Electromagnetic fluctuation

At the other limit, when r > 1, the time of travel of the signal across the gap Z and back is longer than the lifetime of the electromagnetic fluctuation. The damping term goes to zero almost exponentially ... 

How important to forces are the electromagnetic fluctuations that occur in the different frequency regions ... 

Physically, rn is the ratio of the time for an electromagnetic signal to travel and return across the gap of medium m and thickness / divided by the characteristic time 1 / of the particular electromagnetic fluctuation. 

Temperature comes into computation two ways. First, there is the way temperature affects electromagnetic fluctuations, how variable T is handled in formulae. Second, changes in temperature actually affect spectral response. By measuring response at different temperatures, we can determine both these consequences of varied temperature. Figure L2.32 shows the response of AI2O3 at different temperatures.17 The nonretarded Hamaker coefficient for AI2O3 across vacuum goes from 145 zj at 300 K to 152 zj at 800 K and then down to 125 zj at T = 1925 K.14... 

As described in earlier sections, any two material bodies will interact across an intermediate substance or space. This interaction is rooted in the electromagnetic fluctuations— spontaneous, transient electric and magnetic fields—that occur in material bodies as well as in vacuum cavities. The frequency spectrum of these fluctuations is uniquely related to the electromagnetic absorption spectrum, the natural resonance frequencies of the particular material. In principle, electrodynamic forces can be calculated from absorption spectra. 

Y.S. Barash, V.L. Ginzburg, Electromagnetic fluctuations in matter and molecular (Van-der-Waals) forces between them. Sov. Phys. Usp. 18 (1975) 305. 

As discussed in Paresegian s recent book, the modern view of dispersion interactions has its roots in the the Casimir effect. " Rather than charge fluctuations, the phenomenon can be viewed in terms of zero-point electromagnetic-field fluctuations in the vacuum as allowed by the Heisenberg uncertainty principle (AEAt>b/ln). Atoms and molecules can absorb some of these frequencies, namely those frequencies that are resonant with transitions between the quantum mechanical energy levels of the system as determined by its electronic structure. This absorption of the electromagnetic fluctuations gives rise to attractive forces between two bodies. 

As a model consider two solids, as shown in Fig. 2-1. The solids are separated from each other by a gap of width Zq. The internal electromagnetic fluctuation fields in solids set up an electromagnetic field F3, in the gap. The resultant electromagnetic field strengths 3 and 7/3 of the gap are used to determine the Maxwell electromagnetic stress tensor T. The force component parallel to the Z axis is... 

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