197 research outputs found
Analytical approach to the transition to thermal hopping in the thin- and thick-wall approximations
The nature of the transition from the quantum tunneling regime at low
temperatures to the thermal hopping regime at high temperatures is investigated
analytically in scalar field theory. An analytical bounce solution is
presented, which reproduces the action in the thin-wall as well as thick-wall
limits. The transition is first order for the case of a thin wall while for the
thick wall case it is second order.Comment: Latex file, 22 pages, 4 Postscript figure
Gamma-ray emission from pulsars
We have attempted to devise a scheme by which it may be possible to identify pulsars which are likely to be γ-ray pulsars. We apply this test to a representative population of pulsars and identify the likely candidates for γ emission. We also discuss some individual cases including the Crab and Vela pulsars
Globular clusters as gamma ray sources
There are indications now that globular clusters contain a large number of low magnetic field millisecond pulsars. Since
millisecond pulsars are expected to emit γ -rays due to curvature radiation, it is likely that globular clusters will themselves be
sources of γ -rays bright enough to be detectable by present day instruments. Using the expression derived by Scharlemann,
Arons & Fawley (1978) of the energy acquired by the electrons moving along the open magnetic field lines of the pulsars we
have calculated the likely luminosity of γ -rays from globular clusters. We discuss our results in the light of the calculations
reported in the literature based on some of the other models
Simultaneous cellulose hydrolysis and bio-electricity generation in a mediatorless Microbial Fuel Cell using a Bacillus flexus strain isolated from wastewater
The ability of electrochemically active bacteria to degrade natural wastes suggests a wide array of applications for waste management as well as electricity generation. This study reports the results of an experimentation where five bacteria were isolated from waste water and the electrochemical activity of one of them was confirmed by their use in a Microbial Fuel Cell. The bacterium was identified to be Bacillus flexus with a 99% similarity to the IFO 15715 strain using partial 16S rDNA sequencing. Phylogenetic analysis based on the BLAST results indicated close proximity to Bacillus megaterium, a known exoelectrogen
Bounce solutions and the transition to thermal hopping in phi^4 theory with a phi^3 term
The nature of the transition from quantum tunneling at low temperatures to
thermal hopping at high temperatures is investigated in a scalar field theory
with cubic symmetry breaking. The bounce solution which interpolates between
the zero-temperature and high-temperature solutions is obtained numerically,
using a multigrid method. It is found that, for a small value of the
symmetry-breaking coupling f, the transition is first-order. For higher values
of f, the transition continues to be first-order, though weakly so.Comment: Latex file with 18 figures, 29 page
Constraint On The Cosmological Constant From Gravitational Lenses In An Evolutionary Model Of Galaxies
We study the effect of the cosmological constant on the statistical
properties of gravitational lenses in flat cosmologies (Omega_{0}+lambda_{0} =
1). It is shown that some of the lens observables are strongly affected by the
cosmological constant, especially in a low--density universe, and its existence
might be inferred by a statistical study of the lenses. In particular, the
optical depth of the lens distribution may be used best for this purpose
without depending much on the lens model. We calculate the optical depth
(probabilty of a beam encountering with a lens event) for a source in a new
picture of galaxy evolution based on number evolution in addition to pure
luminosity evolution. It seems that present day galaxies result from the
merging of a large number of building blocks. We have tried to put limit on the
cosmological constant in this new picture of galaxy evolution. This
evolutionary model of galaxies permits larger value of cosmological constant.Comment: Latex file with two figures, 24 page
Low-mass Solitons from Fractional Charges in Quantum Chromodynamics
Slansky, Goldman, and Shaw have proposed a model to account for the observation of fractionally charged states. We show that in this model, there are expected to be several low-mass solitons (four being in the mass range ∼20-60 MeV) associated with the third homotopy group π3(SU(3)/SO(3))=Z4, besides a low-mass (∼30 MeV) Z2 monopole. Confirmation of these levels and hence of the model has important implications for Cabrera\u27s results on the magnetic monopole. An efficient algorithm for the calculation of π3(G/H) for a general Lie group G and a subgroup H is developed. It is pointed out that solitons associated with the third homotopy group are predicted by some grand-unified-theory scenarios
- …