10,843 research outputs found
Wormholes in spacetime with torsion
Analytical wormhole solutions in theory are presented. It is discussed
whether the extremely short range repulsive forces, related to the spin angular
momentum of matter, could be the ``carrier'' of the exoticity that threads the
wormhole throat.Comment: 10 pages revte
Purely electromagnetic spacetimes
Electrovacuum solutions devoid of usual mass sources are classified in the
case of one, two and three commuting Killing vectors. Three branches of
solutions exist. Electromagnetically induced mass terms appear in some of them.Comment: 8 page
Geometry of deformations of branes in warped backgrounds
The `braneworld' (described by the usual worldvolume action) is a D
dimensional timelike surface embedded in a N dimensional () warped,
nonfactorisable spacetime. We first address the conditions on the warp factor
required to have an extremal flat brane in a five dimensional background.
Subsequently, we deal with normal deformations of such extremal branes. The
ensuing Jacobi equations are analysed to obtain the stability condition. It
turns out that to have a stable brane, the warp factor should have a minimum at
the location of the brane in the given background spacetime. To illustrate our
results we explicitly check the extremality and stability criteria for a few
known co-dimension one braneworld models. Generalisations of the above
formalism for the cases of (i) curved branes (ii) asymmetrical warping and
(iii) higher co-dimension braneworlds are then presented alongwith some typical
examples for each. Finally, we summarize our results and provide perspectives
for future work along these lines.Comment: 21 pages. Version matching final version. Accepted for publication in
Class. Quant. Gra
Axially symmetric rotating traversable wormholes
This paper generalizes the static and spherically symmetric traversable
wormhole geometry to a rotating axially symmetric one with a time-dependent
angular velocity by means of an exact solution. It was found that the violation
of the weak energy condition, although unavoidable, is considerably less severe
than in the static spherically symmetric case. The radial tidal constraint is
more easily met due to the rotation. Similar improvements are seen in one of
the lateral tidal constraints. The magnitude of the angular velocity may have
little effect on the weak energy condition violation for an axially symmetric
wormhole. For a spherically symmetric one, however, the violation becomes less
severe with increasing angular velocity. The time rate of change of the angular
velocity, on the other hand, was found to have no effect at all. Finally, the
angular velocity must depend only on the radial coordinate, confirming an
earlier result.Comment: 17 pages, AMSTe
Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC
We propose a new method to determine at what transverse momenta particle
production in high-energy pp collisions is governed by hard parton-parton
processes. Using information on the transverse spatial distribution of partons
obtained from hard exclusive processes in ep/gamma p scattering, we evaluate
the impact parameter distribution of pp collisions with a hard parton-parton
process as a function of p_T of the produced parton (jet). We find that the
average pp impact parameters in such events depend very weakly on p_T in the
range 2 < p_T < few 100 GeV, while they are much smaller than those in
minimum-bias inelastic collisions. The impact parameters in turn govern the
observable transverse multiplicity in such events (in the direction
perpendicular to the trigger particle or jet). Measuring the transverse
multiplicity as a function of p_T thus provides an effective tool for
determining the minimum p_T for which a given trigger particle originates from
a hard parton-parton process. Additional tests of the proposed geometric
correlations are possible by measuring the dependence on the trigger rapidity.
Various strategies for implementing this method are outlined.Comment: 9 pages, 6 figure
Diffuse solar radiation and associated meteorological parameters in India
International audienceSolar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another
Evolving wormhole geometries
We present here analytical solutions of General Relativity that describe
evolving wormholes with a non-constant redshift function. We show that the
matter that threads these wormholes is not necessarily exotic. Finally, we
investigate some issues concerning WEC violation and human traversability in
these time-dependent geometries.Comment: 12 pages latex, 3 figures, to appear in Phys. Rev. D., Title
correcte
Design and evaluation of floating microspheres of amoxicillin trihydrate by ionotropic gelation method
The purpose of this investigation was to design and develop floating microspheres of Amoxicillin Trihydrate by ionotropic gelation method with combination of two polymers and to get the best possible formulation out of that with the various aspects. Floating drug delivery system have a bulk density less than gastric fluids and so remains buoyant in the stomach without affecting gastric emptying rate for a prolonged period of time. The floating microspheres were prepared using Ethyl cellulose and Hydroxy propylmethyl cellulose K4M as polymer to achieve an extended retention in upper GIT and there by improved bioavailability. The microspheres were evaluated for particle size analysis, Drug Entrapment Efficiency, Drug Loading Capacity, Floating efficiency, Swelling Study, Loose Surface Crystal Study , drug entrapment efficiency, drug- polymer compatibility study, Micromeritic properties like Bulk Density, Tapped Density, Carrâs Index, and Hausnerâs Ratio, In-vitro release studies and surface morphology characterized by Scanning electron microscopy (SEM). The Microspheres have an average size range of 743.00±7.000 to 837.00±8.544ÎŒm. The entrapment efficiency was found to be in the range of 66.96±1.944 to 82.03±0.657 %. The In-vitro release studies of the drug from the best formulation F6 exhibited a sustained release of 93.46±0.684 % as studied over 10hrs. Release was best explained by zero-order kinetics model and it shows that the drug release follows diffusion mechanism. FT-IR data revealed that, compatible and there was no interaction between the drug and excipients added in the formulation. The data obtained in this study thus suggest that a floating microspheres of Amoxicillin Trihydrate are promising for sustained drug delivery which can reduce dosing frequency
Focusing of timelike worldsheets in a theory of strings
An analysis of the generalised Raychaudhuri equations for string world sheets
is shown to lead to the notion of focusing of timelike worldsheets in the
classical Nambu-Goto theory of strings. The conditions under which such effects
can occur are obtained . Explicit solutions as well as the Cauchy initial value
problem are discussed. The results closely resemble their counterparts in the
theory of point particles which were obtained in the context of the analysis of
spacetime singularities in General Relativity many years ago.Comment: 14 pages, RevTex, no figures, extended, to appear in Phys Rev
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