EN
A real-valued Hardy space $H¹_{√}(𝕋) ⊆ L¹(𝕋)$ related to the square root of the Poisson kernel in the unit disc is defined. The space is shown to be strictly larger than its classical counterpart H¹(𝕋). A decreasing function is in $H¹_{√}(𝕋)$ if and only if the function is in the Orlicz space LloglogL(𝕋). In contrast to the case of H¹(𝕋), there is no such characterization for general positive functions: every Orlicz space strictly larger than L log L(𝕋) contains positive functions which do not belong to $H¹_{√}(𝕋)$, and no Orlicz space of type Δ₂ which is strictly smaller than L¹(𝕋) contains every positive function in $H¹_{√}(𝕋)$. Finally, we have a characterization of certain eigenfunctions of the hyperbolic Laplace operator in terms of $H¹_{√}(𝕋)$.