47,817 research outputs found
Hawking temperature from scattering off the charged 2D black hole
The charged 2D black hole is visualized as presenting an potential barrier
to on-coming tachyon wave. Since this takes the complicated
form, an approximate form is used for scattering analysis. We
calculate the reflection and transmission coefficients for scattering of
tachyon off the charged 2D black hole. The Hawking temperature is also derived
from the reflection coefficient by Bogoliubov transformation. In the limit of
, we recover the Hawking temperature of the 2D dilaton black hole.Comment: 12 pages 3 figures, RevTeX, to obtain figures contact author
([email protected]
Propagating waves in an extremal black string
We investigate the black string in the context of the string theories. It is
shown that the graviton is the only propagating mode in the (2+1)--dimensional
extremal black string background. Both the dilation and axion turn out to be
non-propagating modes.Comment: Minor corrections, 11 pages in ReVTeX, no figure
The vibrational dynamics of vitreous silica: Classical force fields vs. first-principles
We compare the vibrational properties of model SiO_2 glasses generated by
molecular-dynamics simulations using the effective force field of van Beest et
al. (BKS) with those obtained when the BKS structure is relaxed using an ab
initio calculation in the framework of the density functional theory. We find
that this relaxation significantly improves the agreement of the density of
states with the experimental result. For frequencies between 14 and 26 THz the
nature of the vibrational modes as determined from the BKS model is very
different from the one from the ab initio calculation, showing that the
interpretation of the vibrational spectra in terms of calculations using
effective potentials can be very misleading.Comment: 7 pages of Latex, 4 figure
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