QUANTUMSPACE · Quantum Gravity, Black Hole Entropy and the Emergence of Spacetime.
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2005-11-01 → 2007-10-31
- EU contribution
- €155,644
- Participants
- 1
- Scheme
- EIF
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Results in brief
Final Activity Report Summary - QUANTUMSPACE (Quantum Gravity, Black Hole Entropy and the Emergence of Spacetime)
The project was concerned with the two fundamental questions in theoretical physics, namely quantum gravity and quantum mechanics. In quantum gravity the problem is to reconcile quantum mechanics and general relativity. The project proposed a completely new way to achieve this elusive goal. Instead of quantising the gravitational field the project proposed to find the gravitational field in the emergent physics of a quantum mechanical system that did not have a priori any gravitational degrees of freedom. In the course of the project we showed that this could indeed be achieved if one focused on an internal perspective. We showed that not only did special relativity arise in this way but also that Newtonian gravity emerged in the appropriate low velocity limit. We also gave a new formula for the gravitational mass of a large bound object. This view of gravity opened new avenues of research. One possible application was cosmology. We currently think that the universe underwent a period of exponential growth in its early history. The point of view explored here might enable us to replace this period of expansion with a phase transition instead. In quantum mechanics, the question is how quantum mechanics and classical mechanics are related. How do we go from the quantum mechanical superposition principle to classical certainty? To solve this problem we proposed a new view of classical objects as large quantum mechanical systems. This removed the artificial split between the quantum world and the classical world that was introduced by the so called Copenhagen interpretation. It also allowed for the exploitation of special properties that only large systems have. One of these properties was the so called generalised rigidity. This was the presence of a property that requires a force to change it. We argued that it was these properties that we should identify as classical properties. A consequence of this identification was the natural presence of probability. The probability in quantum mechanics was thus not fundamental in our approach. It had the same origin that probability had in all other branches of physics, namely our lack of knowledge of the system.
Data: CORDIS, © European Union
Project objective
The objective of the proposal is to make progress in the problem of quantum gravity. Quantum gravity is the name of the theory that combines quantum theory with general relativity. Although there are several candidates for such a theory none of them can claim to be completely satisfactory. The problem of finding such a theory can be tackled in two different ways. First there is the top down approach. Here one tries to use known theories to infer as much as possible about the as yet unknown theory. Then there is the bottom-up approach. Here one tries to build the theory from first principles. It is the aim of this proposal to make progress using both approaches. The top down approach will be followed by looking closer at the problem of black hole entropy. Recently progress in this direction has been made using the ringing modes of a black hole. A characteristic frequency of the ringing modes spectrum could be used to fix a parameter in loop quantum gravity, one of the candidates for a theory of quantum gravity. With this value of the parameter the entropy of a black hole calculated in loop quantum gravity coincides exactly with the Bekenstein Hawking value of one quarter of the horizon area. This surprising connection opens up a whole set of new questions. The underlying mechanism of this connection is unclear. What is the status for rotating black holes? It is the aim of this proposal to make progress on this type of questions. For this it will be necessary to better understand classical black holes in loop quantum gravity. Here contact is made to the bottom up approach. The understanding of classical black holes in quantum gravity requires the solution of the so-called problem of time. The other aim of the proposal is to understand this problem better. One-way of doing this is to have a closer look at simple system from solid states physics. If looked at in an appropriate way, these systems can be fruitful test beds for ideas on how to proceed.
Original text from CORDIS.
Participants
- IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE · LONDONCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union