Hawking-Unruh Radiation and Radiation of a Uniformly Accelerated Charge

Hawking-Unruh radiation is a measure of the quantum fluctuations in the radiation of accelerated charges. In the case of uniform acceleration, the existence of Unruh radiation adds confidence that radiation exists at all, and helps clarify aspects of the equivalence between radiation in uniform acceleration and in a uniform gravitational field. 1 Hawking-Unruh Radiation According to Hawking [1], an observer outside a black hole experiences a bath of thermal radiation of temperature T = h̄g 2πck , (1) where g is the local acceleration due to gravity, c is the speed of light, h̄ is Planck’s constant and k is Boltzmann’s constant. In some manner, the background gravitational field interacts with the quantum fluctuations of the electromagnetic field with the result that energy can be transferred to the observer as if he(she) were in an oven filled with black-body radiation. Of course, the effect is strong only if the background field is strong. An extreme example is that if the temperature is equivalent to 1 MeV or more, virtual electron-positron pairs emerge from the vacuum into real particles. As remarked by Unruh [2], this phenomenon can be demonstrated in the laboratory according to the principle of equivalence: an accelerated observer in a gravity-free environment experiences the same physics (locally) as an observer at rest in a gravitational field. Therefore, an accelerated observer (in zero gravity) should find him(her)self in a thermal bath of radiation characterized by temperature