25,965 research outputs found
Probing Fuzzballs with Particles, Waves and Strings
We probe D1D5 micro-state geometries with massless particles, waves and
strings. To this end, we study geodetic motion, Klein-Gordon equation and
string scattering in the resulting gravitational background. Due to the reduced
rotational symmetry, even in the simple case of a circular fuzzball, the system
cannot be integrated elementarily. Yet, for motion in the plane of the string
profile or in the orthogonal plane to it, one can compute the deflection angle
or the phase shift and identify the critical impact parameter, at which even a
massless probe is captured by the fuzzball if its internal momentum is properly
tuned. We find agreement among the three approaches, thus giving further
support to the fuzzball proposal at the dynamical level.Comment: 35 pages. Extended and improved discussions on the integrability of
the geodetic equations and on the critical impact parameter
EEMCS final report for the causal modeling for air transport safety (CATS) project
This document reports on the work realized by the DIAM in relation to the completion of the CATS model as presented in Figure 1.6 and tries to explain some of the steps taken for its completion. The project spans over a period of time of three years. Intermediate reports have been presented throughout the projectâs progress. These are presented in Appendix 1. In this report the continuousâdiscrete distributionâfree BBNs are briefly discussed. The human reliability models developed for dealing with dependence in the model variables are described and the software application UniNet is presente
Equation of state of metallic hydrogen from Coupled Electron-Ion Monte Carlo simulations
We present a study of hydrogen at pressures higher than molecular
dissociation using the Coupled Electron-Ion Monte Carlo method. These
calculations use the accurate Reptation Quantum Monte Carlo method to estimate
the electronic energy and pressure while doing a Monte Carlo simulation of the
protons. In addition to presenting simulation results for the equation of state
over a large region of phase space, we report the free energy obtained by
thermodynamic integration. We find very good agreement with DFT calculations
for pressures beyond 600 GPa and densities above . Both
thermodynamic as well as structural properties are accurately reproduced by DFT
calculations. This agreement gives a strong support to the different
approximations employed in DFT, specifically the approximate
exchange-correlation potential and the use of pseudopotentials for the range of
densities considered. We find disagreement with chemical models, which suggests
a reinvestigation of planetary models, previously constructed using the
Saumon-Chabrier-Van Horn equations of state.Comment: 9 pages, 7 figure
Solving the kilo-second QPO problem of the intermediate polar GK Persei
We detect the likely optical counterpart to previously reported X-ray QPOs in
spectrophotometry of the intermediate polar GK Persei during the 1996 dwarf
nova outburst. The characteristic timescales range between 4000--6000 s.
Although the QPOs are an order of magnitude longer than those detected in the
other dwarf novae we show that a new QPO model is not required to explain the
long timescale observed. We demonstrate that the observations are consistent
with oscillations being the result of normal-timescale QPOs beating with the
spin period of the white dwarf. We determine the spectral class of the
companion to be consistent with its quiescent classification and find no
significant evidence for irradiation over its inner face. We detect the white
dwarf spin period in line fluxes, V/R ratios and Doppler-broadened emission
profiles.Comment: 14 pages, 11 figures. Accepted for publication in MNRA
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