## Invited Paper: Some Decision Problems of Enormous Complexity (at LICS 1999)

**Harvey M. Friedman**

### Abstract

We present some new decision and comparison problems of unusually high computational complexity. Most of the problems are strictly combinatorial in nature; others involve basic logical notions. Their complexities range from iterated exponential time completeness to \mathtime completeness to \mathtime completeness to \mathtime completeness. These three ordinals are well known ordinals from proof theory, and their associated complexity classes represent new levels of computational complexity for natural decision problems. Proofs will appear in an extended version of this manuscript to be published elsewhere.

### BibTeX

@InProceedings{Friedman-SomeDecisionProblem, author = {Harvey M. Friedman}, title = {Some Decision Problems of Enormous Complexity}, booktitle = {Proceedings of the Fourteenth Annual IEEE Symposium on Logic in Computer Science (LICS 1999)}, year = {1999}, month = {July}, pages = {2--12}, location = {Trento, Italy}, note = {Invited Talk}, publisher = {IEEE Computer Society Press} }