Lower Bound On Dark Matter Mass Density

In summary, the lower bound on dark matter mass density refers to the minimum amount of matter needed for dark matter to play a significant role in the total mass of the universe. It is calculated using a combination of observed data and theoretical models, and is important for understanding the composition and evolution of the universe. This lower bound has changed over time as our understanding and measurement techniques have improved, and it is crucial for our current understanding of the universe and its formation.
  • #1
embphysics
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Hello, I am not quite certain if I have properly placed this query in the correct forum.

I am currently reading this article on dark matter http://pdg.lbl.gov/2013/reviews/rpp2012-rev-dark-matter.pdf

In the first paragraph, the author states, "This leads to a lower bound on the DM mass density,
ΩDM >∼ 0.1..." I don't understand how any of what was said in the rest of the paragraph before this leads to this conclusion. Why must this be the lower bound on the DM mass density? How can one derive this?
 
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Was nobody else able to understand it?
 
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1. What is a lower bound on dark matter mass density?

A lower bound on dark matter mass density refers to the minimum amount of matter that scientists have calculated is necessary for dark matter to make up a significant portion of the total mass in the universe. This lower bound is based on observations of the gravitational effects of dark matter on visible matter, such as the rotation of galaxies.

2. How is the lower bound on dark matter mass density calculated?

The lower bound on dark matter mass density is calculated using a combination of observed data and theoretical models. Scientists use measurements of the rotation curves of galaxies, gravitational lensing, and the cosmic microwave background to estimate the amount of dark matter in the universe. These measurements are then compared to theoretical predictions to estimate the minimum amount of dark matter necessary to explain these observations.

3. Why is the lower bound on dark matter mass density important?

The lower bound on dark matter mass density is important because it helps us understand the composition and evolution of the universe. By knowing the minimum amount of dark matter that must be present, scientists can better understand the role of dark matter in shaping the structure and dynamics of the universe. It also provides important constraints for theories about the nature of dark matter.

4. Has the lower bound on dark matter mass density changed over time?

Yes, the lower bound on dark matter mass density has changed over time as our understanding of the universe and the techniques for measuring dark matter have improved. As more data is collected and analyzed, the lower bound on dark matter mass density may continue to be refined and adjusted.

5. How does the lower bound on dark matter mass density affect our understanding of the universe?

The lower bound on dark matter mass density is a key piece of information that helps us understand the structure, evolution, and fate of the universe. Without dark matter, our current understanding of the universe and its formation would not be complete. By knowing the lower bound on dark matter mass density, scientists can continue to refine their theories and models of the universe and its origins.

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