We construct a family of posets, called signed Birkhoff posets, that may be viewed as signed analogs of distributive lattices. Our posets are generally not lattices, but they are shown to posses many combinatorial properties corresponding to well known properties of distributive lattices. They have the additional virtue of being face posets of regular cell decompositions of spheres. We give a c...

Birkhoff (or lacunary) interpolation is an extension of polynomial interpolation that appears when observation gives irregular information about function and its derivatives. A Birkhoff interpolation problem is not always solvable even in the appropriate polynomial or rational space. In this paper we split up the initial problem in subproblems having a unique polynomial solution and use multino...

Indeed, in [3] they showed that, if one of the invariant circles of f is missing, then for some p and q with gcd(p; q) = 1 the map must have a periodic orbit of type (p; q) which is not a Birkhoff orbit. On the other hand, Boyland showed in [2] that a twistmap with a non Birkhoff periodic orbit of type (p; q) (gcd(p; q) = 1 must have positive topological entropy, which clearly implies the theorem.

The integrability of this system was conjectured in [16] and in the book of V.V. Kozlov [17]. This system appears first in the classification of Birkhoff integrable systems by Kozlov and Treshchev [16]. The classification involves systems with exponential interraction with sufficient number of integrals, polynomial in the momenta. The classification gives necessary conditions for a system with ...

The Birkhoff polytope Bn is the convex hull of all (n×n) permutation matrices, i.e., matrices where precisely one entry in each row and column is one, and zeros at all other places. This is a widely studied polytope with various applications throughout mathematics. In this paper we study combinatorial types L of faces of a Birkhoff polytope. The Birkhoff dimension bd(L) of L is the smallest n s...

A compact formulation of the set of tours neither in a graph nor its complement is presented and illustrates a general methodology proposed for constructing polyhedral models of decision problems based upon permutations, projection and lifting techniques. Directed Hamilton tours on n vertex graphs are interpreted as (n-1)- permutations. Sets of extrema of Birkhoff polyhedra are mapped to tours ...