Dark matter (DM) may be studied through the motion of objects following nongeodesic trajectories either due to the existence of an extra mass as a projection of higher dimensions onto lower ones or as motion of dipolar particles and fluids in the halos of spiral galaxies. The effect of DM has been extended nearby the core of the galaxy by means of the excess of mass appearing in the motion of fluids in the accretion disc. Nongeodesic equations and those of their deviation are derived in the presence of different classes of bimetric theories of gravity. The stability of these trajectories using the geodesic deviation technique is investigated.

中文翻译：

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暗物质：运动问题

暗物质（DM）可以通过遵循非大地轨道的物体运动来研究，这可能是由于存在额外的质量（作为高维投影到低维的投影），或者是由于双旋粒子和流体在旋涡星系晕圈中的运动。DM的作用已通过积聚盘中流体运动中出现的过量质量而扩展到银河系核心附近。非大地方程及其偏差方程是在存在不同类别的双度量引力理论的情况下得出的。使用测地线偏差技术研究了这些轨迹的稳定性。