16,901 research outputs found
Dynamical Casimir effect in a periodically changing domain: A dynamical systems approach
We study the problem of the behavior of a quantum massless scalar field in
the space between two parallel infinite perfectly conducting plates, one of
them stationary, the other moving periodically. We reformulate the physical
problem into a problem about the asymptotic behavior of the iterates of a map
of the circle, and then apply results from theory of dynamical systems to study
the properties of the map. Many of the general mathematical properties of maps
of the circle translate into properties of the field in the cavity. For
example, we give a complete classification of the possible resonances in the
system, and show that small enough perturbations do not destroy the resonances.
We use some mathematical identities to give transparent physical interpretation
of the processes of creation and amplification of the quantum field due to the
motion of the boundary and to elucidate the similarities and the differences
between the classical and quantum fields in domains with moving boundaries.Comment: 19 pages, 7 figure
Free energy of a static quark anti-quark pair and the renormalized Polyakov loop in three flavor QCD
We study the free energy of a static quark anti-quark pair at finite
temperature in three flavor QCD with degenerate quark masses using N_tau=4 and
6 lattices with Asqtad staggered fermion action. The static free energy was
calculated for different values of the quark mass and the entropy contribution
at large distances has been extracted. We also calculate the renormalized
Polyakov loop following the approach by Kaczmarek et al.Comment: RevTeX, 7 pages, 8 figures; Minor corrections, added referenc
On Charmonia Survival Above Deconfinement
We study charmonium correlators and spectral functions at zero and finite
temperature using anisotropic lattices at several different lattice spacings.
We find evidence for survival of 1S charmonia states at leas till and
dissolution of 1P states at .Comment: contribution to the 29th Johns Hopkins Workshop in Theoretical
Physics, Budapest, Hungary, 1-3 August 200
Periodic variations in the colours of the classical T Tauri star RW Aur A
The classical T Tauri star RW Aur A is an irregular variable with a large
amplitude in all photometric bands. In an extended series of photometric data
we found small-amplitude periodic variations in the blue colours of the star,
with a period of 2.64 days. The period was relatively stable over several
years. The amplitude of the periodic signal is 0.21 mag in U-V, 0.07 mag in
B-V, and about 0.02 mag in V-R and V-I. No periodicity was found in the V
magnitude. The relevance of this photometric period to the recently discovered
periodicity in spectral features of the star is discussed, and the hypothesis
of a hot spot is critically considered.Comment: 5 pages, 8 figures, uses new aa.cls, accepted for publication in
Astronomy and Astrophysic
Simulation of the Gravitational Collapse and Fragmentation of Rotating Molecular Clouds
In this paper we study the process of the subsequent (runaway) fragmentation
of the rotating isothermal Giant Molecular Cloud (GMC) complex. Our own
developed Smoothed Particle Hydrodynamics (SPH) gas-dynamical model
successfully reproduce the observed Cloud Mass-distribution Function (CMF) in
our Galaxy (even the differences between the inner and outer parts of our
Galaxy). The steady state CMF is established during the collapse within a
free-fall timescale of the GMC. We show that one of the key parameters, which
defines the observed slope of the present day CMF, is the initial ratio of the
rotational (turbulent) and gravitational energy inside the fragmented GMC.Comment: 8 pages, 9 EPS figures, special forma.cls class file is use
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