424,019 research outputs found
Solving equations in the relational algebra
Enumerating all solutions of a relational algebra equation is a natural and
powerful operation which, when added as a query language primitive to the
nested relational algebra, yields a query language for nested relational
databases, equivalent to the well-known powerset algebra. We study
\emph{sparse} equations, which are equations with at most polynomially many
solutions. We look at their complexity, and compare their expressive power with
that of similar notions in the powerset algebra.Comment: Minor revision, accepted for publication in SIAM Journal on Computin
Efficient Solution of Language Equations Using Partitioned Representations
A class of discrete event synthesis problems can be reduced to solving
language equations f . X ⊆ S, where F is the fixed component and S the
specification. Sequential synthesis deals with FSMs when the automata for F and
S are prefix closed, and are naturally represented by multi-level networks with
latches. For this special case, we present an efficient computation, using
partitioned representations, of the most general prefix-closed solution of the
above class of language equations. The transition and the output relations of
the FSMs for F and S in their partitioned form are represented by the sets of
output and next state functions of the corresponding networks. Experimentally,
we show that using partitioned representations is much faster than using
monolithic representations, as well as applicable to larger problem instances.Comment: Submitted on behalf of EDAA (http://www.edaa.com/
Representing a P-complete problem by small trellis automata
A restricted case of the Circuit Value Problem known as the Sequential NOR
Circuit Value Problem was recently used to obtain very succinct examples of
conjunctive grammars, Boolean grammars and language equations representing
P-complete languages (Okhotin, http://dx.doi.org/10.1007/978-3-540-74593-8_23
"A simple P-complete problem and its representations by language equations",
MCU 2007). In this paper, a new encoding of the same problem is proposed, and a
trellis automaton (one-way real-time cellular automaton) with 11 states solving
this problem is constructed
Automated code generation for discontinuous Galerkin methods
A compiler approach for generating low-level computer code from high-level
input for discontinuous Galerkin finite element forms is presented. The input
language mirrors conventional mathematical notation, and the compiler generates
efficient code in a standard programming language. This facilitates the rapid
generation of efficient code for general equations in varying spatial
dimensions. Key concepts underlying the compiler approach and the automated
generation of computer code are elaborated. The approach is demonstrated for a
range of common problems, including the Poisson, biharmonic,
advection--diffusion and Stokes equations
Free Variables and the Two Matrix Model
We study the full set of planar Green's functions for a two-matrix model
using the language of functions of non-commuting variables. Both the standard
Schwinger-Dyson equations and equations determining connected Green's functions
can be efficiently discussed and solved. This solution determines the master
field for the model in the `-representation.'Comment: 8 pages, harvma
Branes from a non-Abelian (2,0) tensor multiplet with 3-algebra
In this paper, we study the equations of motion for non-Abelian N=(2,0)
tensor multiplets in six dimensions, which were recently proposed by Lambert
and Papageorgakis. Some equations are regarded as constraint equations. We
employ a loop extension of the Lorentzian three-algebra (3-algebra) and examine
the equations of motion around various solutions of the constraint equations.
The resultant equations take forms that allow Lagrangian descriptions. We find
various (5+d)-dimensional Lagrangians and investigate the relation between them
from the viewpoint of M-theory duality.Comment: 44+1 pages, reference added, typos corrected, and several discussions
added; v3, reference added, many typos corrected, the language improved; v4,
some typos and references corrected, final version to appear in J. Phys.
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