Ultrahigh energy neutrinos as probe for weak-scale string theories?

We discuss the potential of ultrahigh energy (UHE) neutrinos as probe for new particle physics. After briefly reviewing the proposal that the decay products from UHE neutrinos annihilations on relic neutrinos are the observed UHE primaries, we concentrate on the suggestion that UHE neutrinos can acquire cross-sections approaching hadronic size if the string scale is in the TeV range. We review the calculation of the neutrino-nucleon cross-section σNνKK due to the exchange of Kaluza-Klein (KK) excitations of the graviton in a field theoretical framework and discuss the issue of unitarity. Assuming Regge behavior of the neutrino-nucleon interaction mediated by KK gravitons, we find that the effects of large extra dimensions are barely observable