We show, using purely classical considerations and logical extrapolation of results belonging to point particle theories, that the metric background field in which a string propagates must satisfy an Einstein or an Einstein–like equation. Additionally, there emerge restrictions on the worldsheet curvature, which seems to act as a source for spacetime gravity, even in the absence of other matter...

In this work, we investigate the effects of torsion on electromagnetic fields. As a model spacetime, endowed with both curvature and torsion, we choose a generalization of the cosmic string, the cosmic dislocation. Maxwell’s equations in the spacetime of a cosmic dislocation are then solved, considering both the case of a static, uniform, charge distribution along the string, and the case of a ...

The possibility of realization of a curvaton scenario is studied in a theory in which two dilatons are introduced along with coupling to the scalar curvature. It is shown that when two dilatons have an approximate O(2) symmetric coupling, a scalar field playing the role of the curvaton may exist in the framework of this theory without introducing any other scalar field for the curvaton. Thus th...

If stationary, the spectrum of vacuum field noise (VFN) is an important ingredient to get information about the curvature invariants of classical worldlines (relativistic classical trajectories). For scalar quantum field vacua there are six stationary cases as shown by Letaw some time ago, these are reviewed here. However, the nonstationary vacuum noises are not out of reach and can be processe...

We have studied modulated inflation that generates curvature perturbation from light-field fluctuation. As discussed in previous works, even if the fluctuation of the inflaton itself does not generate the curvature perturbation, fluctuation of a light field may induce fluctuation for the end-line of inflation and this may lead to generation of cosmological perturbation ”at the end of the inflat...

The quadratic form of the Dirac equation in a Riemann spacetime yields a gravitational gyromagnetic ratio κS = 2 for the interaction of a Dirac spinor with curvature. A gravitational gyromagnetic ratio κS = 1 is also found for the interaction of a vector field with curvature. It is shown that the Dirac equation in a curved background can be obtained as the square–root of the corresponding vecto...

In the second set of supplementary notes — Gravity, Metrics and Coordinates — we introduced the idea that matter induces spacetime curvature, and we argued that this curvature is fully described by the metric. In the case of a static, spherically symmetric mass distribution, we presented the Einstein Field Equations whose solution gives the metric and therefore the geometry of spacetime. The cu...

We have studied modulated inflation that generates curvature perturbation from light-field fluctuation. As discussed in previous works, even if the fluctuation of the inflaton itself does not generate the curvature perturbation, fluctuation of a light field may induce fluctuation for the end-line of inflation and this may lead to generation of cosmological perturbation ”at the end of the inflat...

We have studied modulated inflation that generates curvature perturbation from light-field fluctuation. As discussed in previous works, even if the fluctuation of the inflaton itself does not generate the curvature perturbation, fluctuation of a light field may induce fluctuation for the end-line of inflation and this may lead to generation of cosmological perturbation “at the end of the inflat...

If stationary, the spectrum of vacuum field noise (VFN) is an important ingredient to get information about the curvature invariants of classical worldlines (relativistic classical trajectories). For scalar quantum field vacua there are six stationary cases as shown by Letaw some time ago, these are reviewed here. However, the nonstationary vacuum noises are not out of reach and can be processe...