59,505 research outputs found
Stochastic Model in the Kardar-Parisi-Zhang Universality With Minimal Finite Size Effects
We introduce a solid on solid lattice model for growth with conditional
evaporation. A measure of finite size effects is obtained by observing the time
invariance of distribution of local height fluctuations. The model parameters
are chosen so that the change in the distribution in time is minimum.
On a one dimensional substrate the results obtained from the model for the
roughness exponent from three different methods are same as predicted
for the Kardar-Parisi-Zhang (KPZ) equation. One of the unique feature of the
model is that the as obtained from the structure factor for
the one dimensional substrate growth exactly matches with the predicted value
of 0.5 within statistical errors. The model can be defined in any dimensions.
We have obtained results for this model on a 2 and 3 dimensional substrates.Comment: 8 pages, 7 figures, accepted in Phys. Rev.
Comment on "Theory and computer simulation for the equation of state of additive hard-disk fluid mixtures"
A flaw in the comparison between two different theoretical equations of state
for a binary mixture of additive hard disks and Monte Carlo results, as
recently reported in C. Barrio and J. R. Solana, Phys. Rev. E 63, 011201
(2001), is pointed out. It is found that both proposals, which require the
equation of state of the single component system as input, lead to comparable
accuracy but the one advocated by us [A. Santos, S. B. Yuste, and M. L\'{o}pez
de Haro, Mol. Phys. 96, 1 (1999)] is simpler and complies with the exact limit
in which the small disks are point particles.Comment: 4 pages, including 1 figur
Optimal Trajectories for Near-Earth-Objects Using Solar Electric Propulsion (SEP) and Gravity Assisted Maneuver
The future interplanetary missions will probably use the conventional chemical rockets to leave the sphere of influence of the Earth, and solar electric propulsion (SEP) to accomplish the other maneuvers of the mission. In this work the optimization of interplanetary missions using solar electric propulsion and Gravity Assisted Maneuver to reduce the costs of the mission, is considered. The high specific impulse of electric propulsion makes a Gravity Assisted Maneuver 1 year after departure convenient. Missions for several Near Earth Asteroids will be considered. The analysis suggests criteria for the definition of initial solutions demanded for the process of optimization of trajectories. Trajectories for the asteroid 2002TC70 are analyzed. Direct trajectories, trajectories with 1 gravity assisted from the Earth and with 2 gravity assisted from the Earth and either Mars are present. An indirect optimization method will be used in the simulations
Ultra-cold bosons in zig-zag optical lattices
Ultra-cold bosons in zig-zag optical lattices present a rich physics due to
the interplay between frustration, induced by lattice geometry, two-body
interaction and three-body constraint. Unconstrained bosons may develop chiral
superfluidity and a Mott-insulator even at vanishingly small interactions.
Bosons with a three-body constraint allow for a Haldane-insulator phase in
non-polar gases, as well as pair-superfluidity and density wave phases for
attractive interactions. These phases may be created and detected within the
current state of the art techniques.Comment: 8 pages, 9 figure
Genetic diversity of Lusitano horse in Brazil using pedigree information
This study aimed to evaluate population parameters and to describe the genetic diversity of the Lusitano
breed in Brazil using pedigree data. Two populations were evaluated: total population (TP) containing
18,922 animals, and reference population (RP) composed of a part of TP containing 8,329 animals, representing
the last generation. The generation interval (10.1 ± 5.1 years) was in the range for horse populations.
Pedigree completeness in RP shows almost 100% filling in the three most recent generations,
indicating improvement in the pedigree data and accuracy of the results, and the inbreeding coefficient
(4.46%) and average relatedness (5.97%) for RP, indicating control on the part of breeders. The effective
population size was 89 (TP) and 90 (RP). The effective number of founders (fe) were 33 and 29, effective
number of ancestors (fa) were 30 and 26, and effective number of founder genomes (fg) were 19 and 15 for
TP and RP, respectively, indicating a reduction of genetic variability in the last generations. The total
number of ancestors that explains 100% of the genetic diversity in the Lusitano breed in Brazil was 427 (TP)
and 341 (RP). The reproductive parameters, probabilities of gene origin showing loss of variability in the
last generations, and the genetic contributions of ancestors suggest the need to monitor genetic diversity
over time in breeding programs to allow control of the next generations and to increase their variability.info:eu-repo/semantics/publishedVersio
Isospin Constraints on the Parametric Coupling Model for Nuclear Matter
We make use of isospin constraints to study the parametric coupling model and
the properties of asymmetric nuclear matter. Besides the usual constraints for
nuclear matter - effective nucleon mass and the incompressibility at saturation
density - and the neutron star constraints - maximum mass and radius - we have
studied the properties related with the symmetry energy. These properties have
constrained to a small range the parameters of the model. We have applied our
results to study the thermodynamic instabilities in the liquid-gas phase
transition as well as the neutron star configurations.Comment: 11 pages, 10 figure
Collective modes in relativistic npe matter at finite temperature
Isospin and density waves in neutral neutron-proton-electron (npe) matter are
studied within a relativistic mean-field hadron model at finite temperature
with the inclusion of the electromagnetic field. The dispersion relation is
calculated and the collective modes are obtained. The unstable modes are
discussed and the spinodals, which separate the stable from the unstable
regions, are shown for different values of the momentum transfer at various
temperatures. The critical temperatures are compared with the ones obtained in
a system without electrons. The largest critical temperature, 12.39 MeV, occurs
for a proton fraction y_p=0.47. For y_p=0.3 we get =5 MeV and for
y_p>0.495 MeV.
It is shown that at finite temperature the distillation effect in asymmetric
matter is not so efficient and that electron effects are particularly important
for small momentum transfers.Comment: 10 pages, 6 figure
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