Wu Shao-Ping

Wave Propagation in Accretion Disks with Self-Gravity

We extend the research by Lubow and Pringle of axisymmetric waves in accretion disks to the case where self-gravity of disks should be considered. We derive and analyse the dispersion relations with the effect of self-gravity. Results show that self-gravity extends the forbidden region of the wave propagation: for high frequency p-modes, self-gravity makes the wavelength shorter and the group velocity larger; for low frequency g-modes, the effect is opposite.

Influences of decoherence on the generation of a macroscopic superposition state using weak cross-Kerr effect

Considering a system in which a single photon and a coherent field propagate through a Kerr medium, when the weak cross-Kerr interaction between the coherent state and the single photon under decoherence is involved, this paper derives analytically a macroscopic superposition state by the superoperator method and investigates the influences of decoherence on the coherence properties of the obtained state. It finds that the macroscopic superposition state will experience evolution from a pure superposition state to a mixed state in a dissipative environment and the Kerr effect makes the field display a periodic revival from decoherence for a short time.

Population Inversion of a V-type Three-Level Atom due to the Effect of Cavity-Induced Quantum Interference

A cavity-modified master equation is derived for a coherently driven V-type three-level atom coupled to a single-mode cavity in the bad cavity limit. The influences of the cavity-induced quantum interference on the steady-state populations are analysed. We show that the population inversion can occur due to the effect of cavity-induced quantum interference. PACS: 42. 50. Dv, 42. 50. Gy

On the pulsational-radial oscillations instability of isothermal magnetized accretion disk with self-gravity

This is the first paper to consider the effects of both magnetic field and self-gravity on the pulsational instability. Our main new results are that the self-gravity enhances the instability of the magneto-acoustic mode in the outer disk strongly, and also affects the instability in the inner disk, but stabilized the viscous mode. The effect of self-gravity is much greater than that of magnetic field in the outer disk, while the effect of magnetic field on the instability is weaker than that in the previous works (Wuet al., 1995; Yanget al., 1995), in which the self-gravity has not been considered. Finally, we discuss our results.

Dynamics of Entanglement for Coherent Motional States of Two Trapped Ions in Cascaded Optical Cavities

We study the generation of an entangled motional coherent state of two distant ions trapped in two cascaded cavities, in which the motional mode of the each ion is coupled to the respective cavity field via a linear-mixing interaction. The master equation is solved analytically by using the characteristic function method. It is found that the generated entangled coherent state resulted from the initial preparation of an even coherent state is more robust than that from an odd coherent state under the dissipation of the cavity.

Influence of the pulsar parameters on γ-ray burst afterglows☆

Abstract By applying the fireball model of γ-ray burst with a central pulsar, the radiation fluxes of the afterglows of two γ-ray bursts, GRB970228 and GRB000301c, are calculated. The results of the calculation agree very well with the observations. The differing characters of the light curves with a “break” in the optical waveband R of the afterglows of two bursts are interpreted, in terms of differing pulsar parameter values.

Axisymmetric Waves in Isothermal Accretion Discs with Vertical Self-Gravity*

We extend the research of axisymmetric waves in accretion discs with three-dimensional structure to the case that vertical self-gravity of the discs is included. We derive and analyze the dispersion relation and solve the eigenfunctions numerically. The following results have been reached: vertical self-gravity expands the forbidden region of the wave propagation. As the influence of the vertical self-gravity increases, the group velocities of the waves get smaller and the vertical nodes of the wave shrink to the middle plane of the disc.

The radial-azimuthal instability of an isothermal magnetized accretion disk

The radial-azimuthal instability of an isothermal magnetized accretion disk is examined in this paper. We find that the azimuthal perturbation enhances the instability of the magneto-acoustic and non-axisymmetric modes. The magnetic field induces and enhances the instability of magneto-acoustic modes, but stabilizes the non-axisymmetric modes in the outer disk. The viscous modes are always stable. The instability of magneto-acoustic modes are dominant in this disk.

The effects of magnetic field and viscosity on the pulsational instability of thin isothermal accretion disks

Abstract Using MHD perturbation, we derive the dispersion equation for pulsational instability of thin isothermal accretion disks. The effects of magnetic field, radial viscous force and the causality-modified α-viscosity are examined. We find that magnetic field is a global destabilizing factor acting on the viscous mode and the two acoustic modes. Radial viscous force is a global stabilizing factor for the two acoustic modes. The causality-modified α-viscosity acts mainly in the inner disk: it is a stabilizing factor for the viscous mode and I-mode when there is no magnetic field, and is a destabilizing factor for the two acoustic modes when there is a magnetic field.