Great question. 4 is at the high edge of the fat tailed universality class. Most high performing models have alpha approaching 2, or at least below 3. See Fi

Great question. 4 is at the high edge of the fat tailed universality class. Most high performing models have alpha approaching 2, or at least below 3. See Figure 8(a) in the Nature paper, and our upcoming JMLR paper https://arxiv.org/abs/1810.01075 https://arxiv.org/abs/1810.01075