  We compute the vacuum energy of three-dimensional asymptotically flat space
based on a Chern-Simons formulation for the Poincare group. The equivalent
action is nothing but the Einstein-Hilbert term in the bulk plus half of the
Gibbons-Hawking term at the boundary. The derivation is based on the evaluation
of the Noether charges in the vacuum. We obtain that the vacuum energy of this
space has the same value as the one of the asymptotically flat limit of
three-dimensional anti-de Sitter space.

High Energy Physics - Theory;General Relativity and Quantum Cosmology