467 research outputs found
Coset Constructions in Chern-Simons Gauge Theory
Coset constructions in the framework of Chern-Simons topological gauge
theories are studied. Two examples are considered: models of the types
with and
coprime integers, and . In the latter
case it is shown that the Chern-Simons wave functionals can be identified with
t he characters of the minimal unitary models, and an explicit representation
of the knot (Verlinde) operators acting on the space of characters is
obtained.Comment: 15 page
Water and energy fluxes from a woodland savanna (cerrado) in southeast Brazil
Study region: The area of woodland savanna (cerrado) is located in southeast Brazil (21°36âČ to 44âČ S, 47°34âČ to 41âČ W).
Study focus: The cerrado sensu-stricto savanna evapotranspiration was observed using the eddy-covariance method over three years.
New hydrological insights for the region: The first year total rainfall (R = 1664 mm) was 11% above the long-term rainfall (1498 mm) and the total evapotranspiration (ET = 1242 mm) and water equivalent of available energy (Av = 1835 mm) were approximately 4% and 2% greater, respectively, than in the second year when the rainfall total was 5% lower than the long-term average. In the third year despite the total rainfall (1259 mm) being 24% lower than the first year and 16% lower than the average, the totals of ET (1242 mm) and Av (1815 mm) were approximately the same.
The small variation in the observed annual ET totals shows that in this cerrado vegetation the deep soil moisture content supports the ET in a dry year and the water available for recharging the soil profile and groundwater (âŒR â ET) was dominated by the rainfall amount being significantly greater in the wet year (422 mm) than in the dry year (13 mm)
Exact scaling in the expansion-modification system
This work is devoted to the study of the scaling, and the consequent
power-law behavior, of the correlation function in a mutation-replication model
known as the expansion-modification system. The latter is a biology inspired
random substitution model for the genome evolution, which is defined on a
binary alphabet and depends on a parameter interpreted as a \emph{mutation
probability}. We prove that the time-evolution of this system is such that any
initial measure converges towards a unique stationary one exhibiting decay of
correlations not slower than a power-law. We then prove, for a significant
range of mutation probabilities, that the decay of correlations indeed follows
a power-law with scaling exponent smoothly depending on the mutation
probability. Finally we put forward an argument which allows us to give a
closed expression for the corresponding scaling exponent for all the values of
the mutation probability. Such a scaling exponent turns out to be a piecewise
smooth function of the parameter.Comment: 22 pages, 2 figure
Polynomials for Torus Links from Chern-Simons Gauge Theories
Invariant polynomials for torus links are obtained in the framework of the
Chern-Simons topological gauge theory. The polynomials are computed as vacuum
expectation values on the three-sphere of Wilson line operators representing
the Verlinde algebra of the corresponding rational conformal field theory. In
the case of the gauge theory our results provide explicit expressions
for the Jones polynomial as well as for the polynomials associated to the
-state () vertex models (Akutsu-Wadati polynomials). By means of the
Chern-Simons coset construction, the minimal unitary models are analyzed,
showing that the corresponding link invariants factorize into two
polynomials. A method to obtain skein rules from the Chern-Simons knot
operators is developed. This procedure yields the eigenvalues of the braiding
matrix of the corresponding conformal field theory.Comment: 50 page
Higher dimensional inhomogeneous dust collapse and cosmic censorship
We investigate the occurrence and nature of a naked singularity in the
gravitational collapse of an inhomogeneous dust cloud described by higher
dimensional Tolman-Bondi space-times. The naked singularities are found to be
gravitationally strong in the sense of Tipler. Higher dimensions seem to favour
black holes rather than naked singularities.Comment: 15 pages, LaTeX, 1 figure, 2 table
Dimensional Dependence of Black Hole Formation in Self-Similar Collapse of Scalar Field
We study classical and quantum self-similar collapses of a massless scalar
field in higher dimensions, and examine how the increase in the number of
dimensions affects gravitational collapse and black hole formation. Higher
dimensions seem to favor formation of black hole rather than other final
states, in that the initial data space for black hole formation enlarges as
dimension increases. On the other hand, the quantum gravity effect on the
collapse lessens as dimension increases. We also discuss the gravitational
collapse in a brane world with large but compact extra dimensions.Comment: Improved a few arguments and added a figur
Stone-stacking as a looming threat to rock-dwelling biodiversity
Non peer reviewe
Growth inhibitory effects of 3âČ-nitro-3-phenylamino nor-beta-lapachone against HL-60: A redox-dependent mechanism
AbstractIn this study, the cytotoxicity, genotoxicity and early ROS generation of 2,2-dimethyl-(3H)-3-(N-3âČ-nitrophenylamino)naphtho[1,2-b]furan-4,5-dione (QPhNO2) were investigated and compared with those of its precursor, nor-beta-lapachone (nor-beta), with the main goal of proposing a mechanism of antitumor action. The results were correlated with those obtained from electrochemical experiments held in protic (acetate buffer pH 4.5) and aprotic (DMF/TBABF4) media in the presence and absence of oxygen and with those from dsDNA biosensors and ssDNA in solution, which provided evidence of a positive interaction with DNA in the case of QPhNO2. QPhNO2 caused DNA fragmentation and mitochondrial depolarization and induced apoptosis/necrosis in HL-60 cells. Pre-treatment with N-acetyl-l-cysteine partially abolished the observed effects related to the QPhNO2 treatment, including those involving apoptosis induction, indicating a partially redox-dependent mechanism. These findings point to the potential use of the combination of pharmacology and electrochemistry in medicinal chemistry
Higher dimensional dust collapse with a cosmological constant
The general solution of the Einstein equation for higher dimensional (HD)
spherically symmetric collapse of inhomogeneous dust in presence of a
cosmological term, i.e., exact interior solutions of the Einstein field
equations is presented for the HD Tolman-Bondi metrics imbedded in a de Sitter
background. The solution is then matched to exterior HD Scwarschild-de Sitter.
A brief discussion on the causal structure singularities and horizons is
provided. It turns out that the collapse proceed in the same way as in the
Minkowski background, i.e., the strong curvature naked singularities form and
that the higher dimensions seem to favor black holes rather than naked
singularities.Comment: 7 Pages, no figure
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
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