Final Report Summary - CGR2011TPS (Challenging General Relativity)
The main aim of this research programme has been to explore the limitations of General Relativity as a theory for the gravitational interaction. The motivation comes from the fact that our poor understanding of gravitation in certain regimes appears to be intimately related to some of the most important open questions in theoretical physics, cosmology and astrophysics. 3 distinct research direction were pursued.
Quantum Gravity and Phenomenology: Local Lorentz symmetry - the cornerstone of Einstein’s Special Relativity that dictates that nothing travels faster than light in vacuum - appears to be a fundamental symmetry of the standard model of particle physics. Significant progress was made in exploring the role of Lorentz symmetry (or absence thereof) in gravity and the implications this might have for quantum gravity - the description of the gravitational interaction when quantum effects are important. In particular, specific quantum gravity candidates were proposed, analysed, and confronted with observations. Our research also provided new insights in the relations between Lorentz symmetry and approaches to quantum gravity that involve discrete (as opposed to continuous) spaces.
Alternative theories of gravity: Several alternative theories of gravitation have been analysed and confronted with observations using newly developed techniques. Some of them were new and others are well-studied and of particular interest to the research community. The links between these theories and quantum gravity candidates have also been explored. The study of such theories has allowed us to quantify how much we are allowed to depart from General Relativity without contradicting observations. It has also allowed us to significantly deepen our theoretical understanding of gravitation.
Strong gravity: Crucial steps were made in understanding the structure of black holes and very compact stars beyond General Relativity. The results range from mathematical theorems to numerical modelling and many of them are groundbreaking, such as finding new types of black holes or demonstrating that that fundamental physics in the interior of very compact stars could be very different of what we observe in Earth based accelerators.
The ultimate objective of the program has been to combine research from all 3 aforementioned directions to advance our understanding of gravitation. Indeed, the two major achievements in this respects have been: (i) to concretely demonstrate that alternative theories of gravity can indeed provide a crucial link between quantum gravity and experiments and observations and be used to instruct quantum gravity model building; (ii) to have a leading role in establishing the foundations of using the structure of black holes and compact stars in testing gravity theories with astronomical observations. Both ideas were particularly novel when the program was proposed but they had become mainstream by now. In the dawn of gravitational wave astronomy, this is a particularly timely contribution.
During the programme, the members of the research group have published 54 journal papers and several conference proceedings, have delivered approximately 100 seminars and presentations, have organised 10 conferences and workshops, and have hosted 48 research visitors from all 5 continents. 4 researchers have received ther PhD while conducting research in the group and 2 more members of the group are expected to do so after the programme is completed.
Quantum Gravity and Phenomenology: Local Lorentz symmetry - the cornerstone of Einstein’s Special Relativity that dictates that nothing travels faster than light in vacuum - appears to be a fundamental symmetry of the standard model of particle physics. Significant progress was made in exploring the role of Lorentz symmetry (or absence thereof) in gravity and the implications this might have for quantum gravity - the description of the gravitational interaction when quantum effects are important. In particular, specific quantum gravity candidates were proposed, analysed, and confronted with observations. Our research also provided new insights in the relations between Lorentz symmetry and approaches to quantum gravity that involve discrete (as opposed to continuous) spaces.
Alternative theories of gravity: Several alternative theories of gravitation have been analysed and confronted with observations using newly developed techniques. Some of them were new and others are well-studied and of particular interest to the research community. The links between these theories and quantum gravity candidates have also been explored. The study of such theories has allowed us to quantify how much we are allowed to depart from General Relativity without contradicting observations. It has also allowed us to significantly deepen our theoretical understanding of gravitation.
Strong gravity: Crucial steps were made in understanding the structure of black holes and very compact stars beyond General Relativity. The results range from mathematical theorems to numerical modelling and many of them are groundbreaking, such as finding new types of black holes or demonstrating that that fundamental physics in the interior of very compact stars could be very different of what we observe in Earth based accelerators.
The ultimate objective of the program has been to combine research from all 3 aforementioned directions to advance our understanding of gravitation. Indeed, the two major achievements in this respects have been: (i) to concretely demonstrate that alternative theories of gravity can indeed provide a crucial link between quantum gravity and experiments and observations and be used to instruct quantum gravity model building; (ii) to have a leading role in establishing the foundations of using the structure of black holes and compact stars in testing gravity theories with astronomical observations. Both ideas were particularly novel when the program was proposed but they had become mainstream by now. In the dawn of gravitational wave astronomy, this is a particularly timely contribution.
During the programme, the members of the research group have published 54 journal papers and several conference proceedings, have delivered approximately 100 seminars and presentations, have organised 10 conferences and workshops, and have hosted 48 research visitors from all 5 continents. 4 researchers have received ther PhD while conducting research in the group and 2 more members of the group are expected to do so after the programme is completed.