Tiberiu Harko is Senior Honorary Research Associate in the Department of Mathematics at University College London, visiting Professor in the Department of Physics at the Sun-Yat Sen University in Guangzhou, China, and Associate Professor in the Babes-Bolyai University, Cluj, Romania. His research interests include general relativity and modified theories of gravity, cosmology, astrophysics and applied mathematics. Francisco S. N. Lobo is Principal Investigator at the Science Faculty of the Universidade de Lisboa, and leads the Cosmology Group at the Institute of Astrophysics and Space Sciences. His research is focused on gravitational physics, and several of his publications have received extensive news coverage from publications including The New York Times, Scientific American and National Geographic.
'A very nice introduction to gravity theories and how on emight extend then in progressively more complicated ways. It is a well-written book, which provides the motivation for modified gravity theories, as well as a very clear formal development of the theories.' Alan Heavens, The Observatory