Geir Dahl
Instituttleder
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Matematisk institutt

English version of this page
E-post
geird@math.uio.no
Telefon
+47 22855835
Mobiltelefon
+47 90640373
Rom
1015
Brukernavn
Besøksadresse
Moltke Moes vei 35
Niels Henrik Abels hus
0851 Oslo
Postadresse
Postboks 1053 Blindern
0316 Oslo
Research interests
Combinatorial matrix theory; so the study of classes of matrices from a combinatorial point of view, or geometric, using convexity and polyhedral theory. Recent focused activities include majorization order and polytopes, classes of (0,1)-matrices with given line sums, doubly stochastic matrices, interval polytopes, matrix ranking methods in tennis(!) , Birkhoff polytopes, spectral graph theory etc.. My CV is here.
Teaching
MAT1120 Linear algebra (I often lecture together with Erik Bedos)
MAT3100 Linear optimization
MAT4120/MAT9120 Mathematical optimization
Reading course in different topics: graph theory, convexity, matrix theory
Some recent talks
Nytt Munch museum - et SKRIK etter kombinatorikk og geometri!
Publikasjoner
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Andrade, Enide; Ciardo, Lorenzo & Dahl, Geir (2022). Perron values and classes of trees. Linear Algebra and its Applications. ISSN 0024-3795. 639, s. 135–158. doi: 10.1016/j.laa.2022.01.005. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2021). Alternating Sign and Sign-Restricted Matrices: Representations and Partial Orders. The Electronic Journal of Linear Algebra. ISSN 1537-9582. 37. doi: 10.13001/ela.2021.6513. Fulltekst i vitenarkiv
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Brualdi, Richard A. & Dahl, Geir (2021). Sign-restricted matrices of 0's, 1's, and −1's. Linear Algebra and its Applications. ISSN 0024-3795. 615, s. 77–103. doi: 10.1016/j.laa.2021.01.001. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2021). Diagonal Sums of Doubly Stochastic Matrices. Linear and multilinear algebra. ISSN 0308-1087. doi: 10.1080/03081087.2021.1901844. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2021). Convex (0,1)-Matrices and Their Epitopes, . Discrete Applied Mathematics. ISSN 0166-218X. 297, s. 21–34. doi: 10.1016/j.dam.2021.02.038. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2020). Permutation matrices, their discrete derivatives and extremal properties. Vietnam Journal of Mathematics. ISSN 2305-221X. 48, s. 719–740. doi: 10.1007/s10013-020-00392-5. Fulltekst i vitenarkiv
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Ciardo, Lorenzo; Dahl, Geir & Kirkland, Steve (2020). On Kemeny's constant for trees with fixed order and diameter. Linear and multilinear algebra. ISSN 0308-1087. doi: 10.1080/03081087.2020.1796905. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2020). Alternating Sign Matrices: Extensions, König-properties, and Primary Sum-Sequences. Graphs and Combinatorics. ISSN 0911-0119. 36, s. 63–92. doi: 10.1007/s00373-019-02119-x. Fulltekst i vitenarkiv
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Dahl, Geir; Guterman, Alexander & Shteyner, Pavel (2019). Majorization for (0,1)-matrices. Linear Algebra and its Applications. ISSN 0024-3795. 585, s. 147–163. doi: 10.1016/j.laa.2019.09.038. Fulltekst i vitenarkiv
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Andrade, Enide; Ciardo, Lorenzo & Dahl, Geir (2019). Combinatorial Perron Parameters for Trees. Linear Algebra and its Applications. ISSN 0024-3795. 566, s. 138–166. doi: 10.1016/j.laa.2018.12.028. Fulltekst i vitenarkiv
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Andrade, Enide; Dahl, Geir; Leal, Laura & Robbiano, Maria (2019). New bounds for the signless Laplacian spread. Linear Algebra and its Applications. ISSN 0024-3795. 566, s. 98–120. doi: 10.1016/j.laa.2018.12.019. Fulltekst i vitenarkiv
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Dahl, Geir; Guterman, Alexander & Shteyner, Pavel (2018). Majorization for matrix classes. Linear Algebra and its Applications. ISSN 0024-3795. 555, s. 201–221. doi: 10.1016/j.laa.2018.06.003. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2018). Alternating sign matrices, related (0,1)-matrices, and the Smith normal form. Linear Algebra and its Applications. ISSN 0024-3795. s. 1–19. doi: 10.1016/j.laa.2018.03.027. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2018). The interval structure of (0,1)-matrices. Discrete Applied Mathematics. ISSN 0166-218X. doi: 10.1016/j.dam.2018.03.024. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2018). Alternating Sign Matrices and Hypermatrices, and a Generalization of Latin Squares. Advances in Applied Mathematics. ISSN 0196-8858. 95, s. 116–151. doi: 10.1016/j.aam.2017.11.005. Fulltekst i vitenarkiv
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Agra, Agostinho; Dahl, Geir; Haufmann, Torkel Andreas & Pinheiro, Sofia (2017). The k-regular induced subgraph problem. Discrete Applied Mathematics. ISSN 0166-218X. 222, s. 14–30. doi: 10.1016/j.dam.2017.01.029. Fulltekst i vitenarkiv
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Brualdi, R.A. & Dahl, Geir (2017). Alternating sign matrices, extensions and related cones. Advances in Applied Mathematics. ISSN 0196-8858. 86, s. 19–49. doi: 10.1016/j.aam.2016.12.001. Fulltekst i vitenarkiv
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Andrade, Enide & Dahl, Geir (2016). Combinatorial Perron values of trees and bottleneck matrices. Linear and multilinear algebra. ISSN 0308-1087. 65(12), s. 2387–2405. doi: 10.1080/03081087.2016.1274363. Fulltekst i vitenarkiv
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Brualdi, Richard A.; Dahl, Geir & Fritscher, Eliseu (2016). Doubly Stochastic Matrices and the Bruhat Order. Czechoslovak Mathematical Journal. ISSN 0011-4642. 66(3), s. 681–700. doi: 10.1007/s10587-016-0286-6. Fulltekst i vitenarkiv
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Dahl, Geir & Haufmann, Torkel Andreas (2016). Zero-one completely positive matrices and the A(R, S) classes. Special Matrices. ISSN 2300-7451. 4(1), s. 296–304. doi: 10.1515/spma-2016-0024. Fulltekst i vitenarkiv
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Barragan, Luis A.; Dahl, Geir; Dominguez, Alberto & Otin, Arantxa (2016). Zero sum sign-central matrices and applications . Linear Algebra and its Applications. ISSN 0024-3795. 505, s. 109–125. doi: 10.1016/j.laa.2016.04.034. Fulltekst i vitenarkiv
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Brualdi, Richard A. & Dahl, Geir (2015). Strict Sign-Central Matrices. SIAM Journal on Matrix Analysis and Applications. ISSN 0895-4798. 36(3), s. 1202–1220. doi: 10.1137/140995428.
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Dahl, Geir (2015). L-rays of permutation matrices and doubly stochastic matrices. Linear Algebra and its Applications. ISSN 0024-3795. 480, s. 127–143. doi: 10.1016/j.laa.2015.04.033.
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Dahl, Geir (2014). The Laplacian energy of threshold graphs and majorization. Linear Algebra and its Applications. ISSN 0024-3795. 469, s. 518–530. doi: 10.1016/j.laa.2014.12.002.
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Charina, Maria & Dahl, Geir (2014). Subdivision schemes, network flows and linear optimization. Advances in Computational Mathematics. ISSN 1019-7168. 41, s. 507–528. doi: 10.1007/s10444-014-9371-2.
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Abreu, Nair; Costa, Liliana; Dahl, Geir & Martins, Enide (2014). The skeleton of acyclic Birkhoff polytopes. Linear Algebra and its Applications. ISSN 0024-3795. 457, s. 29–48. doi: 10.1016/j.laa.2014.05.021.
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Brualdi, Richard A. & Dahl, Geir (2013). An extension of the polytope of doubly stochastic matrices. Linear and multilinear algebra. ISSN 0308-1087. 61(3), s. 393–408. doi: 10.1080/03081087.2012.689980. Fulltekst i vitenarkiv
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Dahl, Geir (2013). A note on majorization transforms and Ryser’s algorithm. Special Matrices. ISSN 2300-7451. 1, s. 17–24. doi: 10.2478/spma-2013-0004.
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Dahl, Geir & Zhang, Fuzhen (2013). Integral majorization polytopes. Discrete Mathematics, Algorithms and Applications (DMAA). ISSN 1793-8309. 5(3). doi: 10.1142/s1793830913500195. Fulltekst i vitenarkiv
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Brualdi, Richard A. & Dahl, Geir (2013). Majorization for partially ordered sets. Discrete Mathematics. ISSN 0012-365X. 313(22), s. 2592–2601. doi: 10.1016/j.disc.2013.08.003.
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Benth, Fred Espen; Dahl, Geir & Mannino, Carlo (2012). Computing Optimal Recovery Policies for Financial Markets. Operations Research. ISSN 0030-364X. 60(6), s. 1373–1388. doi: 10.1287/opre.1120.1112.
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Dahl, Geir (2012). A matrix-based ranking method with application to tennis. Linear Algebra and its Applications. ISSN 0024-3795. 437(1), s. 26–36. doi: 10.1016/j.laa.2012.02.002.
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Dahl, Geir (2012). Martingale matrix classes and polytopes. Linear Algebra and its Applications. ISSN 0024-3795. 437(7), s. 1722–1733. doi: 10.1016/j.laa.2012.04.042.
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Brualdi, R.A. & Dahl, Geir (2012). Majorization classes of integral matrices. Linear Algebra and its Applications. ISSN 0024-3795. 436(4), s. 802–813. doi: 10.1016/j.laa.2010.11.036.
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Dahl, Geir (2011). Polytopes related to interval vectors and incidence matrices. Linear Algebra and its Applications. ISSN 0024-3795. 435(11), s. 2955–2960. doi: 10.1016/j.laa.2011.05.026.
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Dahl, Geir & Minken, Harald (2010). A note on permutations and rank aggregation. Mathematical and computer modelling. ISSN 0895-7177. 52(1-2), s. 380–385. doi: 10.1016/j.mcm.2010.02.052.
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Dahl, Geir (2010). Majorization permutahedra and (0,1)-matrices. Linear Algebra and its Applications. ISSN 0024-3795. 432(12), s. 3265–3271. doi: 10.1016/j.laa.2010.01.024.
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Dahl, Geir (2009). Permutation matrices related to Sudoku. Linear Algebra and its Applications. ISSN 0024-3795. 430(8-9), s. 2457–2463. doi: 10.1016/j.laa.2008.12.023.
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Dahl, Geir (2009). Disjoint congruence classes and a timetabling application. Discrete Applied Mathematics. ISSN 0166-218X. 157(8), s. 1702–1710. doi: 10.1016/j.dam.2008.11.015. Fulltekst i vitenarkiv
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Dahl, Geir; Ball, Michael & Vossen, Thomas (2009). Matchings in Connection with Ground Delay Program Planning. Networks. ISSN 0028-3045. 53(3), s. 293–306. doi: 10.1002/net.20272.
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Dahl, Geir & Flatberg, Truls (2009). Reconstructing (0,1)-matrices from projections using integer programming. Computational optimization and applications. ISSN 0926-6003. 42(1), s. 141–154. doi: 10.1007/s10589-007-9116-y.
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Dahl, Geir & Minken, Harald (2008). Methods based on discrete optimization for finding road network rehabilitation strategies. Computers & Operations Research. ISSN 0305-0548. 35(7), s. 2193–2208. doi: 10.1016/j.cor.2006.10.015.
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Dahl, Geir (2008). Transportation matrices with staircase patterns and majorization. Linear Algebra and its Applications. ISSN 0024-3795. 429(7), s. 1840–1850.
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Dahl, Geir & Flatberg, Truls (2007). An Integer Programming Approach to Image Segmentation and Reconstruction Problems. I Hasle, Geir; Lie, Knut-Andreas & Quak, Ewald Gunther (Red.), Geometric Modelling, Numerical Simulation, and Optimization: Applied Mathematics at SINTEF. Springer Publishing Company. ISSN 978-3-540-68782-5. s. 461–481.
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Brualdi, R.A. & Dahl, Geir (2007). Constructing (0,1)-matrices with given line sums and certain fixed zeros. I Herman, Gabor & Kuba, Attila (Red.), Advances in Discrete Tomography and its Applications. Birkhäuser Verlag. ISSN 0-8176-3614-5.
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Dahl, Geir & Flatberg, Truls (2007). Reconstructing (0,1)-matrices from projections using integer programming. Computational optimization and applications. ISSN 0926-6003. s. 141–154.
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Dahl, Geir; Leinaas, Jon Magne; Myrheim, Jan & Ovrum, Eirik (2007). A tensor product matrix approximation problem in quantum physics. Linear Algebra and its Applications. ISSN 0024-3795. 420(2-3), s. 711–725. doi: 10.1016/j.laa.2006.08.026.
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Dahl, Geir (2007). A note on a parameter relating traffic equilibria and system optimal routing. Applied Mathematics and Computation. ISSN 0096-3003. 191, s. 445–450.
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Dahl, Geir (2021). Kombinatorikk, geometri og Munch!
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Dahl, Geir (2021). Doubly stochastic matrices: old and new results.
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Brualdi, R.A. & Dahl, Geir (2021). Diagonal sums of doubly stochastic matrices.
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Dahl, Geir; Munthe-Kaas, Antonella Zanna; Rønquist, Einar; Rypdal, Martin Wibe; Erfjord, Ingvald & Strømskag, Heidi [Vis alle 10 forfattere av denne artikkelen] (2021). Eksamen i matematikk er på ville veier. Aftenposten (morgenutg. : trykt utg.). ISSN 0804-3116.
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Dahl, Geir (2019). Majorization - some recent developments in matrix theory.
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Dahl, Geir; Brualdi, R.A.; Guterman, Alexander & Shteyner, Pavel (2019). Matrix covering problems.
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Andrade, Enide; Dahl, Geir; Leal, Laura & Robbiano, Maria (2019). New bounds for the signless Laplacian spread.
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Brualdi, R.A. & Dahl, Geir (2019). Matrix covering and A-interval matrices.
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Dahl, Geir; Andrade, Enide & Ciardo, Lorenzo (2018). Combinatorial Perron Parameters and Trees.
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Dahl, Geir & Brualdi, R.A. (2018). Alternating Sign Matrices, Polyhedra and Majorization.
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Dahl, Geir; Ranestad, Kristian & Hole, Arne (2017). Programmering rammer dybdelæring i matematikk. Aftenposten (morgenutg. : trykt utg.). ISSN 0804-3116. s. 22–23.
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Dahl, Geir (2017). Laplacian energy, threshold graphs and majorization.
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Brualdi, R.A. & Dahl, Geir (2017). Alternating sign matrices and related polyhedra.
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Brualdi, R.A. & Dahl, Geir (2017). Alternating sign matrices and polyhedra.
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Andrade, Enide & Dahl, Geir (2016). Combinatorial Perron values.
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Andrade, Enide & Dahl, Geir (2016). Combinatorial Perron values.
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Dahl, Geir & Brualdi, R.A. (2016). Doubly stochastic matrices and the Bruhat order.
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Dahl, Geir & Haufmann, Torkel Andreas (2016). Zero-one completely positive matrices and the A(R,S )matrix classes.
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Haufmann, Torkel Andreas; Agra, Agostinho; Dahl, Geir & Pinheiro, Sofia (2016). The k-regular induced subgraph problem.
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Dahl, Geir (2016). Some Topics in Combinatorial Matrix Theory.
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Dahl, Geir (2015). Combinatorial Matrix Theory and Majorization.
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Agra, Agostinho; Dahl, Geir; Haufmann, Torkel Andreas & Pinheiro, Sofia (2015). Maximal induced k-regular subgraphs.
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Agra, Agostinho; Dahl, Geir; Haufmann, Torkel Andreas & Pinheiro, Sofia (2015). The k-regular induced subgraph problem for k=1,2.
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Dahl, Geir (2015). Permutation matrices, doubly stochastic matrices and their L– rays .
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Dahl, Geir (2015). Majorization, (0,1)-matrices and Laplacian energy.
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Dahl, Geir & Brualdi, R.A. (2014). Majorization for partially ordered sets.
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Dahl, Geir (2014). Majorization and combinatorial matrix theory.
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Dahl, Geir (2014). Traveling Salesman Problem: En matematisk rundtur.
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Haufmann, Torkel Andreas & Dahl, Geir (2014). Optimization and classes of completely positive matrices.
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Dahl, Geir (2013). Nytt Munch museum: et SKRIK etter kombinatorikk og geometri!!
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Dahl, Geir (2013). An introduction to Majorization: theory and applications.
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Dahl, Geir (2013). Majorization transforms and Ryser’s algorithm.
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Brualdi, R.A. & Dahl, Geir (2012). An extension of the polytope of doubly stochastic matrices.
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Dahl, Geir & Brualdi, R.A. (2012). Generalized Birkhoff polytopes and majorization.
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Bebiano, Natália; Dahl, Geir; da Silva, José Dias & da Fonseca, Carlos M. (2012). Preface to the Proceedings of the Coimbra Meeting on 0-1 Matrix Theory and Related Topics. Linear Algebra and its Applications. ISSN 0024-3795. 436(4), s. 789–790. doi: 10.1016/j.laa.2011.09.028.
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Dahl, Geir (2012). A taste of Szemerédi's combinatorics.
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Dahl, Geir (2012). Google: hvordan man blir styrtrik på en matematisk likning!
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Dahl, Geir (2012). Majorization, matrix polytopes and combinatorics.
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Dahl, Geir (2012). Lineær algebra, Google og rangering av websider.
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Dahl, Geir (2011). Kombinatorikk på roterommet!
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Dahl, Geir (2011). Majorization in matrix theory: a brief introduction and some recent progress.
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Dahl, Geir (2011). Martingale matrix classes.
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Dahl, Geir (2010). Majorization and related combinatorial matrix classes.
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Dahl, Geir (2010). Majorization permutahedra and (0,1)-matrices.
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Dahl, Geir (2010). Majorization, A(R,S) and related matrix classes.
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Dahl, Geir (2009). Majorization and network problems.
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Dahl, Geir (2009). Disjoint congruence classes and an optimization problem.
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Dahl, Geir (2009). Introduction to optimization and convexity.
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Dahl, Geir (2008). Majorization in matrix theory: a brief introduction.
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Dahl, Geir (2008). Minimum cuts: theory and algorithms.
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Dahl, Geir (2008). Matematisk spillteori - analyse av Nash likevekt.
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Dahl, Geir & Dahl, Kristina Rognlien (2012). Linear optimization and mathematical finance. University of Oslo. ISSN 0806-2439. Fulltekst i vitenarkiv
Publisert 24. okt. 2010 15:45
- Sist endret 8. mai 2020 09:50