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Bianchi works in the field of quantum gravity, which seeks to unify Einstein’s theory of relativity with quantum mechanics. Recently, he achieved an important result: taking a loop quantum gravity approach, he re-derived a famous equation for the entropy of black holes from first principles.
A formula for the entropy of a black hole may seem like an obscure result, but it’s actually an important signpost on the road to quantum gravity. The equation – which is called the Bekenstein-Hawking formula − is one of the very few in physics that contains constants from both quantum mechanics and Einstein’s gravitation. This tantalizing intersection between the two great physics theories of the 20th century has long fascinated researchers who are struggling to unify them into a 21st century theory of quantum gravity.
Loop quantum gravity, or LQG, is one of several competing theories proposed by these quantum gravity researchers. Among other things, LQG predicts that at a very small scale, spacetime is made of discrete chunks which cannot be further divided – in much the same way that Lego blocks only come in multiples of the same length.
LQG researchers have always calculated the entropy of black holes by counting the number of different ways a black hole’s horizon can be “built” out of such spacetime blocks. This build-and-count approach gave only a partial match for the Bekenstein-Hawking formula – but even this partial match was considered a triumph.
Bianchi was able to take this work one step further. Using a new formalism called spinfoams, he was able to study the energy and temperature of each of the spacetime blocks, and assign each an entropy. His resulting calculation for the total entropy of a black hole was a perfect match for the Bekenstein-Hawking formula.
Bianchi’s work has received significant attention in the scientific community and is now being further developed in collaboration with research groups internationally.
E. Bianchi, “Entropy of Non-Extremal Black Holes From Loop Quantum Gravity,” arXiv: 1204:5122.
Watch Bianchi’s talk, “Black Hole Entropy from Loop Quantum Gravity”: PIRSA: 12050053.