Dynamics of quasi de Sitter and linear combination of exponential models in extended gravity

We investigate the consequences of incepting the Bianchi type I metric in the [Formula: see text] gravity theory field equations. We particularly derive solutions for a matter-dominated universe. From such a scenario, it is possible to predict a late-time de Sitter universe. Moreover, depending on the numerical fitting function for the scale factor, the universe is predicted to bounce and evade the Big Bang singularity.

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Stable compact spacelike hypersurfaces in the de Sitter space as maxima of a linear combination of area and volume

manuscripta mathematica ◽

10.1007/s00229-018-1047-7 ◽

2018 ◽

Vol 159 (1-2) ◽

pp. 229-245

Author(s):

Marco A. L. Velásquez ◽

Henrique F. de Lima ◽

Jonatan F. da Silva ◽

Arlandson M. S. Oliveira

Keyword(s):

Linear Combination ◽

De Sitter Space ◽

De Sitter ◽

Spacelike Hypersurfaces ◽

Area And Volume

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Quasinormal Modes of Extended Gravity Black Holes

10.20944/preprints202009.0669.v1 ◽

2020 ◽

Author(s):

Abdul Jawad ◽

Shahid Chaudhary ◽

Muhammad Yasir ◽

Ali Övgün ◽

İzzet Sakallı

Keyword(s):

Black Holes ◽

Black Hole ◽

Relaxation Rate ◽

Quasinormal Modes ◽

Linear Functions ◽

De Sitter ◽

Extended Gravity ◽

Dimensional Black Hole ◽

Ads Spacetime ◽

Charge Parameter

Black hole's quasinormal frequencies are basically the complex numbers which provide information about the relaxation of perturbations and depend on the characteristics of the spacetime and types of perturbations. In this paper, we evaluate the quasinormal modes of Hayward black hole in Einstein Gauss-Bonnet gravity, Hayward black hole in anti-de Sitter space (AdS) spacetime, and 4-dimensional black hole in Einstein-Lovelock gravity. By utilizing the WKB resonance technique, we examine the quasinormal modes frequencies $\omega$ by shifting the charge parameter $Q$ (it is also identified with the cosmological constant), circular harmonic index $l$, and mass of scalar field $m$. We also study the relaxation rate for those black holes and find out that the relaxation rate increases with increasing values of $Q$. We observe that real and imaginary components of the quasinormal modes are not linear functions as similar to Reisnner Nordstr\"{o}m-AdS. For large values of charge, quasinormal ringing becomes slower to settle down to thermal equilibrium and hence the frequency of the oscillation becomes smaller.

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Curve Estimation Modeling for Predictions of the Novel Coronavirus (Covid-19) Epidemic in Nigeria

Healthy-Mu Journal ◽

10.35747/hmj.v4i1.545 ◽

2020 ◽

Vol 4 (1) ◽

pp. 1

Author(s):

Christian Ebere Enyoh ◽

Andrew Wirnkor Verla ◽

Chidi Edbert Duru ◽

Emmanuel Chinedu Enyoh ◽

Budi Setiawan

Keyword(s):

State Governments ◽

The Novel ◽

Curve Estimation ◽

Exponential Models ◽

Inverse Models ◽

Forward Prediction ◽

S Curve ◽

Novel Coronavirus ◽

Best Fit ◽

Official Data

Based on the official Nigeria Centre for Disease Control (NCDC) data, the current research paper modeled the confirmed cases of the novel coronavirus disease 2019 (COVID-19) in Nigeria. Ten different curve regression models including linear, logarithmic, inverse, quadratic, cubic, compound, power, S-curve, growth, and exponential were used to fit the obtained official data. The cubic (R2 = 0.999) model gave the best fit for the entire country. However, the growth and exponential had the lowest standard error of estimate (0.958) and thus may best be used. The equations for these models were e0.78897+0.0944x and 2.2011e0.0944x respectively. In terms of confirmed cases in individual State, quadratic, cubic, compound, growth, power and exponential models generally best describe the official data for many states except for the state of Kogi which is best fitted with S-curve and inverse models. The error between the model and the official data curve is quite small especially for compound, power, growth and exponential models. The computed models will help to realized forward prediction and backward inference of the epidemic situation in Nigeria, and the relevant analysis help Federal and State governments to make vital decisions on how to manage the lockdown in the country.

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Recognition by Linear Combination of Models

10.21236/ada224268 ◽

1989 ◽

Cited By ~ 17

Author(s):

Shimon Ullman ◽

Ronen Basri

Keyword(s):

Linear Combination

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Estimating the Number of Signals of the Damped Exponential Models

10.21236/ada379088 ◽

1999 ◽

Author(s):

Debasis Kundu ◽

Amit Mitra

Keyword(s):

Exponential Models

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Cosmological spacetimes

10.1093/oso/9780198786399.003.0057 ◽

2018 ◽

Author(s):

Nathalie Deruelle ◽

Jean-Philippe Uzan

Keyword(s):

Cosmological Model ◽

Large Scale ◽

Cosmic Time ◽

De Sitter ◽

Matter Distribution ◽

Observable Universe ◽

Cosmological Principle ◽

Riemannian Spacetime ◽

The Universe ◽

Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

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