Geodesic deviation in pp-wave spacetimes of quadratic curvature gravity

We write the equation of geodesic deviations in the spacetime of $pp$-waves in terms of the Newman-Penrose scalars and apply it to study gravitational waves in quadratic curvature gravity. We show that quadratic curvature gravity $pp$-waves can have a transverse helicity-0 polarization mode and two transverse helicity-2 general relativity-like wave polarizations. A concrete example is given in which we analyze the wave polarizations of an exact impulsive gravitational wave solution to quadratic curvature gravity.Comment: 16 pages, no figures, accepted in Physical Review

On the conformally coupled scalar field quantum cosmology

We propose a new initial condition for the homogeneous and isotropic quantum cosmology, where the source of the gravitational field is a conformally coupled scalar field, and the maximally symmetric hypersurfaces have positive curvature. After solving corresponding Wheeler-DeWitt equation, we obtain exact solutions in both classical and quantum levels. We propose appropriate initial condition for the wave packets which results in a complete classical and quantum correspondence. These wave packets closely follow the classical trajectories and peak on them. We also quantify this correspondence using de-Broglie Bohm interpretation of quantum mechanics. Using this proposal, the quantum potential vanishes along the Bohmian paths and the classical and Bohmian trajectories coincide with each other. We show that the model contains singularities even at the quantum level. Therefore, the resulting wave packets closely follow the classical trajectories from big-bang to big-crunch.Comment: 14 pages, 4 figures, to appear in PL

Is there a trade-off between supervision and wage? Evidence from a metal mechanical firm in southern Brazil

The objective of this work was to test the existence of a trade-off between supervision and wages in a metal mechanical firm in Southern Brazil. The methodology used to assess the effects on productivity and the worker efficiency was the differences-in-differences estimator. Evaluating the results, it was found that with increased supervision, there was an increase in productivity ranging between 13.5% and 26.8%. Therefore, with increased productivity, the company has to choose between increasing the level of supervision, at a cost of US$624.98 or practicing efficiency wages at a cost of US$ 2,907.72.The objective of this work was to test the existence of a trade-off between supervision and wages in a metal mechanical firm in Southern Brazil. The methodology used to assess the effects on productivity and the worker efficiency was the differences-in-differences estimator. Evaluating the results, it was found that with increased supervision, there was an increase in productivity ranging between 13.5% and 26.8%. Therefore, with increased productivity, the company has to choose between increasing the level of supervision, at a cost of US$624.98 or practicing efficiency wages at a cost of US$ 2,907.72

New probe of modified gravity

We suggest a new efficient way to constrain a certain class of large scale modifications of gravity. We show that the scale-free relation between density and size of Dark Matter halos, predicted within the LambdaCDM model with Newtonian gravity, gets modified in a wide class of theories of modified gravity.Comment: 4pages, revte