eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2024-09-16
71:1
71:17
10.4230/LIPIcs.APPROX/RANDOM.2024.71
article
Approximate Degree Composition for Recursive Functions
Chakraborty, Sourav
1
https://orcid.org/0000-0001-9518-6204
Kayal, Chandrima
1
Mittal, Rajat
2
Paraashar, Manaswi
3
https://orcid.org/0009-0005-3805-5095
Saurabh, Nitin
4
Indian Statistical Institute, Kolkata, India
Indian Institute of Technology Kanpur, India
University of Copenhagen, Denmark
Indian Institute of Technology Hyderabad, India
Determining the approximate degree composition for Boolean functions remains a significant unsolved problem in Boolean function complexity. In recent decades, researchers have concentrated on proving that approximate degree composes for special types of inner and outer functions. An important and extensively studied class of functions are the recursive functions, i.e. functions obtained by composing a base function with itself a number of times. Let h^d denote the standard d-fold composition of the base function h. The main result of this work is to show that the approximate degree composes if either of the following conditions holds:
- The outer function f:{0,1}ⁿ → {0,1} is a recursive function of the form h^d, with h being any base function and d = Ω(log log n).
- The inner function is a recursive function of the form h^d, with h being any constant arity base function (other than AND and OR) and d = Ω(log log n), where n is the arity of the outer function.
In terms of proof techniques, we first observe that the lower bound for composition can be obtained by introducing majority in between the inner and the outer functions. We then show that majority can be efficiently eliminated if the inner or outer function is a recursive function.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol317-approx-random2024/LIPIcs.APPROX-RANDOM.2024.71/LIPIcs.APPROX-RANDOM.2024.71.pdf
Approximate degree
Boolean function
Composition theorem