Focus on research: theoretical physicist Marika Taylor
Theoretical physicist Marika Taylor studies string theory and black holes.
For Marika Taylor, the fascination with physics started at an early age. ‘Even as a very small child, I remember wondering why water flowed, or why the sky was blue. My father had a background in mathematics and engineering, so he could always answer my questions.
But by the time she became a student of theoretical physics at Cambridge University and earned her PhD under Stephen Hawking, her father no longer had the answers. Since 2004, Taylor has been working at the Institute for Theoretical Physics at the University of Amsterdam (UvA), currently as senior university lecturer. And she now has a five-year-old daughter of her own. ‘She’s already started asking me the same sorts of questions.’
For now, those questions have not yet broached the theme of Taylor’s research: string theory. As Taylor explains, this physics-based theory imagines subatomic particles as being not points, but vibrating strings. Different particles – such as electrons and protons – have different vibrations. And since aspects like the speed and emission of those vibrations vary, the characteristics of the particles differ, too. ‘You can compare it with the strings on a violin, which can also produce different vibrations, and thus different tones.’
One thing about string theory that many laypeople find difficult to grasp is its implication of more dimensions than what we humans are able to perceive – as many as ten or eleven. In practice, however, Taylor works with neither three, four nor ten dimensions. The key thing to come out of string theory, she notes, is that it has given us an alternative way to describe reality. ‘It enables us to describe the three observable dimensions and gravity in two dimensions, and without gravity. That’s what’s known as the holographic principle.’
Holographic principle as dominant paradigm
When Dutch Nobel Prize winner Gerard ’t Hooft first came up with this principle in the 1990s, it signified a major paradigm shift, Taylor says. ‘All of a sudden you’re dealing with flat earth, with no apple falling from a tree and no planets revolving around the sun.’ Today it is the dominant paradigm in particle physics.
Taylor herself has had no trouble taking the new concepts on board. ‘These ideas were already beginning to circulate at the time that I was doing my doctoral research, and that makes it easier than if I had been, say, 20 years older. But dealing with a new paradigm is experienced as tricky by many. Compare it with the emergence of quantum mechanics a hundred years ago. People trained in classical physics were at a loss, Einstein being a famous example.’
Currently, the primary value of the new holographic principle is that it provides a highly practicable method for computation. The principle is used a great deal in the field of cosmology. One of Taylor’s own areas of research is black holes. Despite their complex nature, these structures actually lend themselves very well to two-dimensional description. ‘Imagine the particles in that hole colliding and bouncing off each other. They behave more or less as they would in a liquid. We know the particles’ entropy and how they move. That information is enough for me to create extremely accurate models describing the black hole.’
Taylor uses this approach to investigate various types of black holes and differently shaped spaces. ‘What are their features; for example, are they superconductive? Often, those physical characteristics aren’t yet clear to us, so I try to predict them in theories.’ Those calculations eventually bring us to new understandings in physics, she observes. A case in point is gravity – an area that has Taylor’s particular interest. ‘One thing I’d really like to know is how can we define gravity in a two-dimensional world?’
Taylor admits that describing just how two particles that move around and interact with each other ultimately gives rise to new physics models is not exactly easy. She characterises her approach as writing equations on a blackboard and then solving them. ‘You could liken it to secondary school mathematics. You write down Newton’s laws, set up an equation and solve it.’
Taylor may be a pureblood theoretician, that is not to say experimentation plays no part in her work. In fact, she says, the conclusions yielded by her research can be ‘smoking guns’ for further lab studies. And vice versa, findings from experiments can prompt new theoretical insights, such as the experiments being conducted in the particle accelerator in Geneva – though on the face of it, as Taylor points out, ‘not exactly at the vanguard of science’. Even so, if there are unexpected findings it generates more work for Taylor and other theoreticians in turn. ‘If they don’t find the Higgs particle, for example, it means we’ll have to come up with new theories. There are some aspects of string theory that we can already rule out based on experiments that have been done.’
Experimental work is seeing a rapid succession of developments. ‘When I started my PhD 15 years ago, people assumed that an accurate measurement of the beginning of the cosmos was impossible. Now we are measuring background radiation in the universe with immense precision.’ Theory is also moving fast. ‘Holography had not been predicted in any way, shape or form 20 years ago. But the principle has staying power because it represents a mathematical truth.’ The question now is if individual elements of string theory may also be substantiated by experiments in the future. ‘It’s possible that we’ll have made an equivalent theoretical leap another 20 years down the road.’
Film Marika Taylor: Black holes and holography