26 research outputs found
Neutrino Masses from Non-minimal Gravitational Interactions of Massive Neutral Fermions
A new mechanism is proposed for generating neutrino masses radiatively
through a non-minimal coupling to gravity of fermionic bilinears involving
massive neutral fermions. Such coupling terms can arise in theories where the
gravity sector is augmented by a scalar field. They necessarily violate the
principle of equivalence, but such violations are not ruled out by present
experiments. It is shown that the proposed mechanism is realised most
convincingly in theories of the Randall- Sundrum type, where gravity couples
strongly in the TeV range. The mechanism has the potential for solving both the
solar and atmospheric neutrino problems. The smallness of neutrino masses in
this scenario is due to the fact that the interaction of the massive neutral
fermions arises entirely from higher-dimensional operators in the effective
Lagrangian.Comment: 7 page Latex 2e file, axodraw needed. Discussion and references
added. Version to appear in MPL
The effect of very low energy solar neutrinos on the MSW mechanism
We study some implications on standard matter oscillations of solar neutrinos
induced by a background of extremely low energy thermal neutrinos trapped
inside the Sun by means of coherent refractive interactions. Possible
experimental tests are envisaged and current data on solar neutrinos detected
at Earth are briefly discussed.Comment: RevTex4, 4 pages, no figure
On a generalized gravitational Aharonov-Bohm effect
A massless spinor particle is considered in the background gravitational
field due to a rotating body. In the weak field approximation it is shown that
the solution of the Weyl equations depend on the angular momentum of the
rotating body, which does not affect the curvature in this approximation. This
result may be looked upon as a generalization of the gravitational
Aharonov-Bohm effect.Comment: 10 pages, LATEX fil
Implications of observed neutrinoless double beta decay
Recently a positive indication of the neutrinoless double beta decay has been
announced. We study the implications of this result taking into consideration
earlier results on atmospheric neutrinos and solar neutrinos. We also include
in our discussions the recent results from SNO and K2K. We point out that on
the confidence level given for the double beta signal, the neutrino mass
matrices are now highly constrained. All models predicting Dirac masses are
ruled out and leptogenesis becomes a natural choice. Only the degenerate and
the inverted hierarchical solutions are allowed for the three generation
Majorana neutrinos. In both these cases we find that the radiative corrections
destabilize the solutions and the LOW, VO and Just So solutions of the solar
neutrinos are ruled out. For the four generation case only the inverted
hierarchical scenario is allowed.Comment: 16 pages, 2 postscript figure
Lorentz invariance with an invariant energy scale
We propose a modification of special relativity in which a physical energy,
which may be the Planck energy, joins the speed of light as an invariant, in
spite of a complete relativity of inertial frames and agreement with Einstein's
theory at low energies. This is accomplished by a non-linear modification of
the action of the Lorentz group on momentum space, generated by adding a
dilatation to each boost in such a way that the Planck energy remains
invariant. The associated algebra has unmodified structure constants, and we
highlight the similarities between the group action found and a transformation
previously proposed by Fock. We also discuss the resulting modifications of
field theory and suggest a modification of the equivalence principle which
determines how the new theory is embedded in general relativity
Probing the Planck Scale with Neutrino Oscillations
Quantum gravity "foam", among its various generic Lorentz non-invariant
effects, would cause neutrino mixing. It is shown here that, if the foam is
manifested as a nonrenormalizable effect at scale M, the oscillation length
generically decreases with energy as (E/M)^(-2). Neutrino observatories and
long-baseline experiments should have therefore already observed foam-induced
oscillations, even if M is as high as the Planck energy scale. The null
results, which can be further strengthened by better analysis of current data
and future experiments, can be taken as experimental evidence that Lorentz
invariance is fully preserved at the Planck scale, as is the case in critical
string theory.Comment: 11 pages, 2 figures. Final version published in PRD. 1 figure,
references, clarifications and explanations added. Results unchange
Quantum Violations of the Equivalence Principle in a Modified Schwarzschild Geometry. Neutrino Oscillations
Neutrino flavour oscillations are analyzed in a model in which particles
experience an effective Schwarzschild geometry modified by maximal acceleration
corrections. These imply a quantum violation of the equivalence principle. The
corresponding shifts in the phase of the neutrino mass eigenstates are
calculated and discussed.Comment: 10 pages. Accepted by Phys. Lett.