| 16/2000 |
Large deviations in random media of zero mean asymmetric zero range processes A. Koukkous We consider an asymmetric zero range process with zero mean in infinite volume with random jump rates starting from equilibrium. We investigate large deviations from hydrodynamical limit of the empirical distribution of particles and prove an upper and lower bound for a large deviation principle. Our main argument is based on a super-exponential estimate in infinite volume. We adapt a method developed by Kipnis \& al. (1989) and Benois \& al. (1995).  rp-2000-16.pdf |
| 15/2000 |
On the Approximation of Fuzzy Sets Heriberto Román-Flores, Yurilev Chalco-Cano, Marko A. Rojas-Medar The purpose of this work is studying the approximation of normal fuzzy sets with compact support and the convolution $(f\bigtriangledown g)(x)=\sup \{f(x-y)\wedge g(y):y\in X\}$ of two fuzzy sets. In particular, by using $\bigtriangledown $-convolution, a density result is proved. rp-2000-15.pdf |
| 14/2000 |
The compression semigroup of a cone is connected João Ribeiro Gonçalves Filho, Luiz A. B. San Martin Let $W\subset \Bbb{R}^{n}$ be a pointed and generating cone and denote by $S(W)$ the semigroup of matrices with positive determinant leaving $W$ invariant. The purpose of this paper is to prove that $S(W)$ is path connected. This result has the following consequence: Semigroups with nonempty interior in the group $\mathrm{Sl}( n,\Bbb{R}) $ are classified into types, each type being labelled by a flag manifold. The semigroups whose type is given by the projective space $\Bbb{P}^{n-1}$ form one of the classes. It is proved here that the semigroups in $\mathrm{Sl}(n,\Bbb{R})$ leaving invariant a pointed and generating cone are the only maximal connected in the class of $\Bbb{P}^{n-1}$. rp-2000-14.pdf |
| 13/2000 |
Stationary Micropolar Fluid Flows with Boundary Data in $L^2$ Grzegorz Lukaszewicz, Marko A. Rojas-Medar, Marcelo M. Santos We consider the Dirichlet boundary value problem for the equations of a stationary micropolar fluid in a bounded three dimensional domain. We show the existence and uniqueness of a distributional solution with boundary values in $L^2$. rp-2000-13.pdf |
| 12/2000 |
On critical semilinear elliptic systems Yang Jianfu We establish in this paper existence results for critical strongly indefinite semilinear elliptic systems defined on both bounded domains and $\Bbb R^N$. rp-2000-12.pdf |
| 11/2000 |
Differential operators in quaternionic quantum mechanics Stefano De Leo, Gisele C. Ducati Motivados por uma formula\c{c}\~ao quaterni\^onica da mec\^anica qu\^antica, discutimos equa\c{c}\~oes diferencias quaterni\^onicas lineares em ${\bf C}$ e ${\bf H}$. Tocamos somente alguns aspectos da teoria matem\'atica, ao saber a resolu\c{c}\~ao de equa\c{c}\~oes diferencias quaterni\^onicas de segunda ordem com coeficientes constantes. Superamos os problems que surgem da perda do teorema fundamental da \'algebra para quaternions e propomos um m\'etodo pr\'atico para resolver equa\c{c}\~oes diferencias quaterni\^onicas de segunda ordem, lineares em ${\bf C}$ e ${\bf H}$, com coeficientes constantes. A resolu\c{c}\~ao da equa\c{c}\~ao de Schr\"odinger linear em ${\bf C}$, em presen\c{c}a de potenciais quaterni\^onicos, representa uma aplica\c{c}\~ao interessante do material matem\'atico discutido neste artigo. rp-2000-11.pdf |
| 10/2000 |
On the controllability of stationary magneto-micropolar fluids J. Ortega, Marko A. Rojas-Medar In this work we some results on the boundary controllability of the steady magneto-micropolar fluids. In particular we consider the boundary controllability of the fluid velocity on a subset of the boundary. In the same way, we can obtain some controllability results when we consider the case of two or more boundary controls for the microrotational velocity or the magnetic fields. In the case of the homogeneous boundary conditions, we can obtain some results for the internal controllability. rp-2000-10.pdf |
| 9/2000 |
Simulation study for misspecifications on a frailty model A. Ferreira, Nancy L. Garcia Nielsen, G.G.; Gill, R.D.; Andersen, P.K.; Sorensen, T.I.A. (1992) A Counting Process Approach to Maximum Likelihood Estimation in Frailty Models. {\it Scandinavian Journal of Statistics} {\bf 19}:25--43 propose a consistent and asymptotically normal estimator for the variance of the frailty distribution under gamma assumption. A simulation study shows that this estimator is asymptotically biased for log-normal and normal frailty distributions. rp-2000-9.pdf |
| 8/2000 |
On complete arcs arising from plane curves F. Giulietti, F. Pambianco, Fernando Torres, E. Ughi We show that the set of $\fq$-rational points of either certain Fermat curves or certain $\fq$-Frobenius non-classical plane curves is a complete $(k,d)$-arc in $\P^2(\fq)$, where $k$ and $d$ are respectively the number of $\fq$-rational points and the degree of the underlying curve. rp-2000-8.pdf |
| 7/2000 |
Remarks on plane maximal curves A. Aguglia, G. Korchmáros, Fernando Torres Some new results on plane $\fq$-maximal curves are stated and proved. By \cite{r-sti}, the degree $d$ of a plane $\fq$-maximal curve is less than or equal to $q+1$ and equality holds if and only if the curve is $\fq$-isomorphic to the Hermitian curve. We show that $d\leq q+1$ can be improved to $d\leq (q+2)/2$ apart from the case $d=q+1$ or $q\leq 5$. This upper bound turns out to be sharp for $q$ odd. In \cite{carbonne-henocq} it was pointed out that some Hurwitz curves are plane $\fq$-maximal curves. Here we prove that (\ref{eq1.2}) is the necessary and sufficient condition for a Hurwitz curve to be $\fq$-maximal. We also show that this criterium holds true for the $\fq$-maximality of a wider family of curves. rp-2000-7.pdf |
