This article, the video and the podcast accompany the Women of Mathematics photo exhibition. You can download Anne-Christine Davis' exhibition poster by clicking here. To see more profiles of female mathematicians and to find out more about the exhibition, see here. Photographs by Henry Kenyon.

Anne-Christine Davis is Professor of Mathematical Physics (1967) at the Department of Applied Mathematics and Theoretical Physics, University of Cambridge.

Plus: How and when you chose to do mathematics?

Anne-Christine Davis: I'm really a theoretical physicist, so I've always been fascinated by science, how things work, by nature – you know, the stars in the sky. From a very, very young age I became interested in science. A little story there. When I first started school, the teacher put flash cards up: A is for apple, B is for banana, C is for I can't remember what, to teach us all the alphabet. Fine, okay. Then she did it again. And I thought, "That's strange. She's done that once. We all know this now, why's she doing it again?" And the teacher picked this up, that I had learnt my alphabet first time round, and gave me a bucket of water and a pipette to play with. And I learnt a little bit about specific gravity. And I thought, "Oh, I want to be a scientist. This is fun." I was five then.

I realised that to understand physics, one has to understand mathematics; that the two are intertwined, and you can't do physics without mathematics. Since I'm not a natural experimentalist, despite that little story, I became a theoretical physicist, and of course that brought me into mathematics, and some physics ... a lot of physics is underpinned by absolutely beautiful mathematics, like Einstein's equations for example.

Plus: What's it like being a female mathematician/theoretical physicist?

Anne-Christine Davis: Oh, it's a lot easier now than it used to be. When I was young I didn't really think about it. At school I was the only girl doing A-level physics, A-level mathematics, and chemistry. It was quite isolating because I would work by myself and the boys would work together, until a lad in the year above me failed his A-levels and retook, and then he and I worked together. He liked working with me because I was bright, and I quite liked working with him because I had someone to work with.

When I went to university I went to Royal Holloway to do physics, and it was a bit more of a revelation, because having come from an inner-city comprehensive school being the only girl doing physics, when I got to university there were other women doing a degree in physics. In fact there were about five of us in our lecture room. When I did my PhD I was again in a group with all guys. It was a bit isolating, because you don't really have a close friend. I used to have friends in different research groups to mine, but not in my own research group. And I think it really struck me when I came out of my PhD viva [examination] and one of the lecturers said, "Congratulations ... so when are you going to get married?" I looked slightly surprised. And he said, "Well, you've got your PhD now, so what's there left for you to do but marry Tony?" My then-boyfriend.

And since I had no intentions of marrying Tony, I was really quite shocked. And a senior member in my department had a post-doctoral position that he was offering, and I said, "Are there any women applying?" And he turned around and said, "I wouldn't give a job to a woman when there was a man there, because a man has a family to look after, whereas a woman has a husband to look after her." And I kind of realised that the attitudes that I thought were outdated were still there. This has sort of gone on, I'm afraid, almost throughout my career, that I've come up against being the woman.

Well, I survived that experience, I did do a post-doc. My first post-doc was quite hard. My second post-doc was fantastic. I was at Imperial College, I was in the group of Tom Kibble [a well-known theoretical physicist]. Tom was definitely a mentor. He had two daughters and a son; he was desperately supportive of women and women in physics. And from that point on, until his recent death, Tom was very supportive of me.

So I think my life really changed as a post-doc in Imperial. I went to CERN [the European Organisation for Nuclear Research] for my next post-doc. There were other women at CERN; I had friends in the experimental group. There were senior women theorists hanging around, but they were in the University of Annecy or somewhere else, they weren't actually appointed in CERN, and I didn't realise at the time. In fact I've only realised a few years ago that I was the first woman to have a job in the theory division at CERN. I'm pleased I didn't know that when I was there, because I don't know if I could have coped. You know, being the first to go to university in my family, and being the first woman here, and the first woman there, you sort of think, "Hang on a minute, I'm not sure about this."

When I first came to Cambridge on a five-year research fellowship, it was actually quite a hard place to be a woman. Ruth Williams was here. She was a college teaching officer in Girton College, and not really regarded as part of the mainstream. One thing is that her research wasn't central to what the research groups were doing. She was treated a bit like a second-class citizen when I had first arrived. I came with this prestigious five-year fellowship, and I was treated like a second-class citizen. You certainly realised that Cambridge was quite a hard place to be a woman. Slowly things have improved, and now it's changed completely. It's changed out of all recognition. Quite a lot of that was down to an inspirational head of department it had, years ago now, David Crighton, who set the ball rolling, recognised the achievements of some of the women, and essentially found ways of getting them appointed into university positions. His former research student, who is now our head of department, seems to be following in that line.

Plus: What advice would you give to a young woman now who is thinking about going into mathematics?

Anne-Christine Davis: I think that if they want to go into mathematics, or science in general, if they're interested they need to persevere and follow their dream. If someone says, "You're not good enough," or someone says, "Women don't do maths," just ignore them, or tell them they're wrong, and prove they're wrong. If you really want to do it, just persevere so you can do it.

Plus: For you, what are the joys of doing mathematics and theoretical physics, and what are the challenges?

Anne-Christine Davis: My biggest joy now is being a PhD supervisor and advisor to younger people, and watching them flower. They just finished their degrees, and they blossom over the three or four years into being great researchers, and this is fantastic: I now have several research students, former research students, who are in faculty positions – in fact, several women. I've got two very successful women, one of them is in Nottingham, another in Imperial, both of them thriving, leaders in the field. And it's fantastic. This is my biggest joy now, watching these people develop.

But also I still get a kick. I've just come back from delivering the Ehrenfest colloquium in Leiden, and as far as I can tell, I'm the second woman in the history of this colloquium to do it. It's quite amusing, because you sign the wall afterwards, and so I signed the wall. There's quite a lot of signatures, but there's also Einstein there! So rather overwhelming company. When I was first thinking about this, I was a bit overwhelmed. Well, I know that they hadn't had women for years, but .... "No, you can do it." You know? And in a way I still get the kick out of realising that my work is appreciated, as well as developing the younger generation.

Plus: Could you tell us what your work is about?

Anne-Christine Davis: Well, my work recently, over many years now, has been in theoretical cosmology. We discovered that the Universe is undergoing a late period of accelerated expansion. We knew that there was a steady expansion of the Universe, this is what we get from looking at Einstein's equations. But it seems to have undergone this accelerated expansion that, when we found it out, it was completely surprising. And I've been trying to understand that. (You can read more about the expanding Universe and the discovery of its acceleration here.)

The approach I've taken is, rather than saying, "Oh, it's a cosmological constant [see here] that Einstein put in," and then try to explain why it's a funny scale, I've been thinking that it's dynamical, and it's coming from the dynamics of a field [fields are related to forces: you might be familiar with the idea of a gravitational field, related to gravity]. So I've added an extra field to Einstein's gravity. It's called a chameleon. Well, that's the one that is easiest to describe. And this should give you an extra force, a fifth force. But the way the chameleon mechanism works, the behaviour of the chameleon depends on the environment. So when the environment's very dense, like in the solar system [there is a lot of mass in the solar system] , the extra force is screened [weakened] because the chameleon becomes quite massive. But cosmologically, it's massless and unscreened, so it gives you extra effects in the cosmos.

Plus: Could you tell us about one of your favourite scientific experiences?

Anne-Christine Davis: There've been quite a few eureka moments. One of the eureka moments was actually writing down this chameleon theory, and suddenly realising that, "Actually, it works like this: we have this screening around the fifth force when matter is dense. This is how it works." And suddenly realising that on the piece of paper you've got there's the correct idea and thinking, "Wow, that's incredible."

Plus: Thank you very much!