My research field is theoretical high energy physics, in particular, my major interest rests on two areas of physics: quantum field theory (QFT) and general relativity (GR). In GR I pursue to apply and develop the ideas of effective field theory techniques proposed by W.Goldberger and I.Rothstein for various classical setups, whereas on the QFT side my efforts are concentrated on studying the models in the region of parameter space where presumably the theory is not well-posed and a natural question arises: is there a loophole to make sense of such a theory? Apart from the theoretical perspectives, the answer to this question implies robust cosmological outcomes and opens a wide door towards better understanding of the cosmology in general and the long standing problem of the singularity in particular. Moreover, nowadays one of the most natural interplays between GR and QFT manifests itself in the AdS/CFT conjecture and currently I am also trying my hand in various holographic aspects of the entanglement entropy and related issues.