我們探討K. Dienes and B. Thomas所提出的Dynamical Dark Matter(DDM)模型。這個模型提出一種可能：宇宙中的暗物質不只有一種，而是數量龐大的一系列具有不同質量的粒子。在特定條件下，這些粒子可以不同的生命期衰變，而不致與現有的觀察衝突。因為暗物質粒子會先後發生衰變，在DDM模型裡，宇宙暗物質的總數可以隨時間而變化。兩位作者並提出一個具體的額外維度的模型，加上一個特定的暗物質產生起始機制：Misalignment Production來實踐DDM的構想。我們討論並澄清他們所作的簡化假設及所使用的計算方法。同時嘗試以Thermal Production來作為暗物質的起始產生機制，計算暗物質的總量，並與兩位作者的結果比較。

We study the Dynamical Dark Matter(DDM) model proposed by K. Dienes and B. Thomas. This model involves the possibility that the Dark Matter (DM) in the universe consist of not just one kind but a huge number, a whole series of particles with varying masses. Under certain conditions, these DM particles can be allowed to decay with varying decay width without conflicting with current observation data. Since DDM particles decays successively, the total DM abundance in the universe will change with time. To realize this idea, the two authors proposed a concrete Extra Dimension model plus one initial DDM particle production mechanism: Misalignment Production. We consider and clarify their assumptions and methods. At the same time, we try to use an alternative Thermal Production to replace Misalignment Production and formulate the calculation of the total DM abundance.

[1] K. R. Diens and B.Thomas. Dynamical Dark Matter: I.
Theoretical Overview. Phys. Rev. D 85,083523 (2012)
[arXiv:1106.4546v2[hep-ph]]

[2] H. C. Cheng,arXiv:1003.1162v1[hep-ph] (2010)

[3] S. Dodelson, Modern cosmology ,Academic press (2003)

[4] K.A. Olive,arXiv:1005.3955v1[hep-ph] (2010)

[5] U.A.Yajnik,arXiv:0808.2236v1[hep-ph](2008)

[6] G. Bertone, D. Hooper and J. Silk, arXiv:0606175v2[hep-ph](2004)