Search for vector-like quarks and heavy resonances decaying to top quarks in ATLAS

This document presents the recent results of the ATLAS experiment at the LHC concerning the $t\bar{t}$ resonance and vector-like quark searches. A search for $t\bar{t}$ resonances at 13~TeV in proton-proton collisions data is performed in the lepton+jet final state and for boosted top topologies. A re-interpretation of the analysis performed with the data recorded at the center of mass energy of 8~TeV, is also presented, for a scalar resonant signal. A vector-like top pair production is also searched for, through three analyses where the vector-like quark decay to Zt, Ht or Wb. A comparison of those analyses is presented. In addition, vector-like quarks are searched via the same sign lepton topology. The results are presented as mass limits on the vector-like top branching ratio plane and as the cross section limit on the $T_{5/3}$ pair production.