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On topologization of countably generated algebras

W. Żelazko (1994)

Studia Mathematica

We prove that any real or complex countably generated algebra has a complete locally convex topology making it a topological algebra. Assuming the continuum hypothesis, it is the best possible result expressed in terms of the cardinality of a set of generators. This result is a corollary to a theorem stating that a free algebra provided with the maximal locally convex topology is a topological algebra if and only if the number of variables is at most countable. As a byproduct we obtain an example...

On total incomparability of mixed Tsirelson spaces

Julio Bernués, Javier Pascual (2003)

Czechoslovak Mathematical Journal

We give criteria of total incomparability for certain classes of mixed Tsirelson spaces. We show that spaces of the form T [ ( k , θ k ) k = 1 l ] with index i ( k ) finite are either c 0 or p saturated for some p and we characterize when any two spaces of such a form are totally incomparable in terms of the index i ( k ) and the parameter θ k . Also, we give sufficient conditions of total incomparability for a particular class of spaces of the form T [ ( 𝒜 k , θ k ) k = 1 ] in terms of the asymptotic behaviour of the sequence i = 1 n e i where ( e i ) is the canonical basis....

On two possible constructions of the quantum semigroup of all quantum permutations of an infinite countable set

Debashish Goswami, Adam Skalski (2012)

Banach Center Publications

Two different models for a Hopf-von Neumann algebra of bounded functions on the quantum semigroup of all (quantum) permutations of infinitely many elements are proposed, one based on projective limits of enveloping von Neumann algebras related to finite quantum permutation groups, and the second on a universal property with respect to infinite magic unitaries.

On two quantum versions of the detailed balance condition

Franco Fagnola, Veronica Umanità (2010)

Banach Center Publications

Quantum detailed balance conditions are often formulated as relationships between the generator of a quantum Markov semigroup and the generator of a dual semigroup with respect to a certain scalar product defined by an invariant state. In this paper we survey some results describing the structure of norm continuous quantum Markov semigroups on ℬ(h) satisfying a quantum detailed balance condition when the duality is defined by means of pre-scalar products on ℬ(h) of the form x , y s : = t r ( ρ 1 - s x * ρ s y ) (s ∈ [0,1]) in order...

On Typical Compact Convex Sets in Hilbert Spaces

De Blasi, F. (1997)

Serdica Mathematical Journal

Let E be an infinite dimensional separable space and for e ∈ E and X a nonempty compact convex subset of E, let qX(e) be the metric antiprojection of e on X. Let n ≥ 2 be an arbitrary integer. It is shown that for a typical (in the sence of the Baire category) compact convex set X ⊂ E the metric antiprojection qX(e) has cardinality at least n for every e in a dense subset of E.

On ultrapowers of Banach spaces of type

Antonio Avilés, Félix Cabello Sánchez, Jesús M. F. Castillo, Manuel González, Yolanda Moreno (2013)

Fundamenta Mathematicae

We prove that no ultraproduct of Banach spaces via a countably incomplete ultrafilter can contain c₀ complemented. This shows that a "result" widely used in the theory of ultraproducts is wrong. We then amend a number of results whose proofs have been infected by that statement. In particular we provide proofs for the following statements: (i) All M-spaces, in particular all C(K)-spaces, have ultrapowers isomorphic to ultrapowers of c₀, as also do all their complemented subspaces isomorphic to their...

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