138 research outputs found
Graph Spectral Properties of Deterministic Finite Automata
We prove that a minimal automaton has a minimal adjacency matrix rank and a
minimal adjacency matrix nullity using equitable partition (from graph spectra
theory) and Nerode partition (from automata theory). This result naturally
introduces the notion of matrix rank into a regular language L, the minimal
adjacency matrix rank of a deterministic automaton that recognises L. We then
define and focus on rank-one languages: the class of languages for which the
rank of minimal automaton is one. We also define the expanded canonical
automaton of a rank-one language.Comment: This paper has been accepted at the following conference: 18th
International Conference on Developments in Language Theory (DLT 2014),
August 26 - 29, 2014, Ekaterinburg, Russi
Annotated nonmonotonic rule systems
AbstractAnnotated logics were proposed by Subrahmanian as a unified paradigm for representing a wide variety of reasoning tasks including reasoning with uncertainty within a single theoretical framework. Subsequently, Marek, Nerode and Remmel have shown how to provide nonmonotonic extensions of arbitrary languages through their notion of a nonmonotonic rule systems. The primary aim of this paper is to define annotated nonmonotonic rule systems which merge these two frameworks into a general purpose nonmonotonic reasoning framework over arbitrary multiple-valued logics. We then show how Reiter's normal default theories may be generalized to the framework of annotated nonmonotonic rule systems
Extracting winning strategies in update games
This paper investigates algorithms for extracting winning strategies in two-player games played on nite graphs. We focus on a special class of games called update games. We present a procedure for extracting winning strategies in update games by constructing strategies explicitly. This is based on an algorithm that solves update games in quadratic time. We also show that solving update games with a bounded number of nondeterministic nodes takes linear time
Unstable Attractors: Existence and Robustness in Networks of Oscillators With Delayed Pulse Coupling
We consider unstable attractors; Milnor attractors such that, for some
neighbourhood of , almost all initial conditions leave . Previous
research strongly suggests that unstable attractors exist and even occur
robustly (i.e. for open sets of parameter values) in a system modelling
biological phenomena, namely in globally coupled oscillators with delayed pulse
interactions.
In the first part of this paper we give a rigorous definition of unstable
attractors for general dynamical systems. We classify unstable attractors into
two types, depending on whether or not there is a neighbourhood of the
attractor that intersects the basin in a set of positive measure. We give
examples of both types of unstable attractor; these examples have
non-invertible dynamics that collapse certain open sets onto stable manifolds
of saddle orbits.
In the second part we give the first rigorous demonstration of existence and
robust occurrence of unstable attractors in a network of oscillators with
delayed pulse coupling. Although such systems are technically hybrid systems of
delay differential equations with discontinuous `firing' events, we show that
their dynamics reduces to a finite dimensional hybrid system system after a
finite time and hence we can discuss Milnor attractors for this reduced finite
dimensional system. We prove that for an open set of phase resetting functions
there are saddle periodic orbits that are unstable attractors.Comment: 29 pages, 8 figures,submitted to Nonlinearit
Finitely generated free Heyting algebras via Birkhoff duality and coalgebra
Algebras axiomatized entirely by rank 1 axioms are algebras for a functor and
thus the free algebras can be obtained by a direct limit process. Dually, the
final coalgebras can be obtained by an inverse limit process. In order to
explore the limits of this method we look at Heyting algebras which have mixed
rank 0-1 axiomatizations. We will see that Heyting algebras are special in that
they are almost rank 1 axiomatized and can be handled by a slight variant of
the rank 1 coalgebraic methods
Quotient Complexity of Regular Languages
The past research on the state complexity of operations on regular languages
is examined, and a new approach based on an old method (derivatives of regular
expressions) is presented. Since state complexity is a property of a language,
it is appropriate to define it in formal-language terms as the number of
distinct quotients of the language, and to call it "quotient complexity". The
problem of finding the quotient complexity of a language f(K,L) is considered,
where K and L are regular languages and f is a regular operation, for example,
union or concatenation. Since quotients can be represented by derivatives, one
can find a formula for the typical quotient of f(K,L) in terms of the quotients
of K and L. To obtain an upper bound on the number of quotients of f(K,L) all
one has to do is count how many such quotients are possible, and this makes
automaton constructions unnecessary. The advantages of this point of view are
illustrated by many examples. Moreover, new general observations are presented
to help in the estimation of the upper bounds on quotient complexity of regular
operations
Reverse mathematics of matroids
Matroids generalize the familiar notion of linear dependence from linear algebra. Following a brief discussion of founding work in computability and matroids, we use the techniques of reverse mathematics to determine the logical strength of some basis theorems for matroids and enumerated matroids. Next, using Weihrauch reducibility, we relate the basis results to combinatorial choice principles and statements about vector spaces. Finally, we formalize some of the Weihrauch reductions to extract related reverse mathematics results. In particular, we show that the existence of bases for vector spaces of bounded dimension is equivalent to the induction scheme for \Sigma^0_2 formulas
Parameterized Synthesis with Safety Properties
Parameterized synthesis offers a solution to the problem of constructing
correct and verified controllers for parameterized systems. Such systems occur
naturally in practice (e.g., in the form of distributed protocols where the
amount of processes is often unknown at design time and the protocol must work
regardless of the number of processes). In this paper, we present a novel
learning based approach to the synthesis of reactive controllers for
parameterized systems from safety specifications. We use the framework of
regular model checking to model the synthesis problem as an infinite-duration
two-player game and show how one can utilize Angluin's well-known L* algorithm
to learn correct-by-design controllers. This approach results in a synthesis
procedure that is conceptually simpler than existing synthesis methods with a
completeness guarantee, whenever a winning strategy can be expressed by a
regular set. We have implemented our algorithm in a tool called L*-PSynth and
have demonstrated its performance on a range of benchmarks, including robotic
motion planning and distributed protocols. Despite the simplicity of L*-PSynth
it competes well against (and in many cases even outperforms) the
state-of-the-art tools for synthesizing parameterized systems.Comment: 18 page
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