Regressive computations characterize logarithmic space

Unambiguous Logarithmic Space Bounded Computations

Computations in Space and Space in Computations

The emergence of terms like natural computing, mimetic computing, parallel problem solving from nature, bio-inspired computing, neurocomputing, evolutionary computing, etc., shows the never ending interest of the computer scientists for the use of “natural phenomena” as “problem solving devices” or more generally, as a fruitful source of inspiration to develop new programming paradigms. It is t...

Unification and Logarithmic Space

We present an algebraic characterization of the complexity classes Logspace and NLogspace, using an algebra with a composition law based on unification. This new bridge between unification and complexity classes is inspired from proof theory and more specifically linear logic and Geometry of Interaction. We show how unification can be used to build a model of computation by means of specific su...

On the Relation between Parallel Real-time Computations and Logarithmic Space

We show that all the problems solvable by a nondeterministic machine with logarithmic work space (NLOGSPACE) can be solved in real time by a parallel machine, no matter how tight the real-time constraints are. We also show that, once real-time constraints are dropped, several other real-time problems are in effect solvable in nondeterministic logarithmic space. Therefore, we conjecture that NLO...

Logarithmic Space and Permutations

In a recent work, Girard [1] proposed a new and innovative approach to computational complexity based on the proofs-as-programs correspondence. In a previous paper [2], the authors showed how Girard proposal succeeds in obtaining a new characterization of co-NL languages as a set of operators acting on a Hilbert Space. In this paper, we extend this work by showing that it is also possible to de...