Pb^208 - Pb^208 collisions and vacuum metastability disasters

In summary: TeV is still a pretty low collision energy.In summary, the LHC report acknowledges the existence of CR (Fe?) of energies up to 2TeV/COM so how can that analogy be valid when they eventually are going to collide Pb^208 at as much as 5.5TeV (2013-2014?). The LHC report also claims that the RHIC report pretty much covered it all. But people only acknowledge the existence of CR (Fe?) of energies up to 2TeV/COM so how can that analogy be valid when they eventually are going to collide Pb^208 at as much as 5.5TeV? Furthermore, how come people claim that the upcomming Pb^
  • #1
malm1987
17
0
First off, I'm not in any way anti-LHC. Quite the opposite to be honest. Even so, this speculative disaster scenario (vacuum bubbles) have caught my attention latelly, and I haven't been able to let go off it. Mostly because I find the otherwise brilliant LSAG-report (both actually) to be quite inconclusive on this specific subject. They claim that the RHIC report pretty much covered it all. But they only acknowledge the existence of CR (Fe?) of energies up to 2TeV/COM so how can that analogy be valid when they eventually are going to collide Pb^208 at as much as 5.5TeV (2013-2014?).

I get the part with us presumably are living in a false vacuum and that a quantum tunnelling (either particle accelerator induced or "natural" occurring) could trigger a phase transition into the true vacuum. Furthermore, I'm aware that Rees & Hut was first with these "concerns", but how did they (a) reach the conclusion that we could be in a false vacuum and (b) that the collisions at particle accelerators could possibly cause this vacuum metastability event?

And perhaps most importantly, how come people claim that the upcomming Pb^208 collisions at max energy (aprox. 2.80TeV/COM for this year) would be more likelly to produce a universe gobbling vacuum bubble than the proton collisions at 3.5TeV/COM? Isn't the whole process governed by the achieved energy at COM rather than what the collisions consist of?

If anyone could take the time to straighten this out for me I'd be forever grateful, it has been bugging me for quite a while now=)
 
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  • #2
The LHC disaster scenarios that I'm familiar with are strangelets and black holes. Here are a couple of papers on those:

http://arxiv.org/abs/0808.4087
http://arxiv.org/abs/hep-ph/9910471

Do you have papers you can point us to on the scenario you're referring to (preferably ones that are free online)?

One of the safest, model-independent arguments against all these scenarios is that cosmic-ray collisions could replicate LHC collisions, and they haven't caused any known dramatic events yet. However, these arguments get kind of complicated, and I have often seem them drastically oversimplified (including here on PF). E.g., LHC collisions produce a compound system that is (approximately) at rest, whereas natural collisions don't (usually) do that.
 
  • #3
bcrowell said:
The LHC disaster scenarios that I'm familiar with are strangelets and black holes. Here are a couple of papers on those:

http://arxiv.org/abs/0808.4087
http://arxiv.org/abs/hep-ph/9910471

Do you have papers you can point us to on the scenario you're referring to (preferably ones that are free online)?

One of the safest, model-independent arguments against all these scenarios is that cosmic-ray collisions could replicate LHC collisions, and they haven't caused any known dramatic events yet. However, these arguments get kind of complicated, and I have often seem them drastically oversimplified (including here on PF). E.g., LHC collisions produce a compound system that is (approximately) at rest, whereas natural collisions don't (usually) do that.

I'm sorry that I was a little unspecific in my initial post. Here is a summary of what I was talking about: http://en.wikipedia.org/wiki/False_vacuum. That is a very short summary of Rees & Hut's paper from 1984 which isn't available for free (unfortunatelly).

(See my previous post reg. details of why I find the LSAG-report inconclusive in regards to this specific scenario=)

Here are the separate safety reports (both RHIC and LHC):
RHIC - http://www.bnl.gov/rhic/docs/rhicreport.pdf (p.3)
LHC - http://lsag.web.cern.ch/lsag/LSAG-Report.pdf (p.5)

Is there any risk whatsoever that this actually could happen?
 
  • #4
Reading the LHC report, it looks to me like vacuum bubbles and magnetic monopoles are far more easily dismissed than black holes and strangelets. In all four cases, cosmic rays could mimic LHC collisions.

For strangelets, the cosmic ray argument is complicated by the fact that strangelets are expected to be relatively fragile, so hypothetical strangelets produced by cosmic rays, at large center of mass velocities, might be harmless because they would break up when they hit something. This concern is not present for vacuum bubbles and magnetic monopoles, which are presumably not fragile. Therefore the cosmic ray argument is more secure for vacuum bubbles and magnetic monopoles then for strangelets.

For black holes, there is a pesky case with two large extra dimensions, which can't be ruled out based on cosmic rays colliding with Earth, but that would have resulted in the destruction of white dwarfs and neutron stars. This issue is particular to black holes.

If you provide the reference for the Rees and Hut paper, people here might be able to comment.

The increases in energy you're talking about probably don't affect the conclusions based on the cosmic ray arguments. Cosmic rays go up to energies many orders of magnitude higher than LHC energies, not just a factor of 2 higher.
 
  • #5
Here is a very short summary of both papers, and links to them: http://www.sns.ias.edu/~piet/act/phys/vacuum/index.html

The name of the papers are:

How stable is our vacuum? by Hut, P. & Rees, M.J., 1983
Is It Safe to Disturb the Vacuum? by Hut, P., 1984

Basically, what I wonder is if there is an increased risk of a phase transition in regards to heavy ion collisions (compared to proton ones) since the energy is close to 575TeV/nuclei, which sounds like alot?

But perhaps it is as you said, vacuum metastability is one of the easier scenarios to dismiss thanks to CR observations. Even so, the RHIC-report mentions an upper limit of heavy ion CR as low as 2TeV/COM which then means LHC will be colliding heavy ions at greater energies than has been observed in CR, or am I overlooking something?
 
  • #6
Any input whatsoever would be deeply appreciated. I'm really starting to loose sleep over these upcomming collisions. Especially since, to my understanding, they will be colliding Pb^208 at energies higher than observed in CR.

How can they be sure that the collisions isn't going to cause a quantum tunneling?

Is there an increased risk for things to go bad when they start to collide heavy ions or is that just another crackpot claim by the LHC-opponents?
 

1. What is the significance of Pb^208 - Pb^208 collisions in relation to vacuum metastability disasters?

Pb^208 - Pb^208 collisions, also known as lead-lead collisions, are important in understanding the potential for vacuum metastability disasters. These collisions involve the heaviest stable isotope of lead, Pb^208, and can occur in high energy particle accelerators. By studying these collisions, scientists can gather information about the properties of vacuum and the potential for vacuum metastability, which could lead to catastrophic events.

2. What is vacuum metastability and why is it a concern?

Vacuum metastability is a theoretical concept that suggests that the vacuum, or empty space, we perceive as stable may actually be in a temporary state and could potentially transition into a more stable state at any moment. This could result in a catastrophic event such as the destruction of the universe. While the likelihood of this happening is extremely low, it is still a concern for scientists to understand and study in order to better understand the fundamental laws of physics.

3. How do scientists study Pb^208 - Pb^208 collisions?

Scientists study Pb^208 - Pb^208 collisions by using high energy particle accelerators, such as the Large Hadron Collider (LHC) at CERN, to accelerate lead particles to near the speed of light and then collide them. This produces a state of extremely high energy and density, similar to the conditions of the early universe. By analyzing the particles and energy produced in these collisions, scientists can gain insights into the properties of vacuum and the potential for vacuum metastability.

4. What have scientists learned from studying Pb^208 - Pb^208 collisions?

Through studying Pb^208 - Pb^208 collisions, scientists have been able to gather data that supports the current understanding of the stability of our vacuum. This research has also helped to rule out certain theories about vacuum metastability and has provided a better understanding of the fundamental laws of physics. However, there is still much to learn and the study of these collisions continues to be an active area of research.

5. Is there a potential for a vacuum metastability disaster to occur in our lifetime?

Based on current scientific understanding, the likelihood of a vacuum metastability disaster occurring in our lifetime is extremely low. However, it is important for scientists to continue studying Pb^208 - Pb^208 collisions and other related phenomena to better understand the properties of vacuum and the potential for catastrophic events. This research can also help to develop strategies for mitigating and potentially preventing such disasters in the future.

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