Need for purely laboratory-based axionlike particle searches

The PVLAS signal has led to the proposal of many experiments searching for light bosons coupled to photons. The coupling strength probed by these near-future searches is, however, far from the allowed region, if astrophysical bounds apply. But the environmental conditions for the production of axionlike particles in stars are very different from those present in laboratories. We consider the case in which the coupling and the mass of an axionlike particle depend on environmental conditions such as the temperature and matter density. This can relax astrophysical bounds by several orders of magnitude, just enough to allow for the PVLAS signal. This creates exciting possibilities for a detection in near-future experiments. © 2007 The American Physical Society.