# Baez LQG talk online

1. Jul 27, 2004

### marcus

A week ago in Dublin John Baez gave one of the plenary talks

the title was:
Loop Quantum Gravity, Quantum Geometry and Spin Foams

this talk is now available online (PS format) from Baez website

http://math.ucr.edu/home/baez/lectures.html#lqg

click on where it says:
"You can see the transparencies of this talk:.... - Postscript version."

the talk is a tutorial with lots of pictures and good explanatory language

It is one of the best introductions to LQG and allied QG approaches that I've seen---the math is there but in its most basic and intuitive form.

The slides are not too abbreviated to read discursively---some care was taken. The summary given here says part of it but does not indicate how conceptual and pictorial the talk actually is. Check it out!

"The last few years have seen the techniques of loop quantum gravity applied to a growing number of problems. They have been used to compute the entropy of various sorts of black holes, including those with non-minimally coupled matter, for which the entropy is not proportional to the area. Perhaps more importantly, loop quantum gravity has given us a clear picture of the quantum geometry of the horizon, which accounts for the microscopic degrees of freedom responsible for black hole entropy. There are tantalizing connections to Hod's work on quasinormal modes, but these remain mysterious. Combined with traditional ideas on quantum cosmology, loop quantum gravity has led to new insights on how quantization can eliminate the singular behavior of geometry at the big bang - perhaps with testable consequences. Predictions of Lorentz symmetry violation may also be experimentally testable, but these remain controversial. Finally, the dynamics of the theory is being studied with the help of spin foam models. My talk will survey all this work with a bare minimum of technical details."

Last edited: Jul 27, 2004
2. Jul 27, 2004

### marcus

The smallest allowed area is

$$8\pi\gamma\sqrt{\frac{1}{2}(\frac{1}{2} +1)} = 5.17004$$

In what units?
Planck of course

so the planck area isnt the smallest measurable area, 5.17 is, instead

this is with the latest Immirzi---credited to Domagala, Lewandowski, and Meissner. A nice thing about Baez shortsweet tutorial on LQG is that it is up to date. Field is moving so fast that tutorials get old after a year or so.

Surveys latest LQG calculations of Black Hole entropy---in cases where it is NOT just A/4, but they calculated it anyway. And reproduce the semiclassical results in all cases with the same Immirzi.

Also fairly up to date report of Bojowald and others LQ Cosmology results.

3. Aug 25, 2004

### physicsisphirst

baez is super cool!!
i don't understand any of this stuff (yet), but his site is really worth hanging out in even if only for the ambience!

his crackpot page is hilarious and for someone like me who is trying to get back into physics after a long, long absence all his advice on books, ideas, physics, math etc etc etc is just extremely inspirational (as is pf)!

this is really a great place:
http://math.ucr.edu/home/baez/

in friendship,
prad

Last edited: Aug 25, 2004
4. Aug 25, 2004

### marcus

POST MORE BAEZ LINKS

right on, phirst!

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