Grant: Discovery Grants Program - Individual

Nature of the work: This theoretical research will challenge Einstein's General Relativity (GR) at all scales in order to find the true theory of gravity by studying its foundations and identifying non-GR signatures detectable with astronomy. GR is successful in the Solar System but is not tested in the rest of the universe. For a theorist, GR must be changed because: 1) it predicts its own failure at singularities (the Big Bang, the centre of black holes); 2) it is incompatible with quantum mechanics (which is instead extremely well tested and accounts for most of the current technology market); 3) it postulates an ad hoc dark energy undetectable in the lab to fit the cosmological observations. I will relate cosmological deviations from GR with black holes and other local objects, working at three levels: Cosmology - With a new approach that I developed, I will study the largest bound structures in the universe, in which two opposing forces (the disrupting pull of the cosmological expansion and the local attraction of gravity) become comparable, determining the features of the largest bound structures. Black holes - theories of non-GR cosmology predict a scalar ``hair'', a field that surrounds black holes, the effects of which will be studied. Star-like objects - I will investigate how star-like objects connect with their cosmological surroundings in alternative gravity. Importance of the research: Since gravity is one of only four fundamental forces in nature - it shapes space and time, rules the planet, the universe, and everyday life - it deserves to be understood. Detecting deviations from GR would change one of the foundations of physics, while discovering black hole hair would provide new astrophysics. These discoveries would change our fundamental view of the universe, much like Einstein's discovery of relativity did. Anticipated outcomes: The main outcome of our research will be the direct linkage of cosmology with black hole hair and starlike objects with their surroundings. We don't understand this physics because we always separate the two aspects, but their joint exploration may lead to new discoveries. Other outcomes include answers to the questions: how do strong gravity/gravity at large scales look like? Is a thermodynamics of dynamical black holes possible? Do accretion disks orbiting black holes change size, or frequency of the emitted radiation, if gravity is not GR? We will soon test these features and, therefore, gravity, with astronomy. Should our work not be successful, we will still improve our understanding of GR and the systems described by it. Main benefits: The main benefit to science will be the advancement of knowledge in a fundamental area. In the long run, fundamental knowledge always leads to technological and economic benefits (e.g., Maxwell's electromagnetism and your cellphone, quantum mechanics and the computer industry, relativity and the GPS of your airplane landing in fog).