String theory is what?

[Nautilidae]

The Dagda is suspended for 1 week.

[Gawdzilla Sama]

The Dagda is suspended for 1 week.

At this time.

[Nautilidae]

The Dagda is suspended for 1 week.

At this time.

Are you saying that he has been banned for one week as of now, or are you saying that he has been banned "at this time"?

[JimC]

The Dagda is suspended for 1 week.

At this time.

Are you saying that he has been banned for one week as of now, or are you saying that he has been banned "at this time"?

No, the one week stands, but further suspensions are always possible for further failures to observe our policies...

However, enough about the unpleasant stuff, you can now get back to eddifying us about String Theory!

[Gawdzilla Sama]

However, enough about the unpleasant stuff, you can now get back to eddifying us about String Theory!

I could ban you for that, Jim!

[JimC]

However, enough about the unpleasant stuff, you can now get back to eddifying us about String Theory!

I could ban you for that, Jim!

[Nautilidae]

The Dagda is suspended for 1 week.

At this time.

Are you saying that he has been banned for one week as of now, or are you saying that he has been banned "at this time"?

No, the one week stands, but further suspensions are always possible for further failures to observe our policies...

However, enough about the unpleasant stuff, you can now get back to eddifying us about String Theory!

I was going to present a theory of mine, but someone may steal it...

According to a paper I read, the Hawking radiation of black branes can contain gravitinos. This means that black-branes are a source of supergravity fields. It caused me to ask a question: are there observable effects of supergravity? If so, would we be able to use the effects to detect D-branes?

[hackenslash]

Oh, look! CERN have very kindly provided a list of aimed research. An interesting list in the context of this topic, as it highlights some of the experiments we were discussing.

http://docartemis.com/sciencepodcasters ... -collider/

[kiki5711]

Could string theory have anything to do with spaghetti???

[lpetrich]

According to a paper I read, the Hawking radiation of black branes can contain gravitinos. This means that black-branes are a source of supergravity fields. It caused me to ask a question: are there observable effects of supergravity? If so, would we be able to use the effects to detect D-branes?

I'd like to see that paper.

I checked Wikipedia, and a black brane is a sort of generalization of a black-hole solution.

Supergravity is supersymmetric gravity, and supergravity multiplets contain the graviton (space-time distortion), at least one gravitino, and often additional particles. The simplest 4D supergravity theory has only the graviton and one gravitino. The graviton has spin 2 and the gravitino spin 3/2.

So if you discover a gravitino, you demonstrate supergravity.

Gravitinos interact at gravitational strength; both gravitons and gravitinos have creation rates and interaction cross-sections that are multiplied by
(energy scale / Planck energy)2 or (gravitational constant) (energy)2

The five superstring solutions all include supergravity multiplets in their low-energy limits, as does M-theory.


An evaporating black hole will produce *any* particles that have rest masses less than the object's current temperature.

I haven't tried to figure out D-branes, it must be said. However, I've seen various cosmological speculations that feature them.

[Farsight]

What's cooking guys? String theory is a busted flush. See Woit's blog for info about how it's been downhill all the way for quite a while now: http://www.math.columbia.edu/~woit/wordpress/?p=2794

Also see this New Scientist article http://www.newscientist.com/article/mg2 ... ?full=true about Witten, who was the "guru" of string theory. However take a look at this more recent article http://www.newscientist.com/article/mg20527511.300 and take careful note of this:

"More recently, Ed Witten, the founder of string theory, has been using another of Penrose's creations - twistor theory - to try to reduce string theory's 11 dimensions to a more manageable four."

He isn't working on string theory, not really. He's gone back to http://en.wikipedia.org/wiki/Topologica ... eld_theory. He was working on this twenty years ago. In essence it says fermions are knots of dynamical stress-energy. For example the proton is a trefoil knot. I've got a bit of insider knowledge on this kind of thing. For example a guy called Qiu-Hong Hu was at ABB 50/25 in Bristol talking to Michael Atiyah who is also into knots and topological quantum field theory. Qiu-Hong wrote http://arxiv.org/abs/physics/0512265 which I omitted from my relativity+ acknowledgements, and there's a link to http://www.physorg.com/news182957628.html which hints at things to come:

"The study of knotted vortices was initiated by Lord Kelvin back in 1867 in his quest for an explanation of atoms", adds Dennis, who began to study knotted optical vortices with Professor Sir Michael Berry at Bristol University in 2000. "This work opens a new chapter in that history."

All this is gauge theory, not string theory - straight up. QED is good but QCD needs a bit of a revamp, and the Higgs sector will be going out of the Standard Model after the symmetry between momentum and inertia catches on. These things take time though, a bit like changing the course of a supertanker.

[Nautilidae]

What's cooking guys? String theory is a busted flush. See Woit's blog for info about how it's been downhill all the way for quite a while now: http://www.math.columbia.edu/~woit/wordpress/?p=2794

Also see this New Scientist article http://www.newscientist.com/article/mg2 ... ?full=true about Witten, who was the "guru" of string theory. However take a look at this more recent article http://www.newscientist.com/article/mg20527511.300 and take careful note of this:

"More recently, Ed Witten, the founder of string theory, has been using another of Penrose's creations - twistor theory - to try to reduce string theory's 11 dimensions to a more manageable four."

He isn't working on string theory, not really. He's gone back to http://en.wikipedia.org/wiki/Topologica ... eld_theory. He was working on this twenty years ago. In essence it says fermions are knots of dynamical stress-energy. For example the proton is a trefoil knot. I've got a bit of insider knowledge on this kind of thing. For example a guy called Qiu-Hong Hu was at ABB 50/25 in Bristol talking to Michael Atiyah who is also into knots and topological quantum field theory. Qiu-Hong wrote http://arxiv.org/abs/physics/0512265 which I omitted from my relativity+ acknowledgements, and there's a link to http://www.physorg.com/news182957628.html which hints at things to come:

"The study of knotted vortices was initiated by Lord Kelvin back in 1867 in his quest for an explanation of atoms", adds Dennis, who began to study knotted optical vortices with Professor Sir Michael Berry at Bristol University in 2000. "This work opens a new chapter in that history."

All this is gauge theory, not string theory - straight up. QED is good but QCD needs a bit of a revamp, and the Higgs sector will be going out of the Standard Model after the symmetry between momentum and inertia catches on. These things take time though, a bit like changing the course of a supertanker.

If Witten isn't working on string theory, why did he give a talk on branes with Liouville theory at the Strings 2010 conference? Quantum field theory doesn't involve branes. If he wasn't studying string theory, why would he bother doing research on branes? Plus, topological quantum field theory is an important part of topological string theory, something that he studies.

[Farsight]

If Witten isn't working on string theory, why did he give a talk on branes with Liouville theory at the Strings 2010 conference? Quantum field theory doesn't involve branes. If he wasn't studying string theory, why would he bother doing research on branes? Plus, topological quantum field theory is an important part of topological string theory, something that he studies.

I don't know. But I do know that if you're moving from 11 to 4 dimensions, it's bye-bye branes, bye bye Calabi-Yau, and it's hello Yang-Mills and Hamiltonians. All I can surmise is that the CERN sabbatical was for a reason, and it isn't easy to let people down, especially when... I'll be diplomatic: especially when they've put years of their professional scientific lives into something that hasn't proved to be as fruitful as they'd hoped.

[JimC]

Welcome to Ratz, Farsight, and specifically welcome to the String thread. A relief to have a critic of String Theory here who can say this:

...I'll be diplomatic...

(if you want to know why it's a relief, sample some earlier posts...)

[Nautilidae]

I don't know. But I do know that if you're moving from 11 to 4 dimensions, it's bye-bye branes, bye bye Calabi-Yau, and it's hello Yang-Mills and Hamiltonians. All I can surmise is that the CERN sabbatical was for a reason, and it isn't easy to let people down, especially when... I'll be diplomatic: especially when they've put years of their professional scientific lives into something that hasn't proved to be as fruitful as they'd hoped.

First, has it occurred to you that string theorists also work in quantum field theory? Leonard Susskind is one of the founders of string theory, and he happily studies both quantum field theory and superstring theory. Just because someone studies a different theory doesn't mean that they doubt the theory of their main field. Many tools from quantum field theory, like Yang-Mills, can be incorporated into string theory. Please do not mistake the tone of this message; I'm merely suggesting something to you, not being condescending.

Second, how has string theory not been as fruitful as people has hoped? With string theory, people can realize grand unification, quantum gravity, supersymmetry, the standard model, a solution to the information paradox, and much more all with a single framework.