What is the evidence for dark matter in the solar neighborhood?

In summary: However, as mentioned before, the evidence for their existence is not as strong as for some of the other candidates.
  • #1
wolram
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http://w.astro.berkeley.edu/~mwhite/darkmatter/essay.html, A good overview of dark matter.
Quote.

The density of matter in the solar neighborhood is measured by sampling a uniform population of luminous stars that extends well above the disk of the galaxy. The average velocities of the stars and the vertical distances they traverse above the disk provide a measure of the gravitational restoring force that keeps these stars in the disk. From the strength of this force, one can deduce the total density of matter that exerts this gravitational pull. Comparing this density with actual counts of stars, one finds that the number of observed stars falls short, by perhaps as much as a factor of 2, of the number needed to account for this density. This is the first hint of any dark matter, and it is present in the vicinity of the sun. It should be noted that the amount of such a shortfall in the disk matter is controversial.
 
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  • #2
From http://arxiv.org/pdf/0811.3347v1.pdf
With the standard active neutrinos being too light, such a dark matter candidate cannot be found within the Standard Model. Thus, one can consider the existence of dark matter as evidence for new physics

In this review we focus on dark matter candidates that appear once the Standard Model is extended with the Peccei–Quinn (PQ) symmetry and/or supersymmetry (SUSY): the axion, the lightest neutralino, the gravitino, and the axino. These hypothetical particles are particularly well motivated:

Is new physics required for Dark Matter?

http://web.mit.edu/redingtn/www/netadv/Xdarkmatte.html Dark Matter library.
 
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  • #3
Its been proposed dark matter may arise from quantum gravity.
 
  • #5
It is a safe bet DM requires physics beyond the standard model. For discussion see http://arxiv.org/abs/0704.2276, Physics Beyond the Standard Model and Dark Matter.
 
  • #6
Cronos from your post

I will discuss strong evidence for non-baryonic dark matter and dark matter later in my lectures. Density fluctuation is covered in many other lectures in this school by Lev Kofman, Sabino Matarrese, Yannick Mellier, Simon Prunet, and Romain Teyssier. Neutrino mass is discussed by Sergio Pastor, and baryon asymmetry by Jim Cline. The bottom line is simple: we already know that there must be physics beyond the standard model. However, we don’t necessarily know the energy (or distance) scale for this new physics, nor what form it takes. One conservative approach is to try to accommodate all of these established empirical facts into the standard model with minimum particle content: The New Minimal Standard Model [2]. I will discuss some aspects of the model later. But theoretical arguments suggest the true model be much bigger, richer, and more interesting.

Why is it evident that new physics is needed? What particle is most favored and why?
 
  • #8

1. What is Dark Matter?

Dark matter is an invisible and elusive substance that makes up about 85% of the total matter in the universe. It does not emit, absorb, or reflect any light, which is why it cannot be seen with traditional telescopes.

2. How do we know that Dark Matter exists?

We know that dark matter exists because of its gravitational effects on visible matter. The movement of stars and galaxies cannot be explained by the amount of visible matter alone, indicating the presence of an invisible mass.

3. What is the difference between Dark Matter and Dark Energy?

Dark matter and dark energy are two different and unrelated concepts. Dark matter is a type of matter that makes up a large portion of the universe, while dark energy is a force that is responsible for the accelerated expansion of the universe.

4. How is Dark Matter being studied?

Scientists are studying dark matter through various methods such as gravitational lensing, observations of galaxy rotations, and experiments with particle accelerators. However, because it does not interact with light, it is challenging to directly detect and study.

5. What are the implications of Dark Matter for our understanding of the universe?

Understanding dark matter is crucial for our understanding of the universe as it plays a significant role in the structure and evolution of galaxies. It also has implications for our understanding of gravity and the fundamental laws of physics.

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