# Gross Perrywall phase transition

#### Skeezer

I just watched a video of James Gates and he discussed something he called the Gross Perrywall phase transition. It was named after David Gross, I am assuming most of you are familiar with his work. In an attempt to search more about this I came up empty. I do not know if I am spelling it correctly or not, but I found zero results.

Does anyone here know what I am talking about? Better yet, any good videos you would recommend along the lines of this?

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#### Bobbywhy

Gold Member
Using the search terms "Gross Perrywall phase transition" in Google Search brings me 450 results, none of which explain the process.

There is something called "Gross-Neveu phase transition" described in ArXiV 1203.3580. Is that what you described?

Cheers,
Bobbywhy

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#### Skeezer

Thank you for the reply! I have contacted Dr. Gates and he has informed me that it is spelled "Gross Periwall". I also would like to apologize for being so straightforward and uninformative with what I am seeking to learn. This actually really interests me and I would love to learn more. Here is what I am trying to learn specifically:

The answer he gave here. I have also now found a few papers and a lot of info about perturbation theory but my main interest is about how he describes that at a small enough level actual space begins to disappear?

I am very familiar with Max Plank's work, but this is a bit different. Unfortunetely I am unfamiliar with most maths used, if anyone had any good references that are "dumbed down" that would be awesome, I especially learn best from videos!

Thanks again

#### Skeezer

Is there a more advanced forum that PF that anyone could recommend? I have searched but not personally found anything better but would really like to get to the bottom of this.

Bobby, I am thinking it has more to do with one of these papers:

http://goo.gl/qn07j

Or something that came from the "Princeton String Quartet".

Again I am most specifically looking for a layman explanation as to how space begins to disappear at a small enough level as explained in the link I posted above by Dr. Gates.

#### Skeezer

[STRIKE]Posted this in the General Physics forum but got no answers. I am still very intrigued and figured this might be a better subforum to ask.[/STRIKE]

<< Moderator Note -- Two Threads Merged >>

Question:

I just watched a video of James Gates and he discussed something he called the Gross Periwall phase transition. It was named after David Gross, I am assuming most of you are familiar with his work. In an attempt to search more about this I came up empty. I do not know if I am spelling it correctly or not, but I found zero results.

Here is what I am trying to learn specifically:

(The Question at 47:27 into the video)

The answer he gave here. I have also now found a few papers and a lot of info about perturbation theory but my main interest is about how he describes that at a small enough level actual space begins to disappear?

Maybe something that came from the "Princeton String Quartet".

Again I am most specifically looking for a layman explanation as to how space begins to disappear at a small enough level as explained in the link I posted above by Dr. Gates.

Last edited by a moderator:

#### fzero

Homework Helper
Gold Member
I think Gates is confusing references here. The behavior he is referring to is a result of Gross and Mende on scattering of strings at energies above the Planck scale. What they found was that such processes are dominated by a specific string configuration, which could be described as a surface. If you compute the scale $x_s$ associated with the size of the surface (say as the square root of the surface area), you find that it scales with the energy of the process $x_s \sim l_s^2 E$, where $l_s$ is the fundamental length present in the string theory. This means that for energies $E > l_s^{-1}$, our probes actually get larger than the fundamental scale $l_s$ that we would hope to probe. It is actually impossible to measure distances smaller than around $l_s$ with strings, leading to the concept of a minimal distance. This is discussed, along with other evidence, in this conference talk by Gross, specifically on pages 20-21.

The famous result by Gross and Periwal is this paper that shows that string perturbation theory is incomplete. Such a result on perturbation theory is interpreted (for example in QCD) as signaling the existence on nonperturbative phenomena. It was subsequently discovered that these phenomena could be described by D-branes. It is actually true that D-branes allow us to probe somewhat shorter distances than fundamental strings (see for example Shenker), but I do not think that this is what Gates meant (or at least it would not be a result to credit to Gross-Periwal).

Neither of these Gross et al results should really be called a phase transition, but there is a related concept called the Hagedorn transition. This is a rather technical subject, but in the context of strings, it has been interpreted as a phase transition at a high temperature, beyond which very large strings are produced. This is somewhat reminiscent of the Gross-Mende behavior, where large strings are also the dominant configuration at high energies.

#### Skeezer

Thank you very much for that answer! It definitely clears things up and is sending me in different new directions in my pursuit for knowledge on this topic.

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