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Rings whose modules are finitely generated over their endomorphism rings

Nguyen Viet DungJosé Luis García — 2009

Colloquium Mathematicae

A module M is called finendo (cofinendo) if M is finitely generated (respectively, finitely cogenerated) over its endomorphism ring. It is proved that if R is any hereditary ring, then the following conditions are equivalent: (a) Every right R-module is finendo; (b) Every left R-module is cofinendo; (c) R is left pure semisimple and every finitely generated indecomposable left R-module is cofinendo; (d) R is left pure semisimple and every finitely generated indecomposable left R-module is finendo;...

Grüss-type bounds for covariances and the notion of quadrant dependence in expectation

Martín EgozcueLuis GarcíaWing-Keung WongRičardas Zitikis — 2011

Open Mathematics

We show that Grüss-type probabilistic inequalities for covariances can be considerably sharpened when the underlying random variables are quadrant dependent in expectation (QDE). The herein established covariance bounds not only sharpen the classical Grüss inequality but also improve upon recently derived Grüss-type bounds under the assumption of quadrant dependency (QD), which is stronger than QDE. We illustrate our general results with examples based on specially devised bivariate distributions...

Dynamics of a Lotka-Volterra map

Francisco BalibreaJuan Luis García GuiraoMarek LampartJaume Llibre — 2006

Fundamenta Mathematicae

Given the plane triangle with vertices (0,0), (0,4) and (4,0) and the transformation F: (x,y) ↦ (x(4-x-y),xy) introduced by A. N. Sharkovskiĭ, we prove the existence of the following objects: a unique invariant curve of spiral type, a periodic trajectory of period 4 (given explicitly) and a periodic trajectory of period 5 (described approximately). Also, we give a decomposition of the triangle which helps to understand the global dynamics of this discrete system which is linked with the behavior...

Sobre el parámetro complejidad lineal y los filtros no lineales de segundo orden.

Amparo Fúster SabaterLuis J. García Villalba — 2000

Revista Matemática Complutense

A new method of analysing the linear complexity of 2nd-order nonlinear filterings of m-sequences that is based on the concept of regular coset is present. The procedure considers any value of the LFSR's length, L, (prime or composite number). Emphasis is on the geometric interpretation of the regular cosets which produce degeneracies in the linear complexity of the filtered sequence. Numerical expressions to compute the linear complexity of such sequences are given as well as practical rules to...

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