By University of Barcelona July 26, 2025
Collected at: https://scitechdaily.com/rewriting-physics-textbooks-scientists-propose-a-bold-new-theory-about-the-universes-origins/
Speculative elements may not be necessary to explain the cosmos.
A team of researchers, led by Raúl Jiménez, an ICREA scientist at the University of Barcelona’s Institute of Cosmos Sciences (ICCUB), and working in partnership with the University of Padua (Italy), has introduced a groundbreaking new theory about how the Universe began.
Published in Physical Review Research, their study offers a major shift in how scientists understand the earliest moments following the Big Bang. Unlike many traditional models, this new approach avoids relying on speculative or unproven assumptions.
Unravelling the mystery of the origins of the Universe
For many years, the dominant explanation in cosmology has been the inflationary model, which proposes that the Universe experienced an extremely rapid expansion in a tiny fraction of a second. While this theory helps explain many features of the cosmos, it depends on several adjustable factors, known as free parameters. Because these variables can be fine-tuned, it becomes difficult to determine whether the model genuinely predicts cosmic behavior or simply fits existing observations.
In a significant breakthrough, the team has proposed a model in which the early Universe does not require any of these arbitrary parameters. Instead, it begins with a well-established cosmic state called De Sitter space, which is consistent with current observations of dark energy.
Gravitational waves: the key to understanding cosmic structure
The new model does not rely on hypothetical fields or particles such as inflation. It suggests that natural quantum fluctuations in space-time, gravitational waves, were sufficient to seed the small density differences that eventually gave rise to galaxies, stars, and planets. These ripples evolve non-linearly, interacting and generating complexity over time, allowing for verifiable predictions with real data.
“For decades, we have tried to understand the early moments of the Universe using models based on elements we have never observed,” says Raúl Jiménez. “What makes this proposal exciting is its simplicity and verifiability. We are not adding speculative elements, but rather demonstrating that gravity and quantum mechanics may be sufficient to explain how the structure of the cosmos came into being.”
Understanding the origin of the Universe is not just a philosophical question; it helps us answer fundamental questions about who we are and where we come from. This new proposal offers a minimalist but powerful, elegant, and potentially refutable vision. This is science at its best: clear predictions that future observations—such as measurements of gravitational waves and cosmic structure—can confirm or reject.
These new results suggest that we may not need speculative elements to explain the cosmos, but only a deep understanding of gravity and quantum physics. If the model is confirmed, it could mark a new chapter in the way we think about the birth of the Universe.
Reference: “Inflation without an inflaton” by Daniele Bertacca, Raul Jimenez, Sabino Matarrese and Angelo Ricciardone, 8 July 2025, Physical Review Research.
DOI: 10.1103/vfny-pgc2
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