- #26

marcus

Science Advisor

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Tom particularly asked for papers he could print out, mark up, and read on the train. In other words, the video of Madrid conference talks don't suffice. This makes sense to me (I like to mark up printout, write in the margins etc.)

When this thread was started I did not know of a satisfactory bunch of papers that would give a summary of the current status. But now the situation has improved. In the preceding post I gave links to papers that either appeared first in July-August 2011, or if they appeared earlier in 2011 had been substantially revised in July-August. Based thereon I would say briefly:

1. Lqg now has a definitive formulation.

2. Evidence is mounting that this definitive version has the right limits.

3. Considerable effort is directed at seeing how to test loop cosmology with early universe data.

I think the most valuable part of this thread, so far, is the post#1 list of questions to be answered. Tom is right that the Zakopane lectures are not exhaustive---they cover some but not all of these questions---and some, like the meaning of the Immirzi parameter, are the subject of interesting current research! Maybe we can find answers to some of these questions, and indicate ones that involve work in progress. Here is Tom's list:

==quote==

So my question is whether there is a recent review article (or a new book in preparation) covering (some of) the following topics including relevant open issues:

- definition and status of path integral and canonical formalism plus their relation

- open (or solved) issues regarding Hamiltonian, dynamics, regularization, off-shell closure of constraint algebra, ...

- meaning, value, ... of the Immirzi parameter

- different classes of spin networks, different vertices / intertwiners (higher SU(N) and/or higher dimension)

- different graphs w/ and w/o dual triangulation

- quantum deformation, status of the cosmological constant

- matter coupling for fermions and gauge fields, gauge fixing for other gauge fields, SUSY / SUGRA

- renormalization, summing / refining, "block-spin" method

- horizons, surface Hilbert spaces, holographic principle

- definition of observables

- construction of coherent states, semiclassical limit, propagators, ...

- phenomenology

==endquote==

When this thread was started I did not know of a satisfactory bunch of papers that would give a summary of the current status. But now the situation has improved. In the preceding post I gave links to papers that either appeared first in July-August 2011, or if they appeared earlier in 2011 had been substantially revised in July-August. Based thereon I would say briefly:

1. Lqg now has a definitive formulation.

2. Evidence is mounting that this definitive version has the right limits.

3. Considerable effort is directed at seeing how to test loop cosmology with early universe data.

I think the most valuable part of this thread, so far, is the post#1 list of questions to be answered. Tom is right that the Zakopane lectures are not exhaustive---they cover some but not all of these questions---and some, like the meaning of the Immirzi parameter, are the subject of interesting current research! Maybe we can find answers to some of these questions, and indicate ones that involve work in progress. Here is Tom's list:

==quote==

So my question is whether there is a recent review article (or a new book in preparation) covering (some of) the following topics including relevant open issues:

- definition and status of path integral and canonical formalism plus their relation

- open (or solved) issues regarding Hamiltonian, dynamics, regularization, off-shell closure of constraint algebra, ...

- meaning, value, ... of the Immirzi parameter

- different classes of spin networks, different vertices / intertwiners (higher SU(N) and/or higher dimension)

- different graphs w/ and w/o dual triangulation

- quantum deformation, status of the cosmological constant

- matter coupling for fermions and gauge fields, gauge fixing for other gauge fields, SUSY / SUGRA

- renormalization, summing / refining, "block-spin" method

- horizons, surface Hilbert spaces, holographic principle

- definition of observables

- construction of coherent states, semiclassical limit, propagators, ...

- phenomenology

==endquote==

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