#### Filter Results:

- Full text PDF available (47)

#### Publication Year

1993

2016

- This year (0)
- Last 5 years (4)
- Last 10 years (18)

#### Publication Type

#### Co-author

#### Journals and Conferences

#### Key Phrases

Learn More

- Hermann Gruber, Jan Johannsen
- FoSSaCS
- 2008

The problem of converting deterministic finite automata into (short) regular expressions is considered. It is known that the required expression size is 2 in the worst case for infinite languages, and for finite languages it is n log n) and n, if the alphabet size grows with the number of states n of the given automaton. A new lower bound method based on… (More)

- Michael Alekhnovich, Jan Johannsen, Toniann Pitassi, Alasdair Urquhart
- Electronic Colloquium on Computational Complexity
- 2001

Two distinct proofs of an exponential separation between regular resolution and unrestricted resolution are given. The previous best known separation between these systems was quasi-polynomial.

- Maria Luisa Bonet, Juan Luis Esteban, Nicola Galesi, Jan Johannsen
- SIAM J. Comput.
- 2000

An exponential lower bound for the size of tree-like Cutting Planes refutations of a certain family of CNF formulas with polynomial size resolution refutations is proved. This implies an exponential separation between the tree-like versions and the dag-like versions of resolution and Cutting Planes. In both cases only superpolynomial separations were known… (More)

We prove an exponential lower bound for tree-like Cutting Planes refutations of a set of clauses which has polynomial size resolution refutations. This implies an exponential separation between tree-like and dag-like proofs for both CuttingPlanes and resolution; in both cases only superpolynomial separations were known before [30, 20, 10]. In order to prove… (More)

- Jan Johannsen, Martin Lange
- ICALP
- 2003

We show that the satisfiability problem for CTL, the branching time logic that allows boolean combinations of path formulas inside a path quantifier but no nesting of them, is 2-EXPTIME-hard. The construction is inspired by Vardi and Stockmeyer’s 2-EXPTIME-hardness proof of CTL∗’s satisfiability problem. As a consequence, there is no subexponential… (More)

- Jan Johannsen
- Kurt Gödel Colloquium
- 1993

- Jan Johannsen
- 1996

We deene an extension R 0 2 of the bounded arithmetic theory R 0 2 and show that the class of functions b 1-deenable in R 0 2 coincides with the computational complexity class TC 0 of functions computable by polynomial size, constant depth threshold circuits.

We define theories of Bounded Arithmetic characterizing classes of functions computable by constantdepth threshold circuits of polynomial and quasipolynomial size. Then we define certain second-order theories and show that they characterize the functions in the Counting Hierarchy. Finally we show that the former theories are isomorphic to the latter via the… (More)

- Jan Johannsen
- Electronic Colloquium on Computational Complexity
- 1997

Using a notion of real communication complexity recently introduced by J. Kraj cek, we prove a lower bound on the depth of monotone real circuits and the size of monotone real formulas for st-connectivity. This implies a super-polynomial speed-up of dag-like over tree-like Cutting Planes proofs.

- Jan Johannsen, Chris Pollett
- LICS
- 1998

We deene theories of Bounded Arithmetic characterizing classes of functions computable by constant-depth threshold circuits of polynomial and quasipoly-nomial size. Then we deene certain second-order theories and show that they characterize the functions in the Counting Hierarchy. Finally we show that the former theories are isomorphic to the latter via the… (More)