Questions tagged [quantum-gravity]
Any of the various explanations of gravity as a quantum theory, including string theory and loop quantum gravity.
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Probabilistic curvature of spacetime [duplicate]
I was wondering since matter tells space-time how to curve, and since matter is probabilistic in position (say hydrogen atom) is the curvature also probabilistic?
black holes slowly shrink by ...
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BTZ black hole as a quotient of AdS space
I am trying to understand this paper 1 and trying to reproduce some calculations and had some questions about that. In section 3.2, page 12, eq. 3.9, the authors are writing normal geodesics of an ...
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Can you calculate the radius of a hypothetical singular surface inside a black hole from observing changes to its linear momentum?
Say there is a ball of unknown radius surrounded by a bubble. The ball represents a hypothetical singular surface inside a black hole and the bubble represents the event horizon.
If you threw marbles ...
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Is the size of a black hole singularity smaller than a fundamental particle?
I am wondering about the size of a black hole singularity. We know that a classical black hole is infinitely dense. I am not asking about size of event horizon. I am asking about actual size of the ...
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What does the word "Observable" mean in Quantum Gravity?
I have seen the statement in several places that the only "observables" in general relativity or Quantum Gravity are measured at temporal or spatial infinity. This is often used as a ...
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Does the cosmological constant entail a mass for the graviton?
If I consider the Einstein equations into the form
$$
R_{\mu\nu}=\kappa \left(T_{\mu\nu}-\frac{1}{2}g_{\mu\nu}T\right)+\Lambda g_{\mu\nu}
$$
and then linearize them, we should get by moving to ...
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What Does Feynman Mean When He Says Amplitude and Probabilities?
In Feynman lectures on gravitation section 1.4, he tries to debate over whether one should quantize the gravitation or not.
He provides a two-slit diffraction experiment with a gravity detector, which ...
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Inflation in background free models of the universe
There are many authors who are attempting to construct a model of physics that doesn't rely on the objective existence of spacetime. This is part of the work in quantum gravity. This leads to things ...
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What is the difference between Hawking radiation and a black hole laser?
While reading this paper (https://arxiv.org/abs/1409.6550), I got a little bit puzzled: what is the difference between Hawking radiation and a black hole laser? Is it the same thing? From my ...
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Quantum experiments at different heights from Earth
If one were to perform the same Quantum mechanical experiment say the double slit experiment or any other quantum mechanical experiments with identical conditions, set ups and elements. while ...
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Graviton metric interaction
In most discussions on quantum-gravity, graviton is considered as a perturbation that is being added linearly to a flat metric (the $h_{\mu\nu}$ term in $g_{\mu\nu} = \eta_{\mu\nu} + h_{\mu\nu}$). ...
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Why is Perturbative expansion of gravity in terms of $GE^2$?
From General Relativity by Weinberg p.797 edited by Hawking & Israel:
This is to be used to generate a perturbation series in powers of $GE^2$ or $G/r^2$ (where $E$ and $r$ are an energy and a ...
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Explain to a non-physicist what goes wrong when trying to quantize gravity
I am not a physicist, but I'm trying to get a little bit of an understanding of why it is hard to extend the standard model with quantum gravity (i.e. why it's hard to combine QM and GR), cf. e.g. A ...
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Planck Length Calculation
On this question, from long ago, the Planck length is calculated as the length at which the Reduced Compton Wavelength is equal to the Schwarzschild Radius. However, in the calculation, the scalar &...
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Quantised Newtonian potential as an operator in non-relativistic QM [closed]
Suppose we have two slowly moving (effectively static) masses $m_1,m_2$, interacting through gravity, that are not occupying a definite state of position i.e. that matter is being treated quantum ...
