Neutrino cascades: The byproducts of propagation of ultra-high-energy neutrinos

Ultra high energy cosmic neutrinos may not propagate unattenuated in space over cosmological distances because they can interact with the relic cosmological neutrino background. This process initiates neutrino cascades which provide a possible signature of the background neutrinos and could give rise to the observed cosmic ray flux beyond the GZK cutoff. We discuss high energy neutrino propagation in space with special focus on generation and development of neutrino cascades. Analytical estimates as well as numerical investigations are presented to show how this byproduct of high energy neutrino propagation can cause various interesting phenomena in the Universe.