Formations of finite monoids and formal languages: Eilenberg's variety theorem revisited

We present an extension of Eilenberg's variety theorem, a well-known result connecting algebra to formal languages. We prove that there is a bijective correspondence between formations of finite monoids and certain classes of languages, the formations of languages. Our result permits to treat classes of finite monoids which are not necessarily closed under taking submonoids, contrary to the original theory. We also prove a similar result for ordered monoids.The authors are supported by Proyecto MTM2010-19938-C03-01 from MICINN (Spain). The second author is supported by the project ANR 2010 BLAN 0202 02 FREC. The third author was supported by the Grant PAID-02-09 from Universitat Politècnica de València

Languages associated with saturated formations of groups

In a previous paper, the authors have shown that Eilenberg's variety theorem can be extended to more general structures, called formations. In this paper, we give a general method to describe the languages corresponding to saturated formations of groups, which are widely studied in group theory. We recover in this way a number of known results about the languages corresponding to the classes of nilpotent groups, soluble groups and supersoluble groups. Our method also applies to new examples, like the class of groups having a Sylow tower.The authors are supported by Proyecto MTM2010-19938-C03-01 from MICINN (Spain). The first author acknowledges support from MEC. The second author is supported by the project ANR 2010 BLAN 0202 02 FREC. The third author was supported by the Grant PAID-02-09 from Universitat Politècnica de València

Finite automata for Schreier graphs of virtually free groups

The Stallings construction for f.g. subgroups of free groups is generalized by introducing the concept of Stallings section, which allows efficient computation of the core of a Schreier graph based on edge folding. It is proved that the groups that admit Stallings sections are precisely the f.g. virtually free groups, this is proved through a constructive approach based on Bass-Serre theory. Complexity issues and applications are also discussed.Peer ReviewedPostprint (published version

Flag codes from planar spreads in network coding

In this paper we study a class of multishot network codes given by families of nested subspaces (flags) of a vector space Fnq, being qa prime power and Fqthe finite field of qelements. In particular, we focus on flag codes having maximum distance (optimum distance flag codes). We explore the existence of these codes from spreads, based on the good properties of the latter ones. For n =2k, we show that optimum distance full flag codes with the largest size are exactly those that can be constructed from a planar spread. We give a precise construction of them as well as a decoding algorithm.The first and third authors are partially supported by Projecte AICO/2017/128 of Generalitat Valenciana. The second author is supported by Generalitat Valenciana and Fondo Social Europeo. Grants: ACIF/2018/196 and BEFPI/2019/070. The third author is also supported by the grant BEST/2019/192 of Generalitat Valenciana

Flag Codes: Distance Vectors and Cardinality Bounds

Given Fq the finite field with q elements and an integer n > 2, a flag is a sequence of nested subspaces of Fnq and a flag code is a nonempty set of flags. In this context, the distance between flags is the sum of the corresponding subspace distances. Hence, a given flag distance value might be obtained by many different combinations. To capture such a variability, in the paper at hand, we introduce the notion of distance vector as an algebraic object intrinsically associated to a flag code that encloses much more information than the distance parameter itself. Our study of the flag distance by using this new tool allows us to provide a fine description of the structure of flag codes as well as to derive bounds for their maximum possible size once the minimum distance and dimensions are fixed.The authors received financial support of Ministerio de Ciencia e Innovación (PID2019-108668GB-I00). The second author is supported by Generalitat Valenciana and Fondo Social Europeo (ACIF/2018/196)

Flag Codes: Distance Vectors and Cardinality Bounds

Given Fq the finite field with q elements and an integer n > 2, a flag is a sequence of nested subspaces of Fnq and a flag code is a nonempty set of flags. In this context, the distance between flags is the sum of the corresponding subspace distances. Hence, a given flag distance value might be obtained by many different combinations. To capture such a variability, in the paper at hand, we introduce the notion of distance vector as an algebraic object intrinsically associated to a flag code that encloses much more information than the distance parameter itself. Our study of the flag distance by using this new tool allows us to provide a fine description of the structure of flag codes as well as to derive bounds for their maximum possible size once the minimum distance and dimensions are fixed.The authors received financial support of Ministerio de Ciencia e Innovación (PID2019-108668GB-I00). The second author is supported by Generalitat Valenciana and Fondo Social Europeo (ACIF/2018/196)

Optimum distance flag codes from spreads via perfect matchings in graphs

In this paper, we study flag codes on the vector space Fnq, being q a prime power and Fq the finite field of q elements. More precisely, we focus on flag codes that attain the maximum possible distance (optimum distance flag codes) and can be obtained from a spread of Fnq. We characterize the set of admissible type vectors for this family of flag codes and also provide a construction of them based on well-known results about perfect matchings in graphs. This construction attains both the maximum distance for its type vector and the largest possible cardinality for that distance.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The authors receive financial support from Ministerio de Ciencia e Innovación PID2019-108668GB-I00 (Spain). The first and third authors are partially supported by Projecte AICO/2017/128 of Generalitat Valenciana (Spain). The second author is supported by Generalitat Valenciana and Fondo Social Europeo, grant number: ACIF/2018/196 (Spain)

An orbital construction of optimum distance flag codes

Flag codes are multishot network codes consisting of sequences of nested subspaces (flags) of a vector space Fnq, where q is a prime power and Fq, the finite field of size q. In this paper we study the construction on F2kq of full flag codes having maximum distance (optimum distance full flag codes) that can be endowed with an orbital structure provided by the action of a subgroup of the general linear group. More precisely, starting from a subspace code of dimension k and maximum distance with a given orbital description, we provide sufficient conditions to get an optimum distance full flag code on F2kq having an orbital structure directly induced by the previous one. In particular, we exhibit a specific orbital construction with the best possible size from an orbital construction of a planar spread on F2kq that strongly depends on the characteristic of the field.The authors receive financial support from Ministerio de Ciencia e Innovación (PID2019-108668GB-I00). The second author is supported by Generalitat Valenciana and Fondo Social Europeo (ACIF/2018/196)

Seguimiento Grado en Matemáticas. Curso 13-14

El objetivo principal de esta red ha sido la coordinación y seguimiento de los cursos correspondientes al Grado en Matemáticas que se ha implantado en su totalidad en el presente curso académico en la Facultad de Ciencias de la Universidad de Alicante y se engloba dentro del proceso general del seguimiento de todos los títulos de la Facultad de Ciencias. La red está coordinada por la coordinadora del Grado en Matemáticas y formada por los coordinadores de cada uno de los semestres. Se pretende evidenciar los progresos del título en el desarrollo del Sistema de Garantía Interno de Calidad (SGIC), con el fin de detectar las posibles deficiencias en el proceso de implantación del grado y contribuir a sus posibles mejoras elaborando propuestas de acciones para mejorar su diseño y desarrollo