Noise Sensitivity Governed by Continuous-Time Random Walks on the Symmetric Group

Abstract

We study the noise sensitivity of Boolean functions on the symmetric group, where noise is induced by running a Markov chain on the symmetric group $S_n$, focusing in particular on the case where the underlying chain is an interchange process on the complete graph $K_n$, the $d$-dimensional discrete torus or the star graph. We prove comparison results between these noise sources. We also show that the indicator of long cycles is noise-sensitive under the interchange process on each of the aforementioned graphs. In addition, we study the noise sensitivity of several fundamental functions such as the parity function and analogues of the dictator function. Furthermore, using the fact that the interchange process on the complete graph is the continuous-time random walk generated by all transpositions, we prove that noise sensitivity remains unchanged when the noise source is switched from the continuous-time random walk generated by all transpositions to that generated by all $s$-cycles ($s$ is even and $2<s\ll n$).