144 research outputs found
The water supercooled regime as described by four common water models
The temperature scale of simple water models in general does not coincide
with the natural one. Therefore, in order to make a meaningful evaluation of
different water models a temperature rescaling is necessary. In this paper we
introduce a rescaling using the melting temperature and the temperature
corresponding to the maximum of the heat capacity to evaluate four common water
models (TIP4P-Ew, TIP4P-2005, TIP5P-Ew and Six-Sites) in the supercooled
regime. Although all the models show the same general qualitative behavior, the
TIP5P-Ew appears as the best representation of the supercooled regime when the
rescaled temperature is used. We also analyze, using thermodynamic arguments,
the critical nucleus size for ice growth. Finally, we speculate on the possible
reasons why atomistic models do not usually crystalize while the coarse grained
mW model do crystallize.Comment: 8 pages, 8 figure
El "Horizonte Brocherense" del Valle de San Alberto, Córdoba, Argentina : Consideraciones taxonómicas e implicancias bioestratigráficas
En 1942 Castellanos formalizó el horizonte "Brocherense" sobre una particular asociación de mamÃferos fósiles hallados por él en el Valle de San Alberto (localidades de Villa Cura Brochero y Nono, provincia de Córdoba), compuesta por Nonotherium henningi Castellanos, Paedotherium brocherense Castellanos y Nopachthus coagmentatus Ameghino. En dicha asociación, Castellanos incluyó otros taxones provenientes de Córdoba, Paraglyptodon cordubensis Ameghino y Propanochthus bullifer Burmeister, aunque carecen de procedencia estratigráfica y geográfica precisa. Esta composición paleofaunÃstica llevó a Castellanos a ubicarla temporalmente entre el Chapadmalalense (Plioceno tardÃo basal) y el Ensenadense (Pleistoceno temprano-medio). Posteriormente, la presencia de Nopachthus, taxón exclusivo del Montehermosense (Mioceno tardÃo cuspidal?-Plioceno temprano) y la asignación preliminar de Nonotherium henningi a Xotodon, taxón cuyo último registro se presenta en el Chapadmalalense, llevó a postular que dichos sedimentos eran asignables al Plioceno temprano-Plioceno tardÃo basal. Una reevaluación de los materiales colectados por Castellanos permitió reconocer que: 1) Nonotherium es un género válido que si bien posee la forma de los molariformes similar a Xotodon, presenta algunas particularidades, e.g., diastema más extenso, mayor tamaño y extensión de los nasales; 2) los restos preservados de Paedotherium no permiten una asignación especÃfica y 3) Nopachthus coagmentatus es reasignado a Phyctaenophyga sp. ya que los osteodermos presentan en su superficie externa una figura central notablemente convexa, a diferencia de los osteodermos de Nopachthus, en los que esta figura es plana o muy suavemente convexa. Esta nueva asociación es correlacionable también con el Huayqueriense (Mioceno tardÃo) dadas las distribuciones temporales hoy reconocidas para estos taxones: Paedotherium del Chasiquense (Mioceno tardÃo basal) al Marplatense- Ensenadense? (Plioceno tardÃo-Pleistoceno temprano a medio), Phyctaenophyga sp. Huayqueriense y Nonotherium exclusivo del "Brocherense". Por ello, se postula que el "horizonte Brocherense" también incluirÃa el Mioceno tardÃo, aunque restan confirmaciones mediante estudios faunÃsticos, de paleomagnetismo y dataciones radiométricas.Sesiones libresFacultad de Ciencias Naturales y Muse
From mitochondria to healthy aging: The role of branched-chain amino acids treatment: MATeR a randomized study
How large is "large " for Nuclear matter?
We argue that a so far neglected dimensionless scale, the number of neighbors
in a closely packed system, is relevant for the convergence of the large
expansion at high chemical potential. It is only when the number of colors is
large w.r.t. this new scale (\sim \order{10}) that a convergent large
limit is reached. This provides an explanation as to why the large
expansion, qualitatively successful in in vacuum QCD, fails to describe high
baryo-chemical potential systems, such as nuclear matter. It also means that
phenomenological claims about high density matter based on large
extrapolations should be treated with caution.Comment: Proceedings of CPOD2010 conference, in Dubna. Results based on
Phys.Rev.C82, 055202 (2010), http://arxiv.org/abs/1006.247
Anomalous vacuum energy and stability of a quantum liquid
KT is grateful to EPSRC and V V Brazhkin to RSF 14-22-
00093 for support
Phase diagrams in nonlocal PNJL models constrained by Lattice QCD results
Based on lattice QCD-adjusted SU(2) nonlocal Polyakov--Nambu--Jona-Lasinio
(PNJL) models, we investigate how the location of the critical endpoint in the
QCD phase diagram depends on the strenght of the vector meson coupling, as well
as the Polyakov-loop (PL) potential and the form factors of the covariant
model. The latter are constrained by lattice QCD data for the quark propagator.
The strength of the vector coupling is adjusted such as to reproduce the slope
of the pseudocritical temperature for the chiral phase transition at low
chemical potential extracted recently from lattice QCD simulations. Our study
supports the existence of a critical endpoint in the QCD phase diagram albeit
the constraint for the vector coupling shifts its location to lower
temperatures and higher baryochemical potentials than in the case without it.Comment: 23 pages, 10 figures. Version accepted in Phys. Part. Nucl. Lett. (to
appear), references adde
Chiral Modulations in Curved Space II: Conifold Geometries
In this paper, we extend our previous analysis concerning the formation of
inhomogeneous condensates in strongly-coupled fermion effective field theories
on curved spaces and include the case of conifold geometries that represent the
simplest tractable case of manifolds with curvature singularities. In the
set-up considered here, by keeping the genuine thermodynamical temperature
constant, we may single out the role that curvature effects play on the
breaking/restoration of chiral symmetry and on the appearance of inhomogeneous
phases. The first goal of this paper is to construct a general expression of
the finite temperature effective action for inhomogeneous condensates in the
case of four-fermion effective field theories on conifold geometries with
generic Riemannian smooth base (generalised cones). The other goal is to
implement numerically the above formal results and construct self-consistent
solutions for the condensate. We explicitly show that the condensate assumes a
kink-like profile, vanishing at the singularity that is surrounded by a bubble
of restored chiral symmetry phase.Comment: 14 pages; 4 figure
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