68,953 research outputs found
Neutrinos and Electromagnetic Gauge Invariance
It is discussed a recently proposed connection among U(1)
electromagnetic gauge invariance and the nature of the neutrino mass terms in
the framework of \mbox {SU(3)}_C\otimes G_W \otimes {\mbox U(1)}_N, =
SU(3), extensions of the Standard Model. The impossibility of that
connection, also in the extended case = SU(4), is demonstrated.Comment: 10 pages, Revtex 3.0, no figure
Positive Ricci curvature through Cheeger deformation
Let be a Riemannian manifold with an isometric -action. If a
principal orbit has finite fundamental group and , Searle--Wilhelm proved that admits a new metric of positive
Ricci curvature. is obtained after a conformal change followed by a
Cheeger deformation. The question remained on whether it is sufficient to
consider only the Cheeger deformation to attain positive Ricci curvature on the
new metric . Here we approach this question by giving necessary and
sufficient conditions on the -action. In particular, we construct an
infinite family of manifolds satisfying the hypothesis of Searle--Wilhelm that
do not develop positive Ricci curvature after Cheeger deformation. Further
exploring the theory, we give a alternative proofs for Lawson--Yau result on
positive scalar curvature under non-abelian symmetry, among others.Comment: 26 pages. Exposition reviewed. Applications include
Distinct magnetic signatures of fractional vortex configurations in multiband superconductors
Vortices carrying fractions of a flux quantum are predicted to exist in
multiband superconductors, where vortex core can split between multiple
band-specific components of the superconducting condensate. Using the
two-component Ginzburg-Landau model, we examine such vortex configurations in a
two-band superconducting slab in parallel magnetic field. The fractional
vortices appear due to the band-selective vortex penetration caused by
different thresholds for vortex entry within each band-condensate, and
stabilize near the edges of the sample. We show that the resulting fractional
vortex configurations leave distinct fingerprints in the static measurements of
the magnetization, as well as in ac dynamic measurements of the magnetic
susceptibility, both of which can be readily used for the detection of these
fascinating vortex states in several existing multiband superconductors.Comment: 5 pages, 4 figure
Physical regularization for the spin-1/2 Aharonov-Bohm problem in conical space
We examine the bound state and scattering problem of a spin-one-half particle
undergone to an Aharonov-Bohm potential in a conical space in the
nonrelativistic limit. The crucial problem of the \delta-function singularity
coming from the Zeeman spin interaction with the magnetic flux tube is solved
through the self-adjoint extension method. Using two different approaches
already known in the literature, both based on the self-adjoint extension
method, we obtain the self-adjoint extension parameter to the bound state and
scattering scenarios in terms of the physics of the problem. It is shown that
such a parameter is the same for both situations. The method is general and is
suitable for any quantum system with a singular Hamiltonian that has bound and
scattering states.Comment: Revtex4, 5 pages, published 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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