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1.
General preservers of quasi-commutativity on hermitian matrices
Bojan Kuzma, Gregor Dolinar, 2008, original scientific article

Abstract: Let ▫$H_n$▫ be the set of all ▫$n \times n$▫ hermitian matrices over ▫$\mathbb{C}$▫, ▫$n \ge 3$▫. It is said that ▫$A,B \in H_n$▫ quasi-commute if there exists a nonzero ▫$\xi \in \mathbb{C}$▫ such that ▫$AB = \xi BA$▫ Bijective not necessarily linear maps on hermitian matrices which preserve quasi-commutativity in both directions are classified.
Found in: osebi
Keywords: mathematics, linear algebra, general preserver, hermitian matrices, quasi-commutativity
Published: 03.04.2017; Views: 680; Downloads: 101
URL Full text (0,00 KB)
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2.
Bar´ery Gibsona dlja problemy Polia
Gregor Dolinar, Bojan Kuzma, Aleksandr Èmilevič Guterman, 2010, published scientific conference contribution

Abstract: 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.
Found in: osebi
Keywords: matematika, linearna algebra, teorija matrik, permanenta, determinanta
Published: 03.04.2017; Views: 598; Downloads: 20
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3.
General preservers of quasi-commutativity on self-adjoint operators
Bojan Kuzma, Gregor Dolinar, 2010, original scientific article

Abstract: Let ▫$H$▫ be a separable Hilbert space and▫ ${\mathcal B}_{sa}(H)▫$ the set of all bounded linear self-adjoint operators. We say that ▫$A, B \in {\mathcal B}_{sa}(H)$▫ quasi-commute if there exists a nonzero ▫$\xi \in \mathbb{C}$▫ suchthat ▫$AB=\xi BA$▫. Bijective maps on ▫${\mathcal B}_{sa}(H)$▫ which preserve quasi-commutativity in both directions are classified.
Found in: osebi
Keywords: mathematics, linear algebra, general preserver, self-adjoint operator, quasi-commutativity
Published: 03.04.2017; Views: 699; Downloads: 41
URL Full text (0,00 KB)

4.
General preservers of quasi-commutativity
Bojan Kuzma, Gregor Dolinar, 2010, original scientific article

Abstract: Let ▫$M_n$▫ be the algebra of all ▫$n \times n$▫ matrices over ▫$\mathbb{C}$▫. We say that ▫$A, B \in M_n$▫ quasi-commute if there exists a nonzero ▫$\xi \in \mathbb{C}$▫ such that ▫$AB = \xi BA$▫. In the paper we classify bijective not necessarily linear maps ▫$\Phi \colon M_n \to M_n$▫ which preserve quasi-commutativity in both directions.
Found in: osebi
Keywords: mathematics, linear algebra, general preserver, matrix algebra, quasi-commutativity
Published: 03.04.2017; Views: 539; Downloads: 43
URL Full text (0,00 KB)

5.
On maximal distances in a commuting graph
Bojan Kuzma, Polona Oblak, Gregor Dolinar, 2012, original scientific article

Abstract: It is shown that matrices over algebraically closed fields that are farthest apart in the commuting graph must be non-derogatory. Rank-one matrices and diagonalizable matrices are also characterized in terms of the commuting graph.
Found in: osebi
Keywords: matematika, linearna algebra, teorija grafov, komutirajoči grafi, matrična algebra, algebraično zaprt obseg, centralizator, razdalja v grafih, mathematics, linear algebra, graph theory, commuting graph, matrix algebra, algebraically closed field, centralizer, distance in graphs
Published: 03.04.2017; Views: 699; Downloads: 92
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6.
Permanent versus determinant over a finite field
Gregor Dolinar, Aleksandr Èmilevič Guterman, Marko Orel, Bojan Kuzma, 2013, published scientific conference contribution

Abstract: Let ▫$\mathbb{F}$▫ be a finite field of characteristic different from 2. We study the cardinality of sets of matrices with a given determinant or a given permanent for the set of Hermitian matrices ▫$\mathcal{H}_n(\mathbb{F})$▫ and for the whole matrix space ▫$M_n(\mathbb{F})$▫. It is known that for ▫$n = 2$▫, there are bijective linear maps ▫$\Phi$▫ on ▫$\mathcal{H}_n(\mathbb{F})$▫ and ▫$M_n(\mathbb{F})$▫ satisfying the condition per ▫$A = \det \Phi(A)$▫. As an application of the obtained results, we show that if ▫$n \ge 3$▫, then the situation is completely different and already for ▫$n = 3$▫, there is no pair ofmaps ▫$(\Phi, \phi)$▫, where ▫$\Phi$▫ is an arbitrary bijective map on matrices and ▫$\phi \colon \mathbb{F} \to \mathbb{F}$▫ is an arbitrary map such that per ▫$A = \phi(\det \Phi(A))$▫ for all matrices ▫$A$▫ from the spaces ▫$\mathcal{H}_n(\mathbb{F})$▫ and ▫$M_n(\mathbb{F})$▫, respectively. Moreover, for the space ▫$M_n(\mathbb{F})$▫, we show that such a pair of transformations does not exist also for an arbitrary ▫$n > 3$▫ if the field ▫$\mathbb{F}$▫ contains sufficiently many elements (depending on ▫$n$▫). Our results are illustrated by a number of examples.
Found in: osebi
Keywords: mathematics, linear algebra, matrix theory, permanent, determinant
Published: 03.04.2017; Views: 662; Downloads: 49
URL Full text (0,00 KB)

7.
Maps on self-adjoint operators preserving numerical range of products up to a factor
Kan He, Gregor Dolinar, Jin Chuan Hou, Bojan Kuzma, 2011, original scientific article

Abstract: Let ▫$H$▫ be a complex Hilbert space and ▫${mathscr{S}}_a(H)$▫ the space of all self adjoint operators on ▫$H$▫. ▫$Phi colon {mathscr{S}}_a(H) to {mathscr{S}}_a(H)$▫ is a surjective map. For ▫$xi, eta in mathbb{C} setminus {1}$▫, then ▫$Phi$▫ satisfies that ▫$$W(AB - xi BA) = W(Phi(A)Phi(B) - etaPhi(B)phi(A))$$▫ for all ▫$A,B in {mathscr{S}}_a(H)$▫ if and only if there exists a unitary operator or con-unitary operator ▫$U$▫ such that ▫$Phi(A) = UAU^ast$▫ for all ▫$A in {mathscr{S}}_a(H)$▫ or ▫$Phi(A) = -UAU^ast$▫ for all ▫$A in {mathscr{S}}_a(H)$▫.
Found in: osebi
Keywords: matematika, teorija operatorjev, numerični zaklad, ohranjevalci
Published: 03.04.2017; Views: 755; Downloads: 12
URL Full text (0,00 KB)

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