T/CPT symmetric analog of black hole in Kruskal–Szekeres coordinates is white hole, which only allows photons to cross horizon outside, hence pushing objects around with EM - act with positive radiation pressure p=<ExH>/c vectors outside, absorption equation increasing the number of excited atoms (N2) outside.
If so, shouldn't black hole symmetrically act with negative radiation pressure - pull objects around with EM by p=<ExH>/c radiation pressure vectors pointing inside, act with stimulated emission equation decreasing the number of excited atoms (N2) outside?

Such looking necessary effect of black hole could be slightly easier to observe than Hawking radiation, maybe even look below the horizon - would need e.g. telescope with excited sensor, monitoring its population - testing if it doesn't deexcite faster than usual by stimulated emission e.g. from black hole.

Edited September 15Sep 15 by Duda Jarek

Including that while white holes should act with positive radiation pressure, black holes should symmetrically act with negative radiation pressure, might resolve the black hole information paradox (?) - showing there was a lot of information exchange before reaching the end of evaporation.

https://en.wikipedia.org/wiki/Black_hole_information_paradox :

Hawking's calculation suggests that the final state of radiation would retain information only about the total mass, electric charge and angular momentum of the initial state. Since many different states can have the same mass, charge and angular momentum, this suggests that many initial physical states could evolve into the same final state.

Why would photons hitting atoms cause different behavior depending on the source?

An atom must already be in an excited state in order to experience stimulated emission. It’s not the opposite of absorption. (I vaguely recall having this discussion before)

Why do you think there are N2 atoms outside a black or white hole?

As far as radiation pressure, sure. There would be radiation pressure on a BH from the radiation incident on it. If for some reason it wasn’t isotropic the BH would experience a force.

From atomic perspective, white holes increase N2 number of excited atoms outside with absorption equation - its T/CPT analog is black hole decreasing N2 number of excited atom with stimulated emission.

Regarding radiation pressure, white hole only emits - pushing objects outside, acting with positive radiation pressure ... applying T/CPT symmetry, doesn't it mean pulling, applying negative radiation pressure?

Like applying T symmetry to marine propeller situation:

Hydrodynamics is mathematically very close to EM, allowing such marine propeller analog:

21 minutes ago, Duda Jarek said:

From atomic perspective, white holes increase N2 number of excited atoms outside with absorption equation - its T/CPT analog is black hole decreasing N2 number of excited atom with stimulated emission.

Your images aren’t loading for me but N2 could refer to the number of atoms in the excited state in a two-state system, where N1 would be the number in the ground state.

Infalling radiation would also cause excitation of atoms.

As I had previously explained, the time reversal analog would be emission from simple de-excitation.

21 minutes ago, Duda Jarek said:

Regarding radiation pressure, white hole only emits - pushing objects outside, acting with positive radiation pressure ... applying T/CPT symmetry, doesn't it mean pulling, applying negative radiation pressure?

Time reversal would change the direction of the radiation. Push or pull is semantics; the force is from the photon momentum, so it depends on the direction of travel.

Yes, N1 is the number of ground state atom e.g. in diagram, N2 of excited - absorption equation increases N2 (e.g. outside white hole), stimulated emission decreases N2 (symmetrically should be outside black hole).

Usually excited atoms mainly undergo spontaneous emission, but stimulated emission could make it faster - suggesting how to try to observe it: continuously excite the sensor of telescope, and monitor its population.

https://en.wikipedia.org/wiki/Barnett_effect can be viewed as EM analog of marine propeller - switching rotation direction to change the sign of created pressure.

Just because the model we have imagined and used says something can happen, does not mean reality has to comply.

White Holes would be a lot easier to find than Black Holes, in fact, they would be among the easiest things to spot possible.
Wer have detected thousands of BHs, some in galaxies 10 Billion years distant/ago, and we have actual photos of closer ones.

NO White Holes have ever been detected.
So basing your premise on how White Holes should act is a non-starter.

I use white holes here only to better understand black holes - as you say, the former would be trivial to observe - acting with absorption equation on sensor of telescope.

If we believe in CPT symmetry, black holes should analogously act with stimulated emission - could reduce the number of excited atoms e.g. in telescope sensor, we might be able to observe: if initially exciting it, and monitoring its population.

Sure, maybe CPT is violated and it will not work, but there are not many options to observe lone BH - this one might be slightly more practical alternative to observation of Hawking radiation ...

ps. The main diagram again as there are problems with above:

15 minutes ago, Duda Jarek said:

If we believe in CPT symmetry, black holes should analogously act with stimulated emission

Or, we can still believe in CPT symmetries, BUT, White Holes simply do not exist.

1 hour ago, Duda Jarek said:

Yes, N1 is the number of ground state atom e.g. in diagram, N2 of excited - absorption equation increases N2 (e.g. outside white hole), stimulated emission decreases N2 (symmetrically should be outside black hole).

Usually excited atoms mainly undergo spontaneous emission, but stimulated emission could make it faster - suggesting how to try to observe it: continuously excite the sensor of telescope, and monitor its population.

You offered this in the context of time-reversal symmetry, and that’s incorrect.

Yes, stimulated emission gives a photon, but photons would’ve been emitted anyway, unless there’s some nonradiative channel for de-excitation, and the atom needs to be excited in the first place, which removed a photon (unless the excitation was via some other process)

I have to think there are better ways of observing black hole signatures. Hot gas being captured is probably fully ionized anyway, so this absorption and emission would be moot. I’d look for X-rays from the accelerated charges

1 hour ago, Duda Jarek said:

https://en.wikipedia.org/wiki/Barnett_effect can be viewed as EM analog of marine propeller - switching rotation direction to change the sign of created pressure.

That seems like a stretch. Regardless, the article doesn’t provide details of the physics.

21 minutes ago, Duda Jarek said:

If we believe in CPT symmetry, black holes should analogously act with stimulated emission

Your time might be better spent understanding why stimulated emission is not time-reversed absorption. Basing any proposal on a flawed premise tends not to bear any fruit.

9 minutes ago, MigL said:

Or, we can still believe in CPT symmetries, BUT, White Holes simply do not exist.

Most believe black holes exist, here we would like to understand their properties from symmetry - existence of white holes is not needed for that.

But maybe they exist, e.g. assuming there was Big Bounce, before it I would expect symmetric formation of our white holes, so maybe also before our Big Crunch - while unlikely, I wouldn't be surprised if observing them in some future.

8 minutes ago, swansont said:

Yes, stimulated emission gives a photon, but photons would’ve been emitted anyway, unless there’s some nonradiative channel for de-excitation, and the atom needs to be excited in the first place, which removed a photon (unless the excitation was via some other process)

Both are coupling of two electrons on both sides of horizon, with photon crossing horizon in the allowed direction - we just switch Feynman diagram between white and black hole, as shown above.

But positive/negative radiation pressure seems more intuitive - like revering marine propeller or rotation in EM Barnett effect.

10 minutes ago, Duda Jarek said:

Most believe black holes exist, here we would like to understand their properties from symmetry - existence of white holes is not needed for that.

Of course BHs exist.
But your statement was

'As white hole should act with positive radiation pressure, shouldn't black hole act with negative?'

and since WHs don't exist, they don't act with positive radiation pressure, so BHs don't need to act with negative radiation pressure.

Does that clarify my position ?

15 minutes ago, Duda Jarek said:

Both are coupling of two electrons on both sides of horizon, with photon crossing horizon in the allowed direction - we just switch Feynman diagram between white and black hole, as shown above.

That doesn’t depict stimulated emission.

As far as WHs existing, you run into thermodynamics issues regarding entropy. If it were viewed as a thermodynamic process, it would not be reversible.

While we might not observe them in this moment, in theory they are possible - e.g. as consequence of BH existence and CPT symmetry.

And consequences of e.g. symmetries do not require actual realization of all possibilities.

E.g. they discuss https://en.m.wikipedia.org/wiki/Mirror_life before it actually exists (on our planet, we think)

Maybe White Holes are composed of SuperSymmetric Particles.

Oh wait ...

They're predicted by the models, but don't exist either.

35 minutes ago, swansont said:

As far as WHs existing, you run into thermodynamics issues regarding entropy. If it were viewed as a thermodynamic process, it would not be reversible.

Reversed WH dynamics is BH dynamics - seems quite reversible.

Moreover, including missing negative radiation pressure might help to finally resolve the real thermodynamical problem: https://en.m.wikipedia.org/wiki/Black_hole_information_paradox

MigL, https://en.wikipedia.org/wiki/White_hole doesn't say anything about supersymmetry?

Edited September 15Sep 15 by Duda Jarek

White holes don't exist because black holes are formed from collapsing matter. The past singularity doesn't exist because that region is occupied by the collapsing matter. Only the future singularity exists.

So imagine there was Big Bounce - wouldn't there be symmetrically white holes before for us?

There might be more ways to form them, e.g. going through https://en.wikipedia.org/wiki/Non-orientable_wormhole , and "difficult to realize" does not allow to be certain something does not exist ...

And we conclude e.g. from symmetries even if we don't know if what we consider was actually realized somewhere, it is sufficient that it is theoretically possible.

5 hours ago, Duda Jarek said:

While we might not observe them in this moment, in theory they are possible - e.g. as consequence of BH existence and CPT symmetry.

Repeating this doesn’t make it true. The universe isn’t governed solely by GR.

Reversed WH dynamics is BH dynamics - seems quite reversible.

You can’t wish away the second law of thermodynamics

5 hours ago, Duda Jarek said:

negative radiation pressure

There is no such thing. There is radiation pressure.

Perhaps you can explain why you think radiation pressure is a significant contributor to BH formation.

White hole is not my idea, but something theoretically allowed e.g. in https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates

https://en.wikipedia.org/wiki/Radiation_pressure is just p=<ExH>/c vector: positive if toward surface (pushing), negative if outward (pulling) ... https://scholar.google.pl/scholar?q=negative+radiation+pressure

Even if there would be zero WH realizations in this moment (3D submanifold of 4D spacetime), WH would only emit - pushing objects outside with positive radiation pressure, and BH are their T/CPT analogs - this transform reverses H magnetic field reversing p=<ExH>/c pressure sign to negative, like changing rotation direction of marine propeller or in Barnett effect ... still not needing having realization of WH.

The real thermodynamics problem was https://en.wikipedia.org/wiki/Black_hole_information_paradox :

Quote

Hawking's calculation suggests that the final state of radiation would retain information only about the total mass, electric charge and angular momentum of the initial state. Since many different states can have the same mass, charge and angular momentum, this suggests that many initial physical states could evolve into the same final state.

But including negative radiation pressure of BH, it is conterminously interacting with exterior, exchanging information - no need for paradoxes.

8 hours ago, Duda Jarek said:

White hole is not my idea, but something theoretically allowed

Something that’s a solution if you only consider GR, but not when you include thermodynamics

7 hours ago, swansont said:

Something that’s a solution if you only consider GR, but not when you include thermodynamics

Fundamentally there is CPT symmetry in equations governing physics, https://en.wikipedia.org/wiki/CPT_symmetry : "The CPT theorem says that CPT symmetry holds for all physical phenomena" ... which requires possibility of WH assuming existence of BH ...

Just appeared fresh Event Horizon Telescope news - showing surprising amounts of jets ... no longer surprising if thinking about this marine propeller analogy: white holes should form vortices going out, so symmetrically black holes should form vortices coming in.

New EHT Images Reveal Unexpected...

New EHT Images Reveal Unexpected Polarization Flips at M8...

"magnetized plasma swirling near the event horizon is far from static; it’s dynamic and complex, pushing our theoretical models to the limit.”

3 hours ago, Duda Jarek said:

Fundamentally there is CPT symmetry in equations governing physics, https://en.wikipedia.org/wiki/CPT_symmetry : "The CPT theorem says that CPT symmetry holds for all physical phenomena" ... which requires possibility of WH assuming existence of BH ...

Selective editing isn’t a good-faith technique*

“The CPT theorem says that CPT symmetry holds for all physical phenomena, or more precisely, that any Lorentz invariant local quantum field theory with a HermitianHamiltonian must have CPT symmetry.”

So tell me, is GR an example of a local quantum field theory, much less one with a Hermitian Hamiltonian?

*from rule 2.12

Example of tactics that are not in good faith include misrepresentation, arguments based on distraction, attempts to omit or ignore information, advancing an ideology or agenda at the expense of the science being discussed, general appeals to science being flawed or dogmatic, conspiracies, and trolling.

The upshot of the above is that while the individual particle interactions (the “physical phenomena”) are reversible, the collective behavior is not. This should really be no surprise, since we have plenty of experience with everyday classical phenomena, on a much smaller scale, that are not.

I copied shorter quote, assuming most physicists agree with "Lorentz invariant local quantum field theory with a Hermitian Hamiltonian" ... would gladly discuss if there are any doubts.

Otherwise, if there are asymmetry theorems like https://en.wikipedia.org/wiki/H-theorem , they always hide mean-field-like approximation called "Stosszahlansatz" ... one could first apply CPT symmetry and then repeat such theorem - "proving" entropy growth in the opposite direction ... well summarized in

https://www.nature.com/articles/s41598-025-87323-x : "the system is dissipative and decohering in both temporal directions"

Thinking about entropy gradient e.g. before Big Bounce, shouldn't it be reversed?