Starting from a generic generally covariant quantum theory, we introduce a logarithmic correction to the quantum wave equation. We demonstrate the emergence of evolution time from the group of automorphisms of the von Neumann algebra governed by this nonlinear correction. It turns out that such a parametrization of time is essentially energy-dependent and becomes global only asymptotically, as the energies become very small as compared to the effective quantum gravity scale. A similar thing happens to Lorentz invariance: in the resulting theory it becomes an asymptotic low-energy phenomenon. We show how the logarithmic nonlinearity deforms the vacuum wave dispersion relations and explains certain features of the astrophysical data coming from the recent observations of high-energy cosmic rays. In general, the estimates imply that, ceteris paribus, particles with higher energy propagate slower than those with lower energy, therefore, for a high-energy particle the mean free path, lifetime in a high-energy state and thus the travel distance from the source can be significantly larger than one would expect from the conventional theory. In addition, we discuss the possibility and conditions of transluminal phenomena in the physical vacuum such as Cherenkov-type shock waves.

The exactly solvable scalar hairy black hole model (originated from the modern high-energy theory) is proposed. It turns out that the existence of black holes is strongly correlated to global scalar field, in a sense that they mutually impose bounds upon their physical parameters like the black hole mass (lower bound) or the cosmological constant (upper bound). We consider the same model also as a cosmological one and show that it agrees with recent experimental data; additionally, it provides a unified quintessencelike description of dark energy and dark matter.

We compare two approaches to open quantum systems, namely, the non-Hermitian dynamics and the Lindblad master equation. In order to deal with more general dissipative phenomena, we propose the unified master equation that combines the characteristics of both of these approaches. This allows us to assess the differences between them as well as to clarify which observed features come from the Lindblad or the non-Hermitian part, when it comes to experiment. Using a generic two-mode single-atom laser system as a practical example, we analytically solve the dynamics of the normalized density matrix operator. We study the two-level model in a number of cases (depending on parameters and types of dynamics), compute different observables and study their physical properties. It turns out that one is able not only to describe the different types of damping in dissipative quantum optical systems but also to mimic the undamped anharmonic oscillatory phenomena which happen in quantum systems with more than two levels (while staying within the framework of the analytically simple two-mode approximation).Comment: 13 pages, 9 figures. The article is based on the talks given at the conferences "12th International Workshop on Pseudo-Hermitian Hamiltonians in Quantum Physics" (02-06 July, 2013, Koc University, Istanbul, Turkey) and "Quantum Information Processing, Communication and Control 2" (25-29 November, 2013, KwaZulu-Natal, South Africa

We introduce a formalism for time-dependent correlation functions for systems whose evolutions are governed by non-Hermitian Hamiltonians of general type. It turns out that one can define two different types of time correlation functions. Both these definitions seem to be physically consistent while becoming equivalent only in certain cases. Moreover, when autocorrelation functions are considered, one can introduce another function defined as the relative difference between the two definitions. We conjecture that such a function can be used to assess the positive semidefiniteness of the density operator without computing its eigenvalues. We illustrate these points by studying analytically a number of models with two energy levels.