A cuspidal modular form $f$ is said to be **self dual** if the coefficients $a_n$ that appear in its $q$-expansion are real numbers; equivalently, the L-function of the modular form is self dual.

The coefficient field of a newform is either a totally real number field or a CM field, depending on whether the newform is self dual or not.

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- Last edited by Andrew Sutherland on 2018-10-21 15:21:51

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- 2018-10-21 15:21:51 by Andrew Sutherland (Reviewed)