24,279 research outputs found
Quantum inequalities for massless spin-3/2 field in Minkowski spacetime
Quantum inequalities have been established for various quantum fields in both
flat and curved spacetimes. In particular, for spin-3/2 fields, Yu and Wu have
explicitly derived quantum inequalities for massive case. Employing the similar
method developed by Fewster and colleagues, this paper provides an explicit
formula of quantum inequalities for massless spin-3/2 field in four-dimensional
Minkowski spacetime.Comment: revtex4, 6 pages, accepted to be published in PRD, minor corrections,
typos correcte
Tunnelling Effect and Hawking Radiation from a Vaidya Black Hole
In this paper, we extend Parikh' work to the non-stationary black hole. As an
example of the non-stationary black hole, we study the tunnelling effect and
Hawking radiation from a Vaidya black hole whose Bondi mass is identical to its
mass parameter. We view Hawking radiation as a tunnelling process across the
event horizon and calculate the tunnelling probability. We find that the result
is different from Parikh's work because is the function of
Bondi mass m(v)
Density oscillations in trapped dipolar condensates
We investigated the ground state wave function and free expansion of a
trapped dipolar condensate. We find that dipolar interaction may induce both
biconcave and dumbbell density profiles in, respectively, the pancake- and
cigar-shaped traps. On the parameter plane of the interaction strengths, the
density oscillation occurs only when the interaction parameters fall into
certain isolated areas. The relation between the positions of these areas and
the trap geometry is explored. By studying the free expansion of the condensate
with density oscillation, we show that the density oscillation is detectable
from the time-of-flight image.Comment: 7 pages, 9 figure
Statistics of lower tropospheric inversions over the continental United States
The basic structure parameters of lower tropospheric
inversions (LTIs) have been derived from 10 years (1998–2007) of high vertical
resolution (~50 m) radiosonde observations over 56 United States
stations. Seasonal and longitudinal variability of these parameters are
presented and the formation mechanisms of LTI are also discussed. It is
found that LTI seems to be a common feature over the continental United
States. The LTI occurrence rates (defined as the fraction of measurements
with LTI, which is calculated from the number of LTI cases divided by the
number of measurements of the whole 10 years) at these 56 stations vary from
3.7% to 14.5%; the averaged base heights of LTI have a range of 3–5 km
above mean sea level (a.m.s.l.); the averaged thicknesses and temperature jump
ranges from 420–465 m and 1.9–2.2 K, respectively. These parameters have an
obvious seasonal variation. In winter, all the occurrence rates, thicknesses
and temperature jumps of LTI have much larger values than those in summer.
LTI occurrence rate shows an obvious west-east increasing trend in all 4
seasons. Detailed analyses reveal that dynamical instability induced by
strong zonal wind shear is responsible for LTI in winter, spring and autumn;
the frontal system tends to generate LTI in summer. Since the higher
occurrence rate, larger temperature jump and larger thickness of LTI occur
in winter, we believe strong zonal wind shear plays a more important role in
the formation of LTI
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