Advance in technology and commercial media has simplified the process of collecting large-scale visual data, but it also raises new challenges in data organization. In this paper, we propose to characterize data association by recovering an intrinsic order from an unorganized dataset. Our method is motivated by smooth manifold geometry. We advocate that the optimal data order should encode the ...

Bivariate generating functions for various subsets of the class of permutations containing no descending sequence of length three or more are determined. The notion of absolute indecomposability of a permutation is introduced, and used in enumerating permutations which have a block structure avoiding 321, and whose blocks also have such structure (recursively). Generalizations of these results ...

Bivariate generating functions for various subsets of the class of permutations containing no descending sequence of length three or more are determined. The notion of absolute indecomposability of a permutation is introduced, and used in enumerating permutations which have a block structure avoiding 321, and whose blocks also have such structure (recursively). Generalizations of these results ...

Given any structure for the language of set theory and a permutation of its domain one obtains a new structure for the language of set theory. These are Rieger-Bernays models. Thus we have a surjection from the full symmetric group of the domain to a family of structures. Both groups and families-of-structures have natural topologies and it is natural to wonder what sensible things can be said ...

Pattern avoidance classes of permutations that cannot be expressed as unions of proper subclasses can be described as the set of subpermutations of a single bijection. In the case that this bijection is a permutation of the natural numbers a structure theorem is given. The structure theorem shows that the class is almost closed under direct sums or has a rational generating function.

We describe an event-style (or poset) semantics for connict-free rewrite systems, such as the-calculus, and other stable transition systems with a residual relation. Our interpretation is based on considering redex-families as events. It treats permutation-equivalent reductions as representing the same concurrent computation. Due to erasure of redexes, Event Structures are inadequate for such a...

It is often the case that systems are “nearly symmetric”; they exhibit symmetry in a part of their description but are, nevertheless, globally asymmetric. We formalize several notions of near symmetry and show how to obtain the benefits of symmetry reduction when applied to asymmetric systems which are nearly symmetric. We show that for some nearly symmetric systems it is possible to perform sy...

A d-dimensional permutation is a sequence of d + 1 permutations with the leading element being the identity permutation. It can be viewed as an alignment structure across d+1 sequences, or visualized as the result of permuting n hypercubes of (d+1) dimensions. We study the hierarchical decomposition of d-dimensional permutations. We show that when d ≥ 2, the ratio between non-decomposable or si...

The set of all permutations, ordered by pattern containment, forms a poset. This paper presents the first explicit major results on the topology of intervals in this poset. We show that almost all (open) intervals in this poset have a disconnected subinterval and are thus not shellable. Nevertheless, there seem to be large classes of intervals that are shellable and thus have the homotopy type ...