6,175 research outputs found
Compact objects in conformal nonlinear electrodynamics
In this paper we consider a special case of vacuum non-linear electrodynamics
with a stress-energy tensor conformal to the Maxwell theory. Distinctive
features of this model are: the absence of dimensional parameter for
non-linearity description and a very simple form of the dominant energy
condition, which can be easily verified in an arbitrary pseudo-riemannian
space-time with the consequent constrains on the model parameters. In this
paper we analyse some properties of astrophysical compact objects coupled to
conformal vacuum non-linear electrodynamics
Pseudo-epsilon expansion and the two-dimensional Ising model
Starting from the five-loop renormalization-group expansions for the
two-dimensional Euclidean scalar \phi^4 field theory (field-theoretical version
of two-dimensional Ising model), pseudo-\epsilon expansions for the Wilson
fixed point coordinate g*, critical exponents, and the sextic effective
coupling constant g_6 are obtained. Pseudo-\epsilon expansions for g*, inverse
susceptibility exponent \gamma, and g_6 are found to possess a remarkable
property - higher-order terms in these expansions turn out to be so small that
accurate enough numerical estimates can be obtained using simple Pade
approximants, i. e. without addressing resummation procedures based upon the
Borel transformation.Comment: 4 pages, 4 tables, few misprints avoide
Critical thermodynamics of two-dimensional N-vector cubic model in the five-loop approximation
The critical behavior of the two-dimensional N-vector cubic model is studied
within the field-theoretical renormalization-group (RG) approach. The
beta-functions and critical exponents are calculated in the five-loop
approximation, RG series obtained are resummed using Pade-Borel-Leroy and
conformal mapping techniques. It is found that for N = 2 the continuous line of
fixed points is well reproduced by the resummed RG series and an account for
the five-loop terms makes the lines of zeros of both beta-functions closer to
each another. For N > 2 the five-loop contributions are shown to shift the
cubic fixed point, given by the four-loop approximation, towards the Ising
fixed point. This confirms the idea that the existence of the cubic fixed point
in two dimensions under N > 2 is an artifact of the perturbative analysis. In
the case N = 0 the results obtained are compatible with the conclusion that the
impure critical behavior is controlled by the Ising fixed point.Comment: 18 pages, 4 figure
Polarization of the fermionic vacuum by a global monopole with finite core
We study the vacuum polarization effects associated with a massive fermionic
field in a spacetime produced by a global monopole considering a nontrivial
inner structure for it. In the general case of the spherically symmetric static
core with finite support we evaluate the vacuum expectation values of the
energy-momentum tensor and the fermionic condensate in the region outside the
core. These quantities are presented as the sum of point-like global monopole
and core-induced contributions. The asymptotic behavior of the core-induced
vacuum densities are investigated at large distances from the core, near the
core and for small values of the solid angle corresponding to strong
gravitational fields. As an application of general results the flower-pot model
for the monopole's core is considered and the expectation values inside the
core are evaluated.Comment: 22 pages, 4 figure
The catalogue of the discrete sources in the declination range from -13 deg to -2 deg
The results of the discrete source measurements with declinations -13 deg or = delta or = -2 deg and right ascensions 0 sub h + 24 sub h are given and were obtained as part of the systematic decametric survey of the celestial sphere with the rotatiotelecope UTR-2. Three hundred sixteen sources were found in the given declination range, four of which were observed for the first time. The source coordinates measured in the survey were compared with those from the 4th Cambridge survey at 178 MHz and the Parkes survey at 408 MHz
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