scholarly journals Testing wormhole solutions in extended gravity through the Poynting-Robertson effect

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
Vittorio De Falco ◽  
Emmanuele Battista ◽  
Salvatore Capozziello ◽  
Mariafelicia De Laurentis
Keyword(s):  
Extended Gravity

scholarly journals Import Flows of Bangladesh: Gravity Model Approach under Panel Data Methodology

2012 ◽  
Vol 60 (2) ◽  
pp. 153-157 ◽  
Author(s):  
Mili Roy ◽  
Md. Israt Rayhan
Keyword(s):  
Panel Data ◽  
Gravity Model ◽  
Cross Section ◽  
Time Series Data ◽  
Random Effect ◽  
Least Square ◽  
Series Data ◽  
Ordinary Least Square ◽  
Extended Gravity ◽  
Trading Partners

In counterpoint to export growth, Bangladesh import growth has remained much less strong, despite impressive progress in import liberalization. This study gives an overview of different methodologies related to gravity model analysis in Bangladesh’s import flow. A pooled cross section and time series data were analyzed to incorporate the country specific heterogeneity in country pair trading partners. The import flows are justified by the basic gravity model since Bangladesh’s imports are positively significant by the economy size and inversely related to trade barrier. Accordingly, we have analyzed pooled ordinary least square, fixed effect, random effect. This study also explores extended gravity model using several variables in the light of gravity model panel data approach. Bangladesh’s import is determined by the home and foreign country’s gross domestic product and exchange rate. In addition, Cross section results show that regional trade arrangement which is South Asian Association for Regional Co-operation and border are significant for Bangladesh’s importimplies that Bangladesh should import more from intra regional country and also should import from India.DOI: http://dx.doi.org/10.3329/dujs.v60i2.11485 Dhaka Univ. J. Sci. 60(2): 153-157, 2012 (July)  

scholarly journals Angular Momentum and Energy Transfer in a Whitehead's Theory of Gravity

2018 ◽  
Author(s):  
Luis Acedo
Keyword(s):  
Angular Momentum ◽  
Major Axis ◽  
Astronomical Unit ◽  
Net Energy ◽  
Semi Major Axis ◽  
Extended Gravity ◽  
First Case ◽  
Planetary Orbits ◽  
Theory Of Gravity ◽  
New Phenomena

In this paper, we revisit a modified version of the classical Whitehead's theory of gravity in which all possible bilinear forms are considered to define the corresponding metric. Although, this is a linear theory that fails to give accurate results for the most sophisticated predictions of general relativity, such as gravity waves, it can still provide a convenient framework to analyze some new phenomena in the Solar System. In particular, recent development in the accurate tracking of spacecraft and the ephemerides of planetary positions have revealed certain anomalies in relation with our standard paradigm for celestial mechanics. Among them the so-called flyby anomaly and the anomalous increase of the astronomical unit play a prominent role. In the first case the total energy of the spacecraft changes during the flyby and a secular variation of the semi-major axis of the planetary orbits is found in the second anomaly. For this to happen it seems that a net energy and angular momentum transfer is taken place among the orbiting and the central body. We evaluate the total transfer per revolution for a planet orbiting the Sun in order to predict the astronomical unit anomaly in the context of Whitehead's theory. This could lead to a more deeply founded hypothesis for an extended gravity model.

scholarly journals Light bending in F[g(□)R] extended gravity theories

2018 ◽  
Vol 780 ◽  
pp. 54-60 ◽  
Author(s):  
Breno L. Giacchini ◽  
Ilya L. Shapiro
Keyword(s):  
Extended Gravity ◽  
Light Bending ◽  
Gravity Theories

Shadow from a rotating black hole in an extended gravity

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040060
Author(s):  
Vjacheslav Prokopov ◽  
Stanislav Alexeyev
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Rotating Black Hole ◽  
Extended Gravity ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Extended Theories

We focus on the consequences of that the Event Horizon Telescope obtained images of the black hole shadow in the center of the M87 galaxy. We show that to test extended theories of gravity the improving of the resolution by 3 orders is necessary. In addition it is demonstrated that the rotation distorts the shape of the shadow and corrections from the extended gravity may affect on this distortion.

Causality of 3D extended gravity theories

2019 ◽  
Vol 34 (16) ◽  
pp. 1950122
Author(s):  
Meguru Komada
Keyword(s):  
Shock Wave ◽  
Three Dimensional ◽  
Massive Gravity ◽  
Gravity Theory ◽  
Delay Effect ◽  
Fundamental Physics ◽  
Extended Gravity ◽  
3D Gravity ◽  
Gravity Theories ◽  
Time Delay Effect

Causality is one of the most important properties to understand gravity theories. It gives us not only a method to confirm that the gravity theories are really consistent, but also gives implications about the properties which unknown fundamental physics should obey. We investigate the causality of three-dimensional (3D) gravity theories, which are considered to be important, by using the Shapiro time delay effect in the Shock wave geometry. One of such gravity theories is the Zwei-Dreibein Gravity (ZDG) theory, which is a consistent 3D gravity theory. In ZDG theory, the serious problems can be removed that have appeared in another important gravity theory called New Massive Gravity (NMG). We study whether the ZDG theory could preserve the causality without losing the above good properties and how the causality structure is related to the structure of the NMG theory.

Extended gravity at galaxy cluster’s scales

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040057
Author(s):  
Stanislav Alexeyev ◽  
Kirill Kovalkov
Keyword(s):  
Cosmological Constant ◽  
Galaxy Cluster ◽  
The Real ◽  
Astrophysical Data ◽  
Extended Gravity

The new result on Horndeski model asymptotic at Galaxy cluster scales is presented. As the obtained constraint for [Formula: see text] has the same order as for the real cosmological constant we demonstrate that at extra-galactic scales Horndeski model is consistent with existing astrophysical data.

scholarly journals Cosmological framework for renormalization group extended gravity at the action level

2020 ◽  
Vol 80 (5) ◽  
Author(s):  
Nicolas R. Bertini ◽  
Wiliam S. Hipólito-Ricaldi ◽  
Felipe de Melo-Santos ◽  
Davi C. Rodrigues
Keyword(s):  
Renormalization Group ◽  
Extended Gravity
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