Please note special time and location.We consider the Hubbard model on the honeycomb lattice as a model for graphene and ask the question of possible lattice distortions. The answer is that in the thermodynamic limit only periodic, reflection-symmetric distortions are allowed and these have at most six atoms per unit cell as compared to two atoms for the undistorted lattice. We sketch the proof, which is based on the technique of reflection positivity. The talk is based on a joint work with E. Lieb.