Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the universe (see galaxy formation and evolution and structure formation).[4
Chaotic Inflation theory models quantum fluctuations in the rate of inflation. Those regions [bubbles]with a higher rate of inflation expand faster and dominate the universe, despite the natural tendency of inflation to end in other regions. This allows inflation to continue forever, to produce future-eternal inflation.
The bubble universe model proposes that different regions of this inflationary universe (termed a multiverse) decayed to a true vacuum state at different times, with decaying regions corresponding to "sub"- universes not in causal contact with each other and resulting in different physical laws in different regions which are then subject to "selection" which determine each region's components based upon (dependent on) the survivability of the quantum components within that region. The end result will be a finite number of universes with physical laws consistent within each region of spacetime.
From THE ETERNAL UNIVERSE, PAUL STEINHARDT AND NEIL TUROK
page 54-59: The decay of inflationary energy into radiation after inflation is governed by quantum mechanics...very similar to radioactive decay. The random character of the decay, sooner in some parts later in others, results in a patchy universe of the type observed today.
...The relaxation of the inflation field to a zero energy value takes place by a process called bubble nucleation: the inflation drops to its zero energy value at one point in space, and this sparks an outward spreading bubble, one whose walls move at lightspeed...Guth realized that space surrounding the bubbles...would continue to undergo rapid inflationary expansion driving the bubbles apart...[there was] no guarantee that the growing bubbles would...coalesce into a large homogeneous expanse...insights of Linde, Albrecht and Steinhardt...now called new inflation...[found changing the shape of the energy bowl prolonged the inflationary burst so that one single bubble easily grew large enough to encompass the entire observable universe.
...Linde [later] found a way to generate an inflationary burst...without invoking a particularly special potential energy bowl, and without setting up the inflation field in a special configuration, the chaotic environment of the early universe could have naturally gievn rise to inflationay expansion...Not surprisingly, Linde called this approach chaotic inflation. Many physicsts consider it the most convincing realization of the inflationary paradigm...
Bubbles refer to the regions of space where a new phase of matter has formed during a cosmological phase transition. These bubbles are characterized by their different physical properties compared to the surrounding space.
Bubbles form when there is a change in the fundamental properties of the universe, such as temperature or energy density, causing a new phase of matter to appear. This change creates regions of space with different properties, leading to the formation of bubbles.
Cosmological phase transitions occur due to changes in the energy density of the universe, typically caused by the expansion or cooling of the universe. These changes can trigger a transition from one phase of matter to another, resulting in the formation of bubbles.
Bubbles play a crucial role in cosmological phase transitions as they are responsible for the formation of new phases of matter. This leads to the formation of structures such as galaxies and clusters of galaxies, shaping the overall structure of the universe.
Scientists use various methods, such as computer simulations and observational data, to study bubbles in cosmological phase transitions. These methods allow scientists to understand the properties and behavior of bubbles and their impact on the evolution of the universe.