16,066 research outputs found
Scaling limit for a drainage network model
We consider the two dimensional version of a drainage network model
introduced by Gangopadhyay, Roy and Sarkar, and show that the appropriately
rescaled family of its paths converges in distribution to the Brownian web. We
do so by verifying the convergence criteria proposed by Fontes, Isopi, Newman
and Ravishankar.Comment: 15 page
Evading the Few TeV Perturbative Limit in 3-3-1 Models
Some versions of the electroweak SU(3)_L\otimesU(1)_X models cannot be
treated within perturbation theory at energies of few TeV. An extended version
for these models is proposed which is perturbative even at TeV scale posing no
threatening inconsistency for test at future colliders. The extension presented
here needs the addition of three octets of vector leptons, which leave three
new leptonic isotriplets in the SU(2)_L\otimesU(1)_Y subgroup. With this
representation content the running of the electroweak mixing angle, , is such that decreases with the increase of the
energy scale , when only the light states of the Standard Model group are
considered. The neutral exotic gauge boson marks then a new symmetry
frontier.Comment: 15 pages, 2 figures, minor correction
Charged shells in Lovelock gravity: Hamiltonian treatment and physical implications
Using a Hamiltonian treatment, charged thin shells in spherically symmetric
spacetimes in d dimensional Lovelock-Maxwell theory are studied. The
coefficients of the theory are chosen to obtain a sensible theory, with a
negative cosmological constant appearing naturally. After writing the action
and the Lagrangian for a spacetime comprised of an interior and an exterior
regions, with a thin shell as a boundary in between, one finds the Hamiltonian
using an ADM description. For spherically symmetric spacetimes, one reduces the
relevant constraints. The dynamic and constraint equations are obtained. The
vacuum solutions yield a division of the theory into two branches, d-2k-1>0
(which includes general relativity, Born-Infeld type theories) and d-2k-1=0
(which includes Chern-Simons type theories), where k gives the highest power of
the curvature in the Lagrangian. An additional parameter, chi, gives the
character of the vacuum solutions. For chi=1 the solutions have a black hole
character. For chi=-1 the solutions have a totally naked singularity character.
The integration through the thin shell takes care of the smooth junction. The
subsequent analysis is divided into two cases: static charged thin shell
configurations, and gravitationally collapsing charged dust shells. Physical
implications are drawn: if such a large extra dimension scenario is correct,
one can extract enough information from the outcome of those collapses as to
know, not only the actual dimension of spacetime, but also which particular
Lovelock gravity, is the correct one.Comment: 25 pages, 9 figure
The Left-Right SU(3)(L)xSU(3)(R)xU(1)(X) Model with Light, keV and Heavy Neutrinos
We construct a full left-right model for the electroweak interactions based
on the gauge symmetry. The fermion
content of the model is such that anomaly cancellation restricts the number of
families to be a multiple of three. One of the most important features of the
model is the joint presence of three light active neutrinos, three additional
neutrinos at keV mass scale, and six heavy ones with masses
around\textbf{} GeV. They form a well-motivated part of the spectrum
in the sense they address challenging problems related to neutrino oscillation,
warm dark matter, and baryogenesis through leptogenesis.Comment: 11 pages. Small corrections and typos fixed. Accepted for publication
in PR
Renormalisation scheme for vector fields on T2 with a diophantine frequency
We construct a rigorous renormalisation scheme for analytic vector fields on
the 2-torus of Poincare type. We show that iterating this procedure there is
convergence to a limit set with a ``Gauss map'' dynamics on it, related to the
continued fraction expansion of the slope of the frequencies. This is valid for
diophantine frequency vectors.Comment: final versio
The peculiar Na-O anticorrelation of the bulge globular cluster NGC 6440
Context. Galactic Globular Clusters (GCs) are essential tools to understand
the earliest epoch of the Milky Way, since they are among the oldest objects in
the Universe and can be used to trace its formation and evolution. Current
studies using high resolution spectroscopy for many stars in each of a large
sample of GCs allow us to develop a detailed observational picture about their
formation and their relation with the Galaxy. However, it is necessary to
complete this picture by including GCs that belong to all major Galactic
components, including the Bulge. Aims. Our aim is to perform a detailed
chemical analyses of the bulge GC NGC 6440 in order to determine if this object
has Multiple Populations (MPs) and investigate its relation with the Bulge of
the Milky Way and with the other Galactic GCs, especially those associated with
the Bulge, which are largely poorly studied. Methods. We determined the stellar
parameters and the chemical abundances of light elements (Na, Al), iron-peak
elements (Fe, Sc, Mn, Co, Ni), -elements (O, Mg, Si, Ca, Ti) and heavy
elements (Ba, Eu) in seven red giant members of NGC 6440 using high resolution
spectroscopy from FLAMES@UVES. Results. We found a mean iron content of
[Fe/H]=-0.500.03 dex in agreement with other studies. We found no internal
iron spread. On the other hand, Na and Al show a significant intrinsic spread,
but the cluster has no significant O-Na anticorrelation nor exhibits a Mg-Al
anticorrelation. The -elements show good agreement with the Bulge field
star trend, although they are at the high alpha end and are also higher than
those of other GCs of comparable metallicity. The heavy elements are dominated
by the r-process, indicating a strong contribution by SNeII. The chemical
analysis suggests an origin similar to that of the Bulge field stars.Comment: 12 pages, 13 figures, Accepted for publication in A&
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