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String Energy

  1. Sep 2, 2005 #1
    In special relativity we say that a particle travelling at the speed of light uses all its energy to do so and thus has no energy for anything else. ie (movement through time) This begs the question; what is giving the string the energy to vibrate? Or does its maximum vibration equate the speed of light? If we could find a unified theory that proves the existance of strings would these questions be valid? I may be stupid, but one can always learn.
  2. jcsd
  3. Sep 2, 2005 #2
    Where did you hear this? A particle travelling at c can have any energy, but can have no mass. (E=pc)

    I think that this is a bad interpretation of the physics involved. One can not assign a co-moving reference frame to a particle at c, as c must always be c from every frame. Hence, no proper time can be defined (proper time is time as seen from a certain reference frame). This is not due to lack of energy.

    Strings are quantum objects, and as such classical physical concepts of energy don't apply to them. Energy becomes an operator (as does anything we can observe*), which is applied to a quantum state. It's corresponding so-called eigenvalues are what we measure as energy, which are quantisized. This means that they can only appear as products with integers. (e.g, you could have an energy of 123.3 Mev and 154.13 MeV but not anything in between). An interesting consequence of this is that a quantum system has a minimum non-zero energy. So strings have some 'vacuum state'. (EDIT: Not to be confused with the ground state, which is the minimum energy in typical quantum mechanics). They can also gain and lose energy through various interactions. These interactions are governed by the laws of quantum field theory.

    *A very important concept in quantum physics :smile:

    I don't think I understand the question. Vibration is not a physical quantity, by itself. We could define frequency, for instance. But not compare it to speed. If your question really means "does the speed of light 'barrier' apply to strings", then the answer is yes.
    Last edited: Sep 2, 2005
  4. Sep 5, 2005 #3
    I had a question about vritual paticles or vacuum fluctuation.
    if this means that matter ( paticle and anti-particle pairs) is created from " nothing" ?
  5. Jun 18, 2011 #4
    Is it possible that string energy could ever be visible. Not by the naked eye, but by a camera
  6. Jun 21, 2011 #5
    or.... why is a string composed of energy?

    Nobody knows...nobody knows what a string is...we just say it's vibrational modes of energy. Nobody knows what "mass" nor gravity nor "time" is either....the best we can do is describe some of their observed behaviors and hopefully make some testable predictions.
  7. Jul 16, 2011 #6
    Have I misunderstood something?

    A string is a line along which a particle can vibrate. No particle has rest mass, but the string as a whole can obtain mass if the particle is vibrating at the speed of light, given by hf/c^2 where h=planck length, f=frequency, c=speed of light. The string for a photon does not have mass, therefore vibrations on the photon string are slower than light.
  8. Jul 17, 2011 #7
    Correction: Strings vibrate in more than one dimension, therefore the mass should be the sum of hf/c^2 for all frequencies f for vibration in each dimension.
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