Breakthrough Tracker record
An explicit construction disproves the undirected multiple-unicast conjecture
Braverman and He construct an undirected network with 157 independent sessions whose linear network-coding rate is at least 1 while fractional multicommodity flow is at most 147/157, and use amplification to obtain a polylogarithmic coding gap.
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- Stable ID
cs-undirected-multiple-unicast-counterexample-2026- Revision
cs-undirected-multiple-unicast-counterexample-2026.v1- Field
- Theoretical computer science · Network coding, information theory and theoretical computer science
- Evidence
- Tier 1 · Peer reviewed: No
- Record state
- Provisional · Explicit verifier-backed preprint counterexample
- Last checked
AI role
The authors report that GPT-6 found a nondeterministic design. They converted it into a causal construction, applied orientation and local search, and supplied an exact symbolic verifier and simulator.
Record details
- Problem or result
- Undirected multiple-unicast network-coding conjecture
- Authors
- Mark Braverman and Zhongtian He
- Institutions
- Princeton University
- Result date
- Preprint submitted October 7, 2026
Why it matters
The paper supplies a finite explicit witness against a long-standing network-coding conjecture rather than only an existential separation.
Limits
The executable checker is author-supplied rather than an independent replication, the amplified family depends on the cited theorem, and the large construction has not been peer reviewed or independently replayed in the sources checked.
Sources
- Primary: Braverman and He multiple-unicast counterexample
- Verification artifact: Counterexample symbolic verifier and simulator
Correction and revision history
- 2026-10-19 — Added after primary-source, scope, status, AI-role and limitation review.
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