43
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An explanation of Hawking Radiation
To answer this we need to talk a bit about how particles are described in quantum field theory.
For every type of particle there is an associated quantum field. So for the electron there is an ...
33
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Can Quantum Field Theory not handle accelerated frames of reference?
No, quantum field theory is perfectly capable of handling accelerated frames of reference:
Quantum Field Theory is based on special relativity. Contrary to some somewhat widespread belief, special ...
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Why is Hawking radiation composed of photons?
The short answer to your title question is that it is not composed only of photons. Hawking's original paper, in which he derived the effect of particle creation by black holes, can be consulted here. ...
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28
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If electrons were just positrons moving backwards in time, then shouldn't we see them coming out of black holes?
The short answer to your question is that positrons are not really electrons moving backward in time, and the premise of your argument doesn't work. However, something like what you are saying, is ...
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27
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An explanation of Hawking Radiation
@JohnDuffield: I can give you both a correct answer in simple terms and the fairy tale, together with references to an explanation how the fairy tale is related to the real thing!
The dry facts are ...
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25
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Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate?
Hawking's explanation in A Brief History of Time is pictorial. It is meant to illustrate the effect, but doesn't really explain it. He actually introduced this illustration in the original article, ...
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23
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Why doesn't Hawking radiation add to the mass of a black hole just as much as it subtracts from it?
The pop science picture of Hawking radiation as particles popping into existence near the event horizon is grossly oversimplified and in many respects misleading. See https://www.forbes.com/sites/...
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20
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Is Hawking radiation real for a far away observer?
External observers and black hole formation
The event horizon is simply the delineation between the part of spacetime from which light can escape and the part of spacetime from which it cannot. In ...
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19
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Does "QFT in curved spacetime" combine QFT and general relativity?
The problem arises due to the fact that if one wants to consider the quantum effects of gravity itself, then one has to compute graviton loop corrections. These are famously non-renormalizable, which ...
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How can black holes evaporate into photons if they contain no anti-matter?
Hawking radiation is not only in the form of photons. Fermions, scalars, other spin-1 particles, and even gravitons also contribute (for example, see https://www.sciencedirect.com/science/article/pii/...
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15
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How can we speak use the notion of "particle" in LHC, given that we live in a curved spacetime?
You seem to be having a few things mixed up, and I hope I manage to address all your confusions. Here are some points to keep in mind, in no particular order.
The length scales involved in most ...
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15
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If electrons were just positrons moving backwards in time, then shouldn't we see them coming out of black holes?
If electrons were just positrons moving backwards in time, then shouldn't we see them coming out of black holes?
If you time reverse an electron falling into a black hole you don’t get a positron ...
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14
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Suggested reading for quantum field theory in curved spacetime
To complement Valter Moretti's excellent answer, I would like to offer a much less rigorous and much more intuitive, physically-oriented alternative: Mukhanov (& Winitzki) - Introduction to ...
14
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Why is Hawking radiation composed of photons?
The electromagnetic field permits zero-mass excitations, down to arbitrarily low temperatures. Black holes are cold.
As the temperature approaches $kT≈1\rm\,MeV$, the high-energy parts of the ...
rob♦
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13
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What's the key point to argue that pure gravity can't be renormalizable from two-loop?
There is no key point, only tedious calculation. It is merely a coincidence. A theory can either be renormalisable, or non-renormalisable; and both scenarios are in principle conceivable. Power-...
13
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Why can't the information inside a black hole be reconstructed from what's left outside?
I'll first give an anecdote exemplifying the issue, and later I'll give the problem in more technical terms. I'm doing it like this because I'm not sure of what pieces of Physics you are acquainted ...
- 16.3k
13
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Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate?
All of the positive claims that you listed:
The radiation arises not from the event horizon exclusively, but from the entirety of the curved space around it
The curved space around the black hole is ...
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12
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How do I derive the Feynman rules for graviton-photon coupling?
I think you could not arrive at your desired Feynman rules because your second equation is wrong. You see, given your definition of the graviton field as a small perturbation to the Minkowski metric, ...
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11
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Origin of $\sqrt{-g}$ in the integral of action $S$
When you're working in general relativity, the coordinates are basically arbitrary and they do not even need to have dimensions of length. This means that the "usual" volume element,
$$
dx^{...
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11
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Can Quantum Field Theory not handle accelerated frames of reference?
Gravity is not "mathematically equivalent to acceleration" - otherwise how could things be accelerated in theories without gravity? Physical principles like the different versions of the ...
- 122k
11
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How to implement a Hilbert space on a manifold?
There are other approaches to doing Quantum Field Theory in Curved Spacetime and I've never seen anyone trying to define a "Hilbert bundle" (so to speak) in order to achieve it. My guess, ...
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11
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What does "conformally coupled scalar" mean?
A minimally coupled free scalar field is described by the action
$$
S[g,\phi] = \frac{1}{2} \int d^D x \sqrt{g} g^{ab} \partial_a \phi \partial_b \phi .
$$
However, this theory is not conformally ...
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11
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QFT on curved spacetime, uniqueness of spacelike hypersurface
how arbitrary is this choice?
It needs to be a Cauchy surface. In other words, it has to intersect every causal curve exactly once. If it missed some curve, you would be missing information on the ...
- 16.3k
10
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Modern treatment of effective QFT in curved spacetime
Objectively speaking, the best book on QFT in curved spacetime is DeWitt's The Global Approach to Quantum Field Theory (2003). For one thing, it was written by one of the founding fathers of the ...
9
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An explanation of Hawking Radiation
I'm late to the party, but I would like to add a new answer in here that tries to capture the important features of Hawking radiation without diving too deep. Since there are already great answers in ...
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9
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How to learn QFT on curved spacetime by self-studying?
I propose that you study the following review article. It is of the algebraic flavor. You will afterwards understand the other approaches fairly easily.
Hollands, Stefan, and Robert M. Wald,
Quantum ...
9
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Evaporation of large charged black holes
Short answer: Yes, if an isolated black hole is large enough (supermassive) and has an initial charge comparable to its mass, then it would lose mass through Hawking radiation much quicker than it ...
- 15.4k
9
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Are particles in curved spacetime still classified by irreducible representations of the Poincare group?
What is a particle?
Before we worry about how to classify particles, we should try to be clear about what "particle" means. Ideally, we would like the definition to have these features:
...
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9
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Why is Hawking radiation composed of photons?
There are already some pretty good answers in this question, but I think there's still some things worth saying.
Why is it the electromagnetic field that is perturbed? [...] Can a black hole also ...
- 16.3k
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Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate?
That Big Think article draws a number of incorrect conclusions from Hawkings particle-antiparticle picture of Hawking radiation, and then goes on to debunk these strawman conclusions and ascribing ...
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Only top scored, non community-wiki answers of a minimum length are eligible