摘要:

We find a necessary and sufficient condition on a Riesz spaceEsuch that a sub-Boolean algebra of components of a positive element generates the Boolean algebra of all components of the element. This condition yields a dual characterization of principalA-modules in the sense of D. Vuza. When applied tol-algebras, one finds improvements of results of J. Synnatzschke.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631774

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Players ONE and TWO play the following game of length ω: In then-th inning ONE first chooses a meager subset of the real line; TWO responds with a nowhere dense set. TWO wins only if the union of TWO'S nowhere dense sets is exactly equal to the union of ONE'S first category sets. We prove that TWO has a winning strategy, even if TWO remembers only the most recent two moves each inning (Corollary 8). We show that in a closely related game, the assertion that TWO has a winning strategy depending on only the most recent two moves each inning is equivalent to a weak version of the Singular Cardinals Hypothesis (Theorem 1).

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631775

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We consider reflection functors in the category of nilpotent groups satisfying certain exactness properties for which the Mal'cev completion functor and thep-cotorsion completion functors are prototypical examples. Each of these functors defines a generalized torsion theory, which in turn defines a closure operator on subgroups. This gives rise to the notion of a categorically compact group with respect to the closure operator which we characterize. This approach provides a unified treatment for the categorically compact groups with respect to the Mal'cev completion and with respect to thep-cotorsion completion, the latter being new. We also consider thep-pro-finite completion, suitably restricted to obtain a reflection functor, and characterize the compact groups so arising.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631776

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A bridging criterion between the category of rings and the category of A-modules is given. This is obtained via a functional relationship between Hoehnke radicals of rings and radicals of A-mod.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631777

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A particle Lagrangian of a linear scalar second-order ordinary differential equation can admit maximally one of 1,2,3 or 5 Noether point symmetries. Moreover, canonical forms of particle Lagrangians of the linear equation are presented according to the number (and algebra) of Noether point symmetries they admit.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631778

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Trying to solve the question of whether everyT1topological space with a unique compatible quasi-proximity should be hereditarily compact, we show that it is true for product spaces as well as for locally hereditarily Lindelöf spaces.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631779

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

LetXandYbe normed spaces andTa linear relation inXxY.Certain known operational quantities of linear operators are extended to linear relations. Properties ofTsuch as precompactness, strict singularity, upper semi-Fredholmness and partial continuity are defined and characterised in terms of the given quantities, and certain uniform boundedness properties of these quantities derived.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631780

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In [Na-Rh] we developed a method based on positivity in order to characterize the stability of the evolution family corresponding to the nonautonomous Cauchy problem in Hilbert spaces. This method is extended to the study of hyperbolicity of linear skew-products. We also show that exponential dichotomy of a linear skew-product flow is equivalent to the existence of a Hermitian valued solution of some linear Riccati equation.

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631781

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631782

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1607-3606    

DOI:10.1080/16073606.1994.9631773

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor