A model explaining the microscopic origin of black hole entropy
A black hole is a fascinating celestial object whose gravitational pull is so strong that no object or even light can escape from it. Although black holes have been the subject of numerous astrophysical studies, their origins and underlying physics remain largely a mystery. Researchers from the University of Pennsylvania and Centro Atomico Bariloche recently published a new model of black hole microstates that investigates the origin of entropy (and thus the degree of disorder) in black holes. The model, presented in a paper published in Physical Review Letters, provides another perspective on black holes that could inform future astrophysical research. “The Bekenstein-Hawking entropy formula, which describes the thermodynamics of black holes, was discovered in the 1970s,” study co-author Vijay Balasubramanian told Phys.org. “This formula suggests that a black hole has an entropy proportional to the area of its horizon. “According to statistical physics developed by Boltzmann and Gibbs in the late 19th century, the entropy of a system is related to the number of microscopic configurations with the same macroscopic description. “In a quantum mechanical world like ours, entropy arises from ‘microstates’, that is, quantum superpositions of microscopic components that provide the same observable properties on large scales.” Physicists have been trying for decades to provide a reliable explanation of black hole entropy. In the 1990s, Andrew Strominger and Kamran Vafa developed a way to count the microstates of a special class of black holes whose mass is equal to the electromagnetic charge in a universe with additional dimensions and multiple species, exploiting a hypothetical property called “supersymmetry.” The relationship between the electric and magnetic fields of a black hole.
To explain the origin of black hole entropy in a universe like ours, Balasubramanian and his colleagues needed to create a new theoretical framework. “Despite previous attempts, there are no reports yet that apply to the type of black holes formed by collapsing stars on our world,” Balasubramanian said. “Our goal was to provide such an account.” The main contribution of this recent work is the introduction of a new model of the black hole microstate, which can be described as a dust shell collapsing inside the black hole. The researchers also developed a technique to count the likelihood of quantum mechanical superposition of these tiny states. “A key finding of our research is that the very different space-time geometries that appear to correspond to different microstates are caused by the subtle effects of quantum mechanical ‘wormholes’ that connect distant regions of space. That means they can mix with each other,” Balasubramanian said. “After considering the effects of these wormholes, we found that in a universe with gravity and matter, the entropy of a black hole is directly proportional to the area of its event horizon, as suggested by Bekenstein and Hawking. .” Recent work by Balasubramanian and his colleagues introduces a new way of thinking about black hole microstates. She specifically describes her own model as a quantum superposition of simple objects that can be well explained by classical physical theories of matter and space-time geometry. “This is very surprising because the community expected that to explain the entropy of black holes microscopically, we would need the entire apparatus of quantum gravity theory, such as string theory.” Balasubramanian said. “We also showed that universes that are different from each other at the macroscopic or even cosmic level can sometimes be understood as quantum superpositions of other macroscopically different universes. This is based on quantum mechanics at the level of the entire universe. This is surprising because we often associate quantum mechanics with small-scale phenomena.” The newly introduced theoretical framework could pave the way for further theoretical studies aimed at explaining the thermodynamics of black holes. In the meantime, the researchers plan to expand and enrich their description of black holes’ microstates. “We are currently investigating to what extent and under what conditions observers outside the event horizon can determine which microstate a black hole is in.” Balasubramanian added.
source: Physical Review Letters https://dx.doi.org/10.1103/PhysRevLett.132.141501