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Revision #2 to TR26-187 | 3rd November 2026 15:44

An Explicit Optimal Separation of BPP from NP in Number-on-Forehead Communication Complexity

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Revision #2
Authors: Yimeng Wang, Haoyu Wang, Pei Wu
Accepted on: 3rd November 2026 15:44
Downloads: 19
Keywords: 


Abstract:

For every fixed $k\ge3$, we construct an explicit total Boolean function in the $k$-player number-on-forehead model with public-coin randomized communication complexity $O_k(1)$ and nondeterministic communication complexity $\Omega_k(n)$, where $n$ is the number of bits on each forehead. For three players, our construction improves the strongest previously known explicit separation, due to Kelley and Lyu (FOCS 2025) building on Kelley, Lovett, and Meka (STOC 2024), from constant randomized versus $\Omega(n^{1/2})$ nondeterministic communication to the optimal constant versus linear separation. Our construction uses algebraic geometry codes to preserve the nondeterministic hardness of generalized inner product while enabling a randomized protocol with constant communication.


Revision #1 to TR26-187 | 2nd November 2026 18:25

An Explicit Optimal Separation of BPP from NP in Number-on-Forehead Communication Complexity





Revision #1
Authors: Yimeng Wang, Haoyu Wang, Pei Wu
Accepted on: 2nd November 2026 18:25
Downloads: 13
Keywords: 


Abstract:

For every fixed $k\ge3$, we construct an explicit total Boolean function in the $k$-player number-on-forehead model with public-coin randomized communication complexity $O_k(1)$ and nondeterministic communication complexity $\Omega_k(n)$, where $n$ is the number of bits on each forehead. For three players, our construction improves the strongest previously known explicit separation, due to Kelley and Lyu (FOCS 2025) building on Kelley, Lovett, and Meka (STOC 2024), from constant randomized versus $\Omega(n^{1/2})$ nondeterministic communication to the optimal constant versus linear separation. Our construction uses algebraic geometry codes to preserve the nondeterministic hardness of generalized inner product while enabling a randomized protocol with constant communication.


Paper:

TR26-187 | 17th September 2026 09:16

An Explicit Optimal Separation of BPP from NP in Number-on-Forehead Communication Complexity





TR26-187
Authors: Yimeng Wang, Haoyu Wang, Pei Wu
Publication: 17th September 2026 14:40
Downloads: 693
Keywords: 


Abstract:

For every fixed $k\ge3$, we construct an explicit total Boolean function in the $k$-player number-on-forehead model with public-coin randomized communication complexity $O_k(1)$ and nondeterministic communication complexity $\Omega_k(n)$, where $n$ is the number of bits on each forehead. This extends the explicit three-player separations of Kelley, Lovett, and Meka (STOC 2024) and Kelley and Lyu (FOCS 2025) to every fixed number of players, and as a side product improves the three-player nondeterministic lower bound from $\Omega(n^{1/2})$ to the optimal $\Omega(n)$. Our construction is based on algebraic geometry codes.



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