In mathematics, the Shimizu L-function, introduced by Hideo Shimizu in 1963, is a Dirichlet series associated to a totally real algebraic number field. Michael Francis Atiyah, H. Donnelly, and I. M. Singer (1983) defined the signature defect of the boundary of a manifold as the eta invariant, the value as s=0 of their eta function, and used this to show that Hirzebruch's signature defect of a cusp of a Hilbert modular surface can be expressed in terms of the value at s=0 or 1 of a Shimizu L-function.
Definition Suppose that K is a totally real algebraic number field, M is a lattice in the field, and V is a subgroup of maximal rank of the group of totally positive units preserving the lattice. The Shimizu L-series is given by
L ( M , V , s ) = ∑ μ ∈ { M − 0 } / V sign N ( μ ) | N ( μ ) | s {\displaystyle L(M,V,s)=\sum _{\mu \in \{M-0\}/V}{\frac {\operatorname {sign} N(\mu )}{|N(\mu )|^{s}}}}
References
Further reading Atiyah, Michael Francis; Donnelly, H.; Singer, I. M. (1982), "Geometry and analysis of Shimizu L-functions", Proceedings of the National Academy of Sciences of the United States of America, 79 (18): 5751, Bibcode:1982PNAS...79.5751A, doi:10.1073/pnas.79.18.5751, ISSN 0027-8424, JSTOR 12685, MR 0674920, PMC 346984, PMID 16593231