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