### Abstract

A unified treatment is given of low-weight modular forms on Γ_{0}(N), N = 2,3,4, that have Eisenstein series representations. For each N, certain weight-1 forms are shown to satisfy a coupled system of nonlinear differential equations, which yields a single nonlinear third-order equation, called a generalized Chazy equation. As byproducts, a table of divisor function and theta identities is generated by means of q-expansions, and a transformation law under Γ_{0}(4) for the second complete elliptic integral is derived. More generally, it is shown how Picard-Fuchs equations of triangle subgroups of PSL(2, R), which are hypergeometric equations, yield systems of nonlinear equations for weight-1 forms, and generalized Chazy equations. Each triangle group commensurable with Γ(1) is treated.

Original language | English (US) |
---|---|

Pages (from-to) | 1-42 |

Number of pages | 42 |

Journal | Manuscripta Mathematica |

Volume | 134 |

Issue number | 1 |

DOIs | |

State | Published - Jan 2011 |

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### ASJC Scopus subject areas

- Mathematics(all)

### Cite this

**Nonlinear differential equations satisfied by certain classical modular forms.** / Maier, Robert S.

Research output: Contribution to journal › Article

*Manuscripta Mathematica*, vol. 134, no. 1, pp. 1-42. https://doi.org/10.1007/s00229-010-0378-9

}

TY - JOUR

T1 - Nonlinear differential equations satisfied by certain classical modular forms

AU - Maier, Robert S

PY - 2011/1

Y1 - 2011/1

N2 - A unified treatment is given of low-weight modular forms on Γ0(N), N = 2,3,4, that have Eisenstein series representations. For each N, certain weight-1 forms are shown to satisfy a coupled system of nonlinear differential equations, which yields a single nonlinear third-order equation, called a generalized Chazy equation. As byproducts, a table of divisor function and theta identities is generated by means of q-expansions, and a transformation law under Γ0(4) for the second complete elliptic integral is derived. More generally, it is shown how Picard-Fuchs equations of triangle subgroups of PSL(2, R), which are hypergeometric equations, yield systems of nonlinear equations for weight-1 forms, and generalized Chazy equations. Each triangle group commensurable with Γ(1) is treated.

AB - A unified treatment is given of low-weight modular forms on Γ0(N), N = 2,3,4, that have Eisenstein series representations. For each N, certain weight-1 forms are shown to satisfy a coupled system of nonlinear differential equations, which yields a single nonlinear third-order equation, called a generalized Chazy equation. As byproducts, a table of divisor function and theta identities is generated by means of q-expansions, and a transformation law under Γ0(4) for the second complete elliptic integral is derived. More generally, it is shown how Picard-Fuchs equations of triangle subgroups of PSL(2, R), which are hypergeometric equations, yield systems of nonlinear equations for weight-1 forms, and generalized Chazy equations. Each triangle group commensurable with Γ(1) is treated.

UR - http://www.scopus.com/inward/record.url?scp=78649944860&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78649944860&partnerID=8YFLogxK

U2 - 10.1007/s00229-010-0378-9

DO - 10.1007/s00229-010-0378-9

M3 - Article

AN - SCOPUS:78649944860

VL - 134

SP - 1

EP - 42

JO - Manuscripta Mathematica

JF - Manuscripta Mathematica

SN - 0025-2611

IS - 1

ER -