It is with great emotion that I announce the passing of our Marcus. Everybody knows here how much he gave to this community. He has been important for me, and for many young quantum-gravity enthusiasts. I learned the first things about loop quantum gravity thanks to him. He had an unique acute...
- Development of spinnetwork theory (recoupling theory on a graph)
- Developments in twistor theory
- Hamiltonian mechanics of covariant systems (Littlejohn)
- Diff invariant gauge theories on a lattice
- The measure on diff invariant space(ashtekar-Lewandowski measure)
- Generalization of...
Studying Loop Quantum Gravity
I put together some informations for students interested in LQG:
http://www.hef.ru.nl/~fvidotto/students/faq.html
I hope you will find it useful, also comments/advises/requests are welcomed.
Cheers,
Francesca
Here it is: http://arxiv.org/abs/1211.0522
Horizon entanglement entropy and universality of the graviton coupling
Eugenio Bianchi
(Submitted on 2 Nov 2012)
We compute the low-energy variation of the horizon entanglement entropy for matter fields and gravitons in Minkowski space. While the...
Right! and indeed in the covariant approach one does not need to write down the Hamiltonian: one writes the transition amplitudes order by order in an expansion! This is precisely the way some of the problems that worry you are circumvented.
These issues are not ignored in the EPRL model...
Achtung: we have to be careful with our approximations, but this does not mean that we can not work with them, on the contrary! For instance when you expand around a cosmological solution, you do not ask your variables to be exactly gauge invariant, but only to be gauge invariant up to the order...
I do not think that this is correct. There is nothing wrong in solving equations approximately. This is also true for the gauge. For example, in doing cosmological perturbation theory one has to solve constraints, of course, but does so only order by order in the expansion.
QCD is different...
ps: experimentalists are not so bad! it's great time for people at Cern, it's nice to see all this excitation... I would not blame them if we don't have yet experiments in quantum gravity, actually it's a theoretician's job to propose some phenomenology to observe... Higgs was crying saying that...
Physics is always a matter of calculating approximately, from the spherical cows to the helium atom to quantum gravity. Indipendently of what would be your favorite theory about human access to Nature, a theory does not exist if it satisfy some abstract laws that we have assumed as rules of the...
Consider a simple quantum mechanical system, and try to describe it in the covariant formalism. The simplest thing could be a hydrogen atom, but this is a special case because it can be solved in a closed form. So, just to fix the ideas, think of an helium atom. In this case one would have a...
You welcome. It's a pleasure to know that there so good biologists around :biggrin:
Do you have any advice for "bioforums" so that I can try the flux in the opposite direction?
The EPRL vertex has been constructed so that it satisfies these 3 criteria (credits Eugenio Bianchi):
locality (each...
This has already been discussed in PF, see this tread:
https://www.physicsforums.com/showthread.php?t=600660&highlight=string+loopIf I can add just a small word: yes, you can combine them, there are of course interesting mathematical tool that you can use from string to LQG and from LQG to...
Suppose you have a triangulated 3d-manifold and you want the curvature on this manifold. The triangulation is made by several tetrahedra: pick one of them, consider it on its own, and consider one of its bone (an edge). The curvature is obtained by performing the parallel transport (a Wilson...