Quantum gravity Definition and 482 Threads

Full quantization of gravity is a big issue, but that's not what I'm asking here. I'm asking about quantum effects that involve any form of gravitation (Newtonian or GR) but that don't require a full quantization of GR or anything like that. Things like gravitational neutron interference or the...

In Quantum Mechanics, the position (or momentum) variable is quantized. I define "quantization" as promoting a variable into a probability distribution. For example, with the double slit experiment, the classical assumption that the position/path of a particle is "unique" cannot explain...

I have a major in Mathematics and Mathematical Physics and I'm finishing a masters in Physics (just finishing to write down the dissertation really). I have also already enrolled the PhD course so that I need now to pick an advisor and a theme before june. My main interest since the early days...

From the proceedings of Group32, the 32nd International Colloquium on Group Theoretical Methods in Physics (9–13 July 2018, Prague): https://iopscience.iop.org/article/10.1088/1742-6596/1194/1/012097 M D Sheppeard Abstract: A physical approach to a category of motives must account for the...

The main role in quantum gravity can be played by the uncertainty principle , where is the gravitational radius, is the radial coordinate, is the Planck length. This uncertainty principle is another form of Heisenberg's uncertainty principle between momentum and coordinate as applied to the...

Are there new hermitian operators in quantum gravity? Background: In many worlds interpretation (MWI). We have the preferred basis problem and the basis are for example position, momentum, spin. Each of those bases come from a hermitian operator: they are the eigenbasis of the (for example)...

Would making the graviton self-interaction easily calculable solve most of the problems of quantum gravity?

I want to know the differences between Newtonian Gravity and Quantum Gravity

If we were to find some way to make the graviton self-interaction easily calculable, would applying non-perturbative renormalization on it seem any promising?

Hi. Would it be possible (at least in principle) to use the spacetime perturbance caused by the energy-momentum of a photon (or any other particle) to figure out which way it took in a double slit experiment? Can this question even be answered in today's attempts at quantum gravity?

The questions concern the extension of the holographic principle to the identification of a wormhole between two black holes with negative cosmological constant and an entangled pair on its boundary, included in the conjecture known as EPR=ER ( Maldacena, Susskind). I refer to...

I would like to know if this group http://www.quantumgravityresearch.org/ and its Emergence Theory has any standing in main stream Physics. Thanks Andrew

What is currently the common opinion on Chronology Protection manifested by Hawking almost 30 years ago? There does not seem to be any fully accepted no-go result for Thornian time machines. Energy conditions can be violated in QFT, semi-classical results suffer from counter-examples, Novikov's...

Hi, I'm new on here and this is my first post, so forgive me if I don't master the threads instantly :) - right, now that's out of way: I want to open a discussion on the singularity in Black Holes, namely in regards to the well known issue of Special Realitivity breaking down at the...

Something I've been thinking about lately. If so, how'd we detect high frequency gravitons? I have Bachelors in physics so you may get a little technical ;)

Basically, I'm a Physics/Math MSc student. Currently strengthening my background in Diff. Geo., QFT, GR. I feel like I should start reading some research papers on Quantum Gravity but I do not know where to start. What papers should I start with? I need papers that are accessible to 2nd year...

If a wave function could be assigned to a whole galaxy, would its mass spread along the wave? Could this account for the anomalies in our calculations for galactic spin?

Hey! I will start my third year on the theoretical physics program. I have taken an introduction course in particle physics, just the basics, not much math. (quark and Feynman diagrams the forces and interaction , CRM matrix and cabibbo angle etc. ) Now I'm choosing between relativistic...

Work in quantum foundations is partly considered important because of the hope that the way we think about QM may point to a road to quantum gravity. Lucien Hardy, who is well-known in quantum foundations for his reformulation of QM in terms of five "reasonable" axioms, is one of the people who...

I think this could be an interesting discussion (unless I'm just totally off base): I don’t think were looking at things right in the atomic world. We represent everything as this wave particle duality which is not incorrect but is a great way to visualize particles and forces and their...

I'm currently doing my thesis in QG and there's a distinct gap between where QFT and GR left off and QG begins, and as I'm sure most of you know, in a thesis you're sort of just thrown right into the deep end. As such, I was hoping someone could recommend a decent textbook that gives a solid...

Sabine Hossenfelder recently wrote about an old theory of quantum gravity due to Weinberg: asymptotically safe quantum gravity. Is anyone familiar with this idea? What I couldn't figure out from the article is whether asymptotic safety is an approach to making consistent quantum field theories...

Can whatever type of information be encoded in a boundary in holographic principle? in a question some years ago regarding holography (https://physics.stackexchange.com/questions/75436/are-stokes-theorem-and-gausss-theorem-examples-of-the-holographic-principle) It is said that AdS/CFT is the...

Gravity is weak - while we can study the other interactions with individual particles, for gravity we need macroscopic objects to get measurable forces. This makes it easy to measure quantum effects for the other interactions, but hard to do so with gravity. Gravitational forces are always...

I've completed a masters degree in physics and my research was on cosmological inflation, though knowing some basic GR (Hartle, Schutz, Ohanian) and cosmology (papers), I haven't had any formal course in QFT, I'm now halfway through QFT by Blundell so nothing profound there, now I wanted to get...

I will soon start with the course introduction to QFT and are hence an amateur on the subject. However I could not help but wonder, If particles are describes by oschlliations in a field, how can a "bigger body" be made up of several such oscillation? (A bigger particle is made out of several...

I mean, first GR is a semi-classical theoryt which makes BH neither classical nor quantum. And since it was formed from many particles so it seems in the least it is closer to classical(so no QM should apply) and I don't know if it makes sense to treat it as manyparticle nonrelativistic qft...

Hello physics forum. I am not very well versed in physics, so this question could be a misfire, but I just wanted to clear this up. I watched one of Susskinds holographic principle lectures. So I get that Bob would see Alice turn into a hot mush of energy as she approaches an event horizon...

How is chaos incorporated into quantum gravity theories, or in theories that incorporate all the known 4 interactions? I don't believe I've seen a thread where chaos theory is discussed in relation to superstring theories or LQG. I've seen some papers and dissertations on quantum chaos and...

Testing Quantum Gravity Johan Hansson, Stephane Francois (Submitted on 19 Oct 2017) The search for a theory of quantum gravity is the most fundamental problem in all of theoretical physics, but there are as yet no experimental results at all to guide this endeavor. What seems to be needed is a...

In quantum gravity, I get 'mixed signals' as regards renormalizability. My state of confusion is being caused, I suspect, by an incomplete understanding of what is covered under t'Hooft's 1972 proof that non-Abelian gauge theories are renormalizable. ( = Nobel Prize 1999). Specifically, some...

So my first question is :- Is there any quantum theory success to derive the principle of general relativity? and If this happen, Does this mean we succeeded in finding a quantum theory of gravity?. and My second question is :- Is quantized background-independet theories exists? and If so, is...

New member here, who decided four years ago to look into quantum gravity. My original intentions were pure: really, how hard could quantum gravity be? My current intentions are: to empathize with those who have approached this subject, spent hours, days, months pulling their hair out, yet...

Physicists had success in developing a relativistic quantum mechanics, also Quantum Field theory. I wonder why it's not the same with a quantum gravity theory. I suppose this is mainly because we do not have good emphirical information from a place where Einstein's theory fails: black holes...

Preface There are lots of times in physics when we use approximations of a more accurate or fundamental physics theory because it is easier to work with. For example, in quantum chromodynamics (QCD) lots of calculations are done using the Schwinger-Dyson equations rather than the actual...

Can someone comment on https://arxiv.org/abs/1705.00626 ? It looks quite technical, but potentially very important.

In special relativity, we know, (proper time)^{2} = - (proper distance)^{2}. But, in Causal Dynamical Triangulations (CDT), they introduce an asymmetry parameter \alpha as, (proper time)^{2} = - \alpha (proper distance)^{2} [Q. 1] Can you please explain me about, why we need to introduce \alpha...

Hello! Manoukian's two books on Quantum Field Theory seem pretty good to me, but before buying them I would like to know your thoughts about them! Bear in mind that I need a pedagogical textbook(with good exercises if possible). Thanks!

I suspect the following reasoning is faulty, but I am not sure why. Hence I would appreciate someone pointing out the errors. That is, which, if any, of the following statements are incorrect, and why? 1) Theoretically, albeit not practically due to the large numbers involved, the laws of...

Why is it the case that, in a semiclassical description of the Einstein-Hilbert action, the cosmological constant is small in Planck units? Why does this mean that $$\ell \gg G$$ for ##\Lambda = - 1/\ell^{2}##?

A clever new paper explores the notion that the reduced Planck's constant in the quantum analogy to Newton's constant for macroscopic quantities though a hybrid quantity that generalized the Compton wavelength and the Schwarzschild radius. This allows for a linkage between the Einstein equations...

Are asymptotic safety and causal dynamical triangulation compatible? https://arxiv.org/pdf/1411.7712.pdf As you all know AS has problems with the holographic principle. However, the dimensional reduction obtained in asymptotic safety by using causal dynamical triangulation can make AS compatible...

Consider the following paragraph taken from page 30 of Thomas Hartman's lecture notes (http://www.hartmanhep.net/topics2015/) on Quantum Gravity: Hawking radiation is a feature of QFT in curved spacetime. It does not require that we quantize gravity - it just requires that we quantize the...

I'm an international student currently at the end of my penultimate year in Msci Theoretical Physics in UK and am considering applying to US graduate programs that do high energy gravitational theories, in particular black hole thermodynamics. Both UCSB and UMD seem to be good choices...

It's well known that a single particle can exist in superposition, but what about the gravity of the particle? Is the gravity also in superposition? I suppose this makes it difficult to write a wavefunction, since we can't express it in terms of a field over a single spacetime. But what if we...

[Mentor's note: moved frpm a different thread] I need to know something quick and don't want a new thread. The number one goal of quantum gravity is uniting them in a region where both occur (like in singularities). Another goal is quantum spacetime. I'd like to know if quantum gravity would...

First I don't have extensive knowledge about gravity beyond General Relativity, so please forgive my ignorance about this subject. I have confusion about the relation between GR and QM and I just want a general picture so that I can connect the dots. My questions: 1- Why do we need quantum...

When we finally solved for quantum gravity. Would it only give us a solution to understanding the interaction in Planck scale quantum and spacetime or would it also give us new technology?

Classical mechanics: a minimal standard course by Sergei Winitzki. It is not probably going to help you if you already did not know the subject but is a great refresher nonetheless. He also includes a differential equations refresher that I found invaluable. Looks like he has a ton of other...

Homework Statement I want to calculate the on shell action for the case of a AdS Schwarzschild black hole. Homework Equations Following the case of the flat Schwarzschild black hole I tried to add a counter-term of the type of a Gibbons-Hawking boundary term for flat Minkowski spacetime...