On the scaling of probability density functions with apparent power-law exponents less than unity

We derive general properties of the finite-size scaling of probability density functions and show that when the apparent exponent τ̃ of a probability density is less than 1, the associated finite-size scaling ansatz has a scaling exponent τ equal to 1, provided that the fraction of events in the universal scaling part of the probability density function is non-vanishing in the thermodynamic limit. We find the general result that τ ≥ 1 and τ ≥ τ̃ . Moreover, we show that if the scaling function G(x) approaches a non-zero constant for small arguments, limx→0 G(x) > 0, then τ = τ̃ . However, if the scaling function vanishes for small arguments, limx→0 G(x) = 0, then τ = 1, again assuming a non-vanishing fraction of universal events. Finally, we apply the formalism developed to examples from the literature, including some where misunderstandings of the theory of scaling have led to erroneous conclusions.