1,362 research outputs found
On structure of effective action in four-dimensional quantum dilaton supergravity
A general structure of effective action in new chiral superfield model
associated with , supergravity is investigated. This model
corresponds to finite quantum field theory and does not demand the
regularization and renormalization at effective action calculation. It is shown
that in local approximation the effective action is defined by two objects
called general superfield effective lagrangian and chiral superfield effective
lagrangian. A proper-time method is generalized for calculation of these two
effective lagrangians in superfield manner. Power expansion of the effective
action in supercovariant derivatives is formulated and the lower terms of such
an expansion are calculated in explicit superfield form
The Background Field Method for N = 2 Super Yang-Mills Theories in Harmonic Superspace
The background field method for N=2 super Yang-Mills theories in harmonic
superspace is developed. The ghost structure of the theory is investigated. It
is shown that the ghosts include two fermionic real omega-hypermultiplets
(Faddeev-Popov ghosts) and one bosonic real omega-hypermultiplet
(Nielsen-Kallosh ghost), all in the adjoint representation of the gauge group.
The one-loop effective action is analysed in detail and it is found that its
structure is determined only by the ghost corrections in the pure super
Yang-Mills theory. As applied to the case of N=4 super Yang-Mills theory,
realized in terms of N=2 superfields, the latter result leads to the remarkable
conclusion that the one-loop effective action of the theory does not contain
quantum corrections depending on the N=2 gauge superfield only. We show that
the leading low-energy contribution to the one-loop effective action in the N=2
SU(2) super Yang-Mills theory coincides with Seiberg's perturbative holomorphic
effective action.Comment: 17 pages, Late
Ionization corrections in a multi-phase interstellar medium: Lessons from a z~2 sub-DLA
We present a high resolution (FWHM=2.7 km/s), high S/N echelle spectrum for
the z = 2.26 QSO J2123-0050 and determine elemental abundances for the z = 2.06
sub-DLA in its line of sight. This high redshift sub-DLA has a complex
kinematic structure and harbours detections of neutral (SI, CI), singly (e.g.
CII, SII) and multiply ionized (e.g. CIV, SiIV) species as well as molecular H
and HD. The plethora of detected transitions in various ionization stages is
indicative of a complex multi-phase structure present in this high redshift
galaxy. We demonstrate that the ionization corrections in this sub-DLA are
significant (up to ~0.7 dex). For example, if no ionization correction is
applied, a super-solar metallicity is derived ([S/H] = +0.36), whereas a single
phase ionization correction reduces this to [S/H] = -0.19. The theoretical
impact of a multi-phase medium is investigated through Cloudy modelling and it
is found that the abundances of Si, S and Fe are always over-estimated (by up
to 0.15 dex in our experiments) if a single-phase is assumed. Therefore,
although Cloudy models improve estimates of metal column densities, the
simplification of a single phase medium leaves a systematic error in the
result, so that even ionization-corrected abundances may still be too high.
Without ionization corrections the properties of this sub-DLA appear to require
extreme scenarios of nucleosynthetic origins. After ionization corrections are
applied the ISM of this galaxy appears to be similar to some of the sightlines
through the Milky Way.Comment: Accepted for publication in MNRA
Comments on the Background Field Method in Harmonic Superspace: Non-holomorphic Corrections in N=4 SYM
We analyse the one-loop effective action of N=4 SYM theory in the framework
of the background field formalism in N=2 harmonic superspace. For the case of
on-shell background N=2 vector multiplet we prove that the effective action is
free of harmonic singularities. When the lowest N=1 superspace component of the
N=2 vector multiplet is switched off, the effective action of N=4 SYM theory is
shown to coincide with that obtained by Grisaru et al on the base of the N=1
background field method. We compute the leading non-holomorphic corrections to
the N=4 SU(2) SYM effective action.Comment: 15 pages, latex, no figures, some comments adde
Black hole and de Sitter solutions in a covariant renormalizable field theory of gravity
It is shown that Schwarzschild black hole and de Sitter solutions exist as
exact solutions of a recently proposed relativistic covariant formulation of
(power-counting) renormalizable gravity with a fluid. The formulation without a
fluid is also presented here. The stability of the solutions is studied and
their corresponding entropies are computed, by using the covariant Wald method.
The area law is shown to hold both for the Schwarzschild and for the de Sitter
solutions found, confirming that, for the case, one is dealing with a
minimal modification of GR.Comment: 7 paages, latex fil
Quantum evolution of Schwarzschild-de Sitter (Nariai) black holes
We calculate the one-loop effective action for conformal matter (scalars,
spinors and vectors) on spherically symmetric background. Such effective action
(in large approximation and expansion on curvature) is used to study
quantum aspects of Schwarzschild-de Sitter black holes (SdS BHs) in nearly
degenerated limit (Nariai BH). We show that for all types of above matter SdS
BHs may evaporate or anti-evaporate in accordance with recent observation by
Bousso and Hawking for minimal scalars. Some remarks about energy flow for SdS
BHs in regime of evaporation or anti-evaporation are also done. Study of no
boundary condition shows that this condition supports anti-evaporation for
nucleated BHs (at least in frames of our approximation). That indicates to the
possibility that some pair created cosmological BHs may not only evaporate but
also anti-evaporate. Hence, cosmological primordial BHs may survive much longer
than it is expected.Comment: Latex file, 20 pages, shortened versio
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