979 research outputs found
The polarization tensor of neutral gluons in external fields at high temperature
The one-loop polarization operator of neutral gluons in the background
constant Abelian isotopic, , and hypercharge, , chromomagnetic
fields combined with electrostatic potential at high temperature is
calculated. The case when is investigated separately. The proper time
method is applied. It is found that neutral gluons do not acquire magnetic
masses in the background fields, in contrast to the charged ones. The
application of the results are discussed.Comment: 13 pages, 1 figur
The pressure of deconfined QCD for all temperatures and quark chemical potentials
We present a new method for the evaluation of the perturbative expansion of
the QCD pressure which is valid at all values of the temperature and quark
chemical potentials in the deconfined phase and which we work out up to and
including order g^4 accuracy. Our calculation is manifestly four-dimensional
and purely diagrammatic -- and thus independent of any effective theory
descriptions of high temperature or high density QCD. In various limits, we
recover the known results of dimensional reduction and the HDL and HTL
resummation schemes, as well as the equation of state of zero-temperature quark
matter, thereby verifying their respective validity. To demonstrate the overlap
of the various regimes, we furthermore show how the predictions of dimensional
reduction and HDL resummed perturbation theory agree in the regime
T~\sqrt{g}*mu. At parametrically smaller temperatures T~g*mu, we find that the
dimensional reduction result agrees well with those of the nonstatic
resummations down to the remarkably low value T~0.2 m_D, where m_D is the Debye
mass at T=0. Beyond this, we see that only the latter methods connect smoothly
to the T=0 result of Freedman and McLerran, to which the leading small-T
corrections are given by the so-called non-Fermi-liquid terms, first obtained
through HDL resummations. Finally, we outline the extension of our method to
the next order, where it would include terms for the low-temperature entropy
and specific heats that are unknown at present.Comment: 45 pages, 21 figures; v2: minor corrections and clarifications,
references added; v3: Fig 16 added, version accepted for publication in PR
Can the scale factor be rippled?
We address an issue: would the cosmological scale factor be a locally
oscillating quantity? This problem is examined in the framework of two
classical 1+1-dimensional models: the first one is a string against a curved
background, and the second one is an inhomogeneous Bianchi I model. For the
string model, it is shown that there exist the gauge and the initial condition
providing an oscillation of scale factor against a slowly evolving background,
which is not affected by such an oscillation "at the mean". For the
inhomogeneous Bianchi I model with the conformal time gauge, an initially
homogeneous scale factor can become inhomogeneous and undergo the nonlinear
oscillations. As is shown these nonlinear oscillations can be treated as a
nonlinear gauge wave.Comment: 10 pages, 5 figure
Solution of the discrete Wheeler-DeWitt equation in the vicinity of small scale factors and quantum mechanics in the space of negative constant curvature
The asymptotic of the solution of the discrete Wheeler-DeWitt equation is
found in the vicinity of small scale factors. It is shown that this problem is
equivalent to the solution of the stationary Schr\"{o}dinger equation in the
(super) space of negative constant curvature. The minimum positive eigenvalue
is found from which a continuous spectrum begins.Comment: 8 page
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