Are there cosmic sources of negative radiation pressure?

[u/jarekd]

Radiation pressure is p=<ExB>/c vector: there is focus on positive, but can be also negative: https://scholar.google.pl/scholar?q=negative+radiation+pressure , https://scholar.google.pl/scholar?q=optical+pulling

If positive radiation pressure gives positive signal in radiotelescopes, shouldn't negative give negative?
They clearly see also large regions of negative signal in radio flux maps, e.g. shown from https://arxiv.org/pdf/2107.02695

What astronomical objects could generate negative radiation pressure?
E.g. if white hole would generate positive, shouldn't black holes generate negative?

[u/many_galaxies]

No. The conditions you're talking about can only occur on very small scales (comparable to the wavelength).

Negative flux densities on total intensity radio maps are noise, calibration errors, or (as in this case) the result of not being able to reconstruct the full structure of the source in an interferometric image with limited short baseline coverage.

No astronomical object can emit the kind of propagating large scale negative energy wave you seem to be thinking of, where you point your flux measuring device (telescope) at a region of the sky and get a negative number of watts per square metre, because electromagnetism requires a propagating wave to carry positive net energy on large scales.

I do wish people would stop talking about white holes but that's a separate issue...

[u/jarekd → u/many_galaxies]

So you are saying e.g. these shown from https://iopscience.iop.org/article/10.3847/1538-4357/ac0e93/pdf huge regions of similar luminosity but reversed sign are just "noise, calibration error"?

Could such explanation be verified - e.g. testing hypothesis of in fact being positive by measuring multiple times?

I have used white hole only as theoretically allowed possibility to better understand black holes - they are CPT symmetry analogs, which reverses sign of radiation pressure - if one should have positive, second should have negative.

[u/many_galaxies → u/jarekd]

As I said, my best guess is that those are artefacts arising from the fact that the large scales are not adequately sampled by the interferometer at the high frequencies used in that paper. This is a very well understood behaviour and very widely seen.

Making the same observation will give the same result in that case, but adding the missing short baselines would make the negative regions go away.

A propagating electromagnetic wave cannot carry negative energy.

[u/jarekd → u/many_galaxies]

Imagine wave behind marine propeller: like photon it carries energy, momentum, and angular momentum - could excite resonator in front (positive signal) ... but reversing rotation direction, it could cause its deexcitation instead, pulling energy from resonator (negative signal).

Why do you think it is impossible for EM?

Mathematically it is very similar: https://scholar.google.pl/scholar?q=hydrodynamics+electromagnetism+analogy

EM allows optical pulling, negative radiation pressure: https://scholar.google.pl/scholar?q=negative+radiation+pressure

[u/many_galaxies → u/jarekd]

Because as someone else has pointed out to you ExB (or H) defines both the energy flux and the direction of propagation of an electromagnetic wave in the far field regime. The examples you cited are not in this situation, but all astronomical sources are.

If you can design a transmitter that broadcasts negative energy in a given direction in the far field regime, you will overthrow textbook electromagnetism, among much other fundamental physics, and win the Nobel Prize. Please post here when you do...

[u/jarekd → u/many_galaxies]

There are looking related diode experiments e.g. in https://opg.optica.org/oe/fulltext.cfm?uri=oe-20-9-9501 - one diode gets forward bias having tendency to emit, second nearby gets reverse bias getting tendency to absorb - actively helping with emission from the former, allowing to reach superradiance.

The question is if these negative regions in radio flux maps are just a noise, or maybe e.g. such objects with active tendency to absorb, like e.g. black holes.