2,054 research outputs found
Vector field localization and negative tension branes
It is shown that negative tension branes in higher dimensions may lead to an
effective lower dimensional theory where the gauge-invariant vector fields
associated with the fluctuations of the metric are always massless and
localized on the brane. Explicit five-dimensional examples of this phenomenon
are provided. Furthermore, it is shown that higher dimensional gauge fields can
also be localized on these configurations with the zero mode separated from the
massive tower by a gap.Comment: 16 pages, LaTeX style; to appear in Phys. Rev.
On the high order multiplicity moments
The description of multiplicity distributions in terms of the ratios of
cumulants to factorial moments is analyzed both for data and for the Monte
Carlo generated events. For the PYTHIA generated events the moments are
investigated for the restricted range of phase-space and for the jets
reconstructed from single particle momenta. The results cast doubts on the
validity of extended local parton-hadron duality and suggest the possibility of
more effective experimental investigations concerning the origin of the
observed structure in the dependence of moments on their order.Comment: 10 pages, 5 figures; corrected version to be published in JP
Clan structure analysis and QCD parton showers in multiparticle dynamics. An intriguing dialog between theory and experiment
This paper contains a review of the main results of a search of regularities
in collective variables properties in multiparticle dynamics, regularities
which can be considered as manifestations of the original simplicity suggested
by QCD. The method is based on a continuous dialog between experiment and
theory. The paper follows the development of this research line, from its
beginnings in the seventies to the current state of the art, discussing how it
produced both sound interpretations of the most relevant experimental facts and
intriguing perspectives for new physics signals in the TeV energy domain.Comment: 118 pages, 48 figures; table of contents fixed for hyperre
Gauge-invariant fluctuations of scalar branes
A generalization of the Bardeen formalism to the case of warped geometries is
presented. The system determining the gauge-invariant fluctuations of the
metric induced by the scalar fluctuations of the brane is reduced to a set of
Schr\"odinger-like equations for the Bardeen potentials and for the canonical
normal modes of the scalar-tensor action. Scalar, vector and tensor modes of
the geometry are classified according to four-dimensional Lorentz
transformations. While the tensor modes of the geometry live on the brane
determining the corrections to Newton law, the scalar and and vector
fluctuations exhibit non normalizable zero modes and are, consequently, not
localized on the brane. The spectrum of the massive modes of the fluctuations
is analyzed using supersymmetric quantum mechanics.Comment: 29 pages in Latex styl
QCD and hybrid NBD on oscillating moments of multiplicity distributions in lepton- and hadron-initiated reactions
QCD predictions for moments of multiplicity distributions are compared with
experimental data on e+e- collisions and their two-NBD fits. Moments of the
multiplicity distribution in a two-NBD model for 1.8 TeV pp collisions are
considered. Three-NBD model predictions and fits for pp at LHC energies are
also discussed. Analytic expressions for moments of hybrid NBD are derived and
used to get insight into jet parameters and multicomponent structure of the
processes. Interpretation of observed correlations is proposed.Comment: 8 pages, no figures, Phys. Lett.
The Broad Line Radio Galaxy J2114+820
In the frame of the study of a new sample of large angular size radio
galaxies selected from the NRAO VLA Sky Survey, we have made radio observations
of J2114+820, a low power radio galaxy with an angular size of 6'. Its radio
structure basically consists of a prominent core, a jet directed in north-west
direction and two extended S-shaped lobes. We have also observed the optical
counterpart of J2114+820, a bright elliptical galaxy with a strong unresolved
central component. The optical spectrum shows broad emission lines. This fact,
together with its low radio power and FR-I type morphology, renders J2114+820 a
non-trivial object from the point of view of the current unification schemes of
radio loud active galactic nuclei.Comment: 6 pages, 5 figures. To appear in the proceedings of EVN/JIVE
Symposium No. 4, New Astronomy Reviews (eds. Garrett et al.
Six-dimensional Abelian vortices with quadratic curvature self-interactions
Six-dimensional Nielsen-Olesen vortices are analyzed in the context of a
quadratic gravity theory containing Euler-Gauss-Bonnet self-interactions. The
relations among the string tensions can be tuned in such a way that the
obtained solutions lead to warped compactification on the vortex. New regular
solutions are possible in comparison with the case where the gravity action
only consists of the Einstein-Hilbert term. The parameter space of the model is
discussedComment: 28 pages in Latex style with 11 figure
Fluid phonons and inflaton quanta at the protoinflationary transition
Quantum and thermal fluctuations of an irrotational fluid are studied across
the transition regime connecting a protoinflationary phase of decelerated
expansion to an accelerated epoch driven by a single inflaton field. The
protoinflationary inhomogeneities are suppressed when the transition to the
slow roll phase occurs sharply over space-like hypersurfaces of constant energy
density. If the transition is delayed, the interaction of the quasi-normal
modes related, asymptotically, to fluid phonons and inflaton quanta leads to an
enhancement of curvature perturbations. It is shown that the dynamics of the
fluctuations across the protoinflationary boundaries is determined by the
monotonicity properties of the pump fields controlling the energy transfer
between the background geometry and the quasi-normal modes of the fluctuations.
After corroborating the analytical arguments with explicit numerical examples,
general lessons are drawn on the classification of the protoinflationary
transition.Comment: 30 pages, 3 figure
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