformation. It is shown that the Hawking radiation of Dirac particles does not exist for $P_1, Q_2$ components, but for $P_2, Q_1$ components it does. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein-Gordon particles.

gr-qc↗

arXiv2001

Hawking Radiation of Dirac Particles in a Variable-mass Kerr Space-time

Hawking effect of Dirac particles in a variable-mass Kerr space-time is investigated by using a method called as the generalized tortoise coordinate transformation. The location and the temperature of the event horizon of the non-stationary Kerr black hole are derived. It is shown that the temperature and the shape of the event horizon depend not only on the time but also on the angle. However, the Fermi-Dirac spectrum displays a residual term which is absent from that of Bose-Einstein distribution.

gr-qc↗

arXiv2000

Four Quantum Conservation Laws for Black Hole Stationary Equilibrium Radiation Processes

The classical first law of thermodynamics for a Kerr-Newman black hole (KNBH) is generalized to a law in quantum form on the event horizon. Then four quantum conservation laws on the KNBH equilibrium radiation process are derived. The Bekenstein-Hawking relation ${\cal{S}}={\cal{A}}/4$ is exactly established. It can be inferred that the classical entropy of black hole arises from the quantum entropy of field quanta or quasi-particles inside the hole.

hep-th↗

arXiv2000

Exact equqations and scaling relations for f-avalanche in the Bak-Sneppen evolution model

Infinite hierarchy of exact equations are derived for the newly-observed f-avalanche in the Bak-Sneppen evolution model. By solving the first order exact equation, we found that the critical exponent which governs the divergence of the average avalanche size, is exactly 1 (for all dimensions), confirmed by the simulations. Solution of the gap equation yields another universal exponent, denoting the the relaxation to the attractor, is exactly 1. We also establish some scaling relations among the critical exponents of the new avalanche.

cond-mat.stat-mech↗

arXiv2000

Different hierarchy of avalanches observed in the Bak-Sneppen evolution model

We introduce a new quantity, average fitness, into the Bak-Sneppen evolution model. Through the new quantity, a different hierarchy of avalanches is observed. The gap equation, in terms of the average fitness, is presented to describe the self-organization of the model. It is found that the critical value of the average fitness can be exactly obtained. Based on the simulations, two critical exponents, avalanche distribution and avalanche dimension, of the new avalanches are given.

cond-mat.stat-mech↗

arXiv2000

Generalized Laws of Black Hole Thermodynamics and Quantum Conservation Laws on Hawking Radiation Process

Four classical laws of black hole thermodynamics are extended from exterior (event) horizon to interior (Cauchy) horizon. Especially, the first law of classical thermodynamics for Kerr-Newman black hole (KNBH) is generalized to those in quantum form. Then five quantum conservation laws on the KNBH evaporation effect are derived in virtue of thermodynamical equilibrium conditions. As a by-product, Bekenstein-Hawking's relation $ S=A/4 $ is exactly recovered.

gr-qc↗

arXiv2000

Spatial-temporal correlations in the process to self-organized criticality

A new type of spatial-temporal correlation in the process approaching to the self-organized criticality is investigated for the two simple models for biological evolution. The change behaviors of the position with minimum barrier are shown to be quantitatively different in the two models. Different results of the correlation are given for the two models. We argue that the correlation can be used, together with the power-law distributions, as criteria for self-organized criticality.

physics.bio-ph↗

arXiv2000

Perturbative calculation of the scaled factorial moments in second-order quark-hadron phase transition within the Ginzburg-Landau description

The scaled factorial moments $F_q$ are studied for a second-order quark-hadron phase transition within the Ginzburg-Landau description. The role played by the ground state of the system under low temperature is emphasized. After a local shift of the order parameter the fluctuations are around the ground state, and a perturbative calculation for $F_q$ can be carried out. Power scaling between $F_q$'s is shown, and a universal scaling exponent $ν\simeq 1.75$ is given for the case with weak correlations and weak self-interactions.

hep-ph↗

arXiv1999

Maxwell-Boltzmann, Bose-Einstein, Fermi-Dirac statistical entropies in a D-dimensional stationary axisymmetry space-time

Statistical entropies of a general relativistic ideal gas obeying Maxwell-Boltzmann, Bose-Einstein and Fermi-Dirac statistics are calculated in a general axisymmetry space-time of arbitrary dimension. This general formation can be used to discuss the entropy of a quantum field not only in the flat space-time but also in a curved space-time. It can also be used to compare the entropies in different dimensional space-times. Analytical expressions for the thermodynamic potentials are presented, and their behaviors in the high or low temperature approximation are discussed. The entropy of a quantum field is shown to be proportional to the volume of optical space or that of the dragged optical space only in the high temperature approximation or in the zero mass case. In the case of a black hole, the entropy of a quantum field at the Hartle-Hawking temperature is proportional to the horizon "area" if and only if the horizon is located at the light velocity surface.

gr-qc↗

arXiv1999

A new hierarchy of avalanches observed in Bak-Sneppen evolution model

A new quantity, average fitness, is introduced in Bak-Sneppen evolution model. Through this new quantity, a new hierarchy of avalanches is observed in the evolution of Bak-Sneppen model. An exact gap equation, governing the self-organization of the model, is presented. It is found that the self-organized threshold of the new quantity can be exactly obtained. Two basic exponents, avalanche distribution and avalanche dimension are given through simulations of one- and two-dimensional Bak-Sneppen models. It is suggested that this new quantity may be a good quantity in determining the emergence of criticality.

cond-mat.stat-mech↗

arXiv1999

Quark rotation asymmetry and baryon magnetic moments

Quark rotation asymmetry is proposed in calculating baryon magnetic moments. After taking into account interactions enforced on constituent quarks, assumed to be linear and Coulomb potentials, respectively, and the quark rotation asymmetry, we fit the theoretical values, based on two more hypotheses and several other reasonable assumptions, of baryon magnetic moments with those from experiments. The good fitting results show the necessity of the consideration of quark rotation asymmetry within baryon.

nucl-th↗

arXiv1999

A model of evolution with interaction strength

Interaction strength is introduced in a model of evolution in d-dimension space. It is realized by imposing a constraint concerning 2d differences of fitnesses between that of any extremal site and those of its 2d nearest neighbours at each time step in the evolution of the model. For any given interaction strength between 0 and 1 the model can self-organize to a critical state. Two exact equations found in Bak-Sneppen model still hold in our model for different interaction strength. Simulations of one- and two-dimensional models for ten different values of interaction are given. It is found that self-organized threshold decreases with interaction strength increasing. It is also shown that the critical exponent, and two basic exponents, avalanche distribution, and avalanche dimension, are interaction strength dependent.

cond-mat.stat-mech↗

arXiv1999

Exact Solutions to Sourceless Charged Massive Scalar Field Equation on Kerr-Newman Background

The separated radial part of a sourceless massive complex scalar field equation on the Kerr-Newman black hole background is shown to be a generalized spin-weighted spheroidal wave equation of imaginary number order. While the separated angular part is an ordinary spheroidal wave equation. General exact solutions in integral forms and in power series expansion as well as several special solutions with physical interest are given for the radial equation in the non-extreme case. In the extreme case, power series solution to the radial equation is briefly studied. Recurrence relations between coefficients in power series expansion of general solutions and connection between the radial equation are discussed in both cases.

gr-qc↗

arXiv1999

Four Quantum Conservation Laws on Black Hole Equilibrium Radiation Process and Quantum Black Hole Entropy

The classical first law of thermodynamic for Kerr-Newmann black hole (KNBH) is generalized to that in quantum form on event horizon. Then four quantum conservation laws on the KNBH equilibrium radiation process are derived, and Bekenstein-Hawking's relation S=A/4 is recovered. It can be argued that the classical entropy of black hole arise from the quantum entropy of field quanta or quasi-particles inside the hole.

gr-qc↗

arXiv1998

Effect of spatial fluctuations on the scaled factorial moments in second-order quark-hadron phase transition within Ginzburg-Landau description

The scaled factorial moments in second-order quark-hadron phase transition are reexamined within the Ginzburg-Landau description, with the spatial fluctuations of phase angle of the complex field $ϕ$ taken into account rigorously. Scaling behaviors between $F_q$ and $F_2$ are shown, and the exponent $ν$ is found very close to the one without spatial fluctuations.

hep-ph↗

arXiv1998

Novel Scaling Behavior for the Multiplicity Distribution under Second-Order Quark-Hadron Phase Transition

Deviation of the multiplicity distribution $P_q$ in small bin from its Poisson counterpart $p_q$ is studied within the Ginzburg-Landau description for second-order quark-hadron phase transition. Dynamical factor $d_q\equiv P_q/p_q$ for the distribution and ratio $D_q\equiv d_q/d_1$ are defined, and novel scaling behaviors between $D_q$ are found which can be used to detect the formation of quark-gluon plasma. The study of $d_q$ and $D_q$ is also very interesting for other multiparticle production processes without phase transition.

hep-ph↗

arXiv1998

Scaling Behavior of Multiplicity Distribution under First-Order Quark-Hadron Phase Transition

Multiplicity distribution in small bins is studied within the Ginzburg-Landau description for first-order quark-hadron phase transition. Direct comparison of the distribution with a Poisson one (with the same average) is made. Dynamical factor $d_q$ for the distributionand ratio $D_q\equiv d_q/d_1$ are studied, and novel scaling behaviors between $D_q$ are found which can be used to detect the formation of quark-gluon plasma.

hep-ph↗