42,148 research outputs found
Natural waters in Amazonia. III. Ammonium molybdate-reactive silica
Natural waters of the Amazonian Tertiary formations along the Manaus-Itacoatjara Road were studied with respect to variations in average seasonal and yearly soluble silica content. In general the variations are small and concentrations very low, for all input fractions, i. e., rainfall, stemflow, and throughfall [about 90 percent of the total (470 analyses) lower than 1.0 mg/l]. While 90 percent of total ground water analyses (excluding well IV 3) have soluble silica concentrations lower than 1.5 mg/l, high rain forest stream waters are slightly higher (90 percent of all values lower than 2.0 mg/l). The Rio Negro waters show 90 percent of the total samples analyzed between 2.0 mg/l and 3.0 mg/l soluble silica
Reflection matrices for the vertex model
The graded reflection equation is investigated for the
vertex model. We have found four classes of diagonal
solutions and twelve classes of non-diagonal ones. The number of free
parameters for some solutions depends on the number of bosonic and fermionic
degrees of freedom considered.Comment: 30 page
Compact coalgebras, compact quantum groups and the positive antipode
In this article -that has also the intention to survey some known results in
the theory of compact quantum groups using methods different from the standard
and with a strong algebraic flavor- we consider compact o-coalgebras and Hopf
algebras. In the case of a o-Hopf algebra we present a proof of the
characterization of the compactness in terms of the existence of a positive
definite integral, and use our methods to give an elementary proof of the
uniqueness - up to conjugation by an automorphism of Hopf algebras- of the
compact involution appearing in [4]. We study the basic properties of the
positive square root of the antipode square that is a Hopf algebra automorphism
that we call the positive antipode. We use it -as well as the unitary antipode
and the Nakayama automorphism- in order to enhance our understanding of the
antipode itself
An exterior for the G\"{o}del spacetime
We match the vacuum, stationary, cylindrically symmetric solution of
Einstein's field equations with , in a form recently given by Santos,
as an exterior to an infinite cylinder of dust cut out of a G\"{o}del universe.
There are three cases, depending on the radius of the cylinder. Closed timelike
curves are present in the exteriors of some of the solutions. There is a
considerable similarity between the spacetimes investigated here and those of
van Stockum referring to an infinite cylinder of rotating dust matched to
vacuum, with .Comment: 11 pages, LaTeX 2.09, no figures. Submitted to Classical and Quantum
Gravit
The entropy of the noncommutative acoustic black hole based on generalized uncertainty principle
In this paper we investigate statistical entropy of a 3-dimensional rotating
acoustic black hole based on generalized uncertainty principle. In our results
we obtain an area entropy and a correction term associated with the
noncommutative acoustic black hole when introduced in the generalized
uncertainty principle takes a specific value. However, in this method, it is
not needed to introduce the ultraviolet cut-off and divergences are eliminated.
Moreover, the small mass approximation is not necessary in the original
brick-wall model.Comment: 9 pages, no figures; version to appear in PLB. arXiv admin note:
substantial text overlap with arXiv:1210.773
Lorentz-violating dimension-five operator contribution to the black body radiation
We investigate the thermodynamics of a photon gas in an effective field
theory model that describes Lorentz violations through dimension-five operators
and Horava-Lifshitz theory. We explore the electrodynamics of the model which
includes higher order derivatives in the Lagrangian that can modify the
dispersion relation for the propagation of the photons. We shall focus on the
deformed black body radiation spectrum and modified Stefan-Boltzmann law to
address the allowed bounds on the Lorentz-violating parameter.Comment: 8 pages, 6 figures. Version published in PL
- …