Gamma-ray spectrum of RX J1713.7-3946 in the Fermi era and future detection of neutrinos

The recently launched satellite, Fermi Gamma-ray Space Telescope, is expected to find out if cosmic-ray (CR) protons are generated from supernova remnants (SNRs), especially RX J1713.7-3946, by observing the GeV-to-TeV gamma-rays. The GeV emission is thought to be bright if the TeV emission is hadronic, i.e., of proton origin, while dim if leptonic. We reexamine the above view using a simple theoretical model of nonlinear acceleration of particles to calculate the gamma-ray spectrum of Galactic young SNRs. If the nonlinear effects of CR acceleration are considered, it may be impossible to distinguish the evidence of proton acceleration from leptonic in the gamma-ray spectrum of Galactic young SNRs like RX J1713.7-3946. On the other hand, future km^3-class neutrino observations will likely find a clear evidence of the proton acceleration there.