# Does Dark Matter have more space-time or particle characteristics?

Dark Matter appears to have more in common with phenomena related to spatial geometry then a particle. I thought in General Relativity, space can be curved without the presence of matter so gravitational lensing does not imply there is matter present but that the space in a region is curved. If Dark matter has more characteristics related to spatial geometry, why is it referred to as a kind of exotic particle (WIMP).

-
possible duplicate: physics.stackexchange.com/questions/29459/… –  Michael Brown Mar 25 '13 at 3:26
There are 2 popular approaches to this puzzle called the dark matter problem. First is through a modification to general theory of relativity as you had suggested. The second is through postulating presence of an unseen particle. I would suspect an unseen particle is the more likely reason for observed experimental discrepancies like galaxy rotation curves being flatter than expected. –  Prathyush Mar 25 '13 at 3:46

But spacetime, according to GR, is constrained by the mass, energy, momentum, pressure, and shear. The equation we write down is $$G_{\mu\nu} = 8\pi T_{\mu\nu},$$ which unfortunately means almost nothing if you don't already know GR, but it just feels so good to write down people like me can't help it sometimes. Basically, the left side encompasses curvature and all that, while the right deals with the "stuff." Inferences about curvature therefore tell us something about the "stuff" there.