Synopsis: Do dark matter particles interact?

The spatial distribution of dark matter around different types of galaxies can be explained if its particles scatter one another, theorist suggest, but only if the interaction has a finite range.
Synopsis figure
Credit: NASA/ESA/C. Conselice (University of Nottingham)

Precise cosmological observations suggest that about three-quarters of the mass-energy of the universe is a poorly understood “dark energy” that drives an overall expansion. Most of the remainder is called “dark matter,” which interacts with light and ordinary matter only through its gravity. The clumpiness of dark matter in the early universe, still recorded in tiny variations in the microwave background, is thought to have seeded the coalescence of matter into the cosmological structures we see today.

Since dark matter is also usually thought to interact with itself only through the gravitational force, simulations predict that it will pile up dramatically within all large clumps of matter. This sharply peaked dark-matter distribution matches that inferred from observations of clusters of galaxies. But in “small” structures, such as dwarf galaxies, the dynamics of stars indicate instead a more spread-out core. In a paper appearing in Physical Review Letters, Abraham Loeb of Harvard and Neil Weiner of New York University suggest that cores of dark matter, as opposed to peaks, arise if dark-matter particles scatter one another. This idea was proposed a decade ago, but failed to explain why larger structures have no core. Now, Loeb and Weiner show that, if the interaction (which for now has an unknown origin) has a finite range, it has a weaker effect on particles moving rapidly relative to each other, which they are expected to do in large structures but not in the smallest ones. – Don Monroe


Announcements

More Announcements »

Subject Areas

Particles and FieldsCosmology

Previous Synopsis

Particles and Fields

A “bump” in the data

Read More »

Related Articles

Viewpoint: The Littlest Liquid
Particles and Fields

Viewpoint: The Littlest Liquid

The plasma of quarks and gluons that forms when a proton collides with a lead nucleus has unexpected liquidlike properties. Read More »

Synopsis: Mid-Infrared Lasers Probe Atomic Structure
Atomic and Molecular Physics

Synopsis: Mid-Infrared Lasers Probe Atomic Structure

Researchers have imaged the structure and the response of atoms and molecules with powerful mid-infrared electric fields. Read More »

Synopsis: Ripples in a BEC Pond
Particles and Fields

Synopsis: Ripples in a BEC Pond

Atoms in a condensate could be used to image the quantum wave function of an impurity charge. Read More »

More Articles