Thread: What do you think about Leonard Susskind?

I would just like to hear other peoples opinion's regarding Leonard Susskind. Thanks.

Tricky one. If somebody really rates the guy, they'll probably say so. If they don't, they might prefer not to say anything. It's one thing to challenge a theory or hypothesis on physics grounds, but giving a personal opinion can get a bit, well, personal.

Originally Posted by GiantEvil

I would just like to hear other peoples opinion's regarding Leonard Susskind. Thanks.

1. He is a good physicist and has done notable research.

2. There are a series of videos of lectures by Susskind on quantum theory and general relativity. They are very good.

3. He has written two books: The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics and The Cosmic Landscape: String Theory and the Illusion of Intelligent Design that are a miserable waste of paper.

4. Susskind takes an extremely strong advocacy position for string theory as a valid model of nature that is unjustified on an objective basis, and that when presented to the lay public as established science is, IMO, downright fraudulent. He has been chastised by 'tHooft for this.

Bottom line: His professional stuff is very good. His popularizations are awful.

3. He has written two books: The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics and The Cosmic Landscape: String Theory and the Illusion of Intelligent Design that are a miserable waste of paper.

Yeah, I read half of The Black Hole War. I'm glad I found it for cheap in the bargain pile.
So what about the Holographic Principle? I can't say I understand it, but I suspect it is crap.

Originally Posted by GiantEvil

So what about the Holographic Principle? I can't say I understand it, but I suspect it is crap.

The holographic principle is speculative, but I would not call it crap.

I don't understand the basis completely. It was proposed by 'tHooft and 'tHooft is as solid a physicist as one could ask for. It is also related to Maldecena's AdS/CFT correspondence conjecture (which Susskind takes as fact without telling the reader of The Black Hole War).

It may not pan out, but I think it is worthy of legitimate research.

Don't take it too literally. The idea is that the information that governs physical processes lies on some boundary. But this begs the question of what, precisely, is meant by information and what precisely is the relevant boundary. The idea has a long way to go before it could become a theory.

It is also related to Maldecena's AdS/CFT correspondence conjecture (which Susskind takes as fact without telling the reader of The Black Hole War).

Well, that was nice of Leonard! But thank's for the info, that helps me form a general idea.

But this begs the question of what, precisely, is meant by information and what precisely is the relevant boundary.

Yea, it seem's this question wanders away from science and towards philosophy. I use the word "data" in my own musings. I suspect that the concept of data is more important to the question of consciousness than to physics. Particles operate according to definable parameters, do they really need to "remember" anything?

Originally Posted by GiantEvil

But this begs the question of what, precisely, is meant by information and what precisely is the relevant boundary.

Yea, it seem's this question wanders away from science and towards philosophy. I use the word "data" in my own musings. I suspect that the concept of data is more important to the question of consciousness than to physics. Particles operate according to definable parameters, do they really need to "remember" anything?

The notion of information is tied to entropy more or less in keeping with Shannon' theory of information channels, but the tie is a bit loose. Conseervation of in formation is sometimes stated in terms of a unitary evolution of the quantum mechanical state function but one needs to be careful here as well. I have not seen an entirely satisfactory definition. I do think there is something deep going on, but more work is needed to make it precise.

Information theory, quantification of information. Fascinating, and it get's back to science, away from philosophy. I'll need to study this more.

2. There are a series of videos of lectures by Susskind on quantum theory and general relativity. They are very good.

Agreed, these videos are the ones where i firstly saw the actual Mathematics involved and thoroughly explained about GR. http://www.youtube.com/watch?v=hbmf0bB38h0

Originally Posted by GiantEvil

So what about the Holographic Principle? I can't say I understand it, but I suspect it is crap.

It is.

Originally Posted by DrRocket

It is also related to Maldecena's AdS/CFT correspondence conjecture (which Susskind takes as fact without telling the reader of The Black Hole War).

DrRocket, what is the Ads/CFT correspondence? I used to hear/see people citing it all the time, but nobody explained what it was.

Recently, I watched a television programme in which Susskind featured. The purpose of his presence was, of course, the holographic principle but, as one might expect of such programmes, little that was intelligible came across. However, Susskind did mention his feeling that as physicists become older, they are more inclined to the view that it is unlikely that a comprehensive and complete understanding of the universe will ever be attained. This seemed ironic as Susskind himself is now getting on a bit and has become known for his attempts to find a "final answer".

Originally Posted by salsaonline

Originally Posted by DrRocket

It is also related to Maldecena's AdS/CFT correspondence conjecture (which Susskind takes as fact without telling the reader of The Black Hole War).

DrRocket, what is the Ads/CFT correspondence? I used to hear/see people citing it all the time, but nobody explained what it was.

AdS -- ant-deSitter space

CFT -- conformal field theory

The AdS/cft correspondence is a conjecture of Maldacena from about 1997 that there is an isomorphism between string theory on a boundary of anti-deSitter space and quantum chromodynamics. There are generalizations.

http://arxiv.org/abs/hep-th/9711200

http://arxiv.org/abs/hep-th/9802150