5,341 research outputs found
On The Power of Tree Projections: Structural Tractability of Enumerating CSP Solutions
The problem of deciding whether CSP instances admit solutions has been deeply
studied in the literature, and several structural tractability results have
been derived so far. However, constraint satisfaction comes in practice as a
computation problem where the focus is either on finding one solution, or on
enumerating all solutions, possibly projected to some given set of output
variables. The paper investigates the structural tractability of the problem of
enumerating (possibly projected) solutions, where tractability means here
computable with polynomial delay (WPD), since in general exponentially many
solutions may be computed. A general framework based on the notion of tree
projection of hypergraphs is considered, which generalizes all known
decomposition methods. Tractability results have been obtained both for classes
of structures where output variables are part of their specification, and for
classes of structures where computability WPD must be ensured for any possible
set of output variables. These results are shown to be tight, by exhibiting
dichotomies for classes of structures having bounded arity and where the tree
decomposition method is considered
Intelligence student advising system - an implementation using object-oriented C++
This paper present an approach for developing a consistent student course-advising system for undergraduate students using knowledge-based technology. A prototype system has been implemented in object-oriented technique using C++. The prototype system was designed for undergraduate Computing students. The prototype is able to give consultation and advice on some important aspect of student advising problems. Knowledgeable behaviour was produced where the ‘expert’ and ‘knowledge’ is stored separately from the inference engine. Object-oriented programming technique was found to enhance the development of the system
Not Every Co-existential Map is Confluent
A continuous surjection between compacta is co-existential if it is the second of two maps whose composition is a standard ultracopower projection. Co-existential maps are always weakly confluent, and are even monotone when the range space is locally connected; so it is a natural question to ask whether they are always confluent. Here we give a negative answer. This is an interesting question, mainly because of the fact that most theorems about confluent maps have parallel versions for co-existential maps---notably, both kinds of maps preserve hereditary indecomposability. Where the known parallels break down is in the question of chainability. It is a celebrated open problem whether confluent maps preserve chainability, or even being a pseudo-arc; however, as has recently been shown, co-existential maps do indeed preserve both these properties
Sharp Trace Hardy-Sobolev-Maz'ya Inequalities and the Fractional Laplacian
In this work we establish trace Hardy and trace Hardy-Sobolev-Maz'ya
inequalities with best Hardy constants, for domains satisfying suitable
geometric assumptions such as mean convexity or convexity. We then use them to
produce fractional Hardy-Sobolev-Maz'ya inequalities with best Hardy constants
for various fractional Laplacians. In the case where the domain is the half
space our results cover the full range of the exponent of the
fractional Laplacians. We answer in particular an open problem raised by Frank
and Seiringer \cite{FS}.Comment: 42 page
On representing some lattices as lattices of intermediate subfactors of finite index
We prove that the very simple lattices which consist of a largest, a smallest
and pairwise incomparable elements where is a positive integer can be
realized as the lattices of intermediate subfactors of finite index and finite
depth. Using the same techniques, we give a necessary and sufficient condition
for subfactors coming from Loop groups of type at generic levels to be
maximal.Comment: 39 pages, latex, corrected proof of Cor. 5.23. To appear in Advance
in Mathematic
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