Zobrazeno 1 - 10
of 34
pro vyhledávání: '"Zenon Jan Jabłoński"'
Publikováno v:
Opuscula Mathematica, Vol 44, Iss 3, Pp 303-321 (2024)
The occasion for this survey article was the 70th birthday of Jan Stochel, professor at Jagiellonian University, former head of the Chair of Functional Analysis and a prominent member of the Kraków school of operator theory. In the course of his mat
Externí odkaz:
https://doaj.org/article/4c1527e835b84a49b71d0e451b0ca38e
Publikováno v:
Abstract and Applied Analysis, Vol 2014 (2014)
It is shown that for every positive integer n there exists a subnormal weighted shift on a directed tree (with or without root) whose nth power is densely defined while its (n+1)th power is not. As a consequence, for every positive integer n there ex
Externí odkaz:
https://doaj.org/article/1bb5a3b54fd3460c8b1ae6ce2cefae62
In a recent paper [15], Hilbert space operators $T$ with the property that each sequence of the form $\{\|T^n h\|^2\}_{n=0}^{\infty}$ is conditionally positive definite in a semigroup sense were introduced. In the present paper, this line of research
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::3ef1c656a6d45a90865559f9a1c17315
http://arxiv.org/abs/2106.03222
http://arxiv.org/abs/2106.03222
The Cauchy dual subnormality problem asks whether the Cauchy dual operator of a $2$-isometry is subnormal. Recently this problem has been solved in the negative. Here we show that it has a negative solution even in the class of cyclic $2$-isometries.
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::68a55c62a74de6963ac73f6ffa85a71f
In this paper we give necessary and sufficient conditions for a bounded linear Hilbert space operator to be an m-isometry for an unspecified m written in terms of conditions that are applied to “one vector at a time”. We provide criteria for orth
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::9a156aa3c58e400237977ee49276d072
https://ruj.uj.edu.pl/xmlui/handle/item/153014
https://ruj.uj.edu.pl/xmlui/handle/item/153014
In this paper, we introduce operators that are represented by upper triangular $2\times 2$ block matrices whose entries satisfy some algebraic constraints. We call them Brownian-type operators of class $\mathcal Q,$ briefly operators of class $\mathc
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4f62de8a8dc44b23f7c16e2d36eee4e6
http://arxiv.org/abs/1910.02872
http://arxiv.org/abs/1910.02872
Publikováno v:
Journal of Mathematical Analysis and Applications. 435:302-314
It is shown that for any positive integer n there exists a subnormal weighted shift on a directed tree whose nth power is closed and densely defined while its ( n + 1 ) th power has trivial domain. Similar result for composition operators in L 2 -spa
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::27454b2501434e397744b2b8232432bd
https://doi.org/10.1016/j.jmaa.2015.10.021
https://doi.org/10.1016/j.jmaa.2015.10.021
Publikováno v:
Lecture Notes in Mathematics ISBN: 9783319740386
The main goal of this chapter is to provide criteria for the subnormality of (not necessarily bounded) weighted composition operators. The first criterion, which is given in Sect. 3.1, requires that hϕ,w > 0 a.e. [μ w ] and that there exists a meas
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::5edda0ea4da7855776186dd7ec071df7
https://doi.org/10.1007/978-3-319-74039-3_3
https://doi.org/10.1007/978-3-319-74039-3_3
Publikováno v:
Lecture Notes in Mathematics ISBN: 9783319740386
In this chapter, we investigate the interplay between selected properties of a weighted composition operator Cϕ,w and the corresponding composition operator C ϕ . In Sect. 7.1, we discuss the questions of when the product M w C ϕ is closed and whe
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::a0081cdfee772fbaf7eb5fbd43944f35
https://doi.org/10.1007/978-3-319-74039-3_7
https://doi.org/10.1007/978-3-319-74039-3_7