Research Article

Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices

Number: Advanced Online Publication Early Pub Date: August 17, 2026
TR EN

Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices

Abstract

Cartan numbers form a four-dimensional real algebra with a mixed hyperbolic--nilpotent structure and an indefinite quadratic character, which precludes the induced modulus from defining a norm and distinguishes their matrix theory from that of classical hypercomplex systems. In this paper, we develop a systematic framework for matrices over the algebra of Cartan numbers by introducing a complex $2\times 2$ representation that establishes an algebra isomorphism between $\mathbb{S}$ and a Hermitian-type subalgebra of $M_{2}(\mathbb{C})$. Based on this representation, we define the complex adjoint matrix $\Xi_{\mathbf{K}}$, prove the identity $\Xi_{\mathbf{K}\mathbf{M}}=\Xi_{\mathbf{K}}\Xi_{\mathbf{M}}$, and show that the invertibility of $\mathbf{K}$ is equivalent to that of $\Xi_{\mathbf{K}}$, leading to the definition of a $q$-determinant with multiplicativity and similarity invariance properties. We further investigate right eigenvalues and generalized right eigenvalues of Cartan number matrices and matrix pencils, demonstrating that non-real Cartan eigenvalues generate infinite similarity orbits and that the complex spectra of $\Xi_{\mathbf{K}}$ fully characterize eigenvalues in $\mathbb{C}$.

Keywords

Supporting Institution

This research received no external funding.

Project Number

Not applicable

Ethical Statement

Ethical approval was not required for this study.

Thanks

The authors are thankful to the reviewers and the editors for their valuable comments and constructive suggestions, which significantly improved the quality of the manuscript.

References

  1. [1] S.S. Ahmad and I. Ali, Bounds for eigenvalues of matrix polynomials over quaternion division algebra, Adv. Appl. Clifford Algebras 26 (4), 1095–1125, 2016.

Details

Primary Language

English

Subjects

Algebra and Number Theory

Journal Section

Research Article

Early Pub Date

August 17, 2026

Publication Date

-

Submission Date

February 26, 2026

Acceptance Date

June 5, 2026

Published in Issue

Year 2026 Number: Advanced Online Publication

APA
Çakır, H., Öztürk, İ., & Özdemir, M. (2026). Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices. Hacettepe Journal of Mathematics and Statistics, Advanced Online Publication. https://doi.org/10.15672/hujms.1898416
AMA
1.Çakır H, Öztürk İ, Özdemir M. Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices. Hacettepe Journal of Mathematics and Statistics. 2026;(Advanced Online Publication). doi:10.15672/hujms.1898416
Chicago
Çakır, Hasan, İskender Öztürk, and Mustafa Özdemir. 2026. “Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices”. Hacettepe Journal of Mathematics and Statistics, no. Advanced Online Publication. https://doi.org/10.15672/hujms.1898416.
EndNote
Çakır H, Öztürk İ, Özdemir M (August 1, 2026) Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices. Hacettepe Journal of Mathematics and Statistics Advanced Online Publication
IEEE
[1]H. Çakır, İ. Öztürk, and M. Özdemir, “Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices”, Hacettepe Journal of Mathematics and Statistics, no. Advanced Online Publication, Aug. 2026, doi: 10.15672/hujms.1898416.
ISNAD
Çakır, Hasan - Öztürk, İskender - Özdemir, Mustafa. “Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices”. Hacettepe Journal of Mathematics and Statistics. Advanced Online Publication (August 1, 2026). https://doi.org/10.15672/hujms.1898416.
JAMA
1.Çakır H, Öztürk İ, Özdemir M. Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices. Hacettepe Journal of Mathematics and Statistics. 2026. doi:10.15672/hujms.1898416.
MLA
Çakır, Hasan, et al. “Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices”. Hacettepe Journal of Mathematics and Statistics, no. Advanced Online Publication, Aug. 2026, doi:10.15672/hujms.1898416.
Vancouver
1.Hasan Çakır, İskender Öztürk, Mustafa Özdemir. Complex Adjoint Representations and Eigenvalue Theory for Cartan Number Matrices. Hacettepe Journal of Mathematics and Statistics. 2026 Aug. 1;(Advanced Online Publication). doi:10.15672/hujms.1898416