Universe May Hide Vast Antimatter

New theories suggest cosmic antimatter is far more common than previously thought.

For decades, the standard view was that matter vastly outnumbers antimatter, an imbalance called "baryon asymmetry." However, new theoretical studies challenge this idea.

These studies explore various ways the universe could have produced matter and antimatter in the first place, a process called "baryogenesis."

Exploring Baryogenesis Scenarios

Researchers investigated how:

Heavy particles break down.
Symmetry between particles and antiparticles (C and CP) might have been broken.
Conditions deviated from a perfect, even temperature in the early universe.

The study explored different "baryogenesis scenarios," which are like recipes for how matter and antimatter might have formed in the early universe. These include ideas like "electroweak baryogenesis" and "baryogenesis through evaporation of primordial black holes."

The scientists analyzed existing theories and observations, rather than conducting experiments.

Potential "Anti-Objects" and Their Signals

Findings suggest mechanisms like the "Affleck-Dine mechanism" could create dense objects, such as stars or black holes, made almost entirely of antimatter. These "anti-objects" could have a huge imbalance between matter and antimatter, like a perfectly even split (β = nB / nγ ∼ 1).

If these anti-objects exist, we might spot them through unique signals:

Powerful 100 million electronvolt gamma radiation.
Unusual amounts of antiprotons (particles with the same mass as protons but a negative charge) or positrons (antimatter electrons) in cosmic rays.
A specific 0.511 million electronvolt line from when electrons and positrons annihilate.

"Discovery of cosmic antimatter looks as the unique chance to establish what baryogenesis scenario was realized in the universe."

— Researchers

This means finding antimatter could tell us which cosmic "recipe" for creating the universe was the correct one. The team believes there's a real chance that our galaxy and others could contain these hidden antimatter objects, from "anti-stars" to "anti-black holes with anti-atmospheres."

Challenges in Detection

Detecting this hidden antimatter is incredibly difficult. Any significant antimatter region would likely be so far away it’s at the very edge of our observable universe, due to:

The background of gamma rays.
Problems with "domain walls" (theoretical boundaries between regions of matter and antimatter).

The current limits on how much antimatter exists only hold true if antimatter forms the same kinds of objects as regular matter. Future, more sensitive instruments will be crucial for the search.

The universe could be a cosmic yin and yang, with vast, unseen realms of antimatter waiting to be found.

Dolgov, A.D. (2009). Baryogenesis and Cosmological Antimatter. arXiv:0901.2100v1 [hep-ph].