剛看到有人可以寫文章可以賺3XX P 我也來挑戰看看XDD ============================================================================== The dynamical Casimir effect [1–4] is a very general prediction of quantum field theory: whenever the boundary conditions of a quantum field are quickly varied in time, pairs of quanta are generated off the vacuum state by parametric amplification of zero-point noise. The simplest and most celebrated example of dynamical Casimir effect has been predicted for an optical cavity whose plane-parallel metallic mirrors are made to rapidly oscillate in time along the cavity axis [5–7]. So far, no experimental observation of this effect has been reported, the main reason being the extremely low intensity of the emission for the experimentally accessible values of the mirror oscillation speed [7,8]. Alternative schemes to modulate the effective optical length of a cavity by acting on the refractive index of the cavity material have been proposed and shown to give a sizeable intensity of dynamical Casimir emission for realistic parameters [9–22]. A related but somehow controversial configuration was considered in [23–26]. Experiments in the direction of [18,19] are presently in the course of development [27]. Promising preliminary results using superconducting devices have been recently presented. Since the original proposal by Unruh [30], the advances in the field of the so-called analog models [31] have pointed out the possibility of simulating the physics of a quantum field on a generic curved space-time in tabletop condensed-matter experiments: the propagation of elementary excitations in spatially and temporally inhomogeneous systems can in fact be recast in terms of a relativistic wave equation on an effective curved spacetime. In the simplest case of acoustic waves in a fluid, the space-time metric is fixed by the spatial and temporal profiles of the sound speed and of the flow velocity. Upon quantization of the resulting field theory, an analog dynamical Casimir effect is then expected to appear whenever the boundary conditions on the phonon modes and/or the sound speed of a spatially homogeneous system are rapidly varied in time [32,33]. On the other hand, an analog Hawking radiation is expected to appear in the presence of an acoustic horizon separating an upstream region of sub-sonic flow from a downstream one of supersonic flow [30,34–41]. ______________________________________________________________________________ 為什麼勇士輸啦QAQ 害我賠了400 P --

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