K. Lakshmanan

Bio: K. Lakshmanan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Context-sensitive grammar & Tree-adjoining grammar. The author has an hindex of 2, co-authored 2 publications receiving 15 citations.

On the Power of P Systems with Contextual Rules

Abstract: We consider P Systems with string objects which evolve by means of one-sided contextual rules and erasing contextual rules. The generative power of these systems with three or less than three membranes is investigated. We show that systems with three membranes characterize the family of recursively enumerable languages. When the string replication is used in one-sided contextual rules, these systems are able of solving NP-complete problems in linear time: this is exemplified with SAT and HPP.

On some classes of contextual grammars

Abstract: In this paper, we introduce some new variants of contextual grammars and investigate their generative power. We'consider a restricted version of depth-first contextual grammars, which depends on length of the inserting contexts. Using this variant, we give a solution to the open problem P14 listed in [8]. We also introduce random context contextual grammars and compare its generative power with the families IC , ICC , EC , ECC , TC . Time-varying contextual grammars are introduced which resemble time-varying grammars. We compare the generative power of this variant with the families of internal, external, total, matrix, and programmed contextual grammars.

P Systems with Activated/Prohibited Membrane Channels

Abstract: We investigate a variant of purely communicating P systems, where multisets of activators can open channels for certain objects to pass through membranes in one direction; however, the permeability of a channel can be controlled by multisets of prohibitors, too.We will show that for such systems with only one membrane and using only singleton activator and prohibitor sets, we already obtain universal computational power. When using systems with activating multisets for membrane channels only, we obtain a similar result. By showing a close correspondence to P systems with symport/antiport as introduced in [13] we can optimize some results given there.

Tracing Some Open Problems in Membrane Computing

Abstract: Membrane computing is a branch of natural computing aiming to abstract computing models from the structure and functioning of the living cell, and from the way cells cooperate in tissues, organs, or other populations of cells. This research area developed very fast, both at the theoretical level and in what concerns the applications. During the almost ten years since membrane computing was initiated, several open problems were circulated, sometimes in comprehensive lists prepared for meetings in this area. The present notes intend to survey the research related to some of these problems, mentioning both progresses made in solving them and questions which still wait for research efiorts.

Contextual Grammars with Subregular Choice

Abstract: We discuss external contextual grammars with choice where the choice language belongs to a family of subregular languages. We determine the hierarchy of language families of contextual languages which is obtained by the use of nilpotent, combinational, definite, regular suffix closed, and regular commutative languages as choice languages.

Further Results on Contextual and Rewriting P Systems

Abstract: In this paper, we continue the study of contextual and rewriting P systems. In contextual P systems, we improve a universality result avoiding the extended feature and by using rules of small weight. In rewriting P systems, we have two (rather surprising) universality results, both of them using three membranes, for non-extended systems with replicated rewriting and with leftmost rewriting, respectively.