
Coherent virtual absorption of elastodynamic waves - bookofjoe
https://advances.sciencemag.org/content/5/8/eaaw3255
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olliej
I’ve read this multiple times and still don’t understand what they’re doing,
or why it is useful.

It states energy can be released on demand, yet the rest of the paper seems to
imply the energy is released the moment the input signal stops.

That ignores other problems I have in understanding: if it stores perfectly
(losing no energy) then the longer you run the input the more energy is
necessarily going to be released. What happens if I run the inputs for a
decade? I cannot imagine that I magically release ten years of energy
immediately, so I’m clearly missing something. I just can’t work out what.

Any chance authors are hanging out in HN?

~~~
semi-extrinsic
Think of sound waves reflecting off a wall. As soon as the first wavefront
hits, it is sent back.

With this thing, you would send soundwaves at the wall, and it would store the
energy in the sound for a short period before sending it back.

It looks like it compresses the time interval for energy release as well. So
you'd play a little Mozart at normal volume at the wall, and then after (say)
1 second it would send a cacaphony of noise back at you.

It also looks like they can control what direction the wall sends sound back
in. And it looks like the period in which they can store energy is very
limited.

As for "can control when the energy is released" \- they control it by
controlling when the incoming signal stops. They have to do a lot of control
on the incoming signals for this to work.

They mention future work to build such a device with photons. I'd hazard a
guess that then you could use this to build a fancy phased array radar
analogue.

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pontifier
I was at the beach yesterday thinking about this same sort of thing. Because
of the way waves add, this sort of thing might be useful for creating
constructive interference at a specific spot from impinging randomness. I'd
love to see a passive wave spike generator floating near a beach.

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whatshisface
Can someone explain to me how this is different from other resonant cavity
mechanisms like kitchen microwaves?

