Indian benchmark indices opened on a flat to negative note on Tuesday, reflecting a cautious sentiment across domestic markets. According to the indices, the Sensex traded at 83,224.93, down by 21.25 points or 0.03 per cent, while the Nifty 50 stood at 25,574.55, declining 10.95 points or 0.04 per cent as of 9:17 am.