Computing the Homology Functor on Semi-algebraic Maps and Diagrams.

Developing an algorithm for computing the Betti numbers of semi-algebraic sets with singly exponential complexity has been a holy grail in algorithmic semi-algebraic geometry and only partial results are known. In this paper we consider the more general problem of computing the image under the homology functor of a continuous semi-algebraic map f : X → Y between closed and bounded semi-algebraic sets. For every fixed ℓ ≥ 0 we give an algorithm with singly exponential complexity that computes bases of the homology groups H i (X) , H i (Y) (with rational coefficients) and a matrix with respect to these bases of the induced linear maps H i (f) : H i (X) → H i (Y) , 0 ≤ i ≤ ℓ . We generalize this algorithm to more general (zigzag) diagrams of continuous semi-algebraic maps between closed and bounded semi-algebraic sets and give a singly exponential algorithm for computing the homology functors on such diagrams. This allows us to give an algorithm with singly exponential complexity for computing barcodes of semi-algebraic zigzag persistent homology in small dimensions. [ABSTRACT FROM AUTHOR]