Geometric representations of linear codes

We say that a linear code C over a field F is triangular representable if there exists a two dimensional simplicial complex $\Delta$ such that C is a punctured code of the kernel ker $\Delta$ of the incidence matrix of $\Delta$ over F and there is a linear mapping between C and ker $\Delta$ which is a bijection and maps minimal codewords to minimal codewords. We show that the linear codes over rationals and over GF(p), where p is a prime, are triangular representable. In the case of finite fields, we show that this representation determines the weight enumerator of C. We present one application of this result to the partition function of the Potts model. On the other hand, we show that there exist linear codes over any field different from rationals and GF(p), p prime, that are not triangular representable. We show that every construction of triangular representation fails on a very weak condition that a linear code and its triangular representation have to have the same dimension.Comment: 20 pages, 8 figures, v3 major change

Geometric representation of binary codes and computation of weight enumerators

For every linear binary code $C$, we construct a geometric triangular configuration $\Delta$ so that the weight enumerator of $C$ is obtained by a simple formula from the weight enumerator of the cycle space of $\Delta$. The triangular configuration $\Delta$ thus provides a geometric representation of $C$ which carries its weight enumerator. This is the initial step in the suggestion by M. Loebl, to extend the theory of Pfaffian orientations from graphs to general linear binary codes. Then we carry out also the second step by constructing, for every triangular configuration $\Delta$, a triangular configuration $\Delta'$ and a bijection between the cycle space of $\Delta$ and the set of the perfect matchings of $\Delta'$.Comment: 16 pages, 11 figures, submitted to Advances in Applied Mathematics, v2: major conceptual change

Lattices and Codes

This thesis studies triangular con gurations, binary matroids, and integer lattices generated by the codewords of a binary code. We study the following hypothesis: the lattice generated by the codewords of a binary code has a basis consisting only of the codewords. We prove the hypothesis for the matroids with the good ear decomposition. We study the operation of edge contraction in the triangular con gurations. Especially in cycles and acyclic triangular con gurations. For an arbitrary graph we nd a triangular con guration with the skeleton containing this graph as a minor. For every binary matroid we construct a triangular con guration such that the matroid is a minor of the con guration. We prove that between the cycle spaces of the matroid and the con guration exists a bijection. The bijection maps the circuits of the matroid to the circuits of the con guration

Geometrické a algebraické vlastnosti diskrétních struktur

In the thesis we study two dimensional simplicial complexes and linear codes. We say that a linear code C over a field F is triangular representable if there exists a two dimensional simplicial complex ∆ such that C is a punctured code of the kernel ker ∆ of the incidence matrix of ∆ over F and dim C = dim ker ∆. We call this simplicial complex a geometric representation of C. We show that every linear code C over a primefield is triangular representable. In the case of finite primefields we construct a geometric representation such that the weight enumerator of C is obtained by a simple formula from the weight enumerator of the cycle space of ∆. Thus the geometric representation of C carries its weight enumerator. Our motivation comes from the theory of Pfaffian orientations of graphs which provides a polynomial algorithm for weight enumerator of the cut space of a graph of bounded genus. This algorithm uses geometric properties of an embedding of the graph into an orientable Riemann surface. Viewing the cut space of a graph as a linear code, the graph is thus a useful geometric representation of this linear code. We study embeddability of the geometric representations into Euclidean spaces. We show that every binary linear code has a geometric representation that can be embed- ded into R4 . We characterize...V práci se zabýváme dvou-dimenzionálními simpliciálními komplexy a lineárními kódy. Řekneme, že lineární kód C nad tělesem F je trojúhelníkově reprezentovatelný, pokud exis- tuje dvou-dimenzionální simpliciální komplex ∆ takový, že kód C je propíchnutým kódem jádra ker ∆ incidenční matice simpliciálního komplexu ∆ nad F a dim C = dim ker ∆. Tento simpliciální komplex nazveme geometrickou reprezentací kódu C. Dokážeme, že každý lineární kód nad prvotělesem je trojúhelníkově reprezentovatelný. Pro konečná prvotělesa sestrojíme geometrickou reprezentaci takovou, že váhový polynom kódu C je dán jednoduchou formulí váhového polynomu prostoru cyklů simpliciálního kom- plexu ∆. Tedy geometrická reprezentace kódu C určuje jeho váhový polynom. Naše motivace pochází z teorie pfaffiánovských orientací grafů, která poskytuje polyno- miální algoritmus pro výpočet váhového polynomu prostoru řezů grafu s omezeným rodem. Tento algoritmus využívá geometrických vlastností nakreslení grafu na orientovatelnou ri- emannovskou plochu. Prostor řezů je lineární kód a odpovídající graf je jeho užitečnou geometrickou reprezentací. Dále studujeme vnořitelnost geometrických reprezentací do euklidovských prostorů. Ukážeme, že každý binární lineární kód má geometrickou reprezentaci v R4 . Charakte- rizujeme binární lineární kódy, které...Katedra aplikované matematikyDepartment of Applied MathematicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Geometric and algebraic properties of discrete structures

In the thesis we study two dimensional simplicial complexes and linear codes. We say that a linear code C over a field F is triangular representable if there exists a two dimensional simplicial complex ∆ such that C is a punctured code of the kernel ker ∆ of the incidence matrix of ∆ over F and dim C = dim ker ∆. We call this simplicial complex a geometric representation of C. We show that every linear code C over a primefield is triangular representable. In the case of finite primefields we construct a geometric representation such that the weight enumerator of C is obtained by a simple formula from the weight enumerator of the cycle space of ∆. Thus the geometric representation of C carries its weight enumerator. Our motivation comes from the theory of Pfaffian orientations of graphs which provides a polynomial algorithm for weight enumerator of the cut space of a graph of bounded genus. This algorithm uses geometric properties of an embedding of the graph into an orientable Riemann surface. Viewing the cut space of a graph as a linear code, the graph is thus a useful geometric representation of this linear code. We study embeddability of the geometric representations into Euclidean spaces. We show that every binary linear code has a geometric representation that can be embed- ded into R4 . We characterize..

Geometric and algebraic properties of discrete structures

In the thesis we study two dimensional simplicial complexes and linear codes. We say that a linear code C over a field F is triangular representable if there exists a two dimensional simplicial complex ∆ such that C is a punctured code of the kernel ker ∆ of the incidence matrix of ∆ over F and dim C = dim ker ∆. We call this simplicial complex a geometric representation of C. We show that every linear code C over a primefield is triangular representable. In the case of finite primefields we construct a geometric representation such that the weight enumerator of C is obtained by a simple formula from the weight enumerator of the cycle space of ∆. Thus the geometric representation of C carries its weight enumerator. Our motivation comes from the theory of Pfaffian orientations of graphs which provides a polynomial algorithm for weight enumerator of the cut space of a graph of bounded genus. This algorithm uses geometric properties of an embedding of the graph into an orientable Riemann surface. Viewing the cut space of a graph as a linear code, the graph is thus a useful geometric representation of this linear code. We study embeddability of the geometric representations into Euclidean spaces. We show that every binary linear code has a geometric representation that can be embed- ded into R4 . We characterize..

Elements of Probability and Mathematical Statistics

Monografie základů pravděpodobnosti a statistických metod v ekonomických aplikacíchA book of probability and statistical methods for applications in economy

Decision-making Under Risk and Uncertainty Theoretically and Practically

Kniha je souhrnem podkladů a příkladů z oblasti rozhodování v riziku a nejistotě/neurčitosti. Pokrývá především oblasti teorie her, teorii grafů a vícekriteriální optimalizaci.This book deals with the basic theory of decision making and with exact as well as heuristic methods which are utilized therein. Problems under scrutiny are those which originate from the theory of matrix games and problems which originate from Bayes theory.

Statistical Analysis Methods Theoretically and Practically

Kniha je souhrnem podkladů a příkladů z oblasti pravděpodobnosti a matematické statisticky. Pokrývá především oblasti popisné statistiky, regresní a korelační analýzy, intervalů spolehlivosti a testování hypotéz. Jako knižní přítisk se objevuje bakalářská práce o grafickém vytěžování dat, především ve volně dostupném výpočetním prostředí R.This book deals with the terminology and applications of descriptive and mathematical statistics, the types of differentiation of random variables, the testing of hypotheses, and the methods for estimations. It also covers the graphical data mining and the use of the computational environment, the R language.