Editorial to Special issue “Workshop on Spectral Graph Theory 2023 – In honor of Prof. Nair Abreu”
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Milica Anđelić
This special issue of Special Matrices is dedicated to the Workshop on Spectral Graph Theory 2023 (WSGT 2023), a conference in honor of Nair Abreu for her (70+3)rd birthday, held in Niterói, Rio de Janeiro, Brazil, from October 24 to 27, 2023. This workshop was attended by eminent researchers in the field, in addition to attracting young researchers and graduate students. In total, 75 researchers from Brazil, Germany, The Netherlands, Denmark, France, USA, Canada, India, China, Argentina, Chile, and Uruguay participated in this meeting.
It was organized by the TEG-Brazil (acronym for Spectral Graph Theory in Portuguese). This group started in 2002 led by Professor Nair Abreu and it was initially composed by mathematicians, computer scientists and students from several institutions in Rio de Janeiro and Niterói. Shortly afterwards, a new SGT research center was created in Porto Alegre, south of Brazil, with strong interaction with the Rio group. Today we have researchers in this area spread across the four corners of the country. This remarkable growth of SGT is due in great deal to the diligent work of Nair Abreu.
Professor Nair Abreu is the pioneer researcher in Spectral Graph Theory in Brazil. Her interest on that theme was initiated in 2001, when she attended an important event in Scotland: Euro Workshop on Algebraic Graph Theory. Many of the researchers that Nair met on that occasion, later visited Brazil, invited by her. Among the papers published by Nair Abreu, we highlight the seminal “Old and new results on algebraic connectivity of graphs,” a mandatory reference for algebraic connectivity, an important topic in SGT.
In 2008, Professor Nair Abreu organized the Workshop on Spectral Graph Theory, WSGT in Rio 2008. This was a memorable event that brought together the most important researchers in the field, including the pioneers Dragos Cvetković and Miroslav Fiedler. More recently, in 2019 Professor Nair lead the organization of the 22st Conference of the International Linear Algebra Society (ILAS 2019) in Rio de Janeiro. This is the most important event organized by the International Linear Algebra Society and was the first time that happened in Latin America.
The SGT Brazilian community is very grateful for her contributions, generosity and kindness. To conclude, we give the floor to Nair, borrowing the following sentence from her speech:
During this period of life, I had the joy to meet new colleagues, students and friends. It's funny to imagine that such concrete and solid friendships are born from abstract properties!
This special issue comprises the following articles:
“Eigenvalues of complex unit gain graphs and gain regularity” by Maurizio Brunetti, https://doi.org/10.1515/spma-2024-0005.
“Note on the product of the largest and the smallest eigenvalue of a graph” by Aida Abiad, Cristina Dalfó, Miquel Àngel Fiol, https://doi.org/10.1515/spma-2024-0008.
“Four-point condition matrices of edge-weighted trees” Ali Azimi, Rakesh Jana, Mukesh K. Nagar, Sivaramakrishnan Sivasubramanian, https://doi.org/10.1515/spma-2024-0011.
“On the Laplacian index of tadpole graphs” by Rodrigo O. Braga, Bruno S. Veloso, https://doi.org/10.1515/spma-2024-0019.
“Signed graphs with strong (anti-)reciprocal eigenvalue property” by Francesco Belardo, Callum Huntington, https://doi.org/10.1515/spma-2024-0017.
“Some results involving the Aα-eigenvalues for graphs and line graphs” by João Domingos G. da Silva Júnior, Carla Silva Oliveira, Liliana Manuela G. C. da Costa, https://doi.org/10.1515/spma-2024-0016.
“A generalization of the Graham-Pollak tree theorem to even-order Steiner distance” by Joshua Cooper, Gabrielle Tauscheck, https://doi.org/10.1515/spma-2024-0018.
“Nonvanishing minors of eigenvector matrices and consequences” by Tarek Emmrich, https://doi.org/10.1515/spma-2024-0020.
“A linear algorithm for obtaining the Laplacian eigenvalues of a cograph” Guantao Chen, Fernando C. Tura, https://doi.org/10.1515/spma-2024-0024.
“On the minimum spectral radius of connected graphs of given order and size” by Sebastian M. Cioaba, Vishal Gupta and Celso Marques, https://doi.org/10.1515/spma-2024-0027.
“Graphs whose Laplacian eigenvalues are almost all 1 or 2” by Shanshan Xu and Ali Mohammadian, https://doi.org/10.1515/spma-2024-0015.
“A Laplacian eigenbasis for threshold graphs” by Rafael R. Macharete, Renata R. Del-Vecchio, Heber Teixeira, Leonardo de Lima, https://doi.org/10.1515/spma-2024-0029.
“Selected open problems in continuous-time quantum walks” by Gabriel Coutinho, Krystal Guo, https://doi.org/10.1515/spma-2024-0025.
© 2024 the author(s), published by De Gruyter
This work is licensed under the Creative Commons Attribution 4.0 International License.
Articles in the same Issue
- Research Articles
- The diameter of the Birkhoff polytope
- Determinants of tridiagonal matrices over some commutative finite chain rings
- The smallest singular value anomaly: The reasons behind sharp anomaly
- Idempotents which are products of two nilpotents
- Two-unitary complex Hadamard matrices of order 36
- Lih Wang's and Dittert's conjectures on permanents
- On a unified approach to homogeneous second-order linear difference equations with constant coefficients and some applications
- Matrix equation representation of the convolution equation and its unique solvability
- Disjoint sections of positive semidefinite matrices and their applications in linear statistical models
- On the spectrum of tridiagonal matrices with two-periodic main diagonal
- γ-Inverse graph of some mixed graphs
- On the Harary Estrada index of graphs
- Complex Palais matrix and a new unitary transform with bounded component norms
- Computing the matrix exponential with the double exponential formula
- Special Issue in honour of Frank Hall
- Editorial Note for the Special Issue in honor of Frank J. Hall
- Refined inertias of positive and hollow positive patterns
- The perturbation of Drazin inverse and dual Drazin inverse
- The minimum exponential atom-bond connectivity energy of trees
- Singular matrices possessing the triangle property
- On the spectral norm of a doubly stochastic matrix and level-k circulant matrix
- New constructions of nonregular cospectral graphs
- Variations in the sub-defect of doubly substochastic matrices
- Eigenpairs of adjacency matrices of balanced signed graphs
- Special Issue - Workshop on Spectral Graph Theory 2023 - In honor of Prof. Nair Abreu
- Editorial to Special issue “Workshop on Spectral Graph Theory 2023 – In honor of Prof. Nair Abreu”
- Eigenvalues of complex unit gain graphs and gain regularity
- Note on the product of the largest and the smallest eigenvalue of a graph
- Four-point condition matrices of edge-weighted trees
- On the Laplacian index of tadpole graphs
- Signed graphs with strong (anti-)reciprocal eigenvalue property
- Some results involving the Aα-eigenvalues for graphs and line graphs
- A generalization of the Graham-Pollak tree theorem to even-order Steiner distance
- Nonvanishing minors of eigenvector matrices and consequences
- A linear algorithm for obtaining the Laplacian eigenvalues of a cograph
- Selected open problems in continuous-time quantum walks
- On the minimum spectral radius of connected graphs of given order and size
- Graphs whose Laplacian eigenvalues are almost all 1 or 2
- A Laplacian eigenbasis for threshold graphs
Articles in the same Issue
- Research Articles
- The diameter of the Birkhoff polytope
- Determinants of tridiagonal matrices over some commutative finite chain rings
- The smallest singular value anomaly: The reasons behind sharp anomaly
- Idempotents which are products of two nilpotents
- Two-unitary complex Hadamard matrices of order 36
- Lih Wang's and Dittert's conjectures on permanents
- On a unified approach to homogeneous second-order linear difference equations with constant coefficients and some applications
- Matrix equation representation of the convolution equation and its unique solvability
- Disjoint sections of positive semidefinite matrices and their applications in linear statistical models
- On the spectrum of tridiagonal matrices with two-periodic main diagonal
- γ-Inverse graph of some mixed graphs
- On the Harary Estrada index of graphs
- Complex Palais matrix and a new unitary transform with bounded component norms
- Computing the matrix exponential with the double exponential formula
- Special Issue in honour of Frank Hall
- Editorial Note for the Special Issue in honor of Frank J. Hall
- Refined inertias of positive and hollow positive patterns
- The perturbation of Drazin inverse and dual Drazin inverse
- The minimum exponential atom-bond connectivity energy of trees
- Singular matrices possessing the triangle property
- On the spectral norm of a doubly stochastic matrix and level-k circulant matrix
- New constructions of nonregular cospectral graphs
- Variations in the sub-defect of doubly substochastic matrices
- Eigenpairs of adjacency matrices of balanced signed graphs
- Special Issue - Workshop on Spectral Graph Theory 2023 - In honor of Prof. Nair Abreu
- Editorial to Special issue “Workshop on Spectral Graph Theory 2023 – In honor of Prof. Nair Abreu”
- Eigenvalues of complex unit gain graphs and gain regularity
- Note on the product of the largest and the smallest eigenvalue of a graph
- Four-point condition matrices of edge-weighted trees
- On the Laplacian index of tadpole graphs
- Signed graphs with strong (anti-)reciprocal eigenvalue property
- Some results involving the Aα-eigenvalues for graphs and line graphs
- A generalization of the Graham-Pollak tree theorem to even-order Steiner distance
- Nonvanishing minors of eigenvector matrices and consequences
- A linear algorithm for obtaining the Laplacian eigenvalues of a cograph
- Selected open problems in continuous-time quantum walks
- On the minimum spectral radius of connected graphs of given order and size
- Graphs whose Laplacian eigenvalues are almost all 1 or 2
- A Laplacian eigenbasis for threshold graphs
