Summary: SIGACT News Complexity Theory Column 40
Lane A. Hemaspaandra
Dept. of Computer Science, University of Rochester
Rochester, NY 14627, USA email@example.com
Introduction to Complexity Theory Column 40
Aduri Pavan very kindly stepped in, after a last-minute guest column cancellation, to write the
present article. Warmest thanks to him.
Upcoming issues will contain articles by (all topics/titles are of course tentative): M. Li´skiewicz,
M. Ogihara, and S. Toda on "Counting Paths in Some Regular Graphs--Old and New Stories"; by
E. B¨ohler, N. Creignou, S. Reith, and H. Vollmer on complexity-theoretic applications of Post's Lat-
tice; by V. Guruswami on codes and expanders; by A. Ambainis (topic TBA); and by J. Hitchcock,
J. Lutz, and E. Mayordomo on "The Fractal Geometry of Complexity Classes."
Guest Column: Comparison of Reductions and Completeness
We study the question of whether various polynomial-time reductions and the com-
pleteness notions differ in NP. We mention known results and give some proof ideas.
Reductions translate instances of one problem to instances of another problem. The crucial notion of