2,346 research outputs found
Black Holes and Naked Singularities in Low Energy Limit of String Gravity with Modulus Field
We show that the black hole solutions of the effective string theory action,
where one-loop effects that couple the moduli to gravity via a Gauss-Bonnet
term are taken into account, admit primary scalar hair. The requirement of
absence of naked singularities imposes an upper bound on the scalar charges.Comment: more details are added and some misprint are correcte
The Third Annual William French Smith Memorial Lecture: A Conversation with Retired Justice Sandra Day O\u27Connor
No-scalar hair conjecture in asymptotic de-Sitter spacetime
We discuss the no-hair conjecture in the presence of a cosmological constant.
For the firststep the real scalar field is considered as the matter field and
the spacetime is assumed to be static spherically symmetric. If the scalar
field is massless or has a convex potential such as a mass term, it is proved
that there is no regular black hole solution. For a general positive potential,
we search for black hole solutions which support the scalar field with a double
well potential, and find them by numerical calculations. The existence of such
solutions depends on the values of the vacuum expectation value and the
self-coupling constant of the scalar field. When we take the zero horizon
radius limit, the solution becomes a boson star like solution which we found
before. However new solutions are found to be unstable against the linear
perturbation. As a result we can conclude that the no-scalar hair conjecture
holds in the case of scalar fields with a convex or double well potential.Comment: 9 pages, 2 Postscript figure
Hairs on the cosmological horizon
We investigate the possibility of having hairs on the cosmological horizon.
The cosmological horizon shares similar properties of black hole horizons in
the aspect of having hairs on the horizons. For those theories admitting haired
black hole solutions, the nontrivial matter fields may reach and extend beyond
the cosmological horizon. For Q-stars and boson stars, the matter fields cannot
reach the cosmological horizon. The no short hair conjecture keeps valid,
despite the asymptotic behavior (de Sitter or anti-de Sitter) of black hole
solutions. We prove the no scalar hair theorem for anti-de Sitter black holes.
Using the Bekenstein's identity method, we also prove the no scalar hair
theorem for the de Sitter space and de Sitter black holes if the scalar
potential is convex.Comment: Revtex, no figures, 16 page
Understanding adhesion at as-deposited interfaces from ab initio thermodynamics of deposition growth: thin-film alumina on titanium carbide
We investigate the chemical composition and adhesion of chemical vapour
deposited thin-film alumina on TiC using and extending a recently proposed
nonequilibrium method of ab initio thermodynamics of deposition growth (AIT-DG)
[Rohrer J and Hyldgaard P 2010 Phys. Rev. B 82 045415]. A previous study of
this system [Rohrer J, Ruberto C and Hyldgaard P 2010 J. Phys.: Condens. Matter
22 015004] found that use of equilibrium thermodynamics leads to predictions of
a non-binding TiC/alumina interface, despite the industrial use as a
wear-resistant coating. This discrepancy between equilibrium theory and
experiment is resolved by the AIT-DG method which predicts interfaces with
strong adhesion. The AIT-DG method combines density functional theory
calculations, rate-equation modelling of the pressure evolution of the
deposition environment and thermochemical data. The AIT-DG method was
previously used to predict prevalent terminations of growing or as-deposited
surfaces of binary materials. Here we extent the method to predict surface and
interface compositions of growing or as-deposited thin films on a substrate and
find that inclusion of the nonequilibrium deposition environment has important
implications for the nature of buried interfaces.Comment: 8 pages, 6 figures, submitted to J. Phys.: Condens. Matte
Nuclear Multifragmentation in the Non-extensive Statistics - Canonical Formulation
We apply the canonical quantum statistical model of nuclear
multifragmentation generalized in the framework of recently proposed Tsallis
non-extensive thermostatistics for the description of nuclear
multifragmentation process. The test calculation in the system with A=197
nucleons show strong modification of the 'critical' behaviour associated with
the nuclear liquid-gas phase transition for small deviations from the
conventional Boltzmann-Gibbs statistical mechanics.Comment: 4 pages, 4 figure
- …