Boundary conditions in the Unruh problem

According to Unruh, a detector moving with constant proper acceleration in empty Minkowski spacetime reveals universal—not depending on the inner structure of the detector—thermal response. We have analyzed the Unruh problem using both conventional and algebraic approaches to quantum field theory. It is shown that the Unruh quantization procedure implies setting a boundary condition for the quantum field operator which changes the topological properties and symmetry group of the spacetime and leads to a field theory in two disconnected left and right Rindler spacetimes instead of Minkowski spacetime. Thus we conclude that, in spite of the work over the last 25 years, there still remain serious gaps in grounding of the Unruh effect, and as of now there is no compelling evidence for the universal behavior attributed to all uniformly accelerated detectors.