contacting advisor before admission can be helpful? I am an Mphil student from India. My field of interest is complex analysis. I plan to go abroad for my PhD. I know the process of GRE exams and all. But I want to ask, is talking to any professor, with whom you wish to work for PhD, from your desired university, helpful in getting admission? 
Can it be helpful somehow?
You could certainly talk with them and discuss your ideas and options and if you find the connection is a good one you could ask for a letter of recommendation from them, but short of a letter I don't think a professor has a whole lot of flex/power when it comes to admissions. 

Certainly if they vouch for you that is a positive thing, but unlike a "job" I feel the role at the University is based more on your academic experience and aptitude than who you know.