Recent zbMATH articles in MSC 81T16https://www.zbmath.org/atom/cc/81T162022-01-14T13:23:02.489162ZWerkzeugNon-perturbative unitarity and fictitious ghosts in quantum gravityhttps://www.zbmath.org/1475.830372022-01-14T13:23:02.489162Z"Platania, Alessia"https://www.zbmath.org/authors/?q=ai:platania.alessia-benedetta"Wetterich, Christof"https://www.zbmath.org/authors/?q=ai:wetterich.christofSummary: We discuss aspects of non-perturbative unitarity in quantum field theory. The additional ghost degrees of freedom arising in ``truncations'' of an effective action at a finite order in derivatives could be fictitious degrees of freedom. Their contributions to the fully-dressed propagator -- the residues of the corresponding ghost-like poles -- vanish once all operators compatible with the symmetry of the theory are included in the effective action. These ``fake ghosts'' do not indicate a violation of unitarity.Vacua in novel 4D Einstein-Gauss-Bonnet gravity: pathology and instability?https://www.zbmath.org/1475.831182022-01-14T13:23:02.489162Z"Shu, Fu-Wen"https://www.zbmath.org/authors/?q=ai:shu.fuwenSummary: We show an inconsistence of the novel 4D Einstein-Gauss-Bonnet gravity by considering a quantum tunneling process of vacua. Based on standard semiclassical techniques, we find a nonperturbative way to the study of the vacuum decay rate of the theory. We analytically compute all allowed cases in the parameter space. It turns out, without exception, that the theory either encounters a disastrous divergence of vacuum decay rate, or exhibits a confusing complex value of vacuum decay rate, or involves an instability (a large vacuum mixing). These suggest a strong possibility that the theory, at least the vacuum of the theory, is either unphysical or unstable, or has no well-defined limit as \(D \to 4\).Black remnants from T-dualityhttps://www.zbmath.org/1475.831222022-01-14T13:23:02.489162Z"Pourhassan, Behnam"https://www.zbmath.org/authors/?q=ai:pourhassan.behnam"Wani, Salman Sajad"https://www.zbmath.org/authors/?q=ai:wani.salman-sajad"Faizal, Mir"https://www.zbmath.org/authors/?q=ai:faizal.mirSummary: In this paper, we will analyze the physical consequences of black remnants, which form due to non-perturbative string theoretical effects. These non-perturbative effects occur due to the T-duality in string theory. We will analyze the production of such black remnants in models with large extra dimensions, and demonstrate that these non-perturbative effects can explain the absence of mini black holes at the LHC. In fact, we will constraint such models using data from the LHC. We will also analyze such non-perturbative corrections for various other black hole solutions. Thus, we will analyze the effects of such non-perturbative corrections on the Van der Waals behavior of AdS black holes. We will also discuss the effects of adding a chemical potential to this system. Finally, we will comment on the physical consequences of such non-perturbative corrections to black hole solutions.