31 research outputs found
Two-dimensional Quantum-Corrected Eternal Black Hole
The one-loop quantum corrections to geometry and thermodynamics of black hole
are studied for the two-dimensional RST model. We chose boundary conditions
corresponding to the eternal black hole being in the thermal equilibrium with
the Hawking radiation. The equations of motion are exactly integrated. The one
of the solutions obtained is the constant curvature space-time with dilaton
being a constant function. Such a solution is absent in the classical theory.
On the other hand, we derive the quantum-corrected metric (\ref{solution})
written in the Schwarzschild like form which is a deformation of the classical
black hole solution \cite{5d}. The space-time singularity occurs to be milder
than in classics and the solution admits two asymptotically flat black hole
space-times lying at "different sides" of the singularity. The thermodynamics
of the classical black hole and its quantum counterpart is formulated. The
thermodynamical quantities (energy, temperature, entropy) are calculated and
occur to be the same for both the classical and quantum-corrected black holes.
So, no quantum corrections to thermodynamics are observed. The possible
relevance of the results obtained to the four-dimensional case is discussed.Comment: Latex, 28 pges; minor corrections in text and abstract made and new
references adde
On the Crustal Matter of Magnetars
We have investigated some of the properties of dense sub-nuclear matter at
the crustal region (both the outer crust and the inner crust region) of a
magnetar. The relativistic version of Thomas-Fermi (TF) model is used in
presence of strong quantizing magnetic field for the outer crust matter. The
compressed matter in the outer crust, which is a crystal of metallic iron, is
replaced by a regular array of spherically symmetric Wigner-Seitz (WS) cells.
In the inner crust region, a mixture of iron and heavier neutron rich nuclei
along with electrons and free neutrons has been considered. Conventional
Harrison-Wheeler (HW) and Bethe-Baym-Pethick (BBP) equation of states are used
for the nuclear mass formula. A lot of significant changes in the
characteristic properties of dense crustal matter, both at the outer crust and
the inner crust, have been observed.Comment: 29 pages REVTEX manuscript, 15 .eps figures (included
The Upper Limit of Magnetic Field Strength in Dense Stellar Hadronic Matter
It is shown that in strongly magnetized neutron stars, there exist upper
limits of magnetic field strength, beyond which the self energies for both
neutron and proton components of neutron star matter become complex in nature.
As a consequence they decay within the strong interaction time scale. However,
in the ultra-strong magnetic field case, when the zeroth Landau level is only
occupied by protons, the system again becomes stable against strong decay.Comment: 6 pages Revtex, 2 .eps figures, fig.(1) is not include
Dilaton gravity approach to three dimensional Lifshitz black hole
The z=3 Lifshitz black hole is an exact black hole solution to the new
massive gravity in three dimensions. In order to understand this black hole
clearly, we perform a dimensional reduction to two dimensional dilaton gravity
by utilizing the circular symmetry. Considering the linear dilaton, we find the
same Lifshitz black hole in two dimensions. This implies that all thermodynamic
quantities of the z=3 Lifshitz black hole could be obtained from its
corresponding black hole in two dimensions. As a result, we derive the
temperature, mass, heat capacity, Bekesnstein-Hawking entropy, and free energy.Comment: 13 pages, 1 figure, version to appear in EPJ
Conserved Quasilocal Quantities and General Covariant Theories in Two Dimensions
General matterless--theories in 1+1 dimensions include dilaton gravity,
Yang--Mills theory as well as non--Einsteinian gravity with dynamical torsion
and higher power gravity, and even models of spherically symmetric d = 4
General Relativity. Their recent identification as special cases of
'Poisson--sigma--models' with simple general solution in an arbitrary gauge,
allows a comprehensive discussion of the relation between the known absolutely
conserved quantities in all those cases and Noether charges, resp. notions of
quasilocal 'energy--momentum'. In contrast to Noether like quantities,
quasilocal energy definitions require some sort of 'asymptotics' to allow an
interpretation as a (gauge--independent) observable. Dilaton gravitation,
although a little different in detail, shares this property with the other
cases. We also present a simple generalization of the absolute conservation law
for the case of interactions with matter of any type.Comment: 21 pages, LaTeX-fil
An action for the exact string black hole
A local action is constructed describing the exact string black hole
discovered by Dijkgraaf, Verlinde and Verlinde in 1992. It turns out to be a
special 2D Maxwell-dilaton gravity theory, linear in curvature and field
strength. Two constants of motion exist: mass M>1, determined by the level k,
and U(1)-charge Q>0, determined by the value of the dilaton at the origin. ADM
mass, Hawking temperature T_H \propto \sqrt{1-1/M} and Bekenstein-Hawking
entropy are derived and studied in detail. Winding/momentum mode duality
implies the existence of a similar action, arising from a branch ambiguity,
which describes the exact string naked singularity. In the strong coupling
limit the solution dual to AdS_2 is found to be the 5D Schwarzschild black
hole. Some applications to black hole thermodynamics and 2D string theory are
discussed and generalizations - supersymmetric extension, coupling to matter
and critical collapse, quantization - are pointed out.Comment: 41 pages, 2 eps figures, dedicated to Wolfgang Kummer on occasion of
his Emeritierung; v2: added ref; v3: extended discussion in sections 3.2, 3.3
and at the end of 5.3 by adding 2 pages of clarifying text; updated refs;
corrected typo
Estimation of accumulated soil organic carbon stock in tropical forest using geospatial strategy
Soil organic carbon (SOC) is a dynamic soil property that represents the key component of the forest ecosystems. The main objective of the present study is to evaluate SOC using the remote sensing images as well as field methods at Ranthambhore Tiger Reserve Forest area. The soil samples were collected randomly from the region at several field locations, to estimate the surface soil carbon concentrations in the laboratory. The study derived results for bare soil index, NDVI, SOC and relationship of SOC with NDVI using regression analysis, while comparing reference SOC (field measured SOC) and predicted SOC (estimated from satellite image). The remote sensing images were used to predict the precise carbon content associated with organic matter in the soil using NDVI and related equations, to prepare digital soil organic carbon map. The relationship between the NDVI and both reference/predicted SOC is established using the equation to derive the digital SOC for the study area using remote sensing data. The statistical relationship between reference SOC, pH concentrations, and NDVI values were presented against the predicted SOC to provide the variation between each variable