Scientists from Spain and Italy have proposed a model that replaces cosmic inflation with gravitational waves as the key force in the universe's early formation. Published in Physical Review Research, the study suggests gravity and quantum mechanics alone can explain the cosmos's structure. This approach draws on a century-old concept linked to Albert Einstein's work.
A new study challenges traditional views of the universe's birth by proposing that gravitational waves, rather than cosmic inflation, drove its early expansion and structure formation. Researchers Daniele Bertacca, Raul Jimenez, Sabino Matarrese, and Angelo Ricciardone from institutions in Spain and Italy developed this model through advanced computer simulations. Published in Physical Review Research in 2025 (volume 7, issue 3), the paper titled "Inflation without an inflaton" argues for a simpler explanation rooted in general relativity and quantum mechanics.
The traditional inflation theory posits that the universe expanded rapidly in a fraction of a second after the Big Bang, relying on unobserved variables. In contrast, the new model invokes De Sitter space—a mathematical construct from the 1920s collaboration between Dutch mathematician Willem de Sitter and Albert Einstein—to show how gravitational waves could generate the seeds for galaxies, stars, and planets.
"For decades, we have tried to understand the early moments of the Universe using models based on elements we have never observed," said Dr. Raúl Jiménez, a co-author from ICREA in Spain. "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."
Gravitational waves, ripples in space-time predicted by Einstein in 1916, were first conceptualized by Oliver Heaviside and Henri Poincaré in 1893 and 1905. Their faint signals from events like merging black holes were finally detected in September 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington and Louisiana. While the Big Bang remains the dominant framework, this study revives overlooked ideas to address lingering questions about the universe's origins without introducing untested components.