Related papers: May Negative Mass Objects exist in the sky?
Many gravitational phenomena that lie at the core of our understanding of the Universe have not yet been directly observed. An example in this sense is the boson star that has been proposed as an alternative to some compact objects…
Probing the existence of hypothetical particles beyond the Standard model often deals with extreme parameters: large energies, tiny cross-sections, large time scales, etc. Sometimes laboratory experiments can test required regions of…
The present surge for the astrophysical relevance of boson stars stems from the speculative possibility that these compact objects could provide a considerable fraction of the non-baryonic part of dark matter within the halo of galaxies.…
In the standard model of universe the increase in mass of our observed expansive Universe is explained by the assumption of emerging the matter objects on the horizon (of the most remote visibility). However, the physical analysis of the…
The discovery of acceleration of the universe expansion in recent astrophysics research prompts the author to propose that the Newton's gravitation law can be generalized to accommodate the antimatter: While the force between…
We propose that the ``isolated'' planetary mass objects observed by Zapatero Osorio et al in the $\sigma$ Orionis cluster might actually be in orbit around invisible stellar mass companions such as mirror stars. Mirror matter is expected to…
A modified-gravity-type model of two hypothetical massless vector fields is presented. These vector fields are gravitationally coupled to standard matter and an effective cosmological constant. Considered in a cosmological context, the…
A number of observed phenomena in high energy physics and cosmology lack their resolution within the Standard Model of particle physics. These puzzles include neutrino oscillations, baryon asymmetry of the universe and existence of dark…
I discuss possible implications a symmetry relating gravity with antigravity might have for smoothing out of the cosmological constant puzzle. For this purpose, a very simple model with spontaneous symmetry breaking is explored, that is…
We generalize tensor-scalar theories of gravitation by the introduction of an abnormally weighting type of energy. This theory of tensor-scalar anomalous gravity is based on a relaxation of the weak equivalence principle that is now…
Neutron stars are highly compact astrophysical objects and therefore of utmost relevance to learn about theories of gravity. Whereas the proper equation of state of the nuclear matter inside neutron stars is not yet known, and a wide range…
We study boson stars in a theory of complex scalar field coupled to Einstein gravity with the potential: $V(|\Phi|) := m^{2} |\Phi|^2 +2 \lambda |\Phi|$ (where $m^2$ and $\lambda$ are positive constant parameters). This could be considered…
We analyze, within the framework of unified brane gravity, the weak-field perturbations caused by the presence of matter on a 3-brane. Although deviating from the Randall-Sundrum approach, the masslessness of the graviton is still…
The generic properties of compact objects made of two different fluids of dark matter are studied in a scale invariant approach. We investigate compact objects with a core-shell structure, where the two fluids are separated, and with mixed…
Exact Newtonian potential with an extra space dimension compactified on a circle is derived and studied. It is found that a point mass located at one side of the circle can generate almost the same strength of gravitational force at the…
The Standard Model is in good shape, apart possibly from g_\mu - 2 and some niggling doubts about the electroweak data. Something like a Higgs boson is required to provide particle masses, but theorists are actively considering…
Several dark matter models allow for the intriguing possibility of exotic compact object formation. These objects might have unique characteristics that set them apart from their baryonic counterparts. Furthermore, gravitational wave…
Modifications to Newtonian dynamics at low accelerations have long been proposed as an alternative to dark matter to explain galaxy rotation curves. More recently, similar corrections have been invoked to interpret anomalies in…
We define gravitational mass in asymptotically de Sitter space-times with compactified dimension. It was shown that the mass can be negative for space-time with matter spreading beyond the cosmological horizon scale or large outward…
It is assumed that the primary interaction between two masses m1 and m2 is not attractive as postulated by Newton's law of gravitation, but repulsive. Both m1 and m2 emit and absorb gravitational radiation. Corresponding to the laws of…