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sniffnoy...other than "everything, because I don't actually know particle physics". These are just the things that seem really inconsistent or nonsensical to me.
Anything involving spontaneous symmetry breaking:
AIUI, "spontaneous symmetry breaking" (in general, not necessarily related to particle physics) is what happens when you have a probabilistic (or in this case, quantum) system which has a symmetry, which - well, let's imagine that the system starts out in a completely known (or basis) state, which admits some symmetry. The symmetry is preserved as the system evolves. However the symmetry is actually a symmetry of the whole (probabilistic or quantum) state of the system; hence if you follow just one possibility, the symmetry will appear to "break" when something random happens (before then it appeared to be a symmetry of each possible state individually).
OK. So... how does that explain anything? "Symmetry would force all particles would all be massless, but this isn't so due to spontaneous symmetry breaking!" So first off, am I understanding this correctly, that this is saying that particles all used to be massless, but not anymore, and they got their masses randomly? Or just the last part, with time not being involved? Note that this doesn't predict anything about actual particle masses - those remain free parameters in the theory. So why do I care that - if I'm understanding this correctly - there's this symmetry that applies to the multiverse taken as a whole? I mean it's a nice idea but it has no physical relevance, surely? Universes where the very particle masses are different aren't going to interfere with our own, right? They should be pretty damned decohered? How is this actually a physical theory?
The notion of a GUT:
This seems to be the next big goal of particle physics, but I don't see why it's important. OK, at high energy scales EM, strong force, and weak force all behave the same? Great, but what about, low energy scales? Yes, we have a very good idea of what happens at low energy scales, but that's not the point. The point is that I thought the goal here was finding, y'know, the actual laws of physics that apply always (aka "Theory of Everything"). If two (or three) things are the same under some conditions, but not all conditions, then they're not the same thing, there's just special conditions under which they happen to be the same. Under the conditions where they are the same you might get a nice description, but if you're looking for a total description, they're not going to be fundamentally the same, because there are in fact conditions where they aren't the same. (And why does Wikipedia seem to insist that a Theory of Everything should involve unification? That certainly isn't obvious!)
And no, patching together two theories, one for low energy and one for high energy, is almost certainly not going to be the actual laws of physics.
Somehow I suspect the answer to this one is again going to be "spontaneous symmetry breaking", though again I fail to see how that explains anything.
The string theory vacuum problem:
Yes, string theory has a number of problems, I know. But this particular one, I don't see why it's a problem. Remember a while back there was a big thing about "string theory has a zillion different possible vaccums"? How is this any different than just saying "string theory has a shit-ton of free parameters"? So, you do experiments and you fill in those parameters! If string theory is true there will be a consistent assignment, if it isn't there won't. Or do I have it right, and the objection really just was that the huge amount of free parameters made the theory too complicated (not to mention too hard to test)? Certainly having so many free parameters is bad, but what confuses me is that - and I'll admit, maybe I'm misremembering - people seemed to be saying this as if there were more to it than that.
So... anyone want to correct my misconceptions?
-Harry
(So I guess posting is finally working again?)
Anything involving spontaneous symmetry breaking:
AIUI, "spontaneous symmetry breaking" (in general, not necessarily related to particle physics) is what happens when you have a probabilistic (or in this case, quantum) system which has a symmetry, which - well, let's imagine that the system starts out in a completely known (or basis) state, which admits some symmetry. The symmetry is preserved as the system evolves. However the symmetry is actually a symmetry of the whole (probabilistic or quantum) state of the system; hence if you follow just one possibility, the symmetry will appear to "break" when something random happens (before then it appeared to be a symmetry of each possible state individually).
OK. So... how does that explain anything? "Symmetry would force all particles would all be massless, but this isn't so due to spontaneous symmetry breaking!" So first off, am I understanding this correctly, that this is saying that particles all used to be massless, but not anymore, and they got their masses randomly? Or just the last part, with time not being involved? Note that this doesn't predict anything about actual particle masses - those remain free parameters in the theory. So why do I care that - if I'm understanding this correctly - there's this symmetry that applies to the multiverse taken as a whole? I mean it's a nice idea but it has no physical relevance, surely? Universes where the very particle masses are different aren't going to interfere with our own, right? They should be pretty damned decohered? How is this actually a physical theory?
The notion of a GUT:
This seems to be the next big goal of particle physics, but I don't see why it's important. OK, at high energy scales EM, strong force, and weak force all behave the same? Great, but what about, low energy scales? Yes, we have a very good idea of what happens at low energy scales, but that's not the point. The point is that I thought the goal here was finding, y'know, the actual laws of physics that apply always (aka "Theory of Everything"). If two (or three) things are the same under some conditions, but not all conditions, then they're not the same thing, there's just special conditions under which they happen to be the same. Under the conditions where they are the same you might get a nice description, but if you're looking for a total description, they're not going to be fundamentally the same, because there are in fact conditions where they aren't the same. (And why does Wikipedia seem to insist that a Theory of Everything should involve unification? That certainly isn't obvious!)
And no, patching together two theories, one for low energy and one for high energy, is almost certainly not going to be the actual laws of physics.
Somehow I suspect the answer to this one is again going to be "spontaneous symmetry breaking", though again I fail to see how that explains anything.
The string theory vacuum problem:
Yes, string theory has a number of problems, I know. But this particular one, I don't see why it's a problem. Remember a while back there was a big thing about "string theory has a zillion different possible vaccums"? How is this any different than just saying "string theory has a shit-ton of free parameters"? So, you do experiments and you fill in those parameters! If string theory is true there will be a consistent assignment, if it isn't there won't. Or do I have it right, and the objection really just was that the huge amount of free parameters made the theory too complicated (not to mention too hard to test)? Certainly having so many free parameters is bad, but what confuses me is that - and I'll admit, maybe I'm misremembering - people seemed to be saying this as if there were more to it than that.
So... anyone want to correct my misconceptions?
-Harry
(So I guess posting is finally working again?)
