Cosmic Neutrinos and New Physics beyond the Electroweak Scale

New physics beyond the electroweak scale may increase weak interaction crosssections beyond the Standard Model predictions. Such cross sections can beexpected within theories that solve the hierarchy problem of known interactionswith a unification scale in the TeV range. We derive constraints on these crosssections from the flux of neutrinos expected from cosmic ray interactions withthe microwave background and the non-observation of horizontal air showers. Wealso discuss how this limit can be improved by upcoming cosmic ray and neutrinoexperiments, and how the energy dependence of the new interactions can beprobed by these experiments