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2. Commuting graphs and extremal centralizersGregor Dolinar, Aleksandr Èmilevič Guterman, Bojan Kuzma, Polona Oblak, 2014, izvirni znanstveni članek Opis: We determine the conditions for matrix centralizers which can guarantee the connectedness of the commuting graph for the full matrix algebra ▫$M_n(\mathbb{F})$▫ over an arbitrary field ▫$\mathbb{F}$▫. It is known that if ▫$\mathbb{F}$▫ is an algebraically closed field and ▫$n \ge 3$▫, then the diameter of the commuting graph of ▫$M_n(\mathbb{F})$▫ is always equal to four. We construct a concrete example showing that if ▫$\mathbb{F}$▫ is not algebraically closed, then the commuting graph of ▫$M_n(\mathbb{F})$▫ can be connected with the diameter at least five. Ključne besede: commuting graph, matrix ring, centralizer Objavljeno v RUP: 31.12.2021; Ogledov: 836; Prenosov: 23 Celotno besedilo (228,78 KB) |
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5. Konveksne množice in konveksne funkcije : zaključna nalogaBećo Merulić, 2015, diplomsko delo Ključne besede: afine množice, konveksne množice, epigraf, zaprtje, relativno odprtje, efektivna domena, Jensenova neenakost, konveksne funkcije, zveznost konveksnih funkcij, subgradient, gradient, diferenciabilnost konveksnih funkcij Objavljeno v RUP: 13.11.2017; Ogledov: 2504; Prenosov: 46 Povezava na celotno besedilo |
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7. Mappings that preserve pairs of operators with zero triple Jordan productMirko Dobovišek, Bojan Kuzma, Gorazd Lešnjak, Chi-Kwong Li, Tatjana Petek, 2007, izvirni znanstveni članek Opis: Let ▫$\mathbb{F}$▫ be a field and ▫$n \ge 3$▫. Suppose ▫${\mathfrak{G_1,G_2}} \subseteq M_n(\mathbb{F})▫$ contain all rank-one idempotents. The structure of surjections ▫$\phi : \mathfrak{G_1} \to \mathfrak{G_2}$▫ satisfying ▫$ABA = 0 \iff \phi(A)\phi(B)\phi(A) = 0$▫ is determined. Similar results are also obtained for (a) subsets of bounded operators acting on a complex or real Banach space, (b) the space of Hermitian matrices acting on ▫$n$▫-dimensional vectors over a skew-field, (c) subsets of self-adjoint bounded linear operators acting on an infinite dimensional complex Hilbert space. It is then illustrated that the results can be applied to characterize mappings ▫$\phi$▫ on matrices or operators such that ▫$F(ABA) = F(\phi(A)\phi(B)\phi(A))▫$ for all ▫$A,B$▫ for functions ▫$F$▫ such as the spectral norm, Schatten ▫$p$▫-norm, numerical radius and numerical range, etc. Ključne besede: matrix algebra, Jordan triple product, nonlinear preservers Objavljeno v RUP: 03.04.2017; Ogledov: 2486; Prenosov: 97 Povezava na celotno besedilo |
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9. Bar´ery Gibsona dlja problemy PoliaGregor Dolinar, Aleksandr Èmilevič Guterman, Bojan Kuzma, 2010, objavljeni znanstveni prispevek na konferenci Opis: V članku je obravnavana spodnja meja za število neničelnih elementov v ▫$(0, 1)$▫ matrikah, pri katerem se da permanento vedno pretvoriti v determinanto samo s spreminjanjem predznaka ▫$pm$▫ elementom matrike. Ključne besede: matematika, linearna algebra, teorija matrik, permanenta, determinanta Objavljeno v RUP: 03.04.2017; Ogledov: 2152; Prenosov: 64 Povezava na celotno besedilo |
10. Reflexivity defect of spaces of linear operatorsJanko Bračič, Bojan Kuzma, 2009, izvirni znanstveni članek Opis: For a finite-dimensional linear subspace ▫{$\mathscr{S}} \subseteq {\mathscr{L}} (V,W)$▫ and a positive integer ▫$k$▫, the ▫$k$▫-reflexivity defect of ▫$\mathscr{S}$▫ is defined by ▫${\mathrm{rd}}_k ({\mathscr{S}}) = \dim({\mathrm{Ref}}_k (\mathscr{S})/\mathscr{S})$▫ where ▫${\mathrm{Ref}}_k$▫ is the ▫$k$▫-reflexive closure of ▫$\mathscr{S}$▫. We study this quantity for two-dimensional spaces of operators and for single generated algebras and their commutants. Ključne besede: mathematics, operator theory, reflexivity defect, reflexivity, two-dimensional space of operators, single generated algebra, commutant Objavljeno v RUP: 03.04.2017; Ogledov: 2197; Prenosov: 193 Povezava na celotno besedilo |