Quantum gravity Definition and 482 Threads

Is CDT a QFT? Can QFT be used with it to explain fundamental particles?

What are the different approaches to solving quantum gravity that are in the framework of quantum field theory?

this paper https://arxiv.org/abs/1701.02311 Hypercuboidal renormalization in spin foam quantum gravity Benjamin Bahr, Sebastian Steinhaus (Submitted on 9 Jan 2017) In this article we apply background-independent renormalization group methods to spin foam quantum gravity. It is aimed at...

Asymptotic safety in quantum gravity is a local QFT. According to many people, local quantum field theories cannot be correct in terms of being a quantum gravity theory. Lubos Motl outlines 4 reasons why they can't be right. "Quantum gravity cannot be described as a local field theory in the...

Can it be either?

Are there any linear quantum gravity theories out there with respect to the wave function?

On wikipedia, I found one of the objections to MWI. "We cannot be sure that the universe is a quantum multiverse until we have a theory of everything and, in particular, a successful theory of quantum gravity.[73] If the final theory of everything is non-linear with respect to wavefunctions then...

https://arxiv.org/abs/1411.1935 This paper says LQG does not produce the Unruh effect effect, and therefore must be wrong. What do you guys think. You can click into the PDF to see the entire paper.

The de Sitter group is often used as an extension of the Poincaré group, because its a simple group and preserves, in addition to a velocity c, a length L. A natural candidate for this length scale is the Planck length. Thus it seems to make sense to think about the invariant Planck length as...

I ever read that there is no meaning for quantizing fluid mechanics. While left hand side of Einstein field equation used fluid-like approximation for matter (momentum-energy tensor). Therefore, if the first statement is correct then there is no meaning for quantizing gravity, right?

Loop Quantum Gravity, Exact Holographic Mapping, and Holographic Entanglement Entropy Muxin Han, Ling-Yan Hung (Submitted on 7 Oct 2016) The relation between Loop Quantum Gravity (LQG) and tensor network is explored from the perspectives of bulk-boundary duality and holographic entanglement...

Four principles for quantum gravity Lee Smolin (Submitted on 6 Oct 2016) Four principles are proposed to underlie the quantum theory of gravity. We show that these suffice to recover the Einstein equations. We also suggest that MOND results from a modification of the classical equivalence...

What is the second paragraph referring to in quantum gravity? specific name for it (like asymptotic gravity, etc.).. http://backreaction.blogspot.com/2016_09_01_archive.html "Just combining quantum field theory with general relativity doesn’t work because, as confirmed by countless...

Hi all, I fairly basic question about spin foam models in loop quantum gravity. I just want to verify that spin foams represent effectively represent all of spacetime (in a quantum form), and that the idea is that general relativity can be obtained in the classical limit? Not sure if that's...

Hi, the question is obvious from the title. I am looking for the names of the top 30 schools in North America for research work in string theory and quantum gravity. Any feedback will be very helpful.

http://arxiv.org/abs/1609.04813 Quantum gravity on foliated spacetime - asymptotically safe and sound Jorn Biemans, Alessia Platania, Frank Saueressig (Submitted on 15 Sep 2016) Asymptotic Safety provides a mechanism for constructing a consistent and predictive quantum theory of gravity valid on...

What is quantum gravity and how do you calculate the probability of where the particle is? I probably phrased the second half of that question wrong.

Hi all, Following up on another post - for a layman, can someone describe the status of virtual particles in Loop Quantum Gravity models? Since LQG avoid UV divergences, and has a different structure from field-based theories, are virtual particles still talked about? (in the context of closed...

If the amplitude of gravitational waves, frequency of gravitational waves and the vector potential of magnetic field in surrounding of such waves are known then what would be the easiest way to calculate resultant acceleration of electrons? My above question is based on the various researches...

This paper offers a potentially important observational test for quantum gravity http://arxiv.org/abs/1608.04228, Quantum Gravity in the Sky: Interplay between fundamental theory and observations.

its commonly stated that no particle accelerator will ever be built that can probe the Planck scale. what about an can an event horizon telescope observe quantum gravity effects near a black hole, such as Sagittarius A* do the various candidates of QG such as string theory LQG asf gravity...

I'm interested in all discussions but particularly those concerning the areas of QFT and cosmology. I've done much studying on the concept of quantum gravity over the past couple years and I want to learn more :)

Does quantum gravity play role inside brain in ever changing perception of time?

I live in Texas, and I'm going on my senior year of high school. I've come to a problem, I don't know what college/university I should continue my education at. I've already decided what I hope to do when I'm older- qft and quantum gravity, but I don't know what place is good to further ones...

Hello every one I am from Hong Kong. I am in my mid-twenties and I have a very bad result in my undergraduate degree in physics and it hinders me a lot in applying for a graduate degree. Theoretical physics (gravitation, quantum field, strings) is the field that I want to do research in for my...

Hi everyone. I heard that there are several theories or hypotheses to quantize gravity such as superstring theory, loop quantum gravity, etc., and I believe none of them are conclusive (that's what I heard). So, here is my question. 1) Is it because there are no experimental results which prove...

How is loop quantum gravity related to the principle of relativity, in particular to the diffeomorphism invariance of general relativity?

In which branch of physics we can put Quantum Gravity and Cosmology ? -astrophysics ? -relativity ? -quantum mechanics ? -classical mechanics? Or other ?

Does the fact that orbital electrons are stable suggest that gravitation is quantized, analagous to the observation that the stability of orbital electrons suggested that electromagnetic energy was quantized?

First of all, I would like to point out that I have zero background in general relativity, but due to my overwhelming curiosity I will post this question anyway. So, what's wrong actually with applying the correspondence principle, which is typical in quantum mechanics, to quantum gravity...

is Loop Quantum Gravity as popular as String Theory in current physics research?

1. Does LIGO give also any information about seizmic activity? (I think as aspect intended primary to seizmic activity, not in connection with gravitational waves.) 2. Will measurement of gravitational wave give any information about quantum gravity? Is here any plan for this usage?

LIGO will apparently announce on February 11, the detection at five plus sigma of gravity waves (3 solar masses of energy worth in about 100 seconds) emitted as two medium sized black holes of about 65 solar masses combined spiral into each other and merge into a single Kerr (i.e. spinning)...

I speak as an novice in this matter. Has progress been made in reconciling quantum field theory with general relativity? I know that there are theories which show reconciliation but none that seem to be verifiable empirically. Gravitons seem, from a practical viewpoint, impossible to detect...

loop quantum gravity and loop quantum cosmology gravity becomes weaker then repulsive instead of stronger, towards the Planck regime, due to the onset of quantum effects. gravity near Planck energies and densities, LQG/LQC becomes repulsive. at the inflection point where LQG gravity strength...

I'm wondering if Quantum Gravity is expected to be a Theory Of Everything (TOE)? Can we expect that if we combine QFT with GR to get Quantum Gravity, will that be a TOE that explains GR and QFT?

interesting new paper on possible new research direction for LQG http://arxiv.org/abs/1511.07332 Towards self dual Loop Quantum Gravity Jibril Ben Achour (Submitted on 23 Nov 2015) In this PhD thesis, we introduced a new strategy to investigate the kinematical and physical predictions of self...

Hello everyone, as those of you who have helped with my other threads know I'm currently a high school student and an aspiring physicist. I'd like to start out my post by saying that I completely understand that I am very early to be thinking this far ahead, especially when I haven't experienced...

Hi all, According to quantum mechanics, the graviton is the measure of the smallest amount of curvature possible in space-time. I read that the mass which would be required to create this curvature is Planck Mass which is close to the value 10^-5g. But the elementary particles, like electrons...

How would one prove quantum gravity, would there be some thing observable or would it just be a mathematical formula.

I have read that very high precision attempts to confirm the constant speed of light in all directions have been successful. For example in 2009, Stephan Schiller's lab was able to achieve a precision level that was one hundred millions times more precise than the original Michelson Morley...

Neil Turok, Director of the Perimeter Institute of Theoretical Physics in Ontario, Canada suggests scaling invariance is a fundamental property of nature, including spacetime. that nature does not recognize any kind of scale, including Planck scale. if true how would this affect the leading...

Thank you for opening this Thread I am kind of new here and this is my first time to post so I apologize if I did something wrong So my question is where can I study/ research Loop Quantum Gravity I have checked fair amount of grad school websites and compared to Super String, I have not yet...

A critique of LQG here: "The next step in the construction of LQG is to decide what the dynamics are. Technically, this is done either (A) by choosing a "Hamiltonian constraint" in parallel with the Hamiltonian formulation of GR, or (B) in the spin-foam formalism, by postulating some sort of...

OK. I'm sure this is probably been considered before but it is my musings coming off a recent attempt to photograph the Andromeda Galaxy. I did a few two minutes or so shots of Andromeda and stacked them for a total of about 14 minutes. Fairly nice. There is some structure to be seen but...

Does quantum gravity argue that space is not singularly occupied by rectilinear motion?I am reading a general relativity intro sort of thing and this inquiry popped up in my mind. The text was explicating space being occupied by only rectilinear motion and I wondered if quantum gravity could be...

Hi All! I have heard that loop quantum gravity is a "background independent" theory, in that there is no preferred coordinate system. Is LQG also a Machian theory?

this paper Do Black Holes End up as Quark Stars ? R.K.Thakur (Submitted on 25 Feb 2007) The possibility of the existence of quark stars has been discussed by several authors since 1970. Recently, it has been pointed out that two putative neutron stars, RXJ 1856.5 - 3754 in Corona Australis...

Homework Statement Hi, I am studying covariant LQG from the recent book by Rovelli & Vidotto, and i am struggling with the linear simplicity constraint. My problems are not with its proof, that i understand, but rather with the physical interpretation in terms of boost generators. I will try to...

This question, at the moment, is ridiculously difficult or even impossible to answer. Some prefer string theory, and some think that it is overly speculative and LQG may be a better fit, and some say the opposite. I would like to ask; In your opinion, what could be the right theory of quantum...