σ8是在半徑為 8 h-1 Mpc 的球內物質分佈功率譜的均方根線性漲落,即(White,Efstathiou & Frenk 1993)。σ8的倒數被定義為偏差參數(bias parameter)(Evrard 1989)。
參考文獻
編輯- Evrard, August E. Biased Cold Dark Matter Theory: Trouble from Rich Clusters?. ApJ Letters. 1989, 341: L71. Bibcode:1989ApJ...341L..71E. doi:10.1086/185460.
- White, S. D. M.; Efstathiou, G.; Frenk, C. S. The amplitude of mass fluctuations in the universe. MNRAS. 1993, 262 (4): 1023–1028. Bibcode:1993MNRAS.262.1023W. doi:10.1093/mnras/262.4.1023.