Publications

The edge-isoperimetric number of graphs and their powers

A. Abiad, N. van de Berg, E. Juliano, H. Reijnders, R. Simoens, T. van Veluw, J. Wittebol

Discrete Mathematics 350(2), 115442 (2027)DOIarXivBibTeXCite

Published online; assigned to the February 2027 issue.

A graph energy conjecture through the lenses of semidefinite programming

A Abiad, G Coutinho, E Juliano, H. Reijnders

SIAM Journal on OptimizationAcceptedarXivBibTeXCite

A lifted entropy splitting lemma and applications

G Coutinho, L Higino

PreprintarXivBibTeXCite

A Lovász Theta Parameter and Theta Body for Signed Graphs

G Coutinho

PreprintarXivBibTeXCite

A SWAP-free Framework for QAOA

T Assis, P Baptista, L Lopes, D Ferreira, G Coutinho

PreprintarXivBibTeXCite

Clique and chromatic numbers of graph powers: spectral bounds and anticodes

A Abiad, G Coutinho, H Kumar, E Juliano, M Tait

PreprintarXivBibTeXCite

Compact graphs and quantum automorphisms

P Baptista, G Coutinho, C Godsil, S Schmidt

PreprintarXivBibTeXCite

Computing fixed point free automorphisms of graphs

A Abiad, G Coutinho, E Juliano, V dos Santos, S Zeijlemaker

LATIN 2026AcceptedarXivBibTeXCite

Conference version accepted at LATIN 2026; journal version submitted.

On some k-fold generalizations of Lovász theta and their sandwich theorems

MKC Silva, G Coutinho, T Oliveira, L Tunçel

PreprintarXivBibTeXCite

On the zero-free region for the chromatic polynomial of graphs with maximum degree Δ and girth g

P. M. S. Fialho, E. Juliano, A. Procacci

Discrete Mathematics 349(3), 114825 (2026)DOIarXivBibTeXCite

Semidefinite programming bounds on fractional cut-cover and maximum 2-SAT for highly regular graphs

H Assumpção, G Coutinho

Mathematics of Operations Research 2026DOIarXivBibTeXCite

Tightness of a MaxCut Lower Bound via Vector Chromatic Number

E. Juliano

The Electronic Journal of Combinatorics 33(3), P3.69 (2026)DOIarXivBibTeXCite

Total Conformal Rigidity in Graphs

H Assumpção, G Coutinho, C Godsil

PreprintarXivBibTeXCite

Two chromatic numbers, eigenvalues and a generalized Lovász theta

MK Silva, G Coutinho, R Grandsire

Special Matrices 14(1), 20250060 (2026)DOIarXivBibTeXCite

Zero-freeness of a multivariate monomer-dimer-cycle polynomial on bounded-degree graphs

G Coutinho, PMS Fialho

PreprintarXivBibTeXCite

A connection between the Aα-spectrum and the Lovász theta number

G Coutinho, T Oliveira

Linear Algebra and Its Applications 2025arXivPaperBibTeXCite

A mathematical foundation for self-testing: Lifting common assumptions

P. Baptista, R. Chen, J. Kaniewski, D. R. Lolck, L. Mančinska, T. G. Nielsen, S. Schmidt

Annales Henri Poincaré 2025DOIarXivBibTeXCite

A remark on the Whitney Broken Circuit Theorem

P. M. S. Fialho, E. Juliano, A. Procacci

Computational and Applied Mathematics 2025DOIarXivBibTeXCite

On the independent set polynomial of graphs and claw-free graphs

Paula M. S. Fialho, Aldo Procacci

PreprintarXivBibTeXCite

Orthogonal polynomials, quantum walks and the Prouhet–Tarry–Escott problem

F Cançado, G Coutinho, TJ Spier

PreprintarXivBibTeXCite

Peak state transfer in continuous quantum walks

G Coutinho, K Guo, V Schmeits

PreprintarXivBibTeXCite

Quantum Sabidussi's Theorem

A. S. Árnadóttir, J. van Dobben de Bruyn, P. N. Kar, D. E. Roberson, P. Zeman

Journal of the London Mathematical Society 2025DOIarXivBibTeXCite

Spectral upper bounds for the Grundy number of a graph

T Assis, G Coutinho, E Juliano

Discrete Mathematics 348(3), 114326 (2025)DOIarXivBibTeXCite

The spectrum of symmetric decorated paths

G Coutinho, E Juliano, TJ Spier

Linear Algebra and Its Applications 2025arXivPaperBibTeXCite

Unsupervised Hierarchical Sequence Stratigraphy Framework of Carbonate Successions

MVS Dantas, KHM Vieira, TJ Spier, JAO Santos, ACT Prado, D Vomlel, M Leite, FA Farias, DGC Fragoso, H Reis, G Coutinho, DG Macharet

Artificial Inteligence in Geosciences 2025PaperBibTeXCite

Conic programming to understand sums of squares of eigenvalues of graphs

G Coutinho, TJ Spier, S Zhang

PreprintarXivBibTeXCite

(this paper heavily supersedes the earlier preprint by Thomás and I)

Forbidden subdivision in integral trees

E. Juliano

PreprintarXivBibTeXCite

Matching (Multi)Cut: Algorithms, Complexity, and Enumeration

G. C. M. Gomes, E. Juliano, G. Martins, V. F. dos Santos

IPEC 2024DOIarXivBibTeXCite

No perfect state transfer in trees with more than 3 vertices

G Coutinho, E Juliano, TJ Spier

Journal of Combinatorial Theory Series B 2024DOIarXivBibTeXCite

Quotient graphs and stochastic matrices

F Cançado, G Coutinho

PreprintarXivBibTeXCite

Selected Open Problems in Continuous-Time Quantum Walks

G Coutinho, K Guo

Special Matrices 2024DOIarXivBibTeXCite

Unexpected Averages of Mixing Matrices

P Baptista, G Coutinho, V Marques

Quantum Information Processing 2024DOIarXivBibTeXCite

Constructing high-resolution stratigraphic frameworks by the application of signal analysis techniques: Example of Balbuena IV Sequence, Yacoraite Formation, Salta Basin

JAO Santos, A Uhlein, MVS Dantas, G Coutinho, TJ Spier, KHM Vieira, ACT Prado, D Macharet, GJ Uhlein, T Novo, H Reis, FA Farias, EB Freire, DGC Fragoso

Marine and Petroleum Geology 2023PaperBibTeXCite

Irrational quantum walks

G Coutinho, PF Baptista, C Godsil, TJ Spier, R Werner

SIAM Journal of Applied Algebra and Geometry 2023DOIarXivBibTeXCite

Quantum Walks in the Normalized Laplacian

G Coutinho, PF Baptista

Linear and Multilinear Algebra 2023DOIarXivBibTeXCite

Strong cospectrality in trees

G Coutinho, E Juliano, TJ Spier

Algebraic Combinatorics 2023DOIarXivBibTeXCite

Why and how to add direction to a quantum walk

R Chaves, BO Chagas, G Coutinho

Quantum Information Processing 2023DOIarXivBibTeXCite

A novel reconstruction attack on foreign-trade official statistics, with a Brazilian case study

DF Favato, G Coutinho, MS Alvim, N Fernandes

PoPETS 2022arXivPaperBibTeXCite

Fundamentals of fractional revival in graphs

A Chan, G Coutinho, W Drazen, O Eisenberg, C Godsil, M Kempton, G Lippner, C Tamon, H Zhan

Linear Algebra and its Applications 655 (2022), 129–158DOIarXivBibTeXCite

Optimization of eigenvalue bounds for the independence and chromatic number of graph powers

A Abiad, G Coutinho, MA Fiol, BD Nogueira, S Zeijlemaker

Discrete Mathematics 2022arXivPaperBibTeXCite

Quantum walks do not like bridges

G Coutinho, C Godsil, E Juliano, CM van Bommel

Linear Algebra and Its Applications 2022arXivPaperBibTeXCite

Dual Hoffman Bounds for the Stability and Chromatic Numbers Based on Semidefinite Programming

NB Proença, MK de Carli Silva, G Coutinho

SIAM Journal on Discrete Mathematics 2021DOIarXivBibTeXCite

Fractional revival and association schemes

A Chan, G Coutinho, C Tamon, L Vinet, H Zhan

Discrete Mathematics 2020arXivPaperBibTeXCite

Algebras, graphs and thetas

MK de Carli Silva, G Coutinho, C Godsil, DE Roberson

LAGOS 2019arXivPaperBibTeXCite

Colouring the normalized Laplacian

G Coutinho, R Grandsire, C Passos

LAGOS 2019arXivPaperBibTeXCite

Discretization of continuous-time quantum walks via the staggered model with Hamiltonians

G Coutinho, R Portugal

Natural Computing 2019DOIarXivBibTeXCite

On the k-independence number of graphs

A Abiad, G Coutinho, MA Fiol

Discrete Mathematics 2019arXivPaperBibTeXCite

Perfect state transfer in a spin chain without mirror symmetry

G Coutinho, L Vinet, H Zhan, A Zhedanov

Journal of Physics A: Mathematical and Theoretical 2019DOIarXivBibTeXCite

Quantum fractional revival on graphs

A Chan, G Coutinho, C Tamon, L Vinet, H Zhan

Discrete Applied Mathematics 2019arXivPaperBibTeXCite

Quantum walks and the size of the graph

G Coutinho

Discrete Mathematics 2019arXivPaperBibTeXCite

A New Perspective on the Average Mixing Matrix

G Coutinho, C Godsil, K Guo, H Zhan

The Electronic Journal of Combinatorics 2018arXivPaperBibTeXCite

Continuous-Time Quantum Walks in Graphs

G Coutinho, C Godsil

IMAGE — The Bulletin of the International Linear Algebra Society 60 (2018), 12–21PaperBibTeXCite

Perfect state transfer is poly-time

G Coutinho, C Godsil

Quantum Information & Computation 2017arXivPaperBibTeXCite

Pretty good state transfer between internal nodes of paths

G Coutinho, K Guo, CM van Bommel

Quantum Information & Computation 2017DOIarXivBibTeXCite

Pretty good state transfer in qubit chains—The Heisenberg Hamiltonian

L Banchi, G Coutinho, C Godsil, S Severini

Journal of Mathematical Physics 2017DOIarXivBibTeXCite

Equiangular Lines and Covers of the Complete Graph

G Coutinho, C Godsil, M Shirazi, H Zhan

Linear Algebra and Its Applications 2016arXivPaperBibTeXCite

Perfect state transfer in products and covers of graphs

G Coutinho, C Godsil

Linear and Multilinear Algebra 2016DOIarXivBibTeXCite

Spectrally extremal vertices, strong cospectrality, and state transfer

G Coutinho

The Electronic Journal of Combinatorics 2016arXivPaperBibTeXCite

No Laplacian Perfect State Transfer in Trees

G Coutinho, H Liu

SIAM Journal of Discrete Mathematics 2015DOIarXivBibTeXCite

Perfect state transfer on distance-regular graphs and association schemes

G Coutinho, C Godsil, K Guo, F Vanhove

Linear Algebra and its Applications 478 (2015), 108–130DOIarXivBibTeXCite