scholarly journals Renormalizability of Alternative Theories of Gravity: Differences between Power Counting and Entropy Argument

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 148
Author(s):  
Francesco Bajardi ◽  
Francesco Bascone ◽  
Salvatore Capozziello
Keyword(s):  
General Relativity ◽  
Teleparallel Gravity ◽  
Power Counting ◽  
Alternative Theories Of Gravity ◽  
Spherically Symmetric ◽  
Asymptotic Safety ◽  
Renormalizable Theory ◽  
Theories Of Gravity ◽  
Working Out ◽  
Alternative Theories

It is well known that General Relativity cannot be considered under the standard of a perturbatively renormalizable quantum field theory, but asymptotic safety is taken into account as a possibility for the formulation of gravity as a non-perturbative renormalizable theory. Recently, the entropy argument has however stepped into the discussion claiming for a “no-go” to the asymptotic safety argument. In this paper, we present simple counter-examples, considering alternative theories of gravity, to the entropy argument as further indications, among others, on the possible flows in the assumptions on which the latter is based. We considered different theories, namely curvature-based extensions of General Relativity as f(R), f(G), extensions of teleparallel gravity as f(T), and Horava–Lifshitz gravity, working out the explicit spherically symmetric solutions in order to make a comparison between power counting and the entropy argument. Even in these cases, inconsistencies were found.

scholarly journals Testing the Vainshtein mechanism using stars and galaxies

2015 ◽  
Vol 24 (12) ◽  
pp. 1544021 ◽  
Author(s):  
Jeremy Sakstein ◽  
Kazuya Koyama
Keyword(s):  
General Relativity ◽  
Solar System ◽  
Main Sequence ◽  
Alternative Theories Of Gravity ◽  
The Novel ◽  
Main Sequence Stars ◽  
Cosmic Expansion ◽  
Astrophysical Objects ◽  
Theories Of Gravity ◽  
Alternative Theories

The Vainshtein mechanism is of paramount importance in many alternative theories of gravity. It hides deviations from general relativity (GR) in the solar system while allowing them to drive the acceleration of the cosmic expansion. Recently, a class of theories have emerged where the mechanism is broken inside astrophysical objects. In this essay, we look for novel probes of these theories by deriving the modified properties of stars and galaxies. We show that main-sequence stars are colder, less luminous and more ephemeral than GR predicts. Furthermore, the circular velocities of objects orbiting inside galaxies are slower and the lensing of light is weaker. We discuss the prospects for testing these theories using the novel phenomena presented here in light of current astrophysical surveys.

scholarly journals ON GENERATING SOME KNOWN BLACK HOLE SOLUTIONS

2010 ◽  
Vol 25 (10) ◽  
pp. 835-842 ◽  
Author(s):  
F. RAHAMAN ◽  
MUBASHER JAMIL ◽  
A. GHOSH ◽  
K. CHAKRABORTY
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Alternative Theories Of Gravity ◽  
Dimensional Parameters ◽  
Theories Of Gravity ◽  
Alternative Theories ◽  
Black Hole Solutions

In this paper, we have presented an algorithm to generate various black hole solutions in general relativity and alternative theories of gravity. The algorithm involves few dimensional parameters that are assigned suitable values to specify the required black hole.

scholarly journals FOURTH-ORDER GRAVITY AND EXPERIMENTAL CONSTRAINTS ON EDDINGTON PARAMETERS

2006 ◽  
Vol 21 (30) ◽  
pp. 2291-2301 ◽  
Author(s):  
S. CAPOZZIELLO ◽  
A. STABILE ◽  
A. TROISI
Keyword(s):  
Experimental Data ◽  
General Relativity ◽  
Alternative Theories Of Gravity ◽  
Third Order ◽  
Definitive Answer ◽  
Order Polynomial ◽  
Theories Of Gravity ◽  
Definition Of ◽  
Ppn Parameters ◽  
Alternative Theories

PPN-limit of alternative theories of gravity represents a still controversial matter of debate and no definitive answer has been provided, up to now, about this issue. By using the definition of the PPN-parameters γ and β in terms of f(R) theories of gravity, we show that a family of third-order polynomial theories, in the Ricci scalar R, turns out to be compatible with the PPN-limit and the deviation from General Relativity, theoretically predicted, can agree with experimental data.

scholarly journals Scalarized black holes

2021 ◽  
Author(s):  
Jose Luis Blázquez-Salcedo ◽  
Burkhard Kleihaus ◽  
Jutta Kunz
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Scalar Field ◽  
Alternative Theories Of Gravity ◽  
Gravitational Action ◽  
Theories Of Gravity ◽  
Bonnet Term ◽  
Alternative Theories ◽  
Black Hole Solutions

AbstractBlack holes represent outstanding astrophysical laboratories to test the strong gravity regime, since alternative theories of gravity may predict black hole solutions whose properties may differ distinctly from those of general relativity. When higher curvature terms are included in the gravitational action as, for instance, in the form of the Gauss–Bonnet term coupled to a scalar field, scalarized black holes result. Here we discuss several types of scalarized black holes and some of their properties.

scholarly journals TESTS OF GENERAL RELATIVITY AND ALTERNATIVE THEORIES OF GRAVITY USING GRAVITATIONAL WAVE OBSERVATIONS

2013 ◽  
Vol 22 (01) ◽  
pp. 1341012 ◽  
Author(s):  
K. G. ARUN ◽  
ARCHANA PAI
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Strong Field ◽  
Information Matrix ◽  
Simons Theory ◽  
Alternative Theories Of Gravity ◽  
Newtonian Theory ◽  
Theories Of Gravity ◽  
Model Independent ◽  
Alternative Theories

Gravitational wave (GW) observations of coalescing compact binaries will be unique probes of strong-field, dynamical aspects of relativistic gravity. We present a short review of various schemes proposed in the literature to test general relativity (GR) and alternative theories of gravity using inspiral waveforms. Broadly these schemes may be classified into two types: model dependent and model independent. In the model dependent category, GW observations are compared against a specific waveform model representative of a particular theory or a class of theories such as scalar-tensor theories, dynamical Chern–Simons theory and massive graviton theories. Model independent tests are attempts to write down a parametrized gravitational waveform where the free parameters take different values for different theories and (at least some of) which can be constrained by GW observations. We revisit some of the proposed bounds in the case of downscaled LISA configuration (eLISA) and compare them with the original LISA configuration. We also compare the expected bounds on alternative theories of gravity from ground-based and space-based detectors and find that space-based GW detectors can test GR and other theories of gravity with unprecedented accuracies. We then focus on a recent proposal to use singular value decomposition of the Fisher information matrix to improve the accuracies with which post-Newtonian theory can be tested. We extend those results to the case of space-based detector eLISA and discuss its implications.

scholarly journals Radioscience simulations in general relativity and in alternative theories of gravity

2012 ◽  
Vol 29 (23) ◽  
pp. 235027 ◽  
Author(s):  
A Hees ◽  
B Lamine ◽  
S Reynaud ◽  
M-T Jaekel ◽  
C Le Poncin-Lafitte ◽  
...  
Keyword(s):  
General Relativity ◽  
Alternative Theories Of Gravity ◽  
Theories Of Gravity ◽  
Alternative Theories

scholarly journals Perturbations of Keplerian orbits in stationary spherically symmetric spacetimes

2014 ◽  
Vol 23 (05) ◽  
pp. 1450049 ◽  
Author(s):  
Matteo Luca Ruggiero
Keyword(s):  
Power Laws ◽  
Approximation Order ◽  
Alternative Theories Of Gravity ◽  
Spherically Symmetric ◽  
Central Mass ◽  
Secular Variations ◽  
Analytic Expressions ◽  
Theories Of Gravity ◽  
The Impact ◽  
Alternative Theories

We study spherically symmetric perturbations determined by alternative theories of gravity to the gravitational field of a central mass in General Relativity (GR). In particular, we focus on perturbations in the form of power laws and calculate their effect on the secular variations of the orbital elements of a Keplerian orbit. We show that, to lowest approximation order, only the argument of pericenter and mean anomaly undergo secular variations; furthermore, we calculate the variation of the orbital period. We give analytic expressions for these variations which can be used to constrain the impact of alternative theories of gravity.

scholarly journals Embedding Black Holes and Other Inhomogeneities in the Universe in Various Theories of Gravity: A Short Review

Universe ◽  
2018 ◽  
Vol 4 (10) ◽  
pp. 109 ◽  
Author(s):  
Valerio Faraoni
Keyword(s):  
Black Holes ◽  
Short Review ◽  
Alternative Theories Of Gravity ◽  
Spherically Symmetric ◽  
Event Horizons ◽  
Interesting Class ◽  
Theories Of Gravity ◽  
The Universe ◽  
Alternative Theories ◽  
Trapping Horizons

Classic black hole mechanics and thermodynamics are formulated for stationary black holes with event horizons. Alternative theories of gravity of interest for cosmology contain a built-in time-dependent cosmological “constant” and black holes are not stationary. Realistic black holes are anyway dynamical because they interact with astrophysical environments or, at a more fundamental level, because of backreaction by Hawking radiation. In these situations, the teleological concept of event horizon fails and apparent or trapping horizons are used instead. Even as toy models, black holes embedded in cosmological “backgrounds” and other inhomogeneous universes constitute an interesting class of solutions of various theories of gravity. We discuss the known phenomenology of apparent and trapping horizons in these geometries, focusing on spherically symmetric inhomogeneous universes.

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