Key equity indices jumped on Wednesday, as investors piled into beaten-down stocks amid expectations of robust corporate earnings for the second quarter ended September.The S&P BSE Sensex vaulted over 400 points, while the NSE's Nifty surged 135 points after last week's hammering.The gains were led by banking, auto and finance stocks."Markets have corrected, hence we are seeing value buying. The positivity may also be attributed to expectations of robust Q2 results," Astha Jain, Senior Analyst Hem Securities, told IANS.At 1.11 p.m., the broader Nifty50 of the National Stock Exchange was trading at 10,437.30, up 136.25 points or 1.32 per cent from its Tuesday's close.The Sensex, which had opened at 34,493.21, was trading at 34,715.87, up 416.40 points or 1.21 per cent.So far, the Sensex has touched an intra-day high of 34,771.10 points and a low of 34,346.50.