185 research outputs found
How effective is advertising in duopoly markets?
A simple Ising spin model which can describe the mechanism of advertising in
a duopoly market is proposed. In contrast to other agent-based models, the
influence does not flow inward from the surrounding neighbors to the center
site, but spreads outward from the center to the neighbors. The model thus
describes the spread of opinions among customers. It is shown via standard
Monte Carlo simulations that very simple rules and inclusion of an external
field -- an advertising campaign -- lead to phase transitions.Comment: 7 pages, 6 figures; v2: cosmetic change
Admixture of quasi-Dirac and Majorana neutrinos with tri-bimaximal mixing
We propose a realization of the so-called bimodal/schizophrenic model
proposed recently. We assume S4, the permutation group of four objects as
flavor symmetry giving tri-bimaximal lepton mixing at leading order. In these
models the second massive neutrino state is assumed quasi-Dirac and the
remaining neutrinos are Majorana states. In the case of inverse mass hierarchy,
the lower bound on the neutrinoless double beta decay parameter m_ee is about
two times that of the usual lower bound, within the range of sensitivity of the
next generation of experiments.Comment: 8 pages, minor changes to match version accepted in PL
Reactor mixing angle from hybrid neutrino masses
In terms of its eigenvector decomposition, the neutrino mass matrix (in the
basis where the charged lepton mass matrix is diagonal) can be understood as
originating from a tribimaximal dominant structure with small deviations, as
demanded by data. If neutrino masses originate from at least two different
mechanisms, referred to as "hybrid neutrino masses", the experimentally
observed structure naturally emerges provided one mechanism accounts for the
dominant tribimaximal structure while the other is responsible for the
deviations. We demonstrate the feasibility of this picture in a fairly
model-independent way by using lepton-number-violating effective operators,
whose structure we assume becomes dictated by an underlying flavor
symmetry. We show that if a second mechanism is at work, the requirement of
generating a reactor angle within its experimental range always fixes the solar
and atmospheric angles in agreement with data, in contrast to the case where
the deviations are induced by next-to-leading order effective operators. We
prove this idea is viable by constructing an -based ultraviolet
completion, where the dominant tribimaximal structure arises from the type-I
seesaw while the subleading contribution is determined by either type-II or
type-III seesaw driven by a non-trivial singlet (minimal hybrid model).
After finding general criteria, we identify all the symmetries
capable of producing such -based minimal hybrid models.Comment: 18 pages, 5 figures. v3: section including sum rules added, accepted
by JHE
Constraining neutrinoless double beta decay
A class of discrete flavor-symmetry-based models predicts constrained
neutrino mass matrix schemes that lead to specific neutrino mass sum-rules
(MSR). We show how these theories may constrain the absolute scale of neutrino
mass, leading in most of the cases to a lower bound on the neutrinoless double
beta decay effective amplitude.Comment: 12 pages, 12 figure
Relating quarks and leptons with the T-7 flavour group
In this letter we present a model for quarks and leptons based on T-7 as flavour symmetry, predicting a canonical mass relation between charged leptons and down-type quarks proposed earlier. Neutrino masses are generated through a Type-I seesaw mechanism, with predicted correlations between the atmospheric mixing angle and neutrino masses. Compatibility with oscillation results leads to lower bounds for the lightest neutrino mass as well as for the neutrinoless double beta decay rates, even for normal neutrino mass hierarchy
Accidental stability of dark matter
We propose that dark matter is stable as a consequence of an accidental Z2
that results from a flavour-symmetry group which is the double-cover group of
the symmetry group of one of the regular geometric solids. Although
model-dependent, the phenomenology resembles that of a generic Higgs portal
dark matter scheme.Comment: 12 pages, final version, published in JHE
Linear Collider Test of a Neutrinoless Double Beta Decay Mechanism in left-right Symmetric Theories
There are various diagrams leading to neutrinoless double beta decay in
left-right symmetric theories based on the gauge group SU(2)_L x SU(2)_R. All
can in principle be tested at a linear collider running in electron-electron
mode. We argue that the so-called lambda-diagram is the most promising one.
Taking the current limit on this diagram from double beta decay experiments, we
evaluate the relevant cross section e e to W_L W_R, where W_L is the Standard
Model W-boson and W_R the one from SU(2)_R. It is observable if the life-time
of double beta decay and the mass of the W_R are close to current limits. Beam
polarization effects and the high-energy behaviour of the cross section are
also analyzed.Comment: 17 pages, 6 figures. v2: minor changes, references added, to be
published in EPJ
Wide-Field InfraRed Survey Telescope (WFIRST) Final Report
In December 2010, NASA created a Science Definition Team (SDT) for WFIRST,
the Wide Field Infra-Red Survey Telescope, recommended by the Astro 2010
Decadal Survey as the highest priority for a large space mission. The SDT was
chartered to work with the WFIRST Project Office at GSFC and the Program Office
at JPL to produce a Design Reference Mission (DRM) for WFIRST. Part of the
original charge was to produce an interim design reference mission by mid-2011.
That document was delivered to NASA and widely circulated within the
astronomical community. In late 2011 the Astrophysics Division augmented its
original charge, asking for two design reference missions. The first of these,
DRM1, was to be a finalized version of the interim DRM, reducing overall
mission costs where possible. The second of these, DRM2, was to identify and
eliminate capabilities that overlapped with those of NASA's James Webb Space
Telescope (henceforth JWST), ESA's Euclid mission, and the NSF's ground-based
Large Synoptic Survey Telescope (henceforth LSST), and again to reduce overall
mission cost, while staying faithful to NWNH. This report presents both DRM1
and DRM2.Comment: 102 pages, 57 figures, 17 table
Deviation from Tri-Bimaximal Mixing and Large Reactor Mixing Angle
Recent observations for a non-zero have come from various
experiments. We study a model of lepton mixing with a 2-3 flavor symmetry to
accommodate the sizable measurement. In this work, we derive
deviations from the tri-bimaximal (TBM) pattern arising from breaking the
flavor symmetry in the neutrino sector, while the charged leptons contribution
has been discussed in a previous work. Contributions from both sectors towards
accommodating the non-zero measurement are presented.Comment: 25 pages, 12 figures. arXiv admin note: text overlap with
arXiv:1109.232
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