The accelerating expansion of the Universe points to a small positive vacuumenergy density and negative vacuum pressure. A strong candidate is thecosmological constant in Einstein's equations of General Relativity. The vacuumdark energy density extracted from astrophysics is 10^56 times smaller than thevalue expected from the Higgs potential in Standard Model particle physics. Thedark energy scale is however close to the range of possible values expected forthe light neutrino mass. We investigate this physics in a simple toy modelwhere the chirality of the neutrino is treated by analogy as an Ising-like"spin" degree of freedom.
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