Wednesday, December 4, 2024

Dark matter formation may have occurred before the Big Bang




Physicists continue to grapple with the mystery of dark matter, the elusive substance that makes up approximately 80% of the matter in the universe but has defied detection.

Now, a team of researchers has proposed an innovative model suggesting that dark matter might have originated before the Big Bang, during an inflationary phase when the universe underwent rapid exponential expansion.

The role of inflation and dark matter formation

Inflation, a concept developed about 45 years ago, describes a brief period in the early universe when its size expanded exponentially by a factor of about about 1026 in 10-36 seconds.

This rapid expansion, theorized to have occurred before the conventional Big Bang, provides explanations for several cosmological puzzles, including the flatness and homogeneity of the universe and the origins of its structure.

Despite being widely accepted among cosmologists, the mechanism driving inflation remains unknown. It is attributed to a hypothetical field called the inflaton, which spans all of spacetime.

During inflation, the universe exists in a state of supercooled expansion, with temperatures dropping drastically. When inflation ends, a process called reheating occurs, restoring the universe to pre-inflation temperatures and initiating the production of standard particles, including photons.

Traditional theories of dark matter formation

Existing theories propose that dark matter emerges through interactions with a thermal bath of particles, with its abundance determined by either a “freeze-out” or “freeze-in” mechanism.

In the freeze-out model, dark matter remains in equilibrium with the thermal bath during the earliest moments, while in the freeze-in model, dark matter never reaches equilibrium due to suppressed interactions.

In ultraviolet (UV) freeze-in, for instance, the temperature of the thermal bath is always lower than the masses of the particles connecting dark matter to the Standard Model of particle physics.

This scenario relies on quantum field interactions, where dark matter is produced under specific energy conditions.

A novel mechanism: Dark matter during inflation

The new model, dubbed WIFI (Warm Inflation via ultraviolet Freeze-In), introduces an alternative perspective. It posits that dark matter was created during the inflationary phase through rare interactions in a hot, energetic environment.

Unlike traditional models, which assume anything produced during inflation is diluted away by the universe’s rapid expansion, the WIFI model suggests that dark matter formed during this period could survive and account for the dark matter observed today.

“The thing that’s unique to our model is that dark matter is successfully produced during inflation,” explained Katherine Freese, lead author and director of the Weinberg Institute for Theoretical Physics at The University of Texas at Austin.

“In most other models, anything that is created during inflation is then ‘inflated away’ by the exponential expansion of the universe, to the point where there is essentially nothing left.”

In this scenario, the inflaton field driving inflation loses some of its energy to radiation, which then produces dark matter particles through the freeze-in mechanism.

Beyond the Big Bang singularity

This model aligns with the idea that inflation predates the Big Bang, challenging the notion of a singularity with infinite density and curvature. Instead, the universe is thought to have had a small but finite size post-inflation, approximately 10-26 meters in diameter.

From there, the standard processes of radiation and particle production unfolded, leading to the universe as we know it.

Future validation and implications

The WIFI model is not yet confirmed by observations, but it could be tested within the next decade through experiments studying the cosmic microwave background (CMB).

Warm inflation, a key component of the WIFI model, will be a focus of these studies. If warm inflation is verified, it would bolster the model’s credibility and open avenues for understanding other particles and processes in the early universe.

“In our study, we focused on the production of dark matter, but WIFI suggests a broader applicability, such as the production of other particles that could play a crucial role in the early universe’s evolution,” said co-author Barmak Shams Es Haghi. “This highlights new opportunities for exploration in future research.”

A new chapter in dark matter research

While the origins of dark matter remain an enigma, the WIFI model offers an exciting framework that ties its formation to one of the universe’s earliest and most dramatic phases.

By exploring this unconventional path, researchers hope to uncover not only the nature of dark matter but also new insights into the universe’s infancy and evolution.

Website: International Research Awards on High Energy Physics and Computational Science.

#HighEnergyPhysics#ParticlePhysics#QuantumPhysics#AstroparticlePhysics#ColliderPhysics#HiggsBoson#LHC#QuantumFieldTheory#NeutrinoPhysics#PhysicsResearch#ComputationalScience#DataScience#ScientificComputing#NumericalMethods#HighPerformanceComputing#MachineLearningInScience#BigData#AlgorithmDevelopment#SimulationScience#ParallelComputing
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