Scale-Invariant Unparticles and Cosmic Expansion
Science Time · 2024
"The accelerating expansion of the universe, traditionally attributed to the Cosmological Constant, may be driven by "unparticles" — a theoretical form of scale-invariant matter that behaves as a macroscopic fluid defying standard particle physics."
In the late 1990s astronomers discovered the universe isn't just expanding but accelerating. The driver is placeholder-named "Dark Energy," roughly 68% of the observable universe, standardly explained by the Cosmological Constant — an inherent energy of empty space. But that model faces severe mathematical tension: quantum mechanics predicts vacuum energy vastly larger than what's actually observed. An alternative: a bizarre, undiscovered state of matter called "unparticles" might be the real engine pushing galaxies apart.
Proposed by theoretical physicist Howard Georgi in 2007, unparticles defy the Standard Model through "scale invariance" — unlike electrons or photons, they have no distinct measurable mass, behaving identically regardless of the energy scale or distance observed, similar to a fractal pattern. Macroscopically they'd behave not like discrete particles but a continuous, relativistic fluid permeating the cosmos. If this fluid interacts with gravity, it generates a repulsive force that matches the observed accelerated expansion — resolving the mathematical tension of the cosmological constant.
What defines the 'scale invariance' of a hypothetical unparticle?
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- Unparticles and Scale Invariance in CosmologyHouse overview (unparticle physics)
Cosmological Cannibalism and Baby Universes
"The rapid expansion of the universe — traditionally explained by cosmic inflation and dark energy — can alternatively be modeled as our universe systematically colliding with and absorbing smaller "baby universes" within a larger multiverse framework."