1307.4969 (Robert Lohmayer et al.)

Phase structure of two-dimensional QED at zero temperature with
flavor-dependent chemical potentials and the role of multidimensional theta
functions    [PDF]

Robert Lohmayer, Rajamani Narayanan

We consider QED on a two-dimensional Euclidean torus with $f$ flavors of massless fermions and flavor-dependent chemical potentials. The dependence of the partition function on the chemical potentials is reduced to a $(2f-2)$-dimensional theta function. At zero temperature, the system can exist in an infinite number of phases characterized by certain values of traceless number densities and separated by first-order phase transitions. Furthermore, there exist many points in the $(f-1)$-dimensional space of traceless chemical potentials where two or three phases can coexist for $f=3$ and two, three, four or six phases can coexist for $f=4$. We conjecture that the maximal number of coexisting phases grows exponentially with increasing $f$.

View original: http://arxiv.org/abs/1307.4969