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My view on the constant speed of stars orbiting around the centre of the galaxy is this: the density of stars is such that a ball (same centre as the ghalaxy) with radius $r$ has to contain mass directly proportional to $r$. As long as the mass outside the ball is distributed evenly enough, that outside objects' mass's gravitational effects cancels ...


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These are models that extend/modify the theory of general relativity: In theoretical physics, massive gravity is a theory of gravity that modifies general relativity by endowing the graviton with a nonzero mass. In the classical theory, this means that gravitational waves obey a massive wave equation and hence travel at speeds below the speed of light. ...


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You are asking if one of these theories is "more correct" than the other. That is a somewhat philosophical question. You can surely believe that a theory "makes more sense" than another, but this has more to do with your personal preference. Correctness in modern science is a matter of agreement with experimental observation. And at the moment there is no ...


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Dark matter is uncharged, it might be its own antiparticle. No relationship to matter and antimatter, where mainly its charge conjugation and parity. we don't know that dark matter has any antiparticle broken symmetry. And there is no known relationship between matter and dark matter, except they interact gravitationally and maybe through weak interactions....


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No way, amount of dark matter is estimated to be 4 times the amount of normal matter. Even if we ignore all other arguments, it still does not restore the symmetry. Dark matter (if there is such a thing), is actually transparent matter (we can not see it) and cold matter (it does not absorb/emit any heat/radiation). That also means that you can not measure ...


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No, we know enough of the "bulk properties" of antimatter to rule this out. Antimatter interacts with the electromagnetic field in exactly the same way as regular matter, just with the opposite charge. Therefore, antimatter should be detectable using most of the techniques we use to detect regular matter in astronomy. This works even if the antimatter is a ...


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I think we can pretty safely say this is not the case. The main reason is that we have a pretty good idea of where dark matter is--to some degree, it can be reconstructed from the gravitational influence it has on surrounding matter. The dark matter appears to be distributed evenly throughout the galaxy. Thing is, a galaxy is pretty "dirty," as far as space ...


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Like it was said before, there is no a priori reason why nature should treat everything symmetrically. Much to the contrary, we know several examples of P- and CP-violating processes. And in other cases we do not even know the reason why a process is "symmetric", when in principle it would be allowed to violate CP (see: the strong CP problem). I guess you ...


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There's not reason to assume nature should treat everything symmetrically. There are many phenomena in nature that we actually know are asymmetric. For example the weak force violates parity symmetry (meaning the weak force has a preference for right or left handedness).


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Dark matter might be matter which has no protons or neutrons, more like pure energy than the kind of matter which is familiar to us ... kind of like the "GEONs" which John Archibald Wheeler proposed, speculatively, many years ago (see his book Geons, Black Holes & Quantum Foam for details). Because it contains energy, and because energy is ...


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The rotation curve exists because of he presence of dark matter and baryonic matter. And we can estimate it using the orbital velocity of the Sun and its distance from the Galactic Centre. The fact that we can do that demonstrates that we can estimate the interaction generated by Dark Matter. That is how its existence was initially suggested. We knew the ...


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The answer is that we do not know. It is a working assumption that it does, and it is this assumption that leads to an estimate of the total mass and how that mass is distributed - essentially by the application of Poisson's equation for gravitation. $$ \nabla^2 \Phi(r) = 4 \pi G \rho(r) $$ If for some reason dark matter did not couple gravitationally in ...


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We assume that gravity couples to the stress-energy tensor i.e. the Einstein equation relates the curvature to the stress-energy tensor. In cosmology the only important terms in the stress-energy tensor are the diagonal terms $T_{00}$, $T_{11}$, $T_{22}$ and $T_{33}$. The $T_{00}$ term is the energy density i.e. how much stuff there is per unit volume - note ...


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It is highly unlikely. Neutrinos are known to account for a small part. The problem with neutrinos is that they are low mass and usually highly relativistic. DM needs to be made up of particles or objects that are slow and non relativistic. DM concentrates around galaxies, and tends to stay around, DM needs to be cold to stay around. As for cosmic rays it'...


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Well, first of all, that's not the NFW profile, instead you should have: $$\rho(r) = \frac{\rho_0}{\frac{r}{r_s}(1+\frac{r}{r_s})^2}$$ The radius $r_s$ is usually called the scale radius, and is the place where the logarithmic derivative of the density is $-2$. This isn't especially physically meaningful, but is mathematically convenient. The integral is ...


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On top of the other excellent answers I'd like to point out that the accretion rate of dark matter particles is believed to be much smaller. The reason matter in accretion disk is being accreted rapidly is because they lose energy from electromagnetic radiation. For dark matter particles, in practice the only way it can be accreted is if the particle ...



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