893 research outputs found
Kleene algebra with domain
We propose Kleene algebra with domain (KAD), an extension of Kleene algebra
with two equational axioms for a domain and a codomain operation, respectively.
KAD considerably augments the expressiveness of Kleene algebra, in particular
for the specification and analysis of state transition systems. We develop the
basic calculus, discuss some related theories and present the most important
models of KAD. We demonstrate applicability by two examples: First, an
algebraic reconstruction of Noethericity and well-foundedness; second, an
algebraic reconstruction of propositional Hoare logic.Comment: 40 page
New Representations of Matroids and Generalizations
We extend the notion of matroid representations by matrices over fields and
consider new representations of matroids by matrices over finite semirings,
more precisely over the boolean and the superboolean semirings. This idea of
representations is generalized naturally to include also hereditary
collections. We show that a matroid that can be directly decomposed as
matroids, each of which is representable over a field, has a boolean
representation, and more generally that any arbitrary hereditary collection is
superboolean-representable.Comment: 27 page
Convolution, Separation and Concurrency
A notion of convolution is presented in the context of formal power series
together with lifting constructions characterising algebras of such series,
which usually are quantales. A number of examples underpin the universality of
these constructions, the most prominent ones being separation logics, where
convolution is separating conjunction in an assertion quantale; interval
logics, where convolution is the chop operation; and stream interval functions,
where convolution is used for analysing the trajectories of dynamical or
real-time systems. A Hoare logic is constructed in a generic fashion on the
power series quantale, which applies to each of these examples. In many cases,
commutative notions of convolution have natural interpretations as concurrency
operations.Comment: 39 page
Weighted Pushdown Systems with Indexed Weight Domains
The reachability analysis of weighted pushdown systems is a very powerful
technique in verification and analysis of recursive programs. Each transition
rule of a weighted pushdown system is associated with an element of a bounded
semiring representing the weight of the rule. However, we have realized that
the restriction of the boundedness is too strict and the formulation of
weighted pushdown systems is not general enough for some applications. To
generalize weighted pushdown systems, we first introduce the notion of stack
signatures that summarize the effect of a computation of a pushdown system and
formulate pushdown systems as automata over the monoid of stack signatures. We
then generalize weighted pushdown systems by introducing semirings indexed by
the monoid and weaken the boundedness to local boundedness
Tropical Cramer Determinants Revisited
We prove general Cramer type theorems for linear systems over various
extensions of the tropical semiring, in which tropical numbers are enriched
with an information of multiplicity, sign, or argument. We obtain existence or
uniqueness results, which extend or refine earlier results of Gondran and
Minoux (1978), Plus (1990), Gaubert (1992), Richter-Gebert, Sturmfels and
Theobald (2005) and Izhakian and Rowen (2009). Computational issues are also
discussed; in particular, some of our proofs lead to Jacobi and Gauss-Seidel
type algorithms to solve linear systems in suitably extended tropical
semirings.Comment: 41 pages, 5 Figure
Supertropical linear algebra
The objective of this paper is to lay out the algebraic theory of
supertropical vector spaces and linear algebra, utilizing the key antisymmetric
relation of ``ghost surpasses.''Special attention is paid to the various
notions of ``base,'' which include d-base and s-base, and these are compared to
other treatments in the tropical theory. Whereas the number of elements in a
d-base may vary according to the d-base, it is shown that when an s-base
exists, it is unique up to permutation and multiplication by scalars, and can
be identified with a set of ``critical'' elements. Linear functionals and the
dual space are also studied, leading to supertropical bilinear forms and a
supertropical version of the Gram matrix, including its connection to linear
dependence, as well as a supertropical version of a theorem of Artin.Comment: 28 page
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