Retirement, as portrayed in TV commercials, is the time to indulge a passion, whether tennis, enjoying more time with a spouse, frequent socializing, or civic engagement. Boston University sociologist Deborah Carr isn’t buying this idealized picture of aging. “This gilded existence is not within the grasp of all older adults,” she argues in “Golden Years? Social Inequality in Later Life.” “For those on the lower rungs of the ladder,” she writes, retirement is “marked by daily struggle, physical health challenges and economic scarcity.” Her book, which mines multidisciplinary research on aging, reaches the distressing conclusion that economic inequality not only exists but that it becomes more pronounced as people age and become vulnerable. And this problem will grow and affect…