Quintuple product identity

Short description: Infinite product identity introduced by Watson

In mathematics the Watson quintuple product identity is an infinite product identity introduced by Watson (1929) and rediscovered by (Bailey 1951) and (Gordon 1961). It is analogous to the Jacobi triple product identity, and is the Macdonald identity for a certain non-reduced affine root system. It is related to Euler's pentagonal number theorem.

Statement

[math]\displaystyle{ \prod_{n\ge 1} (1-s^n)(1-s^nt)(1-s^{n-1}t^{-1})(1-s^{2n-1}t^2)(1-s^{2n-1}t^{-2}) = \sum_{n\in \mathbf{Z}}s^{(3n^2+n)/2}(t^{3n}-t^{-3n-1}) }[/math]

References

• Bailey, W. N. (1951), "On the simplification of some identities of the Rogers-Ramanujan type", Proceedings of the London Mathematical Society, Third Series 1: 217–221, doi:10.1112/plms/s3-1.1.217, ISSN 0024-6115 
• Carlitz, L.; Subbarao, M. V. (1972), "A simple proof of the quintuple product identity", Proceedings of the American Mathematical Society 32: 42–44, doi:10.2307/2038301, ISSN 0002-9939 
• Gordon, Basil (1961), "Some identities in combinatorial analysis", The Quarterly Journal of Mathematics, Second Series 12: 285–290, doi:10.1093/qmath/12.1.285, ISSN 0033-5606 
• Watson, G. N. (1929), "Theorems stated by Ramanujan. VII: Theorems on continued fractions.", Journal of the London Mathematical Society 4 (1): 39–48, doi:10.1112/jlms/s1-4.1.39, ISSN 0024-6107 
• Foata, D., & Han, G. N. (2001). The triple, quintuple and septuple product identities revisited. In The Andrews Festschrift (pp. 323–334). Springer, Berlin, Heidelberg.
• Cooper, S. (2006). The quintuple product identity. International Journal of Number Theory, 2(01), 115-161.

Further reading

• Subbarao, M. V., & Vidyasagar, M. (1970). On Watson’s quintuple product identity. Proceedings of the American Mathematical Society, 26(1), 23-27.
• Hirschhorn, M. D. (1988). A generalisation of the quintuple product identity. Journal of the Australian Mathematical Society, 44(1), 42-45.
• Alladi, K. (1996). The quintuple product identity and shifted partition functions. Journal of Computational and Applied Mathematics, 68(1-2), 3-13.
• Farkas, H., & Kra, I. (1999). On the quintuple product identity. Proceedings of the American Mathematical Society, 127(3), 771-778.
• Chen, W. Y., Chu, W., & Gu, N. S. (2005). Finite form of the quintuple product identity. arXiv preprint math/0504277.