twists them into spirals. the altered wave frequency should drop so low that it will become negative (which simply means that the wave spins in the opposite direction).
They would extract energy from the rotation, just like the object escaping from Penrose’s black hole.
But when we spun the foam fast enough for it to Doppler shift the frequency of the sound waves enough to make them negative, the sound became louder.
https://sciencex.com/news/2020-06-energy-black-hole-theory.html
they can create a Bose-Einstein condensate in which sound particles, or phonons, become audible to an accelerated observer in the silent phonon vacuum; the sound is not created by the detector, rather it is hearing what is there just because of the acceleration.
http://www.sci-news.com/physics/unruh-effect-09079.html
If you move the laser beam, so that the point of illumination moves over the Bose-Einstein condensate, that corresponds to the observer moving through the empty space,” Dr. Schmiedmayer said.
“If you guide the laser beam in accelerated motion over the atomic cloud, then you should be able to detect disturbances that are not seen in the stationary case — just like an accelerated observer in a vacuum would perceive a heat bath that is not there for the stationary observer.”
This is the same as "turning the light around" in meditation - to create the internal Tummo heat from the vacuum.
create a two-dimensional cloud of super cold atoms, known as a Bose-Einstein condensate, and study the sound particles, or phonons, that become audible to an accelerated observer. Just as particles can be viewed as “disturbances” in empty space, the Bose-Einstein condensate also experiences disturbances in the form of irregularities (the phonons) that spread out in waves. By focusing a laser beam on the condensate and guiding it in accelerated motion, it is possible that the observer could detect sound disturbances that would not exist for a stationary observer.
Is it the Dynamic Casimir Effect or Unruh Effect or both or neither....?
Vacuum effects in a vibrating cavity: time refraction, dynamical Casimir effect, and effective Unruh acceleration
Two different quantum processes are considered in a perturbed vacuum cavity: time refraction and dynamical Casimir effect. They are shown to be physically equivalent, and are predicted to be unstable, leading to an exponential growth in the number of photons created in the cavity. The concept of an effective Unruh acceleration for these processes is also introduced, in order to make a comparison in terms of radiation efficiency, with the Unruh radiation associated with an accelerated frame in unbounded vacuum.
https://arxiv.org/pdf/0806.0742.pdf
Time refraction, in a cavity or in an unbounded medium, creates pairs of photons propagating in opposite directions. The dynamical Casimir effect in a cavity creates a standing wave mode, which is equivalent to two counter-propagating photons. And, it was recently shown that the Unruh emission by accelerated electrons is also made of pairs of photons [23], with zero momentum in the instantaneous rest frame.
In Section 4, we introduce the effective Unruh acceleration,and compare the efficiency of dynamical Casimir in a vibrating cavity with that of Unruh radiation in unbounded vacuum.
https://www.nature.com/articles/nphys3810
We show with water waves that a sudden change of the effective gravity generates time-reversed waves that refocus at the source. . We generalize this concept for all kinds of waves, introducing a universal framework which explains the effect of any time disruption on wave propagation. We show that sudden changes of the medium properties generate instant wave sources that emerge instantaneously from the entire space at the time disruption.
https://phys.org/news/2020-06-year-old-theory-alien-civilization-exploit.html
In a new paper published today in Nature Physics, the team describe how they built a system which uses small ring of speakers to create a twist in the sound waves analogous to the twist in the light waves proposed by Zel'dovich.
the rotations are doppler shifted...https://sci-hub.se/10.1038/s41567-020-0944-3
"The disk is rotated in the 0 to 30 Hz range, which also corresponds to the linear response range of our motor (that is, the linear increase of rotation speed with driving voltage)."
Amplification of waves from a rotating bodyMarion Cromb 1, Graham M. Gibson1, Ermes Toninelli1, Miles J. Padgett 1 ✉, Ewan M. Wright2 and Daniele Faccio 1,2 ✉In 1971, Zel’dovich predicted that quantum fluctuations and classical waves reflected from a rotating absorbing cylinder will gain energy and be amplified. This concept, which is a key step towards the understanding that black holes may amplify quantum fluctuations, has not been verified experimentally owing to the challenging experimental requirement that the cyl-inder rotation rate must be larger than the incoming wave frequency. Here, we demonstrate experimentally that these condi-tions can be satisfied with acoustic waves. We show that low-frequency acoustic modes with orbital angular momentum are transmitted through an absorbing rotating disk and amplified by up to 30% or more when the disk rotation rate satisfies the Zel’dovich condition. These experiments address an outstanding problem in fundamental physics and have implications for future research into the extraction of energy from rotating systems.
Superradiant scattering of orbital angular momentum beams
Cisco Gooding, Silke Weinfurtner, and William G. Unruh
Phys. Rev. Research 3, 023242 – Published 24 June 2021
, we demonstrate in the context of acoustomechanics that superradiant amplification can also occur with a vortex beam directed parallel to the rotation axis. We propose two different experimental routes: one must either work with rotations high enough that the tangential velocity at the outer edge of the disk exceeds the speed of sound, or use evanescent sound waves.
Moving plates create negative-frequency photonic resonance
We commonly encounter the idea of negative frequencies while analyzing electromagnetic waves and signals, which are often helpful as a mathematical concept to help us keep track of signals that vary over time. We can safely ignore negative frequencies in situations where incoming and outgoing electromagnetic radiation would be equivalent in the event that time was reversed; for example, in the case of a simple ray tracing problem of imaging with lenses. However, we cannot regard negative frequencies as simply a mathematical concept in cases where electromagnetic radiation behaves differently when time is reversed.
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