geordief

I haven't actually listened to this in half a century (I am going to).Apparently the subject matter is in the news as a genre of writing is showing up (unbeknownst to me ) over the past while. 'Complex, dangerous, sexual beings': The erotic, so-calle...The fairies in erotic "fae" romantasy are not cute or benevolent. They are dangerous, sexual beings, which is exactly what they were in historic folklore, according to a new book.I remember this as a really great song on a really great album(Liege and Lief) with a fantastic singer in Sandy Denny ,who very sadly departed this world via the staircase ,as I remember.

Thanks. Would there be any actual practicality to that? I mean ,are there any physical scenarios where the probability of an interaction can be predicted by summing all the possible paths from a point of emission? Or are we just in interpretation territory ? (Out if the top of my hat ,might quantum computing involve that kind of a scenario?-I don't have any understanding of that subject apart from superposition and ,presumably decoherence being involved)

So good I think I will post it twice

If I can just continue this thread without opening a new one,I think this would be a related question..... I think the "all possible paths traveled" may have been Feynman's favourite interpretation of the model. Can I ask ,when these paths are (if they are) drawn and calculated are physical impossibilities and constraints built into the calculation? ie some paths might require faster than c transfers and some paths might encounter strong spacetime curvature. In the "theory" (if this can be called a theory) ,but not perhaps in practicality are the probabilities (zero ,perhaps in many cases) weighted accordingly? Also is "tunneling" a class of travel that is included?

And vice versa? Does muscle not actually turn to fat (as I think I have heard said) but does it simply waste away - with fat increasing or decreasing regardless? Ps I wonder if there have been studies as to whether body building is a physically unhealthy recreation in the long term (I am sure practioners may feel the opposite)

When 2 quantum objects interact does the outcome depend in some way on how each of the two objects "know" each other ? Is that where the Uncertainty principle comes into play? Does each object need to know both positions and momenta of the system in order to "decide" how the system evolves subsequently? It is not just an observer who cannot measure this but the physical objects themselves have to know this for the outcome to be considered exaxtly "predetermined".. Just as Feynman strongly emphasized at the end of the lecture ,paraphrasing "it is as if Nature herself doesn't know her next move"

Can BEC s form spontaneously?(could we ever know if they did?)

I was thinking of an outside atom which might have been entangled with one of the atoms before it entered the BEC.. Is that possible ,or of any possible consequence? (Would the creation of the BEC break any prior entanglement?)

Can a BEC decohere spontaneously and without interaction with an outside system? Is there any theoretic limit to the number of atoms that can be "assembled" and has there been any question as to whether an entangled atom (I think you can entangle atoms but I could be wrong ) can be involved in any of this? Edit :a very quick search indicates that atoms can indeed be entangled, eg https://www.sciencedaily.com/releases/2026/01/260126075842.htm

Do you know what happens to the information each atom has vis a vis each other as they are seemingly subsumed into some kind of a communal identity? When they re-emerge has that information evolved to a new configuration or does it return to the same configuration it had prior to the change of status?

Does that mean that no constituent part of a BE condensate can have any interaction with a neighbouring system but can only interact with it as a group? Would that in anyway involve faster than light(or instantaneous) transmission of information ? Or does the BE condensate unravel like a ball of wool when disrupted?

Everything ,including orientation would be important but I was interested as to whether quantum objects/systems in particular could be identical in every regard or whether this could be ruled out in all circumstances.

I think I mean for all(physical) purposes. We know that no matter to what degree of identity we prepare any two systems they will evolve differently. I wonder if this is due to the "embedding system" ,a property of any two "identical" pairs or a(non-linear?)combination of both. Yes ,that is how I took it. Will have to look at those theorems.They seem relevant

If we call those 2 atoms "systems" ,is there any sense in which they can be considered as "isolated systems" or does /can their quantum state incorporate the system in which they are "embedded"?

I was listening to a Feynman lecture on the 2 slits experiment and he finished his talk by saying that it used to be thought that if a system was set up accurately enough then it was possible ,in theory to predict its subsequent evolution. He then said that this could no longer be considered to be the case and that ,in another's words "nature does not herself know what comes next"(to paraphrase) Might a reason for this be that no physical systems are identical even in theory? (each system has its own unique place in the overall system) So ,in practice no experimental setup can ever be precisely replicated -and no subsequent evolution of one system can ever be replicated by setting up another identical system and "prodding" it identically to the other. A corollary might be that the mathematics used to describe any physical system is always going to be an approximation to what actually happens (which would be unwelcome "news" to anyone who believed mathematics to be fundamental to physical existence-rather than a very,very useful tool)

Thought the guitar sounded good here too

I see he does Jonny B Goode too....

Thanks. One less misunderstanding is always good (as if a little bit of "decoherence" occurred in my brain,ironically -leading no doubt to further bouts of more informed incoherence* down the road 😉 *for clarity ,I meant "incoherence" in a personal,psychological sense in this particular case 😉

Ah yes,I see it now (your addendum) It is interesting (and something that I think I did pick up on in the Feynman lecture) that you can apparently get a blend of bullet like detections and an overlay of interference pattern on the detection screen. I hope I have that right. It seems like an important clarification (to my previous understanding - which was it was 100% one or the other)

Yes ,I think I had thought of that. Is there any point (I expect this has been done) in having detectors on the barrier with the slits in as well? That way ,if you had one detection at the main detection screen you might also have some multiple at the first barrier alongside the slits? I am not sure what that would add to the scenario but it might show a little more detail possibly.

Down to one photon? And you can't achieve that while maintaining a greater proximity to the slit(s)? I mean ,for simplicity it would be nice to be able to "drop off" a single photon directly in front of slit A so that there would be only the very faintest possibility of it being able to reach slit B (the angle being so tight)

Is that with the 2 slits open? By the way I seem to be being disabused of the idea that it is possible to send one photon at a time.Or is it possible but not relevant at this point or based on the question I asked?(considering one photon at a time might seem simpler if that was possible)

Thanks for your reply. I am reassured that the photons do not have a direction based on the orientation of the apparatus and that they are "free agents" once they emerge from it in front ot the 2 slits and the barrier. (I was,at first scratching my head as to why we can't just point them at one or other of the two slits with a fine accuracy but that was apparently based on an initial misconception) I am still a little unclear as to why high -energy photons would "point better" than low energy ones. Why would one not see them as expanding spheres which end up traveling in the direction of their first interaction? (exactly as low-density photons)

As I am reading ** ,the individual photon (ideally I guess) in the double slit experiment is created from any light source (but ideally a laser) that is pointed at barely translucent material - like darkened glass- so that there emerges at the end a very faint amount of light so that it can be described as (probably?) being a quantum of light or a single photon If the foregoing is more or less correct is it true that the photon in question has emerged from an interaction with the material at the end of the "darkened glass" so that it can be viewed as an expanding sphere of probable locations where it is likely to be detected? In other words ,whilst the initial beam of light at the source was/is pointing more or less in the direction of one or the other slit,the actual photon that emerges from the apparatus is not pointing anywhere (it has no momentum,I think) and instead shoots off in all directions until it is detected either at the wall or somewhere else (even back into the apparatus or maybe missing the screen) So,is it impossible to actually aim a photon at the screen even though the apparatus itself does point in that direction? **I am actually looking at the Feynman lecture (there are 2, I think in Volume 3) on the subject and I don't think he goes into this detail in it.

I think treacle does the same thing (we have tins going back decades since gingerbread is a go to here when it comes to baking)