On the activities of pp-basis of matroid perspectives

There is a renewed interest in matroid perspectives, either for their relevance in other fields of combinatorics and topology, or their applications in engineering. But, like for most of the Tutte invariants, computing the Tutte polynomial of matroid perspectives is #P-hard. Hence the importance of results whose applications would help to speed up computations. In the present paper, we show that a pseudobasis of a matroid perspective can be decomposed by a cyclic flat into two subsets, one of which has zero internal activity and the other has zero external activity. Apart from its own interest in understanding the internal structures of matroid perspective, this decomposition allows an expansion of the Tutte polynomial of matroid perspective over cyclic flats. This can be used to speed up the computation of various evaluations of the polynomial.