arXiv subjects

X. Cai

Publications and source records attributed to X. Cai.

881 records · Page 49Linked to original sources

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↗

arXiv1998

Local Spontaneous Symmetry Breaking for Film System Within Scalar $ϕ^4$ Model for Phase Transition

The difficulty is analysed in evaluating fluctuations in phase transition of finite-size system at temperature far below the critical point. Film system is discussed with one-component order parameter $ϕ^4$ model for phase transition. Non-trivial vacuum state corresponding to minimum Hamiltonian is given approximately for various boundary conditions. It is shown that the spontaneous symmetry breaking plays an important role for such systems, and that perturbative calculations can be done safely when the effect of the vacuum state or the local spontaneous symmetry breaking is taken into consideration.

cond-mat↗

arXiv1997

Multiplicity difference correlators under first-order QGP phase transition

The multiplicity difference correlators between two well-separated bins in high-energy heavy-ion collisions are studied as a means to detect evidence of a first-order quark-hadron phase transition. Analytical expressions for the scaled factorial moments of multiplicity difference distribution are obtained for small bin size $δ$ with mean multiplicity in the bin ${\bar s}\le 1.0$ within Ginzburg-Landau description. The scaling behaviors between the moments are still valid, though they behave completely different from the so-called intermittency patterns. A universal exponent $γ=1.4066$ is given to describe the dynamical fluctuations in the phase transition in small $δ$ limit.

hep-ph↗

arXiv1997

Analytical investigation for multiplicity difference correlators under QGP phase transition

It is suggested that the study of multiplicity difference correlators between two well-separated bins in high-energy heavy-ion collisions can be used as a means to detect evidence of a quark-hadron phase transition. Analytical expressions for the scaled factorial moments of multiplicity difference distribution are obtained in a kinetical region ${\bar s}\le 0.3$ within Ginzburg-Landau description. It is shown that the scaling behaviors between the moments are still valid, though the behaviors of the moments with respect to the bin size are completely different from the so-called intermittency patterns. A universal exponent $γ$ is given to describe the dynamical fluctuations in the phase transition.

hep-ph↗

arXiv1997

Finite-Size Effects in Critical Phenomena from Mean Field Approach with $ϕ^4$ Model

The finite-size effects in critical phenomena of a thin film system are studied from a mean field (MF) approach with $ϕ^4$ model for second-order phase transition. The influence of boundary condition on the critical properties are emphasized. Scaling functions for relative free-energy and relative specific heat capacity are given.

cond-mat↗

arXiv1996

On the Polarization Dependence of Electromagnetic Vertex for Proton

The polarization dependence of the electromagnetic vertex for polarized proton is discussed. Such a dependence is shown to be a result of gluon polarization and gluon interactions with the constituents within proton. One more form factor is introduced to give such a dependence in the electromagnetic vertex for proton. Due the polarization dependence of the vertex, a nonzero single-spin asymmetry for unpolarized lepton scattering off transversely polarized proton is predicted.

hep-ph↗

arXiv1996

A New Perturbation Theory of Finite-Size Effects Near Critical Point

A new perturbation theory is proposed for studying finite-size effects near critical point of the $ϕ^4$ model with a one-component order parameter. The new approach is based on the techniques of generating functional and functional derivative with respect to external source field and can be used for temperatures both above and below the critical point of the bulk system. It is shown that this approach is much simpler comparing with available perturbation theories. Particularly, this new method avoids renormalization in calculating many physical quantities such as correlation functions etc..

cond-mat↗