Lower Bounds For The First Eigenvalue Of The Laplacian With Dirichlet   Boundary Conditions In A Hyperbolic Space Of A Negative Constant Curvature
  In this paper we consider a domain in a space of negative constant sectional curvature. Such assumption about the sectional curvature let us develop a new technique and improve existing lower bounds of eigenvalues from Dirichlet eigenvalue problem, obtained by Alessandro Savo in 2009. 
Sergei Artamoshin
math.DG