Vacuum energy density after inflation

[windy miller]

Its said that if there are different pocket universes made by inflation then this solves the alleged fine tuning of dark energy. My question is this: can the idea of different values for the vacuum energy density in these different pockets be derived from quantum field theory or does it need something more exotic like string theory?

 

[Chronos]

Multiverse to the rescue again! It's the undisputed king of patent medicine curing everything from initial conditions to fine tuning, anthropism, the values of dimensionless constants and even falsification of TOE's..

 

[Haelfix]

My question is this: can the idea of different values for the vacuum energy density in these different pockets be derived from quantum field theory or does it need something more exotic like string theory?

Field theory alone. All you need is a fundamental scalar with a metastable potential, which undergoes vacuum decay. The ensuing physics could (depending on the details of the new ground state) have radically different properties.

 

[windy miller]

Field theory alone. All you need is a fundamental scalar with a metastable potential, which undergoes vacuum decay. The ensuing physics could (depending on the details of the new ground state) have radically different properties.

Thanks, and those radically different properties you mention would they apply to just the vacuum energy density or to other values in physics? I believe that things like the masses of would only differ from pocket universe to pocket universe if string theory or something like it were true. Is that correct or incorrect?

 

[Haelfix]

In principle after vacuum decay, the behaviour of many of the constants in nature could be altered. It's a tiny bit involved, but a fundamental scalar could couple, almost like the interaction of the Higgs field does. The latter contributes to both gauge bosons, as well as fermions, so many properties of the surrounding universe would be radically different, depending on the details of the new vacuum.

String theory is something else, although a similar mechanism could exist within that framework as well. Many of the stringy models produce lots of new scalar fields (called Moduli), and the same sort of thing in principle could happen there.

The sketch of the phenomenon is really quite simple to describe mathematically, and similar things happen all over physics (for instance in condensed matter systems undergoing phase transitions) which is why its not completely crazy, and the details are very closely tied in with the mathematics of inflation.