Any of the various explanations of gravity as a quantum theory, including string theory and loop quantum gravity.

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Where does the $10^{500}$ estimate for the number of stringy vacua come from?

This number is thrown around a lot so I'd like to understand its origin. I know that it counts compactifications of string theories on (not only) Calabi-Yau manifolds and probably also some other ...
7
votes
2answers
354 views

Is taking the “square root” of the densitized inverse triad irregular in loop quantum gravity?

In loop quantum gravity, the canonical (Ashtekar) variables are chosen to be the densitized inverse triad $\mathbf{E}$ and some rotation connection field $\mathbf{A}$. To get the ordinary triad from ...
9
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4answers
1k views

Discussion of the Rovelli's paper on the black hole entropy in Loop Quantum Gravity

In a recent discussion about black holes, space_cadet provided me with the following paper of Rovelli: Black Hole Entropy from Loop Quantum Gravity which claims to derive the Bekenstein-Hawking ...
5
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4answers
664 views

Does string theory tells us anything concrete about black hole decay?

EDIT: I edited the question to reflect Moshe's objections. Please, look at it again. It's apparently a black hole time around here so I decided to ask a question of my own. After a few generic ...
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5answers
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The final death of a black hole

What are the different death scenarios for a black hole? I know they can evaporate through Hawking radiation - but is there any other way? What if you just kept shoveling more and more mass and ...
9
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5answers
925 views

What is the role spin-networks play in Loop Quantum Gravity?

This is a second question (in what will probably become a series) in my attempt to understand LQG a little. In the previous question I asked about the general concepts behind LQG to which space_cadet ...
17
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4answers
2k views

Give a description of Loop Quantum Gravity your grandmother could understand

Of course, assuming your grandmother is not a theoretical physicist. I'd like to hear the basics concepts that make LQG tick and the way it relates to the GR. I heard about spin-networks where one ...
5
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1answer
394 views

Quantum Gravity and Calculations of Mercury's Perihelion

In an astronomy forum that I frequent, I have been having a discussion where the state of quantum gravity research came up. I claimed that Loop Quantum Gravity theories couldn't prove GR in the ...
7
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1answer
2k views

What specifically does the phrase “continuum limit” mean?

I'm interested in the meaning of the phrase "continuum limit" specifically as it is often used in expressions relating to the ability of a quantum gravity theory to recover GR in the continuum limit. ...
10
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3answers
487 views

Hawking radiation and quark confinement

The simple picture of Hawking radiation is that a pair-antiparticle pair is produced near the event horizon, then one falls into the black hole while the other escapes. Suppose the particles are ...
3
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1answer
489 views

Introductions to discrete space-time

It's comparatively easy (cum grano salis) to grasp the following concepts: Euclidean space-time (continous space and continuous time) classical mechanics (discretely distributed matter in continous ...
2
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1answer
352 views

Possibly naive question about quantized space-time

I beg your pardon in advance if this question is naive. In Quantum Mechanics, discrete values of measurements occur only in relation to bound states. This is because of the general solution for the ...
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3answers
812 views

What are some approaches to discrete space-time used in modern physics?

This thought gave rise to some new questions in my mind. What are the consequences for: How would it affect duality i.e. particle, wave property of photons? How does this statement affect the ...
5
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3answers
305 views

What is necessary for a causal set to be manifold-like?

A causal set is a poset which is reflexive, antisymmetric, transitive and locally finite. As a motivation, there is a programme to model spacetime as fundamentally discrete, with causal sets ...
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5answers
5k views

A list of inconveniences between quantum mechanics and (general) relativity?

It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them? E.g. relativity ...