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I'm studying linear sigma model. I understand it's a useful effective model for more than one theory with the same symmetries but I don't understand why it is desirable for sigma to be light. I read this in more than one source without anything to justify, just "so sigma is smaller, which is great for low energy physics! let us all celebrate small sigma!". So I celebrate because I'm a polite person but I don't understand why.

Diego
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    this is a very theoretical question . If you do not get a satisfying response here try https://www.physicsoverflow.org/ – anna v Mar 30 '18 at 03:59
  • Isn't this circular? If the σ is light, which in QCD chiral symmetry breaking appears like an empirical fact, then it is a negligent player in low energy physics; if its mass is infinite, then the model is promoted to the nonlinear/chiral variety, also used for several realistic purposes, with the σ out of the way, also celebrated by some. If the celebrants won't tell you what they are celebrating, why not simply shrug? – Cosmas Zachos Mar 30 '18 at 10:36
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    If you read my answer to this question (https://physics.stackexchange.com/questions/292913/why-is-the-density-of-the-fermi-gas-in-a-neutron-star-not-changing-the-potential) along with the links therein, you will find your answer. – Lewis Miller Mar 31 '18 at 02:13

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