Abstract
We consider the algebra \(\square _{q}\) which is a mild generalization of the quantum algebra \(U_{q}(\frak {sl}_{2})\). The algebra \(\square _{q}\) is defined by generators and relations. The generators are \(\{x_{i}\}_{i\in \mathbb {Z}_{4}}\), where \(\mathbb {Z}_{4}\) is the cyclic group of order 4. For \(i\in \mathbb {Z}_{4}\) the generators xi,xi+ 1 satisfy a q-Weyl relation, and xi,xi+ 2 satisfy a cubic q-Serre relation. For \(i\in \mathbb {Z}_{4}\) we show that the action of xi is invertible on every nonzero finite-dimensional \(\square _{q}\)-module. We view \(x_{i}^{-1}\) as an operator that acts on nonzero finite-dimensional \(\square _{q}\)-modules. For \(i\in \mathbb {Z}_{4}\), define \(\mathfrak {n}_{i,i + 1}=q(1-x_{i}x_{i + 1})/(q-q^{-1})\). We show that the action of \(\mathfrak {n}_{i,i + 1}\) is nilpotent on every nonzero finite-dimensional \(\square _{q}\)-module. We view the q-exponential \(\text {{exp}}_{q}(\mathfrak {n}_{i,i + 1})\) as an operator that acts on nonzero finite-dimensional \(\square _{q}\)-modules. In our main results, for \(i,j\in \mathbb {Z}_{4}\) we express each of \(\text {{exp}}_{q}(\mathfrak {n}_{i,i + 1})x_{j}\text {{exp}}_{q}(\mathfrak {n}_{i,i + 1})^{-1}\) and \(\text {{exp}}_{q}(\mathfrak {n}_{i,i + 1})^{-1}x_{j}\text {{exp}}_{q}(\mathfrak {n}_{i,i + 1})\) as a polynomial in \(\{x_{k}^{\pm 1}\}_{k\in \mathbb {Z}_{4}}\).
Similar content being viewed by others
References
Alnajjar, H.: Leonard pairs associated with the equitable generators of the quantum algebra \(u_{q}(\mathfrak {sl}_{2})\). Linear Multilinear Algebra 59, 1127–1142 (2011)
Baseilhac, P.: An integrable structure related with tridiagonal algebras. Nuclear Phys. B 705, 605–619 (2005)
Funk-Neubauer, D.: Bidiagonal pairs, the Lie algebra \(\mathfrak {sl}_{2}\), and the quantum group \(U_{q}(\mathfrak {sl}_{2})\). J. Algebra Appl. 12, 1250207, 46 (2013)
Huang, H.: The classification of Leonard triples of QRacah type. Linear Algebra Appl. 436, 1442–1472 (2012)
Miki, K.: Finite dimensional modules for the q-tetrahedron algebra. Osaka J. Math. 47(2), 559–589 (2010)
Ito, T., Rosengren, H., Terwilliger, P.: Evaluation modules for the q-tetrahedron algebra. Linear Algebra Appl. 451, 107–168 (2014)
Ito, T., Terwilliger, P.: Tridiagonal pairs and the quantum affine algebra uq(sl2). Ramanujan J. 13, 39–62 (2007)
Ito, T., Terwilliger, P.: Two non-nilpotent linear transformations that satisfy the cubic q-Serre relations. J. Algebra Appl. 6, 477–503 (2007)
Ito, T., Terwilliger, P.: The q-tetrahedron algebra and its finite-dimensional irreducible modules. Comm. Algebra 35, 3415–3439 (2007)
Ito, T., Terwilliger, P., Weng, C.: The quantum algebra \(u_{q}(\mathfrak {sl}_{2})\) and its equitable presentation. J. Algebra 298, 284–301 (2006)
Lusztig, G.: Quantum deformations of certain simple modules over enveloping algebras. Adv. Math. 70, 237–249 (1988)
Lusztig, G.: On quantum groups. J. Algebra 131, 464–475 (1990)
Tanisaki, T.: Lie algebras and quantum groups. Kyoritsu Publishers, Tokyo (2002)
Terwilliger, P.: The equitable presentation for the quantum group \(u_{q}(\mathfrak {g})\) associated with a symmetrizable Kac-Moody algebra \(\mathfrak {g}\). J. Algebra 298, 302–319 (2006)
Terwilliger, P.: The universal Askey-Wilson algebra and the equitable presentation of \(U_{q}(\mathfrak {sl}_{2})\). SIGMA 7, 099, 26 (2011)
Terwilliger, P.: Finite-dimensional irreducible \(u_{q}(\mathfrak {sl}_{2})\)-modules from the equitable point of view. Linear Algebra Appl. 439, 358–400 (2013)
Terwilliger, P.: Billiard Arrays and finite-dimensional irreducible \(u_{q}(\mathfrak {sl}_{2})\)-modules. Linear Algebra Appl. 461, 211–270 (2014)
Terwilliger, P.: The Lusztig automorphism of \(U_{q}(\mathfrak {sl}_{2})\) from the equitable point of view. J. Algebra Appl. 16(12), 1750235, 26 (2017)
Terwilliger, P.: The q-Onsager algebra and the positive part of \(u_{q}(\widehat {\mathfrak {sl}_{2}})\). Linear Algebra Appl. 521, 19–56 (2017)
The Sage Developers. SageMath, the Sage Mathematics Software System (Version 7.0). http://www.sagemath.org (2016)
Worawannotai, C.: Dual polar graphs, the quantum algebra \(u_{q}(\mathfrak {sl}_{2})\), and Leonard systems of dual q-Krawtchouk type. Linear Algebra Appl. 438, 443–497 (2013)
Yang, Y.: Finite-dimensional irreducible \(\square _{q}\)-modules and their Drinfel’d polynomials. Linear Algebra Appl. 537, 160–190 (2018)
Acknowledgments
This paper was written while the author was a graduate student at the University of Wisconsin-Madison. The author would like to thank his advisor, Paul Terwilliger, for offering many valuable ideas and suggestions.
As part of computational evidence, the open software SageMath (see [20]) was used to verify our main results Theorems 8.1, 8.2 and Theorems 9.3–9.6 on low dimensional irreducible \(\square _{q}\)-modules.
Author information
Authors and Affiliations
Corresponding author
Additional information
Presented by: Anne Schilling
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Yang, Y. Some q-exponential Formulas for Finite-Dimensional \(\square _{q}\)-Modules. Algebr Represent Theor 23, 467–482 (2020). https://doi.org/10.1007/s10468-019-09862-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10468-019-09862-y