I Applications for negative radiation pressure?

[JD23]

If the beam splitter reflects half of the incident light then both perspectives should lose half their light, unless beam splitters only work one way.

Exactly - that's my point: if in both perspectives symmetric ring laser would produce the same amount of photons (and there are no other sources), the fact that they are the same system requires that "photons go straight through beamsplitter" - cannot turn up/down.
In electric/hydro analogs, going down the split is directly prevented by negative pressure - suggesting analogous explanation for beam-splitter ... it would be great to perform such a test, but it needs some photonic lab (I don't have access to) ...

Also, you keep talking about CPT symmetry, but it isn't entirely clear which reversals/inversions you are actually doing.

I am talking about CPT because T alone is not conserved.
For simplicity I use T alone in diagrams, but formally imagine there is also CP.

 

[Vanadium 50]

I am talking about CPT because T alone is not conserved.

It is in the electromagnetic interaction.

 

[JD23]

I wanted to add it ... but to get unidirectional photon trajectories there is used Faraday effect, which violates T.

It rotates linear polarization by a fixed angle, due to difference of propagation speeds of two circular polarizations - which are switched in T symmetry.

 

[Vanadium 50]

Faraday effect, which violates T.

No it does not. (A common error is to ignore the effect of T on the magnetic field)

 

[PeterDonis]

here if running backward you get its analogue for 1D topological defects

I don't know where you're getting this from. The CPT inverse of pair creation is pair annihilation: an electron and positron annihilate and a pair of photons comes out.

 

[PeterDonis]

@JD23 where are all these diagrams in your posts coming from?

 

[PeterDonis]

I would gladly discuss and generally am searching for collaboration in these topics, especially access to ring laser to test

PF is not for discussing or pursuing personal research.

 

[Drakkith]

Exactly - that's my point: if in both perspectives symmetric ring laser would produce the same amount of photons (and there are no other sources), the fact that they are the same system requires that "photons go straight through beamsplitter" - cannot turn up/down.

Obviously such a setup would indeed split the laser beam, so I don't know what to tell you.

 

[JD23]

No it does not. (A common error is to ignore the effect of T on the magnetic field)

I have seen such a statement in a few articles, e.g. "Faraday effect that breaks the time-reversal symmetry" in https://www.nature.com/articles/s41566-018-0127-2 so I assumed it is true ... indeed with some internal conflict I should explore as electromagnetism alone is T symmetric and there is nearly no way to get out of EM here (hyperfine interactions with nucleus?)
Thanks for clarification, I will have to think about it.

Obviously such a setup would indeed split the laser beam, so I don't know what to tell you.

In electronic and hydrodynamic analogs the statistics of split is changed by negative pressure - as equations are nearly the same, why it cannot be still true for split of light analog by negative radiation pressure?
CPT theorem suggests it should work, it would be great to test it experimentally ...

Regarding the diagrams, some are linked articles, some I have made for potential computational applications of negative radiation pressure this thread is about.

 

[Drakkith]

In electronic and hydrodynamic analogs the statistics of split is changed by negative pressure - as equations are nearly the same, why it cannot be still true for split of light analog by negative radiation pressure?
CPT theorem suggests it should work, it would be great to test it experimentally ...

As has been said already, light doesn't interact with itself hardly at all. As far as the light is concerned, there is no radiation pressure at all on itself. This is unlike physical flows like water or electric current where the flow is highly interacting with itself.

 

[JD23]

But thinking about EM waves not individual photons, the equations are practically the same as for superfluids - what would prevent recreation of such circulation with active pump?
Negative radiation pressure and optical pulling exist both theoretically and experimentally - claiming impossibility requires a different argument.

So what about intermediate picture - microwaves in waveguides?
Would such EM wave be mathematically very different from superfluid?
Searching "microwave Farday effect" there are a few articles - so enforcing unidirectional circulation might be doable (?)
Would it be possible to build circulation with active pump for wicrowaves?
If so, could split behavior be controlled also by negative (radiation) pressure like in hydrodynamical analog?
If so, what would change for optical photons - of shorter wavelengths?

Ps. Some waveguides from https://www.testandmeasurementtips.com/basics-waveguides-microwaves-ovens/

 

[Drakkith]

But thinking about EM waves not individual photons

Irrelevant. Light does not interact with itself enough either way you look at it.

the equations are practically the same as for superfluids

Again, irrelevant.

So what about intermediate picture - microwaves in waveguides?
Would such EM wave be mathematically very different from superfluid?

That depends entirely on what you mean by 'very different'. And on how deep you look into things.

If so, could split behavior be controlled also by negative (radiation) pressure like in hydrodynamical analog?

No. Radiation pressure acts on matter, not on light.

 

[JD23]

Pressure is effective description of hidden dynamics, e.g. <E x H>/c averaged vector for radiation - so how does this dynamics differ between superfluid and electromagnetism to prevent recreation of circulation with pump?
Please point this difference in equations governing them.

Here are lots of articles about this analogy:
https://scholar.google.pl/scholar?q=electrodynamics+hydrodynamics+analogy

ps. Related: video of Casimir effect for waves in water - this time pulling taken in the opposite direction of this analogy:

 

[Drakkith]

Pressure is effective description of hidden dynamics, e.g. <E x H>/c averaged vector for radiation - so how this dynamics differs between superfluid and electromagnetism to prevent recreation of circulation with pump?

Enough with the analogies. Either talk specifically about your optical setup, using optical terminology, or I will lock this thread. Things like 'recreation of circulation with pump' add an unnecessary step that we have to work through to get to what you're actually wanting to know.

 

[JD23]

I have shown the setting in #10 and #19 here, and we have discussed that e.g. CPT theorem suggests such setting should work similarly in all: electronic, hydrodynamic ... so why not for e.g. EM microwaves, photons?
I agree that negative radiation pressure feels non-intuitive, but it doesn't make it nonexistant, for what I still haven't seen meritorious counterargument.

Ok, so let us skip this potential computation application direction, and leave this thread for different aspects of "Negative radiation pressure" as in the title (please don't lock it).

 

[Drakkith]

I agree that negative radiation pressure feels non-intuitive, but it doesn't make it nonexistant, for what I still haven't seen meritorious counterargument.

I don't think anyone here is claiming that negative radiation pressure doesn't exist (see here). We're saying that your setup probably doesn't do what you think it does.

I have shown the setting in #10 and #19 here, and we have discussed that e.g. CPT theorem suggests such setting should work similarly in all settings: electronic, hydrodynamic ... so why not for e.g. EM microwaves, photons?

Again, I don't see any need to invoke CPT symmetry. If you provide an optical setup, it should immediately be clear what it does. Your setups provided so far do nothing exceptional. You have a ring laser and a beam splitter that splits the beam. That's it. It's a very simple setup.

 

[JD23]

Beside EM-hydro analogy, the only argument I have is that looking from CPT symmetry perspective, symmetric ring laser should produce the same amount of photons in the opposite direction.
If so, just counting the photons, without other sources, photons would have to go "straight through the beamsplitter" (analogously to straight through the split in electric, hydro settings due to negative radiation pressure).
In both perspectives this is practically the same setting, hence should work the same.

I understand that beamsplitters are made to have fixed proportions e.g. 50:50 (for e.g. laser beam carrying positive radiation pressure).
But was it tested in the presence of negative radiation pressure? (a very subtle condition, opposite to positive)
If it wasn't and there are arguments it might be affected, maybe it is worth experimental verification.

Probably it would not be affected as nearly everybody expects, but it would bring questions:
- what is wrong with the above CPT symmetry-based argument?
- what is the mathematical difference between EM and superfluid allowing circuit with pump for exactly one of them?

 

[Drakkith]

Beside EM-hydro analogy, the only argument I have is that looking from CPT symmetry perspective, symmetric ring laser should produce the same amount of photons in the opposite direction.

By itself it might, but you have other things in the system.

In both perspectives this is practically the same setting, hence should work the same.

But that's the thing. It's not the same setting. The beam splitter is at a different angle relative to the oncoming beam of light in the second setup.

I understand that beamsplitters are made to have fixed proportions e.g. 50:50 (for e.g. laser beam carrying positive radiation pressure).
But was it tested in the presence of negative radiation pressure?

There is no negative radiation pressure in any of your setups and negative pressure appears to only be possible in certain types of materials.

- what is wrong with the above CPT symmetry-based argument?

I think you've forgotten the P in CPT. A parity transform of the system would appear to solve the issues I've brought up.

- what is the mathematical difference between EM and superfluid allowing circuit with pump for exactly one of them?

A great many things. Light can't stop moving, for example. It doesn't interact with itself hardly at all. It's uncharged. It's massless. It's fundamentally different from any superfluid.

 

[JD23]

By itself it might, but you have other things in the system.

But that's the thing. It's not the same setting. The beam splitter is at a different angle relative to the oncoming beam of light in the second setup.

Not having other photon sources, to make it more symmetric we can rotate the beamplitter 90 degrees toward us (up/down -> to/from us) - this way in both perspectives (with/without CPT) it would be practically the same situation.
In CPT symmetric physics, preparing situation being the same in both perspectives like circulation with pump - shouldn't they differ by just direction of circulation?

A great many things. Light can't stop moving, for example. It doesn't interact with itself hardly at all. It's uncharged. It's massless. It's fundamentally different from any superfluid.

Indeed for optical photons it is less intuitive, so I have suggested intermediate picture: microwaves in waveguides - which is more "pure EM" governed by nearly the same equations as superfluid - would such reduction of flow down the split by negative radiation pressure be possible for microwave setting?

If so, maybe such more powerful quantum computer (attacking postBQP by physical constraints) could be made on microwaves?
... or maybe superfluid quantum computer with mechanical qubits (e.g. https://phys.org/news/2023-06-mechanical-qubits.html ) of fluid vibrations, for which construction of such two-way quantum computer would be just a matter of connecting it into a circuit with pump.

 

[Drakkith]

Not having other photon sources, to make it more symmetric we can rotate the beamplitter 90 degrees toward us (up/down -> to/from us) - this way in both perspectives (with/without CPT) it would be practically the same situation.

The only beam splitters I've seen are cube-like with the internal diagonal joining the two pieces as the reflecting surface. There is no way to orient this such that it will reflect the two beams the same way.

Indeed for optical photons it is less intuitive, so I have suggested intermediate picture: microwaves in waveguides - which is more "pure EM" governed by nearly the same equations as superfluid - would such reduction of flow down the split by negative radiation pressure be possible for microwave setting?

No, not as far as I know.

At this point I feel we're just going in circles. Light doesn't follow the mathematical laws of hydrodynamics or electrical circuits, so continually asking, "why won't this work like the analogy does" is getting us nowhere.

If you can find a legitimate setup that shows negative radiation pressure then we can discuss it. But trying to develop your own based on analogies and a questionable argument using CPT symmetry is not going to fly here at PF. Thread locked.