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M-theory question

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There is a proposed scenario call the ekpyrotic theory in which the universe was created has it's origins in by two branes colliding [1].


I would not say that it is really an alternative to the big bang theory as such because the evolution of the universe shortly after is just the Lambda-CDM model. It gives a mechanism for the origin of the big bang.



[1] Khoury, Justin; Burt A. Ovrut, Paul J. Steinhardt, Neil Turok (28 Nov 2001). "Ekpyrotic universe: Colliding branes and the origin of the hot big bang". Phys. Rev. D (American Physical Society) 64 (12)

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Can the collision of two branes create a Big Bang ? How ?:confused:


Have a look at the reference I have given you.


Steinhardt from Princeton University has written a short introduction see here.


The basic idea is that our universe was created from the collision of two three branes. The branes stick together and the kinetic energy of the collision is transformed into the particles like electrons, quarks and photons that are fixed on the resulting three brane. The universe then evolves like the standard model of cosmology. Energetically, a flat geometry is preferred and this is what we see. Also, the temperate is all finite so no infinities at the origin of the big bang. Moreover, the temperate could be low enough so that massive monopoles are not created.


Quantum fluctuations of the three branes could also explain the CMBR anisotropies and galaxy seeding. (Though this seems very well explained in the Lambda CDM model.)


I am not sure what the feeling today exactly is with this model. I know there was a lot of interest at one time. Maybe someone else here knows more about this?

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Lots of heavy monopoles should have been created in the early universe, according to the "traditional" big bang. These are simply not seen.


So, either they were not created for some reason, maybe the ekpyrotic universe answers this or they were created but then "diluted" as in inflationary models. Or maybe something else?

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No, it cannot since currently m=11 and our universe is 3-dimensional. We need a better m-theory - with m=3. :eyebrow:


That's where the branes and/or compactification come into the story.

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If movement occurrs during the collison of branes doesn't this mean time passes in the bulk space?


In essence yes. Time is taken as a dimension in the bulk. But I don't see this as a problem.


The "p" in p-brane refers to the "spacial dimensions" as a p-brane sweeps out a (p+1) dimensional world volume.

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