Duda Jarek

Also, pulling with photons is done e.g. by https://en.wikipedia.org/wiki/Optical_tweezers EM radiation pressure is <E x H>/c ( https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_pressure_from_momentum_of_an_electromagnetic_wave ) - doesn't have to be positive.

Turns out there is considered "negative radiation pressure" - predicted for solitons, searched e.g. for mechanical waves on graphene: https://scholar.google.pl/scholar?q=negative+radiation+pressure ... so the question is if it could be realized with EM waves, photons using lasers? Because believing in CPT symmetry, from its perspective photon trajectories would be reversed, the target on the left would be "standard target" to which we "push photons" (absorption equation), what from perspective without CPT would mean emission equation, "pulling photons", "negative radiation pressure".

The T transform here reverses photon direction, making the laser cause excitation of target on the left, what means causing deexcitation without T symmetry. Look at the two equations (from https://en.wikipedia.org/wiki/Stimulated_emission#Mathematical_model ) - to which of 3 targets they apply? The equation on the right applies to the central and right target. The equation on the left applies to the central target - my point is it also symmetrically applies to the target on the left - because in perspective after CPT symmetry the equations are switched.

The CPT theorem says that looking at setting from perspective after CPT symmetry, it should be governed by the same physics. For the discussed setting with asymmetric light source, in perspective after CPT symmetry the two target would be switched, laser would increase the number of excited atoms in the target on the left - toward negative time, what means decrease toward positive time. In other words, it should stimulate emission from this target - not only when it is the central pumped crystal, but also when it is shifted left.

To observe the dN_2/dt = -B rho N_2 evolution, we need N_2 > 0 initial excitation of the target - e.g. gas discharge lamp. Its continuously excited atoms normally deexcite in isotropic way, the laser should additionally increase probability of directional deexcitation - what would be seen by detectors around, watching isotropic radiation, by reduction of seen light intensity.

Mathematically, we have the two equations (from https://en.wikipedia.org/wiki/Stimulated_emission#Mathematical_model ), after CPT they would be switched: the right one (absorption equation) would apply to the target on the left, what without CPT means the emission equation should apply to the target on the left. In other words, while laser causes absorption by target on the rights ("push photons" there"), CPT symmetry says it has to also cause emission by target on the left ("pull photons" from there) - if only N_2 > 0: satisfied condition of being excited in the first place, e.g. lamp. To my knowledge, existence of such effect was not tested yet (?) - negative result would mean macroscopic violation of CPT symmetry, positive would lead to lots of new possibilities/applications.

From perspective after CPT symmetry, you would cause excitation of atoms of target on the left, what means causing deexcitation in perspective without CPT - sure polarized beam would mean pumping/unpumping one polarity, there should be also unpolarized settings, e.g. using free electron laser, wiggler/undulator, synchrotron radiation.

CPT violation would be not seeing this looking unknown effect required by CPT symmetry - that as we "push photons" to the target on the right, we should also symmetrically "pull photons" from the target on the left - because from perspective after CPT transform, we would "push photons" to this target. I also suspect this effect is true, but it needs experimental confirmation - if positive, it would open lots of new possibilities, applications. E.g. in case of low probability nuclear transition producing characteristic gammas, we could "pull them" this way e.g. with free electron laser - hopefully stimulating this nuclear transition. In case of negative result: preparing setting able to see effect on expected level but not seeing it, would mean violation of CPT symmetry on macroscopic level - that macroscopic setting does not work the same in perspective after CPT symmetry. Such credible negative result should also inspire further experiments - improving on potential limitations, searching for the scale where CPT starts being violated and its mechanisms.

Indeed stimulate the target to emit/deexcite, like pulling photons out of it - suggested by symmetry (T/CPT) ... if possible could lead to lots of new applications, e.g.: - new calculation possibilities e.g. for quantum computing, - low probability nuclear transitions - if they produce some characteristic gammas, then they could be stimulated by such caused deexcitation - these high energy photons are available e.g. in free electron lasers, wigglers/undulators in synchrotron ... also in standard laser setting using above Einstein's equation. Which nuclear transitions would be the most interesting, practical? - similarly for chemistry - probably useful for many technological processes ...

To test application of the emission formula for the target on the left, it needs to be initially excited - e.g. a lamp. In this case it would deexcite in isotropic way - the question to test is if there is additional deexcitation caused by the laser, what would be seen by detectors around: in this case getting a lower power of light.

The polarization might be interesting to try to use it to stimulate deexcitation of one polarization of atoms, what might allow e.g. for CPT analogue of state preparation for quantum computing. The basic test is for nonpolarized target: if the formula on the left applies also to the target on the left, as suggested by CPT symmetry switching the targets. The main difficulties of such test is requirement of high N_2/N excited population, and that the asymmetry is imperfect - some percentage of photons travel in the opposite direction, exciting our target. You are writing about the central target (pumped crystal) - to which both equations apply. The question is about the left/right targets - CPT symmetry suggests both should have corresponding formula.

Here is another perspective on the ring laser setting using formulas from https://en.wikipedia.org/wiki/Stimulated_emission There are two (Einstein's) formulas - for absorption it applies to the central target (pumped crystal), and the standard target on the right. The symmetric emission formula is considered only for the central target. However, in perspective after CPT symmetry the targets and equations would switch - hence emission formula should also symmetrically apply to the target on the left - stimulate its deexcitation (if satisfying condition of being excited). Some potential applications of such suggested by CPT symmetry stimulated deexcitation, intuitively "pulling of photons": - low probability nuclear transitions - if they produce some characteristic gammas, then they could be stimulated by such caused deexcitation - these high energy photons are available e.g. in free electron lasers, wigglers/undulators in synchrotron ... also in standard laser setting using above Einstein's equation. Which nuclear transitions would be the most interesting, practical? - similarly for chemistry - probably useful for many technological processes (which ones?). - maybe stimulated proton decay - ultimate energy source: complete matter -> energy transition, ~100x energy density than fusion from any matter. Violation of baryon number is required e.g. by baryogenesis, Hawking radiation. They cannot observe it in room temperature water, but maybe it is a matter of proper conditions, like pulling photons of characteristic energies by some powerful free electron laser? Could use normal laser setting. - ?

Deexcitation is time/CPT reversal, analogue of excitation - here caused by the action of laser.

Isn't it lots of microscale tests? The CPT symmetry seems nonintuitive especially due to time symmetry, e.g. applying it to macroscopic scenario with clear causality, naively it should reverse causality, e.g.: CPT(laser causes excitation of target) = CPT(laser) causes deexcitation of CPT(target) microscopically: CPT(stimulated emission) in laser = stimulated absorption Is it true? If so, it could bring lots of applications, but seems unknown ...

Thanks for the list, so I think we agree CPT should be true also in macroscale - but were there experiments really testing macroscopic CPT? If not, maybe it is worth to design and conduct such tests - like proposed, using time-asymmetric light sources e.g. ring laser or free electron laser. The only nonstandard in the discussed setting is being "behind" instead of "in front" of the source of coherent light ... but becoming proper "in front" when looking from perspective after applying CPT symmetry. This way we would ask physics if it works the same after applying CPT. Microscopically, while e.g. laser cooling is CPT analogue of laser heating, we are asking if there exists CPT analogue of stimulated emission - some stimulated absorption.

Because in CPT transform of this setting, photon directions would be reversed - laser would excite this target: increase probability of its atoms being excited. Hence returning from CPT, it translates into increased probability of these atoms being deexcited.

I imagine there would be both - standard isotropic deexcitation, plus slightly increased probability of deexcitation in the direction of laser.

Thanks, I couldn't access this article ("downloaded 2 times"), but there is accessible another from J-PET team (next building to mine): "The tests of CP and CPT symmetry using the J-PET detector" https://www.epj-conferences.org/articles/epjconf/pdf/2019/04/epjconf_meson2019_05027.pdf They study decay of positronium - this is microscopic CPT symmetry, while the suggested laser ring experiment is supposed to test macroscopic CPT symmetry ... from microscopic perspective asking if there is CPT analogue of "stimulated emission" as "stimulated absorption"? Better than ring laser would be free electron laser (FEL), but they are much more difficult to access. The problem I see is that ring laser, in contrast to FEL, has some percentage of photons traveling in the opposite direction - exciting our target, making its hypothetical stimulate deexcitation more difficult to detect. What other problems can you point in such ring laser test of CPT symmetry?

Sure such continously excited lamp would deexcite - normally in isotropic way. However, applying CPT symmetry to the above setting, CPT of laser would cause excitation of target, what without CPT translates to additional directional radiation - increase of deexcitation rate in direction toward laser, I would like to test.

Applying CPT symmetry to this ring laser setting, would reverse photon directions - CPT(laser) would cause excitation of target ... hence returning from CPT symmetry, it means laser would cause deexcitation of target. The central question is if after CPT symmetry physics works as ours (assumption used in the above statement) - including macroscopic physics, this experiment is supposed to test. Maybe it doesn't, what would be also interesting and publishable - as probably first macroscopic CPT test (?), inspiring further experiments. The problem I see is that, in opposite to free electron laser, such ring laser is not perfect - rather also has some small percentage of photons traveling in the opposite direction, exciting the target - making detection of hypothetical caused deexcitation more difficult. The frequencies of excited target and laser need to overlap, the more the better, e.g. some gas discharge lamp with narrow spectrum, or maybe another laser. I don't understand the need for SPDC? For now these are energy balance calorimetric-type measurements requiring high luminosity ... if successful, much better methods will be soon developed.

I have tried to organize such test of CPT symmetry in synchrotron, but it turns out technically challenging. However, searching for a different laser having clear time asymmetry, a colleague has suggested that there are ring lasers - using optical isolator as kind of photon diode, enforcing photons traveling in one direction. Applying CPT symmetry to the below setting, photons would travel in the opposite direction - causing excitation of the target (lamp). So going back from CPT to to the original setting, shouldn't they cause deexictation of the target? I am looking for access to ring laser to organize such test of CPT symmetry - please contact me in this case.

Better diagram for hypothetical https://en.wikipedia.org/wiki/Non-orientable_wormhole - if they are allowed by physics, there should be also allowed T(laser) causing deexictation of target. If the above test of existence of such effect e.g. in synchrotron will turn out negative (working on it), it could be used e.g. as counterargument against possibility of non-orientable wormholes, or as argument for causality indeed working only in past->future direction (against CPT symmetry). If the test would turn out positive, already possibility of stimulating deexcitation of target in chosen frequencies should probably quickly find hundreds of applications e.g. in technological processes, chemistry.

Electron is much more - quantized electric charge, somehow of finite energy (infinite for perfect point charge) ... plus magnetic dipole moment and angular momentum ... plus zitterbewegung/de Broglie clock - confirmed experimentally: https://link.springer.com/article/10.1007/s10701-008-9225-1 We can simulate some aspects of electron, but it seems we are still far from its complete understanding.

I also think it should remain valid in macroscopis physics - just imagine building larger and larger Feynman diagrams. However, CPT naively reverses causality direction, like in this hypothetical rocket which traveled through Klein-bottle-like wormhole - what seems highly controversial. Taking a setting with clear causality direction e.g. this laser causes excitation of its target later, if constructing CPT analogue of this situation, should CPT(laser) cause deexcitation of target earlier? While building CPT analogue of laser seems technically extremely challenging, at least for free electron laser(FEL) it seems realizable: just replace electrons with positrons traveling in the opposite direction. To test if it can cause deexcitation of target, we could use e.g. a gas-discharge lamp continuously exciting its atoms as the target - the big question is if such CPT(FEL) could increase deexcitation rate in this direction? (what could be measured monitoring lamp's energy balance) I don't know and believe only experiment could really answer this question (?) - I would love to conduct (if only getting allowance to place such lamp e.g. in synchrotron?)

CPT symmetry (charge, parity, time) is at heart of modern physics: However, it seems treated seriously only in scale of Feynman diagrams with a few particles - is it still valid for macroscopic physics? Feynman diagrams of Avogadro's scale numbers of particles? In other words, if preparing CPT(initial conditions), should they lead to CPT(their evolution) ... including time reversed causality direction? While it seems technically challenging to prepare CPT(initial conditions), in theory general relativity allows to prepare T(initial conditions) - by hypothetical Klein-bottle-like wormholes ( https://en.wikipedia.org/wiki/Non-orientable_wormhole ) e.g. rotating 180 deg. light cones - while standard laser causes excitation of its target, would laser in a rocket traveled through such wormhole cause deexcitation of target?