9,585 research outputs found
Universal Aspects of Gauge Field Localization on Branes in -dimensions
In this work, we study the general properties of the -vector field
localization on -brane with co-dimension . We consider a
conformally flat metric with the warp factor depending only on the transverse
extra dimensions. We employ the geometrical coupling mechanism and find an
analytical solution for the gauge field valid for any warp factor. Using
this solution we find that the only condition necessary for localization is
that the bulk geometry is asymptotically AdS. Therefore, our solution has an
universal validity for any warp factor and is independent of the particular
model considered. We also show that the model has no tachyonic modes. Finally,
we study the scalar components of the -vector field. As a general result, we
show that if we consider the coupling with the tensor and the Ricci scalar in
higher co-dimensions, there is an indication that both sectors will be
localized. As a concrete example, the above techniques are applied for the
intersecting brane model. We obtain that the branes introduce boundary
conditions that fix all parameters of the model in such a way that both
sectors, gauge and scalar fields, are confined.Comment: 26 pages, 5 figures, Accepted version for publication in JHE
Anisotropy and percolation threshold in a multifractal support
Recently a multifractal object, , was proposed to study percolation
properties in a multifractal support. The area and the number of neighbors of
the blocks of show a non-trivial behavior. The value of the
probability of occupation at the percolation threshold, , is a function
of , a parameter of which is related to its anisotropy. We
investigate the relation between and the average number of neighbors of
the blocks as well as the anisotropy of
Disorder effects at low temperatures in La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3} manganites
With the aim of probing the effect of magnetic disorder in the
low-temperature excitations of manganites, specific-heat measurements were
performed in zero field, and in magnetic fields up to 9 T in polycrystalline
samples of La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3}, with Y concentrations x=0, 0.10, and
0.15. Yttrium doping yielded the appearance of a cluster-glass state, giving
rise to unusual low-temperature behavior of the specific-heat. The main feature
observed in the results is a strong enhancement of the specific-heat linear
term, which is interpreted as a direct consequence of magnetic disorder. The
analysis was further corroborated by resistivity measurements in the same
compounds.Comment: 9 pages, 2 figure
A nonextensive insight to the stellar initial mass function
the present paper, we propose that the stellar initial mass distributions as
known as IMF are best fitted by -Weibulls that emerge within nonextensive
statistical mechanics. As a result, we show that the Salpeter's slope of
2.35 is replaced when a -Weibull distribution is used. Our results
point out that the nonextensive entropic index represents a new approach
for understanding the process of the star-forming and evolution of massive
stars.Comment: 5 pages, 2 figures, Accepted to EP
Consistency Conditions for -Form Fields Localization on Codimension two Braneworlds
Recently, in (Eur.Phys.J.C 80 (2020) 5, 432), the present authors obtained
general stringent conditions on the localization of fields in braneworlds by
imposing that its zero-mode must satisfy Einstein's equations (EE). Here, we
continue this study by considering free -form. These fields present an
on-shell equivalency relation between a -form and a -form, provided
by Hodge duality (HD). This symmetry will impose a new consistency condition,
namely, confinement of a -form must imply the localization of its dual. We
apply the above conditions to D braneworlds. With this, we find that in
global string-like defects, for example, the -form has a normalizable
zero-mode. By using the HD, we show that its bulk dual -form also has a
normalizable zero-mode, making the confinement consistent with HD. However,
these solutions cannot be made consistent with EE, therefore, these fields must
be ruled out. In fact, by imposing both conditions, only the scalar and its
dual field can be consistently localized. In this way, all the literature so
far in which the free -form is localized in codimension two models should be
reviewed. These results also point to the fact that the symmetries of the
fields can be used to verify the consistency of their localization and even
prohibit it.Comment: 39 pages and 2 figures. Final versio
Strong evidences for a nonextensive behavior of the rotation period in Open Clusters
Time-dependent nonextensivity in a stellar astrophysical scenario combines
nonextensive entropic indices derived from the modified Kawaler's
parametrization, and , obtained from rotational velocity distribution. These
's are related through a heuristic single relation given by , where is the cluster age. In a nonextensive
scenario, these indices are quantities that measure the degree of
nonextensivity present in the system. Recent studies reveal that the index
is correlated to the formation rate of high-energy tails present in the
distribution of rotation velocity. On the other hand, the index is
determined by the stellar rotation-age relationship. This depends on the
magnetic field configuration through the expression , where
and denote the saturation level of the star magnetic field and its
topology, respectively. In the present study, we show that the connection
is also consistent with 548 rotation period data for single
main-sequence stars in 11 Open Clusters aged less than 1 Gyr. The value of
2.5 from our unsaturated model shows that the mean magnetic field
topology of these stars is slightly more complex than a purely radial field.
Our results also suggest that stellar rotational braking behavior affects the
degree of anti-correlation between and cluster age . Finally, we suggest
that stellar magnetic braking can be scaled by the entropic index .Comment: 6 pages and 2 figures, accepted to EPL on October 17, 201
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