Exponential expansion and Higgs mechanism

In summary: Well, it has to do with the details of General Relativity. There are a couple of ways of looking at it, but if there exists some matter that grows in energy density with time, then that matter has pressure that is both negative and greater in magnitude than its matter density. This large negative pressure leads to a negative mass density for some... well, let's just say that it's not the most conventional kind of matter.
  • #1
lark
163
0
Our universe apparently has a positive cosmological constant so it will look more and more like de Sitter spacetime, expanding at at exponentially increasing rate.
So eventually it seems that subatomic spacetime would be affected by this. Eventually even something a Planck distance away would be outside a particle's event horizon.
I wonder if this would tear the Higgs mechanism to pieces …
Laura
 
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  • #2
lark said:
Our universe apparently has a positive cosmological constant so it will look more and more like de Sitter spacetime, expanding at at exponentially increasing rate.
So eventually it seems that subatomic spacetime would be affected by this. Eventually even something a Planck distance away would be outside a particle's event horizon.
I wonder if this would tear the Higgs mechanism to pieces …
Laura
Nah, in order for subatomic interactions to be affected in the way you suggest, you would need the horizon to shrink. Basically, not everything expands. Local matter that is bound together and much smaller than the horizon scale isn't impacted by the overall expansion at all. So as long as the horizon grows or stays the same (as it will if we have a cosmological constant), it just won't impact local interactions, let alone subatomic ones.
 
  • #3
Chalnoth said:
as long as the horizon grows or stays the same (as it will if we have a cosmological constant)

I see. I thought the horizon would shrink since the expansion is exponential, but I guess not.
Laura
 
  • #4
I heard this explanation many times but I never understood if there is actual evidence for it or is just an inference.
Perhaps it is just our inability to measure the expansion (if it exists) over short distances.
 
  • #5
Skolon said:
I heard this explanation many times but I never understood if there is actual evidence for it or is just an inference.
Perhaps it is just our inability to measure the expansion (if it exists) over short distances.
There are two separate ways to approach this problem. First, you could approach the problem by considering General Relativity alone, and see what happens when you transition from the perfectly smooth, homogeneous universe of the FLRW metric to one in which matter is clumpy. If you do that, it's relatively easy to show that once a clump of matter forms, it remains stable as the expansion continues.

The second way is to do quantum field theory in a curved space-time background. This is probably a good way to reconcile quantum mechanics and gravity when the quantum mechanical behavior doesn't have much of an impact on the gravitational behavior (as is the case for subatomic interactions in a large expanding universe). In that case, it's trivial to show that the space-time curvature of a universe with such a tiny cosmological constant as the one we measure is so incredibly low that it just doesn't make any noticeable difference.
 
  • #6
Thank you Chalnoth, it is exactly as I thought.
 
  • #7
If the cosmological constant were increasing in time, there could be a "Big Rip" where eventually all matter is torn apart, and perhaps the Higgs mechanism that creates rest mass would be destroyed.
I guess that wouldn't de Sitter space, it would have some other geometry.
Laura
 
  • #8
I hope I'm not wrong, but from what I remember H has a logarithmic growth to a limit value.
That mean "Big Rip" Theory has been disproven.
 
  • #9
Skolon said:
I hope I'm not wrong, but from what I remember H has a logarithmic growth to a limit value.
That mean "Big Rip" Theory has been disproven.

It has? On a quick web-search, I found something http://www.universetoday.com/36929/big-rip/" the likelihood of the Big Rip ever taking place is substantially diminished because evidence indicates dark energy isn't growing in strength.
This doesn't sound very definitive though, and I didn't find anything more definitive.
 
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  • #10
Most of the reason to believe that a big rip won't happen is theoretical in nature. Basically, you have to violate certain energy conditions in General Relativity (namely the fact that matter has positive mass).
 
  • #11
Chalnoth said:
Most of the reason to believe that a big rip won't happen is theoretical in nature. Basically, you have to violate certain energy conditions in General Relativity (namely the fact that matter has positive mass).

Why would it require negative-mass matter? It's just the idea that dark energy, whatever that is, is getting stronger.
 
  • #12
lark said:
Why would it require negative-mass matter? It's just the idea that dark energy, whatever that is, is getting stronger.
Well, it has to do with the details of General Relativity. There are a couple of ways of looking at it, but if there exists some matter that grows in energy density with time, then that matter has pressure that is both negative and greater in magnitude than its matter density. This large negative pressure leads to a negative mass density for some observers.
 
  • #13
Chalnoth said:
Well, it has to do with the details of General Relativity. There are a couple of ways of looking at it, but if there exists some matter that grows in energy density with time, then that matter has pressure that is both negative and greater in magnitude than its matter density. This large negative pressure leads to a negative mass density for some observers.

The dark energy could be the cosmological constant, which isn't matter. That could decay or grow.
 
  • #14
lark said:
The dark energy could be the cosmological constant, which isn't matter. That could decay or grow.
There is no known physical mechanism that could cause it to grow.
 
  • #15
Chalnoth said:
There is no known physical mechanism that could cause it to grow.
I saw papers online about the conjectured decay of the cosmological constant, i.e. tending to zero. If it can decay, it could grow also, I guess.
Sure, the Big Rip would involve new physics. But so do other theories, including inflation.
Laura
 
  • #16
lark said:
I saw papers online about the conjectured decay of the cosmological constant, i.e. tending to zero. If it can decay, it could grow also, I guess.
Well, again, decaying is no problem because it doesn't violate any energy conditions. Growing is a problem because it requires a pressure that is larger than its energy density, violating the weak energy condition.

lark said:
Sure, the Big Rip would involve new physics. But so do other theories, including inflation.
Laura
While true, inflation is a minimal extension of existing physics. Growing dark energy is not.
 

What is exponential expansion?

Exponential expansion refers to the rapid and continuous growth of a quantity or phenomenon over time. In the scientific context, it is commonly used to describe the rapid expansion of the universe in the early stages of the Big Bang theory.

What is the Higgs mechanism?

The Higgs mechanism is a theory in particle physics that explains how particles acquire mass. It proposes the existence of a field, known as the Higgs field, which interacts with particles and gives them mass.

How are exponential expansion and the Higgs mechanism related?

In the early stages of the universe, exponential expansion is thought to have occurred due to the effects of the Higgs field. As the universe expanded, the Higgs field interacted with particles and gave them mass, allowing for the formation of structures like galaxies and stars.

What evidence supports the theory of exponential expansion?

One of the key pieces of evidence for exponential expansion is the observation of the cosmic microwave background radiation, which is thought to be leftover radiation from the early stages of the universe. The uniformity and patterns seen in this radiation support the idea of rapid expansion.

How does the Higgs mechanism impact our understanding of the universe?

The Higgs mechanism is a crucial component of the Standard Model of particle physics, which is our current understanding of the fundamental particles and forces in the universe. It helps to explain how particles acquire mass and plays a role in theories such as the Big Bang and inflation. Its discovery has greatly advanced our understanding of the universe and its origins.

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