42,863 research outputs found
Linear and Non Linear Effects on the Newtonian Gravitational Constant as deduced from the Torsion Balance
The Newtonian gravitational constant has still 150 parts per million of
uncertainty. This paper examines the linear and nonlinear equations governing
the rotational dynamics of the torsion gravitational balance. A nonlinear
effect modifying the oscillation period of the torsion gravitational balance is
carefully explored.Comment: 11 pages, 2 figure
Bound States and Critical Behavior of the Yukawa Potential
We investigate the bound states of the Yukawa potential , using different algorithms: solving the Schr\"odinger
equation numerically and our Monte Carlo Hamiltonian approach. There is a
critical , above which no bound state exists. We study the
relation between and for various angular momentum quantum
number , and find in atomic units, , with , ,
, and .Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in
China
On Black Hole Stability in Critical Gravities
We consider extended cosmological gravities with Ricci tensor and scalar
squared terms in diverse dimensions. These theories admit solutions of Einstein
metrics, including the Schwarzschild-Tangherlini AdS black holes, whose mass
and entropy vanish at the critical point. We perform linearized analysis around
the black holes and show that in general the spectrum consists of the usual
spin-2 massless and ghost massive modes. We demonstrate that there is no
exponentially-growing tachyon mode in the black holes. At the critical point,
the massless spin-2 modes have zero energy whilst the massive spin-2 modes are
replaced by the log modes. There always exist certain linear combination of
massless and log modes that has negative energy. Thus the stability of the
black holes requires that the log modes to be truncated out by the boundary
condition.Comment: 16 pages, minor corrections, further comments and references adde
Theoretical modeling of spatial and temperature dependent exciton energy in coupled quantum wells
Motivated by a recent experiment of spatial and temperature dependent average
exciton energy distribution in coupled quantum wells [S. Yang \textit{et al.},
Phys. Rev. B \textbf{75}, 033311 (2007)], we investigate the nature of the
interactions in indirect excitons. Based on the uncertainty principle, along
with a temperature and energy dependent distribution which includes both
population and recombination effects, we show that the interplay between an
attractive two-body interaction and a repulsive three-body interaction can lead
to a natural and good account for the nonmonotonic temperature dependence of
the average exciton energy. Moreover, exciton energy maxima are shown to locate
at the brightest regions, in agreement with the recent experiments. Our results
provide an alternative way for understanding the underlying physics of the
exciton dynamics in coupled quantum wells.Comment: 8 pages, 5 figure
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