5 hours ago, Duda Jarek said:

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?

The title of that is “Emergence of opposing arrows of time in open quantum systems” (again, you sin by omission)

GR is not a quantum theory, and the systems under discussion are subject to non-quantum processes.

"the system is dissipative and decohering in both temporal directions" was only my favorite quote from https://www.nature.com/articles/s41598-025-87323-x , not clearly different title.

The fact that there is no mainstream unification of EM + gravity, only shows its ignorance - does not mean nature does not interact this way.

Personally, I see Einstein's attempt to unify EM + gravity as the most promising: https://en.wikipedia.org/wiki/Teleparallelism

Edited September 17Sep 17 by Duda Jarek

For better intuition, it is good to imagine vacuum cleaner with both suction and blow mode, switched by T/CPT symmetry - white hole has lightcones directed outside, hence would only blow also electromagnetically (positive radiation pressure outside - sucked from inside) ... and  black hole as its T/CPT symmetry is not "doing nothing" but should have symmetric suction, also electromagnetic (negative radiation pressure outside - positive inside).

Edited September 18Sep 18 by Duda Jarek

2 hours ago, Duda Jarek said:

For better intuition, it is good to imagine vacuum cleaner with both suction and blow mode, switched by T/CPT symmetry

Which mode requires power input, while the other creates it?

Analogies are limited because they fail to account for all details, and this analogy doesn’t account for the critical concept that makes white holes impossible

Are you going to address the issues I raised, or does this get closed?

The process is "propelled" by bent lightcones - leading to photon/EM stream only in one direction, positive radiation pressure p=<ExH>/c in one direction, becoming negative in T symmetry as it reverses magnetic field B ... exactly as for blowing-sucking vacuum cleaner.

EM and hydrodynamics are governed by analogous equations like below, https://en.wikipedia.org/wiki/Barnett_effect gives EM analog of marine propeller ... but I have used it only for intuitions, we can just apply T symmetry to EM as above.

I have really tried to address your issues on the go - please elaborate if you think I have missed something?

a

23 minutes ago, Duda Jarek said:

The process is "propelled" by bent lightcones - leading to photon/EM stream only in one direction, positive radiation pressure p=<ExH>/c in one direction, becoming negative in T symmetry as it reverses magnetic field B ... exactly as for blowing-sucking vacuum cleaner.

EM and hydrodynamics are governed by analogous equations like below, https://en.wikipedia.org/wiki/Barnett_effect gives EM analog of marine propeller ... but I have used it only for intuitions, we can just apply T symmetry to EM as above.

I have really tried to address your issues on the go - please elaborate if you think I have missed something?

a

Where have you addressed the thermodynamic objection to the existence of these hypothetical things?

Edited September 18Sep 18 by exchemist

38 minutes ago, Duda Jarek said:

I have really tried to address your issues on the go - please elaborate if you think I have missed something?

Since you’re apparently unable to read what I wrote, there’s entropy and why you think radiation pressure is a significant contributor to BH formation.

5 hours ago, Duda Jarek said:

it is good to imagine vacuum cleaner with both suction and blow mode, switched by T/CPT symmetry

Just to point out that you cannot make CPT, or PC, etc into a "physical switch", as it is not an active symmetry. So the example is not a good one, in my opinion.

I also agree with arguments that have surfaced by other members, that CPT is an inescapable consequence of QFT (Lorentz invariance plus crossing symmetries of the S matrix), but it's not necessarily a symmetry of a non-linear theory like GR. The status of GR as per CPT is that it just happens to be CPT-invariant in its present formulation.

The possibility that there be white holes may be tantalising, but there are no astrophysical candidates for them so far.

We had exchange regarding CPT vs 2nd law of thermodynamics - the former is fundamental in equations, the latter e.g. in H-theorem needs "Stosszahlansatz" mean-field-like approximation, which e.g. applied after symmetry would give reversed entropy gradient ... like in mentioned quote "the system is dissipative and decohering in both temporal directions" from https://www.nature.com/articles/s41598-025-87323-x

Not having realization of e.g. white hole, still allows to conclude from symmetries ...

But ok, let's think about black hole alone - from below BH horizon there would act positive radiation pressure from horizon (like above for WH):

p = <ExH>/c would be directed toward a surface below BH horizon, what means positive radiation pressure.

And symmetrically for surface above BH horizon, this radiation pressure p vector would be pointing outward - what means negative radiation pressure.

Such blow-suction "electromagnetic vacuum cleaner" works across the BH/WH horizon - for BH blowing toward inside horizon, but toward outside it is not "doing nothing" but should act with suction - actively pull electromagnetically, like acting with stimulated emission equation on atoms.

Edited September 19Sep 19 by Duda Jarek

7 hours ago, Duda Jarek said:

Such blow-suction "electromagnetic vacuum cleaner" works across the BH/WH horizon - for BH blowing toward inside horizon, but toward outside it is not "doing nothing" but should act with suction - actively pull electromagnetically,

Why does this matter? i.e. how does this affect the formation of the BH? How big is this effect going to be?

7 hours ago, Duda Jarek said:

like acting with stimulated emission equation on atoms.

Stimulated emission results in a force on the atom in the opposite direction of the photon direction, so I don’t see the connection.

7 hours ago, Duda Jarek said:

We had exchange regarding CPT vs 2nd law of thermodynamics - the former is fundamental in equations, the latter e.g. in H-theorem needs "Stosszahlansatz" mean-field-like approximation, which e.g. applied after symmetry would give reversed entropy gradient

I guess you missed where it points out that H-theorem violates T symmetry.

The strength of the effect can be found from the absorption-stimulated emission equations above, which are switched in T/CPT perspective - the former should act below BH horizon, the latter above, the opposite for WH.

If caused by negative radiation pressure, it should be literally pulling of photons e.g. from excited atoms ... like marine propeller pulling energy from excited resonator:

Should lead e.g. to dimming of shinning matter surrounding black hole, and maybe could be observed in various ways ...

Edited September 19Sep 19 by Duda Jarek

2 hours ago, Duda Jarek said:

The strength of the effect can be found from the absorption-stimulated emission equations above, which are switched in T/CPT perspective - the former should act below BH horizon, the latter above, the opposite for WH.

Those equations don’t tell you the strength of the radiation pressure, they tell you population change rates (dN/dt), and they are not time symmetric unless N1=N2, which is steady state. If N1>N2, you’ll see N2 increasing when time runs forward and decreasing when it runs backward.

2 hours ago, Duda Jarek said:

If caused by negative radiation pressure, it should be literally pulling of photons e.g. from excited atoms ... like marine propeller pulling energy from excited resonator:

Should lead e.g. to dimming of shinning matter surrounding black hole, and maybe could be observed in various ways ...

Sorry, what neutral atoms would these be? I asked about this before.

The absortpion equation is consequence of positive radiation pressure of photons.

CPT analog of this scenario is stimulated emission by negative radiation pressure - like above marine propeller pulling energy from excited resonator.

Neglecting it is like saying that vacuum cleaner is only blowing, but does nothing from the suction side - to act with positive radiation pressure inside horizon of BH, there is necessary negative outside.

A number of years ago, I simulated the second law of thermodynamics on an Excel spreadsheet. The system I simulated was very simple, intended to remove the complications associated with physics and chemistry. As a result of this simulation, it became clear to me that transition probabilities are not time symmetric. If one considers the reversible interconversion between two compounds, the rate constant of this reaction reverses sign under time reversal. This allows the description of the progress of the equilibration reaction to remain covariant with respect to time reversal, resolving an apparent incompatibility between the second law of thermodynamics and relativity. But transition probabilities are positive valued. Therefore, when the rate constant reverses sign under time reversal, it no longer corresponds to a transition probability. A process that obeys statistics in the forward time direction does not obey the same statistics or indeed any statistics in the reverse time direction.

Edited September 19Sep 19 by KJW

Spontaneous emission is not symmetric, as by excitation there is created tendency to emit photons, which can be absorbed by various targets, getting Feynman diagrams of e.g. electron-electron coupling by photon, where emitter is localized, but absorber is practically random ... entropy is growing.

But absorption-stimulated emission equations are switched by CPT symmetry.

41 minutes ago, Duda Jarek said:

The absortpion equation is consequence of positive radiation pressure of photons.

CPT analog of this scenario is stimulated emission by negative radiation pressure - like above marine propeller pulling energy from excited resonator.

It’s a consequence of a resonant photon flux. The direction doesn’t matter, and there’s no way to calculate a pressure or force from the information. There’s no direction, so there is no “positive”

https://en.m.wikipedia.org/wiki/Radiation_pressure says p=<ExH>/c, which can be toward surface (positive e.g. below BH horizon) or outward (negative e.g. above BH horizon)

2 minutes ago, Duda Jarek said:

But absorption-stimulated emission equations are switched by CPT symmetry.

Any equation can be switched by reversing time, but that doesn’t make them symmetric. N1 and N2 refer to different states, and if the system isn’t in steady-state you can discern the direction of time.

3 minutes ago, Duda Jarek said:

https://en.m.wikipedia.org/wiki/Radiation_pressure says p=<ExH>/c, which can be toward surface (positive e.g. below BH horizon) or outward (negative e.g. above BH horizon)

But those surfaces aren’t in the equation. “The absortpion equation is consequence of positive radiation pressure of photons.” is not an accurate statement.

And pressure is a scalar.

Acting with positive radiation pressure we increase N2 ... what applying T/CPT symmetry becomes decreasing N2 by negative radiation pressure.

Natural for marine propellers, vacuum cleaners ... but wrongly neglected for EM.

1 hour ago, Duda Jarek said:

Acting with positive radiation pressure we increase N2 ... what applying T/CPT symmetry becomes decreasing N2 by negative radiation pressure.

How does an atom know if the radiation pressure is positive?

Let’s say you start with atoms all in the ground state (1). How will you decrease N2? It’s zero.

Even if you have atoms in state 2, how will N2 decrease when you have photons hitting atoms that are in state 1, causing them to go to state 2? In the two state system Einstein describes, N2 doesn’t decrease. If it did, you’d know time was running backwards, which is not supposed to happen if you had a good symmetry.

One of several things you don’t seem to get here is both equations are in play at the same time. The equations tell you what happens to N1 and N2 when you shine a flux of resonant photons on them. N1 goes down and N2 goes up until you are in steady state. (N1+N2 is constant). CPT wasn’t even proposed until decades after Einstein did this work.

https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_pressure_by_emission also says about photon intensity, positive absorbed by ground state atoms, exciting them, e.g. inside BH horizon.

But outside BH horizon this <ExH>/c radiation pressure becomes outward surface - negative radiation pressure, should pull photons e.g. from excited atoms by symmetric analog: stimulated emission equation.

4 hours ago, Duda Jarek said:

https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_pressure_by_emission also says about photon intensity, positive absorbed by ground state atoms, exciting them, e.g. inside BH horizon.

But outside BH horizon this <ExH>/c radiation pressure becomes outward surface - negative radiation pressure, should pull photons e.g. from excited atoms by symmetric analog: stimulated emission equation.

Repeating this does not address the issues I pointed out. Which, if you did, would underscore the problems with your idea.

As it is, you’re just soapboxing, and showing no interest in learning the details of the physics involved (I spent ~30 years working in this area of physics. I think it’s quite interesting) IOW, you don’t need to try to explain the details of radiation pressure to me. It’s not the impediment here.

Don’t bring it up again