The Multifractal Spectra of V-Statistics

Let $(X,T)$ be a topological dynamical system and let $\Phi: X^r \to $\mathbb{R}$$beacontinuousfunctionontheproductspace$X^r= X\times … \times X$($r\ge 1$)\mathrm{.}WeareinterestedinthelimitofV-statisticstaking$\Phi$ as kernel: [\lim_{n\to \infty} n^{-r}\sum_{1\le i_1, …, i_r\le n} \Phi(T^{i_1}x, …, T^{i_r} x).] The multifractal spectrum of topological entropy of the above limit is expressed by a variational principle when the system satisfies the specification property. Unlike the classical case ($r=1$) where the spectrum is an analytic function when $\mathrm{\Phi }$ is H"{o}lder continuous, the spectrum of the limit of higher order V-statistics ($r\ge 2$) may be discontinuous even for very nice kernel $\mathrm{\Phi }$.