2,609 research outputs found
Static and symmetric wormholes respecting energy conditions in Einstein-Gauss-Bonnet gravity
Properties of -dimensional static wormhole solutions are
investigated in Einstein-Gauss-Bonnet gravity with or without a cosmological
constant . We assume that the spacetime has symmetries corresponding
to the isometries of an -dimensional maximally symmetric space with the
sectional curvature . It is also assumed that the metric is at
least and the -dimensional maximally symmetric subspace is
compact. Depending on the existence or absence of the general relativistic
limit , solutions are classified into general relativistic (GR)
and non-GR branches, respectively, where is the Gauss-Bonnet coupling
constant. We show that a wormhole throat respecting the dominant energy
condition coincides with a branch surface in the GR branch, otherwise the null
energy condition is violated there. In the non-GR branch, it is shown that
there is no wormhole solution for . For the matter field with
zero tangential pressure, it is also shown in the non-GR branch with
and that the dominant energy condition holds at the
wormhole throat if the radius of the throat satisfies some inequality. In the
vacuum case, a fine-tuning of the coupling constants is shown to be necessary
and the radius of a wormhole throat is fixed. Explicit wormhole solutions
respecting the energy conditions in the whole spacetime are obtained in the
vacuum and dust cases with and .Comment: 10 pages, 2 tables; v2, typos corrected, references added; v3,
interpretation of the solution for n=5 in section IV corrected; v4, a very
final version to appear in Physical Review
Strings in five-dimensional anti-de Sitter space with a symmetry
The equation of motion of an extended object in spacetime reduces to an
ordinary differential equation in the presence of symmetry. By properly
defining of the symmetry with notion of cohomogeneity, we discuss the method
for classifying all these extended objects. We carry out the classification for
the strings in the five-dimensional anti-de Sitter space by the effective use
of the local isomorphism between \SO(4,2) and \SU(2,2). We present a
general method for solving the trajectory of the Nambu-Goto string and apply to
a case obtained by the classification, thereby find a new solution which has
properties unique to odd-dimensional anti-de Sitter spaces. The geometry of the
solution is analized and found to be a timelike helicoid-like surface
Counterion Effects on Nano-confined Metal-Drug-DNA Complexes
We have explored morphology of DNA molecules bound with Cu-complexes of
piroxicam molecules, a non-steroidal anti-inflammatory drug (NSAID), under
one-dimensional confinement of thin films and have studied the effect of
counterions present in a buffer. X-ray reflectivity at and away from the Cu K
absorption edge and atomic force microscopy studies reveal that confinement
segregates the drug molecules preferentially in a top layer of the DNA film,
and counterions enhance this segregation
The universe out of a monopole in the laboratory?
To explore the possibility that an inflationary universe can be created out
of a stable particle in the laboratory, we consider the classical and quantum
dynamics of a magnetic monopole in the thin-shell approximation. Classically
there are three types of solutions: stable, collapsing and inflating monopoles.
We argue that the transition from a stable monopole to an inflating one could
occur either by collision with a domain wall or by quantum tunneling.Comment: to appear in Phys. Rev. D with changing title into "Is it possible to
create a universe out of a monopole in the laboratory?", text and figures
revised, 21 pages, 6 figure
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