Self-dual polygons and self-dual curves

We study projectively self-dual polygons and curves in the projective plane. Our results provide a partial answer to problem No 1994-17 in the book of Arnold’s problems (2004).     

Self-dual weak Hopf algebras

In this paper, we define the notion of self-dual graded weak Hopf algebra and self-dual semilattice graded weak Hopf algebra. We give characterization of finite-dimensional such algebras when they are in structually simple forms in the sense of E. L. Green and E. N. Morcos. We also give the definition of self-dual weak Hopf quiver and apply these types of quivers to classify the finite- dimensional self-dual semilattice graded weak Hopf algebras. Finally, we prove partially the conjecture given by N. Andruskiewitsch and H.-J. Schneider in the case of finite-dimensional pointed semilattice graded weak Hopf algebra H when grH is self-dual.     

Structure of quasitriangular quasi—hopf algebras

Physicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Khar'kov. Translated from Funktsional'nyi Analiz i Ego Prilozheniya, Vol. 26, No. 1, pp. 78–80, January–March, 1992.     

Symmetric semisimple modules of group algebras over finite fields and self-dual permutation codes

A module of a finite group over a finite field with a symmetric non-degenerate bilinear form which is invariant by the group action is called a symmetric module. In this paper, a characterization of indecomposable orthogonal decompositions of symmetric semisimple modules and a criterion for the hyperbolic symmetric modules are obtained, and some applications to the self-dual permutation codes are shown.     

Terms that are self-dual in Boolean algebras but not in MO 2

An absorption law is an identity of the form p = x. The ternary function x+y+z (ring addition) in Boolean algebras satisfies three absorption laws in two variables. If a term satisfies these three identities in a variety, it is called a minority term for that variety. We construct a minority term p for orthomodular lattices such the identity defines Boolean algebras modulo orthomodular lattices. (The dual of p is denoted by .) Consequently, having a unique minority term function characterizes Boolean algebras among orthomodular lattices. Our main result generalizes this example to arbitrary arity and arbitrary consistent sets of 2-variable absorption laws. Presented by J. Berman.     

Self-dual sequences

A study is made on self-dual sequences. Some enumeration problems on the number of these sequences and the number of cycles of length k which can be produced by an n-stage shift register are investigated. Also, some full cycles with special properties are constructed from those sequences.     

Self-dual continuous processes

The important application of semi-static hedging in financial markets naturally leads to the notion of conditionally quasi self-dual processes which is, for continuous semimartingales, related to conditional symmetry properties of both their ordinary as well as their stochastic logarithms. We provide a structure result for continuous conditionally quasi self-dual processes. Our main result is to give a characterization of continuous Ocone martingales via a strong version of self-duality.     

Self-dual lattice identities

Given a finitely based self-dual variety of lattices, is it definable, modulo lattice theory, by a single self-dual lattice identity? There are infinitely many examples with “yes” as the answer and infinitely many with “no.”. Received December 20, 1999; accepted in final form July 11, 2002.     

Irredundant self-dual bases for self-dual lattice varieties

For any finitely based self-dual variety of lattices, we determine the sizes of all equational bases that are both irredundant and self-dual. We make the same determination for {0, 1}-lattice varieties.Received July 11, 2002; accepted in final form August 27, 2004.     

Upper quasi continuous maps and quasi continuous selections

The paper deals with the existence of a quasi continuous selection of a multifunction for which upper inverse image of any open set with compact complement contains a set of the form (G \ I) ∪ J, where G is open and I, J are from a given ideal. The methods are based on the properties of a minimal multifunction which is generated by a cluster process with respect to a system of subsets of the form (G \ I) ∪ J.     

Every self-dual ordering has a self-dual linear extension

In this note, it is showed that every self-dual ordering has a self-dual linear extension.     

Self-dual, not self-polar

The smallest number of points of an incidence structure which is self-dual but not self-polar is 7. For non-binary structures (where a “point” may occur more than once in a “block”) the number is 6.     

Strongly self-dual graphs

We present a class of graphs whose adjacency matrices are nonsingular with integral inverses, denoted h-graphs. If the h-graphs G and H with adjacency matrices M(G) and M(H) satisfy M(G)^-1=SM(H)S, where S is a signature matrix, we refer to H as the dual of G. The dual is a type of graph inverse. If the h-graph G is isomorphic to its dual via a particular isomorphism, we refer to G as strongly self-dual. We investigate the structural and spectral properties of strongly self-dual graphs, with a particular emphasis on identifying when such a graph has 1 as an eigenvalue.     

Boolean designs and self-dual matroids

A proper splitting of a rectangular matrix A is one of the form A = M ? N, where A and M have the same range and null spaces. This concept was introduced by R. Plemmons as a means of generalizing to rectangular and singular matrices the concept of a regular splitting of a nonsingular matrix as introduced by R. Varga. In consideration of the linear system Ax=b, A. Berman and R. Plemmons used a proper splitting of A into M ? N and showed that the iteration x⁽ⁱ⁺¹⁾=M⁺Nx⁽ⁱ⁾+M⁺b converges to A⁺b, the best least-squares solution to the system, if and only if the spectral radius of M⁺N is less than one. The purpose of this paper is to further develop the characteristics of proper splittings and to extend these previous results by replacing the Moore-Penrose generalized inverse with a least-squares g-inverse, a minimum-norm g-inverse, or a g-inverse. Also, some criteria are given for comparing convergence rates of M_i^?N_i, where A = M₁?N₁ = M₂?N₂, and a method is developed for constructing proper splittings of special types of matrices.