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This paper appears to further the case for DM vs MOND http://arxiv.org/abs/1401.3162, A simple model linking galaxy and dark matter evolution.
Chronos said:This paper appears to further the case for DM vs MOND http://arxiv.org/abs/1401.3162, A simple model linking galaxy and dark matter evolution.
TEFLing said:MOND can be construed as claiming, that at large distances, i.e. long range, gravity switches character, from 1/r2 to 1/r
Does that have the simple interpretation, that gravity as we know it, is composed of two separate phenomena... One of which varies in strength as 1/r2, the other as 1/r ?
Fg = GMm/r2 + G' Mm/r
So you could explain MOND, if you could explain what two separate phenomena, explained each of the two terms?
Relatedly, what GR like equation, would have a 1/r weak field limit? The standard GR equation has a 1/r2 limit... What modified form of the GR equation would generate weak field 1/r like forces ?
TEFLing said:MOND can be construed as claiming, that at large distances, i.e. long range, gravity switches character, from 1/r2 to 1/r
TEFLing said:Are there any versions of MOND which posit a transition from 1/r2 to 1/r behavior of the form
Fg = GMm/r2 + G' Mm/r
With the former dominating at close range and the latter at galactic scales?
MOND stands for Modified Newtonian Dynamics, which is a theory proposed as an alternative to the widely accepted theory of dark matter. It suggests that the laws of gravity need to be modified on large scales in order to explain the observed rotation curves of galaxies.
The bullet cluster is a galaxy cluster that underwent a collision between two subclusters. The distribution of the hot gas and the dark matter in this cluster were found to be spatially separated, providing evidence for the existence of dark matter. This is important for understanding MOND because it challenges the theory's ability to explain the observed dynamics of galaxy clusters.
The "bullet for MOND" refers to a recent study that analyzed the dynamics of the galaxy cluster Abell 520, which was previously thought to be a counterexample to dark matter. The study found that the observed dynamics of the cluster can be explained by standard dark matter without the need for MOND. This implies that MOND may not be a viable alternative to dark matter.
Galaxy clusters are important for understanding MOND because they allow us to test the theory on a larger scale than individual galaxies. By analyzing the dynamics of galaxy clusters, we can see if MOND can successfully explain the observed motions of galaxies on a larger scale. This helps us to determine the validity of the theory.
Yes, there are some observations that have been interpreted as evidence for MOND. For example, the rotation curves of some dwarf galaxies and some spiral galaxies can be explained by MOND without the need for dark matter. However, these observations are still debated and the majority of evidence still supports the existence of dark matter.