Lorentz invariance and the cosmological constant

Non-trivial solutions in string held theory may lead to the spontaneous breaking of Lorentz invariance and to new tenser-matter interactions. It is argued that requiring the contribution of the vacuum expectation values of Lorentz censors to account for the vacuum energy up to the level Omega(0)(Lambda) = 0.5, implies the new interactions range is lambda similar to 10(-4) m. These conjectured violations of Lorentz symmetry are consistent with the most stringent experimental limits.