60,542 research outputs found
Kardar-Parisi-Zhang growth on one-dimensional decreasing substrates
Recent experimental works on one-dimensional (1D) circular
Kardar-Parisi-Zhang (KPZ) systems whose radii decrease in time have reported
controversial conclusions about the statistics of their interfaces. Motivated
by this, we investigate here several 1D KPZ models on substrates whose size
changes in time as , focusing on the case . From
extensive numerical simulations, we show that for there exists a
transient regime in which the statistics is consistent with that of flat KPZ
systems (the case), for both . Actually,
for a given model, and , we observe that a difference between
ingrowing () systems arises only at long
times (), when the expanding surfaces cross over to
the statistics of curved KPZ systems, whereas the shrinking ones become
completely correlated. A generalization of the Family-Vicsek scaling for the
roughness of ingrowing interfaces is presented. Our results demonstrate that a
transient flat statistics is a general feature of systems starting with large
initial sizes, regardless their curvature. This is consistent with their recent
observation in ingrowing turbulent liquid crystal interfaces, but it is in
contrast with the apparent observation of curved statistics in colloidal
deposition at the edge of evaporating drops. A possible explanation for this
last result, as a consequence of the very small number of monolayers analyzed
in this experiment, is given. This is illustrated in a competitive growth model
presenting a few-monolayer transient and an asymptotic behavior consistent,
respectively, with the curved and flat statistics.Comment: 5 pages, 3 figure
Width and extremal height distributions of fluctuating interfaces with window boundary conditions
We present a detailed study of squared local roughness (SLRDs) and local
extremal height distributions (LEHDs), calculated in windows of lateral size
, for interfaces in several universality classes, in substrate dimensions
and . We show that their cumulants follow a Family-Vicsek
type scaling, and, at early times, when ( is the correlation
length), the rescaled SLRDs are given by log-normal distributions, with their
th cumulant scaling as . This give rise to an
interesting temporal scaling for such cumulants , with . This scaling is analytically
proved for the Edwards-Wilkinson (EW) and Random Deposition interfaces, and
numerically confirmed for other classes. In general, it is featured by small
corrections and, thus, it yields exponents 's (and, consequently,
, and ) in nice agreement with their respective universality
class. Thus, it is an useful framework for numerical and experimental
investigations, where it is, usually, hard to estimate the dynamic and
mainly the (global) roughness exponents. The stationary (for ) SLRDs and LEHDs of Kardar-Parisi-Zhang (KPZ) class are also investigated
and, for some models, strong finite-size corrections are found. However, we
demonstrate that good evidences of their universality can be obtained through
successive extrapolations of their cumulant ratios for long times and large
's. We also show that SLRDs and LEHDs are the same for flat and curved KPZ
interfaces.Comment: 11 pages, 10 figures, 4 table
Aproximative solutions to the neutrino oscillation problem in matter
We present approximative solutions to the neutrino evolution equation
calculated by different methods. In a two neutrino framework, using the
physical parameters which gives the main effects to neutrino oscillations from
nu{e} to another flavors for L=3000Km and E=1GeV, the results for the
transition probability calculated by using series solutions, by to take the
neutrino evolution operator as a product of ordered partial operators and by
numerical methods, for a linearly and sinusoidally varying matter density are
compared. The extension to an arbitrary density profile is discussed and the
evolution operator as a product of partial operators in the three neutrino case
is obtained.Comment: 12 pages, 5 figure
Newtonian Perturbations on Models with Matter Creation
Creation of Cold Dark Matter (CCDM) can macroscopically be described by a
negative pressure, and, therefore, the mechanism is capable to accelerate the
Universe, without the need of an additional dark energy component. In this
framework we discuss the evolution of perturbations by considering a
Neo-Newtonian approach where, unlike in the standard Newtonian cosmology, the
fluid pressure is taken into account even in the homogeneous and isotropic
background equations (Lima, Zanchin and Brandenberger, MNRAS {\bf 291}, L1,
1997). The evolution of the density contrast is calculated in the linear
approximation and compared to the one predicted by the CDM model. The
difference between the CCDM and CDM predictions at the perturbative
level is quantified by using three different statistical methods, namely: a
simple -analysis in the relevant space parameter, a Bayesian
statistical inference, and, finally, a Kolmogorov-Smirnov test. We find that
under certain circumstances the CCDM scenario analysed here predicts an overall
dynamics (including Hubble flow and matter fluctuation field) which fully
recovers that of the traditional cosmic concordance model. Our basic conclusion
is that such a reduction of the dark sector provides a viable alternative
description to the accelerating CDM cosmology.Comment: Physical Review D in press, 10 pages, 4 figure
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