Modern Physics Letters A

Measurements of the luminosity of Type Ia supernovae versus redshift provided the original evidence for the accelerating expansion of the Universe and the existence of dark energy. Despite substantial improvements in survey methodology, systematic uncertainty in flux calibration dominates the error budget for this technique, exceeding both statistics and other systematic uncertainties. Consequently, any further collection of Type Ia supernova data will fail to refine the constraints on the nature of dark energy unless we also improve the state of the art in astronomical flux calibration to the order of 1%. We describe how these systematic errors arise from calibration of instrumental sensitivity, atmospheric transmission and Galactic extinction, and discuss ongoing efforts to meet the 1% precision challenge using white dwarf stars as celestial standards, exquisitely calibrated detectors as fundamental metrologic standards, and real-time atmospheric monitoring.

Axion electrodynamics is deduced from the local duality invariant electrodynamics (LDIE) with a new perspective on both formalism and the physical interpretation. First, the delicate issue of duality rotation symmetry in the Maxwell action is critically reviewed and the generalized Maxwell field equations invariant under local duality rotation are derived. In the alternative approach, a generalization is made to Sudbery’s pseudo-vector action such that it is local duality invariant. Variational principle is used to derive the Euler–Lagrange equations of motion. The gauge potential for local duality rotation, termed duroton, under the assumption that it is a gradient of the axion field leads to the dual symmetric axion electrodynamics. The absence of the magnetic monopole in Maxwell equations motivates to impose a natural condition to deduce the standard axion electrodynamics. The present derivation offers the possibility for new physical interpretation of the axions and the monopoles.

In this paper, we will examine the problem of violation of causality in $f(R,T)$ modified gravity, where $R$ is the Ricci scalar and $T$ is the trace of the energy–momentum tensor $T_{\mu \nu }$. We investigate the causality problem in two special cases, in the first we consider the matter content of the universe as a perfect fluid and in the second case, the matter content is a perfect fluid plus a scalar field.

The gauge dependence problem existing in the original Gribov–Zwanziger theory is discussed.

The nonlinear propagation of dust-ion-acoustic (DIA) solitary waves (SWs) in an unmagnetized four-component dusty plasma containing electrons and negative ions obeying vortex-like (trapped) velocity distribution, cold mobile positive ions and arbitrarily charged stationary dust has been theoretically investigated. The properties of small but finite amplitude DIASWs are studied by employing the reductive perturbation technique. It has been found that owing to the departure from the Maxwellian electron and Maxwellian negative ion distribution to a vortex-like one, the dynamics of such DIASWs is governed by a modified Korteweg–de Vries (mKdV) equation which admits SW solution under certain conditions. The basic properties (speed, amplitude, width, etc.) of such DIASWs are found to be significantly modified by the presence of trapped electron and trapped negative ions. The implications of our results to space and laboratory dusty electronegative plasmas (DENPs) are briefly discussed.

In this study, we investigate whether global monopoles cause black holes or wormholes to form. Field equations for static spherically symmetric spacetimes with global monopoles are obtained in $f(R)$ gravity. We found exact solutions for the field equations without using any perturbation or approximation methods. It is shown that the obtained $f(R)$ function is in accordance with the $\mathrm{\Lambda }$-cold dark matter ($\mathrm{\Lambda }$-CDM) model. Also, it is shown that the static spherically symmetric spacetimes associated with global monopoles form black holes or wormhole structures under some restrictions. Finally, geometrical and physical results of the solutions are discussed.