39 research outputs found
Broken Symmetry as a Stabilizing Remnant
The Goldberger-Wise mechanism enables one to stabilize the length of the
warped extra dimension employed in Randall-Sundrum models. In this work we
generalize this mechanism to models with multiple warped throats sharing a
common ultraviolet brane. For independent throats this generalization is
straight forward. If the throats possess a discrete interchange symmetry like
Z_n the stabilizing dynamics may respect the symmetry, resulting in equal
throat lengths, or they may break it. In the latter case the ground state of an
initially symmetric configuration is a stabilized asymmetric configuration in
which the throat lengths differ. We focus on two- (three-) throat setups with a
Z_2 (Z_3) interchange symmetry and present stabilization dynamics suitable for
either breaking or maintaining the symmetry. Though admitting more general
application, our results are relevant for existing models in the literature,
including the two throat model with Kaluza-Klein parity and the three throat
model of flavor based on a broken Z_3 symmetry.Comment: 23 pages; v2 minor cosmetic chang
Exotic fermion multiplets as a solution to baryon asymmetry, dark matter and neutrino masses
We propose an extension to the standard model where three exotic fermion
5-plets and one scalar 6-plet are added to the particle content. By demanding
that all interactions are renormalizable and standard model gauge invariant, we
show that the lightest exotic particle in this model can be a dark matter
candidate as long as the new 6-plet scalar does not develop a nonzero vacuum
expectation value. Furthermore, light neutrino masses are generated radiatively
at one-loop while the baryon asymmetry is produced by the CP-violating decays
of the second lightest exotic particle. We have demonstrated using concrete
examples that there is a parameter space where a consistent solution to the
problems of baryon asymmetry, dark matter and neutrino masses can be obtained.Comment: 17 pages, 2 figures (REVTeX4.1), v2: some refs added, v3: typos
corrected, Sec.VI.B, C modified, this version to appear in PR
Electromagnetic Leptogenesis
We present a new leptogenesis scenario, where the lepton asymmetry is
generated by CP violating decays of heavy electroweak singlet neutrinos via
electromagnetic dipole moment couplings to the ordinary light neutrinos. Akin
to the usual scenario where the decays are mediated through Yukawa
interactions, we have shown, by explicit calculations, that the desired
asymmetry can be produced through the interference of the corresponding
tree-level and one-loop decay amplitudes involving the effective dipole moment
operators. We also find that the relationship of the leptogenesis scale to the
light neutrino masses is similar to that for the standard Yukawa-mediated
mechanism.Comment: 6 pages, 6 figures; v2: some references added, minor change to
discussion, accepted by PR
Leptogenesis implications in models with Abelian family symmetry and one extra real Higgs singlet
We show that the neutrino models, as suggested by Low, which have an
additional Abelian family symmetry and a real Higgs singlet to the default
see-saw do not hinder the possibility of successful thermal leptogenesis. For
these models (neglecting radiative effects), we have investigated the situation
of strong washout in both the one-flavor approximation and when flavor effects
are included. The result is that while such models predict that theta_{13}=0
and that one light neutrino to be massless, they do not modify or provide
significant constraints on the typical leptogenesis scenario where the final
asymmetry is dominated by the decays of the lightest right-handed neutrinos.Comment: 18 pages, RevTeX4, accepted by Phys. Rev. D. v2: minor corrections,
note and 1 ref. added, same content as published versio
Lifshitz theories with extra dimensions and 3+1-d Lorentz invariance
We construct Lifshitz scalar field theories in 4+1 dimensions which retain
3+1-d Lorentz invariance and therefore ensure a unique limiting speed in the
3+1-d world. Such a construction is potentially useful in developing
field-theoretic ultraviolet completions of extra-dimensional field theories.
The extra dimension y is treated asymmetrically from the usual three spatial
dimensions by introducing derivatives of order 2n with respect to y in the
action. We show that lambda phi^4 theory becomes progressively less
non-renormalisable by power counting as n is increased. This suggests that the
non-local theory obtained in the infinite-n limit may be complete in the
ultraviolet.Comment: 10 pages; added reference and discussion, this version to appear in
PR
Phenomenological constraints on minimally coupled exotic lepton triplets
By introducing a set of new triplet leptons (with nonzero hypercharge) that
can Yukawa couple to their Standard Model counterparts, new sources of
tree-level flavor changing currents are induced via mixing. In this work, we
study some of the consequences of such new contributions on processes such as
the leptonic decays of gauge bosons, and which violate lepton flavor, and mu-e conversion in
atomic nuclei. Constraints are then placed on the parameters associated with
the exotic triplets by invoking the current low-energy experimental data.
Moreover, the new physics contribution to the lepton anomalous magnetic moments
is calculated.Comment: 17 pages, 1 figure, 2 tables (REVTeX4.1); v2: refs added, to appear
in PR