2,373 research outputs found
Construction of 3D wormhole supported by phantom energy
In this article, we have found a series solution of 3D Einstein equations
describing a wormhole for an inhomogeneous distribution of phantom energy.
Here, we assume equation of state is linear but highly anistropic.Comment: 9 papge, 4 figures. Accepted for publication in Physica Script
Vacuumless topological defects in Lyra geometry
Few years ago, Cho and Vilenkin have proposed that topological defects can
arise in symmetry breaking models without having degenerate vacua. These types
of defects are known as vacuumless defects. In the present work, the
gravitational field of a vacuumless global string and global monopole have been
investigated in the context of Lyra geometry. We find the metric of the
vacuumless global string and global monopole in the weak field approximations.
It has been shown that the vacuumless global string can have repulsive whereas
global monopole exerts attractive gravitational effects on a test particle. It
is dissimilar to the case studied in general relativity.Comment: 14 pages, 9 figures. To appear in Astrophys.Space.Sc
Gravitational field of domain wall in Lyra geometry
In this paper, we study the domain wall with time dependent displacement
vectors based on Lyra geometry in normal gauge i.e. displacement vector . The field theoretic energy momentum tensor is
considered with zero pressure perpendicular to the wall. We find an exact
solutions of Einstein equation for a scalar field with a potential
describing the gravitational field of a plane symmetric domain wall.
We have seen that the hyper surfaces parallel to the wall ()
are three dimensional de-sitter spaces. It is also shown that the gravitational
field experienced by test particle is attractive.Comment: 11 pages, 6 figures; Submitted in Astrophysics and Space Science
after minor revisio
Thin Domain Walls in Lyra Geometry
This paper studies thin domain walls within the frame work of Lyra Geometry.
We have considered two models. First one is the thin domain wall with
negligible pressures perpendicular and transverse direction to the wall and
secondly, we take a particular type of thin domain wall where the pressure in
the perpendicular direction is negligible but transverse pressures are existed.
It is shown that the thin domain walls have no particle horizon and the
gravitational force due to them is attractive.Comment: 8 pages, typos are corrected, published Astrophysics and Space
Sciences 305, 337 (2006
Thin-shell wormholes from charged black holes in generalized dilaton-axion gravity
This paper discusses a new type of thin-shell wormhole constructed by
applying the cut-and-paste technique to two copies of a charged black hole in
generalized dilaton-axion gravity, which was inspired by low-energy string
theory. After analyzing various aspects of this thin-shell wormhole, we discuss
its stability to linearized spherically symmetric perturbations.Comment: Minor changes, 6 pages, 4 figures. Accepted for publication in Gen.
Rel. Gra
Some new class of Chaplygin Wormholes
Some new class of Chaplygin wormholes are investigated in the framework of a
Chaplygin gas with equation of state , . Since
empty spacetime () does not follow Chaplygin gas, so the
interior Chaplygin wormhole solutions will never asymptotically flat. For this
reason, we have to match our interior wormhole solution with an exterior vacuum
solution i.e. Schwarzschild solution at some junction interface, say .
We also discuss the total amount of matter characterized by Chaplygin gas that
supplies fuel to construct a wormhole.Comment: 14 pages, 12 figures, Accepted for publication in Mod.Phys.Lett.
Local randomness in Hardy's correlations: Implications from information causality principle
Study of nonlocal correlations in term of Hardy's argument has been quite
popular in quantum mechanics. Recently Hardy's argument of non-locality has
been studied in the context of generalized non-signaling theory as well as
theory respecting information causality. Information causality condition
significantly reduces the success probability for Hardy's argument when
compared to the result based on non-signaling condition. Here motivated by the
fact that maximally entangled state in quantum mechanics does not exhibit
Hardy's non-local correlation, we do a qualitative study of the property of
local randomness of measured observable on each side reproducing Hardy's
non-locality correlation,in the context of information causality condition. On
applying the necessary condition for respecting the principle of information
causality, we find that there are severe restrictions on the local randomness
of measured observable in contrast to results obtained from no-signaling
condition.Still, there are some restrictions imposed by quantum mechanics that
are not obtained from information causality condition.Comment: 6 pages, 2 tables, new references adde
Thin-shell wormholes from black holes with dilaton and monopole fields
We provide a new type of thin-shell wormhole from the black holes with
dilaton and monopole fields. The dilaton and monopole that built the black
holes may supply fuel to construct the wormholes. Several characteristics of
this thin-shell wormhole have been discussed. Finally, we discuss the stability
of the thin-shell wormholes with a "phantom-like" equation of state for the
exotic matter at the throat.Comment: 6 pages and 3 figures, some typos are corrected and accepted in
Int.J.Theor.Phy
Tetramer Orbital-Ordering induced Lattice-Chirality in Ferrimagnetic, Polar MnTi2O4
Using density-functional theory calculations and experimental investigations
on structural, magnetic and dielectric properties, we have elucidated a unique
tetragonal ground state for MnTi2O4, a Ti^{3+} (3d^1)-ion containing
spinel-oxide. With lowering of temperature around 164 K, cubic MnTi2O4
undergoes a structural transition into a polar P4_1 tetragonal structure and at
further lower temperatures, around 45 K, the system undergoes a paramagnetic to
ferrimagnetic transition. Magnetic superexchange interactions involving Mn and
Ti spins and minimization of strain energy associated with co-operative
Jahn-Teller distortions plays a critical role in stabilization of the unique
tetramer-orbital ordered ground state which further gives rise to lattice
chirality through subtle Ti-Ti bond-length modulations
- …