Browsing Matematisk institutt by Author "Dahl, Geir"

Now showing items 1-20 of 35

  • Alternating Sign and Sign-Restricted Matrices: Representations and Partial Orders 
    Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    Sign-restricted matrices (SRMs) are (0,±1)-matrices where, ignoring 0's, the signs in each column alternate beginning with a +1 and all partial row sums are nonnegative. The most investigated of these matrices are the ...
  • Alternating Sign Matrices -- Extensions, Konig-properties, and Primary Sum-Sequences 
    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 ...
  • Alternating Sign Matrices and Hypermatrices, and a Generalization of Latin Squares 
    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 ...
  • Alternating sign matrices, extensions and related cones 
    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 ...
  • Alternating Sign Matrices, Related (0, 1)-Matrices, and the Smith Normal Form 
    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. ...
  • An extension of the polytope of doubly stochastic 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
  • Combinatorial Fiedler theory and graph partition 
    Andrade, Enide; Dahl, Geir (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
  • Combinatorial Perron Parameters for Trees 
    Andrade, Enide; Ciardo, Lorenzo; Dahl, Geir (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2019)
  • Combinatorial Perron values of trees and bottleneck matrices 
    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) ...
  • Convex (0,1)-Matrices and Their Epitopes, 
    Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
  • Diagonal Sums of Doubly Stochastic Matrices 
    Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
  • Disjoint congruence classes and a timetabling application 
    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; ...
  • Doubly Stochastic Matrices and the Bruhat Order 
    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 ...
  • Frobenius-König theorem for classes of (0, ±1)-matrices 
    Brualdi, R.A.; Dahl, Geir (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
  • Integral majorization polytopes 
    Dahl, Geir; Zhang, Fuzhen (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2013)
  • The interval structure of (0,1)-matrices 
    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 A-interval 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 ∗ ...
  • The k-regular induced subgraph problem 
    Agra, Agostinho; Dahl, Geir; Haufmann, Torkel Andreas; Pinheiro, Sofia (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
    We consider the problem of finding a maximum k-regular induced subgraph of a graph G. Theoretical results are established to compare upper bounds obtained from different techniques, including bounds from quadratic programming, ...
  • Lagrangian based methods for finding MAP solutions for MRF models 
    Storvik, Geir; Dahl, Geir (Research report / Forskningsrapport, 1996)
  • Linear optimization and mathematical finance 
    Dahl, Geir; Dahl, Kristina Rognlien (Research report / Forskningsrapport, 2012)
  • LP based heuristics for the multiple knapsack problem with assignment restrictions 
    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 NP-hard. We consider special cases and their computational complexity. ...