Related Experiment Video
Updated: Nov 19, 2025
10:27
Contrast-Matching Detergent in Small-Angle Neutron Scattering Experiments for Membrane Protein Structural Analysis and Ab Initio Modeling
Published on: October 21, 2018
12.7K
Testing viable f(R) models with the angular-diameter distance to compact quasar cores.
Joseph Sultana1, Fulvio Melia2, Demosthenes Kazanas3
1Department of Mathematics, Faculty of Science, University of Malta, Msida MSD2080, Malta.
Physical Review. D. (2016)
|January 29, 2021
Summary
We analyzed f(R) gravity models as alternatives to dark energy. By calculating the redshift of maximum angular diameter distance (z_max), we found most models align with observations, offering a new way to test modified gravity theories.
Area of Science:
- Cosmology and astrophysics
- Modified gravity theories
- General Relativity
Background:
- Dark energy is a hypothetical form of energy believed to permeate all of space.
- f(R) gravity models offer an alternative to dark energy within modified gravity theories.
- The angular diameter distance (d_A) is a key cosmological observable.
Purpose of the Study:
- To compute the redshift (z_max) where angular diameter distance (d_A) reaches its maximum for popular f(R) models.
- To compare these theoretical predictions with the observed z_max value (1.70 ± 0.20).
- To test the viability of f(R) models against standard Lambda Cold Dark Matter (ΛCDM) cosmology.
Main Methods:
- Calculating z_max for various f(R) gravity models.
- Comparing model predictions with the model-independent measurement of z_max from compact quasar cores.
- Quantifying observational differences between f(R) models and ΛCDM.
Main Results:
- Most popular f(R) models are consistent with the observed z_max within 1-sigma.
- The turning point z_max provides a method to differentiate between f(R) models and ΛCDM.
- The Hu-Sawicki f(R) model exacerbates the tension between ΛCDM predictions and observations, while the Starobinky model reduces it.
Conclusions:
- The z_max measurement offers a powerful tool for testing and prioritizing alternative gravity theories.
- f(R) models show varying degrees of success in mitigating cosmological tensions.
- Future improvements in measurement precision will further refine our ability to distinguish between modified gravity scenarios.
Related Concept Videos
01:21Schwarzschild Radius and Event Horizon
2.4K
No object with a finite mass can travel faster than the speed of light in a vacuum. This fact has an interesting consequence in the domain of extremely high gravitational fields.
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape...
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape...
2.4K
01:14Gravitation Between Spherically Symmetric Masses
1.1K
The gravitational potential energy between two spherically symmetric bodies can be calculated from the masses and the distance between the bodies, assuming that the center of mass is concentrated at the respective centers of the bodies.
1.1K
01:10Detection of Black Holes
2.4K
Although black holes were theoretically postulated in the 1920s, they remained outside the domain of observational astronomy until the 1970s.
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
2.4K
01:05Relating Angular And Linear Quantities - II
6.0K
In the case of circular motion, the linear tangential speed of a particle at a radius from the axis of rotation is related to the angular velocity by the relation:
6.0K
01:15Distance Corrections
164
To achieve precise distance measurements, especially in surveying and construction, certain corrections must be applied to account for potential sources of error like the standardization errors, temperature variations, and slope adjustments.Standardization error emerges when measurement equipment undergoes changes, such as wear, repairs, or weather impacts. To address this, surveyors compare the equipment’s readings to a standard. This process identifies any deviation that might lead to...
164
01:12Radius of Gyration of an Area
2.3K
The second moment of area, also known as the moment of inertia of area, is a crucial factor in understanding an object's resistance against bending deformation, or stiffness. To accurately estimate the second moment of area along any axis, one needs to concentrate all areas associated with that object into a thin strip, which should be placed parallel to that particular axis.
2.3K