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Metin Arik

Publications and source records attributed to Metin Arik.

At least 37 records · Page 2Linked to original sources
arXiv2017

Gravitational Wave Solutions to Linearized Jordan-Brans-Dicke Theory on a Cosmological Background

Approximate vacuum solutions of Jordan-Brans-Dicke theory for perturbed scalar field and perturbed Robertson-Walker metric, are found. Solutions for the scale factor and the scalar field in unperturbed JBD theory are dependent on the $ω$ parameter which determines how the scalar field is coupled to geometry of space-time. After adding a metric perturbation to Robertson-Walker metric and a perturbation to the scalar field, we solved the linearized JBD equations and found the scale factor and the scalar field as $a\propto t$ and $ϕ\propto t^{-2}$ with $ω=$-3/2. The results are necessary conditions for ordinary and scalar gravitational waves to exist in the vacuum case. Despite omega is a large positive number for current solar system environment observations, this value of omega makes JBD theory conformally invariant and fits recent supernovae type Ia data. We also looked for the value of omega for the case which has nonzero spatial curvature parameter.

gr-qc↗
arXiv2017

Inflation and late time acceleration designed by Stueckelberg massive photon

We present a mini review of the Stueckelberg mechanism, which was proposed to make the abelian gauge theories massive as an alternative to Higgs mechanism, within the framework of Minkowski as well as curved spacetimes. The higher the scale the tighter the bounds on the photon mass, which might be gained via the Stueckelberg mechanism, may be signalling that even an extremely small mass of the photon which cannot be measured directly could have far reaching effects in cosmology. We present a cosmological model where Stueckelberg fields, which consist of both scalar and vector fields, are non-minimally coupled to gravity and the universe could go through a decelerating expansion phase sandwiched by two different accelerated expansion phases. We discuss also the possible anisotropic extensions of the model.

gr-qc↗
arXiv2016

A Perspicuous Description of the Schwarzschild Black Hole Geodesics

Schwarzschild black hole is the simplest black hole that is studied most in detail. Its behavior is best understood by looking at the geodesics of the particles under the influence of its gravitational field. In this paper, the focus of attention is giving a perspicuous description of the Schwarzschild geodesics by using analogue potential approach. Specifically we discuss geodesics of light and of a massive particle in the case that their angular momentum is non zero in the Schwarzschild spacetime. This discussion is done by defining analogue potentials out of geodesic equations and defining relevant dimensionless conserved quantities. Then, we designate how geodesics change in response to the change of these quantities. Our results indicate the relation between the particles' motion near black hole horizon and their angular momentum. Furthermore, we make a comparison between Newtonian Physics (NP) and General Relativity (GR) in the language of the analogue potential approach.

gr-qc↗
arXiv2016

Cosmological isotropic matter-energy generalizations of Schwarzschild and Kerr metrics

We present a time dependent isotropic fluid solution around a Schwarzschild black hole. We offer the solutions and discuss the effects on the field equations and the horizon. We derive the energy density, pressure and the equation of state parameter. In the second part, we generalize the rotating black hole solution to an expanding universe. We derive from the proposed metric the special solutions of the field equations for the dust approximation and the dark energy solution. We show that the presence of a rotating black hole does not modify the scale factor $b(t)=t^{2/3}$ law for dust, nor $b(t)=e^{λ\hspace{1mm}t}$ and $p=-ρ$ for dark energy.

gr-qc↗
arXiv2016

Quantum Mechanics in a Space with Finite Number of Points

We define a deformed kinetic energy operator for a discrete position space with a finite number of points. The structure may be either periodic or nonperiodic with well-defined end points. It is shown that for the nonperiodic case the translation operator becomes nonunitary due to the end points. This uniquely defines an algebra which has the desired unique representation. Energy eigenvalues and energy wave functions for both cases are found. As expected, in the continuum limit the solution for the nonperiodic case becomes the same as the solution of an infinite one dimensional square well and the periodic case solution becomes the same as the solution of a particle in a box with periodic boundary conditions.

quant-ph↗
arXiv2016

The Atmosphere of a Black Hole

We present a static, isotropic fluid solution around a black hole and its effects on the field equations and the horizon. We offer the solutions, their descriptions and we comment on their shortcomings. We derive from the proposed metric the density, the pressure, the equation of state, the temperature near and far of the black hole and the equation of state parameter. We show that for a special case, when $r\rightarrow\ 0$ the solution behaves as $p=\fracρ{3}$, the equation of state for radiation and for $r\rightarrow\infty$ we observe that $p=0$, the equation of state for dust.

gr-qc↗
arXiv2014

Black Hole solutions in a cosmological spacetime background

We propose and analyze a new metric that has two conformal factors a(t) and b(t) that combine the expansion of the universe and its effects on the spatial and temporal part of the Schwarzschild metric in isotropic coordinates. We present the solutions, their descriptions and we comment on their shortcomings. In the spatially flat case of an expanding universe, we derive from the proposed metric the special solutions of the field equations for the dust approximation and the McVittie metric. We show that the presence of a black hole does not modify the a(t) proportional to t^{2/3} law for dust and H=constant for dark energy.

gr-qc↗
arXiv2014

Accelerated expansion of the Universe a la the Stueckelberg mechanism

We investigate a cosmological model in which the Stueckelberg fields are non-minimally coupled to the scalar curvature in a gauge invariant manner. We present not only a solution that can be considered in the context of the late time acceleration of the universe but also a solution compatible with the inflationary cosmology. Distinct behaviors of the scalar and vector fields together with the real valued mass gained by the Stueckelberg mechanism lead the universe to go through the two different accelerated expansion phases with a decelerated expansion phase between them. On the other hand, in the solutions we present, if the mass is null then the universe is either static or exhibits a simple power law expansion due to the vector field potential.

gr-qc↗
arXiv2014

Bending of light caused by gravitation: the same result via totally different philosophies

We offer a concise and direct way to derive the bending angle of light (i.e. as generally called, gravitational lensing), while light grazes a star, through the approach suggested earlier by the first author, which is fundamentally based on the energy conservation law and the weak equivalence principle. We come out with the same result as that of the general theory of relativity (GTR), although the philosophies behind are totally different from each other. We emphasize that in our approach, there is no need to draw a distinction between light and ordinary matter, which makes our approach of gravity potentially compatible with quantum mechanics. Furthermore, our equation that furnishes gravitational lensing, also furnishes the result about the precession of the perihelion of a planet. The results obtained are discussed.

physics.gen-ph↗
arXiv2013

A five dimensional model with a fifth dimension as fundamental as time in terms of a cosmological approach

In five dimensional cosmological models, the convention is to include the fifth dimension in a way similar to the other space dimensions. In this work we attempt to introduce the fifth dimension in a way that a time dimension would be introduced. With such an internal space, we are able to obtain accelerated expansion without introducing dark energy. We obtain a five dimensional flat, meaning both Ricci flat and conformally flat, spacetime into which all relevant four dimensional cosmologies can be locally embedded. We also argue on the choice of the cosmological frame. The choice that is simplest and most convenient in terms of dimensional analysis, amounts to a linearly expanding universe.

gr-qc↗
arXiv2012

Possible Connection between Dark Energy and Electromagnetic Interactions

This paper has been withdrawn by the authors. Please see [arXiv:1208.3224]. We investigate a model where dark energy is caused by the photon field coupling to gravitation. The cosmological background expectation value of the electromagnetic scalar potential generates the Planck mass as well as causing an exponential expansion which is identified with dark energy. The Higgs-like mechanism for the vector potential predicts the photon mass to be exactly zero.

gr-qc↗
arXiv2012

Electromagnetic Origin for Planck Mass and Dark Energy

The origin of dark energy remains to be one of the challenges of modern cosmology. We modify Jordan-Brans-Dicke theory using a vector field instead of a scalar field and theory becomes similar to a simple Einstein-aether theory. The time component of the vector field picks up a cosmological background value. Identifying the vector field to be the photon field, a small photon mass leads to late time inflation. The time dependent background electrical potential of the photon permeates the universe and explains the weakness of the gravitational interaction by coupling to curvature. This theory relates the smallness of the photon mass to the smallness of the Hubble parameter. The model predicted photon mass is far below observational constraints.

gr-qc↗
arXiv2009

Quantum Mechanical Disclosure of the Classical Adiabatic Constancy of PVg for an Ideal Gas, and for a Photon Gas

Previously, we established a connection between the macroscopic classical laws of gases and the quantum mechanical description of molecules of an ideal gas (T. Yarman et al. arXiv:0805.4494). In such a gas, the motion of each molecule can be considered independently on all other molecules, and thus the macroscopic parameters of the ideal gas, like pressure P and temperature T, can be introduced as a result of simple averaging over all individual motions of the molecules. It was shown that for an ideal gas enclosed in a macroscopic cubic box of volume V, the constant, arising along with the classical law of adiabatic expansion, i.e. PV5/3=constant, can be explicitly derived based on quantum mechanics, so that the constant comes to be proportional to h^2/m; here h is the Planck Constant, and m is the relativistic mass of the molecule the gas is made of. In this article we show that the same holds for a photon gas, although the related setup is quite different than the previous ideal gas setup. At any rate, we come out with PV5/3 hc=constant, where c is the speed of light. No matter what the dimensions of the constants in question are different from each other, they are still rooted to universal constants, more specifically to h2 and to hc, respectively; their ratio, i.e. V1/3 h/mc, interestingly pointing to the de Broglie relationship's cast.

physics.class-ph↗
arXiv2008

Symmetry analysis and exact solutions of modified Brans-Dicke cosmological equations

We perform a symmetry analysis of modified Brans-Dicke cosmological equations and present exact solutions. We discuss how the solutions may help to build models of cosmology where, for the early universe, the expansion is linear and the equation of state just changes the expansion velocity but not the linearity. For the late universe the expansion is exponential and the effect of the equation of state on the rate of expansion is just to change the constant Hubble parameter.

gr-qc↗