1,721,087 research outputs found
Algebraic Proof Systems (Invited Talk)
No full textGiven a set of polynomial equations over a field F, how hard is it to prove that they are simultaneously unsolvable? In the last twenty years, algebraic proof systems for refuting such systems of equations have been extensively studied, revealing close connections to both upper bounds (connections between short refutations and efficient approximation algorithms) and lower bounds (connections to fundamental questions in circuit complexity.)
The Ideal Proof System (IPS) is a simple yet powerful algebraic proof system, with very close connections to circuit lower bounds: [Joshua A. Grochow and Toniann Pitassi, 2018] proved that lower bounds for IPS imply VNP ≠ VP, and very recently connections in the other direction have been made, showing that circuit lower bounds imply IPS lower bounds [Rahul Santhanam and Iddo Tzameret, 2021; Yaroslav Alekseev et al., 2020].
In this talk I will survey the landscape of algebraic proof systems, focusing on their connections to complexity theory, derandomization, and standard proposional proof complexity. I will discuss the state-of-the-art lower bounds, as well as the relationship between algebraic systems and textbook style propositional proof systems. Finally we end with open problems, and some recent progress towards proving superpolynomial lower bounds for bounded-depth Frege systems with modular gates (a major open problem in propositional proof complexity)
Progress in Lifting and Applications in Lower Bounds (Invited Talk)
No full textEver since Yao introduced the communication complexity model in 1979, it has played a pivotal role in our understanding of limitations for a wide variety of problems in Computer Science. In this talk, I will present the lifting method, whereby communication lower bounds are obtained by lifting much simpler lower bounds. I will show how lifting theorems have been used to solve many open problems in a variety of areas of computer science, including: circuit complexity, proof complexity, combinatorial optimization (size of linear programming formulations), cryptography (linear secret sharing schemes), game theory and privacy.
At the end of the talk, I will sketch the proof of a unified lifting theorem for deterministic and randomized communication (joint with Arkadev Chattopadyhay, Yuval Filmus, Sajin Koroth, and Or Meir.
Propositional Proof Complexity: A Survey on the State of the Art, Including Some Recent Results
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Exponential Time/Space Speedups for Resolution and the PSPACE-completeness of Black-White Pebbling
No full textAutomatizability and Simple Stochastic Games
Full text linkThe complexity of simple stochastic games (SSGs) has been open since they were dened by Condon in 1992. Despite intensive eort, the complexity of this problem is still unresolved. In this paper, building on the results of [4], we establish a connection between the complexity of SSGs and the complexity of an important problem in proof complexity{the proof search problem for low depth Frege systems. We prove that if depth-3 Frege systems are weakly automatizable, then SSGs are solvable in polynomial-time. Moreover we identify a natural combinatorial principle, which is a version of the well-known Graph Ordering Principle (GOP), that we call the integer-valued GOP (IGOP). This principle states that for any graph G with nonnegative integer weights associated with each node, there exists a locally maximal vertex (a vertex whose weight is at least as large as its neighbors). We prove that if depth-2 Frege plus IGOP is weakly automatizable, then SSG is in P. Supported by NSERC.
An Exponential Separation between the Matching Principle and the Pigeonhole Principle
No full textThe combinatorial matching principle states that there is no perfect matching on an odd number of vertices. This principle generalizes the pigeonhole principle, which states that for a fixed bi-partition of the vertices, there is no perfect matching between them. Therefore, it follows from recent lower bounds for the pigeonhole principle that the matching principle requires exponential-size bounded-depth Frege proofs. Ajtai [Ajt90] previously showed that the matching principle does not have polynomial-size bounded-depth Frege proofs even with the pigeonhole principle as an axiom schema. His proof utilizes nonstandard model theory and is nonconstructive. We improve Ajtai's lower bound from barely superpolynomial to exponential and eliminate the nonstandard model theory. Our lower bound is also related to the inherent complexity of particular search classes (see [Pap91]). In particular, oracle separations between the complexity classes PPA and PPAD, and between PPA and PPP also follow f..
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