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San Luis, Argentina

The National University of San Luis is a public university in Argentina, with its seat in the city of San Luis, capital of the province of the same name, in the Cuyo region. It was created in 1973, along with the National University of San Juan, split off the National University of Cuyo based in Mendoza. Wikipedia.

The proof of a new extension of a theorem that allows to construct deterministic evolution equations from a set of discrete stochastic evolution equation is developed. The present extension allows to handle evolution equations of dynamical variables that are tensors of any rank. Due that the almost paradigmatic field that uses tensors is relativity, an illustrative example is given and the equations that allows to find the geodesics is derived from a set of discrete stochastic evolution equations. Extension to dynamical variables described by spinor indices or "arbitrary labels" are given.

Jara E.C.,National University of San Luis
Genetic Programming and Evolvable Machines | Year: 2011

Real-world time series have certain properties, such as stationarity, seasonality, linearity, among others, which determine their underlying behaviour. There is a particular class of time series called long-memory processes, characterized by a persistent temporal dependence between distant observations, that is, the time series values depend not only on recent past values but also on observations of much prior time periods. The main purpose of this research is the development, application, and evaluation of a computational intelligence method specifically tailored for long memory time series forecasting, with emphasis on manystep- ahead prediction. The method proposed here is a hybrid combining genetic programming and the fractionally integrated (long-memory) component of autoregressive fractionally integrated moving average (ARFIMA) models. Another objective of this study is the discovery of useful comprehensible novel knowledge, represented as time series predictive models. In this respect, a new evolutionary multi-objective search method is proposed to limit complexity of evolved solutions and to improve predictive quality. Using these methods allows for obtaining lower complexity (and possibly more comprehensible) models with high predictive quality, keeping run time and memory requirements low, and avoiding bloat and over-fitting. The methods are assessed on five real-world long memory time series and their performance is compared to that of statistical models reported in the literature. Experimental results show the proposed methods' advantages in long memory time series forecasting. © Springer Science+Business Media, LLC 2011.

Costanza G.,National University of San Luis
Physica A: Statistical Mechanics and its Applications | Year: 2012

The proof of a theorem that allows one to construct deterministic evolution equations from a set, with two subsets, containing two types of discrete stochastic evolution equation is developed. One subset evolves Markovianly and the other non-Markovianly. As an illustrative example, the deterministic evolution equations of quantum electrodynamics are derived from two sets of Markovian and non-Markovian stochastic evolution equations, of different type, after an average over realization, using the theorem. This example shows that deterministic differential equations that contain both first-order and second-order time derivatives can be derived after a Taylor series expansion of the dynamical variables. It is shown that the derivation of such deterministic differential equations can be done by solving a set of linear equations. Two explicit examples, the first containing updating rules that depend on one previous time step and the second containing updating rules that depend on two previous time steps, are given in detail in order to show step by step the linear transformations that allow one to obtain the deterministic differential equations. © 2011 Elsevier B.V. All rights reserved.

Alvarez E.,National University of San Luis | Alvarez E.,SLAC
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We study how the significance of top quark induced charge asymmetries at the LHC may be enhanced exploiting the tt̄ total transverse momentum to enrich the fraction of quark-fusion events in the sample. We combine this variable with previous variables related to the boost and the invariant mass of the tt̄ pair to find an optimum cut which maximizes the significance of the asymmetry when systematic and statistic errors are taken into account. We find that including the tt̄ transverse momentum in the analysis of the expected 2012 LHC data provides a considerable enhancement in the significance of the asymmetry. © 2012 American Physical Society.

Costanza G.,National University of San Luis
Physica A: Statistical Mechanics and its Applications | Year: 2014

Non-Markovian continuum stochastic and deterministic equations are derived from a set of discrete stochastic and deterministic evolution equations. Examples are given of discrete evolution equations whose updating rules depend on two or more previous time steps. Among them, the continuum stochastic evolution equation of the Newton second law, the stochastic evolution equation of a wave equation, the stochastic evolution equation for the scalar meson field, etc. are obtained as special cases. Extension to systems of evolution equations and other extensions are considered and examples are given. The concept of isomorphism and almost isomorphism are introduced in order to compare the coefficients of the continuum evolution equations of two different smoothing procedures that arise from two different approaches. Usually these discrepancies arising from two sources: On the one hand, the use of different representations of the generalized functions appearing in the models and, on the other hand, the different approaches used to describe the models. These new concept allows to overcome controversies that were appearing during decades in the literature. © 2014 Elsevier B.V.

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