39 research outputs found
Interaction effects and phase relaxation in disordered systems
This paper is intended to demonstrate that there is no need to revise the
existing theory of the transport properties of disordered conductors in the
so-called weak localization regime. In particular, we demonstrate explicitly
that recent attempts to justify theoretically that the dephasing rate
(extracted from the magnetoresistance) remains finite at zero temperature are
based on the profoundly incorrect calculation. This demonstration is based on a
straightforward evaluation of the effect of the electron-electron interaction
on the weak localization correction to the conductivity of disordered metals.
Using well-controlled perturbation theory with the inverse conductance as
the small parameter, we show that this effect consists of two contributions.
First contribution comes from the processes with energy transfer smaller than
the temperature. This contribution is responsible for setting the energy scale
for the magnetoresistance. The second contribution originates from the virtual
processes with energy transfer larger than the temperature. It is shown that
the latter processes have nothing to do with the dephasing, but rather manifest
the second order (in ) correction to the conductance. This correction is
calculated for the first time. The paper also contains a brief review of the
existing experiments on the dephasing of electrons in disordered conductors and
an extended qualitative discussion of the quantum corrections to the
conductivity and to the density of electronic states in the weak localization
regime.Comment: 34 pages, 13 .eps figure
The photometric and spectral investigation of CI Camelopardalis, an X-ray transient and B[e] star
We combined the results of UBVR photometry of CI Cam taken at Sternberg
Astronomical Institute in 1998--2001, and moderate resolution spectroscopy
taken at Special Astrophysical Observatory during the same time period.
Photometry as well as fluxes of Balmer emissions and of some Fe II emission
lines of CI Cam in quiet state reveal a cyclic variation with the period of
. The variation like this may be due to an orbital motion in a
wide pair with a giant star companion that exhibits the reflection effect on
its side faced to a compact companion.
The V-band photometry also confirms the pre-outburst 11.7 day period found by
Miroshnichenko earlier, but with a lower amplitude of 3 per cent. The
possibility of identity of this photometric period with the period of jet's
rotation in the VLA radio map of the object CI Cam was investigated. The radio
map modelling reveals the inclination of the jet rotation axis to the line of
sight, , the angle between the rotation axis and the direction of
ejection of the jet, , and jet's spatial velocity of
0.23--0.26c.
Equivalent widths and fluxes of various spectral lines show different
amplitudes of changes during the outburst, and essentially distinct behaviour
in quiescence. Five types of such behaviour were revealed, that indicates the
strong stratification of a gas and dust envelope round the system . The time
lag of strengthening of 50--250 in the forbidden line of nitrogen [N II]
was found relatively to the X-ray outburst maximum.Comment: 15 pages, 8 figures, 3 tables, Astron. Zh., 2002, (in press), vol.79,
number