Lite – that is, $SU(3)$ color gauge theory with two massless quarks – suggests the existence of a second-order phase transition at finite temperature, associated with the restoration of chiral symmetry. Universality arguments suggest that it should exhibit the critical exponents of a 4-component magnet, governed by the $O(4)$ linear $\sigma$ model. There are many precise predictions for the singular behavior of effective meson masses, specific heat, magnitude of the condensate, etc., based on this picture. One can go on to predict analytically the equation of state near the critical point, also allowing for small but nonzero – conceivably, even realistic – quark masses.

It would be a landmark achievement to check some of these predictions, say specifically to measure a critical exponent that can be clearly distinguished from mean field theory. This would provide welcomeconfirmation of some of our deepest prejudices about the nature of chiral symmetry and its restoration; conversely, any deviation from the predictions would force us to rethink some fundamentals.

A few years ago some doubts were raised about the applicability of universality in this context. They have been convincingly addressed, but live on in modified form as valid questions about the scope of universality that 