早期宇宙中的膨胀子优势稀释了暗物质遗迹丰度
Dilaton dominance in the early Universe dilutes Dark Matter relic abundances
摘要：
暗子场的作用及其与物质的耦合可能导致暗物质（DM）遗迹密度的稀释。这与经典的场景形成对比，在经典的场景中，由于膨胀率的修改，遗迹密度增加，因为宇宙在DM去耦时不是辐射主导的。此外，膨胀子场还通过与尘埃的耦合作用影响遗迹密度，使遗迹丰度降低。因此，两个独立的机制相互竞争，导致，在一般情况下，减少的遗迹密度。如果直接暗物质实验指向小的中性伴子-核子截面，这意味着小的中性伴子湮灭率和大的遗迹密度，至少在流行的超对称场景中，这个特征可能是受欢迎的，可以挽救这种情况。在存在稀释机制的情况下，可以满足两个实验约束。在非临界弦论的背景下，已经研究了介子在这种机制中的作用，但在这项工作中，我们遵循一个相当普遍的方法，假设介子只在大爆炸核合成之前的早期时代占主导地位。
英文摘要：
The role of the dilaton field and its coupling to matter may result to a dilution of Dark Matter (DM) relic densities. This is to be contrasted with quintessence scenarios in which relic densities are augmented, due to modification of the expansion rate, since Universe is not radiation dominated at DM decoupling. Dilaton field, besides this, affects relic densities through its coupling to dust which tends to decrease relic abundances. Thus two separate mechanisms compete each other resulting, in general, to a decrease of the relic density. This feature may be welcome and can rescue the situation if Direct Dark Matter experiments point towards small neutralino-nucleon cross sections, implying small neutralino annihilation rates and hence large relic densities, at least in the popular supersymmetric scenarios. In the presence of a diluting mechanism both experimental constraints can be met. The role of the dilaton for this mechanism has been studied in the context of the non-critical string theory but in this work we follow a rather general approach assuming that the dilaton dominates only at early eras long before Big Bang Nucleosynthesis.
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