4,825 research outputs found
A [SU(6)] FLAVOR MODEL WITHOUT MIRROR FERMIONS
We introduce a three family extension of the Pati-Salam model which is
anomaly-free and contains in a single irreducible representation the known
quarks and leptons without mirror fermions. Assuming that the breaking of the
symmetry admits the implementation of the survival hypothesis, we calculate the
mass scales using the renormalization group equation. Finally we show that the
proton remains perturbatively stable.Comment: Z PHYS. C63, 339 (1994
Effective spacetime from multi-dimensional gravity
We study the effective spacetimes in lower dimensions that can be extracted
from a multidimensional generalization of the Schwarzschild-Tangherlini
spacetimes derived by Fadeev, Ivashchuk and Melnikov ({\it Phys. Lett,} {\bf A
161} (1991) 98). The higher-dimensional spacetime has
dimensions, where and are the number of "internal" and "external" extra
dimensions, respectively. We analyze the effective spacetime obtained
after dimensional reduction of the external dimensions. We find that when
the extra dimensions are compact (i) the physics in lower dimensions is
independent of and the character of the singularities in higher dimensions,
and (ii) the total gravitational mass of the effective matter distribution
is less than the Schwarzshild mass. In contrast, when the extra dimensions
are large this is not so; the physics in does explicitly depend on
, as well as on the nature of the singularities in high dimensions, and the
mass of the effective matter distribution (with the exception of wormhole-like
distributions) is bigger than the Schwarzshild mass. These results may be
relevant to observations for an experimental/observational test of the theory.Comment: A typo in Eq. (24) is fixe
Minimal Scalar Sector of 3-3-1 Models without Exotic Electric Charges
We study the minimal set of Higgs scalars, for models based on the local
gauge group which do not contain
particles with exotic electric charges. We show that only two Higgs
triplets are needed in order to properly break the symmetry. The exact
tree-level scalar mass matrices resulting from symmetry breaking are calculated
at the minimum of the most general scalar potential, and the gauge bosons are
obtained, together with their couplings to the physical scalar fields. We show
how the scalar sector introduced is enough to produce masses for fermions in a
particular model which is an subgroup. By using experimental results we
constrain the scale of new physics to be above 1.3 TeV.Comment: LaTeX, 22 pages, 1 figure include
Neutral perfect fluids of Majumdar-type in general relativity
We consider the extension of the Majumdar-type class of static solutions for
the Einstein-Maxwell equations, proposed by Ida to include charged perfect
fluid sources. We impose the equation of state and discuss
spherically symmetric solutions for the linear potential equation satisfied by
the metric. In this particular case the fluid charge density vanishes and we
locate the arising neutral perfect fluid in the intermediate region defined by
two thin shells with respective charges and . With its innermost flat
and external (Schwarzschild) asymptotically flat spacetime regions, the
resultant condenser-like geometries resemble solutions discussed by Cohen and
Cohen in a different context. We explore this relationship and point out an
exotic gravitational property of our neutral perfect fluid. We mention possible
continuations of this study to embrace non-spherically symmetric situations and
higher dimensional spacetimes.Comment: 9 page
Supersymmetric One-family Model without Higgsinos
The Higgs potential and the mass spectrum of the N=1 supersymmetric extension
of a recently proposed one-family model based on the local gauge group , which is a subgroup of the electroweak-strong
unification group , is analyzed. In this model the slepton multiplets play
the role of the Higgs scalars and no Higgsinos are needed, with the consequence
that the sneutrino, the selectron and six other sleptons play the role of the
Goldstone bosons. We show how the problem is successfully addressed in
the context of this model which also predicts the existence of a light CP-odd
scalar.Comment: REVTeX 4, 10 pages. Included discussions about constraints coming
from the rho-parameter and from Muon (g-2). References added. Version to
appear in Phys. Rev.
Stars in five dimensional Kaluza Klein gravity
In the five dimensional Kaluza Klein (KK) theory there is a well known class
of static and electromagnetic--free KK--equations characterized by a naked
singularity behavior, namely the Generalized Schwarzschild solution (GSS). We
present here a set of interior solutions of five dimensional KK--equations.
These equations have been numerically integrated to match the GSS in the
vacuum. The solutions are candidates to describe the possible interior perfect
fluid source of the exterior GSS metric and thus they can be models for stars
for static, neutral astrophysical objects in the ordinary (four dimensional)
spacetime.Comment: 15 pages, 8 figures. To be published in EPJ
Evolving weighting schemes for the Bag of Visual Words
The Bag of Visual Words (BoVW) is an established representation in computer vision. Taking inspiration from text mining, this representation has proved to be very effective in many domains. However, in most cases, standard term-weighting schemes are adopted (e.g., term-frequency or TF-IDF). It remains open the question of whether alternative weighting schemes could boost the performance of methods based on BoVW. More importantly, it is unknown whether it is possible to automatically learn and determine effective weighting schemes from scratch. This paper brings some light into both of these unknowns. On the one hand, we report an evaluation of the most common weighting schemes used in text mining, but rarely used in computer vision tasks. Besides, we propose an evolutionary algorithm capable of automatically learning weighting schemes for computer vision problems. We report empirical results of an extensive study in several computer vision problems. Results show the usefulness of the proposed method
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