For a set A and a number n let F_n^A(x_1,...,x_n) =
A(x_1)\cdots A(x_n). We study how hard it is to approximate this
function in terms of the number of queries required. For a general
set A we have exact bounds that depend on functions from coding
theory. These are applied ... more >>>

In [Blass, Gurevich, and Shelah, 99] a logic L_Y has been introduced as a possible candidate for a logic capturing the PTIME properties of structures (even in the absence of an ordering of their universe). A reformulation of this problem in terms of a parameterized halting problem p-Acc for nondeterministic ... more >>>