Name: Sun Qingfeng Date: 12/09/14-08:50:29 AM Z


In[1] $Assumptions = {test > 1}
In[2] tmp = Sqrt[test - 1]
In[3] Calc[tmp (Pair[LorentzIndex[\[Beta]], LorentzIndex[\[Beta]1]]) (Pair[
       LorentzIndex[\[Beta]], LorentzIndex[\[Beta]1]])]
Out[3] 4 I Sqrt[1-test]
In[4] Calc[tmp (Pair[LorentzIndex[\[Beta]], LorentzIndex[\[Beta]1]]) (Pair[
     LorentzIndex[\[Beta]], LorentzIndex[\[Beta]1]])] // Simplify
Out[4] -4 Sqrt[test-1]

PS: My Mathematica version: 8.0
FeynCalc Version: 8.20 patched with FeyArts 3.7