Narrow Results

In an attempt to explain some of the unknown phenomena of nature, including dark energy and dark matter, we explore the possibility of the existence of a fifth fundamental force of nature as also cited by some researchers. With the inclusion of such a force in the system, some of the vague things can be explained and there is high hope of its importance in building up a “theory of everything”. With this intention, we investigate some manifestations of the fifth force which stand from theoretical calculations or from theoretical point of view, though till now there is less experimental proof. However, the theoretical results obtained indicate the existence of a fifth force which will lead to the completion in defining the laws of physics and nature. With this discovery, science may be able to explain the whole complexity of the Universe in near future.

In this work, we consider the Universe is being filled with matter composed of a chameleon-type dark energy scalar field. Employing a particular form of potential, we discuss the field's role in the accelerating phase of the Universe for an anisotropic model using the logamediate and intermediate forms of scale factors. The natures of statefinder and slow-roll parameters are discussed diagrammatically.

There is a deep connection between cosmology — the science of the infinitely large — and particle physics — the science of the infinitely small. This connection is particularly manifest in neutron particle physics. Basic properties of the neutron — its Electric Dipole Moment and its lifetime — are intertwined with baryogenesis and nucleosynthesis in the early Universe. I will cover this topic in the first part, that will also serve as an introduction (or rather a quick recap) of neutron physics and Big Bang cosmology. Then, the rest of the paper will be devoted to a new idea: using neutrons to probe models of Dark Energy. In the second part, I will present the chameleon theory: a light scalar field accounting for the late accelerated expansion of the Universe, which interacts with matter in such a way that it does not mediate a fifth force between macroscopic bodies. However, neutrons can alleviate the chameleon mechanism and reveal the presence of the scalar field with properly designed experiments. In the third part, I will describe a recent experiment performed with a neutron interferometer at the Institut Laue Langevin that sets already interesting constraints on the chameleon theory. Last, the chameleon field can be probed by measuring the quantum states of neutrons bouncing over a mirror. In the fourth part, I will present the status and prospects of the GRANIT experiment at the ILL.

In this work, we consider an emergent Universe in generalized gravity theories like the chameleon, f(R) and f(T) gravities. We reconstruct the potential of the chameleon field under the emergent scenario of the Universe and observe its increasing nature with the evolution of the Universe. We reveal that in the emergent Universe scenario, the equation-of-state parameter behaves like quintessence in the case of f(R) gravity and like phantom in the case of f(T) gravity.

In this paper, the field equations of a chameleon field in which the matter Lagrangian term is a general function of the scalar field as well as matter field, are derived. The equations are then expressed in Friedmann–Lemaître–Robertson–Walker (FLRW) framework and the associated phase portraits and a power law solution are discussed in details. It is shown that why nonminimal coupling between the chameleon and matter fields leads to an energy transfer between the fields, which consequently affects the expansion rate of the universe. The transfer direction is determined by the second law of thermodynamics. The solution indicates that an accelerating expansion of the universe can be described as a result of the energy flow from the chameleon field to matter field.