1,452 research outputs found
Reheating in nonminimal derivative coupling model
We consider a model with nonminimal derivative coupling of inflaton to
gravity. The reheating process during rapid oscillation of the inflaton is
studied and the reheating temperature is obtained. Behaviors of the inflaton
and produced radiation in this era are discussed.Comment: 16 pages, 5 figures; discussions added; accepted by JCA
Gravitational collapse and black hole evolution: do holographic black holes eventually "anti-evaporate"?
We study the gravitational collapse of compact objects in the Brane-World. We
begin by arguing that the regularity of the five-dimensional geodesics does not
allow the energy-momentum tensor of matter on the brane to have (step-like)
discontinuities, which are instead admitted in the four-dimensional General
Relativistic case, and compact sources must therefore have an atmosphere. Under
the simplifying assumption that matter is a spherically symmetric cloud of dust
without dissipation, we can find the conditions for which the collapsing star
generically ``evaporates'' and approaches the Hawking behavior as the
(apparent) horizon is being formed. Subsequently, the apparent horizon evolves
into the atmosphere and the back-reaction on the brane metric reduces the
evaporation, which continues until the effective energy of the star vanishes.
This occurs at a finite radius, and the star afterwards re-expands and
``anti-evaporates''. We clarify that the Israel junction conditions across the
brane (holographically related to the matter trace anomaly) and the projection
of the Weyl tensor on the brane (holographically interpreted as the quantum
back-reaction on the brane metric) contribute to the total energy as,
respectively, an ``anti-evaporation'' and an ``evaporation'' term. Concluding,
we comment on the possible effects of dissipation and obtain a new stringent
bound for the brane tension.Comment: 18 pages in RevTeX4 style, 11 eps figures included. Discussion on the
contribution of dissipation and clarifications added, version accepted for
publication in Prog. Theor. Phys. Vol. 114, No.
On the Covariant Galileon and a consistent self-accelerating Universe
In this paper we show that the flat space Galilean theories with up to three
scalars in the equation of motion (the quartic Galileons) are recovered in the
decoupling limit of certain scalar theories non-minimally coupled to gravity,
the so-called "Slotheonic" theories. These theories are also invariant under
the generalized Galilean shifts in curved spacetime. While Galilean
self-(derivative)couplings are not explicit in the action, they appear after
integrating out gravity. We then argue that Galilean supersymmetric theories
may only be found in the context of supergravity. Finally, we discuss on the
possibility that Slotheonic theories are the effective four dimensional
theories of consistent DGP-like models with self-accelerating cosmological
solutions. Moreover, we show that the quartic and cubic Galileon in consistent
DGP models cannot be decoupled.Comment: v3: clarifications added; version accepted for publication in PR
A New Class of Four-Dimensional N=1 Supergravity with Non-minimal Derivative Couplings
In the N=1 four-dimensional new-minimal supergravity framework, we
supersymmetrise the coupling of the scalar kinetic term to the Einstein tensor.
This coupling, although introduces a non-minimal derivative interaction of
curvature to matter, it does not introduce harmful higher-derivatives. For this
construction, we employ off-shell chiral and real linear multiplets. Physical
scalars are accommodated in the chiral multiplet whereas curvature resides in a
linear one.Comment: 18 pages, version published at JHE
Screening Brazilian Macrophomina phaseolina isolates for alkaline lipases and other extracellular hydrolases
Macrophomina phaseolina, phylum Ascomycota, is a phytopathogenic fungus distributed worldwide in hot dry areas. There are few studies on its secreted lipases and none on its colony radial growth rate, an indicator of fungal ability to use nutrients for growth, on media other than potato-dextrose agar. In this study, 13 M. phaseolina isolates collected in different Brazilian regions were screened for fast-growth and the production of hydrolases of industrial interest, especially alkaline lipases. Hydrolase detection and growth rate determination were done on citric pectin, gelatin, casein, soluble starch, and olive oil as substrates. Ten isolates were found to be active on all substrates tested. The most commonly detected enzymes were pectinases, amylases, and lipases. The growth rate on pectin was significantly higher (P < 0.05), while the growth rates on the different media identified CMM 2105, CMM 1091, and PEL as the fastest-growing isolates. The lipase activity of four isolates grown on olive oil was followed for 4 days by measuring the activity in the cultivation broth. The specific lipolytic activity of isolate PEL was significantly higher at 96 h (130 mU mg protein–1). The broth was active at 37 °C, pH 8, indicating the potential utility of the lipases of this isolate in mild alkaline detergents. There was a strong and positive correlation (0.86) between radial growth rate and specific lipolytic activity. [Int Microbiol 2012; 15(1):1-7
Criminal Sanctions for Agricultural Violations of the Clean Water Act
Public enforcement of the Clean Water Act (CWA) has been characterized by the increased use of criminal sanctions over the past decade. This sanctioning trend has developed in direct response to the passage of the Sentencing Reform Act (SRA) as part of the Comprehensive Crime Control Act of 1984. New sentencing guidelines were established in 1987 under which courts were required to impose sentences which reflect the seriousness of the offense, provide just punishment for the offense, and afford adequate deterrence to criminal conduct. Legal trends are documented for both industrial and agricultural violations as a result of applying the new federal sentencing guidelines to CWA cases. The efficiency implications of the SRA are evaluated in the context of a model of the public enforcement of environmental law. It is concluded that fault-based standards of liability and the use of mixed fine/incarceration sanctions are appropriate for agricultural violations of the CWA.Elsevier - Paper presented at the 43rd Annual Conference of the Western Social Science Association - Reno (Nevada) 18 to 21 April 200
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