Open universe theory
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Open Universe Theory: A Comprehensive Overview
Introduction to Open Universe Theory
The concept of an open universe is a significant topic in cosmology, referring to a universe with a density parameter ((\Omega)) less than one. This implies that the universe will expand forever, never reaching a state of collapse. The open universe theory contrasts with the closed universe theory, where (\Omega) is greater than one, leading to eventual collapse, and the flat universe theory, where (\Omega) equals one, resulting in a balanced expansion.
Geometrical Structure and Observational Evidence
The determination of the universe's geometrical structure through the magnitude-vs-redshift relation has been challenging due to its insensitivity to the deceleration parameter, which determines spatial curvature. By relaxing the assumption of identical gravitational and atomic clocks, sufficient sensitivity can be achieved to determine this parameter. Current observational evidence suggests that the universe is open1.
Quantum Cosmology and Open Universes
Quantum cosmology provides a framework for understanding the creation and evolution of the universe. In the context of open universes, the Wheeler-DeWitt equation's superpotential is significantly modified, leading to different qualitative behaviors of the wavefunction compared to closed universes. Quantum cosmology favors an open universe ((k=-1)), predicting sufficient inflation, which is an improvement over classical measures2.
Density Parameter and the Anthropic Principle
The density parameter ((\Omega)) is crucial in determining the universe's fate. Cosmologists generally believe that the universe is open, with (\Omega) in the range of 0.1 to 0.5. Some theories suggest that (\Omega) should be close to unity to allow the development of stars and life, aligning with the anthropic principle. However, a proposed physical process near the initial cosmic singularity naturally leads to an open universe3.
Classical and Quantum Models in Open FRW Universes
In the framework of nonlinear massive gravity theory, classical and quantum cosmological models in an open Friedmann-Robertson-Walker (FRW) space background have been studied. The theory allows physical solutions for open FRW models, where the mass term acts as a cosmological constant. Quantum effects can replace classically forbidden regions with a bouncing period, connecting contracting and expanding phases4.
Self-Acceleration and Nonlinear Massive Gravity
Nonlinear massive gravity with Lorentz-invariant mass terms supports open FRW universes driven by arbitrary matter sources. While flat FRW solutions are absent, open FRW universes are governed by the Friedmann equation with an effective cosmological constant. This theory exhibits a discontinuity at the flat FRW limit, highlighting the unique nature of open universes5.
Big-Bang Nucleosynthesis and Weak Interactions
Big-bang nucleosynthesis alone cannot determine if the universe is open. However, current gauge theories of elementary particles favor low universal lepton numbers, suggesting an open universe. These values, compatible with nucleosynthesis, support the idea of an open universe with (\Omega < 0.2)7.
Long-Term Evolution in an Open Universe
An open universe does not necessarily evolve into a state of permanent quiescence. Quantitative estimates indicate that normal physical processes, biological adaptation to low temperatures, and interstellar communication can continue indefinitely, utilizing a finite store of energy8.
Quantum Creation and Inflationary Models
The quantum creation of an open universe can be described using different wave functions. The Hartle-Hawking wave function leads to a universe with a very low (\Omega), resulting in a practically structureless universe. In contrast, the tunneling wave function suggests that most inflationary models should have (\Omega = 1), although some models allow (\Omega) to vary widely9.
Conclusion
The open universe theory is supported by various lines of evidence from both classical and quantum cosmology. Observational data, quantum cosmological models, and theoretical considerations all point towards an open universe with a density parameter less than one. This theory has profound implications for the long-term evolution of the universe, suggesting that it will continue to expand indefinitely, with ongoing physical and biological processes.
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Most relevant research papers on this topic
Case for an open universe
The universe is open, as the determination of the deceleration parameter q-bar/sub 0/ can be achieved by relaxing the assumption of gravitational and atomic clocks.
Quantum cosmology and open universes
Quantum cosmology favors open universes with k=-1, and sufficient inflation is predicted, improving our understanding of inflation in classical measures.
Classical and quantum massive cosmology for the open FRW universe
The nonlinear massive gravity theory allows for two distinct branches of classical solutions, with quantum effects potentially avoiding classical singularities and allowing for a bouncing period between contraction and expansion eras.
Open FRW universes and self-acceleration from nonlinear massive gravity
Open Friedmann-Robertson-Walker universes can exist with a sufficiently small curvature constant, but there is no exact flat FRW solution, resulting in a discontinuity at the flat FRW limit.
Highly CitedThe case for an open Universe
There is no convincing evidence to support a closed universe, and cosmologists should keep an open mind until empirical data settles the issue.
Weak interactions in the early Universe: is the Universe open?
The universe is open, as low values of universal lepton numbers suggest an open universe, but the Big Bang nucleosynthesis compatibility issue remains unresolved.
Time without end: Physics and biology in an open universe
An open universe can support life and communication for ever, using a finite energy store, if assumed scaling laws are valid.
Highly CitedQuantum creation of an open inflationary universe
The tunneling wave function better describes the probability of universe creation, leading to a universe with Omega = 1, which aligns with the standard expectation that inflation makes the universe flat.
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