Comments about "Hawking radiation" in Wikipedia

This document contains comments about the document "Hawking radiation" in Wikipedia
In the last paragraph I explain my own opinion.



The article starts with the following sentence.
Hawking radiation is black-body radiation that is predicted to be released by black holes, due to quantum effects near the event horizon.
What is important is the word predicted.
It is named after the physicist Stephen Hawking, who provided a theoretical argument for its existence in 1974, and sometimes also after Jacob Bekenstein, who predicted that black holes should have a finite, non-zero temperature and entropy.
The question is what exactly means "that black holes should have a non-zero temperature" and entropy.
Hawking's work followed etc. that, according to the quantum mechanical uncertainty principle, rotating black holes should create and emit particles.
The problem is how do you know that you can use the uncertainty principle to make predictions about the physical behaviour of a BH.
Hawking radiation reduces the mass and energy of black holes and is therefore also known as black hole evaporation.
The first step is to demonstrate or make acceptable that BH are not completely Black.
Because of this, black holes that lose more mass than they gain through other means are expected to shrink and ultimately vanish.
That of course is true, but not highly probable.
Ofcourse when the average density in due time decreases, the likelyhood increases.
Micro black holes are predicted to be larger net emitters of radiation than larger black holes and should shrink and dissipate faster.
When Micro BH's dissipate faster the probability that they exist in the first place decreases.

1. Overview

Black holes are sites of immense gravitational attraction.
That means a BH is not completely black. Any way the name of a Black Hole is misleading because it is based on a human perspective, namely that humans can not observe a BH. In reality it is a very massive object compressed to a tiny space.
Nevertheless, far from the black hole the gravitational effects can be weak enough for calculations to be reliably performed in the framework of quantum field theory in curved spacetime.
Far from a BH the rotating stars around a BH can be described by Newton's Law.
Hawking showed that quantum effects allow black holes to emit exact black body radiation
This already demonstrates why names are misleading. In fact black body radiation has nothing to do with a Black Hole.
The electromagnetic radiation is produced as if emitted by a black body with a temperature inversely proportional to the mass of the black hole.
The program "BH merger" demonstrates three types of simulations. See VB BHmerger operation. The first demonstration is a photon around a BH. The purpose of this demonstration is to show that there could be sphere of photons circulating at a certain distance around a BH. This layer services like a cloud.
This cloud more or less could also service as a reflection layer for infalling photons.

2. Trans-Planckian problem

3. Emission process

Hawking radiation is required by the Unruh effect and the equivalence principle applied to black hole horizons.
This sentence is logical wrong.
Close to the event horizon of a black hole, a local observer must accelerate to keep from falling in.
I expect what they mean is that how closer you approach a Black Hole the larger outward force you need not to fall in.
This is same for any object.
An accelerating observer sees a thermal bath of particles that pop out of the local acceleration horizon, turn around, and free-fall back in.
I expect what they mean is: An observer at rest sees etc.
The problem ofcourse is the use of the word "sees". An observer can only see a particle if the particle emits a photon and the surroundings of the particle not (in the direction of the observer).

4. Black hole evaporation

When particles escape, the black hole loses a small amount of its energy and therefore some of its mass
The issue is how particles can escape from a BH.
The starting definition of a BH is that nothing can escape. The exception is gravitational radiation.

4.1 1976 Page numerical analysis

In 1976 Don Page calculated the power produced, and the time to evaporation, for a nonrotating, non-charged Schwarzschild black hole of mass M
First you have to solve the issue idicated above.

4.2 A crude analytic estimate

5. Large extra dimensions

8. See also

Following is a list with "Comments in Wikipedia" about related subjects


When a BH emits radiation in the form of particles its net mass decreases. The next step in this evolution process should be that the BH should again become vissible. That means inorder for a BH to vanish it first should become a sun like sized star, than a planet sized etc.
A different line of reasoning is that there are all different types and sizes of BH's. Even very tiny BH's in the mass range of comets. When that is the case: once a BH always a BH.


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Created: 8 April 2016

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