Analysis of Boolean Functions
Prof. Ryan O'DonnellResearch-level course developing Fourier analysis over the Boolean hypercube, hypercontractivity, noise stability, invariance principles, and applications to hardness of approximation and social choice.
Syllabus
20Lecture 1: The Fourier Expansion and Basic Formulas (15-859)
This lecture introduces the Fourier expansion for Boolean functions, a foundational concept, and derives basic formulas relevant to its application in theoretical computer science.
Lecture 2: Probability Densities and BLR Linearity Testing (15-859)
This session explores probability densities and convolution in the context of Boolean functions, culminating in an examination of the Blum-Luby-Rubinfeld (BLR) linearity testing algorithm.
Lecture 3: Social Choice and Influences (15-859)
This lecture connects Boolean function analysis to social choice theory, exploring the concept of influences and their implications for collective decision-making processes.
Lecture 4: Noise Stability and Arrow's Theorem (15-859)
This session delves into noise stability for Boolean functions and its relation to Arrow's Impossibility Theorem, demonstrating profound connections between robust computation and social choice.
Lecture 5: Spectral Concentration and Learning (15-859)
This lecture investigates spectral concentration phenomena in Boolean functions and its utility in learning algorithms, specifically examining how spectral properties aid in function approximation.
Lecture 6: Restrictions and the Goldreich-Levin Theorem (15-859)
This session covers the concept of restrictions on Boolean functions and details the Goldreich-Levin Theorem, a cornerstone result in cryptography for extracting hard-core predicates.
Lecture 7: DNF Formulas (15-859)
This lecture focuses on Disjunctive Normal Form (DNF) formulas, exploring their properties and relevance in the analysis of Boolean functions, including complexity and learning aspects.
Lecture 8: Linial-Mansour-Nisan Theorems (15-859)
This session meticulously examines the Linial-Mansour-Nisan (LMN) Theorems, crucial results that relate the complexity of Boolean functions to their Fourier spectrum.
Lecture 9: Majority, LTFs, and the CLT (15-859)
This lecture explores the properties of Majority functions and Linear Threshold Functions (LTFs), linking them to the Central Limit Theorem (CLT) for approximating sums of random variables.
Lecture 10: LTFs and Noise Stability (15-859)
This session further develops the understanding of Linear Threshold Functions (LTFs) by analyzing their noise stability properties, a critical aspect for robust computation and learning.
Lecture 11: Level-1 Inequality and the 2/π Theorem (15-859)
This lecture introduces the Level-1 inequality and the precise 2/π Theorem, exploring their roles in characterizing the Fourier spectrum of Boolean functions, particularly for 'reasonable' random variables.
Lecture 12: Bonami's Lemma and the KKL Theorem (15-859)
This session presents Bonami's Lemma and the pivotal KKL (Kahn-Kalai-Linial) Theorem, which establishes a fundamental lower bound on the influence of variables in Boolean functions.
Lecture 13: Dictator Testing and the FKN Theorem (15-859)
This lecture introduces dictator testing, a crucial technique in property testing, and presents the Friedgut-Kalai-Naor (FKN) Theorem concerning functions with small influences.
Lecture 14: Probabilistically Checkable Proofs of Proximity (15-859)
This session introduces Probabilistically Checkable Proofs of Proximity (PCPPs), an advanced concept extending PCPs to property testing for proximity to a specific language or property.
Lecture 15: Constraint Satisfaction Problems (15-859)
This lecture explores Constraint Satisfaction Problems (CSPs), examining their structure, complexity, and how Boolean function analysis can be applied to understand their solvability and hardness.
Lecture 16: Håstad's Hardness Theorems (15-859)
This session rigorously presents Håstad's hardness theorems, landmark results demonstrating the optimality of certain approximation algorithms for fundamental CSPs.
Lecture 17: UG-Hardness Results from Dictator Tests (15-859)
This guest lecture details UG-hardness results derived from dictator tests, showcasing how these concepts contribute to proving the inapproximability of specific optimization problems.
Lecture 18: The Hypercontractivity Theorem (15-859)
This lecture focuses on the Hypercontractivity Theorem, a powerful tool in probability and functional analysis with broad applications in theoretical computer science and spectral graph theory.
Lecture 19: Invariance Theorems (15-859)
This session covers invariance theorems, which elucidate how the structure of Boolean functions can be preserved under certain transformations, providing insights into their robustness and universality.
Lecture 20: Majority Is Stablest Theorem (15-859)
This final lecture presents the seminal "Majority Is Stablest" Theorem, demonstrating that the Majority function is maximally stable against noise, a key result in robust statistics and theoretical computer science.



















