Reversible simulation of space-bounded computations

Unambiguous Logarithmic Space Bounded Computations

On the Derandomization of Space-Bounded Computations

Some Observations about Relativization of Space Bounded Computations

In this column we explore what relativization says about space bounded computations and what recent results about space bounded computations say about relativization. There is a strong belief in computational complexity circles that problems which can be relativized in two contradictory ways are very hard to solve. We believe that such problems can only be solved by proof techniques that do not...

Alternative Notions of Approximation and Space-Bounded Computations

We investigate alternative notions of approximation for problems inside P (deterministic polynomial time), and show that even a slightly nontrivial information about a problem may be as hard to obtain as the solution itself. For example, we prove that if one could eliminate even a single possibility for the value of an arithmetic circuit on a given input, then this would imply that the class P ...

Reversible space-time simulation of cellular automata

We brieey recall the deenitions of Cellular automata (ca), simulation, re-versibility and Partitioned cellular automata (pca) as deened by Morita. We call the sequence of the iterated conngurations of a connguration a space-time diagram. We deene an embedding relation between space-time diagrams and a space-time simulation relation between ca. We built a space-time simulation of any ca by a rev...