As health care costs mount and the Affordable Care Act begins to take hold, one aspect of the sweeping law has divided Georgia’s medical community and politicians.Under the law, also known as “Obamacare,” all states have the option of expanding Medicaid, a program jointly funded by the federal government and states that provides health-care benefits for some low-income individuals and families. Expansion would mean that anybody earning 133 percent of the federal poverty level or less would be eligible for Medicaid. In Georgia, that would mean about 650,000 more people would be added to the Medicaid rolls, which already have about 1.7 million people.