From https://t.me/usf_army

At one of the active front-line sectors, operators of the #20th Separate #K_2 Regiment of the Unmanned Systems Forces disrupted the enemy's preparation for offensive actions.

In coordination with aerial reconnaissance, which maintains constant control over the line of combat contact, strike #UAV pilots inflicted targeted damage on vehicles used by the occupiers to move reserves from rear areas.

Unknotting number is not additive under connected sum

Mark Brittenham, Susan Hermiller
https://arxiv.org/abs/2506.24088 https://arxiv.org/pdf/2506.24088 https://arxiv.org/html/2506.24088

arXiv:2506.24088v1 Announce Type: new
Abstract: We give the first examples of a pair of knots $K_1$,$K_2$ in the 3-sphere for which their unknotting numbers satisfy $u(K_1\#K_2)<u(K_1)+u(K_2)$ . This answers question 1.69(B) from Kirby's problem list, "Problems in low-dimensional topology", in the negative.

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