Force Free Magnetic Field and Modifications in Kerr Black Hole

A recent research presented a solution for a Schwarzschild black hole with a force-free magnetic field showing how the canonical form of background metric changes, Found. Phys. 52 (2022) 4, 93. Therefore, it is logical that this research seeks modified solutions for the Kerr black hole as well. The goal of this paper is, thereby, to pinpoint an exact solution for the Kerr black holes perturbed by force-free magnetic fields. However, to do this we use a well-known tetrad formalism and obtain an explicit expression for the electromagnetic strength tensor in the background metric, that is Kerr, based on the tangent space calculations. Analyzing the stress-energy tensor reveals the perturbed factors in the metric that allow us to understand better the physics of the disks around massive and supermassive black holes. These results show that it is not enough to depend solely on perturbation theory set against the background metric, without considering the backreaction of the force-free magnetufluid on it. This research indicates the necessity of studying the impact of force-free magnetic fields on the structure and evolution of mysterious cosmic objects.Comment: 11 page

Schwarzschild black hole perturbed by a force-free magnetic field

We envisage a black hole perturbed by a force-free magnetic field (FFMF) outside and attempt to determine its structure. We suppose the metric that describes this black hole is of the static spherical type, that is Schwarzschild, and the energy-momentum tensor emanating from an FFMF source perturbs this background metric, in this regard one can imagine a magnetic accretion disk around the black hole. By solving the equations for such a configuration, we will show that in addition to modifying the diagonal elements of the background metric, we will also see the non-zeroing of the off-diagonal elements of the general metric, one of the immediate consequences of which will be a static to stationary transition. "Space-time tells matter how to move; matter tells space-time how to curve" -- John Archibald WheelerComment: 12 Pages; Based on published versio

The effect of de Sitter like background on increasing the zero point budget of dark energy

During this work, using subtraction renormalization mechanism, zero point quantum fluctuations for bosonic scalar fields in a de-Sitter like background are investigated. By virtue of the observed value for spectral index, $n_s(k)$, for massive scalar field the best value for the first slow roll parameter, $\epsilon$, is achieved. In addition the energy density of vacuum quantum fluctuations for massless scalar field is obtained. The effects of these fluctuations on other components of the Universe are studied. By solving the conservation equation, for some different examples, the energy density for different components of the Universe are obtained. In the case which, all components of the Universe are in an interaction, the different dissipation functions, $\tilde{Q}_{i}$, are considered. The time evolution of ${\rho_{DE}(z)}/{\rho_{cri}(z)}$ shows that $\tilde{Q}=3 \gamma H(t) \rho_{m}$ has best agreement in comparison to observational data including CMB, BAO and SNeIa data set.Comment: 11 pages, 3 figure

Non-commutative and commutative vacua effects in a scalar torsion scenario

In this work, the effects of non-commutative and commutative vacua on the phase space generated by a scalar field in a scalar torsion scenario are investigated. For both classical and quantum regimes, the commutative and non-commutative cases are compared. To take account the effects of non-commutativity, two well known non-commutative parameters, $\theta$ and $\beta,$ are introduced. It should be emphasized, the effects of $\beta$ which is related to momentum sector has more key role in comparison to $\theta$ which is related to space sector. Also the different boundary conditions and mathematical interpretations of non-commutativity are explored.Comment: 10 pages, Accepted for publication in Physics Letters B (July/30/2015

Vacuum Zero Point Energy and its Statistical Correlations in dS Background

We study the vacuum zero point energy associated to a scalar field with an arbitrary mass and conformal coupling in a dS background. Employing dimensional regularization scheme, we calculate the regularized zero point energy density, pressure and the trace of the energy momentum tensor. It is shown that the classical relation $\langle T \rangle =-4 \langle \rho \rangle$ for the vacuum stress energy tensor receives anomalous quantum correction which depends on the mass and the conformal coupling while the relation $\langle \rho \rangle = - \langle P \rangle$ does hold. We calculate the density contrast associated to the vacuum zero point energy and show that $\delta \rho \sim \langle \rho \rangle$ indicating an inhomogeneous and non-perturbative distribution of the zero point energy. Finally, we calculate the skewness associated to the distribution of the zero point energy and pressure and show that they are highly non-Gaussian.Comment: 23 page

Interacting scalar tensor cosmology in light of SNeIa, CMB, BAO and OHD observational data sets

During this work, an interacting chameleon like scalar field scenario, by considering SNeIa, CMB, BAO and OHD data sets is investigated. In fact, the investigation is realized by introducing an ansatz for the effective dark energy equation of state, which mimics the behaviour of chameleon like models. Based on this assumption, some cosmological parameters including Hubble, deceleration and coincidence parameters in such mechanism are analysed. It is realized that, to estimate the free parameters of a theoretical model, by regarding the systematic errors it better the whole of the above observational data sets to be considered. In fact, if one considers SNeIa, CMB and BAO but disregards OHD it maybe leads to different results. Also to get a better overlap between the counters with the constraint $\chi _{\rm{m}}^2\leq 1$, the $\chi _{\rm{T}}^2$ function could be re-weighted. The relative probability functions are plotted for marginalized likelihood $\mathcal{L} (\Omega_{\rm{m0}} ,\omega_1, \beta)$ according to two dimensional confidence levels $68.3\%$, $90\%$ and $95.4\%$. Meanwhile, the value of free parameters which maximize the marginalized likelihoods using above confidence levels are obtained. In addition, based on these calculations the minimum value of $\chi^2$ based on free parameters of an ansatz for the effective dark energy equation of state are achieved.Comment: Accepted by the European Physical Journal C. 13 pages, 17 figures and 4 tables