A partition of R in two homogeneous and homeomorphic parts
A partition of the Catalan numbers and enumeration of genealogical trees
A special relational structure, called genealogical tree, is introduced; its social interpretation and geometrical realizations are discussed. The numbers of all abstract genealogical trees with exactly n+1 nodes and k leaves is found by means of enumeration of code words. For each n, the form a partition of the n-th Catalan numer Cₙ, that means .
A partition of the non-negative integers, with applications.
A partition theorem for α-large sets
A path(ological) partition problem
Let τ(G) denote the number of vertices in a longest path of the graph G and let k₁ and k₂ be positive integers such that τ(G) = k₁ + k₂. The question at hand is whether the vertex set V(G) can be partitioned into two subsets V₁ and V₂ such that τ(G[V₁] ) ≤ k₁ and τ(G[V₂] ) ≤ k₂. We show that several classes of graphs have this partition property.
A permutation regularity lemma.
A permutations representation that knows what “Eulerian” means.
A Pfaffian-Hafnian analogue of Borchardt's identity.
A Pieri-type formula for even orthogonal Grassmannians
We study the cohomology ring of the Grassmannian G of isotropic n-subspaces of a complex 2m-dimensional vector space, endowed with a nondegenerate orthogonal form (here 1 ≤ n < m). We state and prove a formula giving the Schubert class decomposition of the cohomology products in H*(G) of general Schubert classes by "special Schubert classes", i.e. the Chern classes of the dual of the tautological vector bundle of rank n on G. We discuss some related properties of reduced decompositions of "barred...
A Pieri-type theorem for Lagrangian and odd Orthogonal Grassmannians.
A Pivoting Algorithm for Convex Hulls and Vertex Enumeration of Arrangements and Polyhedra.
A plethysm formula for .
A polyhedral study of a two level facility location model
We study an uncapacitated facility location model where customers are served by facilities of level one, then each level one facility that is opened must be assigned to an opened facility of level two. We identify a polynomially solvable case, and study some valid inequalities and facets of the associated polytope.
A polynomial algorithm for minDSC on a subclass of series Parallel graphs
The aim of this paper is to show a polynomial algorithm for the problem minimum directed sumcut for a class of series parallel digraphs. The method uses the recursive structure of parallel compositions in order to define a dominating set of orders. Then, the optimal order is easily reached by minimizing the directed sumcut. It is also shown that this approach cannot be applied in two more general classes of series parallel digraphs.
A positive proof of the Littlewood-Richardson rule using the octahedron recurrence.
A Poster about the Old History of Fractional Calculus
MSC 2010: 26A33, 05C72, 33E12, 34A08, 34K37, 35R11, 60G22The fractional calculus (FC) is an area of intensive research and development. In a previous paper and poster we tried to exhibit its recent state, surveying the period of 1966-2010. The poster accompanying the present note illustrates the major contributions during the period 1695-1970, the "old history" of FC.
A prime factor theorem for a generalized direct product
We introduce the concept of neighborhood systems as a generalization of directed, reflexive graphs and show that the prime factorization of neighborhood systems with respect to the the direct product is unique under the condition that they satisfy an appropriate notion of thinness.
A probabilistic approach to the asymptotics of the length of the longest alternating subsequence.
A probabilistic proof of a weak limit law for the number of cuts needed to isolate the root of a random recursive tree.
A problem concerning -pancyclic graphs