Large zero point density fluctuations in fluids

Abstract

Zero point density fluctuations in a liquid and their potential observation by light scattering are discussed. It is suggested that there are two distinct effects of interest. One gives an average number of scattered photons, and depends upon an inverse power of the photon wavelength. The second effect arises in the scattering of finite size photon wave packets and depends upon an inverse power of the spatial size of the wave packet, as well as upon the shape of the wave packet. This effect appears as large fluctuations in the number of scattered photons, and is analogous to the vacuum fluctuations of space-time averages of the energy density in quantum field theory. It is an illustration that quantum fluctuations become larger when probed on smaller length and time scales.

Space and time averaged quantum stress tensor fluctuations

“…Phenomena associated with a full theory of quantum gravity may be explored through extensions to the semiclassical theory of gravity. Many such phenomena have been proposed over the years, including geodesic focusing [9,21,22], impacts on power spectra [10,11], increased barrier penetration rates of charged particles [23], alternative false vacuum decay pathways for self-coupled scalar fields [24], velocity fluctuations of Rydberg atoms [26], and large variations in scattered photons in low-temperature light scattering experiments [27].…”

“…These operators are of interest because they are related to physical quantities that may be probed experimentally. For example, the p = 3 case can be used to infer the behavior of electromagnetic energy density fluctuations [16], electromagnetic momentum flux fluctuations [23], and even fluid density fluctuations [27].…”

“…These findings suggest the probabilities of measuring large vacuum fluctuations of stress tensor operators may not be as negligible as one might have expected, spurring work into possible physical effects such as focusing of geodesics induced by spacetime curvature fluctuations [21,22] and enhanced barrier penetration rates of charge particles due to radiation pressure fluctuations [23]. Related phenomena in other systems that emerge from similar quadratic operators are also expected to occur: false vacuum decay of a self-interacting scalar field may be dominated by a pathway [24] different from the usual instanton approximation [25], Rydberg atoms may exhibit velocity fluctuations in response to a sequence of short laser pulses [26], and low-temperature light scattering experiments may find large variations in the number of scattered photons [27].…”

Space and Time Averaged Quantum Stress Tensor Fluctuations

“…Large fluctuations of stress-tensor-like operators have a number of potentially observable and interesting effects, including fluctuating gravity waves [19], increased barrier penetration probabilities for charged particles [20], alternative processes for false vacuum decay [21], and greater variance of scattered photons in a low-temperature light scattering experiments [23].…”

“…Large fluctuations around the zero point density of a fluid as an analog model for quantum stress tensor fluctuations is studied in Ref. [23]. These density fluctuations may potentially be detectable in low-temperature light scattering experiments [24] by observing fluctuations in the number of scattered photons.…”