We discuss a phenomenon important to the development of the early Universe which may be experimentally testable in heavy-ion collisions. An arbitrary induced $\theta$ vacuum state should be created in heavy-ion collisions, similar to the creation of the disoriented chiral condensate. It should be a large domain with a wrong ${\theta }^{\mathrm{ind}}\ne 0$ orientation which will mimic the physics of the early Universe when it is believed that the fundamental parameter ${\theta }^{\mathrm{fund}}\ne 0$. We test this idea numerically in a simple model where we study the evolution of the phases of the chiral condensates in QCD with two quark flavors with nonzero ${\theta }^{\mathrm{ind}}$ parameter. We see the formation of a nonzero ${\theta }^{\mathrm{ind}}$ vacuum on a time scale of ${10}^{-23\mathrm{}}\mathrm{s}$.

• Received 18 October 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.4814