mUMBAI, Aug. 28 -- The BSE Sensex, briefly plunged about 3% during a 20-minute closing auction on Thursday, exacerbating concerns over thin liquidity and manipulation during the window. At one point, the 30-stock index slumped to 74,983.19 points, 2.9% lower than the level of 77,182.91 at 3.15pm, according to the bourse's data. The gauge recovered nearly all of the losses to eventually close 0.7% lower for the day. P13...