2,884 research outputs found
Circular Languages Generated by Complete Splicing Systems and Pure Unitary Languages
Circular splicing systems are a formal model of a generative mechanism of
circular words, inspired by a recombinant behaviour of circular DNA. Some
unanswered questions are related to the computational power of such systems,
and finding a characterization of the class of circular languages generated by
circular splicing systems is still an open problem. In this paper we solve this
problem for complete systems, which are special finite circular splicing
systems. We show that a circular language L is generated by a complete system
if and only if the set Lin(L) of all words corresponding to L is a pure unitary
language generated by a set closed under the conjugacy relation. The class of
pure unitary languages was introduced by A. Ehrenfeucht, D. Haussler, G.
Rozenberg in 1983, as a subclass of the class of context-free languages,
together with a characterization of regular pure unitary languages by means of
a decidable property. As a direct consequence, we characterize (regular)
circular languages generated by complete systems. We can also decide whether
the language generated by a complete system is regular. Finally, we point out
that complete systems have the same computational power as finite simple
systems, an easy type of circular splicing system defined in the literature
from the very beginning, when only one rule is allowed. From our results on
complete systems, it follows that finite simple systems generate a class of
context-free languages containing non-regular languages, showing the
incorrectness of a longstanding result on simple systems
Combining Insertion and Deletion in RNA-editing Preserves Regularity
Inspired by RNA-editing as occurs in transcriptional processes in the living
cell, we introduce an abstract notion of string adjustment, called guided
rewriting. This formalism allows simultaneously inserting and deleting
elements. We prove that guided rewriting preserves regularity: for every
regular language its closure under guided rewriting is regular too. This
contrasts an earlier abstraction of RNA-editing separating insertion and
deletion for which it was proved that regularity is not preserved. The
particular automaton construction here relies on an auxiliary notion of slice
sequence which enables to sweep from left to right through a completed rewrite
sequence.Comment: In Proceedings MeCBIC 2012, arXiv:1211.347
Polyfolds: A First and Second Look
Polyfold theory was developed by Hofer-Wysocki-Zehnder by finding
commonalities in the analytic framework for a variety of geometric elliptic
PDEs, in particular moduli spaces of pseudoholomorphic curves. It aims to
systematically address the common difficulties of compactification and
transversality with a new notion of smoothness on Banach spaces, new local
models for differential geometry, and a nonlinear Fredholm theory in the new
context. We shine meta-mathematical light on the bigger picture and core ideas
of this theory. In addition, we compiled and condensed the core definitions and
theorems of polyfold theory into a streamlined exposition, and outline their
application at the example of Morse theory.Comment: 62 pages, 2 figures. Example 2.1.3 has been modified. Final version,
to appear in the EMS Surv. Math. Sc
Splicing Systems from Past to Future: Old and New Challenges
A splicing system is a formal model of a recombinant behaviour of sets of
double stranded DNA molecules when acted on by restriction enzymes and ligase.
In this survey we will concentrate on a specific behaviour of a type of
splicing systems, introduced by P\u{a}un and subsequently developed by many
researchers in both linear and circular case of splicing definition. In
particular, we will present recent results on this topic and how they stimulate
new challenging investigations.Comment: Appeared in: Discrete Mathematics and Computer Science. Papers in
Memoriam Alexandru Mateescu (1952-2005). The Publishing House of the Romanian
Academy, 2014. arXiv admin note: text overlap with arXiv:1112.4897 by other
author
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