211 research outputs found
Quantum corrections of Abelian Duality Transformations
A modification of the Abelian Duality transformations is proposed
guaranteeing that a (not necessarily conformally invariant) -model be
quantum equivalent (at least up to two loops in perturbation theory) to its
dual. This requires a somewhat non standard perturbative treatment of the {\sl
dual} -model. Explicit formulae of the modified duality transformation
are presented for a special class of block diagonal purely metric
-models.Comment: Latex 11 pages; remarks on a free model and references adde
Comment on "Finite Size Corrections to the Radiation Reaction Force in Classical Electrodynamics" [arXiv:1005.2617]
In [1, arXiv:1005.2617] effective field theory methods have been employed to
compute the equations of motion of a spherically symmetric charged shell of
radius R, taking into account the radiation reaction force exerted by the
shell's own electromagnetic field up to O(R^2). The authors of Ref. [1] have
stated that the known result for the self force of the shell as can be found
from Eq. (16.28) of the textbook of Jackson [2] (see also Chap. 4 in the review
of Pearle [3]) is incorrect, in that the term linear in R should be absent. We
claim that this conclusion of Ref. [1] is incorrect, and that the textbook
result, Eq. (1) does hold.Comment: 1 pag
On the equivalence between 2D Yukawa and Gross-Neveu models
We study numerically on the lattice the 2D Yukawa model with the U(1) chiral
symmetry and = 16 at infinite scalar field self-coupling. The scaling
behaviour of the fermion mass, as the Yukawa coupling approaches zero, is
analysed using the mean field method. It is found to agree with that of the
Gross-Neveu model with the same symmetry and . The results suggest that
the 2D Yukawa models belong to the universality class of the Gross-Neveu models
not only at weak scalar field self-coupling but also for a broad range of the
bare parameters which is not accessible to the expansion. New
universality classes might arise at the crossover to the spin model
universality class, however.Comment: 18 pages, Juelich HLRZ 111/9
Multiplier Sequences for Simple Sets of Polynomials
In this paper we give a new characterization of simple sets of polynomials B
with the property that the set of B-multiplier sequences contains all
Q-multiplier sequence for every simple set Q. We characterize sequences of real
numbers which are multiplier sequences for every simple set Q, and obtain some
results toward the partitioning of the set of classical multiplier sequences
Gravitational waves from binaries on unbound orbits
A generalized true anomaly-type parametrization, convenient to describe both
bound and open orbits of a two-body system in general relativity is introduced.
A complete description of the time evolution of both the radial and of the
angular equations of a binary system taking into account the first order
post-newtonian (1PN) is given. The gravitational radiation field emitted by the
system is computed in the 1PN approximation including higher multipole moments
beyond the standard quadrupole term. The gravitational waveforms in the time
domain are explicitly given up to the 1PN order for unbound orbits, but the
results are also illustrated on binaries on elliptic orbits with special
attention given to the effects of eccentricity.Comment: 27 pages, 10 figures, to appear in Phys. Rev.
Lattice Classification of 8-Dimensional Chiral Heterotic Strings
The eight-dimensional chiral rank 18 heterotic strings are classified using the covariant lattice approach
Resonant excitations of the 't Hooft-Polyakov monopole
The spherically symmetric magnetic monopole in an SU(2) gauge theory coupled
to a massless Higgs field is shown to possess an infinite number of resonances
or quasinormal modes. These modes are eigenfunctions of the isospin 1
perturbation equations with complex eigenvalues, ,
satisfying the outgoing radiation condition. For , their
frequencies approach the mass of the vector boson, , while
their lifetimes tend to infinity. The response of the monopole to
an arbitrary initial perturbation is largely determined by these resonant
modes, whose collective effect leads to the formation of a long living
breather-like excitation characterized by pulsations with a frequency
approaching and with an amplitude decaying at late times as .Comment: 4 page
Integrable Chiral Theories in 2+1 Dimensions
Following a recent proposal for integrable theories in higher dimensions
based on zero curvature, new Lorentz invariant submodels of the principal
chiral model in 2+1 dimensions are found. They have infinite local conserved
currents, which are explicitly given for the su(2) case. The construction works
for any Lie algebra and in any dimension, and it is given explicitly also for
su(3). We comment on the application to supersymmetric chiral models.Comment: 13 page
Boson stars and oscillatons in an inflationary universe
Spherically symmetric gravitationally bound, oscillating scalar lumps (boson
stars and oscillatons) are considered in Einstein's gravity coupled to massive
scalar fields in 1+D dimensional de Sitter-type inflationary space-times. We
show that due to inflation bosons stars and oscillatons lose mass through
scalar radiation, but at a rate that is exponentially small when the expansion
rate is slow.Comment: 19 pages, 5 figure
Computation of the radiation amplitude of oscillons
The radiation loss of small amplitude oscillons (very long-living, spatially
localized, time dependent solutions) in one dimensional scalar field theories
is computed in the small-amplitude expansion analytically using matched
asymptotic series expansions and Borel summation. The amplitude of the
radiation is beyond all orders in perturbation theory and the method used has
been developed by Segur and Kruskal in Phys. Rev. Lett. 58, 747 (1987). Our
results are in good agreement with those of long time numerical simulations of
oscillons.Comment: 22 pages, 9 figure
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