Lqg Definition and 259 Threads

Spin networks describing BH have a central node with label taken from an intertwiner Hilbertspace of high dimension (corresp. to hole entropy). Horizon area corresponds to the network links that pass through the horizon. The horizon Hilbertspace turns out to have the same high dimension (again...

What can we learn, if anything, from how the organizers of the ICHEP chose to represent the growing research activity in nonstring approaches to QG? ICHEP is currently going on in Paris and has somewhat more than 1000 participants. International Conf on High Energy Physics. Largely experimental...

regarding the problem of time in QG, Is time absolute or dynamical in LQG? string theory? How does LQG and string theory deal with time in singularities in the center of black holes?

Here is a new LQG resource site. http://sites.google.com/site/quantumgravitytheory/" I hope it will be useful.

I’ve been starting to look at how LQG works, and if I’ve understood it correctly, just thinking about the kinematics, the quantum state of spacetime is encoded in a spin network. If I want to determine the volume of a region of spacetime, the result will be an eigenvalue of some volume...

My impression was that much of the 2009 interest in Horava gravity had waned. A number of problems with it were brought out at the Perimeter Institute conference on it that was held in November 2009. Ted Jacobson did the final summary session of the conference and gave an informative wrap-up...

Hi, this is not based on detailed work but just an idea which arised comparing causal dynamical triangulations and loop quantum gravity. In CDT it seems reasonable to treat spacetime as a fractal. That means there is no limit or minimum length in the triangulations, but the triangulations...

Hi all I use to read posts on LQG where I try to understand what will be evident next 10 years!. I'd just like to know how one can add to spin networks or multiply one by a scalar? Thank you

Seething expanding geometry--new LQG view of reality A view of reality emerging from current LQG research (like 1004.1780) is somewhat analogous to the "seething vacuum" of quantum field theory. But it is a "seething geometry" in which bits of area and volume constantly come into existence and...

First followups of April1780 (new LQG) paper A new formulation of LQG was given in the arxiv paper 1004.1780 which is easier for me to remember as 2010 April1780 That was quite possibly the most influential QG paper of the year so since I may want to link to it several times I'll think of it...

This paper was spotted by MTd2. In it, Seth Major, argues that the quantum GEOMETRY of LQG implies quantum effects on the ANGLE of scattering of particles. But scattering angles can be observed and measured in the large---even if they originate in events too small to be themselves observed...

LQG is an attempt to quantize geometry Noncommutative geometry is an attempt to express the SM geometrically, and is able to derive the SM Lagrangian and prediction of Higgs mass. LQG is not a TOE since it does not include SM, only quantize gravity, and NCG is not a TOE since it does not...

Sometimes I wonder if LQG is as much of a "failure" as string theory, with string theory inability to dimensionally reduce uniquely, and LQG unable to define hamiltonian constraint. Recent paper http://arxiv.org/abs/1005.1866 Large-spin asymptotics of Euclidean LQG flat-space...

The workshop involved some top people including Mathilde Marcolli (longtime co-author with Alain Connes), Jerzy Lewandowski, Thomas Thiemann, Hanno Sahlmann, Jesper Grimstrup, Raimar Wulkenhaar, their co-workers, and several others. It took place the week of 7-13 February at Oberwolfach. Was...

Like phonons? Even if SF is a random lattice, there might be modes emerging from some space of phase space. Look at this example from BEC quantum Chaos: http://www.theo-phys.uni-essen.de/tp/forsch/bec.html

How does LQG work? I know there are gravitons in it but how do they interact with spacetime? Why is it a theory of quantum gravity but not everything? Thanks, Cosmolojosh

Is there some review article which covers the most important literature? Something like this: http://arxiv.org/PS_cache/hep-th/pdf/0311/0311044v5.pdf but for lqg and spin foam models? P.s if there is also up to date list of string literature that would be terrific as well.

Jorge Pulling is teaching a course for UG in intro to LQG, I thought some of you might be interseted, here: http://www.phys.lsu.edu/classes/spring2010/phys4750/ Unfortunately he hasn't yet uploaded his Lecture Notes,I hope he will eventually upload them. I could email him ofcourse... (-:

In LQC (which is something like a toy moidel for LQG) one can derive the so-called big bouce scenario. As far as I can see it is common belief that LQG will lead to something similar. But couldn't full LQG be a "matrix" for a multiverse theory, where - due to quantum fluctuations - baby...

Why NO infinities in LQG ?? what is the reason for LQG in 4-dimension to have NO infinities when doing calculations ?? , is it due to the fact that the VOlume and Area operators are Quantizied ? then if VOlume and Area are Quantizied, there should be a MINIMUM or quantum of area or volume we...

I'm a lay person reading Three Roads to Quantum Gravity. I like the book very much but do have trouble understanding parts of it. Hopefully I can find clarification on a point of confusion for me. I thought loop quantum gravity was based on relational spacetime - that spacetime wasn't...

Verlinde and Jacobson's early work, strongly implies that gravity is emergent. Anyhow, one of Jacobson's and Verlinde's claim in his paper is that since gravity is not a fundamental force, it does not make physical sense to quantize it canonically. So the LQG program is misguided...

http://arxiv.org/abs/1002.1462 Embedding the Bilson-Thompson model in an LQG-like framework Deepak Vaid (Submitted on 8 Feb 2010) We argue that the Quadratic Spinor Lagrangian approach allows us to approach the problem of forming a geometrical condensate of spinorial tetrads in a natural...

I think Markopoulou and Oriti have been sniffing this out a long time. Note that Wen has heuristically linked tensor networks and AdS/CFT (strings!) in the final slide of http://dao.mit.edu/~wen/talks/09QHtop.pdf. http://arxiv.org/abs/0907.2994 Tensor network decompositions in the presence...

Using Verlinde's argument, Smolin shows Loop implies Newton's law of gravity in the appropriate limit. Verlinde's recent paper has thus supplied LQG with a missing piece of the puzzle. Smolin's paper presents his perspective on the significance of the Jacobson 1995 paper and of Verlinde's...

Hello everybody I noticed here are people knowing Loop Quantum Gravity. I am not a professional physicist but I like LQG because it doesn't depend on the background what is needed in General Relativity. I am learning Cramer's Transactional Interpretation of the Quantum Mechanics recently. TI...

1999-2009, key results "look back" in string & LQG In the news there is a lot of "past 10 years", from Bush v.s Gore and 9-11, to Iraq and electing first Black President, to death of Michael Jackson. The first possibly promising trial of HIV vaccine. While 10 years is arbitrary, from 80's was...

Interesting development. We already knew nonstring QG at UC Davis, but hadn't heard of LQG research in the UC Berkeley physics department. The acknowledgments thanked Rovelli among others, for discussions and hospitality---at least one of the authors must have visited Marseille and Pavia* while...

We will get a chance to gauge the progress in LQG---how far along they are in dealing with the main outstanding problems. There will be a workshop at Zakopane in late February early March. But we need someone to help by relaying information. http://www.fuw.edu.pl/~jpa/qgqg3/ Thanks to...

Does this paper prove GR emerge from LQG with matter? A common criticism of LQG is that despite intense research, no semiclassical limit has been shown to connect GR with LQG in the low energy limit. And hence, it is not even a candidate theory of quantum gravity. This paper...

Why the term "cylindrical functions" for the states in LQG? I just can't find a any reference that explain the why of the term "cylindrical" for the states in LQG. Thanks in advance for any comment. Z.

Mass and energy curve spacetime, lots of concentrated mass, lots of curvature. Does the quantized volume of Loop Quantum Gravity correspond to a minimum quantum of energy? If so how does that minimum energy compare to the energy of a individual photon from say a radio station broadcast? It seems...

So Thieman and co are still working on the Master Constraint program for canonical, non-SF, LQG? I thought that approach was dead and given way to SF ala Rovelli

Hi, What is the absolute best grad schools in the US or Europe for String Theory, M-Theory and LQG? I tend to learn better in a classroom environment, so I'm sort of looking for a grad school which actually has relevant courses, and not just a European-style research university where I...

If Black holes do not exist, would string & LQG be falsified? Suppose that black holes do not exist in nature, in that the quantum properties of matter prevents density from increasing beyond a certain limit, as well as gravity's strength diminishing at higher energies. Stellar objects can...

It's important to be able to test LQG with observations, most likely using new data on the microwave Background (CMB) collected by instruments such as the Planck spacecraft . It turned out to be impossible to derive a prediction of dispersion (energy dependent speed of light) at least so...

When gravity is expressed in tools of QFT, the quanta is the spin-2 graviton. What is the quanta according to LQG, SF, CDT, and other BI theories? Is it the spin network? What role does the graviton of QFT quanta play and BI ?

Even if string should turn out to be a dead end as far as unification goes, and fail to produce a predictive theory of how the world works, it could still be interesting and constructive to formulate some version of string within the background independent LQG context. Here is a recent paper...

Hey Marcus, what have been the most important results in LQG from the last ten years, say 1998-2009? A variety of ways from citations to number of papers/researchers, to solving outstanding problems. TO put it another way what does LQG tell us in 2009 that was not known in 1998? Are we any...

Tom.stoer recently started a thread to collect ideas on the topic of stringy dislike of LQG. I thought that was a constructive initiative. At least for me it was helpful to sample what are the current rationales of dismissal, in part because this is a kind of folklore that has changed over time...

Hi, I know a couple of arguments why the loopy guys don't like string theory (perturbative quantization, background dependence, too many statements w/o proof, mysterious M theory, ...) But can anybody tell me why stringy people don't like loop quantum gravity? I mean serious arguments...

Does anyone have any ideas? Marcus, do you have?

http://arxiv.org/abs/0905.3627 At VIII. Disscussion, p. 36: "Our main result is the formula (53) for the inner product in Hj1,...,jn in terms of a holomorphic integral over the space of “shapes” parametrized by the cross-ratio coordinates Zi. In the “tetrahedral” n = 4 case there is a...

http://arxiv.org/abs/0905.3170 In this paper we have recalled the semiclassical metric obtained from a classical analysis of the loop quantum black hole (LQBH). We show that the regular Reissner-Nordstrom-like metric is self-dual in the sense of T-duality: the form of the metric obtained in...

This confirms a beautiful result of Modesto's earlier paper, that LQG seems to coincide with two other very different types of quantum geometry/gravity on the business of dimensionality declining continuously with scale. Fractal-like microstructure of space time. As scale decreases the observed...

I am a new member; I hope I didn't miss existing questions and answers. One of my questions regarding loop quantum gravity / Ashtekar variables is: what is the relation between the familiar SO(3,1) Lorentz symmetry of special relativity and the local SU(2) symmetry of the vierbein-rotation...

What is group field theory, and its relation LQG, CDT? There's no wiki article on gft. I am aware of the numerous articles on arix, could someone summarize what these articles mean?

I'll risk some projections, so if I'm wrong if anyone wants they can fish up this thread 10 months down the road and say "hah hah it didn't happen". Anyway it can help to have an idea of what changes to expect----some rough idea of the recent past and the near future. So here' what I think...

I guess I will post not answered emails so that I can improve my ideas, or perhaps, seek better ideas to whom send a similar message. ********* Dear Petr Horava, In your article you say that your result reproduces the lattice computations of J. Ambjørn, J. Jurkiewicz, and R. Loll...

In the last couple of years there'v been several papers on this, often by people I hadn't heard of before. The question came up in another thread "can you summarize in a single post" the various ideas being discussed? Personally I couldn't but I can dig up some links. Toss them out for you to...