Duda Jarek

swansont, the big question is which boundary conditions? For Euler-Lagrange we use values and derivative to start evolution in one direction - usually toward future, but can also use it toward past by t -> -t. For the least action principle we use boundary conditions symmetrically from both directions. I haven't seen general relativity solved with Euler-Lagrange: "unrolling" 3D spacetime (?) Instead, they search for static 4D shape of spacetime satisfying least action equations - Einstein's block Universe, eternalism philosophy of time: https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time) And in such least action principle view, there are allowed closed timelike curves, but the found static 4D solution (we travel through) has already resolved all potential time paradoxes: https://en.wikipedia.org/wiki/Novikov_self-consistency_principle KJW, modern physics is believed to be CPT symmetric, so asymmetries like entropy gradient need to be properties of specific solution we live in, like throwing a rock to lake (symmetric in equations). E.g. LIGO rather mostly sees retarded waves, as "collisions from our past" seem more like in our solution, but maybe it also contains reversed (?) - e.g. assuming Big Crunch and evolving backward, getting black hole collisions this way for us would be "collisions from our future" with advanced waves - maybe LIGO could see, probably for time-reversed chirp shapes (?)

But isn't general relativity solved in time symmetric way like the least action principle? How would you like to restrict causality to uni-directional in such 4D block universe view? E.g. below black hole horizon time is switched with space, or even worse: Klein-botte-like wormhole ( https://en.wikipedia.org/wiki/Non-orientable_wormhole ) could in theory apply P or T symmetry to a rocket flying through it - how do you see causality there?

General relativity is rather solved in time symmetric way, like the least action principle condition in Einstein's field equations, what as in e.g. Wheeler-Feynman absorber theory requires symmetrically both retarded and advanced solutions. So why seems there are only considered retarded gravitational waves? Can we exclude being advanced wave for all observed events ( https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations )? If not, should they use original chirp shapes, or maybe time reversed?

While your examples seem just reduced energy, time crystals are objects oscillating in the lowest energy state, which corresponds to kinetic energy so energy minimization usually kills it ... But somehow electron and neutrinos do it it - we should try to understand, and it seems to require negative terms in Hamiltonian - in perturbative approximation using negative energy virtual particles.

Seems we need negative Hamiltonian terms to explain why resting electron and neutrino are oscillating - making them https://en.wikipedia.org/wiki/Time_crystal , and such often automatically appear (e.g. https://arxiv.org/pdf/2501.04036 ) In effective descriptions they might need negative energy virtual particles, but are they also used as non-effective?

While special relativity says inertial mass is equivalent with energy, there are at least two more types of mass, for which equivalence seems not so certain - let me briefly summarize and ask for more arguments for/against their equivalence. Gravitational mass is hypothesized to be equal by equivalence principle, and gravitational interaction of antimatter now seems nearly certain to be the same (?) However, all these tests are for baryons and bulk matter made of them, for non-baryons I am aware only of this 1967 Witteborn, Fairbank test for electron - measuring maximal time for thermal electrons reaching upper electrode tmax=sqrt(2h/g), which turned out infinite, suggesting g=0. But later it was explained as due to gravitational charge gradient in shielding, so seems experimentally we still don't know (good slides). de Broglie clock, zitterbewegung - e.g. relativistic QM requires E=mc^2 for psi ~ exp(-iEt/hbar). For electron it was directly confirmed ( https://link.springer.com/article/10.1007/s10701-008-9225-1 ) by observing increased absorption of 81MeV electron beam when agreeing with spatial lattice of crystal, however, they got 0.28% disagreement. The same oscillation formula was used to introduce 3 masses based on neutrino oscillations, but experimental confirmation they are equivalent to energy seems quite difficult (maybe GERDA?) Are there some more arguments they are equal or not? Past and future experiments to improve the situation?

So you are saying that while circulating electron loses energy, circulating positron gains it? I think both are losing in our perspective, and both are gaining from CPT perspective. It can gain energy by synchrotron self-absorption, but it would need emitters in the past - which are rare now ... in contrast to absorbers in our future. In CPT perspective it is the opposite: more emitters than absorbers.

But as you have quoted “The CPT theorem says that CPT symmetry holds for all physical phenomena" ... So do you say "circulating charge" is outside of "all physical phenomena"? Or propose some understanding (I haven't seen in your posts)? I have proposed one: because there is more absorbers than emitters - do you agree, disagree (why?), or have a different understanding?

CPT symmetry says it doesn't matter if you look at circling charge forward or backward in time ... but it clearly depends in solution we live in. There is clear asymmetry we should understand ... and it seems essentially different than entropy asymmetry.

CPT symmetry is supposed to be in equations governing physics, so its violations need to be in solution. Indeed like entropy asymmetry ... but how would you like to conclude this emission asymmetry from it? I don't see how to do, looks like a different type of asymmetry - literally presence of more absorbers than emitters, reversed in CPT perspective.

Yes, it is called synchrotron self-absorption ... but the question is why emission is dominating in our perspective, but in CPT perspective absorption is dominating? Is it because of more absorbers than emitters? No, I am asking why against CPT symmetry: in our perspective circulating electron loses energy, but applying this symmetry it gains energy instead?

Yes, they are not the same - against CPT symmetry, the question is: why? I think because there is now more absorbers than emitters - do you agree, or have a different answer?

Electrons circling due to magnetic field, in CPT perspective become positrons circling in the opposite direction. But CPT symmetry says that both are governed by the same equations - so why the former loses energy, but applying symmetry it gains energy instead? I am not neglecting this obviously observed asymmetry, but ask where it comes from?

While physics is believed to be CPT symmetric in equations, this symmetry is clearly violated in solution we live in, e.g. by entropy growth. I would like to ask about different asymmetry in solution: that circulating electron loses energy due to synchrotron radiation, but in CPT perspective it is also circulating charge - now gaining energy. Can we say that this asymmetry comes from that there are more absorbers in our future than emitters in our past?

Photon in QFT is e.g. a coupling between two electrons using below Feynman diagram - requires both emitter and absorber, they are switched in perspective of CPT symmetry. So can photon be emitted if there is no absorber on the way? A practical example: from radiotelescope with thermally excited resonator - while it is focused on absorption, in theory its antenna could also emit e.g. thermal excitations (seen as negative signal), but used frequencies are very difficult to absorb, often such directional EM wave would just travel to infinity through space, so from CPT perspective would have no emission mechanism. Can radiotelesope emit if such EM wave would just travel to infinity?

Modern physics is CPT symmetric, requires eternalism/Einstein's block Universe philosophy of time - assuming our Universe will finally collapse, the situation before such Big Crunch (BC) seems quite similar to after our Big Bang (BB). It brings many questions (yellow), maybe also answers - I would like to propose to discuss. For example: 1) From entropy perspective, thermodynamical parameters like densities seem very similar near BB and BC - so shouldn't the final entropy be similar? But if so, it means finally entropy should start decreasing - does it mean reversed 2nd law of thermodynamics near BC? How would evolution backward from BC differ from evolution forward from BB? What can we say about situation after BC, before BB (cyclicity)? 2) Currently synchrotron radiation mostly emits, naively against CPT symmetry, but usually asymmetry comes from solution - does it just mean it is now easier to find target for excitation in the future, than for deexcitation in the past? Would it be the opposite before BC? I was inspired here by recent https://iopscience.iop.org/article/10.1209/0295-5075/ad2088/pdf suggesting such inversed beta/statistics in black hole. 3) Spontaneous emission seems to have similar asymmetry now - would it be reversed near BC? Could they help each other by positive/negative radiation pressure/Feynman diagrams coupling them? 4) While after BB there is tendency to form black holes, shouldn't there be tendency to form white holes before BC? Could they "survive till the end"? Rather lone - so how could we exclude/confirm that a lone shining point is a white hole? What spectrum should they have? As white hole would act with positive emission pressure exciting atoms outside, shouldn't black hole act with negative radiation pressure deexciting atoms outside?

There is this legendary https://en.wikipedia.org/wiki/Collatz_conjecture even getting Veritasium video "The Simplest Math Problem No One Can Solve": that using rule "divide x by 2 if even, take 3x+1 otherwise" at least experimentally from any natural number there is reached 1 - any thoughts? It seems natural to try to look at evolution of x in numeral systems: base-2 is natural for x->x/2 rule (left column), but base-3 does not look natural for x->3x+1 rule (central column). However, rANS ( https://en.wikipedia.org/wiki/Asymmetric_numeral_systems ) gluing 0 and 2 digits of base-3 (removing 1 bit of information) looks quite natural (right column) - maybe some rule could be found from it helping to prove this conjecture?

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.

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.

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)

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.

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.

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:

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.

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