Dark Bubble Cosmology Predicts Weak Gravity at Micron Scales and Enables Inflation Without New Physics

The fundamental nature of gravity at extremely small scales remains an open question, and new theoretical work now predicts surprising behaviour at micron distances. Ulf Danielsson and Suvendu Giri, both from Uppsala Universitet, investigate the implications of a ‘dark bubble’ cosmology, a model which elegantly explains the cosmological constant and makes testable predictions for gravitational forces. Contrary to many theories involving extra dimensions, this research demonstrates that gravity actually weakens at these tiny scales, a result that could be verified using tabletop experiments. This weakening also has profound cosmological consequences, potentially resolving the long-standing puzzle of early inflation and offering an explanation for the observed curvature of the universe, addressing the ‘why-now’ problem of the cosmological constant.

The study provides explicit predictions for measurable deviations using tabletop experiments. Furthermore, the same effect reduces the effective force of gravity at high energy densities in the early universe, naturally leading to a period of early inflation without needing additional theoretical assumptions. The work also proposes a quantum origin for the universe, suggesting a five-dimensional black hole acted as a catalyst for the nucleation of the dark bubble, and explains how this process accounts for the present matter content in the universe.

Dark Bubble Cosmology Addresses Constant Problem

This research explores dark bubble cosmology, a cosmological model proposing our universe originated as a bubble forming within a higher-dimensional Anti-de Sitter (AdS) space. A primary motivation is to address the cosmological constant problem, the significant discrepancy between the theoretically predicted vacuum energy and the observed dark energy density. The dark bubble model attempts to dynamically adjust the cosmological constant to its observed, small value.

Rooted in string theory, the model aims to provide a consistent framework for cosmology that incorporates quantum gravity effects. The universe doesn’t originate from nothing, but rather emerges from the decay of the AdS space, with the bubble nucleation triggering expansion. Key findings reveal that inflation, a period of rapid expansion in the early universe, arises automatically as a consequence of the bubble nucleation and its subsequent evolution, eliminating the need for fine-tuning of parameters. The model also predicts a scale-invariant spectrum of primordial fluctuations, consistent with observations of the Cosmic Microwave Background. This dynamic relaxation of the cosmological constant is achieved through the decay of the AdS space and the formation of the bubble.

The model predicts a specific amount of radiation in the present universe, consistent with observations. The nucleation of the bubble is catalyzed by an initial five-dimensional black hole, with its entropy related to the initial conditions of the universe. The model also suggests that black holes can be mimicked by AdS black shells, which could have observable electromagnetic and gravitational signatures. This offers an alternative to the standard Lambda-CDM model of cosmology, providing a concrete example of how string theory can construct a viable cosmological model and potentially explain the origin of dark energy. The model makes several testable predictions, such as the scale-invariant spectrum of primordial fluctuations and the existence of black hole mimickers, establishing a connection between black holes and the origin of the universe.

Future research will focus on a more detailed study of the inflationary mechanisms predicted by the model, investigating the observational signatures of black hole mimickers, refining the model by incorporating more realistic physics, and testing the model’s predictions against observational data. Further research is also needed to understand the initial conditions that led to the formation of the initial five-dimensional black hole, and to explore the deeper connection between the model and the fundamental principles of quantum gravity. In essence, this research presents a sophisticated cosmological model rooted in string theory that attempts to address some of the most challenging problems in modern cosmology, such as the cosmological constant problem and the origin of inflation.

Dark Bubble Model Predicts Weakened Gravity

This research explores the dark bubble model, a cosmological framework proposing our universe exists as a bubble within a higher-dimensional space. A key achievement is the prediction that gravity weakens at small scales, deviating from the standard Newtonian inverse square law, and at high energy densities, potentially driving a period of early inflation without requiring additional theoretical components. The team calculated the resulting gravitational potential, demonstrating a qualitative shift in gravitational force at specific distances, and establishing a connection between the model’s parameters and the observed cosmological constant.

This investigation builds upon previous work by refining calculations of the backreaction of matter on the dark bubble and resolving ambiguities in the resulting gravitational potential. The findings suggest the possibility of experimentally verifying the model’s predictions using tabletop experiments, as the predicted scale of gravitational modification falls within the range of current experimental sensitivity.