'TeV Gamma-ray Crisis' and an Anisotropic Space Model
  To solve the `TeV gamma crisis', we examine a model whose one spatial direction is discretized at a high energy scale. Assuming the standard extra-galactic IR photon distribution, we evaluate the mean free-path of a energetic photon which acquires an effective mass in the model. For a wide range of the value of the lattice energy scale between a few TeV and around $10^{10}$ GeV, the mean free-path of a TeV energy photon can be enlarged enough to solve the `crisis'. Taking into account the effects of the universe expansion, we find bounds of the lattice constant. 
Gi-Chol Cho, Jun-ichi Kamoshita, Mariko Matsunaga, Akio Sugamoto and   Isamu Watanabe