2,378 research outputs found
Thermodynamics of noncommutative quantum Kerr black holes
Thermodynamic formalism for rotating black holes, characterized by
noncommutative and quantum corrections, is constructed. From a fundamental
thermodynamic relation, equations of state and thermodynamic response functions
are explicitly given and the effect of noncommutativity and quantum correction
is discussed. It is shown that the well known divergence exhibited in specific
heat is not removed by any of these corrections. However, regions of
thermodynamic stability are affected by noncommutativity, increasing the
available states for which some thermodynamic stability conditions are
satisfied.Comment: 16 pages, 9 figure
Wormholes as Basis for the Hilbert Space in Lorentzian Gravity
We carry out to completion the quantization of a Friedmann-Robertson-Walker
model provided with a conformal scalar field, and of a Kantowski-Sachs
spacetime minimally coupled to a massless scalar field. We prove that the
Hilbert space determined by the reality conditions that correspond to
Lorentzian gravity admits a basis of wormhole wave functions. This result
implies that the vector space spanned by the quantum wormholes can be equipped
with an unique inner product by demanding an adequate set of Lorentzian reality
conditions, and that the Hilbert space of wormholes obtained in this way can be
identified with the whole Hilbert space of physical states for Lorentzian
gravity. In particular, all the normalizable quantum states can then be
interpreted as superpositions of wormholes. For each of the models considered
here, we finally show that the physical Hilbert space is separable by
constructing a discrete orthonormal basis of wormhole solutions.Comment: 23 pages (Latex), Preprint IMAFF-RC-04-94, CGPG-94/5-
Thiemann transform for gravity with matter fields
The generalised Wick transform discovered by Thiemann provides a
well-established relation between the Euclidean and Lorentzian theories of
general relativity. We extend this Thiemann transform to the Ashtekar
formulation for gravity coupled with spin-1/2 fermions, a non-Abelian
Yang-Mills field, and a scalar field. It is proved that, on functions of the
gravitational and matter phase space variables, the Thiemann transform is
equivalent to the composition of an inverse Wick rotation and a constant
complex scale transformation of all fields. This result holds as well for
functions that depend on the shift vector, the lapse function, and the Lagrange
multipliers of the Yang-Mills and gravitational Gauss constraints, provided
that the Wick rotation is implemented by means of an analytic continuation of
the lapse. In this way, the Thiemann transform is furnished with a geometric
interpretation. Finally, we confirm the expectation that the generator of the
Thiemann transform can be determined just from the spin of the fields and give
a simple explanation for this fact.Comment: LaTeX 2.09, 14 pages, no figure
Asymptotically anti-de Sitter wormholes
Starting with a procedure for dealing with general asymptotic behaviors, we
construct a quantum theory for asymptotically anti-de Sitter wormholes. We
follow both the path integral formalism and the algebraic quantization program
proposed by Ashtekar. By adding suitable surface terms, the Euclidean action of
the asymptoically anti-de Sitter wormholes can be seen to be finite and gauge
invariant. This action determines an appropriate variational problem for
wormholes. We also obtain the wormhole wave functions of the gravitational
model and show that all the physical states of the quantum theory are
superpositions of wormhole states.Comment: 10 pages, RevTeX 3.0, LaTeX 2.0
Inhomogeneous Loop Quantum Cosmology: Hybrid Quantization of the Gowdy Model
The Gowdy cosmologies provide a suitable arena to further develop Loop
Quantum Cosmology, allowing the presence of inhomogeneities. For the particular
case of Gowdy spacetimes with the spatial topology of a three-torus and a
content of linearly polarized gravitational waves, we detail a hybrid quantum
theory in which we combine a loop quantization of the degrees of freedom that
parametrize the subfamily of homogeneous solutions, which represent Bianchi I
spacetimes, and a Fock quantization of the inhomogeneities. Two different
theories are constructed and compared, corresponding to two different schemes
for the quantization of the Bianchi I model within the {\sl improved dynamics}
formalism of Loop Quantum Cosmology. One of these schemes has been recently put
forward by Ashtekar and Wilson-Ewing. We address several issues including the
quantum resolution of the cosmological singularity, the structure of the
superselection sectors in the quantum system, or the construction of the
Hilbert space of physical states.Comment: 16 pages, version accepted for publication in Physical Review
Engineering a catabolic pathway in plants for the degradation of 1,2-dichloroethane
Plants are increasingly being employed to clean up environmental pollutants such as heavy metals; however, a major limitation of phytoremediation is the inability of plants to mineralize most organic pollutants. A key component of organic pollutants is halogenated aliphatic compounds that include 1,2-dichloroethane (1,2-DCA). Although plants lack the enzymatic activity required to metabolize this compound, two bacterial enzymes, haloalkane dehalogenase (DhlA) and haloacid dehalogenase (DhlB) from the bacterium Xanthobacter autotrophicus GJ10, have the ability to dehalogenate a range of halogenated aliphatics, including 1,2-DCA. We have engineered the dhlA and dhlB genes into tobacco (Nicotiana tabacum ‘Xanthi’) plants and used 1,2-DCA as a model substrate to demonstrate the ability of the transgenic tobacco to remediate a range of halogenated, aliphatic hydrocarbons. DhlA converts 1,2-DCA to 2-chloroethanol, which is then metabolized to the phytotoxic 2-chloroacetaldehyde, then chloroacetic acid, by endogenous plant alcohol dehydrogenase and aldehyde dehydrogenase activities, respectively. Chloroacetic acid is dehalogenated by DhlB to produce the glyoxylate cycle intermediate glycolate. Plants expressing only DhlA produced phytotoxic levels of chlorinated intermediates and died, while plants expressing DhlA together with DhlB thrived at levels of 1,2-DCA that were toxic to DhlA-expressing plants. This represents a significant advance in the development of a low-cost phytoremediation approach toward the clean-up of halogenated organic pollutants from contaminated soil and groundwater
Comparison of aromatic composition of an endangered variety ('Albilla Dorada') with other recognized aromatic varieties
'Albilla Dorada' is a local and endangered grape variety. It was correctly identified beforehand by analysing six microsatellite regions recommended by the GENRES 081 project plus six other additional regions, resulting in one new genotype not described for any variety according to the literature consulted. The object of this paper is to characterize the aromatic composition of this grape vine genotype not previously described. The minority volatile compounds in the grapes were analysed by gas chromatography-mass spectroscopy (GC-MS) and compared with those of eight known aromatic cultivars: 'Albillo Real', 'Macabeo', 'Malvasía Aromática', 'Gewürztraminer', 'Viognier', 'Malvasía Riojana', 'Riesling' and 'Moscatel de Grano Menudo'. Statistically significant differences between varieties were found as regards the different fractions making up the aromatic composition. 'Albilla Dorada' differed from the rest in that it had higher proportions of alcohols, benzene alcohols and norisoprenoids. In the case of the terpene fraction, it was the variety with the highest proportions of citronellol and terpene hydroxides. Results of this work point out 'Albilla Dorada' is a variety with a singular aromatic identity and highlight the necessity of recovering it before its total disappearance.
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