Quantum gravity Definition and 482 Threads

There's a somehow related set of issues I find myself pondering time and again: In 1995, Ted Jacobson derived Einstein's equations from thermodynamics across a horizon. Roughly, he showed that if the horizon's entropy is given by the Bekenstein-Hawking formula, then the second law of...

if conformal gravity is a successful research program, what would its implications be for loop quantum gravity? can conformal gravity be loop quantized? can loop quantum gravity be made to respect conformal invariance? or are the two mutually exclusive?

Both string theorists and loop quantum gravity theories have proposed that space-time may be something other than the perfectly smooth, perfectly local space of classical general relativity, which can potentially lead to path dependent phase alteration of light from a common source due to the...

Recently, I was thinking about a publishing a theory and how to do it? I found that you can TRY to publish it in a magazine/journal IF they want to do it, but there are also specific options such as registered works.com where you can basically patent ( i don't know hat the correct word here is )...

I have been reading about M-Theory and LQG, and from what I read they are actually very similar. It seems that just a a string-world sheet is the same as a sum of an infinite number of Feynman diagrams, a membrane would be the sum of an infinite number of graphs or networks. Or as Susskind...

for example, is loop quantum gravity/SF in 4 dimensions dual to a CFT in 3 dimensions? does a serious proposal of QG have to respect the holographic principle?

what about loop quantum gravity? plausible formulation of quantum gravity in some universe. not necessarily ours.

arxiv:1503.06237 proposes a 5-qubit error-correcting code as an analogy for AdS/CFT duality. One of the authors, Beni Yoshida, has an expository post at quantumfrontiers.com and motls.blogspot.com. It includes the idea of joining together many instances of the 5-qubit code (which as a diagram is...

Homework Statement [/B]Homework Equations The solutions manual said, "It's trivial. Develop new mathematical tools and construct the theory." I don't really get it :*([/B] The Attempt at a Solution ?[/B]

Ive often heard that in quantum gravity space time is discrete. One analogy I've heard is to think of spacetime as being made up on space time atoms. In these models when the universe expands, is the number of space time atoms thought to increase?

I know there is a theory regarding quantum gravity. Can anyone explains it to me how it works? I did try seaeching online, but all that is shown are the math which I don't even understand.

(I don't know if this is the best place to ask this, if not please feel free to move it elsewhere or delete it.) A number of Quantum Gravity papers explore the evolution of Black Holes and their potential transition to White Holes, and some discuss the possibility of astronomical observation of...

Disclaimer: I'm just an amateur enthusiast who is a programmer during the day I suppose everyone who takes an interest in physics who doesn't have the mathematical tools to further their enquiries end up writing posts like mine, and that at the very least it's nice to see where the ideas reside...

I see that we use dimensional analysis involving constants of nature to obtain the Planck length and then apply the uncertainty principle to find the corresponding Planck mass-energy. But the energy and length scales were found by invoking a "particle" interpretation of fundamental entities of...

I'm beginning to apply to grad schools (primarily in observational or computational cosmology and extragalactic astronomy) but have a deep interest in M-theory and quantum gravity although I haven't been able to study it. I very much enjoy theory and think that I would find studying M-theory or...

I am doing a project of theories of gravity, and am having some trouble understanding whether loop quantum gravity is testable or not. I had some questions which I cannot seem to find the answers to: 1. Is it theoretically possible to probe distances of 10^{-35} or would the concentration of...

Greetings, I have some questions concerning CDT: 1.Where can I find the newest updates on CDT (causal dynamical triangulation) and newest breakthroughs or aproaches to a theory of quantum gravity(as rare as they may be)? 2. What is a recommendable introduction to CDT (that is mathematical)...

I am a new member! I am very much interested and want to pursue theoretical cosmology. I am currently a class/grade 10 student!

We know that a photon has no mass, but has relativistic mass - which means in theory, a photon will have a gravitational field. What is the total possible gravitational affect of all photons (and electromagnetic radiation) emitted from the stars in the universe? Could this account for...

This is a question currently pondered by many Quantum physicists and theoretical physicists. I was just wondering how many of you prefer ST(string theory) as opposed to LQG(loop quantum gravity.) Please provide points and reasons regarding your answer. I will provide an opinion when a few...

I'm watching first and second semester undergraduate level quantum mechanics on-line (MIT Open Courseware). I am enjoying the lectures, but I'm not doing the homework or the math, just getting familiar with the concepts and tools. As I go through the open course ware, I'd really like to be...

I have heard that perturbative quantum gravity calculation predicts an increase of constant G at large distances. So I simply wonder can this growth in G naturally explain the galaxy rotation velocity curve?

why are physisist having so much trouble quantising gravity and getting it to fit into QFT?

Perimeter conference http://pirsa.org/C14020 Here are links to the talks' videos and slides PDF Recent developments in asymptotic safety: tests and properties Tim Morris http://pirsa.org/14040085/ What you always wanted to know about CDT, but did not have time to...

Which do you think are the most promising alternatives?

Hello guys! I hope that you could help me. I want to do my PhD on LQG at the UK and I have the following options: Newcastle, with David Toms. (His research area is QFT on curved spacetime but he liked my project on LQG) Aberdeen, with Charles Wang Nottingham, with Kirill Krasnov or John...

Thanks to GJ for pointing out these three links: http://backreaction.blogspot.ca/2013/10/quantum-gravity-in-cosmic-microwave.html Quantum Gravity in the Cosmic Microwave Background? http://www.nature.com/news/how-to-see-quantum-gravity-in-big-bang-traces-1.13834 How to see quantum...

I mean I don't see any theory actually derives gravitational interaction from actual fields of particles. I only see some manipulation of GR to make it look like a quantum field theory. So are these theories looked upon as one more step to actual unification or are they the FINAL unification...

I am interested in both physics and biology but I have not decided which subject i will choose to do research in the future. I am now studying natural sciences in the university. When I was at high school, one of the biology professor that I met suggested me to choose biology and give up...

http://arxiv.org/abs/1401.6562 This looks very interesting, they are claiming a potential test for quantum gravity . What do we think?

"Hearing a drum's shape" as approach to quantum gravity (Kempf) Achim Kempf and his students have coded an ITERATIVE procedure for finding the shape that when struck has a given sound spectrum. He shows brief movie clips of the computer finding the correct shape by successive approximations, as...

If you search major book retailers on the internet, you can find lots of new and very good books on string theory, for both novice and more advanced students. However, for loop quantum gravity, you can't really find anything. Is there an introductory book that takes you from QFT to LQG ? Where...

Most people here I think will agree that in order to understand what happened at the big bang we most likely need a quantum theory of gravity. There do appear to be models of cosmology such as CCC or Baum/Frampton that seem to try and sidestep this requirement, but looking at quantum gravity...

I've been wondering, why does the world need a theory of quantum gravity? What questions would be solved if such a theory was discovered? What does a theory of quantum gravity mean for black holes, if anything? Try to be quite indepth about the questions rather than something like "It will...

Is it possible to explain simply what a Theory of Quantum Gravity is supposed to achieve/explain and why it is needed.

hi quantum gravity has many problems, I find up to now. I think this problems are conceptual and mathematical is it true? it's conceptual problems are: 1- problem of time 2- quantization and smooth space-time 3- uncertainly in space and the concept of continuous space-time that means you...

For a while I have wondered if the refraction of light had any connection to gravity on small scales (dare I say . . . quantum gravity?!?). I found this paper in the Cornell University Library. Below is the link and a copy of the opening synopsis that anyone can see without downloading it. . . ...

Quantum Gravity: "Lie Groups" vs. "Banach Algebras & Spectral Theory" I'm interested in researching quantum gravity & non-commutative geometry. I am planning to take one math course outside of my physics classes this Fall to help, but can't decide between two: "Lie groups" or "Banach algebras &...

Sabine Hossenfelder recently wrote a blog post containing this parenthetical remark: "(I had meant to write a summary of which possible experiments for quantum gravity pheno are presently being discussed and how plausible I think they are to deliver results, but I got distracted by Dyson’s above...

How specifically does LQG explain how the universe can oscillate from big bang to big crunch ad infinitum? Wouldn't the total energy able to be used as work decrease after a couple of bounces? Am I simply misunderstanding or making a false assumption about what LQG's premises are? I've not...

Hello All, I am beginning to think about PhD applications, and I am of course trying to find out as many opportunities as possible. The field in which I currently work is Causal Dynamical Triangulations, and I am in principle interested in working on this or LQG, though I would also consider...

So why the hot pursuit of QG while GUT unification does not look even attainable. None(AFAIK) of the QG theories seem to address this question (GUT), or am I wrong.

I will work with supernatural units in which \hbar = c = 1 and further, \pi = e = -1 = 1. Using these units, and some minor calculation we see that the Lagrangian is: \mathcal{L} = 1 This not only simplifies matters, but leads to remarkably accurate predictions. For instance, if we assume that...

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Hi, I wasn't sure where to post this so I hope it's ok to post my questions here. I would like to learn the basic fundamentals of Loop Quantum Gravity as efficiently as possible. I'm currently 63 years old. I majored in Physics and Chemistry eons ago, and so I'm rusty on everything but...

I'm currently taking an astrophysics course, and need to do a project on some sort of on-going astrophysics research. Over the last year, I've been reading a few papers here and there in QG (specifically LQG), and was wondering if there was any on-going research relating quantum gravity in...

I've read that if one wants to quantize gravity , there must be a smallest length scale " The Planck length " . If I want to measure the position of a point particle then in conventional Quantum mechanics I'll find it at the point $(x,y,z)$ at some-time $t$ with an arbitrary momentum but this...

"Quantum" gravity -- Planck's constant as a scalar field? I was just reading about a fascinating new theory on the solution to the quantum gravity problem: http://arxiv.org/pdf/1212.0454.pdf I really like it, but I have one big problem with it: The author states that G = \frac{\hbar...

Can someone who understands it explain the significance of the Weinberg-Witten Theorem to the possibility of quantum gravity? (Described here: http://en.wikipedia.org/wiki/Weinberg-Witten_theorem) From the Wikipedia article, the conclusion is I don't understand how that can be correct. Deser...

Hey all, Any suggestions on a good (graduate level) quantum gravity book? I'm quite accustomed with GR (Carroll, Schutz, Wald, Baez all beaten to death!) and am hoping to start acquainting myself with this field as it is what I will be researching. Best TS