Proceedings of the National Academy of Sciences of the United States of America

About the PNAS Member Editor
Name Ashtekar, Abhay V.
Location The Pennsylvania State University
Primary Field Physics
Secondary Field Astronomy
 Election Citation
Ashtekar has been an international leader in the field of gravitationalphysics for three decades. He has made major contributions to general relativity and quantum fields in curved spacetime, and is the primary developer of the loop representation approach to quantum gravity, which has spawned many new ideas and insights.
 Research Interests
Ashtekar's group developed the theory of quantum Riemannian geometry that lies at the foundation of Loop Quantum Gravity. It describes 'atoms of geometry'. Space-time can be visualized as a fabric that is woven by one-dimensional quantum threads. Thanks to this specific microscopic description, the big bang of general relativity is tamed and replaced by a big bounce. Consequently, there are no infinities and one can study the very early universe unambiguously. This theory has been developed in detail, shown to make predictions that are borne out by the cosmic microwave background missions, and has also made predictions for future observations. It brings out an unforeseen relation between the very small and the very large. Ashtekar and his team have also analyzed global problems in general relativity. They developed the notion of quasi-local horizons that is widely used in numerical simulations of black hole collisions, as well as in the investigations of the quantum mechanical evaporation of black holes. On another front, they have shown that the presence of a cosmological constant introduces unforeseen issues in the theory of gravitational waves and constructed a framework to address them. In broad terms, these diverse projects explore the interface of physics and geometry.

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