Browsing by Autor "Carlos Segovia"

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    Chen-Ruan Cohomology of cotangent orbifolds and Chas-Sullivan String Topology
    (International Press of Boston, 2007) Ana González; Ernesto Lupercio; Carlos Segovia; Bernardo Uribe; Miguel A. Xicoténcatl
    In this paper we prove that for an almost complex orbifold, its virtual orbifold cohomology
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    On the Density of Certain Languages with $p^2$ Letters
    (Electronic Journal of Combinatorics, 2015) Carlos Segovia; Monika Winklmeier
    The sequence $(x_n)_{n\in\mathbb N} = (2,5,15,51,187,\ldots)$ given by the rule $x_n=(2^n+1)(2^{n-1}+1)/3$ appears in several seemingly unrelated areas of mathematics. For example, $x_n$ is the density of a language of words of length $n$ with four different letters. It is also the cardinality of the quotient of $(\mathbb Z_2\times \mathbb Z_2)^n$ under the left action of the special linear group $\mathrm{SL}(2,\mathbb Z)$. In this paper we show how these two interpretations of $x_n$ are related to each other. More generally, for prime numbers $p$ we show a correspondence between a quotient of $(\mathbb Z_p\times\mathbb Z_p)^n$ and a language with $p^2$ letters and words of length $n$.