8/23/2023 0 Comments Boinc projects quantum gravity![]() Such a spacetime is a solution to Einstein’s equations with a negative cosmological constant. AdS stands for anti-de Sitter, which is shorthand for a spacetime with constant, negative curvature. The difficult problem of constructing more realistic model universes is a topic of ongoing and active research.Īnother strategy is to generalize the so-called AdS/CFT correspondence, which arguably furnishes our best understanding of quantum gravity to date. It is possible to construct nearly stable universes in this manner, but these constructions possess features that make them unrealistic. One approach is to find an appropriate “string compactification”-a type of architectural map for strings and membranes-which builds up a universe with a positive cosmological constant. ![]() There are many strategies in quantum gravity for constructing an expanding universe. Their findings may offer a new direction for theorists trying to build models of quantum gravity with a positive cosmological constant consistent with our own Universe. Inspired by this framework, Yasuaki Hikida from Kyoto University in Japan and colleagues studied a simplified model of an expanding universe and found that it also has holographic properties. ![]() While quantum gravity models with a negative cosmological constant do not describe our Universe, they do have a surprising feature: the gravity-filled volume of spacetime can be described by a field theory without gravity, often envisioned as a hologram living on a surface. They have had more success with the imagined setting of a negative cosmological constant. A positive cosmological constant is a major challenge for quantum gravity theorists to understand. Our prevailing understanding of cosmology posits that this accelerating expansion is due to empty space possessing an energy, described by a positive cosmological constant. ×Įxperimental discoveries in the late 1990s established that we live in a Universe undergoing accelerating expansion. The calculations of Hikida and colleagues establish that a WZW conformal field theory produces correct answers for cosmological entropies. The surface of the lake can be identified with the Wess-Zumino-Witten (WZW) conformal field theory, which describes gravitational fluctuations that are represented as waves. The bottom of the lake corresponds to earlier times when the universe is smaller, and the top of the lake corresponds to later times when the universe is larger. 106, pp.APS/ Alan Stonebraker Figure 1: Three-dimensional de Sitter space is an expanding universe, which can be imagined as a lake whose width expands from a narrow bottom to a wide top. Kempf, Quantum Uncertainty and the Spectra of Symmetric Operators, Acta Appl. Martin, Information Theory, Spectral geometry and Quantum Gravity, Phys. Kempf, Information-theoretic natural ultraviolet cutoff for spacetime, Physical Review Letters 103, 231301 (2009), arXiv:0908.3061. Kempf, Spacetime could be simultaneously continuous and discrete, in the same way that information can be, New Journal of Physics, 12, 115001 (2010) Read the "Spacetime could be simultaneously continuous and discrete, in the same way that information can be" short paper in Physical Review Letters (PDF), and the latest, longer paper in New Journal of Physics (PDF). Read the "Proposed spacetime structure could provide hints for quantum gravity theory" news item as a PDF file (PDF) or on website. Watch the video of a talk I gave on this topic at the Santa Fe Institute in February 2011, and a short video-abstract on New Journal of Physics. This yields a new connection in between the fields of information theory and quantum gravity, and the emerging methods have the potential to be useful in both fields. I showed that spacetime could be simultaneously continuous and discrete, in the same way that information can. How can general relativity and quantum theory be unified in one theory? Basic idea
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |