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

In summary, some scenarios suggest that the beginning of the universe was caused by a quantum fluctuation and violent expansion, but not all models agree on this. Inflation models explain the expansion as a result of the inflaton field going through a phase transition. There is no time translation symmetry in an expanding universe, meaning that energy conservation may not hold and energy and matter could appear from nowhere. However, it is unclear what would happen if these conditions were repeated in a spacetime with no global symmetries. This is because no models have been proposed in this scenario and it is pointless to speculate on the possibilities without any constraints.
  • #1
Suekdccia
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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?
 
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  • #2
Suekdccia said:
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.

Suekdccia said:
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.

Suekdccia said:
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.
 
  • #3
PeterDonis said:
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?
 
  • #4
Suekdccia said:
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.
 
  • #5
Drakkith said:
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 :smile:
 
  • #6
Suekdccia said:
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?
 

1. What are symmetries in the Universe at the Big Bang?

Symmetries in the Universe at the Big Bang refer to the uniformity and balance of physical laws and properties at the moment of the Universe's creation. This includes the distribution of matter and energy, the strength of fundamental forces, and the overall structure of the Universe.

2. Why are there no symmetries in the Universe at the Big Bang?

The lack of symmetries in the Universe at the Big Bang is due to the rapid expansion and cooling of the Universe during the initial moments after the Big Bang. This expansion caused the Universe to become less uniform and more chaotic, breaking the initial symmetries present at the moment of creation.

3. How do scientists study the symmetries in the Universe at the Big Bang?

Scientists study the symmetries in the Universe at the Big Bang through various methods, including observations of cosmic microwave background radiation, measurements of the distribution of matter and energy in the Universe, and simulations using advanced computer models.

4. What implications do the lack of symmetries in the Universe at the Big Bang have?

The lack of symmetries in the Universe at the Big Bang has significant implications for our understanding of the Universe's evolution and the laws of physics. It suggests that the Universe is not completely uniform and that there may be unknown forces or phenomena that played a role in the early stages of the Universe's development.

5. Could there have been symmetries in the Universe at the Big Bang that we have yet to discover?

Yes, it is possible that there were symmetries in the Universe at the Big Bang that we have yet to discover. As our technology and understanding of the Universe continue to advance, we may uncover new evidence or theories that shed light on the initial conditions of the Universe and the presence of symmetries at the Big Bang.

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