Duda Jarek

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?

Fully synthetic cells are already created and working (e.g. https://en.wikipedia.org/wiki/Artificial_cell , https://www.nist.gov/news-events/news/2021/03/scientists-create-simple-synthetic-cell-grows-and-divides-normally ) - for simple microbes it is just a matter of putting what's needed into phospholipid bag ... and there are financial motivations: to cheaply synthesize mirror chemicals e.g. for drugs. It is quite likely there will be first mirror microbes in a decade - it is now time to prepare for that: understand the dangers (e.g. taking over ecological niches while being toxic), try to prevent them ...

Thanks, added to https://en.wikipedia.org/wiki/Mirror_life ... mirror microbe by 2040?

Radiation of linear antenna is probably detected everyday, the question is minimal size of rotating dipole to still radiate EM waves? So what is the minimal number of atoms building a dipole, such that the radiation power formula from the first post still works?

Indeed, while both calculations suggest alignment already for classical magnets, they seem to lead to essentially different times for such process - bringing interesting question of which is more appropriate, has better agreement with experiment.

So please take a look in the attached article - calculations for classical magnet in external magnetic field - satisfying below equation (3), do you disagree with it? Sure such magnet is built of atoms, but I don't think atomic physics is a proper description for antenna (?)

You are focusing on internal atomic physics of these atoms, but please also take a look at the classical picture e.g. in calculation of this article. Imagine you have a nanonmagnet built of a thousand of atoms - I think you agree we can treat it as a classical magnet, so this classical calculation should be valid (?) EM radiated energy during such classical alignment might not necessarily be localized like photons (?) - rather as EM radiation of cylindrically symmetric antenna, suggesting such EM wave might be e.g. cylindrically symmetric ... I don't know if atomic physics describes well antennas? Now reduce the number of atoms one by one to a single atom ...

Ok, maybe I should use e.g. "excessive" word instead - generally a system having excessive energy (larger than minimal), has tendency to release this energy. E.g. excited atom has tendency to release excessive energy as EM radiation (photon carrying the difference of energy, momentum, angular momentum) - deexciting to energy minimum of the ground state. I see unaligned "classical" magnetic dipole in external magnetic field analogously - this field causes precession, which means excessive kinetic energy - which can be released through EM radiation, leading to aligned magnetic dipole without this excessive energy. If you want more formal classical calculation, there is a deep analysis in the linked article. Sure this is different description than quantum, the big question is where is the boundary? Why cannot they be just different perspectives on the same systems? Like phonons which are both normal modes, and effects of creation operator in perturbative QFT ...

The article ( https://www.preprints.org/manuscript/202210.0478/v1 ) uses classical electromagnetism - just a magnet in external magnetic field: should not only precess, but also finally align in parallel or anti-parallel way, what can be imagined e.g. as EM radiation of abundant (kinetic) energy, or direct calculation in this article. Please point mistake, problem in this derivation ... or if you cannot, the size boundary where it no longer works? As classical it should work for large magnets - made from how many of atoms? A million? A thousand? ... a single atom? electron? Experimentally it agrees also with the last two ... so where do you see the classical-quantum boundary here?

I was pointed recent very nice article "Phenomenological theory of the Stern-Gerlach experimen" by Sergey A. Rashkovskiy with very detailed calculation of the alignment time getting ~10^-10s for Stern-Gerlach with atoms: https://www.preprints.org/manuscript/202210.0478/v1 Instead of radiation, he directly uses formula for magnetic dipole in external magnetic field: My very approximated evaluation from radiation of abundant energy suggested a few orders of magnitude fasted alignment - bringing very interesting question if they are equivalent, how does energy balance looks above (?) Anyway, this is another confirmation that classical magnetic dipoles in external magnetic field have tendency to align in parallel or anti-parallel way. This "classical measurement" is deterministic and time-reversible: if recreating reversed EM, in theory one could reverse the process ... What is nonintuive here is that such EM radiation carrying energy difference here seems different than in "optical photon", might be delocalized (?). The big question is the minimal size to be able to apply this "classical measurement" - minimal size of such magnet: a million atoms? Thousand atoms? Single atoms? Electron? Experimentally in Stern-Gerlach they observe the same conclusion, such alignment is also well known for electrons (e.g. https://en.wikipedia.org/wiki/Sokolov%E2%80%93Ternov_effect ), for which they observe both Larmor precession, but also much more complex acrobatics in EM field: spin echo ( https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance#Pulsed_electron_paramagnetic_resonance ) So where is the classical-quantum boundary here?

I completely agree that quantum mechanically the spin alignment is never perfect, however, often is nearly perfect - e.g. in Stern-Gerlach, NMR, ferromagnets. If you could elaborate on my questions regarding classical magnet - should it precess in external magnetic field? If so radiating energy as EM waves? Until reaching nearly perfect alignment?

Excited atoms have tendency to deexcite - releasing abundant energy as EM wave (photon), through dynamics of electrons in e.g. electric potential of the nucleus. The ground state e.g. of hydrogen is just the lowest energy state for proton+electron. In theory they could be taken closer down to zero distance (->neutron), but it would require investing ~782keV energy. This kind of orbit quantization is also observed in hydrodynamical QM analogs, e.g. double quantization: https://www.nature.com/articles/ncomms4219 - of distance R and angular momentum Lz: The discussion indeed starts going in circles, and I don't think I understand the problem. So do you agree classical magnet would precess in external magnetic field? That rotating, oscillating dipole radiates energy as EM wave like antenna? That radiating all the energy such classical magnet would align in parallel or anti-parallel way? That this is the same conclusion as observed in Stern-Gerlach? Do you have an alternative explanation of such alignment in Stern-Gerlach? Alignment known also e.g. in NMR: https://www.cis.rit.edu/htbooks/nmr/chap-3/chap-3.htm

But excited atoms radiate abundant energy - getting to the lowest energy: ground state? So why shouldn't unaligned spin radiate abundant kinetic energy - getting to the lowest energy: aligned spin? ... especially that this is exactly what they observe in Stern-Gerlach ... and EM says that oscillating dipoles should radiate energy. Indeed, and in Stern-Gerlach we have free unbounded objects - having magnetic dipole, in external magnetic field - as also e.g. electrons in synchrotron radiating energy as EM waves. Magnetic dipole in external magnetic field gets torque - Larmor precession ... rotating dipole creates varying EM fields - like antenna radiating energy as EM waves, of power given by the used formula. Larmor precession comes from torque - works in all scales: from electron to macroscopic magnets. For non-polarized beam, the original direction of magnetic dipole is random, the final in Stern-Gerlach is aligned in parallel or anti-parallel way - exactly as we would expect for a classical magnet in external magnetic field.

There is this formula for power of rotating electric dipole: http://www.phys.boun.edu.tr/~sevgena/p202/docs/Electric dipole radiation.pdf Inserting k = 10^6 Hz and p ~ 10^-23, you get power ~10^-4 W ... proper calculations would require someone experienced with antennas, but generally we are talking about ~femtosecond scales. We are talking about rotating dipole and acceleration of charges/dipoles generally leads to radiation of energy as EM waves, e.g. in bremsstrahlung. The above formula is for oscillating dipole, getting the details is difficult I will think about, but generally these are ~femtosecond scales. ... and this radiation says that magnetic dipoles should align in magnetic filed - what is exactly what they observe e.g. in Stern-Gerlach.

Imagine you have some object e.g. atom, and put it into precessing coordinates - it would introduce additional time derivative terms (kinetic), until stopping this precession.

I have described classical radiation explanation leading to the same conclusion as Stern-Gerlach: of finally aligned spins. I have used the formula for EM radiation energy of antenna as oscillating dipole in the first post here. This is a complicated problem - it would be great if somebody experienced in antennas could make a better calculation. If it would be a macroscopic magnet, torque should lead to precession. Exactly the same argument is used for electron in https://en.wikipedia.org/wiki/Larmor_precession So why there shouldn't be precession in intermediate scale: of atom? And precession means additional kinetic energy - contributions with time derivative, which can be minimalized by just aligning spin - what they experimentally observe e.g. in Stern-Gerlach.

Such need is suggested by conservation laws - especially of energy and angular momentum. Magnetic dipole of random direction in external magnetic field has abundant energy (kinetic of precession) - in Stern-Gerlach somehow lost by aligning, so what happens with this energy difference? Could turn into heat, through EM interactions. Also angular momentum is different for a random initial spin and aligned final spin - what has happened with this difference? There are two effects here - "V cdot mu" energy as in Zeeman effect, and kinetic energy from precession of unaligned spin. In Stern-Gerlach the latter seems to dominate, but there should be also statistical difference of population of two beams (?) - although, it might be extremely tiny. The problem is that classical theory of radiation predicts exactly the same outcome - magnetic dipole in external magnetic field gets torque, additional kinetic energy of precession - as oscillating dipole should should EM radiate energy, until reaching minimum: when it is aligned ... exactly as seen in Stern-Gerlach. So what is the difference between such classical behavior of magnet in magnetic field, and what they observe in Stern-Gerlach?