[HTML][HTML] A computational technique in Coxeter spectral study of symmetrizable integer Cartan matrices

D Simson - Linear Algebra and its Applications, 2020 - Elsevier
With any symmetrizable integer Cartan matrix C∈ SC arn⊆ M n (Z), a Z-invertible Coxeter
matrix Cox C∈ M n (Z) is associated. We study such positive definite matrices up to a strong …

Symbolic algorithms computing Gram congruences in the Coxeter spectral classification of edge-bipartite graphs, I. A Gram classification

D Simson - Fundamenta Informaticae, 2016 - content.iospress.com
We continue the Coxeter spectral study of the category 𝒰ℬigr m of loop-free edge-bipartite
(signed) graphs Δ, with m≥ 2 vertices, we started in [SIAM J. Discr. Math. 27 (2013), 827 …

Symbolic algorithms computing Gram congruences in the Coxeter spectral classification of edge-bipartite graphs, II. Isotropy mini-groups

D Simson - Fundamenta Informaticae, 2016 - content.iospress.com
In this two parts article with the same title we continue the Coxeter spectral study of the
category 𝒰ℬigr m of loop-free edge-bipartite (signed) graphs Δ, with m≥ 2 vertices, we …

Weyl orbits of matrix morsifications and a Coxeter spectral classification of positive signed graphs and quasi-Cartan matrices of Dynkin type An

D Simson - Advances in Mathematics, 2022 - Elsevier
By applying an advanced technique of Weyl orbits of matrix morsifications of Dynkin graphs
we obtain a complete classification (up to the strong Gram Z-congruence) of the connected …

[HTML][HTML] A Coxeter spectral classification of positive edge-bipartite graphs I. Dynkin types Bn, Cn, F4, G2, E6, E7, E8

D Simson - Linear Algebra and its Applications, 2018 - Elsevier
We develop a computational technique for classification of a class of signed graphs (called
edge-bipartite graphs), we started in Simson (2013)[42] and Bocian et al.(2014)[6]. Here we …

Congruences of edge-bipartite graphs with applications to Grothendieck group recognition I. Inflation algorithm revisited

A Mróz - Fundamenta INFormaticae, 2016 - content.iospress.com
We study edge-bipartite graphs (bigraphs), a class of signed graphs, by means of the
inflation algorithm which relies on performing certain elementary transformations on a given …

Inflation agorithm for Cox-regular postive edge-bipartite graphs with loops

B Makuracki, D Simson… - Fundamenta Informaticae, 2017 - content.iospress.com
We continue the study of finite connected edge-bipartite graphs Δ, with m≥ 2 vertices (a
class of signed graphs), started in [SIAM J. Discrete Math. 27 (2013), 827-854] and …

[HTML][HTML] Inflation algorithm for loop-free non-negative edge-bipartite graphs of corank at least two

D Simson, K Zając - Linear Algebra and its Applications, 2017 - Elsevier
We continue the study of finite connected loop-free edge-bipartite graphs Δ, with m≥ 3
vertices (a class of signed graphs), we started in Simson (2013)[48] and M. Gąsiorek et …

Quadratic algorithm to compute the Dynkin type of a positive definite quasi-Cartan matrix

B Makuracki, A Mróz - Mathematics of Computation, 2021 - ams.org
Cartan matrices and quasi-Cartan matrices play an important role in such areas as Lie
theory, representation theory, and algebraic graph theory. It is known that each (connected) …

Numeric algorithms for corank two edge-bipartite graphs and their mesh geometries of roots

K Zając - Fundamenta Informaticae, 2017 - content.iospress.com
Following a Coxeter spectral analysis problems for positive edge-bipartite graphs (signed
multigraphs with a separation property) introduced in [SIAM J. Discr. Math. 27 (2013), 827 …