Logarithmic co-Higgs bundles

In this article, we introduce a notion of logarithmic co-Higgs sheaves associated with a simple normal crossing divisor on a projective manifold and show their existence with nilpotent co-Higgs fields for fixed ranks and second Chern classes. Then, we deal with various moduli problems involving logarithmic co-Higgs sheaves, such as coherent systems and holomorphic triples, specially over algebraic curves of low genus.