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Space-time in string theory

  1. Nov 13, 2008 #1
    Does string theory state that space-time is made of strings? And if so, how can "empty space" be made of strings if string theory says that a single string is a particle?

    Also, would space-time being made of strings be an explanation as to why it behaves so erratically at very tiny scales?

    Can anyone help?

  2. jcsd
  3. Nov 14, 2008 #2


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    This is actually an excellent question!

    The usual formulation of string theory ASSUMES that spacetime exists even without the strings. From that assumption the theory implies the existence of gravitons propagating through spacetime. Strictly speaking, that's all that string theory can say regarding your question.

    However, the experience from non-string theory of gravitons suggests (but in no way proves) that the existence of gravitons means that spacetime itself is also a dynamical entity. But if this is the case, then strings themselves are actually not the basic fundamental entities. Instead, the truly fundamental entity should be string-field (generalizing the notion of the gravitational field) or something even more abstract, but nobody knows yet what exactly this would be.
  4. Nov 16, 2008 #3
    Thank you, understood.
  5. Mar 5, 2009 #4
    This newbie got here via a search of the term "unlimited entity"

    Has anyone explored the assumption that there is an unlimited entity, that is, really taking a serious run at it?

    If there were more than one unlimited entity, each would be limited by the other, therefore there can be only one. Unlimited in all aspects, it would have to be both infinitely large and infinitely small, infinitely "fast" and infinitely "slow" and must include all reality. Sounds counter-intuitive, but what isn't in current cosmology?

    A barrier to exploration most people are unlikely to pay attention to is that the imaging capacity of the human brain is limited, and all the transducers we use to measure anything are likewise limited. To assume the human brain can image everything of reality, even with our impressive sets of symbolic operations and technology, is arrogant. However, if there were an unlimited entity, its local operation must be evident in all human experience of reality. A few thoughts:

    Obviously strange in our mental imaging capacity, an unlimited entity would have to traverse every infinitely small point in unlimited "space" in the instant of the present moment. Also strange to us, between two infinitely small points infinitely close from our mental perspective, there is an infinite number of infinitely small points.

    As a single entity, the unlimited cannot traverse the same infinitely small point twice in the same iteration. To avoid "hitting" itself, it must change trajectory by an infinitely small amount. Best bet for the single principle of its operation (there must be only one) is the simplest possible set of operations, together and apart.

    A mathematical definition of "strings" of unlimited length would be a nice metaphor, but complicated. It's easier and more fun to mentally play with the possibility of an unlimited entity using ordinary (local and limited) three dimensional coordinates and sequences of events (together and apart).

    There is only one way an unlimited entity can randomly generate three classes of waves and subclasses (try thinking process ether or activity matrix). Try parallel waves (opposite paths in a sequence of iterations) which go straight. Infinitely close to parallel waves but non parallel (same opposite paths in a sequence of iterations) but travel a helical path and can become a stable pattern if they happen to link head to tail. Waves of infinitely close to right angle interaction during a single iteration (twisting circular path and two subclasses) can also link head to tail by chance as a standing configuration and with prodigious size variation with interaction of three passes of the unlimited. These bigger hummers stay put in the instant of the present moment, and the way they evolve by hooking up together and randomly changing partners will show you lots about a lot of things.

    And oh yeah, random recombination (together and apart) proceeds toward the maximum ratio of interrelated operations to the total number of operations in the system.

    If you do it right, you can show how all these waves can come together and apart and evolve the familiar patterns and do the same thing with any arbitrary local coordinates.

    Go for it guys. It won't fry your brain and somebody has to figure out the details:wink:

    Last edited: Mar 5, 2009
  6. Mar 7, 2009 #5
    M theory and it's constituent string theories utiize a fixed spacetime background...meaning the spacetime is chosen first, then the string theories are developed....it is a major failing of string theory as formulated so far. In addition those theories showed either a negative or zero cosmological constant in conflict with apparent observations of an accelerating universe.

    For a more recent string theory based approach, see my thread just posted: Emergent String Based Spacetime...no math, just concepts...


    It's still speculative, but offers considerable insights on how small dimensions might be stabilized and how a positive cosmological constant can be formulated....

    Trying to determine just how space time emerges from "nothing", perhaps the vacuum of space, perhaps via singularities, is a major challange for theoretical physics of all stripes...string theory, quantum mechanics, and so on...
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