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Bouncing universes and anti matter.

  1. Jul 19, 2011 #1


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    I found this article on anti matter, (far to complex for me to completely understand). what i would like to know is, does this happen at every bounce, or is this (the) start to the universe.

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  3. Jul 19, 2011 #2


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    May be i have not worded this question in a proper way. what i want to know is , if the universe has gone through several bounces would antimatter become less after every bounce .
  4. Jul 19, 2011 #3


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    Wolram, it's a reasonable question. I don't know the answer. But even before we can ask your question (regarding some particular bounce model), we have to ask would any matter get through a bounce----any at all?

    In some particular bounce cosmology model it might be that all the usual forms of matter are destroyed and, say, only light---only very high energy photons---emerge right after the bounce.

    Because newcomers might be reading this thread, we should be sure to mention that no bounce cosmo model has been proven. There is growing interest in them---they are increasingly studied---it appears possible to derive testable predictions---but the tests have not been performed (essentially because new instruments would have to placed in orbit.)

    So the question being asked here is hypothetical: assuming some particular bounce cosmology is right (for definiteness say LQC) what are the first energy fields to appear after the bounce, what quantum fields besides the gravitational field itsef?

    I think that is very much in the realm of "new physics". It is a fascinating question. Some people conjecture that the first offspring from the bounce would be a "scalar field" of the sort called an "inflaton". (Inflation scenarios are based on that assumption.)
    You only get particles and antiparticles when the "inflaton" field decays and self-destructs, giving up its energy. No scalar field has ever been observed. AFAIK the standard model of particle physics has no place in it for such a field. The standard model would have to be enlarged, to encompass something like an "inflaton" and predict its properties.

    So it's best to be humble and patient, in the face of major gaps in human knowledge like this. Try to realize how much we don't know.

    But we do know that there are no "anti-photons". Or if you like, a photon of light is its own anti-particle. So that gives us a simple way of imagining the U right after the bounce. It could be nothing but expanding geometry and glorious intense light. So no antiparticles---they come a tiny fraction of a second later after the geometry has expanded some and the light has had a chance to cool down a little. This is just a simplified way of picturing---it is conjectural (so please don't hold me to it :biggrin:)
  5. Jul 20, 2011 #4


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    Gravitons have no antiparticle equivalent, so it is difficult to construct a bounce model that works under physics as currently known. Under inflation, gravity is repulsive in the very early universe making it possible for an infinite rate of expansion for a very, very brief period of time. This would imply the universe is dead flat after inflation, which is not unreasonable given current observational data. A slight curvature remains a definite possibility and, given nature abhors infinities, suggests the early universe expanded at an enormous, albeit finite rate.
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