arXiv subjects
Publications and source records attributed to Jian-Ge Zhou.
The spacetime superalgebra via the supermembrane probe in the background of AdS_4 \times S^7 is discussed to the lowest order in the spinor coordinate $\t$. To obtain the correct spacetime superalgebras, all $\t^2$ order corrections for supervielbein and super 3-form gauge potential have to be included. The central extension of the superalgebra OSp(8|4) of the super isometries for AdS_4 \times S^7 is found.
The greybody factors for spin 1/2 particles in the BTZ black holes are discussed from 2D CFT in bulk-boundary correspondence. It is found that the initial state of spin 1/2 particle in the BTZ black holes can be described by the Poincaré vacuum state in boundary 2D CFT, and the nonlinear coordinate transformation causes the thermalization of the Poincaré vacuum state. For special case, our results for the greybody factors agree with the semiclassical calculation.
The greybody factors in BTZ black holes are evaluated from 2D CFT in the spirit of AdS$_3$/CFT correspondence. The initial state of black holes in the usual calculation of greybody factors by effective CFT is described as Poincaré vacuum state in 2D CFT. The normalization factor which cannot be fixed in the effective CFT without appealing to string theory is shown to be determined by the normalized bulk-to-boundary Green function. The relation among the greybody factors in different dimensional black holes is exhibited. Two kinds of $(h,{\bar h})=(1,1)$ operators which couple with the boundary value of massless scalar field are discussed.
We study the creation of a fundamental string between D4-branes at angles in string theory. It is shown that $R(-1)^{F}$ part of the one-loop potential of open string changes its sign due to the change of fermionic zero-mode vacua when the branes cross each other. As a result the effective potential is independent of the angles when supersymmetry is partially unbroken, and leads to a consistent picture that a fundamental string is created in the process. We also discuss the s-rule in the configuration. The same result is obtained from the one-loop potential for the orthogonal D4-branes with non-zero field strength. The result is also confirmed from the tension obtained by deforming the Chern-Simons term on one D4-brane, which is induced by another tilted D4-brane.
The partition function in Matrix theory is constructed by Euclidean path integral method. The D0-branes, which move around in the finite region with a typical size of Schwarzschild radius, are chosen as the background. The mass and entropy of the system obtained from the partition function contain the parameters of the background. After averaging the mass and entropy over the parameters, we find that they match the properties of 11D Schwarzschild black holes. The period $\b$ of Euclidean time can be identified with the reciprocal of the boosted Hawking temperature. The entropy $S$ is shown to be proportional to the number $N$ of Matrix theory partons, which is a consequence of the D0-brane background.
The potential between two D4-branes at angles with partially unbroken supersymmetry is computed, and is used to discuss the creation of a fundamental string when two such D4-branes cross each other in M(atrix) theory. The effective Lagrangian is shown to be anomalous at 1-loop approximation, but it can be modified by bare Chern-Simons terms to preserve the invariance under the large gauge transformation. The resulting effective potential agrees with that obtained from the string calculations. The result shows that a fundamental string is created in order to cancel the repulsive force between two D4-branes at proper angles.
A formula suitable for a quantitative evaluation of the tunneling effect in a ferromagnetic particle is derived with the help of the instanton method. The tunneling between n-th degenerate states of neighboring wells is dominated by a periodic pseudoparticle configuration. The low-lying level-splitting previously obtained with the LSZ method in field theory in which the tunneling is viewed as the transition of n bosons induced by the usual (vacuum) instanton is recovered. The observation made with our new result is that the tunneling effect increases at excited states. The results should be useful in analyzing results of experimental tests of macroscopic quantum coherence in ferromagnetic particles.
An explicit solution in super Yang-Mills theory, which after T-duality describes two sets of D4-branes at angles, is constructed. The gauge configuration possesses 3/16 unbroken supersymmetry for the equal magnitudes of field strengths, and can be considered as the counterpart of the solution of D=11 supergravity with the same amount of supersymmetry in the solutions given by Gauntlett et al. The energy of the Born-Infeld action of the gauge configuration gives further evidence for the geometrical interpretation as two sets of D4-branes at angles. The energy of super Yang-Mills theory is shown to coincide with that of M(atrix) theory. This fact shows that the configuration with 3/16 supersymmetry can be realized in M(atrix) theory, which describes two sets of longitudinal M5-branes (with common string direction) at angles.
We present a systematic analysis of possible bound states of M-brane solutions (including waves and monopoles) by using the solution generating technique of reduction of M-brane to 10 dimensions, use of T-duality and then lifting back to 11 dimensions. We summarize a list of bound states for one- and two-charge cases including tilted brane solutions. Construction rules for these non-marginal solutions are also discussed.
The tunneling effect of a periodic potential with an asymmetric twin barrier per period is calculated using the instanton method. The model is derived from the Hamiltonian of a small ferromagnetic particle in an external magnetic field using the spin-coherent-state path integral. The instantons in two neighbouring barriers differ and lead to different level shifts $\triangleε_1, \triangleε_2$. We derive with Bloch theory the energy spectrum which has formally the structure of an energy band. The spectrum depends on both level shifts. The removal of Kramer's degeneracy by an external magnetic field is discussed. In addition we find a new kind of quenching of macroscopic quantum coherence which is irrelevant to Kramer's degeneracy.
Starting from the coherent state representation of the evolution operator with the help of the path-integral, we derive a formula for the low-lying levels $E = ε_0 - 2\triangleεcos (s+ξ)π$ of a quantum spin system. The quenching of macroscopic quantum coherence is understood as the vanishing of $cos (s+ξ)π$ in disagreement with the suppression of tunneling (i.e. $\triangleε= 0$) as claimed in the literature. A new configuration called the macroscopic Fermi-particle is suggested by the character of its wave function. The tunneling rate ($(2\triangleε)/(π)$) does not vanish, not for integer spin s nor for a half-integer value of s, and is calculated explicitly (for the position dependent mass) up to the one-loop approximation.
An M-brane and anti-M-brane scheme is proposed to study nonextremal 4D and 5D black holes. The improved nonextremal intersecting M-brane solutions proposed here, involve two sets of harmonic functions. The constraints among the pressures are found, and new features in the M-brane and anti-M-brane picture are demonstrated, which resolve the discrepancy in the number of free parameters in the D-brane picture. In terms of the ``numbers'' of M-branes and anti-M-branes, the prefactors of the entropies are found to be model independent, and the Bekenstein-Hawking entropy assumes the duality invariant form which is consistent with the microscopic explanation of the black hole entropy.
The RST model is augmented by the addition of a scalar field and a boundary term so that it is well-posed and local. Expressing the RST action in terms of the ADM formulation, the constraint structure can be analysed completely. It is shown that from the view point of local field theories, there exists a hidden dynamical field in the RST model. Thanks to the presence of this hidden dynamical field, we can reconstruct the closed algebra of the constraints which guarantee the general invariance of the RST action. The resulting stress tensors are recovered to be true tensor quantities. At the quantum level, the cancellation condition for the total central charge is reexamined. Finally, with the help of the hidden dynamical field, the fact that the semi-classical static solution of the RST model has two independent parameters (P,M), whereas for the classical CGHS model there is only one, can be explained.
A new approach with BRST invariance is suggested to cure the degeneracy problem of ill defined path integrals in the path-integral calculationof quantum mechanical tunneling effects in which the problem arises due to the occurrence of zero modes. The Faddeev-Popov procedure is avoided and the integral over the zero mode is transformed in a systematic way into a well defined integral over instanton positions. No special procedure has to be adopted as in the Faddeev-Popov method in calculating the Jacobian of the transformation. The quantum mechanical tunneling for the Sine-Gordon potential is used as a test of the method and the width of the lowest energy band is obtained in exact agreement with that of WKB calculations.
The ADM and Bondi mass for the RST model have been first discussed from Hawking and Horowitz's argument. Expressing the localized RST action in terms of the ADM formulation, the RST Hamiltonian can be derived, meanwhile keeping track of all boundary terms. Then the total boundary terms can be taken as the total energy for the RST model. It has been found that there is a new contribution to the ADM and Bondi mass from the RST boundary due to the existence of the hidden dynamical field. The ADM and Bondi mass have been discussed respectively in detail, and some new properties have been found.