A Danbury philanthropist who co-founded the Subway sandwich chain has died at the age of 90.  Peter Buck studied nuclear physics at Columbia University, where he obtained masters and doctoral degrees. He work for General Electric and Nuclear Energy Services.  Forbes has long ranked Buck among Connecticut’s wealthiest residents.  The Peter and Carmen Lucia Buck Foundation listed assets of $577 million and made numerous gifts to nonprofits in Danbury.  Danbury Hospital has also been one beneficiary of his charitable donations with a $30 million gift to build a new patient-care building for the hospital. Subway is the world’s largest chain by locations, and trails only Starbucks and McDonald’s for global revenue.  Buck's $1,000 investment in a family friend’s Connecticut sandwich shop in 1965 provided the genesis for what is now the world’s largest restaurant chain.