Why is DC sqrt(2) higher than AC after rectifing?
The reason is that AC voltages are most often represented in terms of RMS.  So the peak voltage of a 120VAC (rms) signal is higher than 120V, it is ~170V.  When you rectify and assuming there is some bulk capacitor to store the peaks, you will see that voltage in DC.  The concept of RMS is that the 120Vrms AC source should have the same power flowing as 120VDC, even though the peak voltage is 170V.