(a) When the ideal I=m1,m2,…,mk for a constant k, we can test whether fI in randomized polynomial time. This result holds even for f given by a black-box, when f is of small degree.
(b) When I=m1,m2,…,mk for a constant is computed by a ΣΠΣ circuit with output gate of bounded fanin, we can test whether fI in deterministic polynomial time. This generalizes the Kayal–Saxena result [11] of deterministic polynomial-time identity testing for ΣΠΣ circuits with bounded fanin output gate.
(c) When k is not constant the problem is coNP-hard. We also show that the problem is upper bounded by coMAPP over the field of rationals, and by coNPModpP over finite fields.
(d) Finally, we discuss identity testing for certain restricted depth 4 arithmetic circuits.
For ideals I=f1,…,fℓ where each fiF[x1,…,xk] is an arbitrary polynomial but k is a constant, we show similar results as (a) and (b) above.