most recent 30 from http://mathoverflow.net 2013-05-24T19:46:49Z http://mathoverflow.net/feeds/user/19003 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/79577/how-do-the-rings-of-level-n-quasi-modular-forms-related-to-the-rings-of-modular/79945#79945 Ram Murty 2011-11-03T16:06:40Z 2011-11-03T16:06:40Z

<p>Dear Simon: Your assertion is right. Let $\Gamma$ be a subgroup of finite index in $SL_2(Z)$. Then any quasi-modular form for $\Gamma$ can be written uniquely as a polynomial in $E_2$ with coefficients which are modular forms for $\Gamma$. This is proved in a paper by Kaneko and Zagier, A generalized Jacobi theta function and quasi-modular forms in The Moduli Space of Curves, Progress in Math., Vol. 129, Birkhauser, 1995, pp. 165-172. Hope this helps.</p> <p>Ram Murty</p>