Boosted top quark techniques and searches for $t\bar{t}$ resonances at the LHC

In many models of beyond the Standard Model physics (BSM) the top quark plays a special role. The ATLAS and CMS experiments at the Large Hadron Collider (LHC) have performed dedicated searches for $t\bar{t}$ resonances, which may occur in BSM models. Especially at high $t\bar{t}$ masses the top quarks can have strongly boosted decay products. In recent years many new techniques have been developed to reconstruct and identify such decays. Both ATLAS and CMS use jet substructure to identify hadronic $W$ boson and top quark decays. Some of those techniques are summarised in this article and the recent results of searches for $t\bar{t}$ resonances are presented. In the lepton+jets channel a leptophobic top-colour $Z'$ with a small width could be excluded at the 95% CL in the range $0.5TeV < m_{Z'} < 1.7 TeV$ as a benchmark scenario. Kaluza-Klein gluons and $Z'$ bosons with larger widths could be excluded in similar mass ranges.