Guest Piece for the Complexity Theory Column, edited by
Lane Hemaspaandra,
SIGACT NEWS 54
March, 2023, pp. 63--81.UPDATE, July, 2024: Alexey Milovanov has presented
a
solution to Open Problem 10, showing that there is a Universal Turing Machine defining
Kolmogorov complexity, such that the Halting Problem (and thus every computably-enumerable set)
is poly-time reducible to the Kolmogorov random strings.
UPDATE, February, 2026: Alexey Milovanov has
solved the other half of Open
Problem 10, showing that there is a Universal Turing Machine defining plain
Kolmogorov complexity, such that the Halting Problem
is NOT poly-time reducible to the Kolmogorov random strings.
UPDATE, August, 2026: Together with a co-author, Alexander Shekhovtsov has
presented solutions to Open Question 3 (by characterizing ACC0 in terms of small genus) and part of
Open Question 9 (by showing, nonconstructively, the existence of an irrational algebraic
number that is not in AC0).
6th Conference on Computability in Europe (CiE 2010),
Centre for Applied Mathematics and Information Technology,
Dept. of Mathematics, University of Azores, pp. 1--5, 2010.
(with Jia Jiao, Meena
Mahajan, and
V. Vinay),
Theoretical Computer Science Vol. 209, 1998, 47-86.
[NOTE:The proof of Theorem 7.12 is incorrect. See the discussion
of this here.]
This is a
revision and extension of
the paper Depth reduction for noncommutative arithmetic
circuits (with Jia Jiao), in Proc. 25th
STOC 1993, pp.
515-522.
(with Ulrich Hertrampf),
Information and Computation Vol. 112
1994, pp. 217-238. (This material appeared in preliminary form in
the papers A Note on the Power of Threshold Circuits
(FOCS
1989, pp. 580-584), and On the Power of Uniform Families of
Constant-Depth Threshold Circuits
(MFCS 1990, Lecture
Notes in Computer Science 452, pp. 158-164.))
in Kolmogorov Complexity and
Computational Complexity,
Osamu Watanabe,
editor, EATCS Monograph Series, Springer-Verlag, 1992, pp. 4-22.
Earlier versions of this work appeared in
Proc. AAAI Spring Symposium on the Theory and Application
of Minimal-Length Encoding, and in a paper entitled The Generalized
Kolmogorov Complexity of Sets, in
Proc.
4th IEEE Structure in Complexity Theory Conference, 1989.
(with Osamu
Watanabe),
Information and Computation Vol. 86
1990, pp. 160-178.
An earlier version appeared in
Proc. 3rd IEEE Structure in Complexity Theory Conference, 1988.
Journal of Computer and System Sciences Vol. 39, 1989, 101-124.
Special issue on IEEE Structure in Complexity Theory Conference 1987
(whose proceedings contain an abstract of this paper).
An earlier version
appeared in Proc. 19th
STOC, 1987, pp.
151-159.