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Theorem between Curvature and submanifolds

  1. Jan 7, 2004 #1
    I wonder if there are any theorems between changing curvature of some overall manifold and the equivalence of this to the creation of submanifolds.

    It seems to me that this would be the missing link between the expanding universe of GR and the particles of String Theory. Perhaps this is also a type of symmetry breaking process.

    Any comments or observations out there?

    Thanks.
     
  2. jcsd
  3. Jan 7, 2004 #2
    what do you mean by "changing"? remember that in GR, time is part of the manifold, so there is no way to say the curvature changes in time in a consistent way.


    the link between string theory and GR is not missing, it is well known: String theory contains GR as a first order approximation.

    which symmetry did you have in mind to be broken, and what does this have to do with String theory, GR, submanifolds, or changing curvature?
     
  4. Jan 7, 2004 #3
    Re: Re: Theorem between Curvature and submanifolds

    I was refering to the "expansion" of the universe, how the volume of space is increasing with time. This is sometimes described as the "unwinding" of a curled up dimension. And this gives rise to the idea of a curvature of space dimensions changing with time as it uncurls.


    This sounds like a start. But is it fair to say which one include the other? And is both SR and GR "included"? And are higher order branes also included in this relationship?

    Strings and the world-sheets thereof are submanifolds of the overall space-time. The more partilces/strings, the more mass density and the greater the curvature of spacetime. So this does sound like the start of a relationship between the curvature of something and the existence of submanifolds.



    Don't know, really. But once you distinguish regions (as you do when you have submanifolds "somewhere" with respect to others) , then you can no longer say that every place is equivalent to any other.
     
  5. Jan 8, 2004 #4
    Re: Re: Re: Theorem between Curvature and submanifolds

    the spatial curvature can be constant in an expanding universe. for example, it can be zero.



    it is certainly fair to say that string theory contains GR. like i said, string theory predicts einsteins field equation as a first order approximation.

    on the other hand, GR does not contain string theory. in fact, up until the seventies, string theory was unknown, and yet GR had existed for many decades.

    as far as special relativity is concerned, string theory contains that as well, but unlike general relativity, special relativity is put in by hand in string theory.

    i don t think branes have anything to do with this question.

    strings and worldsheets are submanifolds of spacetime, i agree.

    i don t see any straightforward relationship between number of submanifolds and curvature.


    R3 has infinitely many submanifolds. this does not imply that any region of R3 is somehow special.
     
  6. Jan 8, 2004 #5
    Re: Re: Re: Re: Theorem between Curvature and submanifolds

    The reason I ask such questions is that it would seem that at the most
    fundamental beginnings of the universe, we have both the expansion of the
    universe (a manifold) and the creation of particles (submanifolds of the
    univserse) that do not get any larger with time. This would seem to occur at
    the very first instant at the starting point of very small size, possibly
    even a single point. If this is not arbitrary, then it would seem that there
    must be some connection between expansion and particle creation. The
    question I have is if expansion gives particles, then was their ever an
    expansion of space time without particles, the expansion of the one and only
    "God" particle? It may be that multiple particles existed from the start. Or
    perhaps due to some quantum mechanical effect, there may have been only one
    particle to begin with, the "universal" particle, which latter fractured
    into many.



    I suppose you'd have to have forces between particle (between these
    submanifolds) before invariance with place is destroyed, hey?
     
  7. Jan 8, 2004 #6
    i have pretty much no idea what you are talking about.
     
  8. Jan 8, 2004 #7
    Isn't String Theory itself a description of how manifolds emerge from other manifolds and then join, since they describe the interaction of world-sheets which are manifolds? Isn't M-theory a study of how lower dimensional submanifold (strings) emerge from higher dimensional manifolds (membranes)? Perhaps M-theory itself is the theorem I'm looking for. Or perhaps the theorem I'm looking for would be the non-perturbative form of M-theory we would all like to see.

    My earlier point was that if two different things are true in conjunction at the same place at the same time (as they would have to be at the singularity from which the big bang occured), then this implies that one proves the other so that there is an equality between them. So the question is whether the universe begins with both particle creation (emergence of submanifolds) and universal expansion simultaneously, or whether we could have expansion without particle creation.
     
  9. Jan 9, 2004 #8
    no.

    i don t know M=theory, but this description doesn t sound accurate to me.

    M-theory is not a theorem

    yeah, perhaps.

    conjunction? what does that mean? this is starting to sound like astrology.

    as far as i know, particle creation has nothing to do with expansion, and even a classical universe with a constant number of particles will undergo expansion.
     
  10. Jan 9, 2004 #9
    Originally posted by Mike2
    Isn't String Theory itself a description of how manifolds emerge from other manifolds and then join

    Is that because the splitting and joining of world-sheets is itself all only one manifold with holes in it, and not creating separate manifolds?

    I'm refering to logical conjunction of two propostions held to be true. Consider the following statements of propositional calculus:
    (The symbol "[tex] \to [/tex]" stands for material implication, and "[tex]\cdot[/tex]" symbolized conjunction.)

    [tex]
    (p \cdot s) \to (p \to s)
    [/tex]

    and by symmetry:

    [tex]
    (p \cdot s) \to (s \to p)
    [/tex]

    Together they prove:

    [tex]
    (s \to p) \cdot (p \to s) = (p=s)
    [/tex]

    It seems obvious that particle creations imply expansion since we could not distinquish one particle from another unless they are separated in space which must expand in order for that distinction to exist.

    And the expansion of any manifold from nothing implies at least the existence of one particle, the particle described by that initial manifold that expands.

    So perhaps it's not such a great leap to conjecture that it is a general truth that the expansion of one manifold is equal to the creation of submanifolds.
     
  11. Jan 27, 2004 #10
    Re: Re: Re: Re: Re: Theorem between Curvature and submanifolds

    For example, here's a thought I'm considering; maybe there is some study of this in the literature somewhere: We have for each instant of time the overall manifold of reality that changes from the previous moment. There is a hypersurface that marks the initial and final state from one time to the next. That hypesurface is one less dimensionality of the origional manifold. But if we consider the time interval as a whole, and make no distinction between one instance of time and another in that interval, then we might consider there to be an infinite number of alternative paths from initial to finial state each of which contributes to a final result. And this would give a Feynman path formulation for the propogation of the hypersurface. Thus the expansion of an overall manifold creates the propogation of submanifolds (interpreted as particles). This is a pretty rough sketch. Do you think it has any merit?
     
  12. Jan 27, 2004 #11
    what you are describing sounds a little like the concept of a cobordism. perhaps you should look into that theory. it is formulated in the language of category theory.

    you can read a little about them in Baez' seminar on Topological Quantum Field Theory here
     
  13. Jan 27, 2004 #12
    Thanks for that link. Yes it does sound like a cobordism.
     
  14. Jan 27, 2004 #13
    Re: Re: Re: Re: Re: Re: Theorem between Curvature and submanifolds

    So what is this result that considers every possible "path"? Is this like saying that a space is equivalent to every possible path through it? Is this some way of considering the entire space?
     
  15. Feb 1, 2004 #14
    Re: Re: Re: Re: Re: Theorem between Curvature and submanifolds

    Now I wonder if there is not some relationship between particle (submanifold) creation and entropy. Or whether there is not some equivalence between a decrease in entropy and the creation of some submanifold. For it would seem that the creation of a submanifold where before it was not would have to represent some increase of order in the universe. The order, or decrease in entropy, being stored in the constant characteristics of the submanifold.

    Entropy is not necessarily a purely physical phenominon and can be used in association with probabilities in general.

    For example, if the information (Shannon information) of the entire universe as a whole cannot change, then as the universe expands, there becomes more possible states, and the entropy of the universe would increase unless some process also produces states of lower entropy to compensate. Just speculating, any thoughts?
     
    Last edited: Feb 1, 2004
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