Comments on: Return to the Fold http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/ Random samplings from a universe of ideas. Mon, 01 Dec 2008 23:18:49 +0000 http://wordpress.org/?v=2.3.1 By: PLato http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11003 PLato Mon, 30 Jan 2006 17:56:12 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11003 Layman scratching amazing...that viscosity measures(D brane analysis?) could have been hidden in all this talk? Layman scratching

amazing…that viscosity measures(D brane analysis?) could have been hidden in all this talk?

]]> By: Nick Evans http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11002 Nick Evans Mon, 30 Jan 2006 17:21:06 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11002 Hi Guys. Thanks for your interest in our paper on ghost branes and SU(N|N) regularization. I'll let Olly try to convince you about regulators - as you've deduced it's basically the same story as Pauli Villars though. Flat space as a dual I can try to be helpful for you though. Stay in the pure AdS/CFT Correspondence - move the D3 onto a 5-sphere. The geometry is AdS outside the sphere and flat space inside. What does that mean? It means the theory is totally higgsed at the scale corresponding to the radius of the sphere and below that scale is a mass gap. The gravity description of this "nothing" is flat space. Our host, Clifford, played precisely this game in his enhancon papers removing repulsons and replacing with flat space... cheers Nick Hi Guys. Thanks for your interest in our paper on ghost branes and SU(N|N) regularization.

I’ll let Olly try to convince you about regulators - as you’ve deduced it’s basically the same story as Pauli Villars though.

Flat space as a dual I can try to be helpful for you though. Stay in the pure AdS/CFT Correspondence - move the D3 onto a 5-sphere. The geometry is AdS outside the sphere and flat space inside. What does that mean? It means the theory is totally higgsed at the scale corresponding to the radius of the sphere and below that scale is a mass gap. The gravity description of this “nothing” is flat space. Our host, Clifford, played precisely this game in his enhancon papers removing repulsons and replacing with flat space…

cheers Nick

]]> By: Oliver http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11001 Oliver Mon, 30 Jan 2006 16:10:38 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11001 Hi, I can shed some light on the issue of unitarity at finite cutoff. As effectively said already, if the cutoff is sent to infinity, all fields in the spontaneously broken SU(N|N) theory become infintely massive, with the exception of the physical SU(N) field (and an unphysical copy which is decoupled). One of the crucial ingredients of our ERG approach - which is built in from the start - is that the partition function is invariant under the flow. Since we know that we are dealing with just SU(N) YM at the top end of the flow, we know that we must be dealing with the same theory everywhere along the flow. So, when computing physical quantities, the unphysical fields serve only to regularize the physical theory, and do not spoil unitarity. This works at finite N. Oliver. Hi,

I can shed some light on the issue of unitarity at finite cutoff. As effectively said already, if the cutoff is sent to infinity, all fields in the spontaneously broken SU(N|N) theory become infintely massive, with the exception of the physical SU(N) field (and an unphysical copy which is decoupled). One of the crucial ingredients of our ERG approach - which is built in from the start - is that the partition function is invariant under the flow. Since we know that we are dealing with just SU(N) YM at the top end of the flow, we know that we must be dealing with the same theory everywhere along the flow. So, when computing physical quantities, the unphysical fields serve only to regularize the physical theory, and do not spoil unitarity. This works at finite N.

Oliver.

]]> By: Jacques Distler http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11000 Jacques Distler Mon, 30 Jan 2006 14:15:15 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-11000 Multiply by whatever factor you want, and you can get whatever nonsense you desire. The normalization of the boundary state is fixed by demanding that the open string partition function is properly normalized in the presence of boundaries. Perhaps it might be helpful to note that one can, technically, put either bosonic or fermionic Chan-Paton factors on the boundary; you get the same answer either way. Usually, this is thought of as an either/or proposition. The ghost D-brane proposal is to allow <em>both</em> bosonic and fermionic Chan-Paton factors in the same theory. Multiply by whatever factor you want, and you can get whatever nonsense you desire.

The normalization of the boundary state is fixed by demanding that the open string partition function is properly normalized in the presence of boundaries.

Perhaps it might be helpful to note that one can, technically, put either bosonic or fermionic Chan-Paton factors on the boundary; you get the same answer either way. Usually, this is thought of as an either/or proposition. The ghost D-brane proposal is to allow both bosonic and fermionic Chan-Paton factors in the same theory.

]]> By: Robert http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10999 Robert Mon, 30 Jan 2006 14:07:03 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10999 So, if I multiply by a phase do I really get branes with complex tension? So, if I multiply by a phase do I really get branes with complex tension?

]]> By: Jacques Distler http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10998 Jacques Distler Mon, 30 Jan 2006 13:58:27 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10998 <blockquote>Shouldn't I normalize this somehow with <B|B'></blockquote> No! Because <B|B'>=∞ ! The Boundary State is not a normalizable state in the Hilbert space.

Shouldn’t I normalize this somehow with <B|B’>

No! Because <B|B’>=∞ !

The Boundary State is not a normalizable state in the Hilbert space.

]]> By: Robert http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10997 Robert Mon, 30 Jan 2006 13:42:59 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10997 </em> I could ask the same question in ordinary QFT: I can 'probe' the charge of a particle by computing the amplitude for a T-channel exchange of a photon. That should be proportional to e^2. However, I do not get ghost electrons with positive charge and negative mass by multiplying external electron lines by (-1). I could ask the same question in ordinary QFT: I can ‘probe’ the charge of a particle by computing the amplitude for a T-channel exchange of a photon. That should be proportional to e^2. However, I do not get ghost electrons with positive charge and negative mass by multiplying external electron lines by (-1).

]]> By: Robert http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10996 Robert Mon, 30 Jan 2006 13:38:39 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10996 ? was langle B|B rangle ? was langle B|B rangle

]]> By: Robert http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10995 Robert Mon, 30 Jan 2006 13:38:18 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10995 Shouldn't I normalize this somehow with < B >? Shouldn’t I normalize this somehow with < B >?

]]> By: Jacques Distler http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10994 Jacques Distler Mon, 30 Jan 2006 13:16:57 +0000 http://blogs.discovermagazine.com/cosmicvariance/2006/01/27/return-to-the-fold/#comment-10994 Whoa! Cool! I can mess up, not only my own comment, but succeeding ones as well. WordPress is <em>da Bomb!</em> Whoa! Cool! I can mess up, not only my own comment, but succeeding ones as well. WordPress is da Bomb!

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