Black holes fascinate

It has been a successful year for theoretical physicist Monica Guica. She has gone from having no own research funding to heading a research programme financed from a number of different sources. Its aim is to discover the beautiful and interesting theory behind black holes and holography.

Monica Guica
Monica Guica. Photo: Mikael Wallerstedt.

Our world is “holographic” and black holes are the key to understanding how holography works. This is the theme of Monica Guica’s pioneering research in theoretical physics. During 2015, she was awarded several major grants totalling almost 30 million SEK from the European Research Council (ERC), the Wallenberg Foundation and the Swedish Research Council.

“I’ll use the money to put together a team and I have already recruited two researchers to do their postdocs here,” says Monica Guica.

We met at the Ångström Laboratory in the Physics Department, where Monica Guica spends half her time as a teacher and researcher. The other half she spends at the research institute Nordita in Stockholm, whose scope is to promote Nordic collaboration in the realm of theoretical physics. Recently she arranged a month long programme about black holes, that gathered many leading researchers.

Physicists have been fascinated by black holes for a long time. A black hole is a concentration of mass with a gravitational field so strong that not even light can escape it. While there is now astrophysical evidence for the existence of black holes, from a theoretical point of view they pose a great puzzle: they show that general relativity and quantum mechanics – the two best tested theories of the world – are incompatible with each other.

“Black holes can help us understand holography, a general principle which tells us that the entire world around us can be encoded on a two-dimensional surface. The theory is universal, but our understanding of how it works in the real world is limited. I want to investigate black holes in the sky – in particular, maximally spinning ones – as a crutch to understanding holography in our world. Then we can also find how gravity in our world emerges from the black hole hologram,” says Monica Guica.

She explains things slowly and methodically but this does not help much. It is hard to keep up. One thing is clear, however, Monica Guica’s research deals with some of the most fundamental entities in the universe – gravity, time and space.

She has always been interested in the interplay between gravity and quantum mechanics. First in cosmology – her first project was the cosmological constant problem – and then in the context of black holes.

“70 percent of our universe is cosmological constant, which is tremendously puzzling. If you estimate its value theoretically, you get an answer way bigger than we measure. I started by working on that.”

Monica Guica later went on to do third-cycle studies at Harvard University. 

“One of my teachers was Andrew Strominger, who was the first person to explain entropy (approximately: maximum chaos) in black holes. I studied black holes and super symmetry theory; it was very pure but not realistic.”

During her first postdoc, Monica Guica explained the entropy of a realistic black hole for the first time.

“That was nice since it was the first study of its kind.”

These days, she is working on various things but mostly on understanding realistic black holes and the connection with holography.

“I’ve been greatly guided by string theory. At first we said ‘Wow! We’ve got it! This is so simple, so beautiful!’ But then we noticed that it was very much more complicated than we first thought.”

When Monica Guica talks about her research, she repeatedly talks about how beautiful different theories are. She has come to appreciate this beauty more and more. 

“I’ve always wondered what gravity is and it’s beautiful to try to understand what time is in physical and mathematical terms. Philosophers have always wondered over metaphysical matters such as the meaning of everything, what is time, when did the universe start? We’re not there yet, but I think that physicists have made great progress in understanding fundamental, ‘metaphysical’ questions. But there’s still a long way to go.”

Monica Guica has moved around a lot in her life. She is originally from Romania but studied and did research in Chicago, Harvard, Paris and Philadelphia before ending up in Stockholm and Uppsala two years ago.

What has it been like to move between different universities?

“For me it was a great opportunity to study abroad, especially as I did not have to pay. I obtained a scholarship after having competed in the International Physics Olympiad. It was fantastic and I had excellent mentors who taught me to love physics and to love my work.”

Monica Guica still collaborates with many people and organisations overseas.

“Much of our research is about interpretation and so I constantly need to test my theories on others and receive feedback. That is why it is important to travel, make new contacts and attend conferences.”

There is no doubt that physics is a major part of her life. When I ask how this interest started, she answers that a good teacher played a decisive role.

“She was very funny and explained physical phenomena by making up stories. Now that I’m a teacher myself, I understand what a great teacher she was.”

While growing up in Romania, science olympiads were an important part of Monica Guica’s education. In her eighth year, she entered the International Physics Olympiad and was helped to prepare by her teacher. At high school, she continued competing in national and international olympiads and won a scholarship for studies in the USA.

Since last year, Monica Guica has been a teacher herself and enjoys the role. At present, she is teaching gravitation and cosmology which gives her a chance to use her favourite book written by her previous teacher professor Sean Carroll.

“Given the recent discovery of gravitation waves from two black holes which collided 1.3 billion years ago, this year I also included gravitational waves.”

They are evidence of the existence of black holes but there is still much left for Monica Guica and her colleagues to explore.

“We have a plan for the next five years and hopefully something good will come out of it. New ideas pop up all the time and all I want is to do some nice physics. I’d be very happy if I could come up with a theory which is both interesting and long-lasting.”

Annica Hulth

Facts about Monica Guica

Name: Monica Guica
Title: University lecturer in Theoretical Physics.
Interests: “I used to like reading and going to the cinema. These days, there’s too much work and too little organisation, but our students sometimes organise cinema evenings. I used to like learning languages too… Ha-ha, my life isn’t especially interesting.”
Hidden talents: No musical talent, but has been good at dancing.
Last book read: “A historical book about how Nicolae Ceaușescu came to power in Romania. Communism was very traumatic for my home country so I’m trying to understand it. Especially since we didn’t study those things in history at school. I’m now catching up.”
Makes me happy: “Dancing and speaking Spanish. I’ve spent a lot of time in South America.”
Makes me angry: “Many things but actually nothing in particular – daily irritants. I’m concentrating on learning how to deal with them.”