5,803 research outputs found
Neutrino mass generation in the SO(4) model
Generation of neutrino mass in SO(4) model is proposed here. The algebraic
structure of SO(4) is same as to that of . It is
shown that the spontaneous symmetry breaking results three massive as well as
three massless gauge bosons. The standard model theory according to which there
exist three massive gauge bosons and a massless one is emerged from this model.
In the framework of a small Dirac neutrino mass is
derived. It is also shown that such mass term may vanish with a special choice.
The Majorana mass term is not considered here and thus in this model the
neutrino mass does not follow seesaw structure.Comment: 7 pages, no figur
Radiative neutrino decay and CP-violation in R-parity violating supersymmetry
We calculate the radiative decay amplitude for Majorana neutrinos in
trilinear R-parity violating supersymmetric framework. Our results make no
assumption regarding the masses and mixings of fermions and sfermions. The
results obtained are exemplary for generic models with loop-generated neutrino
masses. Comparison of this amplitude with the neutrino mass matrix shows that
the two provide independent probes of CP-violating phases.Comment: Latex, uses axodraw, 14 pages (small changes implemented
On a three-tier ecological food chain model with deterministic and random harvesting: A mathematical study
In the present study, we consider a nutrient-autotroph-herbivore ecosystem model where the herbivore species is assumed to have a commercial value. We use a Holling type-II harvest function to model density dependent herbivore harvesting. Stability criteria of the resulting model is investigated both from analytical and numerical viewpoints. The investigation revealed the existence of a number of threshold values of the harvest rate that have a remarkable influence on the system dynamics. Next we incorporate a noise term in the parameter representing harvest rate to model the phenomenon of poaching as random harvesting. The stochastic model is analyzed for exponential mean square stability and the resulting criteria in terms of harvest related parameters obtained. These parameter thresholds could be utilized to develop effective harvesting strategies and wildlife management policies which take into account the overall survival of the ecological populations
Effect of Fibonacci Modulation On Superconductivity
We have studied finite-sized single band models with short range pairing
interactions between electrons in presence of diagonal Fibonacci modulation in
one dimension. Two models, namely the attractive Hubbard model and the
Penson-Kolb model, have been investigated at half-filling at zero temperature
by solving the Bogoliubov-de Gennes equations in real space within a mean field
approximation. The competition between ``disorder'' and the pairing interaction
leads to a suppression of superconductivity (of usual pairs with zero
centre-of-mass momenta) in the strong-coupling limit while an enhancement of
the pairing correlation is observed in the weak-coupling regime for both the
models. However, the dissimilarity of the pairing mechanisms in these two
models brings about notable difference in the results. The extent to which the
bond ordered wave and the -paired (of pairs with centre-of-mass momenta =
) phases of the Penson-Kolb model are affected by the disorder has also
been studied in the present calculation. Some finite size effects are also
identified.Comment: 14 pages, 13 figure
Estimation of (Cl-Mn)/Fe flux ratio at relativistic energies using steady-state leaky-box model modified for reaccelerations
The (Cl-Mn)OFe flux ratio at the top of the atmosphere has been estimated from source composition. We have adopted the SSLB model modified for weak shocks to estimate the enhancement of (Cl-Mn)OFe flux ratio due to reacceleration. The observed active detector results of Lezniak and Webber,
Caldwell, Orth et al., Engelmann et al., and our passive detector results are fairly supported by the expected results from the SSLB model modified with reacceleration after Ferrando for energies G100 GeVOn
Hybrid fuzzy particle swarm optimization approach for reactive power optimization
This paper presents a new approach to the optimal reactive power planning based on fuzzy logic and particle swarm optimization (PSO). The objectives are to minimize real power loss and to improve the voltage profile of a given interconnected power system. Transmission loss is expressed in terms of voltage increments by relating the control variables i.e. reactive var generations by the generators, tap positions of transformers and reactive power injections by the shunt capacitors. The objective function and the constraints are modeled by fuzzy sets. A term ‘sensitivity’ at each bus is defined which depends on variation of real power loss with respect to the voltage at that bus. Based on the Fuzzy membership values of the sensitivity, corrective action at a particular bus is taken i.e. shunt capacitors are installed at the candidate buses based on real power loss and sets of solution. Then, PSO is applied to get final solution. PSO is used for optimal setting of transformer tap positions and reactive generations of generators. The solutions obtained by this method is compared with the solutions obtained by other evolutionary algorithms like genetic algorithm (GA), differential evolution (DE) and particle swarm optimization (PSO)
Upper bounds on all R-parity-violating \lambda\lambda'' combinations from proton stability
In an R-parity-violating supersymmetric theory, we derive upper bounds on all
the \lambda''_{ijk}\lambda_{i'j'k'}-type combinations from the consideration of
proton stability, where \lambda''_{ijk} are baryon-number-violating couplings
involving three baryonic fields and \lambda_{i'j'k'} are
lepton-number-violating couplings involving three leptonic fields.Comment: 5 pages, Latex, uses axodraw.sty; minor changes in the text. Final
versio
A Cosmic Census of Radio Pulsars with the SKA
The Square Kilometre Array (SKA) will make ground breaking discoveries in
pulsar science. In this chapter we outline the SKA surveys for new pulsars, as
well as how we will perform the necessary follow-up timing observations. The
SKA's wide field-of-view, high sensitivity, multi-beaming and sub-arraying
capabilities, coupled with advanced pulsar search backends, will result in the
discovery of a large population of pulsars. These will enable the SKA's pulsar
science goals (tests of General Relativity with pulsar binary systems,
investigating black hole theorems with pulsar-black hole binaries, and direct
detection of gravitational waves in a pulsar timing array). Using SKA1-MID and
SKA1-LOW we will survey the Milky Way to unprecedented depth, increasing the
number of known pulsars by more than an order of magnitude. SKA2 will
potentially find all the Galactic radio-emitting pulsars in the SKA sky which
are beamed in our direction. This will give a clear picture of the birth
properties of pulsars and of the gravitational potential, magnetic field
structure and interstellar matter content of the Galaxy. Targeted searches will
enable detection of exotic systems, such as the ~1000 pulsars we infer to be
closely orbiting Sgr A*, the supermassive black hole in the Galactic Centre. In
addition, the SKA's sensitivity will be sufficient to detect pulsars in local
group galaxies. To derive the spin characteristics of the discoveries we will
perform live searches, and use sub-arraying and dynamic scheduling to time
pulsars as soon as they are discovered, while simultaneously continuing survey
observations. The large projected number of discoveries suggests that we will
uncover currently unknown rare systems that can be exploited to push the
boundaries of our understanding of astrophysics and provide tools for testing
physics, as has been done by the pulsar community in the past.Comment: 20 pages, 7 figures, to be published in: "Advancing Astrophysics with
the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)04
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