842 research outputs found
Operator splitting for the Benjamin-Ono equation
In this paper we analyze operator splitting for the Benjamin-Ono equation,
u_t = uu_x + Hu_xx, where H denotes the Hilbert transform. If the initial data
are sufficiently regular, we show the convergence of both Godunov and Strang
splitting.Comment: 18 Page
Non-topological gravitating defects in five-dimensional anti-de Sitter space
A class of five-dimensional warped solutions is presented. The geometry is
everywhere regular and tends to five-dimensional anti-de Sitter space for large
absolute values of the bulk coordinate. The physical features of the solutions
change depending on the value of an integer parameter. In particular, a set of
solutions describes generalized gravitating kinks where the scalar field
interpolates between two different minima of the potential. The other category
of solutions describes instead gravitating defects where the scalar profile is
always finite and reaches the same constant asymptote both for positive and
negative values of the bulk coordinate. In this sense the profiles are
non-topological. The physical features of the zero modes are discussed.Comment: 9 pages, 4 figure
Orbifold resolutions with general profile
A very general class of resolved versions of the C/Z_N, T^2/Z_N and S^1/Z_2
orbifolds is considered and the free theory of 6D chiral fermions studied on
it. As the orbifold limit is taken, localized 4D chiral massless fermions are
seen to arise at the fixed points. Their number, location and chirality is
found to be independent on the detailed profile of the resolving space and to
agree with the result of hep-th/0409229, in which a particular resolution was
employed. As a consistency check of the resolution procedure, the massive
equation is numerically studied. In particular, for S^1/Z_2, the "resolved"
mass--spectrum and wave functions in the internal space are seen to correctly
reproduce the usual orbifold ones, as the orbifold limit is taken.Comment: 28 pages, 3 figures, typos corrected, references adde
Modulus stabilization of generalized Randall Sundrum model with bulk scalar field
We study the stabilization of inter-brane spacing modulus of generalized
warped brane models with a nonzero brane cosmological constant. Employing
Goldberger-Wise stabilization prescription of brane world models with a bulk
scalar field, we show that the stabilized value of the modulus generally
depends on the value of the brane cosmological constant. Our result further
reveals that the stabilized modulus value corresponding to a vanishingly small
cosmological constant can only resolve the gauge hierarchy problem
simultaneously. This in turn vindicates the original Randall-Sundrum model
where the 3-brane cosmological constant was chosen to be zero.Comment: 12 Pages, 1 figure, Revtex, Version to appear in Euro. Phys. Let
INFLUENCE OF MORINGA OLEIFERA (DRUM-STICK) FRUIT EXTRACT ON HAEMATOLOGICAL PROFILE FOLLOWING REPEATED EXPOSURE TO LOW LEVELS OF ARSENIC THROUGH FEED ON RATS
Effect of Moringa oleifera fruits hot methanolic extract (MFE), if any, in minimizing the adverse reactions of repeated exposure to arsenic trioxide (AT) in feed was investigated in Wistar rats with reference to haematological profile. Three groups of rats each containing 10 (5male+5female) were used. The group I served as
negative control. Rats of group II were fed arsenic trioxide (AT) alone @ 100 ppm in feed while those of group III simultaneously received AT (@100 ppm) and MFE (50 mg/kg/day) for 28 days. Blood samples were collected from retroorbital plexus for estimation of hematological parameters (haemoglobin, PCV, TEC, MCH, MCHC, MCV) of different groups on 0 day, 15th day and 29th day respectively. Exposure to AT through feed in group II resulted in significant (P<0.05) decrease in haemoglobin, TEC and MCHC, accompanied by increased MCV, with no significant alteration of PCV or MCH of the rats. While rats of group III treated with AT (@100 ppm) and MFE (50 mg/kg/day) also resulted in same consequences as it was in group II but it was slightly less than that of group II suggesting of mild non significant protective effect
ANTIPYRETIC ACTIVITY OF BLUMEA LACERA LEAVES IN ALBINO RATS
The present study was carried out to determine the antipyretic activity of the methanolic extract of Blumea lacera leaves (BLE) on albino rats. Acute toxicity study of BLE was performed by limit test as per OECD guideline. Antipyretic activity was studied by inducing pyrexia with Brewer's yeast. Acute oral LD50 of BLE in female rats was more than 2000 mg/kg. Three ascending doses of 100 (1/20 LD50), 200 (1/10 LD50) and 400 mg/kg (1/5 LD50) were selected for studying the antipyretic activity of BLE in rats. BLE at dose rates of 200 and 400 mg/kg reduced brewer's yeast induced pyrexia in rats suggesting antipyretic effect of BLE
de Sitter branes with a bulk scalar
We propose new braneworld models arising from a scalar field in the bulk. In
these examples, the induced on--brane line element is de Sitter (or anti de
Sitter) and the bulk (five dimensional) Einstein equations can be exactly
solved to obtain warped spacetimes. The solutions thus derived are single and
two-brane models -- one with {\em thin} branes while the other one of the {\em
thick} variety. The field profiles and the potentials are obtained and analysed
for each case. We note that for the {\em thick} brane scenario the field
profile resembles a kink, whereas for one or more {\em thin} branes, it is
finite and bounded in the domain of the extra dimension. We have also addressed
the localisation of gravity and other matter fields on the brane for these
braneworld models.Comment: 18 pages, 5 figures. Substantial changes and new results. To appear
in GR
Fermion localization on degenerate and critical branes
In this work we analyze the localization of fermions on degenerate and
critical Bloch branes. This is done directly on physical coordinates, in
constrast to some works that has been using conformal coordinates. We find the
range of coupling constants of the interaction of fermions with the scalar
fields that allow us to have normalizable fermion zero-mode localized on the
brane on both, critical and degenerate Bloch branes. In the case of critical
branes our results agree with those found in [Class. Quantum Grav. \textbf{27}
(2010) 185001]. The results on fermion localization on degenerate Bloch branes
are new. We also propose a coupling of fermions to the scalar fields which
leads to localization of massless fermion on both sides of a double-brane.Comment: 16 pages, 6 figure
Cosmology and Fermion Confinement in a Scalar-Field-Generated Domain Wall Brane in Five Dimensions
We consider a brane generated by a scalar field domain wall configuration in
4+1 dimensions, interpolating, in most cases, between two vacua of the field.
We study the cosmology of such a system in the cases where the effective
four-dimensional brane metric is de Sitter or anti de Sitter, including a
discussion of the bulk coordinate singularities present in the de-Sitter case.
We demonstrate that a scalar field kink configuration can support a brane with
dS cosmology, despite the presence of coordinate singularities in the
metric. We examine the trapping of fermion fields on the domain wall for
nontrivial brane cosmology.Comment: 29 pages, 12 figures; minor changes, accepted by JHE
Geodesics and Geodesic Deviation in static Charged Black Holes
The radial motion along null geodesics in static charged black hole
space-times, in particular, the Reissner-Nordstr\"om and stringy charged black
holes are studied. We analyzed the properties of the effective potential. The
circular photon orbits in these space-times are investigated. We found that the
radius of circular photon orbits in both charged black holes are different and
differ from that given in Schwarzschild space-time. We studied the physical
effects of the gravitational field between two test particles in stringy
charged black hole and compared the results with that given in Schwarzschild
and Reissner-Nordstr\"om black holes.Comment: 12 pages, 5 figures, small changes, figures and references added,
conclusions changed. A improved, version accepted in Astrophysics and Space
Scienc
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