摘要:
We discuss a model of weakly magnetized, isothermal accretion disk with diffusion-type viscosity. On the basis of our previous work, we investigate the pulsational instability for non-axisymmetric perturbations of the disk (including perturbations in all three directions, radial, azimuthal and vertical). It is shown that radial perturbation is essential: in the absence of radial perturbation, there can be no instability for azimuthal and vertical perturbations; in the presence of radial perturbation, instability for the purely radial perturbation, as well as axisymmetric and non-axisymmetric instabilities arising from the coupling between the radial perturbation on one hand, and the vertical and azimuthal perturbations, respectively, on the other, are all possible. When perturbations in all three directions coexist, the corresponding non-axisymmetric instability is also possible.
关键词:
finite-size scaling;phi(4) field theory;universality
摘要:
Previous theories have predicted that O(n) symmetric systems in a finite cubic geometry with periodic boundary conditions have universal finite-size scaling functions near criticality in d>4 dimensions. On the basis of exact results for the O(n) symmetric phi(4) model in the large n limit we show that universal finite-size scaling does not hold in the predicted form because of significant cut-off and lattice effects for d>4. It is shown that finite-size scaling is valid with two reference lengths which turn out to be identical with the amplitudes of the bulk correlation length. For the phi(4) field theory the finite-size scaling functions are shown to be non-universal, i.e., to depend explicitly on the cut-off and on the bare four-point coupling constant, whereas for a phi(4) lattice model the finite-size scaling functions have a different form that is independent of the lattice spacing and the four-point coupling constant. (C) 1998 Elsevier Science B.V. All rights reserved.
作者机构:
[刘延申; 祝家清] Central China Normal Univ, Wuhan, China
通讯机构:
Central China Normal Univ, China
关键词:
自由电子激光器;能量转换效率
摘要:
According to the Weizsacker-Williams approximation, the energy conversion between the scattered photon and pseudophoton is studied and the relation is obtained. The enhancement of the energy of the scattered photon is achieved at the cost of consuming of electron energy. The scale and efficiency of energy conversion are calculated. The energy conversion efficiency in the free-electron laser is up to 50%.
作者机构:
[Li, JR; Zheng, XP] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构:
[Zheng, XP] H;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
关键词:
Fluctuation;Kinetic theory;QGP;Weak turbulent theory
摘要:
We calculate the energy changes of a colored particle and a color dipole passing through a quark-gluon plasma (QGP) taking into account the non-linear color dielectric coefficient and find the partons may have an increase of energy determined by fluctuating or turbulent intensity unlike the result in a linear approximation. We also show the acceleration effect is due to energy transfer into the partons from fluctuating fields. (C) 1998 Elsevier Science B.V.
作者机构:
[Hu, XM; Peng, JS] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构:
[Hu, XM] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
In this paper we investigate the effect of two incoherent steps on the statistical properties of cascade lasers without and with inversion. It is demonstrated that the noise in the intensity difference may be reduced 50% below the shot noise. A simple physical explanation of the mechanism for squeezing is given.
作者机构:
[Hu, XM; Peng, JS] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构:
[Hu, XM] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
The effects of the pump phase noise on the linewidth of the Xi-laser without inversion are studied. Although the finite pump phase noise is added to the spontaneous emission noise, the linewidth of the Xi-laser without inversion can be reduced. Physically this is interpreted as the enhancement of the atomic-coherence-induced noise correlation via the pump phase noise.