标题： 变色龙暗物质的静态结构作为矮椭圆星系核心的解释 显示英文标题

标题： Static structure of chameleon dark Matter as an explanation of dwarf spheroidal galactic core

摘要： 我们提出了一种新的机制，用以解释最近观测到的富含暗物质的矮椭球星系中的核心型暗物质密度分布。 在我们的场景中，由于暗物质粒子与一种变色龙标量的相互作用，在矮星系向其中心靠近的过程中，暗物质粒子质量会逐渐减小。 在更靠近星系中心的地方，吸引性的标量第五力变得比引力强得多，并被暗物质云的费米压力所平衡，从而得到了暗物质晕的平衡静态构型。 类似于孤子星或费米子Q星的情况，当标量达到静态分布并远离星系中心时，暗物质晕的稳定性得以实现。 对于简单的标量-暗物质相互作用和二次标量自相互作用势，我们表明，暗物质的行为在距离星系中心几$\rm{kpc}$之外的地方完全类似于冷暗物质（CDM），但在更近的距离上，暗物质变得更轻，费米压力不能忽略。 利用托马斯-费米近似，我们数值求解了标量场、费米子质量和暗物质能量密度随距离的变化径向静态分布。 我们发现，对于由超轻标量介导的第五力，有可能在星系中心附近获得平坦的暗物质密度分布。 在我们的场景中，距离星系中心$ r \geq 1\, \rm{kpc}$处可以忽略第五力，而在这一距离之外，暗物质可以简单地被视为重的非相对论性粒子，从而再现了CDM在大尺度上的成功。 显示英文摘要

摘要： We propose a novel mechanism which explains cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of dark matter cloud, thus an equilibrium static configuration of dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the galactic center. For simple scalar-dark matter interaction and quadratic scalar self interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond few $\rm{kpc}$ away from galactic center but at closer distance it becomes lighter and fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultra light scalar, it is possible to obtain a flattened dark matter density profile towards galactic center. In our scenario, the fifth force can be neglected at distance $ r \geq 1\, \rm{kpc}$ from galactic center and dark matter can be simply treated as heavy non-relativistic particles beyond this distance, thus reproducing the success of CDM at large scales.