No symmetries in the Universe at the Big Bang...?

[Suekdccia]

TL;DR Summary

No symmetries in the universe at the Big Bang...?

I apologize in advance if this is a stupid question but...

According to some scenarios about the beginning of the universe (namely cosmological inflation), in layman's terms, everything was born out of a quantum fluctuation which caused a violent expansion. In this case, since an expanding universe breaks the time translation symmetry, energy conservation does not necessarily hold and therefore energy and matter could have appeared from """nowhere""" ()

However, if these conditions were "repeated" in a spacetime with no (global) symmetries, could all conservation laws and the rest fundamental laws of physics have been also violated or approximate? Would this be theoretically possible?

 

[PeterDonis]

According to some scenarios about the beginning of the universe (namely cosmological inflation), in layman's terms, everything was born out of a quantum fluctuation which caused a violent expansion.

Actually not all inflation models say that. The common feature that all inflation models have is that the "Big Bang" state--the hot, dense, rapidly expanding state that is the earliest state of the universe for which we have good evidence--happened because inflationary expansion ended when the inflaton field (the scalar field driving inflationary expansion) went through a phase transition from a "false vacuum" state to a "true vacuum" state and transferred all of its energy density to the Standard Model fields.

Where inflation models differ is on how the inflationary expansion came about. The original inflation models assumed that inflationary expansion was triggered by some event (possibly a previous phase transition, for example from some kind of Planck scale physics). However, the main front runner inflation models today appear to be "eternal inflation" models, in which inflationary expansion extends infinitely far back into the past--it never starts and there is no state previous to it. Universes like ours get "born" when a fluctuation causes inflation to stop via the phase transition from "false vacuum" to "true vacuum" described above.

since an expanding universe breaks the time translation symmetry, energy conservation does not necessarily hold and therefore energy and matter could have appeared from """nowhere"""

This is a fairly common statement in pop science videos, even by experts like Guth, but you have to be careful about what it means. The inflaton field in its "false vacuum" state, i.e., while inflation is going on, works like dark energy: its energy density is constant everywhere in the inflating region of spacetime. If we look at successive spacelike slices in FRW coordinates with increasing scale factor, this looks like inflaton field energy is continuously being "created from nothing". But, as you will see if you read, for example, Carroll's classic blog post "Energy Is Not Conserved", that's not the only possible interpretation. What is true on any interpretation is that, as you say, there is no time translation symmetry in an expanding universe, and therefore there is no globally conserved energy.

if these conditions were "repeated" in a spacetime with no (global) symmetries, could all conservation laws and the rest fundamental laws of physics have been also violated or approximate? Would this be theoretically possible?

We have no idea since nobody has proposed any model along these lines. It's pointless to ask what is "possible" if you throw out all constraints.

 

[Suekdccia]

We have no idea since nobody has proposed any model along these lines. It's pointless to ask what is "possible" if you throw out all constraints.

Even if it has not been proposed, would inflation occurring in a spacetime that lacks all (global) symmetries mean that all laws associated with these symmetries would be violated in the formation of the universe?

 

[Drakkith]

Even if it has not been proposed, would inflation occurring in a spacetime that lacks all (global) symmetries mean that all laws associated with these symmetries would be violated in the formation of the universe?

If the laws require symmetry, then without that symmetry existing the laws wouldn't appear to apply. So there's not really any violation that could even occur since the laws wouldn't apply in the first place.

 

[Suekdccia]

If the laws require symmetry, then without that symmetry existing the laws wouldn't appear to apply. So there's not really any violation that could even occur since the laws wouldn't apply in the first place.

Well, that makes sense

 

[PeterDonis]

Even if it has not been proposed

The question is pointless if it is about a model that nobody has proposed and does not exist. How can anyone possibly say anything about a model that does not exist?