I can provide information on some notable multiverse theories that have been proposed by physicists and cosmologists.
Many-Worlds Interpretation: Proposed by physicist Hugh Everett, the Many-Worlds Interpretation suggests that every possible outcome of a quantum event is realized in a separate universe. In this theory, the universe splits into multiple branches with every quantum interaction, resulting in an infinite number of parallel universes.
Bubble Universes (Eternal Inflation): According to this theory, our universe is just one of many bubble-like universes that exist within a larger multiverse. In the process of cosmic inflation, new universes continually bud off, each with its own physical properties and laws of physics.
Brane Multiverse: This theory is based on string theory and suggests that our universe is a three-dimensional "brane" floating within a higher-dimensional space called the "bulk." Other branes could exist parallel to ours, each representing a separate universe with its own laws of physics.
Mathematical Universe Hypothesis: Proposed by physicist Max Tegmark, this hypothesis suggests that all possible mathematical structures exist as separate universes. According to this view, our physical reality is just one of many mathematical structures, each describing a different universe with its unique set of physical laws.
Quantum Multiverse: This theory suggests that every quantum event leads to the creation of multiple universes, branching out from each possible outcome. It combines the ideas of quantum mechanics and the multiverse, proposing that every conceivable outcome of a quantum event actually occurs in a separate universe.
Each of these multiverse theories has its own unique features and implications, and they vary in terms of their level of acceptance and supporting evidence within the scientific community. The choice of a "favorite" theory often depends on an individual's perspective, philosophical leanings, and interpretation of the available evidence.