Structure Of Boolean Almost Low Degree Functions On The Biased Cube
Yuval Filmus (Technion - Israel Institute of Technology)
https://simons.berkeley.edu/talks/yuval-filmus-technion-israel-institute-technology-2023-07-28
Structural Results
The FKN theorem states that if a Boolean function on the Boolean cube is close to degree 1, then it is close to a dictator.
Similarly, the KindlerโSafra theorem states that if a Boolean function on the Boolean cube is close to degree d, then it is close to a junta.
The picture becomes more interesting when we study functions on the p-biased Boolean cube.
If a Boolean function is ๐-close to degree 1, then (up to negation) it is O(๐)-close to a maximum of O(โ๐/p+1) coordinates, and so O(โ๐+p)-close to a constant function.
A similar statement holds for functions close to degree d, but the corresponding structure is more complicated.
Another setting we might discuss is functions on the symmetric group.
If a Boolean function is ๐-close to degree 1, then it is O(โ๐)-close to a dictator (suitably defined), and O(๐)-close (up to negation) to a union of โmostly disjointโ cosets.
A similar statement should hold for degree d, where the function ought to be close to a (suitably defined) decision tree of depth poly(d).
Joint work with Irit Dinur (Weizmann Institute) and Prahladh Harsha (TIFR).