Indian equity benchmarks BSE Sensex and NSE Nifty50 are likely to make a gap-down opening on Monday, tracking weakness across most global peers amid persistent concerns about the resilience of the world economy. Singapore Exchange (SGX) Nifty futures — an early indicator of the Nifty index — fell as much as 109.5 points or 0.6 percent to 17,634.5 ahead of the opening bell on Dalal Street.