Intersection Numbers For Subspace Designs

t-Designs with few intersection numbers

Pott, A. and M. Shriklande, t-Designs with few intersection numbers, Discrete Mathematics 90 (1991) 215-217. We give a method to obtain new i-designs from t-designs with j distinct intersection numbers if i + j 1 does not exceed t.

Block Intersection Numbers of Block Designs Ii

A Note on t-designs with t Intersection Numbers

Let X be a finite set of v elements, called points, and let β be a finite family of distinct k-subsets of X , called blocks. Then the pair D = (X ,β) is called a t-design with parameters (v,k,λ) if any t-subset of X is contained in exactly λ members of β. If λi denotes the number of blocks containing i points, i = 0,1,2, . . . , t−1, then λi is independent of the choice of the i points and λi (...

Virtual Intersection Numbers

Intersection homology Betti numbers

A generalization of the formula of Fine and Rao for the ranks of the intersection homology groups of a complex algebraic variety is given. The proof uses geometric properties of intersection homology and mixed Hodge theory. The middle-perversity intersection homology with integral coefficients of a compact complex n-dimensional algebraic variety X with isolated singularities is well known to be...