Source: University of Canterbury

16 December 2020

The Royal Swedish Academy of Sciences is awarding the Oskar Klein Medal to the University of Canterbury’s renowned Canterbury Distinguished Professor Roy Kerr.

He will give the 2020 Oskar Klein Memorial Lecture on Friday morning (NZ time), on campus at the University of Canterbury.

In 2019, astronomers captured the first image of a black hole, heralding a revolution in our understanding of the universe’s most enigmatic objects, and proving Canterbury Distinguished Professor Kerr’s 56-year-old solution correct.

**The 2020 ****Oskar Klein Memorial Lecture** **is titled: ‘Kerr Black Holes have no Singularities’.**

**Abstract:** All proofs that Black Holes have real physical singularities make assumptions about the nature of the matter inside and of certain light rays. It is shown that there are such lines inside Kerr that do not satisfy these assumptions. As an example to show that the behaviour inside the event horizon for real matter is very different from the idealisation of empty Kerr we consider two slowly rotating Black Holes collapsing to a single object. There have been many different approaches used to calculate the collapse of two BHs to a single one. We show that the best starting point is the Kerr-Schild form for a Black Hole. This explains the unexpected accuracy of a calculation by Jose Rodriguez for the first gravitational wave discovery, GW150914. (More at: www.okc.albanova.se/research/memorial-lecture)

Given the travel restrictions, Canterbury Distinguished Professor Kerr will deliver the lecture internationally via Zoom (https://stockholmuniversity.zoom.us/j/63531400896), 8am, Friday 18 December New Zealand time (8pm on Thursday 17 December in Stockholm, Sweden), with a physical audience in Lecture Theatre E5, Engineering Core, at the University of Canterbury’s Ilam campus.

**Roy Kerr biography:**

Professor Roy Patrick Kerr is an eminent mathematician, known internationally for discovering the Kerr solution, an exact solution to the Einstein field equation of general relativity.

Professor Kerr began his long association with the University of Canterbury in 1951, earning a Bachelor of Science in 1954 and a Master of Science in 1955. He then went to Cambridge to research his PhD, and was awarded his doctorate in 1959.

From England, Dr Kerr moved to the United States, where as a postdoctoral student in Syracuse, New York, he worked with Professor Peter Bergmann, Albert Einstein’s collaborator.

In 1963, while working at the University of Austin in Texas, Dr Kerr did something that had eluded scientists for 47 years – he discovered the solution to Einstein’s equations that define the space outside a rotating star or black hole. This was something many in the field doubted could be done.

Professor Kerr’s discovery triggered a revolution in the field of astrophysics, and is now known as the ‘Kerr geometry’ or ‘Kerr solution’.

Dr Kerr returned to New Zealand and the University of Canterbury in 1971, where he became a Professor of Mathematics for 22 years until his retirement in 1993, when he was appointed an ‘Emeritus Professor’. Professor Kerr developed strong links with the department of physics and astronomy, where his seminal work on the Kerr Vacuum provided the basis of much research and teaching.

Professor Kerr was awarded the British Royal Society’s Hughes Medal in 1984 and the Rutherford Medal from the New Zealand Royal Society in 1993. He was made a Companion of the New Zealand Order of Merit in 2011, and was awarded the 2013 Albert Einstein medal by the Albert Einstein Society in Switzerland.

The University of Canterbury awarded the rare honour of the title Canterbury Distinguished Professor to Professor Roy Kerr who also received the prestigious Crafoord Prize in Sweden in 2016. Canterbury Distinguished Professor is the highest academic title that can be awarded by UC and has been conferred only twice before in the University’s history. Title recipients are Nobel Prize winners or equivalent, such as the Crafoord Prize, which is worth over $NZ1 million

**Stephen Hawking on Roy Kerr:**

One of the world’s foremost theoretical physicists famous for his work on black holes, Stephen Hawking, described Kerr’s discovery in his celebrated book, *A Brief History of Time.*

Professor Hawking wrote: “In 1963, Roy Kerr, a New Zealander, found a set of solutions of the equations of general relativity that described rotating black holes. These ‘Kerr’ black holes rotate at a constant rate, their size and shape depending only on their mass and rate of rotation. If the rotation is zero, the black hole is perfectly round and the solution is identical to the Schwarzschild solution. If the rotation is non-zero, the black hole bulges outward near its equator (just as the Earth or the Sun bulge due to their rotation), and the faster it rotates, the more it bulges. So … it was conjectured that any rotating body that collapsed to form a black hole would eventually settle down to a stationary state described by the Kerr solution. In 1970 a colleague and fellow research student of mine at Cambridge, Brandon Carter, took the first step toward proving this conjecture. He showed that, provided a stationary rotating black hole had an axis of symmetry, like a spinning top, its size and shape would depend only on its mass and rate of rotation. Then, in 1971, I proved that any stationary rotating black hole would indeed have such an axis of symmetry. Finally, in 1973, David Robinson at Kings College, London, used Carter’s and my results to show that the conjecture had been correct: such a black hole had indeed to be the Kerr solution.”