Quantum gravity Definition and 482 Threads

Hi there, I am still a lay person in this subject, so I have to ask. Don´t we need quantum gravity to study wormholes ? thanks JVD

can anyone tell me what quantum gravity is, and if possible some links on it?

I've just read Quantum field theory of many-body systems Xiao-Gang Wen His web page http://dao.mit.edu/~wen/ I thought that his book might be easier than his papers. hehehe It's a textbook. I did get to learn a few things. Here is what wiki says about the subject. In physics...

HERE IS A WEBPAGE ABOUT HOW IACT WORKS http://magic.mppmu.mpg.de/introduction/iact.html this page helps to survey gammaray astronomy and put IACT in broader context. http://magic.mppmu.mpg.de/introduction/index.html Observing high energy gammarays which have traveled cosmological...

So far all theories of physics have been motivated by the need to explain physical phenomena, but is there any phenomena that requires quantum gravity for explanation? Is this a situation, where the motivation stems from a need to have a model of some specific form, instead of having...

I downloaded William Donnelly's talk, given at Loops'07 Entanglement Entropy in Loop Quantum Gravity http://www.matmor.unam.mx/eventos/loops07/talks/7B/Donnelly.pdf maybe he will discuss it with us I just had a look

I'm having a little bit of trouble distinguishing between the two. Basically LQG states that the quantum structure of spacetime is composed of spin-networks which are composed of strings just with their ends tied, I guess you could say. LQG is also background independent. It says that these...

The conference http://gesalerico.ft.uam.es/strings07/040_scientific07_contents/041_speakers.htm is about string theory, not other approaches to quantum gravity. It should be quite clear to anyone who understands LQG-like approaches to quantum gravity that there is not one single word in...

Edward Witten is the most influential string theorists in the world, is now doing research into gravity that is decidedly non-string, and very similar to LQG. here's a link http://gesalerico.ft.uam.es/strings07/040_scientific07_contents/041_speakers.htm his research program is titled "...

"the programme for the consistent canonical part of the quantization of four-dimensional Einstein’s general realtivity is essentially complete." Eyo Eyo Ita III I guess we must be close. :smile:

Quantum Gravity & Quantum Geometry Live :) Hi, Some records as well as lecture notes about different approaches to quantum gravity are now avaible to download from the website of QG Zakopane 2007 School: http://www.fuw.edu.pl/~kostecki/school.html I think that at least two talks of Carlo...

Marcus! Surely, I’m not the only one reading the links that you provide! http://arxiv.org/PS_cache/arxiv/pdf/0706/0706.1534v1.pdf Coupling gauge theory to spinfoam 3d quantum gravity Simone Speziale June 11, 2007 Note: The Acknowledgments: The author is particularly grateful to Carlo...

I was reading somewhere (I think wikipedia on quantum geometry?) that Loop Quantum Gravity is "noncommutative"...but I'm trying to figure this out on my own (naturally, there are no citations for this claim!). Now, my reasoning is that one would try to express various differential forms in...

Another first. http://arxiv.org/abs/0704.3214 (2+1)-Dimensional Quantum Gravity as the Continuum Limit of Causal Dynamical Triangulations D. Benedetti, R. Loll, F. Zamponi 38 pages, 13 figures "We perform a non-perturbative sum over geometries in a (2+1)-dimensional quantum gravity...

Bee has organized an informal working and discussion group at Perimeter for people researching ways to empirically test QG ideas they found a room where they can meet Tuesday afternoons, and part of organizing the group was to set up a BLOG, http://qglab.blogspot.com/ which she says is...

Sabine Hossenfelder: Phenomenological Quantum Gravity The search for a satisfying theory that unifies general relativity with quantum field theory is surely one of the major tasks for physicists in the 21st century. During the last decade, the phenomenology of quantum gravity and string...

As far as I understand, loop quantum gravity treats space and time on very different footings. What I get is that in LQG time acts like a CPU clock in a computer representing a counter for the subsequent changes in the descrete structure of space. What worries me about this picture is, when...

For those who have been following my model, I see this as another step in the right direction. http://arxiv.org/pdf/0704.0278 q-deformed spin foam models of quantum gravity Igor Khavkine and J. Daniel Christensen 02 April 2007 Large triangulations are necessary to approximate semiclassical...

In loop quantum gravity it is assumed that space is not infinitely divisible. The nodes are not space . Actually they are the infinitely divisible part of a matter. The distance between the nodes are not discrete. The distance between the nodes may be 1.5 Planck's length or 2.5 Planck's length...

Loop quantum gravity and Planck-size black hole entropy http://arxiv.org/abs/gr-qc/0703116 Alejandro Corichi, Jacobo Diaz-Polo, Enrique Fernandez-Borja Unfortunately ... this non-expert ... did not see the light. I did do some research into what is expected to happen at CERN. I'll just...

Marcus! Your find... http://arxiv.org/abs/gr-qc/0703097 New directions in Background Independent Quantum Gravity Fotini Markopoulou Perimeter Institute for Theoretical Physics Good stuff. How influential is Fotini Markopoulou? Is anybody going to listen? jal

https://www.physicsforums.com/showthread.php?p=1162921#post1162921 http://math.ucr.edu/home/baez/marseille/krasnov.jpg Jal called attention to Krasnov's most recent paper on non-metric QG. https://www.physicsforums.com/showthread.php?t=158874 =========== here's a video of K.'s most recent...

This just out: http://arxiv.org/abs/gr-qc/0702144 Singularities and Quantum Gravity Martin Bojowald 41 pages, lecture course at the XIIth Brazilian School on Cosmology and Gravitation, September 2006 IGPG-07/2-4, NSF-KITP-07-19 "Although there is general agreement that a removal of...

Here is a list of the mathematics one needs to know for string theory (i'm skipping the simple 1st and 2nd year math courses). http://superstringtheory.com/math/index.html Real analysis In real analysis, students learn abstract properties of real functions as mappings, isomorphism, fixed...

has someone taken a look to this book? https://www.amazon.com/gp/product/0199269696/?tag=pfamazon01-20 https://www.amazon.com/gp/product/0199269696/?tag=pfamazon01-20 Quantum Gravity Meets Structuralism: Interweaving Relations in the Fundation of Physics by Dean Rickles and Steven French...

In Einstein equation of general relativity, one side is stress-energy tensor and the other side is the Einstein tensor (functions of metric tensor). But the problem is in order to describe the matter field/stress-energy tensor, we have to use the space and time, which are determined by the...

A Stanford researcher has measured the effect of gravity using quantum mechanics: http://www.newscientist.com/article.ns?id=dn10948&feedId=online-news_rss20 Can this shed new light on the gravitational constant, dark matter, the quantum vacuum, or even the universe? Why did they have to use...

What is Quantum Gravity and the Curvature of Spacetime and how is it all relevant to one another?

Usually one thinks of quantum gravity effects becoming important at the scale of the Planck length. I have however some strong doubts about this because of the following. In relativity, one uses "sticks" and clocks to be able to define events in spacetime. Consider for instance a light...

"[URL First Quantum Geometry and Quantum Gravity School March 23 - April 3, 2007 Zakopane, Poland[/URL] Invited Lecturers: Jan Ambjorn, Abhay Ashtekar, Alain Connes*, Laurent Freidel, Shahn Majid, Martin Reuter, Hendryk Pfeiffer*, Jean-Marc Schlenker, Thomas Thiemann *-to be confirmed Local...

I find the covariant version of loop quantum gravity http://arxiv.org/abs/gr-qc?papernum=0608135 more appealing than the usual LQG approach. What the experts think?

http://arxiv.org/abs/hep-th/0611042 Hidden Quantum Gravity in 4d Feynman diagrams: Emergence of spin foams Aristide Baratin, Laurent Freidel 28 pages, 7 figures "We show how Feynman amplitudes of standard QFT on flat and homogeneous space can naturally be recast as the evaluation of...

Kea posted this on another thread: The Tomita-Takesaki results are and exciting breakthrough in AQFT, by now getting to be pretty well understood. The beginnings of it are in Haag's book Local Quantum Physics. Another line of work in AQFT that approaches the idea of matter in QG is...

http://arxiv.org/abs/astro-ph/0610571 On the Problem of Detecting Quantum-Gravity Based Photon Dispersion in Gamma-Ray Bursts Jeffrey D. Scargle, Jay P. Norris, Jerry T. Bonnell 63 pages, 19 figures, to be submitted to the Astrophysical Journal "Gamma-ray bursts at cosmological...

She is visiting from the AEI-Golm and will give a seminar talk at Perimeter tomorrow. Kristina Giesel Algebraic Quantum Gravity Thursday September 7, 2006, 12:30 PM "We introduce a new top down approach to canonical quantum gravity, called Algebraic Quantum Gravity (AQG): The quantum...

It seems to me that Loop Quantum Gravity has already ruled out the possibility that the spacetime could be a manifold like S^4, by making the assumption that the tangent bundle is trivial, or M = R x Sigma. TS^4 is non-trivial implies we cannot find a basis of tetrad fields that span the module...

http://xxx.unizar.es/PS_cache/gr-qc/pdf/0607/0607130.pdf Title: Quantum Geometry and its Implications for Black Holes Authors: Martin Bojowald Comments: 16 pages, Plenary talk at ``Einstein's Legacy in the New Millenium,'' Puri, India, December 2005 General relativity successfully...

selfAdjoint called attention to a new series of papers by Thomas Thiemann (AEI-Golm) and Kristina Giesel (Perimeter Institute) https://www.physicsforums.com/showthread.php?p=1045334#post1045334 in post #503 of the non-string QG bibliography thread. I am printing off the first in the series...

Here is a set of 100-some slides for a talk Daniele Oriti gave in September 2005 called The Group Field Theory Approach to Quantum Gravity http://www.phy.olemiss.edu/GR/qg05/talks/oriti.pdf The talk was given at this conference in Sardinia: http://www.phy.olemiss.edu/GR/qg05/ This is the...

I have finished a quick first reading of the rovelli at all paper ingraviton propagator http://arxiv.org/gr-qc/0604044 I couldn´t dive too much into the details because spin foams was a prerequisite and i only could do an equally fast reading of the alejandro perez review of the subjecto...

This is the start of a presentation of some work I have done over the past year and hope to publish. This is how it is that quantum information is preserved in quantum gravity and cosmology. This will involve a number of posts along this thread. The next three posts involve quantum...

I had studied LQG using the thieman articles (mostly the brief of around 80 pages) and some other brief reviews (the one on living reviews on gnernal relativity for example) and also i had readed some articles announced in the threads which maintains Marcus. But i wanted a most serious...

http://lambda.gsfc.nasa.gov/product/map/dr2/pub_papers/threeyear/parameters/wmap_3yr_param.pdf Look on page 43, at figure 17 the 68 % confidence interval for Omega_k is [-0.037, -0.008] this means that the 68% confidence interval for Omega_total is [1.008, 1.037] anything over 1...

http://arxiv.org/abs/hep-th/0603022 Quantum Gravity and the Standard Model Sundance O. Bilson-Thompson, Fotini Markopoulou, Lee Smolin 12 pages, 21 figures "We show that a class of background independent models of quantum spacetime have local excitations that can be mapped to the first...

http://christinedantas.blogspot.com/2006/02/basic-curriculum-for-quantum-gravity.html QG continues to gain definition as a field. Lee Smolin is currently teaching an online video course---two lectures a week---that some of us are following. Today Christine Dantas, who has a QG blog...

For those who are interested in QG, but find it a bit daunting [like me], here is a nice read: http://www.arxiv.org/abs/hep-th/0601129 Loop and spin foam quantum gravity: a brief guide for beginners

http://golem.ph.utexas.edu/~distler/blog/archives/000713.html" has a new post about CDT. He goes on about continuum limits and doesn't believe Reuter on the GR renormalization fixed point, suggesting (on no evidence that I could see) that the GR doesn't have the right kind for a good continuum...

I just finished reading this paper, and have a question: CAUSAL SITES AS QUANTUM GEOMETRY J. DANIEL CHRISTENSEN AND LOUIS CRANE Abstract. http://arxiv.org/PS_cache/gr-qc/pdf/0410/0410104.pdf We propose a structure called a causal site to use as a setting for quantum geometry...

Alain Connes---views on quantum gravity Peter Woit flagged this wide-ranging interview with Alain Connes http://www.math.columbia.edu/~woit/wordpress/?p=313 Connes voices opinions on string theory, the Bourbaki, and a host of other subjects...

Oriti's new book! Cambridge (2006) "Towards Quantum Gravity" Daniele Oriti is a really nice young person as well as being on the frontline of QG research. He is at Cambridge His PhD thesis contained ground-breaking quotations from Homer Simpson and Groucho Marx. the important thing is that he...