Note on Energy Shifts of Oscillators in Blackbody Radiation
The energy shift of an oscillator in blackbody radiation is calculated based simply on the total energy of the interacting field-oscillator system as a function of the refractive index. For high temperatures T the energy and free-energy shifts are found to vary as -T^2 and +T^2, respectively, in agreement with the result originally obtained by Ford, Lewis, and O'Connell [Phys. Rev. Lett. 55, 2273 (1985)].
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