15636466
Gaugino mass nonuniversality in an SO(10) supersymmetric grand unified theory: Low-energy spectra and collider signals
We derive the nonuniversal gaugino mass ratios in a supergravity (SUGRA) framework where the Higgs superfields belong to the nonsinglet representations 54 and 770 in an SO(10) grand unified theory (GUT). We evaluate the ratios for the phenomenologically viable intermediate breaking chain SU(4){sub C}xSU(2){sub L}xSU(2){sub R}(G{sub 422}). After a full calculation of the gaugino mass ratios, noting some errors in the earlier calculation for 54, we obtain, using the renormalization group equations, interesting low scale phenomenology of such breaking patterns. Here, we assume the breaking of the SO(10) GUT group to the intermediate gauge group and that to the standard model take place at the GUT scale itself. We also study the collider signatures in multilepton channels at the Large Hadron Collider (LHC) for some selected benchmark points allowed by the cold dark-matter relic density constraint provided by the WMAP data and compare these results with the minimal supergravity (mSUGRA) framework with similar gluino masses indicating their distinguishability in this regard.
10611151
Unitarity violation in sequential neutrino mixing in a model of extra dimensions
We give the first demonstration of unitarity violation in the sequential neutrino mixing matrix in a scenario with extra compact spacelike dimensions. Gauge singlet neutrinos are assumed to propagate in one extra dimension, giving rise to an infinite tower of states in the effective four-dimensional theory. It is shown that this leads to small lepton-number violating entries in the neutrino mass matrix, which can violate unitarity on the order of 1%.
55809021
Heptagonic symmetry for quarks and leptons
The non-Abelian discrete symmetry D(7) of the heptagon is successfully applied to both quark and lepton mass matrices, including CP violation.
118491017
Supersymmetric left–right model with radiative neutrino mass and multipartite dark matter
We propose a unified extension of the standard model with three types of coexisting dark matter, motivated by three well-studied scenarios: (1) supersymmetry with $$R$$R-parity conservation, (2) left–right symmetry where the $${SU}(2)_R$$SU(2)R doublet is not $$(\nu ,e)_R$$(ν,e)R but $$(n,e)_R$$(n,e)R where $$n$$n is a dark-matter candidate, and (3) a one-loop radiative neutrino mass model where the particles in the loop have an odd $$Z_2$$Z2 symmetry, the lightest of which is also a dark-matter candidate. Whereas there are many new particles in this model, the gauge couplings get unified in the same way as in the minimal supersymmetric standard model (MSSM). Since there are at least three dark-matter candidates, each one’s share of the total relic density of the Universe is adjustable, allowing for a much larger parameter space for the MSSM candidate itself. Our main focus is a careful study of a possible specific multipartite dark-matter scenario in this context.
123789901
Dark Matter Pions
We study the scenario where dark matter corresponds to a set of pseudoGoldstone bosons, that we call dark pions, generated by the spontaneous breaking of a symmetry in the dark sector. As a concrete example, we consider an SU(N)×SU(N) broken to the diagonal subgroup that remains an exact symmetry that ensures the stability of the dark pions, and allows a novel-interactions involving neutral gauge bosons and 3 dark pions. We study both experimental and theoretical constraints, and show that the model can accommodate all data in wide regions of parameter space.
14407716
Nonuniversal scalar masses: A signal-based analysis for the CERN Large Hadron Collider
We study the possible signatures of nonuniversal scalar masses in supersymmetry at the Large Hadron Collider (LHC). This is done, following our recent study on gaugino nonuniversality, via a multichannel analysis, based largely on the ratios of event rates for different final states, aimed at minimizing irregularity in the pattern due to extraneous effects and errors. We have studied (a) squark-slepton nonuniversality, (b) nonuniversality in sfermion masses of the third family, (c) the effects of SO(10) D-terms in supersymmetric grand unified theories. After presenting an elaborate numerical analysis of like- and opposite-sign dileptons, inclusive and hadronically quiet trileptons, as well as inclusive jet final states, we point out specific features of the spectrum in each case, which can be differentiated in the above channels from the spectrum for a minimal supergravity scenario with a universal scalar mass at high scale. The event selection criteria and the situations where the signals are sizable enough for a comparative study, are also delineated. It is found that, with some exceptions, the trilepton channels are likely to be especially useful for this purpose.
18344805
A Dynamical study of fission process and estimation of prescission neutron multiplicity
The dynamics of fission has been studied by solving Euler-Lagrange equation with dissipation generated through one and two body nuclear friction. The average kinetic energies of the fission fragments, prescission neutron multiplicities and the mean energies of the prescission neutrons have been calculated and compared with experimental values and they agree quite well. A single value of friction coefficient has been used to reproduce the experimental data for both symmetric and asymmetric splitting of the fissioning systems over a wide range of masses and excitation energies. It has been observed that a stronger friction is required in the saddle to scission region as compared to that in the ground state to saddle region.
125083170
Acoustic geometry through perturbation of mass accretion rate - axisymmetric flow in static spacetimes
This is the second of our series of papers devoted to the study of the stability analysis of the stationary transonic integral solutions for accretion flow onto a static compact object, using the acoustic geometry. Precisely, we consider accretion of an axisymmetric, inviscid and irrotational fluid in a general static axisymmetric spacetime and study the perturbation of the mass accretion rate, and demonstrate the natural emergence of the general relativistic acoustic geometry. In other words, the astrophysical accretion process has a natural interpretation as an example of the acoustic analogue gravity phenomenon. We also discuss two explicit examples of the Schwarzschild and the Rindler spacetimes. For the later, in particular, we demonstrate that for smooth flow fileds there can be no sonic point.
118213552
Acoustic geometry through perturbation of mass accretion rate : I - radial flow in general static spacetime
We propose a novel perturbation scheme to perform the linear stability analysis of stationary transonic integral accretion solutions corresponding to the hydrodynamic non self-gravitating radial flow of matter in a general static black hole spacetime. We demonstrate that a metric independent perturbation scheme can be developed, which leads to the emergence of the relativistic acoustic geometry and ensures the stability of the background stationary solutions. The acoustic metric obtained by perturbing the mass accretion rate rate is found to be identical with that obtained through the perturbation of the velocity potential. Our work thus makes a crucial connection between two apparently disjoint fields of study - accretion astrophysics and analogue gravity phenomena. We also formally prove that acoustic horizons never form in the Rindler spacetime.
117279651
Black holes and the positive cosmological constant
We address some aspects of black hole spacetimes endowed with a positive cosmological constant, i.e. black holes located inside a cosmological event horizon. First we establish a general criterion for existence of cosmological event horizons. Using the geometrical set up built for this, we study classical black hole no hair theorems for both static and stationary axisymmetric spacetimes. We discuss cosmic Nielsen-Olesen strings as hair in Schwarzschild-de Sitter spacetime. We also give a general calculation for particle creation by a Killing horizon using complex path analysis and using this we study particle creation in Schwarzschild-de Sitter spacetime by both black hole and the cosmological event horizons.
9862464
Black-hole no-hair theorems for a positive cosmological constant.
We extend all known black-hole no-hair theorems to space-times endowed with a positive cosmological constant Lambda. Specifically, we prove that static spherical black holes with Lambda > 0 cannot support scalar fields in convex potentials and Proca-massive vector fields in the region between the black hole and the cosmic horizon. We also demonstrate the existence of at least one type of quantum hair, and of exactly one charged solution for the Abelian Higgs model. Our method of proof can be applied to investigate other types of quantum or topological hair on black holes in the presence of a positive Lambda.