Léo Ramos Chaves
Myers during his visit to São Paulo in July 2017, when he taught courses for Latin American students who would compete to enroll in an international master’s degreeLéo Ramos ChavesCanadian physicist Robert Myers, 58, began his research career in the 1980s, attempting to discover what black holes would be like in a Universe with more than the four known dimensions: three spatial (length, width and height) and time. The work did not go as expected, but it paved the way for him to become an international expert on string theory, the physical model describing the Universe as made up of microscopic filaments—strings—vibrating in up to 10 dimensions.
Since then, Myers has published 211 articles, which have been cited about 22,000 times, and has been outlining how to use string theory to understand gravitation. He was recently considered one of the most influential researchers in his field. His name was in the 2014 and 2015 editions of the World’s Most Influential Scientific Minds ranking, which lists the authors of the most cited articles in the last decade in different scientific areas.
Myers grew up in Deep River, a small town of 5,000 in the province of Ontario, Canada. He decided to study physics because it seemed to him to be the most challenging field, and since 2001 he has been a researcher at the Perimeter Institute for Theoretical Physics, one of the world’s most innovative theoretical physics centers, based in Waterloo, also in the province of Ontario.
In July 2017, Myers was in São Paulo and taught almost 100 advanced Latin American undergraduate physics students. They were preparing to compete for the few openings in the master’s degree program to be jointly administered by Perimeter and the International Center for Theoretical Physics (ICTP) of the South American Institute for Fundamental Research (SAIFR), at São Paulo State University (Unesp). In the following interview, Myers spoke about working at Perimeter and the area of physics he has been helping develop.
You’ve been at Perimeter since the beginning and you’re also a professor at the University of Waterloo. What are the differences between the two institutions?
I believe I was the first researcher hired by Perimeter. The University of Waterloo is a large institution with about 10,000 students and various interests and activities. It has a good reputation in engineering and mathematics. In physics, it is beginning to improve. At Perimeter, the focus is on physics. It’s in Waterloo because that’s where Mike Lazaridis’ business is located [he owns the BlackBerry cell phone company and donated $100 million to found Perimeter]. When they established the institute, they wanted partnerships with other institutions, but there was a conscious decision to not be part of the university. We have partnerships with the University of Toronto, the University of York, McMaster University and the University of Western Ontario. We hire professors with them and work with their students. This gives us flexibility. In a university, people are part of a larger team, which follows the priorities set by the president. We have to negotiate more and try to convince the other parties that our personal goals are also important. At Perimeter, we set our priorities without interference.
You have the freedom to choose what to study?
Yes, and it is much easier to change fields and follow new paths. In part because we are a small institution. One of our characteristics is to aim high and study challenging questions.
How many students are at Perimeter? Are the students stronger than those at other institutions?
All together, there are no more than 100. There are about 30 master’s degree students, and 45 in the doctoral program. There is the Visiting Graduate Fellowship program, which brings a good number of advanced-level graduate students to the institute every year. They work for a while at Perimeter, but do their theses and research at other universities. All our students are students at Waterloo, since the institute does not grant master’s and doctoral degrees. The initial idea was to do one thing well. By establishing partnerships, the institute and the other institutions benefit mutually. Today, Waterloo attracts better physics students than 15 years ago.
Recently, you were twice chosen one of the most influential scientists in the world in your field. In addition, you have published over 200 articles, cited 22,000 times. What is your secret?
I worked a lot. I don’t know what advice to give. I tell my students they should look for something they really like. The rest comes from effort. I see a lot of people pursuing a career because they need a job to survive. I was lucky to get a fun job. Enthusiasm nurtures many researchers. It is much more than a job or a career, it is something we are passionate about. We like to work hard, for long hours, to discover new formulas or analyze results from experiments.
Your most-cited article (1,539 citations) is on black holes. What did you study?
That article was from 1986. It was my PhD dissertation at Princeton University. At the time, there was a second revolution in string theory that excited everyone. We live in a four-dimensional spacetime: three spatial dimensions and one temporal dimension. And string theory is formulated using a spacetime with 10 dimensions. I was interested in understanding what black holes would be like in a Universe with more than four dimensions. I had an idea in mind, but it did not work. Black holes arise under extreme conditions, in which gravity is very strong, and can provide information on several aspects of the theory. One of its most exciting features is that it is a theory of quantum gravitation [string theory includes a quantum description of gravity and attempts to reconcile quantum mechanics, which describes the three physical forces relevant to microscopic phenomena—the electromagnetic, strong nuclear and weak nuclear forces—with Einstein’s theory of general relativity, which describes the force of gravity and macroscopic phenomena]. Over time, physicists have discovered connections and have been able to study black holes and have insights related to string theory.
Was it unusual to study black holes in several dimensions?
It was ahead of its time. It interested me and my advisor, Malcolm John Perry. As I advanced, I tried to take advantage of opportunities. I often say that we have a toolbox of ideas and techniques. The more tools you put in the box, the greater your ability to solve problems. At the moment, I’m excited to be working in a field that tries to understand how the ideas of quantum information theory could be useful for understanding black holes and quantum gravitation.
What would you like to discover?
Black holes are a kind of playground for mathematicians. Currently, any theory that tries to explain highly energetic astrophysical phenomena attributes them to black holes. Forty years ago, they looked for more elegant solutions. In the early 1970s, Jacob Bekenstein [1947-2015] was the first physicist to look at black holes from a different perspective and try to incorporate information theory ideas into general relativity, which deals with gravity. He carried out mental experiments that tried to imagine the physics involved in a specific phenomenon and said that, in order for the physics we know to make sense, black holes should have entropy [a measure of how energy can be distributed among the microscopic components of an object]. He also said that this entropy should be proportional to the surface area of the black hole. Many people were skeptical. To have entropy, an object must have an internal structure, such as molecules of a gas enclosed in a room. And, from the point of view of general relativity, it did not make sense to think of an internal structure for black holes.
How was the idea received?
Bekenstein was a graduate student at Princeton and people questioned his ideas until, years later, Stephen Hawking proposed that black holes could release thermal radiation when quantum fluctuations occur. If these objects act as a heat reservoir, they have to have entropy. Bekenstein and Hawking made a very precise prediction about what the entropy of a black hole would be. It is a remarkable formula. On the one hand, it provides information about a black hole’s area, a two-dimensional geometric feature of space-time. On the other, it relates this to entropy, which implies something about the internal structure, or the quantum state of the black hole. This formula suggests that information about the inner structure or quantum nature of a black hole may be encoded in its geometry. I tell this story because, in order to try to better understand this idea and others related to it, we constantly return to the question of how the geometry of space-time encodes information about the microscopic states that we cannot see, or at least not yet. Bekenstein realized early on that entropy was a way of characterizing information, but it took time for the rest of us to recognize this. Instead of using information theory to try to understand important aspects of gravity and black holes, today we use quantum information theory, a field that grew out of the idea of using quantum mechanics to produce new types of computers.
How can this knowledge be used?
To build faster computers or better understand the behavior of matter. There are condensed matter theories that use the entropy of entanglement or ideas from quantum information theory to describe new states of matter [they are exotic states that cannot be described by the phenomena—magnetism, density, etc.—used to characterize common materials]. This has already provided tools for physicists in the past. Now a new group of physicists is going to quantum information theorists to borrow new tools that can allow us to look differently at issues that we have been analyzing for a long time.
What kind of questions would you like to answer with these tools?
Ultimately, we want to discover how to unify the theories that describe the four known forces, one of the great mysteries for theoretical physicists. On the one hand, we have quantum mechanics. It works very well and makes predictions that can be verified experimentally, but only on the atomic scale. On the other hand, we have general relativity, which describes the phenomena associated with larger objects, such as the movement of planets or the evolution of the Universe. As a theoretical physicist, I can imagine mental experiments in which the two theories play an important role. There should be a way to unify them. But we have not figured out how to do this consistently. The hope is that we are not looking at the problems in the right way, and that quantum information theory will help us progress.
The goal is to achieve what is called the theory of everything?
You can call it that. Some call it the theory of quantum gravitation.
One of the tools used is the holographic principle, a theoretical proposition according to which we can describe the information contained in a three-dimensional object, such as a sphere, using what is known about its surface, a two-dimensional object. Is this an attempt to eliminate gravity from the problem?
In a way, it is. I think of holography as a dictionary. There are phenomena we want to describe and we can use two languages. One is a special class of quantum field theory, known as conformal field theory. The details do not matter, but, in this language, gravity does not appear. In the other, we use gravity, but in an extra dimension. One of the obstacles is that, on the one hand, I have quantum field theory, which describes the world in three dimensions, two of space and one of time. How am I going to use it to describe phenomena that occur in four dimensions, three of space and one of time?
Is gravity unimportant on the scale treated by quantum field theory?
I would not describe it that way. The concept of gravity does not exist in quantum field theory. It is as if it were a language in which that word did not exist. So, I don’t have to worry about it. It is an advantage because this theory is a system with which we should feel comfortable when doing calculations. Since the physics I describe with this theory is the same as that which I describe with general relativity, which includes gravity, we use our intuition to understand how things work in one, and then try to translate and understand what that means in the other. In reality, there is a dialog. In some situations, we use general relativity to perform calculations that are difficult in quantum field theory, and thus learn something about the latter. In other situations, we do calculations with the tools of quantum field theory in order to try to learn something new about gravitation. Work of this type has been in progress for about 20 years, and it is a complicated dictionary.
What would you like to discover, in the end?
I would like to understand the Hawking radiation that escapes from black holes. I have not studied it in detail, but it seems that there are inconsistencies.
In the fact that black holes emit some form of radiation?
Emitting radiation means releasing energy. If enough time passed, a black hole could emit all of its energy and disappear. This creates a paradox, because quantum mechanics says that information in the Universe cannot just disappear, it has to be conserved, just like energy. It is an important question that, perhaps, will only answered by a complete theory of quantum gravitation.
What would this complete theory allow you to describe?
Everything, from the smallest to the largest scale. This would be important, for example, for understanding what happened during the first seconds of the Universe. We know that the Cosmos is rapidly expanding. If we could reverse time, we would see the Universe shrink to a point where the effects of quantum gravity would become important. In principle, it could give us insight into where the Universe came from, where it all began.
