Published on *Science Careers* (http://sciencecareers.sciencemag.org)

November 18, 2005

Predicting how black holes collide is one of several challenges applied mathematician and 2005 EURYI award [1] winner, Snorre Christiansen (pictured left), hopes to tackle in the coming years. Just 3 years after finishing his Ph.D., this Norwegian postdoc is about to occupy a faculty chair and establish his own research group at the University of Oslo. The key to his success so far, Christiansen believes, was building on his past expertise while simultaneously developing a direction that's uniquely his own.

That, and a measure of luck. "I think I have been lucky in the choice of topics to work on, topics which later turned out to be useful for developments in an apparently different direction."

Christiansen, though only 30 years old, has studied and worked in 3 countries. After attending a French high school in Norway, Christiansen enrolled for an undergraduate engineering programme at the Ecole Polytechnique [2]in Paris. He then decided to do this research thesis for his *Diplome d'Etudes Approfondies* (DEA)--the equivalent of a MSc. degree--with the mathematics professor Jean Claude Nédélec at the Centre for Applied Mathematics [3]. Christiansen was so inspired by the mathematician's work that he decided stay on for his Ph.D.

**Computation of electromagnetic and acoustic waves**

For his doctoral project, Christiansen solved equations and developed algorithms to allow the computation--via numerical simulation--of electromagnetic and acoustic waves. The work involved the application of discretization techniques, "which basically turn a given mathematical model or equation into an algorithm that a computer can work with." The model used most often, he says, is "a continuum model with too many parameters for a computer to handle so you want to reduce this to a finite number."

Numerical simulation, says Christiansen, is of more than academic interest. The field's techniques allow the simulation of physical experiments and even the prediction of new physical phenomena. Consequently, the applications of numerical simulation techniques are frequently valuable to industry; in fact, Christiansen's Ph.D. work led to a patent. Yet, for Christiansen, the greatest satisfaction comes from mathematics. "We also work on equations that you can't immediately relate to a physical situation, but there is a beauty alone in doing the maths."

By the time he finished his Ph.D., Christiansen's heart was set on an academic career. In early 2002, he took up his first postdoc position at the Swiss Federal Institute of Technology in Zurich ( ETH Zurich [4]) working on a project related to his Ph.D. thesis. He left Zurich for Norway 6 months later, when he got an offer that was too good to refuse: a 4-year postdoc position at the Centre of Mathematics for Application ( CMA [5]) at the University of Oslo in his home country. A postdoc of 4 years was a generous offer by Norwegian standards and at that stage Christiansen was a little homesick and ready to go home, he recalls.

After just 3 years of postdoc work at CMA, Christiansen is already setting up a research group that includes 2 postdocs and 1 Ph.D. student, after securing a EURYI award worth €1.2 million. He also just got news that he has been offered an associate professor position at the Department of Mathematics at OsloUniversity.

**Success breeds success**

Although Christiansen's career has hit a lot of milestones lately, his recent success, he feels, is the accretion of several years of progress and effort. Because his Ph.D. turned out well, he had exceptional postdoc opportunities. "I think the reason I got the 4 year postdoc at CMA was simply the good results in my Ph.D., results that were both useful for industry and good mathematics." In the same way, he thinks the research progress he made as a postdoc lead him to securing the EURYI funding. And winning the EURYI award accelerated his acquisition of faculty job, Christiansen believes.

Christiansen also believes it's important to take the time to devise solid research plans that build on current skills and past accomplishments while looking toward the future, plans that show that "you have your own initiative and can change research direction while still being able to use what you have acquired." For example, in the coming years, he plans to add non-linear differential equations to his research repertoire, supplementing the linear integral-equation techniques he learned during is Ph.D. The results, Christiansen hopes, will be numerical simulations that are better suited to elucidating phenomena in theoretical physics, such as black holes.

Christiansen's time abroad has served him well, he believes. "I think it is reassuring for evaluating committees to see that I have support from researchers from different countries. And I think it has enabled me to work on relevant and up-to-date problems."

*Anne Forde is Next Wave's European Editor, North and East.*

**To series index [6] **

**Links:**

[1] http://www.esf.org/esf_genericpage.php?section=8&language=0&genericpage=1879

[2] http://www.polytechnique.fr/

[3] http://www.cmap.polytechnique.fr/

[4] http://www.sam.math.ethz.ch/

[5] http://www.cma.uio.no/

[6] http://sciencecareers.sciencemag.org/career_development/issue/articles/2005_11_11/the_european_young_investigator_awards_meet_the_2005_winners/(parent)/68/