On weak weighted estimates of martingale transform
  We consider several weak type estimates for singular operators using the Bellman function approach. We disprove the $A_1$ conjecture of Muckenhoupt, which stayed open after Muckenhoupt--Wheeden's conjecture was disproved by Reguera--Thiele. 
Fedor Nazarov, Alexander Reznikov, Vasily Vasyunin, Alexander Volberg
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