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Mu-Lin Yan

Publications and source records attributed to Mu-Lin Yan.

At least 73 records · Page 4Linked to original sources
arXiv2000

Statistical Entropy of a Stationary Dilaton Black Hole from Cardy Formula

With Carlip's boundary conditions, a standard Virasoro subalgebra with corresponding central charge for stationary dilaton black hole obtained in the low-energy effective field theory describing string is constructed at a Killing horizon. The statistical entropy of stationary dilaton black hole yielded by standard Cardy formula agree with its Bekenstein-Hawking entropy only if we take period $ T$ of function $v$ as the periodicity of the Euclidean black hole. On the other hand, if we consider first-order quantum correction then the entropy contains a logarithmic term with a factor $-{1/2}$, which is different from Kaul and Majumdar's one, $-{3/2}$. We also show that the discrepancy is not just for the dilaton black hole, but for any one whose corresponding central change takes the form $\frac{c}{12}= \frac{A_H}{8πG}\frac{2π}{κT}$.

gr-qc↗
arXiv2000

Entropies of Rotating Charged Black Holes from Conformal Field Theory at Killing Horizons

The covariant phase technique is used to compute the constraint algebra of the stationary axisymmetric charged black hole. A standard Virasoro subalgebra with corresponding central charge is constructed at a Killing horizon with Carlip's boundary conditions. For the Kerr-Newman black hole and the Kerr-Newman-AdS black hole, the density of states determined by conformal fields theory methods yields the statistical entropy which agrees with the Bekenstein-Hawking entropy.

gr-qc↗
arXiv2000

Rigorous Effective Field Theory Study on Pion Form Factor

We study $e^+e^-\toπ^+π^-$ cross section and phase shift of $I=l=1$ $π-π$ scattering below 1GeV in framework of chiral constituent quark model. The results including all order contribution of the chiral perturbation expansion and all one-loop effects of pseudoscalar mesons, but without any adjust parameters. Width of $ρ$ predicted by the model strongly depends on transition momentum-square $q^2$. We show that the mass pamameter of $ρ$-meson in its propagator is very different from its physical mass due to momentum-dependent width of $ρ$. The mass difference between $ρ^0$ and $ω$ are predicted successfully. The rigorous theoretical prediction on $e^+e^-\toπ^+π^-$ cross section and the phase shift in $I=l=1$ $π-π$ scattering agree with data excellentlly.

hep-ph↗
arXiv2000

CP violation in psi(2S) -> J/psi pi pi processes

We propose to search for CP-violating effects in the decay psi(2S)->J/psi+pi+pi. The scheme has the advantage that one does not need to track two or more CP-conjugate processes. Model independent amplitudes are derived for this purpose. The fact that leading CP violating terms are O(k) under low energy expansion and the processes are flavor disconnected make the measurement of these CP breaking parameters practical. Our results can be extended to the case of Upsilon(2S)->Upsilon(1S)+pi+pi and Upsilon(3S)->Upsilon(2S)+pi+pi straightforwardly.

hep-ph↗
arXiv1999

A Quantum Integrable System with Two Colour-Components in Two Dimensions

The Davey-Stewartson 1(DS1) system[9] is an integrable model in two dimensions. A quantum DS1 system with 2 colour-components in two dimensions has been formulated. This two-dimensional problem has been reduced to two one-dimensional many-body problems with 2 colour-components. The solutions of the two-dimensional problem under consideration has been constructed from the resulting problems in one dimensions. For latters with the $δ$-function interactions and being solved by the Bethe ansatz, we introduce symmetrical and antisymmetrical Young operators of the permutation group and obtain the exact solutions for the quantum DS1 system. The application of the solusions is discussed.

hep-th↗
arXiv1999

Large N_c Expansion in Chiral Quark Model of Mesons

We study SU(3)$_L\timesSU(3)_R$ chiral quark model of mesons up to the next to leading order of $1/N_c$ expansion. Composite vector and axial-vector mesons resonances are introduced via non-linear realization of chiral SU(3) and vector meson dominant. Effects of one-loop graphs of pseudoscalar, vector and axial-vector mesons is calculated systematically and the significant results are obtained. We also investigate correction of quark-gluon coupling and relationship between chiral quark model and QCD sum rules. Up to powers four of derivatives, chiral effective lagrangian of mesons is derived and evaluated to the next to leading order of $1/N_c$. Low energy limit of the model is examined. Ten low energy coupling constants $L_i(i=1,2,...,10)$ in ChPT are obtained and agree with ChPT well.

hep-ph↗
arXiv1999

Entropies of the general nonextreme stationary axisymmetric black hole: statistical mechanics and thermodynamics

Starting from metric of the general nonextreme stationary axisymmetric black hole in four-dimensional spacetime, both statistical-mechanical and thermodynamical entropies are studied. First, by means of the "brick wall" model in which the Dirichlet condition is replaced by a scattering ansatz for the field functions at the horizon and with Pauli-Villars regularization scheme, an expression for the statistical-mechanical entropy arising from the nonminimally coupled scalar fields is obtained. Then, by using the conical singularity method Mann and Solodukhin's result for the Kerr-Newman black hole (Phys. Rev. D54, 3932(1996)) is extended to the general stationary black hole and the nonminimally coupled scalar field. We last shown by comparing the two results that the statistical-mechanical entropy and one-loop correction to the thermodynamical entropy are equivalent for coupling $ξ\leq 0$. After renormalization, a relation between the two entropies is given.

gr-qc↗
arXiv1999

Electromagnetic self-energies of the neutral pions: Contributions from vector resonances

By employing vector meson dominance to establish the electromagnetic interactions of hadrons, the electromagnetic self-energy of the neutral pions, which receives the contributions from the vector resonances due to chiral anomaly, is evaluated. This part of the electromagentic mass, which can contribute to the mass difference of $π^\pm-π^0$, is finite and as expected, is smaller than the contributions due to isospin symmetry breaking and electromagnetic chiral logs corrections, however, could be compared with the contribution from the short distance QCD.

hep-ph↗
arXiv1999

Quantum entropy of the general non-extreme stationary axisymmetric black hole due to minimally coupled quantum scalar field

By using the 't Hooft "brick wall" model and the Pauli-Villars regularization scheme we calculate the statistical-mechanical entropy arising from the minimally coupled scalar fields which rotate with the azimuthal angular velocity $Ω_0=Ω_H$ ($Ω_H$ is the angular velocity of the black hole horizon) in the general four-dimensional non-extreme stationary axisymmetric black hole space-time. We also show, for the Kerr-Newman and the Einstein-Maxwell dilaton-axion black holes, that the statistical-mechanical entropy obtained from our derivation and the quantum thermodynamical entropy by the conical singularity method are equivalent.

gr-qc↗
arXiv1999

Electromagnetic self-energies of vector mesons and electromagnetic mass anomaly of the massive Yang-Mills particles

A systematic method developed by the authors to evaluate the one-loop electromagnetic self-energies of the low-lying mesons is extended to the calculation of the vector sector including $ρ$, $ω$, and $ϕ$-mesons. The theoretical result of $ρ^0-ρ^\pm$ electromagnetic mass difference is in agreement with the measurements. An interesting effect called as electromagnetic mass anomaly of the massive Yang-Mills particles is further discussed. There is no new parameter in this study.

hep-ph↗
arXiv1999

Covariant amplitudes for mesons

We show how to construct covariant amplitudes for processes involving higher spins in this paper. First we give the explicit expressions of Rarita-Schwinger wave functions and propagators for bosons with spins, then kinematic singularity free 3-leg effective vertexes are derived and given in a list. Equivalence relations are worked out to get these independent vertexes. Constraints of space reflection symmetry and boson symmetry are considered and shown in a explicit way. Some helicity amplitudes for two-body decays in center of frame are calculated. Finally the covariant helicity amplitudes for the process $a_1\to π^+π^+π^-$ are constructed to illustrate how to include background (1PI) amplitudes. Both background amplitudes and resonance amplitudes are needed to give reliable descriptions to high energy reactions.

hep-ph↗
arXiv1998

Comment on the hadronic decay of excited heavy quarkonia

We make comments on ref.[Z.Phys. C73, 541 (1997)], and provide partial wave analysis to the decays of excited heavy S-wave $1^-$ quarkonia into the basic $1^-$ quarkonia state plus $ππ$. It is revealed that there exist contributions of D-wave transition in $ψ'\longrightarrow J/ψππ$, $Υ(2S)\longrightarrow Υ(1S) ππ$ and $Υ(3S)\longrightarrow Υ(1S) ππ$ by using the data-fitting results in ref.[Z.Phys C73, 541 (1997)]. A possible experimental method to measure the D-wave directly is discussed.

hep-ph↗
arXiv1998

$ρ^0-ω$ mixing in U(3)}$_L\times$ U(3)$_R$ chiral theory of mesons

In this paper, U(3)$_L\times$ U(3)$_R$ chiral theory of mesons is extended to the leading order in quark mass expansion in order to evaluate the $ρ^0-ω$ mixing. It is shown that the use of path integral method to integrate out the quark fields naturally leads to the $ρ^0-ω$ mixing vertices, and this mixing is entirely from the quark loop in this theory. The off-shell behaviour of the mixing amplitude is analyzed. The on-shell mixing amplitude is obtained from the decay $ω\to π^+π^-$. Furthermore, the constraints on the light quark mass parameters are extracted from the $ρ^0-ω$ mixing and the mesons masses, and the mass splitting of $K^*(892)$-mesons is predicted.

hep-ph↗
arXiv1998

Chiral Perturbation Theory and U(3)_L\times U(3)_R Chiral Theory of Mesons

We examine low energy limit of $U(3)_L\times U(3)_R$ chiral theory of mesons through integrating out fields of vector and axial-vector mesons. The effective lagrangian for pseudoscalar mesons at $O(p^4)$ has been obtained, and five low energy coupling constants $L_i(i=1,2,3,9,10)$ have been revealed. They are in good agreement with the results of CHPT's at $μ\sim m_ρ$.

hep-ph↗
arXiv1997

Electromagnetic masses of the mesons and the generalization of Dashen's theorem

In the framework of $U(3)_L\times U(3)_R$ chiral field theory, Dashen's theorem is reexamined, and the well-known result of $m_{π^\pm}^2-m_{π^0}^2$ obtained by Das, Guralnik, Mathur, Low, and Young is reproduced. We find that Dashen's theorem, which automatically holds for pseudoscalar mesons in this theory, can be generalized to the sector of axial-vector mesons, however, fails for the sector of vector mesons.

hep-ph↗
arXiv1997

Electromagnetic mass splittings of $π, a_1, K, K_1(1400)$ and $K^*(892)$

To one-loop order and $O(α_{em})$, the electromagnetic mass splittings of $π$, $a_1$, $K$, $K_1(1400)$, and $K^*(892)$ are calculated in the framework of $U(3)_L\times U(3)_R$ chiral field theory. The logarithmic divergences emerging in the Feynman integrations of the mesonic loops are factorized by using an intrinsic parameter $g$ of this theory. No other additional parameters or counterterms are introduced to absorb the mesonic loop divergences. When $f_π$,$m_ρ$ and $m_a$ are taken as inputs, the parameter $g$ will be determined and all the physical results are finite and fixed. Dashen's theorem is satisfied in the chiral SU(3) limit of this theory, and a rather large violation of the theorem is revealed at the order of $m_s$ or $m_K^2$. Mass ratios of light quarks have been determined. A relation for electromagnetic corrections to masses of axial-vector mesons is obtained. It could be regarded as a generalization of Dashen's theorem. Comparing with data, it is found that the non-electromagnetic mass difference of $K^*$ is in agreement with the estimation of Schechter, Subbaraman, Weigel.

hep-ph↗