Probing screened modified gravity with nonlinear structure formation

2018 ◽  
Vol 27 (04) ◽  
pp. 1830003 ◽  
Author(s):  
David F. Mota
Keyword(s):  
Structure Formation ◽  
Modified Gravity ◽  
Equivalence Principle ◽  
Velocity Dispersion ◽  
Power Spectra ◽  
Nonlinear Structure ◽  
Fifth Force ◽  
Modified Gravity Theories ◽  
Halo Masses ◽  
Screening Scale

We review the effects of modified gravity theories, in particular the symmetron and [Formula: see text] gravity, on the nonlinear regime of structure formation. In particular, we investigate the velocity dispersion of galaxy clusters as a function of the halo masses, how the matter power spectra depend on the coupling, range, and screening scale of the fifth force, and on possible ways of detecting violations of the equivalence principle using the mass inferred via lensing methods versus the mass inferred via dynamical methods. Furthermore, we show how one could use different voids statistics as one of the most promising probes of modified gravity.

Nonlinear structure formation in gravity theories beyond general relativity

2016 ◽  
Vol 31 (21) ◽  
pp. 1640007
Author(s):  
David F. Mota
Keyword(s):  
Structure Formation ◽  
Modified Gravity ◽  
Equivalence Principle ◽  
Velocity Dispersion ◽  
Power Spectra ◽  
Nonlinear Structure ◽  
Modified Gravity Theories ◽  
Gravity Theories ◽  
Halo Masses ◽  
Screening Scale

We investigate the effects of modified gravity theories, in particular, the symmetron and f(R) gravity, on the nonlinear regime of structure formation. In particular, we investigate the velocity dispersion of galaxy clusters as a function of the halo masses, how the matter power spectra depend on the coupling, range and screening scale of the fifth force, and on possible ways of detecting violations of the equivalence principle using the mass inferred via lensing methods versus the mass inferred via dynamical methods.

ON IMPLICATIONS OF EQUIVALENCE PRINCIPLE FOR MODIFIED GRAVITY THEORIES

2011 ◽  
Vol 20 (14) ◽  
pp. 2839-2845 ◽  
Author(s):  
M. M. SHEIKH-JABBARI
Keyword(s):  
Modified Gravity ◽  
Equivalence Principle ◽  
Riemann Curvature ◽  
Riemann Curvature Tensor ◽  
Lovelock Gravity ◽  
Modified Gravity Theory ◽  
Modified Gravity Theories ◽  
Levi Civita Connection ◽  
Gravity Theories ◽  
Einstein’S General Relativity

One of the manifestations of Einstein Equivalence Principle (EEP) is that a freely falling particle in a gravitational field is following a geodesic. In Einstein's general relativity (GR) this is built in the formulation by assuming the connection to be the Levi-Civita connection. The latter may, however, be demanded to be implied by the dynamics of a generic modified gravity theory, within the Palatini formulation. We show that for extensions of the Einstein GR which are described by a Lagrangian [Formula: see text], where gμν is the metric and Rμαβν is the Riemann curvature tensor, this manifestation of EEP is only fulfilled for a special class of Lagrangians, the Lovelock gravity theories. Our analysis also implies that within the above mentioned set of modified gravity theories only for Lovelock gravity theories metric and Palatini formulations are equivalent.

scholarly journals The impact of modified gravity on the Sunyaev-Zel’dovich effect

2020 ◽  
Author(s):  
Myles A Mitchell ◽  
Christian Arnold ◽  
César Hernández-Aguayo ◽  
Baojiu Li
Keyword(s):  
Galaxy Formation ◽  
Modified Gravity ◽  
Power Spectra ◽  
Substantial Effect ◽  
Formation Model ◽  
Modified Gravity Theories ◽  
Sunyaev Zel'dovich Effect ◽  
Normal Branch ◽  
Using Data ◽  
The Impact

Abstract We study the effects of two popular modified gravity theories, which incorporate very different screening mechanisms, on the angular power spectra of the thermal (tSZ) and kinematic (kSZ) components of the Sunyaev-Zel’dovich effect. Using the first cosmological simulations that simultaneously incorporate both screened modified gravity and a complete galaxy formation model, we find that the tSZ and kSZ power spectra are significantly enhanced by the strengthened gravitational forces in Hu-Sawicki f(R) gravity and the normal-branch Dvali-Gabadadze-Porrati model. Employing a combination of non-radiative and full-physics simulations, we find that the extra baryonic physics present in the latter acts to suppress the tSZ power on angular scales l ≳ 3000 and the kSZ power on all tested scales, and this is found to have a substantial effect on the model differences. Our results indicate that the tSZ and kSZ power can be used as powerful probes of gravity on large scales, using data from current and upcoming surveys, provided sufficient work is conducted to understand the sensitivity of the constraints to baryonic processes that are currently not fully understood.

scholarly journals Does the Cosmological Expansion Change Local Dynamics?

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1417
Author(s):  
Marcelo Schiffer
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Hubble Constant ◽  
Matter Content ◽  
Matter Distribution ◽  
Present Value ◽  
Field Equations ◽  
Local Dynamics ◽  
Cosmological Expansion ◽  
Modified Gravity Theories

It is a well-known fact that the Newtonian description of dynamics within Galaxies for its known matter content is in disagreement with the observations as the acceleration approaches a0≈1.2×10−10 m/s2 (slighter larger for clusters). Both the Dark Matter scenario and Modified Gravity Theories (MGT) fail to explain the existence of such an acceleration scale. Motivated by the closeness of the acceleration scale and the Hubble constant cH0≈10−9 h m/s2, we are led to analyze whether this coincidence might have a Cosmological origin for scalar-tensor and spinor-tensor theories by performing detailed calculations for perturbations that represent the local matter distribution on the top of the cosmological background. Then, we solve the field equations for these perturbations in a power series in the present value of the Hubble constant. As we shall see, for both theories, the power expansion contains only even powers in the Hubble constant, a fact that renders the cosmological expansion irrelevant for the local dynamics.

scholarly journals Cosmological nonlinear structure formation in full general relativity

2014 ◽  
Vol 90 (12) ◽  
Author(s):  
José M. Torres ◽  
Miguel Alcubierre ◽  
Alberto Diez-Tejedor ◽  
Darío Núñez
Keyword(s):  
General Relativity ◽  
Structure Formation ◽  
Nonlinear Structure

scholarly journals A logarithmic correction in the entropy functional formalism

2016 ◽  
Vol 25 (07) ◽  
pp. 1650080 ◽  
Author(s):  
Fayçal Hammad ◽  
Mir Faizal
Keyword(s):  
Quantum Gravity ◽  
Modified Gravity ◽  
Correction Term ◽  
Modified Theories Of Gravity ◽  
Logarithmic Correction ◽  
Functional Formalism ◽  
Entropy Formula ◽  
Entropy Functional ◽  
Modified Gravity Theories ◽  
Theories Of Gravity

The entropy functional formalism allows one to recover general relativity, modified gravity theories, as well as the Bekenstein–Hawking entropy formula. In most approaches to quantum gravity, the Bekenstein–Hawking’s entropy formula acquires a logarithmic correction term. As such terms occur almost universally in most approaches to quantum gravity, we analyze the effect of such terms on the entropy functional formalism. We demonstrate that the leading correction to the micro-canonical entropy in the entropy functional formalism can be used to recover modified theories of gravity already obtained with an uncorrected micro-canonical entropy. Furthermore, since the entropy functional formalism reproduces modified gravity, the rise of gravity-dependent logarithmic corrections turns out to be one way to impose constraints on these theories of modified gravity. The constraints found here for the simple case of an [Formula: see text]-gravity are the same as those obtained in the literature from cosmological considerations.

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