Comments on: News From the Front, IV

By: LaTeX Spoken Here! - Asymptotia

LaTeX Spoken Here! - Asymptotia — Tue, 12 Dec 2006 22:33:29 +0000

[...] The first equation I shall try is the following (for more on unpacking this equation and its meaning, see this post and links therein): [...]

By: Stephen Uitti

Stephen Uitti — Thu, 26 Oct 2006 15:11:15 +0000

Let me get this straight, or at least twisted in a knot. If a string theory hasn’t got a brane, then it’s a straw-man argument.

By: Plato

Plato — Wed, 25 Oct 2006 15:46:36 +0000

Hello Clifford,

I like the fact that scientists sense the emergence of response necessary, for actions initiated from their fellow scientists(Lee Smolin).

This is the kind of debate that has been long hoped for as I watched and looked for such situations to occur, for they were most enlightening factors too, “what use this subject” even to the lay person.

So one had to indeed look for such processes “in physics” to compare any “model assumption” to help push perspective forward?

By: Alejandro Rivero

Alejandro Rivero — Wed, 25 Oct 2006 01:48:16 +0000

Actually, do all the papers on string theory agree nowadays to the need of having “inside the box” a Lagrangian corresponding to a relativistic string as physics understands it? Sometimes, specially with membranes and with topology stuff, I am under the impresion that any, say, “theory of one dimensional geometric segments” is considered to be a theory of strings.

By: Clifford

Clifford — Mon, 23 Oct 2006 22:59:59 +0000

It is not an attraction per se….. I make an observation that it is possible, and that it means something about the physics. It does not mean that not being able to do it is bad. Far from it… it is very good. Consider the degenerate two-well system in QM. Then do more wells…. Then do an infinite number.

Thanks,

-cvj

By: Aaron F.

Aaron F. — Mon, 23 Oct 2006 22:06:43 +0000

Hmm… so if asymptotic series aren’t all that bad, and don’t prevent you from coming up with usable answers, what’s the attraction of being able to calculate things exactly?

p.s. When you say “exactly,” I’ve been assuming you mean in closed form, with no series to sum or anything. Is that how most people actually use the term?

By: JustAnotherInfidel

JustAnotherInfidel — Mon, 23 Oct 2006 14:49:12 +0000

I saw this paper on the ArXiv this morning and am looking forward to reading it. Hopefully I am not alone in recognizing the irony here—the man who taught us about D branes now says that they’re not altogether necessary. Thank you for a very readable post Dr. Johnson.

By: Clifford

Clifford — Mon, 23 Oct 2006 06:06:39 +0000

Hi Aaron… Kind of… but be careful: Having an asymptotic series in perturbation theory is not a problem. It just means you have to do more than perturbation theory, generally. It tells you that your theory is quite rich, in fact. This is true in field theory too, generically. It is also common in even some of the simplest quantum mechanical systems one can think of.

Cheers,

-cvj

By: Aaron F.

Aaron F. — Mon, 23 Oct 2006 05:32:36 +0000

Cool! And completely over my head, but let’s see if I got this much:

1. Because they involve branes, grown-up string theories have series that can’t be summed, and therefore problems with no closed-form solutions?
2. Your baby theories are similar to string theories, but have no branes (giggle), and therefore guarantee closed-form solutions to everything?