A variant of the theory of quantum gravity – unification Quantum Mechanics and Einstein’s General relativity – could help solve one of the biggest puzzles in cosmology, new research suggests.
For nearly a century, scientists have known that the universe is expanding. But in recent decades, physicists have discovered that different types of measurements of the expansion rate — known as the Hubble parameter — have produced puzzling discrepancies.
To resolve this paradox, a new study suggests incorporating quantum effects into a core theory used to determine the rate of expansion.
„We tried to resolve and explain the mismatch between the values of the Hubble parameter from two different main types of observations,” study co-author PK Sureshprofessor of physics at the University of Hyderabad in India, told Live Science via email.
An expanding problem
The expansion of the universe was first discovered by Edwin Hubble in 1929. His observations with the largest telescope of the time revealed that galaxies far away from us appear to be moving at a faster rate. Although Hubble initially overestimated the expansion rate, subsequent measurements refined our understanding and established the current Hubble parameter as more reliable.
In the late 20th century, astrophysicists introduced a new technique to measure the expansion rate by examining the cosmic microwave background. big bang.
however, A serious problem arose With these two types of measurements. In particular, the new method produced a Hubble parameter value nearly 10% lower than that obtained from astronomical observations of distant cosmic objects. Such discrepancies between different scales, known as the Hubble tension, indicate potential flaws in our understanding of the evolution of the universe.
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In a study published in the journal Classical and quantum gravity, Suresh and his colleague from University of Hyderabad P. Anupama proposed a solution to reconcile these divergent results. They underlined that physicists implicitly infer the Hubble parameter by using a model of the evolution of our universe based on Einstein’s theory of general relativity.
The team advocated revising this theory to incorporate quantum effects. These effects, inherent to fundamental interactions, include random field fluctuations and the spontaneous generation of particles from the vacuum of space.
Despite scientists’ ability to integrate quantum effects with theories from other fields, quantum gravity remains elusive, making detailed calculations very difficult or impossible. To make matters worse, experimental studies of these effects require reaching much higher temperatures or energies than can be achieved in a laboratory.
Acknowledging these challenges, Suresh and Anupama focused on broader quantum-gravitational effects common to many proposed theories.
„Our equation doesn’t necessarily account for everything, but that doesn’t stop us from testing quantum gravity or its effects experimentally,” Suresh said.
Their theoretical study revealed that accounting for quantum effects when describing gravitational interactions during the early stages of the universe’s expansion, known as cosmic inflation, could actually change the current theory’s predictions about the properties of the microwave background. Measurements are consistent.
Of course, final conclusions can only be drawn once a complete theory of quantum gravity is known, but even the initial findings are encouraging. Furthermore, the link between the cosmic microwave background and quantum gravitational effects opens the way to experimentally study these effects in the future, the team said.
„Quantum gravity must play a role in the dynamics of the early universe; so its effect can be seen through measurements of the properties of the cosmic microwave background,” said Suresh.
„Some future work devoted to studying this electromagnetic background is very feasible and promising for testing quantum gravity. … It offers a promising proposition for solving and validating inflationary models of cosmology in conjunction with quantum gravity.”
Additionally, the authors hypothesize that quantum gravitational events in the early universe may have shaped the properties of gravitational waves emitted during that period. Detection of these waves by future gravitational-wave observatories may shed further light on the properties of quantum gravity.
„Gravitational waves have only been observed so far from various astrophysical sources, but gravitational waves from the early universe have yet to be detected,” Suresh said. „We hope our work will help identify the correct inflation model and detect primordial gravitational waves with features of quantum gravity.”
„Oddany rozwiązywacz problemów. Przyjazny hipsterom praktykant bekonu. Miłośnik kawy. Nieuleczalny introwertyk. Student.