2020-01-10 11:00 P7F
Quantum Radiation and Vacuum Fluctuations*
Bei-Lok Hu
From the 70s recurring confusion appears in two aspects of quantum radiation
from/in an atom. They are:
(A) The claim that one can explain phenomena associated with vacuum
fluctuations by radiation reaction and vice versa [1]. (B) Unruh
effect [2] says that a uniformly accelerated atom will get hot, but is
there emitted radiation from it in the nature of Lamor? (None proven
in 1+1 dimension [3]). Issue B is particularly relevant to
experimental tests of Unruh/Hawking radiation. In this talk we shall
focus on Aspect A because it brings out several important issues at
the interfaces of quantum, stochastic, semiclassical and classical.
Misconception in Issue A could generate more confusion because it is
often used by “classicists” as an example that one can always find a
classical explanation for any quantum phenomena, which is wrong. We
reiterate what was said in [4] before: What holds the ‘duality
relation’ with vacuum fluctuations is not radiation reaction, but
quantum dissipation. These two entities belong to two different
worlds: vacuum fluctuations are quantum in nature but radiation
reaction already exists at the classical level. A charge, be it moving
or stationary, feels the effect of vacuum fluctuations, as would any
physical object in all circumstances, but radiation reaction is absent
for a uniformly accelerated (UA) charge. We use the simplest example
of a stationary atom to illustrate the relation between vacuum
fluctuations, quantum dissipation and quantum radiation. While the
fluctuation-dissipation relation [5] describes the balance between
vacuum fluctuations and quantum dissipation in all situations, we show
that delicate cancellation of the interference between emitted
radiation from the atom and the local fluctuations in the free field
at the observation point is what accounts for the absence of quantum
radiation. Continued work for a UA atom in 3+1 D will resolve the
mystery of Issue B: Whether there is emitted quantum radiation in
Unruh effect.
*Based on J. T. Hsiang and B. L. Hu, Physics 1, 430–444 (2019) arXiv:1910.11527
[1] Milonni, P.W. The Quantum Vacuum: An Introduction to Quantum Electrodynamics; Academic Press: Cambridge, MA, 1993. Different ways of looking at the electromagnetic vacuum. Phys. Scr. T12, 102 (1988).
[2] Unruh, W.G. Notes on black-hole evaporation. Phys. Rev. D14, 870 (1976).
[3] Raine, D.J.; Sciama, D.W.; Grove, P., Does a uniformly accelerated quantum oscillator radiate? Proc. R. Soc. Lond. A435, 205 (1991). Hu, B.L.; Raval, A. Is there emitted radiation in Unruh effect? arXiv:quant-ph/0012134. Lin, S.-Y.; Hu, B.L. Accelerated detector–quantum field correlations: From vacuum fluctuations to radiation flux. Phys. Rev. D 73, 124018 (2006)
[4] Johnson, P.R.; Hu, B.L., Phys. Rev. D65, 065015 (2002). Johnson, P.R.; Hu, B.L., Unruh effect in a uniformly accelerated charge: From quantum fluctuations to classical radiation. Found. Phys. 35, 1117 (2005)
[5] Ford, G.W. The fluctuation-dissipation theorem. Contemp. Phys. 58, 244 (2017).
Hsiang, J.-T.; Hu, B.L.; Lin, S.-Y. Fluctuation-dissipation and correlation-propagation relations from the nonequilibrium dynamics of detector-quantum field systems. Phys. Rev. D 100, 025019 (2019). Hsiang, J.-T.; Hu, B.L.; Lin, S.-Y.; Yamamoto, K. Fluctuation-dissipation and correlation-propagation relations in (1+3)D moving detector-quantum field systems. Phys. Lett. B 795, 694 (2019).
Presentation Slides