There are several hypothetical universes that have been proposed within the realm of current theories about the observable universe. While these universes have not been observed or confirmed, they are considered possibilities based on theoretical frameworks. Here are a few examples:
Inflationary Multiverse: According to the theory of cosmic inflation, the universe underwent a rapid expansion in its early stages. This theory suggests that this expansion might have caused the formation of "bubble" universes within a larger multiverse. Each bubble universe could have its own set of physical laws and constants, leading to a vast ensemble of parallel universes.
String Theory Landscape: String theory is a framework that seeks to unify quantum mechanics and general relativity. Within string theory, there exists the concept of a "landscape" that comprises a vast number of possible solutions or configurations. Each solution corresponds to a different universe with its own physical laws and properties. This landscape potentially allows for a multitude of universes, each with distinct characteristics.
Brane Cosmology: Brane cosmology, derived from string theory, suggests that our universe is a three-dimensional "brane" embedded within a higher-dimensional "bulk." In this scenario, multiple branes could exist, each representing a separate universe with its own unique properties. These universes might be separated by vast distances in the extra dimensions.
Simulated Universes: The concept of simulated universes suggests that our reality is a computer-generated simulation. According to this idea, an advanced civilization could create and run simulations that are indistinguishable from a genuine universe. If this were the case, it would imply the existence of countless simulated universes, each with its own rules and characteristics.
It's important to note that these ideas are still speculative and are part of ongoing scientific research and investigation. While they provide intriguing possibilities, their existence and validity require further evidence and testing.