393 research outputs found
Extensions of discrete classical orthogonal polynomials beyond the orthogonality
It is well known that the family of Hahn polynomials
is orthogonal with respect to a certain
weight function up to . In this paper we present a factorization for Hahn
polynomials for a degree higher than and we prove that these polynomials
can be characterized by a -Sobolev orthogonality.
We also present an analogous result for dual-Hahn, Krawtchouk, and Racah
polynomials and give the limit relations between them for all n\in \XX N_0.
Furthermore, in order to get this results for the Krawtchouk polynomials we
will get a more general property of orthogonality for Meixner polynomials.Comment: 2 figures, 20 page
A Survey on q-Polynomials and their Orthogonality Properties
In this paper we study the orthogonality conditions satisfied by the
classical q-orthogonal polynomials that are located at the top of the q-Hahn
tableau (big q-jacobi polynomials (bqJ)) and the Nikiforov-Uvarov tableau
(Askey-Wilson polynomials (AW)) for almost any complex value of the parameters
and for all non-negative integers degrees. We state the degenerate version of
Favard's theorem, which is one of the keys of the paper, that allow us to
extend the orthogonality properties valid up to some integer degree N to
Sobolev type orthogonality properties. We also present, following an analogous
process that applied in [16], tables with the factorization and the discrete
Sobolev-type orthogonality property for those families which satisfy a finite
orthogonality property, i.e. it consists in sum of finite number of masspoints,
such as q-Racah (qR), q-Hahn (qH), dual q-Hahn (dqH), and q-Krawtchouk
polynomials (qK), among others.
-- [16] R. S. Costas-Santos and J. F. Sanchez-Lara. Extensions of discrete
classical orthogonal polynomials beyond the orthogonality. J. Comp. Appl.
Math., 225(2) (2009), 440-451Comment: 3 Figures, 3 tables, in a 22 pages manuscrip
Biopesticide activity from drimanic compounds to control tomato pathogens
IndexaciĂłn: Scopus.Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 ÎŒg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 ÎŒg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens. © 2018 by the authors.https://www.mdpi.com/1420-3049/23/8/205
The Complexity of Nash Equilibria in Simple Stochastic Multiplayer Games
We analyse the computational complexity of finding Nash equilibria in simple
stochastic multiplayer games. We show that restricting the search space to
equilibria whose payoffs fall into a certain interval may lead to
undecidability. In particular, we prove that the following problem is
undecidable: Given a game G, does there exist a pure-strategy Nash equilibrium
of G where player 0 wins with probability 1. Moreover, this problem remains
undecidable if it is restricted to strategies with (unbounded) finite memory.
However, if mixed strategies are allowed, decidability remains an open problem.
One way to obtain a provably decidable variant of the problem is restricting
the strategies to be positional or stationary. For the complexity of these two
problems, we obtain a common lower bound of NP and upper bounds of NP and
PSPACE respectively.Comment: 23 pages; revised versio
Not so different after all: Properties and spatial structure of column density peaks in the pipe and Orion A clouds
We present a comparative study of the physical properties and the spatial distribution of column density peaks in two giant molecular clouds (GMCs), the Pipe Nebula and Orion A, which exemplify opposite cases of star cluster formation stages. The density peaks were extracted from dust extinction maps constructed from Herschel/SPIRE far-infrared images. We compare the distribution functions for dust temperature, mass, equivalent radius, and mean volume density of peaks in both clouds, and made a more fair comparison by isolating the less active Tail region in Orion A and by convolving the Pipe Nebula map to simulate placing it at a distance similar to that of the Orion Complex. The peak mass distributions for Orion A, the Tail, and the convolved Pipe have similar ranges, sharing a maximum near 5 M and a similar power-law drop above 10 M. Despite the clearly distinct evolutive stage of the clouds, there are very important similarities in the physical and spatial distribution properties of the column density peaks, pointing to a scenario where they form as a result of uniform fragmentation of filamentary structures across the various scales of the cloud, with density being the parameter leading the fragmentation, and with clustering being a direct result of thermal fragmentation at different spatial scales. Our work strongly supports the idea that the formation of clusters in GMC could be the result of the primordial organization of pre-stellar material
Algorithms for Game Metrics
Simulation and bisimulation metrics for stochastic systems provide a
quantitative generalization of the classical simulation and bisimulation
relations. These metrics capture the similarity of states with respect to
quantitative specifications written in the quantitative {\mu}-calculus and
related probabilistic logics. We first show that the metrics provide a bound
for the difference in long-run average and discounted average behavior across
states, indicating that the metrics can be used both in system verification,
and in performance evaluation. For turn-based games and MDPs, we provide a
polynomial-time algorithm for the computation of the one-step metric distance
between states. The algorithm is based on linear programming; it improves on
the previous known exponential-time algorithm based on a reduction to the
theory of reals. We then present PSPACE algorithms for both the decision
problem and the problem of approximating the metric distance between two
states, matching the best known algorithms for Markov chains. For the
bisimulation kernel of the metric our algorithm works in time O(n^4) for both
turn-based games and MDPs; improving the previously best known O(n^9\cdot
log(n)) time algorithm for MDPs. For a concurrent game G, we show that
computing the exact distance between states is at least as hard as computing
the value of concurrent reachability games and the square-root-sum problem in
computational geometry. We show that checking whether the metric distance is
bounded by a rational r, can be done via a reduction to the theory of real
closed fields, involving a formula with three quantifier alternations, yielding
O(|G|^O(|G|^5)) time complexity, improving the previously known reduction,
which yielded O(|G|^O(|G|^7)) time complexity. These algorithms can be iterated
to approximate the metrics using binary search.Comment: 27 pages. Full version of the paper accepted at FSTTCS 200
Blackwell-Optimal Strategies in Priority Mean-Payoff Games
We examine perfect information stochastic mean-payoff games - a class of
games containing as special sub-classes the usual mean-payoff games and parity
games. We show that deterministic memoryless strategies that are optimal for
discounted games with state-dependent discount factors close to 1 are optimal
for priority mean-payoff games establishing a strong link between these two
classes
Decision Problems for Nash Equilibria in Stochastic Games
We analyse the computational complexity of finding Nash equilibria in
stochastic multiplayer games with -regular objectives. While the
existence of an equilibrium whose payoff falls into a certain interval may be
undecidable, we single out several decidable restrictions of the problem.
First, restricting the search space to stationary, or pure stationary,
equilibria results in problems that are typically contained in PSPACE and NP,
respectively. Second, we show that the existence of an equilibrium with a
binary payoff (i.e. an equilibrium where each player either wins or loses with
probability 1) is decidable. We also establish that the existence of a Nash
equilibrium with a certain binary payoff entails the existence of an
equilibrium with the same payoff in pure, finite-state strategies.Comment: 22 pages, revised versio
Deterministic Priority Mean-payoff Games as Limits of Discounted Games
International audienceInspired by the paper of de Alfaro, Henzinger and Majumdar about discounted -calculus we show new surprising links between parity games and different classes of discounted games
Anomalous Commutator Algebra for Conformal Quantum Mechanics
The structure of the commutator algebra for conformal quantum mechanics is
considered. Specifically, it is shown that the emergence of a dimensional scale
by renormalization implies the existence of an anomaly or quantum-mechanical
symmetry breaking, which is explicitly displayed at the level of the generators
of the SO(2,1) conformal group. Correspondingly, the associated breakdown of
the conservation of the dilation and special conformal charges is derived.Comment: 23 pages. A few typos corrected in the final version (which agrees
with the published Phys. Rev. D article
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