1,372 research outputs found
A map on the space of rational functions
We describe dynamical properties of a map defined on the space
of rational functions. The fixed points of are classified and
the long time behavior of a subclass is described in terms of Eulerian
polynomials
Characterization of the Vertices and Extreme Directions of the Negative Cycles Polyhedron and Hardness of Generating Vertices of 0/1-Polyhedra
Given a graph and a weight function on the edges w:E\mapsto\RR, we consider the polyhedron of negative-weight flows on , and get a complete characterization of the vertices and extreme directions of . As a corollary, we show that, unless , there is no output polynomial-time algorithm to generate all the vertices of a 0/1-polyhedron. This strengthens the NP-hardness result of Khachiyan et al. (2006) for non 0/1-polyhedra, and comes in contrast with the polynomiality of vertex enumeration for 0/1-polytopes \cite{BL98} [Bussieck and L\"ubbecke (1998)]
Lambda Polarization in Polarized Proton-Proton Collisions at RHIC
We discuss Lambda polarization in semi-inclusive proton-proton collisions,
with one of the protons longitudinally polarized. The hyperfine interaction
responsible for the - and - mass splittings gives
rise to flavor asymmetric fragmentation functions and to sizable polarized
non-strange fragmentation functions. We predict large positive Lambda
polarization in polarized proton-proton collisions at large rapidities of the
produced Lambda, while other models, based on SU(3) flavor symmetric
fragmentation functions, predict zero or negative Lambda polarization. The
effect of and decays is also discussed. Forthcoming
experiments at RHIC will be able to differentiate between these predictions.Comment: 18 pages, 5 figure
An Efficient Implementation of a Quasi-polynomial Algorithm for Generating Hypergraph Transversals
Given a finite set V, and a hypergraph , the hypergraph transversal problem calls for enumerating all minimal hitting sets (transversals) for . This problem plays an important role in practical applications as many other problems were shown to be polynomially equivalent to it. Fredman and Khachiyan (1996) gave an incremental quasi-polynomial time algorithm for solving the hypergraph transversal problem [9]. In this paper, we present an efficient implementation of this algorithm. While we show that our implementation achieves the same bound on the running time as in [9], practical experience with this implementation shows that it can be substantially faster. We also show that a slight modification of the algorithm in [9] can be used to give a stronger bound on the running time
An Algorithm for Dualization in Products of Lattices and Its Applications
Let \cL=\cL_1×⋅s×\cL_n be the product of n lattices, each of which has a bounded width. Given a subset \cA\subseteq\cL, we show that the problem of extending a given partial list of maximal independent elements of \cA in \cL can be solved in quasi-polynomial time. This result implies, in particular, that the problem of generating all minimal infrequent elements for a database with semi-lattice attributes, and the problem of generating all maximal boxes that contain at most a specified number of points from a given n-dimensional point set, can both be solved in incremental quasi-polynomial time
Implementation status of mandatory inspection of sprayers in Romania
To harmonize the Romanian legislation on plant protection to the European legislation the Directive 128/2009 has been transposed into national legislation by Government Emergency Ordinance 34/2012 on establishing the institutional framework for action to the sustainable use of pesticides in Romania.National Action Plan approved by Decision 683/2013, on reducing the risks associated with the use of plant protection products is the strategic document regarding the continuous improvement of the use of plant protection products and contains quantitative targets, measures and timetables to reduce risks and the effects of using plant protection products on the environment and human health
Catalogue of the enchytraeid worm collection (Oligochaeta: Enchytraeidae) of the Natural History Museum in London. I. Spirit collection
The catalogue of the enchytraeid spirit collection in the Natural History Museum, London is presented.Two lists are given: 1) Inventory of the collection listed in alphabetical order of genera, and 2) Alphabeticallist of the species with the valid genera names
Upper and Lower Bounds for Weak Backdoor Set Detection
We obtain upper and lower bounds for running times of exponential time
algorithms for the detection of weak backdoor sets of 3CNF formulas,
considering various base classes. These results include (omitting polynomial
factors), (i) a 4.54^k algorithm to detect whether there is a weak backdoor set
of at most k variables into the class of Horn formulas; (ii) a 2.27^k algorithm
to detect whether there is a weak backdoor set of at most k variables into the
class of Krom formulas. These bounds improve an earlier known bound of 6^k. We
also prove a 2^k lower bound for these problems, subject to the Strong
Exponential Time Hypothesis.Comment: A short version will appear in the proceedings of the 16th
International Conference on Theory and Applications of Satisfiability Testin
- …