All Topics
All Topics
Technology
Technology
Design
Design
Programming
Programming
Science
Science
News
News
Gaming
Gaming
Entertainment
Entertainment
Business
Business
Finance
Finance
Sports
Sports
Health
Health
Food
Food
Travel
Travel
Art
Art
Music
Music
Books
Books
Education
Education
Politics
Politics
Personal
Personal
No algorithm. No AI slop. No ads. Just RSS. Pro-human. Indie writers. Real journalism. Open web. Chronological. Hand toasted.

Mathematicians Disprove Long-Standing Knot Theory Conjecture About Unknotting Numbers

By

JohnHammersley

7mo ago· 5 min readenNews

Summary

Mathematicians Mark Brittenham and Susan Hermiller published a groundbreaking preprint disproving a long-standing conjecture in knot theory that the unknotting number is additive under connected sum. Their counterexample, which involves creating a knot with unknotting number 2 from two knots each with unknotting number 1, challenges fundamental assumptions in the field and has generated significant attention in the mathematical community.

Key quotes

· 5 pulled
The unknotting number of a knot is the minimum number of times you need to change a crossing in a diagram of the knot to turn it into the unknot.
The conjecture was that the unknotting number is additive under connected sum: u(K#L) = u(K) + u(L).
They found a counterexample: two knots K and L, each with unknotting number 1, such that their connected sum K#L has unknotting number 2.
This is a surprising result because it goes against what many mathematicians believed for a long time.
The discovery has generated excitement in the mathematical community and been covered by major science publications.
Snippet from the RSS feed
On June 30, 2025, Mark Brittenham and Susan Hermiller uploaded a preprint to the arXiv called “Unknotting number is not additive under connected sum” (and an updated version on Septembe…

You might also wanna read