16 research outputs found
Energy in Topologically Massive Gravity
We define conserved gravitational charges in -cosmologically extended-
topologically massive gravity, exhibit them in surface integral form about
their de-Sitter or flat vacua and verify their correctness in terms of two
basic types of solution.Comment: 6 page
Modeling multidimensional effects in the propagation of radiative shocks
Radiative shocks (also called supercritical shocks) are high Mach number shock waves that photoionize the medium ahead of the shock front and give rise to a radiative precursor. They are generated in the laboratory using high-energy or high-power lasers and are frequently present in a wide range of astronomical objects. Their modelisation in one dimension has been the subject of numerous studies, but generalization to three dimensions is not straightforward. We calculate analyticaly the absorption of radiation in a grey uniform cylinder and show how it decreases with , the product of the opacity and of the cylinder radius . Simple formulas, whose validity range increases when diminishes, are derived for the radiation field on the axis of symmetry. Numerical calculations in three dimensions of the radiative energy density, flux and pressure created by a stationary shock wave show how the radiation decreases whith . Finally, the bidimensional structures of both the precursor and the radiation field are calculated with time-dependent radiation hydrodynamics numerical simulations and the influence of two-dimensional effects on the electron density, the temperature, the shock velocity and the shock geometry are exhibited. These simulations show how the radiative precursor shortens, cools and slows down when is decreased
The black holes of topologically massive gravity
We show that an analytical continuation of the Vuorio solution to
three-dimensional topologically massive gravity leads to a two-parameter family
of black hole solutions, which are geodesically complete and causally regular
within a certain parameter range. No observers can remain static in these
spacetimes. We discuss their global structure, and evaluate their mass, angular
momentum, and entropy, which satisfy a slightly modified form of the first law
of thermodynamics.Comment: 10 pages; Eq. (15) corrected, references added, version to appear in
Classical and Quantum Gravit
Black hole mass and angular momentum in topologically massive gravity
We extend the Abbott-Deser-Tekin approach to the computation of the Killing
charge for a solution of topologically massive gravity (TMG) linearized around
an arbitrary background. This is then applied to evaluate the mass and angular
momentum of black hole solutions of TMG with non-constant curvature
asymptotics. The resulting values, together with the appropriate black hole
entropy, fit nicely into the first law of black hole thermodynamics.Comment: 20 pages, references added, version to appear in Classical and
Quantum Gravit
Non-asymptotically flat, non-AdS dilaton black holes
We show that previously known non-asymptotically flat static black hole
solutions of Einstein-Maxwell-dilaton theory may be obtained as near-horizon
limits of asymptotically flat black holes. Specializing to the case of the
dilaton coupling constant , we generate from the
non-asymptotically flat magnetostatic or electrostatic black holes two classes
of rotating dyonic black hole solutions. The rotating dyonic black holes of the
``magnetic'' class are dimensional reductions of the five-dimensional
Myers-Perry black holes relative to one of the azimuthal angles, while those of
the ``electric'' class are twisted dimensional reductions of rotating dyonic
Rasheed black strings. We compute the quasi-local mass and angular momentum of
our rotating dyonic black holes, and show that they satisfy the first law of
black hole thermodynamics, as well as a generalized Smarr formula. We also
discuss the construction of non-asymptotically flat multi-extreme black hole
configurations.Comment: Minor corrections. 2 references added. To appear in Physical Review
Jump conditions in hypersonic shocks
We study the quantitative effects of excitation, ionization,
radiation energy and pressure, on the jump conditions in hypersonic shocks in a
real gas. The ionization structure and excitation energies are calculated from
the local temperature and density, using the Screened Hydrogenic Model. We
assume an optically thick medium and no radiation flux through the shock front.
We investigate the jump conditions in different gases and propose a
phenomenological description of compression for different shock velocities. We
find that the excitation energy term is the dominant term in ionized gases at
low velocities. Consequently, higher shock velocities than the values predicted
by standard calculations in a perfect gas must be reached in order to observe
the effects of radiation in the compression ratio. Our results provide
constraints for the design of future radiative shock experiments on the next
generation of powerful nanosecond lasers or on Z-pinches
Quantitative effects of ionic excitation and radiation
Abstract. We study the quantitative effects of excitation, ionization, radiation energy and pressure, on the jump conditions in hypersonic shocks in a real gas. The ionization structure and excitation energies are calculated from the local temperature and density, using the Screened Hydrogenic Model. We assume an optically thick medium and no radiation flux through the shock front. We investigate the jump conditions in different gases and propose a phenomenological description of compression for different shock velocities. We find that the excitation energy term is the dominant term in ionized gases at low velocities. Consequently, higher shock velocities than the values predicted by standard calculations in a perfect gas must be reached in order to observe the effects of radiation in the compression ratio. Our results provide constraints for the design of future radiative shock experiments on the next generation of powerful nanosecond lasers or on Z-pinches. PACS. 52.35.Tc Shock waves and discontinuities – 95.30.Dr Atomic processes and interactions
Radiative Shocks in the Context of Young Stellar Objects: A Combined Analysis from Experiments and Simulations
Radiative Shock Experiments At Luli
International audienceWe present the set-up and the results of a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using specific designed targets filled with xenon gaz at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured quantities related to the shock (electronic density, propagation velocities, temperature, radial dimension) are presented and compared with various numerical simulations