Quantum inequalities in curved two-dimensional spacetimes

In quantum field theory there exist states in which the energy density is negative. It is important that these negative energy densities satisfy constraints, such as quantum inequalities, to minimize possible violations of causality, the second law of thermodynamics, and cosmic censorship. In this paper I show that conformally invariant scalar and Dirac fields satisfy quantum inequalities in two-dimensional spacetimes with a conformal factor that depends on x only or on t only. These inequalities are then applied to two-dimensional black hole and cosmological spacetimes. It is shown that for static observers the bound on the negative energies diverges to minus infinity as the event horizon or initial singularity is approached. Thus, neglecting back reaction, the negative energies measured by static observers become unconstrained near the horizon or initial singularity. The results of this paper also support the hypothesis that the quantum interest conjecture applies only to deviations from the vacuum polarization energy, not to the total energy.