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Title：Quantum Radiation and Vacuum Fluctuations Start Date/Time：2020-01-15 / 12:30 End Date/Time ：2020-01-15 / 13:30

- Speaker：Prof. Bei-Lok Hu (Univ of Maryland)
- Place：P512 of NCTS, 5F, 3rd General Building, Nat'l Tsing Hua Univ.
- Host：Prof. Chong-Sun Chu (NTHU)
- Detailed contents：

Abstract：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

[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).

(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**. 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***not*radiation reaction, but quantum dissipation**fluctuation-dissipation relation**[5] describes the balance between vacuum fluctuations and quantum dissipation in all situations, we show that delicate cancelation 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).

[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).