26,396 research outputs found
Anisotropic KPZ growth in 2+1 dimensions: fluctuations and covariance structure
In [arXiv:0804.3035] we studied an interacting particle system which can be
also interpreted as a stochastic growth model. This model belongs to the
anisotropic KPZ class in 2+1 dimensions. In this paper we present the results
that are relevant from the perspective of stochastic growth models, in
particular: (a) the surface fluctuations are asymptotically Gaussian on a
sqrt(ln(t)) scale and (b) the correlation structure of the surface is
asymptotically given by the massless field.Comment: 13 pages, 4 figure
On the asymmetric zero-range in the rarefaction fan
We consider the one-dimensional asymmetric zero-range process starting from a
step decreasing profile. In the hydrodynamic limit this initial condition leads
to the rarefaction fan of the associated hydrodynamic equation. Under this
initial condition and for totally asymmetric jumps, we show that the weighted
sum of joint probabilities for second class particles sharing the same site is
convergent and we compute its limit. For partially asymmetric jumps we derive
the Law of Large Numbers for the position of a second class particle under the
initial configuration in which all the positive sites are empty, all the
negative sites are occupied with infinitely many first class particles and with
a single second class particle at the origin. Moreover, we prove that among the
infinite characteristics emanating from the position of the second class
particle, this particle chooses randomly one of them. The randomness is given
in terms of the weak solution of the hydrodynamic equation through some sort of
renormalization function. By coupling the zero-range with the exclusion process
we derive some limiting laws for more general initial conditions.Comment: 22 pages, to appear in Journal of Statistical Physic
A model for multifragmentation in heavy-ion reactions
From an experimental point of view, clear signatures of multifragmentation
have been detected by different experiments. On the other hand, from a
theoretical point of view, many different models, built on the basis of totally
different and often even contrasting assumptions, have been provided to explain
them. In this contribution we show the capabilities and the shortcomings of one
of this models, a QMD code developed by us and coupled to the nuclear
de-excitation module taken from the multipurpose transport and interaction code
FLUKA, in reproducing the multifragmentation observations recently reported by
the INDRA collaboration for the reaction Nb + Mg at a 30 MeV/A projectile
bombarding energy. As far as fragment production is concerned, we also briefly
discuss the isoscaling technique by considering reactions characterized by a
different isospin asymmetry, and we explain how the QMD + FLUKA model can be
applied to obtain information on the slope of isotopic yield ratios, which is
crucially related to the symmetry energy of asymmetric nuclear matter.Comment: 8 pages, 2 figures, Proc. 12th International Conference on Nuclear
Reaction Mechanisms, Varenna, Italy, June 15 - 19 200
Geometry of contours and Peierls estimates in d=1 Ising models
Following Fr\"ohlich and Spencer, we study one dimensional Ising spin systems
with ferromagnetic, long range interactions which decay as ,
. We introduce a geometric description of the spin
configurations in terms of triangles which play the role of contours and for
which we establish Peierls bounds. This in particular yields a direct proof of
the well known result by Dyson about phase transitions at low temperatures.Comment: 28 pages, 3 figure
Model checking usage policies
We study usage automata, a formal model for specifying policies on the usage of resources. Usage automata extend finite state automata with some additional features, parameters and guards, that improve their expressivity. We show that usage automata are expressive enough to model policies of real-world applications. We discuss their expressive power, and we prove that the problem of telling whether a computation complies with a usage policy is decidable. The main contribution of this paper is a model checking technique for usage automata. The model is that of usages, i.e. basic processes that describe the possible patterns of resource access and creation. In spite of the model having infinite states, because of recursion and resource creation, we devise a polynomial-time model checking technique for deciding when a usage complies with a usage policy
Beneficiamento e armazenamento de sementes de algumas espécies de pinus.
bitstream/item/42002/1/CT0069.pd
Consumersâ Attitudes on Services of General Interest in the EU: Accessibility, Price and Quality 2000-2004
The research question addressed by this paper is a simple one: are European consumers happy with the services provided by the utilities after two decades of reforms? We focus on electricity, gas, water, telephone in the EU 15 Member States. The variables we analyse are consumersâ satisfaction with accessibility, price and quality, as reported in three waves of Eurobarometer survey, 2000-2002-2004, comprising around 47,000 observations. We use ordered logit models to analyze the impact of privatization and regulatory reforms, as represented by an OECD dataset, controlling for individual and country characteristics. Our results do not support a clear association between consumersâ satisfaction and a standard reform package of privatization, vertical disintegration, liberalization.Consumersâ Satisfaction, Gas, Electricity, Telephone, Water, Eurobarometer
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