3,218 research outputs found
Duality invariance in Fayet-Iliopoulos gauged supergravity
We propose a geometric method to study the residual symmetries in ,
Fayet-Iliopoulos (FI) gauged supergravity. It essentially
involves the stabilization of the symplectic vector of gauge couplings (FI
parameters) under the action of the U-duality symmetry of the ungauged theory.
In particular we are interested in those transformations that act non-trivially
on the solutions and produce scalar hair and dyonic black holes from a given
seed. We illustrate the procedure for finding this group in general and then
show how it works in some specific models. For the prepotential ,
we use our method to add one more parameter to the rotating Chow-Comp\`ere
solution, representing scalar hair.Comment: 31 pages, uses jheppub.sty. Final version to appear on JHE
Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide
The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for k sub 1 was measured over a temperature range of 263 - 502 K and the data were fitted to an Arrhenuis expression with good linearity
Disinfection of wastewater using ultraviolet radiation
The disadvantages associated with the use of chlorine for disinfection, in conjunction with improvements in ultraviolet radiation disinfection technologies have led to the recent increased use of ultraviolet radiation to provide disinfection of effluents from wastewater treatment plants. The theory of ultraviolet radiation and the engineering design of the ultraviolet disinfection system are discussed in depth.
The operational history and records of two wastewater treatment plants that use ultraviolet radiation for disinfection were analyzed in an attempt to develop correlations on the factors that affect ultraviolet radiation disinfection efficiency and to investigate as to whether disinfection with ultraviolet radiation is a legitimate alternative to disinfection with chlorine. One facility is a tertiary wastewater treatment plant while the other is a secondary facility.
A high level of disinfection was consistently observed at the tertiary case study facility under the range of operating conditions encountered since the ultraviolet radiation system was put on-line in January 1991. The ultraviolet disinfection system at the secondary case study facility in general provided a satisfactory level of disinfection; however, it was subject to poor disinfection efficiencies upon high plant flows.
Based on the performance of the two case study facilities, ultraviolet radiation disinfection systems can be successfully used to disinfect treated wastewater effluents from both secondary and tertiary facilities. Ultraviolet radiation does represent a reliable, safe and practical alternative to disinfection with chlorine
Holomorphic Anomaly in Gauge Theories and Matrix Models
We use the holomorphic anomaly equation to solve the gravitational
corrections to Seiberg-Witten theory and a two-cut matrix model, which is
related by the Dijkgraaf-Vafa conjecture to the topological B-model on a local
Calabi-Yau manifold. In both cases we construct propagators that give a
recursive solution in the genus modulo a holomorphic ambiguity. In the case of
Seiberg-Witten theory the gravitational corrections can be expressed in closed
form as quasimodular functions of Gamma(2). In the matrix model we fix the
holomorphic ambiguity up to genus two. The latter result establishes the
Dijkgraaf-Vafa conjecture at that genus and yields a new method for solving the
matrix model at fixed genus in closed form in terms of generalized
hypergeometric functions.Comment: 34 pages, 2 eps figures, expansion at the monopole point corrected
and interpreted, and references adde
An action principle for the Einstein-Weyl equations
A longstanding open problem in mathematical physics has been that of finding an action principle for the Einstein–Weyl (EW) equations. In this paper, we present for the first time such an action principle in three dimensions in which the Weyl vector is not exact. More precisely, our model contains, in addition to the Weyl nonmetricity, a traceless part. If the latter is (consistently) set to zero, the equations of motion boil down to the EW equations. In particular, we consider a metric affine f(R) gravity action plus additional terms involving Lagrange multipliers and gravitational Chern–Simons contributions. In our framework, the metric and the connection are considered as independent objects, and no a priori assumptions on the nonmetricity and the torsion of the connection are made. The dynamics of the Weyl vector turns out to be governed by a special case of the generalized monopole equation, which represents a conformal self-duality condition in three dimensions
Comment on "c-axis Josephson tunneling in -wave superconductors''
This comment points out that the recent paper by Maki and Haas [Phys. Rev. B
{\bf 67}, 020510 (2003)] is completely wrong.Comment: 1 page, submittted to Phys. Rev.
Does dynamics reflect topology in directed networks?
We present and analyze a topologically induced transition from ordered,
synchronized to disordered dynamics in directed networks of oscillators. The
analysis reveals where in the space of networks this transition occurs and its
underlying mechanisms. If disordered, the dynamics of the units is precisely
determined by the topology of the network and thus characteristic for it. We
develop a method to predict the disordered dynamics from topology. The results
suggest a new route towards understanding how the precise dynamics of the units
of a directed network may encode information about its topology.Comment: 7 pages, 4 figures, Europhysics Letters, accepte
Epidemic threshold in structured scale-free networks
We analyze the spreading of viruses in scale-free networks with high
clustering and degree correlations, as found in the Internet graph. For the
Suscetible-Infected-Susceptible model of epidemics the prevalence undergoes a
phase transition at a finite threshold of the transmission probability.
Comparing with the absence of a finite threshold in networks with purely random
wiring, our result suggests that high clustering and degree correlations
protect scale-free networks against the spreading of viruses. We introduce and
verify a quantitative description of the epidemic threshold based on the
connectivity of the neighborhoods of the hubs.Comment: 4 pages, 4 figure
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