dmg

In LCDM model http://en.wikipedia....ambda-CDM_model There is dark matter density Omegac and physical dark matter density Omegac*h2, where h is the reduced Hubble constant, h=100*H0. What is the interpretation of the dark matter density and the physical dark matter density? What is it that is counted in one, but not in the other?

juanrga, I have read these BBC articles. 1) I don't see that the first one disproves dark matter. They say that Mond theory better predicts the relationship between gassy galaxies' rotation speeds and masses. However, the author conceded that "when you get up to the big scale of clusters of galaxies and you try to apply Mond to the whole thing, you fall short of fixing the missing mass problem". 2) In the second article they don't disprove dark matter either, they only suggest that instead of "cold" dark matter that formed within the first one millionth of a second after the Big Bang, the Universe may instead be filled with warm dark matter (WDM). Where do you see a contradiction?

juanrga, thanks for joining in the topic. I found an interesting discussion about dark matter on NPR http://www.npr.org/templates/story/story.php?storyId=6835217 There they say that in the past a crisscrossing network of strings of dark matter had formed a scaffolding upon which all ordinary matter later accumulated. Stars wouldn't have formed without this scaffolding. And we wouldn't have galaxies without dark matter.

Thanks, pantheory.

Swansot, Pantheory, Airbrush, thanks for your replies! I read about hypothetical particles - weakly interacting massive particles (WIMPs) as possible solution to the dark matter. I wonder if these hypothetical particles obey the Pauli exclusion principle, or can they form a Bose-Einstein condensate?

Swansont, thank you for your replies. Could you explain to me in more detail why gravitational energy has to be dissipated? Does it have anything to do with conservation of energy? It just cannot be locked up inside an event horizon and has to be dissipated? The asinine cretin, thanks.

Maybe I shouldn't have used the word 'collapse' for dark matter. If dark matter interacts only gravitationally, it probably much faster can form black holes.

pantheory, thank you for your reply.

I read that dark matter accounts for 23% of the mass-energy content of the observable universe, while the ordinary matter accounts for only 4.6%. My question is which category do black holes fall into? Do you count them as ordinary matter? If a massive star collapses, we get a black hole. What if a huge collection of dark matter collapses? Will we get a black hole again? I guess yes. Can we distinguish such two black holes? Can we count the latter black hole as part of dark matter?