23,771 research outputs found
Mimetic gravity: mimicking the dynamics of the primeval universe in the context of loop quantum cosmology
Mimetic gravity can be described as a formulation capable of mimicking
different evolutionary scenarios regarding the universe dynamics.
Notwithstanding its initial aim of producing a similar evolution to the one
expected from the dark components of the standard cosmology, a recent
association with loop quantum cosmology could also provide interesting results.
In this work, we reinterpret the physics behind the curvature potential of
mimetic gravity description of loop quantum cosmology. Furthermore, we also
test the compatibility of our formulation for a Higgs-type field, proving that
the mimetic curvature potential can mimic the dynamics from a Higgs
inflationary model. Additionally, we discuss possible scenarios that emerge
from the relationship between matter and mimetic curvature and, within certain
limits, describe results for the primeval universe dynamics obtained by other
authors.Comment: 13 pages, 2 figure
Spin Liquid Behavior in Electronic Griffiths Phases
We examine the interplay of the Kondo effect and the RKKY interactions in
electronic Griffiths phases using extended dynamical mean-field theory methods.
We find that sub-Ohmic dissipation is generated for sufficiently strong
disorder, leading to suppression of Kondo screening on a finite fraction of
spins, and giving rise to universal spin-liquid behavior.Comment: 4 pages, minor changes included, typos correcte
Seed Magnetic Fields Generated by Primordial Supernova Explosions
The origin of the magnetic field in galaxies is an open question in
astrophysics. Several mechanisms have been proposed related, in general, with
the generation of small seed fields amplified by a dynamo mechanism. In
general, these mechanisms have difficulty in satisfying both the requirements
of a sufficiently high strength for the magnetic field and the necessary large
coherent scales. We show that the formation of dense and turbulent shells of
matter, in the multiple explosion scenario of Miranda and Opher (1996, 1997)
for the formation of the large-scale structures of the Universe, can naturally
act as a seed for the generation of a magnetic field. During the collapse and
explosion of Population III objects, a temperature gradient not parallel to a
density gradient can naturally be established, producing a seed magnetic field
through the Biermann battery mechanism. We show that seed magnetic fields can be produced in this multiple explosion scenario on
scales of the order of clusters of galaxies (with coherence length ) and up to on scales of galaxies ().Comment: Accepted for publication in MNRAS, 5 pages (MN plain TeX macros v1.6
file). Also available at http://www.iagusp.usp.br/~oswaldo (click "OPTIONS"
and then "ARTICLES"
THE IMPACT OF POLLUTION CONTROLS ON LIVESTOCK-CROP PRODUCERS
A discrete-time, continuous-space model of a livestock- crop producer is used to examine the long-run effects of phosphorus runoff controls on optimal livestock production and manure application practices. Quantity restrictions and taxes on phosphorus application are shown to reduce livestock supply and impose greater costs on livestock-crop producers than on crop-only producers. Restrictions on manure application, without accompanying restrictions on commercial fertilizer application, will have only a limited effect on phosphorus runoff levels.Environmental Economics and Policy, Farm Management,
- …