The quantum criticality conundrum

It is well known theoretically that materials possessing distinct adjoining quantum phases at zero temperature can display behaviour that is universal and insensitive to microscopic details. This is the phenomenon of quantum criticality. Universality is, however, a central feature of the phases them selves and one essential to identifying them. Recent developments in the st udy of correlated-electron materials suggest that quantum criticality is pr esent in these materials and has been masking the true nature of their phas es. This raises troubling questions about the relation between theory and e xperiment in physics, as well as in science generally.