Constraints on the variability of quark masses from nuclear binding

TL;DR

This paper refines constraints on light quark masses based on nuclear binding, showing that significant deviations could prevent the formation of stable heavy nuclei and atoms, thus impacting the conditions for life.

Contribution

It provides tighter anthropic constraints on light quark masses and the Higgs vacuum expectation value based on nuclear stability considerations.

Findings

Heavy nuclei become unstable if m_u + m_d exceeds physical values by 64%.

Constraints on quark masses imply a narrow anthropic window for the Higgs VEV.

Nuclear binding considerations limit the variation of fundamental constants.

Abstract

Based on recent work on nuclear binding, we update and extend the anthropic constraints on the light quark masses, with results that are more tightly constrained than previously obtained. We find that heavy nuclei would fall apart (because the attractive nuclear central potential becomes too weak) if the sum of the light quark masses m_u+m_d would exceed their physical values by 64% (at 95% confidence level). We summarize the anthropic constraints that follow from requiring the existence both of heavy atoms and of hydrogen. With the additional assumption that the quark Yukawa couplings do not vary, these constraints provide a remarkably tight anthropic window for the Higgs vacuum expectation value: 0.39 < v/v_physical < 1.64.