Browsing by Author "Ng, KW"

Now showing 1 - 3 of 3

Neutrino-photon scattering and its crossed processes in a background magnetic field
(1999-11-04)
Chyi, TK
;
Hwang, CW
;
Kao, WF
;
Lin, GL
;
Ng, KW
We study the neutrino-photon processes such as gamma gamma --> , v gamma --> v gamma, and --> gamma gamma in a background magnetic field smaller than the critical magnetic field Bc + m(e)(2)/e. Using Schwinger's formalism, we extract leading magnetic-field contributions to the above processes. Our result is valid throughout the kinematic regime where both neutrino and photon energies are significantly smaller than m(w). We briefly discuss the astrophysical implications of our result. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
One-loop Vilkovisky-DeWitt effective potential for scale-invariant gravity
(1999-06-01)
Lin, SY
;
Ng, KW
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
For a pure gravity theory without matter, the scale symmetric phase represents an equivalent class of gravity theories, to which the Einstein gravity plus a cosmological constant belongs under a special gauge choice. The one-loop quantum correction of this scale-invariant theory is calculated by using Vilkovisky-DeWitt's method. It is shown that the resulting effective potential is gauge-independent as expected. Some discussions of the Vilkovisky-DeWitt method through this calculation are given.
Weak-field expansion for processes in a homogeneous background magnetic field
(2000-11-15)
Chyi, TK
;
Hwang, CW
;
Kao, WF
;
Lin, GL
;
Ng, KW
The weak-field expansion of the charged fermion propagator under a uniform magnetic field is studied. Starting from Schwinger's proper-time representation, we express the charged fermion propagator as an infinite series corresponding to different Landau levels. This infinite series is then reorganized according to the powers of the external field strength B. For illustration, we apply this expansion to gamma --> nu<()over bar> and nu --> nu gamma decays, which involve charged fermions in the internal loop. The leading and subleading magnetic-field effects to the above processes are computed.