## Comments about "No-hair theorem" in Wikipedia

This document contains comments about the document "No-hair_theorem" in Wikipedia
• The text in italics is copied from that url
• Immediate followed by some comments
In the last paragraph I explain my own opinion.

### Introduction

The article starts with the following sentence.
The no-hair theorem postulates that all black hole solutions of the Einstein-Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three externally observable classical parameters: mass, electric charge, and angular momentum.
What we are discussing here are the mathematical solutions of the Einstein-Maxwell equations. That is only one side of the picture.
The question is if the physical behaviour of any BH (based on observations of its surroundings) correctly can be described by the three parameters: mass, electric charge and angular momentum.
That means there exist no issue of evolution, shape and magnetic charge. With evolution I mean all what happened to create the BH
All other information (for which "hair" is a metaphor) about the matter which formed a black hole or is falling into it, "disappears" behind the black-hole event horizon and is therefore permanently inaccessible to external observers
The problem is that "all" information about the processes in the past that formed the black hole is permanently lost. We can only calculate the amount of mass of the BH.
Information of the matter that is falling in a BH is not completely lost. If a comet collides with the Sun and if we know more about its specific chemical composition than after the collision this information is still available.
There is still no rigorous mathematical proof of the no-hair theorem, and mathematicians refer to it as the no-hair conjecture.
IMO it does not make sense to try to prove this theorem. The starting point is the physical world and how it evolves. In this particular case it is the evolution of BH's. Part of the problem the details of BH's cannot be observed, making it very difficult to mathematically describe all what is physical involved.

### 1. Example

Suppose two black holes have the same masses, electrical charges, and angular momenta, but the first black hole is made out of ordinary matter whereas the second is made out of antimatter; nevertheless, they will be completely indistinguishable to an observer outside the event horizon.
What is the purpose of an example to explain something if it is highly questionable if the example is real.
None of the special particle physics pseudo-charges (i.e., the global charges baryonic number, leptonic number, etc.) are conserved in the black hole.
End of the Example!
Are we sure that all physical concepts that apply outside a BH also exist within the radius of a BH? Specific are we sure that the "energy conservation law" should apply for a BH?

### 2 Changing the reference frame

Every isolated unstable black hole decays rapidly to a stable black hole; and (excepting quantum fluctuations) stable black holes can be completely described (in a Cartesian coordinate system) at any moment in time by these eleven numbers:
How do we know that a BH is unstable versus stable? and what means stable?
• mass-energy M,
• linear momentum P (three components),
• angular momentum J (three components),
• position X (three components),
• electric charge Q.
These eleven numbers represent the conserved attributes of an object which can be determined from a distance by examining its gravitational and electromagnetic fields. All other variations in the black hole will either escape to infinity or be swallowed up by the black hole.
Why not write this sentence like:
These eleven numbers represent the attributes of a BH which can be determined from a distance by examining its gravitational and electromagnetic fields. All other variations like: etc etc in the black hole can not be determined.
I expect what can not be de

### 6. Observational results

The LIGO results provide the first experimental observation of the uniqueness or no-hair theorem.
The direct measurements of gravitational waves of the LIGO results are an indication that there are very small Black Holes. The results are very impressive but IMO have nothing to do with the no-hair theorem.
The document: does not mention the no-hair theorem.
This observation is consistent with Stephen Hawking's theoretical work on black holes in the 1970s.
Yes it is.

### 7. See also

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

### Reflection

The information paradox, more specific the "energy conservation law" raises some specific questions.
Consider with Lego blocks you build a house, in general any thing that you build with has any beauty or function. This beauty, art work or function is information.
Next you destroy what you have build or created and all this information is destroyed.
The same problem also exist when a library burns down. The burning process is in accordance with the "energy conservation law" but the issue is if that also is true for the contents of the books that are destroyed. All that information is also lost and cannot be recovered from the ashes. From a physical point of view this burning process is irreversible.
The same issues are also at stake when a comet collides with our Sun or a star is captured by a BH. All this processes are irreversible.

### Reflection - Baryonic versus Non-Baryonic

IN sci.astro.research there is the discussion: "Did LIGO Detect Dark Matter? - New paper on arxiv.org". See: https://groups.google.com/forum/?fromgroups=#!topic/sci.astro.research/Rbdjx0o38Ek
The document under discussion is: http://arxiv.org/abs/1603.00464
At page 1 of this document we read:
Suppose that all DM matter in the Universe resided in Milky-Way like halos of mass M = etc
Based on that assumption the article indirectly assumes that there are non-baryonic objects of all different sizes, starting from very small until 30 Sun masses. Unfortunate the article does not explain the details of this building process.

A second document discussed is: http://arxiv.org/abs/1603.08338 In this document the above mentioned document "Did LIGO Detect Dark Matter?" has reference #9.

In principle it is possible that all Black Holes are non-baryonic, including our BH at the center of our Milky Way.
The problem is, as soon when we observe that a star falls into our BH of the center of the Milky way and if we agree that stars are baryonic than our BH is not any more 100% non-baryonic. This opens the way that our BH is 100% baryonic.

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Created: 8 February 2016

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