Synopsis: And Then There Was One

Interactions between primordial photons and axions may be why the accepted model of nucleosynthesis overestimates the abundance of the isotope lithium-7.
Synopsis figure
ESA/NASA/JPL-Caltech

Astrophysicists currently favor cosmological models based on cold dark matter, which has the advantage of accurately predicting the observed abundance of most of the light elements synthesized after the big bang. The one troublemaker in the crowd is lithium-7, an isotope that is observed to be a factor of 2 to 3 less abundant than theory suggests. Better observations have in fact worsened the discrepancy, so what might explain this lithium-7 anomaly? In a paper in Physical Review Letters, Ozgur Erken and colleagues at the University of Florida, Gainesville, have now proposed a way out of the “lithium problem” with testable consequences.

Cold dark matter models generally invoke one or more hypothetical particles, often WIMPS (weakly interacting massive particles). However, some researchers favor a picture involving another as-yet-undetected candidate particle, a type of low-mass boson called the axion. In an unusual twist, researchers believe that if the axions are cold enough they might form a cosmological Bose-Einstein condensate. This BEC could interact with primordial photons and cool them down in an exchange of energy.

According to Erken et al., the predicted formation rate of lithium-7 in this scenario would be reduced by a factor of 2, bringing it more into line with observations. However, this modification to the theory raises the predicted number of neutrino species to more than six, well above the three species currently known. Fortunately, the Planck satellite launched in 2009 is expected to send back data that will nail down the effective number of neutrino types and put axion-photon interactions to the test. – David Voss


Announcements

More Announcements »

Subject Areas

AstrophysicsParticles and Fields

Previous Synopsis

Astrophysics

Tidal Disruption of a Star

Read More »

Next Synopsis

Biological Physics

Birth Rhythms

Read More »

Related Articles

Viewpoint: The First Sounds of Merging Black Holes
Cosmology

Viewpoint: The First Sounds of Merging Black Holes

Gravitational waves emitted by the merger of two black holes have been detected, setting the course for a new era of observational astrophysics. Read More »

Viewpoint: Extending an Alternative to Feynman Diagrams
Particles and Fields

Viewpoint: Extending an Alternative to Feynman Diagrams

A simplifying technique for calculating scattering amplitudes—the basis for predictions in particle physics experiments—has been extended to cover a class of effective quantum field theories. Read More »

Synopsis: Neutron Stars May Explain Gamma Ray Excess
Astrophysics

Synopsis: Neutron Stars May Explain Gamma Ray Excess

New models show that neutron stars—and not dark matter—could be responsible for an excess of gamma rays from the Milky Way’s center. Read More »

More Articles