Lectures On General Relativity And Cosmology Basic Course

These lecture notes are intended for starting PhD students in theoretical physics who have a working knowledge of General Relativity. The four topics covered are: Surface charges as conserved quantities in theories of gravity; Classical and holographic features of three-dimensional Einstein gravity; Asymptotically flat spacetimes in four dimensions: BMS group and memory effects; The Kerr black hole: properties at extremality and quasi-normal mode ringing. Each topic starts with historical foundations and points to a few modern research directions.

Unlike most traditional introductory textbooks on relativity and cosmology that answer questions like “Does accelerated expansion pull our bodies apart?”, “Does the presence of dark matter affect the classical tests of general relativity?” in a qualitative manner, the present text is intended as a foundation, enabling students to read and understand the textbooks and many of the scientific papers on the subject. And, above all, the readers are taught and encouraged to do their own calculations, check the numbers and answer the above and other questions regarding the most exciting discoveries and theoretical developments in general relativistic cosmology, which have occurred since the early 1980s. In comparison to these intellectual benefits the text is short. In fact, its brevity without neglect of scope or mathematical accessibility of key points is rather unique. The authors connect the necessary mathematical concepts and their reward, i.e. the understanding of an important piece of modern physics, along the shortest path. The unavoidable mathematical concepts and tools are presented in as straightforward manner as possible. Even though the mathematics is not very difficult, it certainly is beneficial to know some statistical thermodynamics as well as some quantum mechanics. Thus the text is suitable for the upper undergraduate curriculum.

Following the approach of Lev Landau and Evgenii Lifshitz, this book introduces the theory of special and general relativity with the Lagrangian formalism and the principle of least action. This method allows the complete theory to be constructed starting from a small number of assumptions, and is the most natural approach in modern theoretical physics. The book begins by reviewing Newtonian mechanics and Newtonian gravity with the Lagrangian formalism and the principle of least action, and then moves to special and general relativity. Most calculations are presented step by step, as is done on the board in class. The book covers recent advances in gravitational wave astronomy and provides a general overview of current lines of research in gravity. It also includes numerous examples and problems in each chapter.

Whilst general relativity is not complex in its formulation, the physical interpretation of its mathematical descriptions gives rise to a range of exciting consequences in cosmology. A detailed understanding of general relativity is therefore a prerequisite for students wishing to pursue further courses or commence research projects in cosmology and its various captivating subfields including black holes and gravitational waves. This is not a book on general relativity per se and the author's treatment of this fundamental topic is concise, with the required differential geometry summarized in an appendix. Instead, the primary goal of this book is to allow students to understand in a critical way two pillars of modern theoretical physics: inflationary theory, and quantum black holes and the information-loss problem. Accordingly, the book extensively introduces black holes and cosmology before proceeding to the important issues found in inflation and the information-loss problem. Other important topics discussed in detail include the cosmological constant and its relation to dark energy and an introduction to quantum field theory on curved backgrounds. Including numerous exercise problems, the material provides a single rigorous text for advanced students in theoretical physics and mathematics requiring an introduction to the implications and interpretation of general relativity in areas of cosmology. Readers of this text will be well prepared to follow the theoretical developments in the field and undertake research projects as part of an MSc or PhD programme.

Suitable for a one-semester course in general relativity for senior undergraduates or beginning graduate students, this text clarifies the mathematical aspects of Einstein's theory of relativity without sacrificing physical understanding.