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Strongly internal sets and generalized smooth functions  [PDF]
Paolo Giordano,Michael Kunzinger,Hans Vernaeve
Mathematics , 2014,
Abstract: Based on a refinement of the notion of internal sets in Colombeau's theory, so-called strongly internal sets, we introduce the space of generalized smooth functions, a maximal extension of Colombeau generalized functions. Generalized smooth functions as morphisms between sets of generalized points form a sub-category of the category of topological spaces. In particular, they can be composed unrestrictedly.
Strongly transitive multiple trees  [PDF]
Katrin Tent
Mathematics , 2011,
Abstract: We give an amalgamation construction of free multiple trees with a strongly transitive automorphism group. The construction shows that any partial codistance function on a tuple of finite trees can be extended to yield multiple trees.
Transitive Sets and Cyclic Quadrilaterals  [PDF]
Imre Leader,Paul A. Russell,Mark Walters
Mathematics , 2010,
Abstract: Motivated by some questions in Euclidean Ramsey theory, our aim in this note is to show that there exists a cyclic quadrilateral that does not embed into any transitive set (in any dimension). We show that in fact this holds for almost all cyclic quadrilaterals, and we also give explicit examples of such cyclic quadrilaterals. These are the first explicit examples of spherical sets that do not embed into transitive sets.
Transitive Hall sets  [PDF]
Gérard Henry Edmond Duchamp,Jean-Gabriel Luque,Marianne Deboysson-Flouret
Mathematics , 2005,
Abstract: We give the definition of Lazard and Hall sets in the context of transitive factorizations of free monoids. The equivalence of the two properties is proved. This allows to build new effective bases of free partially commutative Lie algebras. The commutation graphs for which such sets exist are completely characterized and we explicit, in this context, the classical PBW rewriting process.
Maximal chain transitive sets for local groups  [cached]
Carlos J. Braga Barros,Luiz A. B. San Martin
Boletim da Sociedade Paranaense de Matemática , 2003,
Abstract: Let H be a locally transitive local group. We characterize the maximal chain sets for a family F of subsets of H as intersections of control sets for certain shadowing semigroups.
Semi-monotone sets  [PDF]
Saugata Basu,Andrei Gabrielov,Nicolai Vorobjov
Mathematics , 2010,
Abstract: A coordinate cone in R^n is an intersection of some coordinate hyperplanes and open coordinate half-spaces. A semi-monotone set is a defnable in an o-minimal structure over the reals, open bounded subset of R^n such that its intersection with any translation of any coordinate cone is connected. This can be viewed as a generalization of the convexity property. Semi-monotone sets have a number of interesting geometric and combinatorial properties. The main result of the paper is that every semi-monotone set is a topological regular cell.
Chain transitive homeomorphisms on a space: all or none  [PDF]
ethan akin,juho rautio
Mathematics , 2015,
Abstract: We consider which spaces can be realized as the omega limit set of the discrete time dynamical system. This is equivalent to asking which spaces admit a chain transitive homeomorphism and which do not. This leads us to ask for spaces where all homeomorphisms are chain transitive.
Convergence rates for forward-backward dynamical systems associated with strongly monotone inclusions  [PDF]
Radu Ioan Bot,Ern? Robert Csetnek
Mathematics , 2015,
Abstract: We investigate the convergence rates of the trajectories generated by implicit first and second order dynamical systems associated to the determination of the zeros of the sum of a maximally monotone operator and a monotone and Lipschitz continuous one in a real Hilbert space. We show that these trajectories strongly converge with exponential rate to a zero of the sum, provided the latter is strongly monotone. We derive from here convergence rates for the trajectories generated by dynamical systems associated to the minimization of the sum of a proper, convex and lower semicontinuous function with a smooth convex one provided the objective function fulfills a strong convexity assumption. In the particular case of minimizing a smooth and strongly convex function, we prove that its values converge along the trajectory to its minimum value with exponential rate, too.
Transitive Sets in Euclidean Ramsey Theory  [PDF]
Imre Leader,Paul A. Russell,Mark Walters
Mathematics , 2010,
Abstract: A finite set $X$ in some Euclidean space $R^n$ is called Ramsey if for any $k$ there is a $d$ such that whenever $R^d$ is $k$-coloured it contains a monochromatic set congruent to $X$. This notion was introduced by Erdos, Graham, Montgomery, Rothschild, Spencer and Straus, who asked if a set is Ramsey if and only if it is spherical, meaning that it lies on the surface of a sphere. This question (made into a conjecture by Graham) has dominated subsequent work in Euclidean Ramsey theory. In this paper we introduce a new conjecture regarding which sets are Ramsey; this is the first ever `rival' conjecture to the conjecture above. Calling a finite set transitive if its symmetry group acts transitively---in other words, if all points of the set look the same---our conjecture is that the Ramsey sets are precisely the transitive sets, together with their subsets. One appealing feature of this conjecture is that it reduces (in one direction) to a purely combinatorial statement. We give this statement as well as several other related conjectures. We also prove the first non-trivial cases of the statement. Curiously, it is far from obvious that our new conjecture is genuinely different from the old. We show that they are indeed different by proving that not every spherical set embeds in a transitive set. This result may be of independent interest.
Smooth and non-smooth estimates of a monotone hazard  [PDF]
Piet Groeneboom,Geurt Jongbloed
Statistics , 2011,
Abstract: We discuss a number of estimates of the hazard under the assumption that the hazard is monotone on an interval [0,a]. The usual isotonic least squares estimators of the hazard are inconsistent at the boundary points 0 and a. We use penalization to obtain uniformly consistent estimators. Moreover, we determine the optimal penalization constants, extending related work in this direction by Woodroofe and Sun (1993) and Woodroofe and Sun (1999). Two methods of obtaining smooth monotone estimates based on a non-smooth monotone estimator are discussed. One is based on kernel smoothing, the other on penalization.
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