4 ms·

Non-locality can't be right though, since locality is defined by the speed of light, and nobody will tell you that sending information faster than the speed of

Non-locality can't be right though, since locality is defined by the speed of light, and nobody will tell you that sending information faster than the speed of light is possible. Many worlds it is, then.

M_Grey 10y ago
Non-locality doesn't imply that you can transmit information FTL, in fact you can't without classical channels. You can send random bits with entangled particles, but that is the precise opposite of information.
wyager 10y ago
Many worlds isn't the only alternative. The "cleanest" (i.e. least magical) proposed solution I know of is einselection, which gives us emergent behavior of the schroedinger equation that looks kind of like many worlds and kind of like "ideal" non-unitary collapse, but doesn't posit any "unobservable" or "magical" processes unlike many worlds or Copenhagen.
- jostylr 10y ago
  You have to be clear about what is real in the theory. Many worlds presentations often suffer from this as they often talk about splitting universes, whatever that would mean. A nice version which might coincide with what is in mind for einselection is to take the wave function and integrate it out to get a mass density on three space. This mass density will the various different "worlds" present in it by means of the evolution; any given time will not tell us what belongs to which world, but as time evolves, we can see which pictures correspond to which ones, like fuzzy tv sets. See https://arxiv.org/pdf/0903.2211.pdf https://arxiv.org/pdf/0903.2211.pdf
  - M_Grey 10y ago
    There isn't much to recommend any of the many 'Interpretations' of QM, and if you deal with people involved in using it for their jobs, they tend to adhere to a "shut up and calculate" interpretation. After all, why construct an ontology based on what is clearly not complete at all energy scales? Still, where there are gaps, people will "theorize".
    - jostylr 10y ago
      It is all a matter of what you want out of science. Some people, such as myself, enjoy having a narrative about how the universe works consistent with experiments. This is both satisfying and useful in finding new directions to push or ways to solve problems (such as a recent attempt to solve the divergences in QFT by using boundary conditions appropriate for particle flows: https://arxiv.org/pdf/1506.00497.pdf https://arxiv.org/pdf/1506.00497.pdf). If you have just quantities to compute, but have no idea what those quantities represent in reality, it is hard to see how one can think of that as understanding how the universe works. It is not clear why having a "complete" theory would change one's position on ontology. It is either important or it is not to a person, just as some people love playing with big machinery and only care about models in as far as it enables them to do that. Others really do not care about big machinery except as it produces potential data to suggest new models or discard the old. Why should one make a judgement about that?
      - M_Grey 10y ago
        If what you want out of science is a narrative with no clear basis in reality, why bother with science?
        jostylr 10y ago
        It certainly has a basis in reality. The story needs to be consistent with what we know, at least in the realm that it claims to give sense to. Science is not about getting the absolute truth, it is about getting information and a story consistent with what we know to be true, often with caveats about where the story applies. And, of course, you can deny ontology all you like, but everyone operates with one in their mind. It is impossible to do interact with reality and to use equations without some internal assumption of an ontology, however vague and unexamined it might be. It is just that the "shut up and calculate" crowd does not want to discuss it, much like how "very religious" people often do not want to talk about their religion. They are simply not interested in examining stuff that may challenge their world views. But it doesn't mean they don't have an underlying belief. It is similar to, paraphrasing Bell, how solipists buy life insurance. The real point of science is to question our assumptions and obtain a better understanding, often contradicting what we thought was true. In order to do that, one has to look at what one believes is true. This is what the investigation of different ontologies is doing. But, as I said, many are not interested in pursuing that line of thinking and that's fine. But it is not fine to say it should not be pursued at all or to imply it is less important or noble. Different aspects of understanding should be pursued by those who find those aspects enjoyable to pursue.
jostylr 10y ago
The tension is not with FTL, but rather with the tension of a seeming need in QM for "now" and that in relativity of "not now". There are a number of ways to work in a "now" in a way compatible with the mathematics of relativity. For a full exploration of these ideas, one can see https://arxiv.org/pdf/1307.1714.pdf https://arxiv.org/pdf/1307.1714.pdf which explores ways that the wave function itself possesses multiple possibilities of extracting a "now". To what extent those "now"s are acceptable is certainly open to much debate.

M_Grey 10y ago

Non-locality doesn't imply that you can transmit information FTL, in fact you can't without classical channels. You can send random bits with entangled particles, but that is the precise opposite of information.

wyager 10y ago

Many worlds isn't the only alternative. The "cleanest" (i.e. least magical) proposed solution I know of is einselection, which gives us emergent behavior of the schroedinger equation that looks kind of like many worlds and kind of like "ideal" non-unitary collapse, but doesn't posit any "unobservable" or "magical" processes unlike many worlds or Copenhagen.

jostylr 10y ago
You have to be clear about what is real in the theory. Many worlds presentations often suffer from this as they often talk about splitting universes, whatever that would mean. A nice version which might coincide with what is in mind for einselection is to take the wave function and integrate it out to get a mass density on three space. This mass density will the various different "worlds" present in it by means of the evolution; any given time will not tell us what belongs to which world, but as time evolves, we can see which pictures correspond to which ones, like fuzzy tv sets. See https://arxiv.org/pdf/0903.2211.pdf https://arxiv.org/pdf/0903.2211.pdf
- M_Grey 10y ago
  There isn't much to recommend any of the many 'Interpretations' of QM, and if you deal with people involved in using it for their jobs, they tend to adhere to a "shut up and calculate" interpretation. After all, why construct an ontology based on what is clearly not complete at all energy scales? Still, where there are gaps, people will "theorize".
  - jostylr 10y ago
    It is all a matter of what you want out of science. Some people, such as myself, enjoy having a narrative about how the universe works consistent with experiments. This is both satisfying and useful in finding new directions to push or ways to solve problems (such as a recent attempt to solve the divergences in QFT by using boundary conditions appropriate for particle flows: https://arxiv.org/pdf/1506.00497.pdf https://arxiv.org/pdf/1506.00497.pdf). If you have just quantities to compute, but have no idea what those quantities represent in reality, it is hard to see how one can think of that as understanding how the universe works. It is not clear why having a "complete" theory would change one's position on ontology. It is either important or it is not to a person, just as some people love playing with big machinery and only care about models in as far as it enables them to do that. Others really do not care about big machinery except as it produces potential data to suggest new models or discard the old. Why should one make a judgement about that?
    - M_Grey 10y ago
      If what you want out of science is a narrative with no clear basis in reality, why bother with science?
      - jostylr 10y ago
        It certainly has a basis in reality. The story needs to be consistent with what we know, at least in the realm that it claims to give sense to. Science is not about getting the absolute truth, it is about getting information and a story consistent with what we know to be true, often with caveats about where the story applies. And, of course, you can deny ontology all you like, but everyone operates with one in their mind. It is impossible to do interact with reality and to use equations without some internal assumption of an ontology, however vague and unexamined it might be. It is just that the "shut up and calculate" crowd does not want to discuss it, much like how "very religious" people often do not want to talk about their religion. They are simply not interested in examining stuff that may challenge their world views. But it doesn't mean they don't have an underlying belief. It is similar to, paraphrasing Bell, how solipists buy life insurance. The real point of science is to question our assumptions and obtain a better understanding, often contradicting what we thought was true. In order to do that, one has to look at what one believes is true. This is what the investigation of different ontologies is doing. But, as I said, many are not interested in pursuing that line of thinking and that's fine. But it is not fine to say it should not be pursued at all or to imply it is less important or noble. Different aspects of understanding should be pursued by those who find those aspects enjoyable to pursue.

jostylr 10y ago

The tension is not with FTL, but rather with the tension of a seeming need in QM for "now" and that in relativity of "not now". There are a number of ways to work in a "now" in a way compatible with the mathematics of relativity. For a full exploration of these ideas, one can see https://arxiv.org/pdf/1307.1714.pdf https://arxiv.org/pdf/1307.1714.pdf which explores ways that the wave function itself possesses multiple possibilities of extracting a "now". To what extent those "now"s are acceptable is certainly open to much debate.