SWEET SCIENCE The fighters of Ardon Sweet Science Gym have personal stories of struggle, redemption, perseverance and excellence — inside and outside the ring — set against the backdrop of rapid gentrification in Brooklyn. While almost every boxing gym is filled with some of those stories, Greg Ardon’s gym is different because of the diversity of the people and the tales they have to tell. Some of Ardon’s fighters were born in the neighborhood, which used to be called Sunset Park but is now being rebranded by realtors as Greenwood Heights. Many of them, however, converged here from around the world: Mexico, Iran, St. Thomas, Palestine, the Dominican Republic, Poland and Russia. Ardon understands what they're going through. He is from El Salvador and grew up in Park Slope-before it was a haven for baby strollers and coffee shops. When Ardon's fighters aren’t at the gym training, they’re cutting hair, saving suicidal people from jumping off bridges, studying history, cuffing criminals, bussing tables, stocking shelves at a super market, and finding clever ways to train while playing with their children. These same fighters might spar any given day, and the stories of struggle are as rife as the stories of sustained achievement. In the past year, hundreds of millions of dollars have changed hands in local real estate deals within a few blocks of this enclave. Architects are drawing up luxury condos, Industry City and the Brooklyn Nets are transforming the waterfront. This is the portrait of the people that created a community within a community that is fighting over what the word "community" even means.