8,007 research outputs found
Inhomogeneous Cooling of the Rough Granular Gas in Two Dimensions
We study the inhomogeneous clustered regime of a freely cooling granular gas
of rough particles in two dimensions using large-scale event driven simulations
and scaling arguments. During collisions, rough particles dissipate energy in
both the normal and tangential directions of collision. In the inhomogeneous
regime, translational kinetic energy and the rotational energy decay with time
as power-laws and . We numerically determine
and , independent of the
coefficients of restitution. The inhomogeneous regime of the granular gas has
been argued to be describable by the ballistic aggregation problem, where
particles coalesce on contact. Using scaling arguments, we predict
and for ballistic aggregation, being different from
that obtained for the rough granular gas. Simulations of ballistic aggregation
with rotational degrees of freedom are consistent with these exponents.Comment: 6 pages, 5 figure
Dynamic Density Response of Trapped Interacting Quantum Gases
An expression for the dynamic density response function has been obtained for
an interacting quantum gas in Random Phase Approximation (RPA) including first
order self and exchange contribution. It involves the single particle wave
functions and eigen values. The expression simplifies when diagonal elements
are considered. The diagonal elements of the imaginary part of Fourier
transformed response function is relevant in the measurement of Bragg
scattering cross-section and in several other applications.Comment: 2 pages, 0 figure, conferenc
Dynamics of Uniform Quantum Gases, I: Density and Current Correlations
A unified approach valid for any wavenumber, frequency, and temperature is
presented for uniform ideal quantum gases allowing for a comprehensive study of
number density and particle-current density response functions. Exact
analytical expressions are obtained for spectral functions in terms of
polylogarithms. Also, particle-number and particle-current static
susceptibilities are presented which, for fugacity less than unity,
additionally involve Kummer functions. The wavenumber and temperature dependent
transverse-current static susceptibility is used to show explicitly that
current correlations are of a long range in a Bose-condensed uniform ideal gas
but for bosons above the critical temperature and for Fermi and Boltzmann gases
at all temperatures these correlations are of short range. Contact repulsive
interactions for systems of neutral quantum particles are considered within the
random-phase approximation. The expressions for particle-number and
transverse-current susceptibilities are utilized to discuss the existence or
nonexistence of superfluidity in the systems under consideration
Accuracy of urinary human papillomavirus testing for presence of cervical HPV: systematic review and meta-analysis
This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 3.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/3.0/.Funding: This study did not receive any fundin
URINARY TESTING FOR HPV Authors' reply to Vorsters and colleagues
This is the peer reviewed published version of the following article: URINARY TESTING FOR HPV Authors' reply to Vorsters and colleagues, which has been published in final form at 10.1136/bmj.g6253. This article may be used for non-commercial purposes in accordance with BMJ's Terms and Conditions for Self-Archiving.
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Density excitations of a harmonically trapped ideal gas
The dynamic structure factor of a harmonically trapped Bose gas has been
calculated well above the Bose-Einstein condensation temperature by treating
the gas cloud as a canonical ensemble of noninteracting classical particles.
The static structure factor is found to vanish as wavenumber squared in the
long-wavelength limit. We also incorporate a relaxation mechanism
phenomenologically by including a stochastic friction force to study the
dynamic structure factor. A significant temperature dependence of the
density-fluctuation spectra is found. The Debye-Waller factor has been
calculated for the trapped thermal cloud as function of wavenumber and of
particle number. A substantial difference is found between clouds of small and
large particle number
Exactly solvable -symmetric models in two dimensions
Non-hermitian, -symmetric Hamiltonians, experimentally realized
in optical systems, accurately model the properties of open, bosonic systems
with balanced, spatially separated gain and loss. We present a family of
exactly solvable, two-dimensional, potentials for a
non-relativistic particle confined in a circular geometry. We show that the
symmetry threshold can be tuned by introducing a second
gain-loss potential or its hermitian counterpart. Our results explicitly
demonstrate that breaking in two dimensions has a rich phase
diagram, with multiple re-entrant symmetric phases.Comment: 6 pages, 6 figure
Dependence of structure factor and correlation energy on the width of electron wires
The structure factor and correlation energy of a quantum wire of thickness
are studied in random phase approximation and for the less
investigated region . Using the single-loop approximation, analytical
expressions of the structure factor have been obtained. The exact expressions
for the exchange energy are also derived for a cylindrical and harmonic wire.
The correlation energy is found to be represented by , for small
and high densities. For a pragmatic width of the wire, the correlation energy
is in agreement with the quantum Monte Carlo simulation data.Comment: Being slightly modifie
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