Synopsis: Cosmic consistency check

At the current time, we cannot tell if Einstein’s cosmological constant—or some other theory—is the correct description for dark energy in the Universe. A proposed measure based on existing data may help us to better distinguish these ideas.
Synopsis figure

The leading interpretation of why the expansion of the Universe is apparently accelerating is the presence of dark energy. Long before the supernova observations that indicated an accelerating Universe, Einstein proposed the idea of a cosmological constant, which says that dark energy homogeneously fills all of space as a constant energy density. Numerous other ideas, involving the variation of dark energy in time and space, have gained substantial interest. However, it is difficult to distinguish among them with either present data or those expected to be available in the next few years.

The main sources of these data are measurements of how the luminosity of supernovae depends on redshift and therefore distance. To interpret these data with dark-energy theories requires necessarily oversimplified parametrizations and assumptions (based on inferences from other data) about the matter density and curvature of the Universe. In a paper appearing in Physical Review Letters, Caroline Zunckel of Oxford University and Chris Clarkson of the University of Cape Town develop a new approach, which could more independently distinguish among dark-energy theories. They introduce a new measure, based only on luminosity-distance data, which does not require knowledge of the cosmic matter density and would be zero if the cosmological constant is correct. Conversely, finding a nonzero value would indicate that some other explanation of dark energy must be valid.

This test alone would be unable to firmly establish the cosmological constant as the unique picture of dark energy, but it would considerably narrow the possibilities. – Stanley Brown


Announcements

More Announcements »

Subject Areas

Cosmology

Previous Synopsis

Next Synopsis

Optics

Waving, one by one

Read More »

Related Articles

Viewpoint: Weighing Dark Matter Halos with the Cosmic Microwave Background
Astrophysics

Viewpoint: Weighing Dark Matter Halos with the Cosmic Microwave Background

Gravitational lensing by foreground dark matter halos leaves an observable imprint on the cosmic microwave background, which can be used to determine their masses Read More »

Viewpoint: A Clearer View of a Dusty Sky
Astrophysics

Viewpoint: A Clearer View of a Dusty Sky

A signal in the cosmic microwave background thought to be evidence of inflation in the early Universe can be explained by interstellar dust. Read More »

Synopsis: Particle Weighing in the Early Universe
Astrophysics

Synopsis: Particle Weighing in the Early Universe

The spectrum of a distant quasar reveals no sign of changes in the mass ratio of the proton and the electron over 12 billion years, constraining dark energy theories. Read More »

More Articles