Cardinalities of σ-complete OML's

In this paper we show that the Comfort-Hager result on cardinalities of-complete Boolean algebras is also true for-complete OML's having a bound on the number of complements. Using the Kaplansky theorem on continuous geometries we get a result on modular ortho-lattices. We also get a result on cardinalities of saturated OML's.Presented by R. McKenzie.Supported by the NSF of Srbija through Math. Inst., Grant #401A.     

Equational calculi for Grzegorczyk's classes ɛn

Equational calculi are constructed for Grzegorczyk's classes ⁿ and a proof is sketched for an Important theorem for these classes.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 68, pp. 140–141, 1977.The author expresses his great appreciation to. N. A. Shanin and G. E. Mints for their valuable advice and comments.     

A Kazdan–Warner type identity for the σk curvature

We prove a Kazdan–Warner type identity involving the ${\sigma }_k$ curvature and a conformal Killing vector field on a compact manifold. Our method also works to provide a unified proof for the necessary conditions in the Christoffel–Minkowski problem. To cite this article: Z.-C. Han, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

A Cantor-Bernstein Theorem for σ-Complete MV-Algebras

The Cantor-Bernstein theorem was extended to -complete boolean algebras by Sikorski and Tarski. Chang's MV-algebras are a nontrivial generalization of boolean algebras: they stand to the infinite-valued calculus of Lukasiewicz as boolean algebras stand to the classical two-valued calculus. In this paper we further generalize the Cantor-Bernstein theorem to -complete MV-algebras, and compare it to a related result proved by Jakubík for certain complete MV-algebras.     

Invariant σ-fields for a class of diffusions

Summary The invariant -field for a diffusion gives all bounded harmonic functions for the infinitesimal generator of that diffusion. We specify the invariant -field for a class of two dimensional diffusions and thereby obtain a representation for all bounded harmonic functions for the process. When the infinitesimal generator is radially symmetric we obtain the Martin boundary. This is used to find the invariant -field for the corresponding process.     

The 1/N-Expansion for Flag-Manifold σ-Models

Theoretical and Mathematical Physics - We derive the Feynman rules for the 1/N-expansion of the simplest σ-model in the class of models that we previously proposed. We consider the case where...     

Differentiating σ-fields for Gaussian and shifted Gaussian processes

We study the notions of differentiating and non-differentiating σ-fields in the general framework of (possibly drifted) Gaussian processes and characterize their invariance properties, when changing to an equivalent probability measure. As an application, we investigate the class of stochastic derivatives associated with shifted fractional Brownian motions. We finally establish conditions for the existence of a jointly measurable version of the differentiated process and we outline a general framework for stochastic embedded equations.     

Gröbner Bases for Ideals of σ-PBW Extensions

In this article, we introduce the σ-PWB extensions and construct the theory of Gröbner bases for the left ideals of them. We prove the Hilbert's basis theorem and the division algorithm for this more general class of Poincaré–Birkhoff–Witt extensions. For the particular case of bijective and quasi-commutative σ-PWB extensions, we implement the Buchberger's algorithm for computing Gröbner bases of left ideals.     

ℰ-complete andD-generic filters of partially ordered sets

In this paper we prove theorems which ensure the existence of -complete andD-generic filters of partially ordered sets.     

A Marginal Sampler for σ-Stable Poisson–Kingman Mixture Models

We investigate the class of σ-stable Poisson–Kingman random probability measures (RPMs) in the context of Bayesian nonparametric mixture modeling. This is a large class of discrete RPMs, which encompasses most of the popular discrete RPMs used in Bayesian nonparametrics, such as the Dirichlet process, Pitman–Yor process, the normalized inverse Gaussian process, and the normalized generalized Gamma process. We show how certain sampling properties and marginal characterizations of σ-stable Poisson–Kingman RPMs can be usefully exploited for devising a Markov chain Monte Carlo (MCMC) algorithm for performing posterior inference with a Bayesian nonparametric mixture model. Specifically, we introduce a novel and efficient MCMC sampling scheme in an augmented space that has a small number of auxiliary variables per iteration. We apply our sampling scheme to a density estimation and clustering tasks with unidimensional and multidimensional datasets, and compare it against competing MCMC sampling schemes. Supplementary materials for this article are available online.     

On the structure of sets of σ-monogeneity for continuous functions

The notion of the sets of -monogeneity for continuous functions is introduced which makes it possible to study pseudo-analytic properties of these functions. The theorem on the structure of these sets is proved.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 45, No. 2, pp. 226–232, February, 1993.     

Totally dissipative measures for the shift and conformal σ-finite measures for the stable holonomies

In this paper we investigate some results of ergodic theory with infinite measures for a subshift of finite type. We give an explicit way to construct σ-finite measures which are quasi-invariant by the stable holonomy and equivalent to the conditional measures of some σ-invariant measure. These σ-invariant measures are totally dissipative, σ-finite but satisfy a Birkhoff Ergodic-like Theorem. The constructions are done for the symbolic case, but can be extended for uniformly hyperbolic flows or diffeomorphisms.     

The classification of (J, σ)-irreducible monoids of type A 4

In this paper we develop a very basic method to classify (J, σ)-irreducible monoids of type A ₄. As a typical example, we list all the types for the monoids corresponding to the strongly dominant weights. This example also shows that there is no general theorem to determine the cross-section lattices for reductive monoids according to their Dynkin diagrams as Putcha and Renner’s recipe for J-irreducible monoids.     

Finite groups with given σ-embedded and σ-n-embedded subgroups

Let G be a finite group and σ = {σ _i |i∈I} be a partition of the set of all primes P. A set H of subgroups of G is said to be a complete Hall σ-set of G if every non-identity member of H is a Hall σ _i -subgroup of G and H contains exactly one Hall σ _i -subgroup of G for every σ _i ∈ σ(G). A subgroup H is said to be σ-permutable if G possesses a complete Hall σ-set H such that HA ^x = A ^x H for all A ∈ H and all x ∈ G. Let H be a subgroup of G. Then we say that: (1) H is σ-embedded in G if there exists a σ-permutable subgroup T of G such that HT = H ^σG and H ∩ T ≤ H _σG , where H _σG is the subgroup of H generated by all those subgroups of H which are σ-permutable in G, and H ^σG is the σ-permutable closure of H, that is, the intersection of all σ-permutable subgroups of G containing H. (2) H is σ-n-embedded in G if there exists a normal subgroup T of G such that HT = H ^G and H ∩ T ≤ H _σG . In this paper, we study the properties of the new embedding subgroups and use them to determine the structure of finite groups.     

The extreme solutions for a σ-Hessian equation with a nonlinear operator

The aim of this paper is to study the existence of extreme solutions and their properties for a general -Hessian equation involving a nonlinear operator. By introducing a suitable growth condition and developing a iterative technique, some new results on existence and asymptotic estimates of minimum and maximum solutions are derived. Moreover, we also establish the iterative sequences that converge uniformly to the extreme solutions.