Tau function may refer to:
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Tau function (integrable systems), in integrable systems
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Ramanujan tau function
The Ramanujan tau function, studied by , is the function
\tau : \mathbb\to\mathbb defined by the following identity:
:\sum_\tau(n)q^n=q\prod_\left(1-q^n\right)^ = q\phi(q)^ = \eta(z)^=\Delta(z),
where q=\exp(2\pi iz) with \mathrm(z)>0, \phi is t ...
, giving the Fourier coefficients of the Ramanujan modular form
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Divisor function
In mathematics, and specifically in number theory, a divisor function is an arithmetic function related to the divisors of an integer. When referred to as ''the'' divisor function, it counts the ''number of divisors of an integer'' (includi ...
, an arithmetic function giving the number of divisors of an integer
{{disambiguation