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

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Discussion Overview

The discussion revolves around the evidence for dark matter in the solar neighborhood, exploring various theoretical frameworks and candidates for dark matter, including non-baryonic dark matter, axions, and WIMPs. Participants reference empirical observations, theoretical implications, and the necessity for physics beyond the Standard Model.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that the density of matter in the solar neighborhood suggests a shortfall in observed stars compared to the gravitational pull required, indicating potential dark matter presence.
  • Others propose that dark matter candidates may arise from extensions to the Standard Model, such as axions, neutralinos, gravitinos, and axinos, suggesting new physics is necessary.
  • One participant mentions the possibility of dark matter being linked to quantum gravity.
  • There is a suggestion that while WIMPs remain a viable candidate for dark matter, the axion is currently viewed as a favored particle in the search for dark matter solutions.
  • Concerns are raised about the energy scale and form of the new physics required to explain dark matter, with references to various theoretical models and empirical facts.

Areas of Agreement / Disagreement

Participants generally agree that new physics is likely required to explain dark matter, but there is no consensus on which specific candidate is most favored or the implications of this new physics.

Contextual Notes

Participants express uncertainty regarding the energy scales and specific characteristics of the proposed dark matter candidates, as well as the implications of empirical observations on the Standard Model.

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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Space news on Phys.org
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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Its been proposed dark matter may arise from quantum gravity.
 
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.
 
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?
 

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