Related papers: What to expect from scalar-tensor space geodesy
Following work by Khoury and Weltman, we introduce a scalar field phi, the chameleon, which is conformally coupled to matter. That is, matter experiences a metric which is a conformal transform (parametrized by phi) of the Einstein metric.…
We study the relationship between the strength of fifth forces and the origin of scale breaking in the Standard Model (SM) of particle physics. We start with a light scalar field that is conformally coupled to a toy SM matter sector through…
We study observational bounds in a class of scalar-tensor gravity theories recently proposed. Either an upper or lower bound on a conformal factor in these theories is derived from null observation in composition dependent fifth force…
By studying the chameleon gravity on galaxy scales, we investigate the effects of the chameleon dark matter. To perform this task, we consider the dynamics of the chameleon scalar field in the region of galactic halos in static spherically…
Light scalars generically mediate a fifth force incompatible with local tests of gravity unless their couplings are parametrically suppressed or screening mechanisms are introduced. We demonstrate that such suppression can arise from…
In this paper, we study the distribution of dark matter halos and voids using high resolution simulations in f(R) gravity models with the chameleon mechanism to screen the fifth force in dense environment. For dark matter halos, we show…
Cross-correlating two different types of galaxy gives rise to parity breaking in the correlation function that derives from differences in the galaxies' properties and environments. This is typically associated with a difference in galaxy…
We investigate a chameleon scalar field dynamically interacting with a Kiselev-type metric, where the static anisotropic fluid part of the metric is replaced by a density-dependent scalar field non-minimally coupled to curvature. This…
Theories of dark energy require a screening mechanism to explain why the associated scalar fields do not mediate observable long range fifth forces. The archetype of this is the chameleon field. Here we show that individual atoms are too…
Screening mechanisms are essential features of dark energy models mediating a fifth force on large scales. We study the regime of strong scalar field nonlinearities, known as Vainshtein screening, in the most general scalar-tensor theories…
The last few decades have provided abundant evidence for physics beyond the two standard models of particle physics and cosmology. As is now known, the by far largest part of our universe's matter/energy content lies in the `dark' and…
Modified theories of gravity that offer viable models for dark energy often rely on mechanisms that screen their effects in high density environments. From this perspective, it would appear that, once solar system constraints are satisfied,…
We investigate the behavior of the fifth force in voids in chameleon models using the spherical collapse method. Contrary to Newtonian gravity, we find the fifth force is repulsive in voids. The strength of the fifth force depends on the…
Scalar-tensor theories are the best motivated alternatives to general relativity and provide a mathematically consistent framework to test the various observable predictions. They can involve three functions of the scalar field: (i) a…
Chameleon fields, which are scalar field dark energy candidates, can evade fifth force constraints by becoming massive in high-density regions. However, this property allows chameleon particles to be trapped inside a vacuum chamber with…
We consider $f(R)$ modified gravity theory incorporating the chameleon mechanism to address galactic dynamics. By employing the metric formalism and utilizing a conformal transformation, we simplify the field equations and describe the…
Here we investigate a possible presence of a fifth force at the Galactic Center (GC), and its potential influence on the stellar orbits around the central supermassive black hole of our Galaxy. For this purpose we simulated the stellar…
We consider the emergence of large-scale cosmological expansion in scalar-tensor theories of gravity. This is achieved by modelling sub-horizon regions of space-time as weak-field expansions around Minkowski space, and then subsequently…
We present a unifying treatment for metric and scalar perturbations across different energy regimes in scalar-tensor theories of gravity. To do so, we introduce two connected symmetry-breaking patterns: one due to the acquisition of…
Recently, the scalar-tensor representation of $f (R,T)$ gravity was used to explore gravitationally induced particle production/annihilation. Using the framework of irreversible thermodynamics of open systems in the presence of matter…