Karthekeyan Chandrasekaran Amit Deshpande Santosh Vempala The Limit of Convexity Based Isoperimetry: Sampling Harmonic-Concave Functions http://arxiv.org/abs/0906.2448 2009 CoRR abs/0906.2448 db/journals/corr/corr0906.html#abs-0906-2448 informal publication