205 research outputs found
Classical Tests of General Relativity: Brane-World Sun from Minimal Geometric Deformation
We consider a solution of the effective four-dimensional brane-world
equations, obtained from the General Relativistic Schwarzschild metric via the
principle of Minimal Geometric Deformation, and investigate the corresponding
signatures stemming from the possible existence of a warped extra dimension. In
particular, we derive bounds on an extra-dimensional parameter, closely related
with the fundamental gravitational length, from the experimental results of the
classical tests of General Relativity in the Solar system.Comment: 6 pages, slightly improved, to appear in Europhysics Letter
Ultra peripheral heavy ion collisions and the energy dependence of the nuclear radius
To estimate realistic cross sections in ultra peripheral heavy ion collisions
we must remove effects of strong absorption. One method to eliminate these
effects make use of a Glauber model calculation, where the nucleon-nucleon
energy dependent cross sections at small impact parameter are suppressed. In
another method we impose a geometrical cut on the minimal impact parameter of
the nuclear collision (, where is the radius of ion
""). In this last case the effect of a possible nuclear radius dependence
with the energy has not been considered in detail up to now. Here we introduce
this effect showing that for final states with small invariant mass the effect
is negligible. However when the final state has a relatively large invariant
mass, e.g. an intermediate mass Higgs boson, the cross section can decrease up
to 50%.Comment: To appear in Phys. Lett.
Torsion Axial Vector and Yvon-Takabayashi Angle: Zitterbewegung, Chirality and all that
We consider propagating torsion as a completion of gravitation in order to
describe the dynamics of curved-twisted space-times filled with Dirac spinorial
fields; we discuss interesting relationships of the torsion axial vector and
the curvature tensor with the Yvon-Takabayashi angle and the module of the
spinor field, that is the two degrees of freedom of the spinor field itself: in
particular, we shall discuss in what way the torsion axial vector could be seen
as the potential of a specific interaction of the Yvon-Takabayashi angle, and
therefore as a force between the two chiral projections of the spinor field
itself. Chiral interactions of the components of a spinor may render effects of
zitterbewegung, as well as effective mass terms and other related features: we
shall briefly sketch some of the analogies and differences with the similar but
not identical situation given by the Yukawa interaction occurring in the Higgs
sector of the standard model. We will provide some overall considerations about
general consequences for contemporary physics, consequences that have never
been discussed before, so far as we are aware, in the present physics
literature.Comment: 8 page
Unveiling a spinor field classification with non-Abelian gauge symmetries
A spinor fields classification with non-Abelian gauge symmetries is
introduced, generalizing the the U(1) gauge symmetries-based Lounesto's
classification. Here, a more general classification, contrary to the Lounesto's
one, encompasses spinor multiplets, corresponding to non-Abelian gauge fields.
The particular case of SU(2) gauge symmetry, encompassing electroweak and
electromagnetic conserved charges, is then implemented by a non-Abelian spinor
classification, now involving 14 mixed classes of spinor doublets. A richer
flagpole, dipole, and flag-dipole structure naturally descends from this
general classification. The Lounesto's classification of spinors is shown to
arise as a Pauli's singlet, into this more general classification.Comment: 12 page
Non-existence of rest-frame spin-eigenstate spinors in their own electrodynamics
We assume a physical situation where gravity with torsion is neglected for an
electrodynamically self-interacting spinor that will be taken in its rest-frame
and spin-eigenstate: we demonstrate that under this circumstance no solution
exists for the system of field equations. Despite such a situation might look
artificial nevertheless it represents the instance that is commonly taken as
the basis for all computations of quantum electrodynamics.Comment: 5 page
New Spinor Fields on Lorentzian 7-Manifolds
This paper deals with the classification of spinor fields according to the
bilinear covariants in 7 dimensions. The previously investigated Riemannian
case is characterized by either one spinor field class, in the real case of
Majorana spinors, or three non-trivial classes in the most general complex
case. In this paper we show that by imposing appropriate conditions on spinor
fields in 7d manifolds with Lorentzian metric, the formerly obtained
obstructions for new classes of spinor fields can be circumvented. New spinor
fields classes are then explicitly constructed. In particular, on 7-manifolds
with asymptotically flat black hole background, these spinors can define a
generalized current density which further defines a time Killing vector at the
spatial infinity.Comment: 13 pages, improved, to match the final version accepted in JHE
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