Gaussian moat
Let be the ring of Gaussian integers, with norm and Euclidean absolute value . Call a Gaussian prime if is a nonzero non-unit whose only divisors in are units and unit multiples of ; equivalently, is a Gaussian prime exactly when is a rational prime, or with and a rational prime with .
Then there is no infinite sequence of pairwise distinct Gaussian primes such that
Equivalently, for each real let be the graph whose vertex set is the set of Gaussian primes and in which two distinct Gaussian primes are joined by an edge when ; then every connected component of is finite. In particular, for every the component of containing the Gaussian prime is finite, so that only finitely many Gaussian primes can be reached from the origin by steps of length at most through Gaussian primes.
References
Primary source
Additional references
- Wikipedia, Gaussian moat, the article this problem comes from.
Progress summary
The problem remains open: an unverified 2019 paper claims a proof only for Gaussian primes off the coordinate axes.
Basil Gordon posed the question in 1962: can one walk arbitrarily far through Gaussian primes using steps bounded by one fixed length? The general negative answer has not been established.
Known results
- Jordan and Rabung constructed a -moat in 1970.
- Gethner et al. constructed -, -, and -moats in 1998.
- Tsuchimura constructed a -moat in 2004. These results exclude walks with step length at most , but do not settle whether some finite bound permits an infinite walk.
2019 restricted claim
A 2019 arXiv note, “A Note on The Gaussian Moat Problem,” claims that no infinite bounded-step sequence exists for Gaussian primes with . This is only a restricted version of the stated problem, and the claim is unverified; the paper also acknowledges an unresolved issue about whether its constructed moats separate the origin from infinity.
Current status (as of October 2026): The general Gaussian moat problem remains open; classical results rule out bounded walks through step length , while the 2019 restricted proof claim is unverified and does not cover all Gaussian primes.
Sources
- ar5iv.labs.arxiv.org
- ar5iv.labs.arxiv.org
- en.wikipedia.org
- cdn.openai.com
- www-cdn.anthropic.com
- quantamagazine.org
- quantamagazine.org
- cdn.openai.com
- cdn.openai.com
- quantamagazine.org
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- ar5iv.labs.arxiv.org
- ar5iv.labs.arxiv.org
- arxiv.org
- mathstodon.xyz
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- cdn.openai.com
- cdn.openai.com
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