mumbai, Dec. 15 -- India's capital markets regulator is likely to reduce margins on equity derivatives on non-expiry days to encourage big traders to place longer-term bets rather than focus solely on the expiration day, said two people aware of the development. A margin is the amount that an investor must pay upfront to initiate a trade in the derivatives segment. The Securities and Exchange Board of India's (SEBI's) move to cut these margins could deepen the derivatives markets, where most of the trading by large, high-frequency and proprietary traders as well as individual investors takes place on the expiry day of weekly option contracts. "The RMRC (SEBI's risk management and review committee) is discussing a rationalisation of margins ...