God and the Multiverse: Humanity's Expending View of the Cosmos by Victor J. Stenger

Author:Victor J. Stenger [Stenger, Victor J.]
Language: eng
Format: epub
ISBN: 9781616149703
Barnesnoble:
Goodreads: 20299767
Publisher: Prometheus Books
Published: 2014-08-19T05:00:00+00:00

THE GUT PHASE TRANSITION

Given the success of the standard model, we can reasonably assume that prior to the electroweak phase transition at a presently estimated 173 GeV in temperature, which occurred at about 10–11 second, the universe can be described by the standard model with electroweak unification. That is, the strong force is still distinct but electromagnetism and the weak force are unified. The universe at this time still consisted of the quarks, leptons, and gauge bosons in table 11.1, but they were all massless and there were no Higgs bosons. Particles still outnumbered antiparticles by a billion to one. At some higher energy and earlier time, there almost certainly had to be a phase transition from a state of higher symmetry that, itself, was the result of a phase transition from an even higher symmetric state.

The best candidate remains some kind of GUT in which the strong and electroweak forces are united and both baryon- and lepton-number conservation are violated. This GUT, in turn, arose from another symmetry at higher energy in which B and L were conserved.

Most GUTs that have been proposed exhibit these properties. Here the symmetry is manifested by no distinction being made between quarks and leptons so that reactions such as those shown in figure 11.4 can take place. The X particle that is exchanged in the figure can be thought of as a “leptoquark,” a combination of quark and lepton. The breaking of B and L come about, according to Sakharov, by differences in reaction rates caused by CP violation.

In the more symmetric state prior to the GUT phase transition, CP is invariant and B and L conservation are each restored. So the universe starts out with all the symmetries and equal numbers of particles and antiparticles. The asymmetry of matter and antimatter is generated after the phase transition from this earlier state to the GUT state.

So all we have to do is keep building more and more powerful colliding-beam accelerators so that we can keep probing farther and farther back in time until we reach the GUT regime. The trouble is, we aren’t even close to having enough energy. The GUT phase transition is estimated to occur at about 1025 eV, twelve orders of magnitude above the energy of the LHC. A vast “desert” may exist between the GUT and electroweak phase transitions, during which time the universe remains in the unbroken phase of the electroweak-unified state.

At least the LHC will enable us to explore the unbroken phase. But will we ever be able to probe beyond this state? It is highly unlikely with accelerators, at least in any foreseeable future. However, we do have another window on the very early universe, and that is proton decay. Super-K may be nearing the point where proton decay is observed. Several GUTs predict decay modes that are within the range of Super-K or a larger detector.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.