Browsing Matematisk institutt by Author "Dahl, Geir"
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Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)This paper is concerned with properties of permutation matrices and alternating sign matrices (ASMs). An ASM is a square (0,±1)matrix such that, ignoring 0’s, the 1’s and −1’s in each row and column alternate, beginning ...

Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / SubmittedVersion, 2017)An alternating sign matrix, or ASM, is a (0, ±1)matrix where the nonzero entries in each row and column alternate in sign. We generalize this notion to hypermatrices: an n × n × n hypermatrix A = [aijk] is an alternating ...

Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)An alternating sign matrix , or ASM, is a (0,±1)(0,±1)matrix where the nonzero entries in each row and column alternate in sign, and where each row and column sum is 1. We study the convex cone generated by ASMs of order ...

Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2018)We investigate the Smith Normal Form (SNF) of alternating sign matrices (ASMs) and related matrices of 0’s and 1’s ((0, 1)matrices). We identify certain classes of ASMs and (0, 1)matrices whose SNFs are (0, 1)matrices. ...

Brualdi, Richard A.; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2013)This is an Author's Accepted Manuscript of an article published in Linear and Multilinear Algebra Volume 61, Issue 3, 2013. Published online: 07 Jun 2012. Copyright Taylor & Francis, available online

Andrade, Enide; Ciardo, Lorenzo; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2019)

Andrade, Enide; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)The algebraic connectivity a(G) of a graph G is an important parameter, defined as the second smallest eigenvalue of the Laplacian matrix of G. If T is a tree, a(T) is closely related to the Perron values (spectral radius) ...

Dahl, Geir (Journal article / Tidsskriftartikkel / SubmittedVersion, 2009)We consider a combinatorial problem motivated by a special simplified timetabling problem for subway networks. Mathematically the problem is to find (pairwise) disjoint congruence classes modulo certain given integers; ...

Brualdi, Richard A.; Dahl, Geir; Fritscher, Eliseu (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2016)The Bruhat order is defined in terms of an interchange operation on the set of permutation matrices of order n which corresponds to the transposition of a pair of elements in a permutation. We introduce an extension of ...

Dahl, Geir; Zhang, Fuzhen (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2013)

Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2018)Let A be an n × n (0, ∗)matrix, so each entry is 0 or ∗. An Ainterval matrix is a (0, 1)matrix obtained from A by choosing some ∗’s so that in every interval of consecutive ∗’s, in a row or column of A, exactly one ∗ ...

Agra, Agostinho; Dahl, Geir; Haufmann, Torkel Andreas; Pinheiro, Sofia (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)We consider the problem of finding a maximum kregular induced subgraph of a graph G. Theoretical results are established to compare upper bounds obtained from different techniques, including bounds from quadratic programming, ...

Storvik, Geir; Dahl, Geir (Research report / Forskningsrapport, 1996)

Dahl, Geir; Dahl, Kristina Rognlien (Research report / Forskningsrapport, 2012)

Dahl, Geir; Foldnes, Njål (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2006)Starting with a problem in wireless telecommunication, we are led to study the multiple knapsack problem with assignment restrictions. This problem is NPhard. We consider special cases and their computational complexity. ...

Dahl, Geir; Guterman, Alexander; Shteyner, Pavel (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)

Dahl, Geir; Guterman, Alexander; Shteyner, Pavel (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2018)We introduce a new majorization order for classes (sets) of matrices which generalizes several existing notions of matrix majorization. Roughly, the notion says that every matrix in one class is majorized by some matrix ...

Andrade, Enide; Dahl, Geir; Leal, Laura; Robbiano, Maria (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2019)Let G be an undirected simple graph. The signless Laplacian spread of G is defined as the maximum distance of pairs of its signless Laplacian eigenvalues. This paper establishes some new bounds, both lower and upper, for ...

Ciardo, Lorenzo; Dahl, Geir; Kirkland, Steve (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)

Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)Abstract For a permutation π , and the corresponding permutation matrix, we introduce the notion of discrete derivative , obtained by taking differences of successive entries in π . We characterize the possible derivatives ...