Related Experiment Video
Updated: May 24, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Axion dark matter and cosmological parameters.
1Department of Physics, University of Florida, Gainesville, Florida 32611, USA.
Physical Review Letters
|March 10, 2012
Summary
Photon cooling after the Big Bang can resolve the lithium abundance problem. Colder axions in a Bose-Einstein condensate may enable this cooling, predicting a high effective number of neutrinos.
Area of Science:
- Cosmology
- Particle Physics
Background:
- The primordial abundance of Lithium-7 (⁷Li) shows a significant discrepancy between observational data and theoretical predictions from Big Bang nucleosynthesis.
- Achieving the necessary photon cooling before cosmic recombination is challenging under standard cosmological models.
Purpose of the Study:
- To propose a mechanism for photon cooling that resolves the cosmological lithium abundance problem.
- To investigate the role of dark matter axions in facilitating this cooling process.
Main Methods:
- Investigating the thermal contact between Bose-Einstein condensed axions and photons.
- Analyzing the impact of axion-photon thermalization on early universe thermodynamics.
Main Results:
- Photon cooling after Big Bang nucleosynthesis and before recombination can reconcile the observed and predicted ⁷Li abundances.
- Bose-Einstein condensed axions provide a viable mechanism for achieving this photon cooling through thermal contact.
- The proposed mechanism predicts a higher effective number of neutrinos (N_eff) than currently inferred from cosmic microwave background anisotropy data.
Conclusions:
- The axion Bose-Einstein condensate model offers a potential solution to the cosmic lithium problem.
- This model has testable implications for cosmological parameters, specifically N_eff, which can be constrained by future cosmic microwave background observations.
Related Concept Videos
01:21Schwarzschild Radius and Event Horizon
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 velocity with the...
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 velocity with the...
01:10Detection of Black Holes
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...
01:18Conservation of Angular Momentum: Application
A system's total angular momentum remains constant if the net external torque acting on the system is zero. Examples of such systems include a freely spinning bicycle tire that slows over time due to torque arising from friction, or the slowing of Earth's rotation over millions of years due to frictional forces exerted on tidal deformations. However in the absence of a net external torque, the angular momentum remains conserved. The conservation of angular momentum principle requires a change...
01:11Angular Momentum about an Arbitrary Axis
Imagine a rigid body with a mass denoted as 'm', which has its center of mass at point G and is rotating around an inertial reference frame. The angular momentum at an arbitrary point P can be calculated by taking the cross product of the position vector and linear momentum vector for each individual mass element.
The velocity of a mass element comprises its translational velocity and the relative velocity instigated by the body's rotation. Substituting the velocity equation into the angular...
The velocity of a mass element comprises its translational velocity and the relative velocity instigated by the body's rotation. Substituting the velocity equation into the angular...
01:12Reduced Mass Coordinates: Isolated Two-body Problem
In classical mechanics, the two-body problem is one of the fundamental problems describing the motion of two interacting bodies under gravity or any other central force. When considering the motion of two bodies, one of the most important concepts is the reduced mass coordinates, a quantity that allows the two-body problem to be solved like a single-body problem. In these circumstances, it is assumed that a single body with reduced mass revolves around another body fixed in a position with an...
01:09Angular Momentum and Principle Axes of Inertia
The concept of angular momentum for a solid structure is illustrated as the cumulative result of the cross-product of the position vector of the mass element and the cross-product of the body's angular velocity with the position vector.
To put this equation into simpler terms, it can be reconfigured using rectangular coordinates. This involves choosing an alternative set of XYZ axes that are arbitrarily inclined with respect to the reference frame. The process of deriving the rectangular...
To put this equation into simpler terms, it can be reconfigured using rectangular coordinates. This involves choosing an alternative set of XYZ axes that are arbitrarily inclined with respect to the reference frame. The process of deriving the rectangular...