92 research outputs found
Multiparticle Threshold Amplitudes Exponentiate in Arbitrary Scalar Theories
Threshold amplitudes are considered for -particle production in arbitrary
scalar theory. It is found that, like in , leading- corrections to
the tree level amplitudes, being summed over all loops, exponentiate. This
result provides more evidence in favor of the conjecture on the exponential
behavior of the multiparticle amplitudes.Comment: 9 pages, latex, 3 latex figure
Dynamical vs spectator models of (pseudo-)conformal Universe
We discuss two versions of the conformal scenario for generating scalar
cosmological perturbations: a spectator version with a scalar field conformally
coupled to gravity and carrying negligible energy density, and a dynamical
version with a scalar field minimally coupled to gravity and dominating the
cosmological evolution. By making use of the Newtonian gauge, we show that (i)
no UV strong coupling scale is generated below due to mixing with
metric perturbations in the dynamical scenario, and (ii) the dynamical and
spectator models yield identical results to the leading non-linear order. We
argue that these results, which include potentially observable effects like
statistical anisotropy and non-Gaussianity, are characteristic of the entire
class of conformal models. As an example, we reproduce, within the dynamical
scenario and working in comoving gauge, our earlier result on the statistical
anisotropy, which was originally obtained within the spectator approach.Comment: 13 page
Three fermionic generations on a topological defect in extra dimensions
We suggest a mechanism explaining the origin of three generations of the
Standard Model fermions from one generation in a higher-dimensional theory.
Four-dimensional fermions appear as zero modes trapped in the core of a
topological defect with topological number three. We discuss hierarchical
pattern of masses and mixings which arises in these models.Comment: 19 pages, no figures; v.2: references added, main text unchange
O(4) symmetric singular solutions and multiparticle cross sections in theory at tree level
We solve the classical euclidean boundary value problem for tree-level
multiparticle production in theory at arbitrary energies in the case
of symmetric field configurations. We reproduce known low-energy results
and obtain a lower bound on the tree cross sections at arbitrary energies.Comment: LaTeX, 9pp + 2 Postscript figures, tar-compressed and uuencoded using
uufiles; minor Postscript bug fixe
Properties of scalar perturbations generated by conformal scalar field
Primordial scalar perturbations may be generated when complex conformal
scalar field rolls down its negative quartic potential. We begin with the
discussion of peculiar infrared properties of this scenario. We then consider
the statistical anisotropy inherent in the model. Finally, we discuss the
non-Gaussianity of scalar perturbations. Because of symmetries, the bispectrum
vanishes identically. We present a general expression for the trispectrum and
give its explicit form in the folded limit.Comment: Prepared for "Gravity and Cosmology (GC2010)" workshop, Kyoto, Japan,
May,24-July,16, 2010; 15 pages, 1 figur
On holography for (pseudo-)conformal cosmology
We propose a holographic dual for (pseudo-)conformal cosmological scenario,
with a scalar field that forms a moving domain wall in adS_5. The domain wall
separates two vacua with unequal energy densities. Unlike in the existing
construction, the 5d solution is regular in the relevant space-time domain.Comment: 6 pages, 1 figur
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