Showing papers in "International Journal of Geometric Methods in Modern Physics in 2019"

Abstract: We show that an n-dimensional generalized Robertson–Walker (GRW) space-time with divergence-free conformal curvature tensor exhibits a perfect fluid stress–energy tensor for any f(R) gravity model....

Abstract: The aim of this thesis is to provide a general description of the corpuscular theory of gravity. After reviewing some of the major conceptual issues emerging from the semiclassical and field theoretic approaches to Einstein's gravity, we present a synthetic overview of two novel (and extremely intertwined) perspectives on quantum mechanical effects in gravity: the horizon quantum mechanics formalism and the classicalization scheme. After this preliminary discussion, we then proceed with implementing the latter to several different scenarios, namely self-gravitating systems, the early Universe, and galactic dynamics. Concerning the first scenario, we start by describing the generation of the Newtonian potential as the result of a coherent state of toy (scalar) gravitons. After that we employ this result to study some features of the gravitational collapse and to argue that black holes can be thought of a self-sustained quantum states, at the critical point, made of a large number soft virtual gravitons. We then refine this simplified analysis by constructing an effective theory for the gravitational potential of a static spherical symmetric system up to the first post-Newtonian correction. Additionally, we employ the horizon quantum mechanics formalism to study the causal structure emerging from the corpuscular scenario. Finally, we present a short discussion of corpuscular black holes in lower dimensional spaces. After laying down the basics of corpuscular black holes, we present a generalization of the aforementioned arguments to cosmology. Specifically, we first introduce a corpuscular interpretation of the de Sitter spacetime. Then we use it as the starting point for a corpuscular formulation of the inflationary scenario and to provide an alternative viewpoint on the dark components of the LambdaCDM model. The key message of this work is that the corpuscular theory of gravity offers a way to unify most of the experimental observations (from astrophysical to galactic and cosmological scales) in a single framework, solely based on gravity and baryonic matter.

Abstract: These are the lecture notes for the course given at the “XXVII International Fall Workshop on Geometry and Physics” held in Seville (Spain) in September 2018. We review the geometric formulation of...

Abstract: In this paper, we relate the evolution equations of the electric field and magnetic field vectors of the polarized light ray traveling in a coiled optical fiber in the ordinary space into the nonli...

Abstract: Finsler geometry naturally appears in the description of various physical systems. In this review, I divide the emergence of Finsler geometry in physics into three categories: dual description of d...

Abstract: Schwinger’s algebra of selective measurements has a natural interpretation in the formalism of groupoids. Its kinematical foundations, as well as the structure of the algebra of observables of the ...

Abstract: The kinematical foundations of Schwinger’s algebra of selective measurements were discussed in [F. M. Ciaglia, A. Ibort and G. Marmo, Schwinger’s picture of quantum mechanics I: Groupoids, To appea...

Abstract: In a n-dimensional Friedmann–Robertson–Walker metric, it is rigorously shown that any analytical theory of gravity f(R,𝒢), where R is the curvature scalar and 𝒢 is the Gauss–Bonnet topological inva...

Abstract: We compare the gravitational collapse of homogeneous perfect fluid with various equations of state in the framework of General Relativity and in R2 gravity. We make our calculations using dimension...

Abstract: A new picture of Quantum Mechanics based on the theory of groupoids is presented. This picture provides the mathematical background for Schwinger’s algebra of selective measurements and helps to un...

Abstract: In this work, we calculate the quantum correction effects on the deflection of light in the space-time geometry of a quantum improved Kerr black hole pierced by an infinitely long cosmic string. Mo...

Abstract: In this paper, we discuss the singular Lagrangian systems on the framework of contact geometry. These systems exhibit a dissipative behavior in contrast with the symplectic scenario. We develop a c...

Abstract: In this paper, we find solutions for the Klein–Gordon equation in the presence of a Cornell potential under the influence of noninertial effects in the cosmic string space-time. Then, we study Klein–Gordon oscillator in the cosmic string space-time. In addition, we show that the presence of a Cornell potential causes the forming bound states for the Klein–Gordon equation in this kind of background.

Abstract: The construction of nonstandard Lagrangians and Hamiltonian structures for Lienard equations satisfying Chiellini condition is presented and their connection to time-dependent Hamiltonian formalism...

Abstract: In this work, we study inextensible flows of tangent bimagnetic particles in space. Moreover, we obtain the inextensible flows of electric field by Lorentz equation. Finally, we obtain new results ...

Abstract: This paper is devoted to exploring exact charged solutions in a cloud of strings through minimal geometric deformation technique in three-dimensional gravity. For this purpose, we first evaluate th...

Abstract: In the present paper, the work of Moreas et al. [P. H. R. S. Moraes, G. Ribeiro and R. A. C. Correa, A transition from a decelerated to an accelerated phase of the universe expansion from the simpl...

Abstract: We derive the weak field limit for a gravitational Lagrangian density Lg = (R + a0R2 +∑ k=1pa kR□kR)−g, where higher-order derivative terms in the Ricci scalar R are taken into account. The interes...

Abstract: Catheterization has an imperative rule in heat transfer investigations, which are frequently applied to analyze and deal with the heart transfer studies. Here, the entering of a catheter adjusts th...

Abstract: An orthogonality space is a set endowed with a symmetric, irreflexive binary relation. By means of the usual orthogonality relation, each anisotropic quadratic space gives rise to such a structure....

Abstract: We define the coordinate equations of killing magnetic curves γ(s) in ℝ13 with the magnetic vector field V under the frame {γ′(s),V,V ∧γ′(s)}. In particular, this yields to describe the geometrical...

Abstract: In this paper, we present a study of proper conformal vector fields of spatially homogeneous rotating space-times in the f(R) theory of gravity. A total of six cases have been discussed in detail. ...

Abstract: In this paper, we have presented bulk viscous cosmological model of the universe in the modified gravity theory in which the Lagragian of the gravitational action contains a general function f(R,T)...

Abstract: In this paper, we have studied proper conformal vector fields of pp-wave space-times in the f(R) theory of gravity using algebraic and direct integration techniques. From this study, we found that ...

Abstract: We study the phantom fluid in the late universe, thus assuming the equation of state parameter w to be less than − 1. The fluid is assumed to consist of two components, one laminar component ρ and ...

Abstract: If M is a 3-dimensional contact metric manifold such that Qφ = φQ which admits a Yamabe soliton (g,V ) with the flow vector field V pointwise collinear with the Reeb vector field ξ, then we show th...

Abstract: The realistic models of neutron stars are considered for simple R + αR2 gravity and equivalent Brance–Dicke theory with dilaton field in Einsein frame. For negative values of α we have no acceptabl...

Abstract: There are two types of warped product pseudo-slant submanifolds, M𝜃 ×fM⊥ and M⊥×fM𝜃, in a nearly Kaehler manifold. We derive an optimization for an extrinsic invariant, the squared norm of second f...

Abstract: With the extended navigation data, we consider the generalized Zermelo navigation on Riemannian manifolds, admitting a space-dependent ship’s speed in the presence of perturbation determined by a w...

Abstract: This paper is aimed to evaluate the existence of wormholes in viable f(R,T) gravity models (where R is the scalar curvature and T is the trace of stress–energy tensor of matter). The exact solution...