title: Fricke involution
text: # Fricke involution
  
  In mathematics, a Fricke involution is the involution of the modular curve $X_0(N)$ given by τ → –1/Nτ. It is named after Robert Fricke. The Fricke involution also acts on other objects associated with the modular curve, such as spaces of modular forms and the Jacobian $J_0(N)$ of the modular curve.
  
  