The notion of promise problems was introduced and initially studied
by Even, Selman and Yacobi
(Information and Control, Vol.~61, pages 159-173, 1984).
In this article we survey some of the applications that this
notion has found in the twenty years that elapsed.
These include the notion ... more >>>

We introduce ``minimal'' two--sorted first--order theories VL, VSL, VNL and VP
that characterize the classes L, SL, NL and P in the same
way that Buss's $S^i_2$ hierarchy characterizes the polynomial time hierarchy.
Our theories arise from natural combinatorial problems, namely the st-Connectivity
Problem and the Circuit Value Problem.
It ... more >>>

Matroid intersection has a known polynomial time algorithm using an
oracle. We generalize this result to delta-matroids that do not have
equality as a restriction, and give a polynomial time algorithm for
delta-matroid intersection on delta-matroids without equality using an
oracle. We note that when equality is present, delta-matroid intersection
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