Core Concepts

The authors present efficient algorithms for boosting uniformity in quasirandom groups, achieving exponential improvements over previous work.

Abstract

The paper focuses on the communication complexity of multiplying elements from the group H = SL(2, q) in the number-on-forehead model with k parties. The authors prove a lower bound of (t log H)/ck, which is an exponential improvement over previous work and matches the state-of-the-art in the area.

Relatedly, the authors show that the convolution of kc independent copies of a 3-uniform distribution over Hm is close to a k-uniform distribution, again an exponential improvement over previous work which needed ck copies. The proofs are remarkably simple and the results extend to other quasirandom groups.

The authors also generalize previous work on the relationship between (ϵ, k)-uniformity and k-uniformity, showing that any distribution over Hm whose weight-k Fourier coefficients are small is close to a k-uniform distribution. This proof is simpler than previous work in the abelian setting.

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Stats

The authors prove a lower bound of (t log H)/ck for the communication complexity of multiplying k × t elements from the group H = SL(2, q) in the number-on-forehead model with k parties.
The authors show that the convolution of kc independent copies of a 3-uniform distribution over Hm is close to a k-uniform distribution.

Quotes

"The proofs are remarkably simple; the results extend to other quasirandom groups."
"This generalizes previous work in the abelian setting, and the proof is simpler."

Key Insights Distilled From

by Harm Derksen... at **arxiv.org** 09-12-2024

Deeper Inquiries

The techniques developed in this paper, particularly those related to boosting uniformity in quasirandom groups, can be applied to various problems in communication complexity and group theory. One significant application is in the analysis of multiparty communication protocols, where the number-on-forehead model is prevalent. The exponential improvement in lower bounds for communication complexity, as demonstrated in this work, can be leveraged to establish stronger separations between deterministic and randomized protocols. This could lead to new insights into the complexity of other group operations and their implications for cryptographic protocols.
Moreover, the methods used to boost uniformity from k-uniform to 2k-uniform distributions can be adapted to study the mixing properties of other quasirandom groups. By extending the results to different types of groups, researchers can explore the communication complexity of iterated group products in broader contexts, potentially uncovering new relationships between group properties and computational complexity.
Additionally, the simplification of proofs and the generalization of results to other quasirandom groups suggest that these techniques could be useful in studying the representation theory of finite groups, particularly in understanding the behavior of Fourier coefficients in non-abelian settings. This could lead to advancements in the field of non-abelian Fourier analysis, which has applications in various areas, including coding theory and combinatorial designs.

While the results presented in this paper are robust, there are certain limitations and assumptions that could potentially be relaxed or generalized. One key assumption is the requirement for the group H to be quasirandom. Although the results extend to other quasirandom groups, exploring the implications for non-quasirandom groups could yield interesting insights. This would involve investigating the communication complexity of group operations in settings where the quasirandomness condition does not hold, which may lead to different lower bounds or communication protocols.
Another aspect that could be generalized is the dependency on the number of parties k. The current results provide bounds that grow exponentially with k, but it may be possible to derive results that are less sensitive to the number of parties involved. This could involve developing new techniques that allow for more efficient communication protocols in scenarios with a large number of parties, potentially leading to improved performance in practical applications.
Furthermore, the paper primarily focuses on the group SL(2, q) and its properties. Generalizing the results to other classes of groups, such as higher-dimensional groups or groups with specific algebraic structures, could broaden the applicability of the findings. This would require a deeper exploration of the representation theory and Fourier analysis in these contexts, potentially leading to new discoveries in both communication complexity and group theory.

The improved bounds on boosting uniformity in quasirandom groups have several potential applications across various fields. In the realm of communication complexity, the exponential improvement in lower bounds can enhance the design of efficient multiparty protocols, particularly in cryptographic settings where secure communication is paramount. This could lead to more robust protocols for secure multiparty computation, where parties need to jointly compute a function while keeping their inputs private.
In addition, the results can be applied to the development of pseudorandom generators and extractors, which are crucial in cryptography and complexity theory. The ability to boost uniformity efficiently can aid in constructing pseudorandom distributions that are statistically indistinguishable from uniform distributions, thereby enhancing the security of cryptographic systems.
Moreover, the findings can influence the study of randomized algorithms, particularly in scenarios where uniformity plays a critical role in the performance of algorithms. By leveraging the improved bounds, researchers can design algorithms that are more efficient in terms of communication and computation, leading to advancements in fields such as distributed computing and network design.
Finally, the techniques and results from this paper can contribute to the broader understanding of quasirandomness in groups, which has implications in combinatorial design theory and the study of expander graphs. The insights gained from boosting uniformity can lead to new constructions and applications in these areas, further enriching the interplay between group theory, combinatorics, and computational complexity.

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