4,601 research outputs found
Topological Defects in the Left-Right Symmetric Model and their Relevance to Cosmology
It is shown that the minimal left-right symmetric model admits cosmic string
and domain wall solutions. The cosmic strings arise when the SU(2)_R is broken
and can either be destabilized at the electroweak scale or remain stable
through the subsequent breakdown to U(1)_{EM}. The strings carry zero modes of
the neutrino fields. Two distinct domain wall configurations exist above the
electroweak phase transition and disappear after that. Thier destablization
provides new sources of non-equilibrium effects below the electroweak scale
which is relevant to baryogenesis.Comment: 29 pages, LaTex file with 6 postscript figure
Cosmological Consequences of Spontaneous Lepton Number Violation in Grand Unification, EFI-93-07
Cosmological constraints on grand unified theories with spontaneous lepton
number violation are analysed. We concentrate on , the simplest of the
models possessing this property. It has been noted previously that the
consistency of these models with the observed baryon asymmetry generically
implies strict upper bounds on the light neutrino masses. In this paper, we
analyze the situation in detail. We find that minimal models of fermion masses
face difficulties, but that it is possible for these models to generate an
adequate baryon asymmetry via non-equilibrium lepton number violating processes
when the right-handed neutrino masses are near their maximum possible values.
This condition uniquely picks out the minimal gauge symmetry breaking scheme. A
non-minimal model is also analyzed, with somewhat different conclusions due to
the nature of the imposed symmetries.Comment: uses harvmac.tex, epsf.tex, and tables.tex; 4 figures submitted as
tar-compressed-uuencoded postscript files; beautiful compressed postscript
version available by anonymous ftp from
rainbow.uchicago.edu:/pt-preprints/efi-93-07.ps.
Low scale B-L extension of the Standard Model at the LHC
The fact that neutrinos are massive indicates that the Standard Model (SM)
requires extension. We propose a low energy (<TeV) B-L extension of the SM,
which is based on the gauge group SU(3)_C x SU(2)_L x U(1)_Y x U(1)_{B-L}. We
show that this model provides a natural explanation for the presence of three
right-handed neutrinos in addition to an extra gauge boson and a new scalar
Higgs. Therefore, it can lead to very interesting phenomenological implications
different from the SM results which can be tested at the LHC. Also we analyze
the muon anomalous magnetic moment in this class of models. We show that
one-loop with exchange Z' may give dominant new contribution ~ few x 10^{-11}.Comment: 12 page
Fully Constrained Majorana Neutrino Mass Matrices Using
In 2002, two neutrino mixing ansatze having trimaximally-mixed middle
() columns, namely tri-chi-maximal mixing () and
tri-phi-maximal mixing (), were proposed. In 2012, it was
shown that with as well as
with leads to the solution,
, consistent with the
latest measurements of the reactor mixing angle, . To obtain
and
, the type~I see-saw
framework with fully constrained Majorana neutrino mass matrices was utilised.
These mass matrices also resulted in the neutrino mass ratios,
.
In this paper we construct a flavour model based on the discrete group
and obtain the aforementioned results. A Majorana neutrino
mass matrix (a symmetric matrix with 6 complex degrees of freedom)
is conveniently mapped into a flavon field transforming as the complex 6
dimensional representation of . Specific vacuum alignments
of the flavons are used to arrive at the desired mass matrices.Comment: 20 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:1402.085
String Solitons
We review the status of solitons in superstring theory, with a view to
understanding the strong coupling regime. These {\it solitonic} solutions are
non-singular field configurations which solve the empty-space low-energy field
equations (generalized, whenever possible, to all orders in ), carry a
non-vanishing topological "magnetic" charge and are stabilized by a topological
conservation law. They are compared and contrasted with the {\it elementary}
solutions which are singular solutions of the field equations with a
-model source term and carry a non-vanishing Noether "electric" charge.
In both cases, the solutions of most interest are those which preserve half the
spacetime supersymmetries and saturate a Bogomol'nyi bound. They typically
arise as the extreme mass=charge limit of more general two-parameter solutions
with event horizons. We also describe the theory {\it dual} to the fundamental
string for which the roles of elementary and soliton solutions are
interchanged. In ten spacetime dimensions, this dual theory is a superfivebrane
and this gives rise to a string/fivebrane duality conjecture according to which
the fivebrane may be regarded as fundamental in its own right, with the
strongly coupled string corresponding to the weakly coupled fivebrane and
vice-versa. After compactification to four spacetime dimensions, the fivebrane
appears as a magnetic monopole or a dual string according as it wraps around
five or four of the compactified dimensions. This gives rise to a
four-dimensional string/string duality conjecture which subsumes a
Montonen-Olive type duality in that the magnetic monopoles of the fundamental
string correspond to the electric winding states of the dual string. This leads
to a {\it duality of dualities} whereby under string/string duality the the
strong/weak coupling -duality trades places with the minimum/maximum length
-duality. Since these magnetic monopoles are extreme black holes, a
prediction of -duality is that the corresponding electric massive states of
the fundamental string are also extreme black holes.Comment: 150 pages, TeX, submitted to Physics Reports, 3 figures available on
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