Stock indexes didn't do much at first glance Monday, but the modest move for the Standard & Poor's 500 masked some dramatic changes roiling underneath the surface. Telecom stocks, banks and other areas of the market that stand to benefit the most from Washington's drive to cut corporate tax rates jumped. At the same time, technology stocks slumped, giving up a chunk of the gains that have made them the best-performing part of the market by far this year. The New York Stock Exchange was nearly evenly split between stocks that rose and fell, and the split in performance left the S&P 500 close to where it began the day. It ended down 2.78 points, or 0.1%, at 2,639.44. The Dow Jones industrial average rose 58.46, or 0.2%, to 24,290.05, and the Nasdaq composite slid 72.22, or 1.1%, to 6,775.37. The cross-currents swept through the market on the first day of trading after the Senate narrowly approved its proposal to revamp the tax system. Indexes initially jumped on expectations that lower tax rates would help corporate profits pile up even higher, and the S&P 500 was up as much as 0.9% in morning trading. Lower tax rates would help boost profits for companies, which already have been reporting resurgent earnings growth this year thanks to the improving global economy. If profits do accelerate, that would help allay worries that the stock market — which is still close to record highs — has climbed too far, too quickly. Telecommunications companies pay some of the highest effective tax rates among the big companies in the S&P 500, so they stand to reap some of the biggest rewards of lower tax rates. Telecom stocks in the index jumped 1.6%, tied for the biggest gain of the 11 sectors in the index. Financial stocks, which analysts also expect to be winners from the tax overhaul, likewise climbed 1.6%. Technology companies, meanwhile, probably would get less of a boost. They already were typically paying the lowest effective tax rates of the 11 sectors in the S&P 500, analysts said. Tech stocks in the index dropped 1.9%, lagging far behind the rest of the market. It's a very different position for the sector, which has risen nearly twice as much as the overall S&P 500