# Tag Info

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In classical gravity, the answer is "never". In general relativity, the answer is "never". Now what about a quantum theory of gravity? We don't know how it'll work, but it should reduce to general relativity in the classical limit (i.e. the limit of weak fields and large distances, which is exactly what your question is about). So the answer is still ...

4

The main result of Nottale is well known as just a consistency postulate of quantum gravity: that if the electromagnetic renormalisation of electron mass is cut off at Planck Scale, the correction is of the same order of magnitude that the electron mass itself. This is remarked eg in Polchiski string theory book. Over this consistency postulate, Nottale ...

3

If we know the classical physics theory of the electromagnetic force (and we do), we can guess what the quantum mechanics theory for it should be (and then test with experiment, and as far as we can tell we've guessed correctly). We can do likewise with any classical force. (Although the strong and weak theories were not found by starting from any classical ...

3

No distance is far enough. Among other things, if you are extremely far away, then there is room for lots and lots of things to be far away from you and even if they individually have little effect we can find the net effect of all of them. So we know the effect of each one is not zero. So we can prove the effect of A on B is not zero even when they are ...

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I also don't think I can give a definitive answer. But maybe no one can because maybe no one knows enough about the theory and about why people don't know about the theory. But I will do my best. As mentioned by Nikolajs maybe fee people think they can contribute to it or make use of it. This is partly because of the success of quantum mechanics and ...

1

Quantum mechanics has an absolute time concept, and general relativity has the dynamic time concept of spacetime. The incompatibility of both concepts is called the problem of time in quantum gravity. Yes, but that Wikipedia article needs attention from an expert. It says "therefore, we arrive at the conclusion that 'nothing moves' ('there is no time') ...

1

Your premise is that quantum gravity has effects near the singularity and that the event horizons is a barrier to getting information our from within the horizon. So a simple theoretical investigation is to look at a very very small black hole, one where the outside of the event horizon is still near the singularity and thus the quantum gravity effects are ...

1

Unfortunately, that question's answer depends on the theory of quantum gravity that you chose. But roughly here is the situation : If you take a classical spacetime and quantum matter fields ($G_{\mu\nu} = \langle T_{\mu\nu} \rangle_\omega$), also known as semiclassical gravity, then the stress energy tensor varies with the measurement. The standard ...

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I think it is important to note that the wavefunction of quantum mechanics is not a field like the electric or magnetic field. It assigns complex numbers to configurations. So it is a function where the domain of the function is not space or even spacetime. So there is not a value of the field at a point in spacetime, so there isn't a thing to curve it. ...

1

The question is ill-posed. At the classical level, the force (gravitational or otherwise) between objects never becomes zero. It goes to zero as the distance goes to infinity, but it never really becomes zero. At the quantum level, we don't have a theory of gravity, but already the concept of "distance" doesn't make precise sense anymore, since quantum ...

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Sébastien : I can't give a definitive answer, just an opinion. And I would say that to get anywhere, this theory has to be consistent with relativity, which is one of the best-tested theories we've got. See http://arxiv.org/abs/1403.7377. It has to persuade the "relativists" first, and only then can it gain credence amongst the wider physics community and be ...

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Lets start with the definition of M theory: M-theory brought all of the string theories together. It did this by asserting that strings are really one-dimensional slices of a two-dimensional membrane vibrating in 11-dimensional space. So the universe which is at the microscopic level quantum mechanical, is composed of these ...

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Hawking radiation is indeed usually calculated as a semiclassical effect (classical gravitational field and quantum matter), which is invalid at high energy ($\langle T_{\mu\nu}\rangle >> 1$) and high fluctuations ($\langle T_{\mu\nu} T^{\mu\nu} \rangle - \langle T_{\mu\nu} \rangle \langle T^{\mu\nu}\rangle >>1$). Still, it is a result that is ...

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