{ "id": "1606.01064", "version": "v1", "published": "2016-06-03T12:40:47.000Z", "updated": "2016-06-03T12:40:47.000Z", "title": "Hardy spaces for semigroups with Gaussian bounds", "authors": [ "Jacek DziubaƄski", "Marcin Preisner" ], "categories": [ "math.FA", "math.CA" ], "abstract": "Let T_t=e^{-tL} be a semigroup of self-adjoint linear operators acting on L^2(X,mu), where (X,d mu) is a space of homogeneous type. We assume that T_t has an integral kernel T_t(x,y) which satisfies the upper and lower Gaussian bounds: \\frac{C_1}{mu(B(x,\\sqrt{t}))} \\exp(-c_1d(x,y)^2/t)\\leq T_t(x,y) \\leq \\frac{C_2}{\\mu(B(x,\\sqrt{t}))} \\exp(-c_2 d(x,y)^2/t). By definition, f belongs to H^1_L if \\| f\\|_{H^1_L}=\\|\\sup_{t>0}|T_t f(x)|\\|_{L^1(X,\\mu)} <\\infty. We prove that there is a function \\omega(x), 0