15,435 research outputs found
Detecting palindromes, patterns, and borders in regular languages
Given a language L and a nondeterministic finite automaton M, we consider
whether we can determine efficiently (in the size of M) if M accepts at least
one word in L, or infinitely many words. Given that M accepts at least one word
in L, we consider how long a shortest word can be. The languages L that we
examine include the palindromes, the non-palindromes, the k-powers, the
non-k-powers, the powers, the non-powers (also called primitive words), the
words matching a general pattern, the bordered words, and the unbordered words.Comment: Full version of a paper submitted to LATA 2008. This is a new version
with John Loftus added as a co-author and containing new results on
unbordered word
Limits of Baumslag-Solitar groups and dimension estimates in the space of marked groups
We prove that the limits of Baumslag-Solitar groups which we previously
studied are non-linear hopfian C*-simple groups with infinitely many twisted
conjugacy classes. We exhibit infinite presentations for these groups, classify
them up to group isomorphism, describe their automorphisms and discuss the word
and conjugacy problems. Finally, we prove that the set of these groups has
non-zero Hausforff dimension in the space of marked groups on two generators.Comment: 30 pages, no figures, englis
Beauty, elegance, grace, and sexiness compared
Beauty is the single most frequently and most broadly used aesthetic virtue term. The present study aimed at providing higher conceptual resolution to the broader notion of beauty by comparing it with three closely related aesthetically evaluative concepts which are likewise lexicalized across many languages: elegance, grace(fulness), and sexiness. We administered a variety of questionnaires that targeted perceptual qualia, cognitive and affective evaluations, as well as specific object properties that are associated with beauty, elegance, grace, and sexiness in personal looks, movements, objects of design, and other domains. This allowed us to reveal distinct and highly nuanced profiles of how a beautiful, elegant, graceful, and sexy appearance is subjectively perceived. As aesthetics is all about nuances, the fine-grained conceptual analysis of the four target concepts of our study provides crucial distinctions for future research
A Chomsky-SchĂĽtzenberger-Stanley type characterization of the class of slender context-free languages
Slender context-free languages have a complete algebraic characterization by L. Ilie in [13]. In this paper we give another characterization of this class of languages. In particular, using linear Dyck languages instead of unrestricted ones, we obtain a Chomsky-SchĂĽtzenberger-Stanley type characterization of slender context-free languages
On the Commutative Equivalence of Context-Free Languages
The problem of the commutative equivalence of context-free and regular languages is studied. In particular conditions ensuring that a context-free language of exponential growth is commutatively equivalent with a regular language are investigated
Unusual algorithms for lexicographical enumeration
Using well-known results, we consider algorithms for finding minimal words of given length n in regular and context-free languages. We also show algorithms enumerating the words of given length n of regular and contextfree languages in lexicographical order
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