Quantum coherence effects and the second law of thermodynamics

Abstract Negative energy densities and fluxes due to quantum coherence effects in quantum field theories are discussed. Such negative energy fluxes seeming­ly lead to a breakdown of the second law of thermodynamics. It is argued that such a breakdown will not in fact occur if a negative energy flux F is constrained by an inequality of the form │F│≲ T-2 where T is a character­istic time over which the negative energy flux occurs. Particular models in which negative energy fluxes occur are examined, and it is found that such an inequality is indeed satisfied. Quantum violations of the dominant energy condition, which requires that the local energy density be greater than or equal to the magnitude of the pressure are also discussed briefly.