The actual paper by Nick Brown, Alan Sokal, and Harris Friedman (longer, but pretty easy reading): http://arxiv.org/abs/1307.7006 http://arxiv.org/abs/1307.7006

The actual paper by Nick Brown, Alan Sokal, and Harris Friedman (longer, but pretty easy reading): http://arxiv.org/abs/1307.7006 http://arxiv.org/abs/1307.7006 See also: https://en.wikipedia.org/wiki/Critical_positivity_ratio https://en.wikipedia.org/wiki/Critical_positivity_ratio