International Journal of Modern Physics A

In this paper, we consider the group formed by finite renormalizations as an infinite-dimensional Lie group. It is demonstrated that for the finite renormalization of the gauge coupling constant, its generators ${\widehat{L}}_n$ with $n\ge 1$ satisfy the commutation relations of the Witt algebra and, therefore, form its subalgebra. The commutation relations are also written for the more general case when finite renormalizations are made for both the coupling constant and matter fields. We also construct the generator of the Abelian subgroup corresponding to the changes of the renormalization scale. The explicit expressions for the renormalization group generators are written in the case when they act on the $\beta$-function and the anomalous dimension. It is explained how the finite changes of these functions under the finite renormalizations can be obtained with the help of the exponential map.

In this paper, we propose an approach based on the theory of an axiomatic S matrix and partially switching on an interaction, which is extremely suitable for describing the phenomenon of oscillations within the framework of quantum field theory. We discuss the relation of the proposed approach with other approaches based on considering of wave packets as asymptotic states or introducing of “distance- or time-dependent propagators”.

We study a subclass of Horndeski gravity which has both global conformal and shift symmetries. Global symmetries are characterized by the presence of a conserved current which has been shown to be of particular importance for the integrability features of the theory at hand yielding numerous compact object solutions. We find the general conserved current associated to global conformal symmetry of Horndeski theories. We discuss some of its properties, how it can be conveniently broken by physically relevant terms and, show how it is related to that of shift symmetry when shift symmetry is present. Given our results, we consider a particular theory and demonstrate how the presence of symmetries provides integrability for the given black hole solution. We then find the charged extension of the solution thanks to the conformal invariance of the Maxwell action.

In this paper, we propose generalizations of the Sokolov–Ternov and Unruh effects, and discuss the possibility to measure them on different experiments.

In this paper, we propose that physical time is based on counting the oscillations of wave functions. The discrete counting of the ticks of these clocks does not depend on the metric frame. It remains well defined for the beginning epochs of the universe. The photon clock counts the oscillations of electromagnetic plane waves in the cosmic reference frame. It can be gauged with clocks for other massless or massive particles. These equivalent clocks form a clock system which defines a common universal continuous physical time. For the photon clock, this physical time coincides with conformal time. The universe is eternal toward the past for typical models of inflationary cosmology — the photon clock ticks an infinite number of times. We compare the photon clock system to geodesic physical time, which is a frame invariant generalization of proper time.

We review the recent results on the search for Light Dark Matter (LDM) in the NA64 experiment at CERN. The phenomenology and production of LDM, as well as the experimental constraints from other accelerator searches are also briefly discussed.

In this paper, we numerically study the evolution of a classical real scalar field in $(1+1)$ dimensions with initial conditions describing thermal fluctuations around a metastable vacuum. We track false vacuum decay in real time and compare several observables to the predictions of the standard Euclidean formalism. We find agreement for the shape of the critical bubble and the exponential suppression of the decay rate. However, the decay rate prefactor is almost an order of magnitude lower than the predicted value. We argue that this signals a breakdown of thermal equilibrium during the bubble nucleation. In addition, the inefficient thermalization in the system biases the properties of the statistical ensemble and leads to further decrease of the decay rate with time. We substantiate our interpretation with a suite of stochastic field simulations with controlled thermalization time. By varying this time, we find that the predictions of the standard equilibrium formalism are recovered when it is sufficiently short. We propose an upper bound on the thermalization time that must be satisfied in order to ensure the applicability of the Euclidean rate calculation. We discuss that this bound is unavoidably violated in common single-field models, irrespective of the number of space–time dimensions, implying that deviations from equilibrium in these models cannot be neglected. In theories with multiple fields, the bound may or may not hold, depending on the setup details. We investigate one more signature of nonequilibrium dynamics — coherent oscillonic precursors to the critical bubble nucleation. We show that they get suppressed in the stochastic dynamical simulations when the thermalization time is reduced.