Logic List Mailing Archive

PhD student position in Theoretical Computer Science, Stockholm (Sweden), Deadline: 15 Dec 2013

The Theory Group at KTH Royal Institute of Technology invites applications 
for a PhD position in theoretical computer science.

KTH Royal Institute of Technology is the leading technical university in 
Sweden. The Theory Group at KTH (http://www.csc.kth.se/tcs/) offers a 
strong research environment covering a wide range of research topics such 
as complexity theory and approximation algorithms, computer and network 
security, cryptography, formal methods and natural language processing. 
The group has a consistent track record of publishing in the leading 
theoretical computer science conferences and journals worldwide, and the 
research conducted here has attracted numerous international awards and 
grants in recent years. We are now set to expand further, and this 
position is just one of several new openings.

Proving formulas in propositional logic is a problem of immense importance 
both theoretically and practically. This computational task is widely 
believed to be intractable in the worst case, although proving (or 
disproving) this is a major open problem in theoretical computer science 
and mathematics. (This is one of the famous million dollar Millennium 
Problems, known as the P vs. NP problem.) In spite of this, today 
so-called SAT solvers are routinely used to solve large-scale real-world 
problem instances with millions of variables. The intriguing question of 
when SAT solvers perform well or badly, and what properties of the 
formulas explain this behaviour, remains quite poorly understood.

Proof complexity studies formal systems for reasoning about logic 
formulas. This field has deep connections to fundamental questions in 
computational complexity, but another important motivation is the 
connection to SAT solving. All SAT solvers use some kind of method or 
system in which proofs are searched for, and proof complexity analyses the 
potential and limitations of such proof systems (and thereby of the 
algorithms using them).

Our research aims to advance the frontiers of proof complexity, and to 
leverage this research to shed light on questions related to SAT solving. 
We want to understand what makes formulas hard or easy in practice, and to 
gain theoretical insights into other crucial but poorly understood issues 
in SAT solving. We are also interested in exploring the possibility of 
basing SAT solvers on stronger proof systems than are currently being 
used. In order to do so, however, a crucial step is to obtain a better 
understanding of the corresponding proof systems, and in this context 
there are a number of well-known and relatively longstanding open 
questions in proof complexity that we want to study and try to resolve.

This research project is led by Jakob Nordstrom 
(http://www.csc.kth.se/~jakobn) and is financed by a Breakthrough Research 
Grant from the Swedish Research Council and a Starting Independent 
Researcher Grant from the European Research Council. The group currently 
consists of one postdoctoral researcher and two PhD students (in addition 
to the project leader). Travel funding is included, and the group also 
receives short-term and long-term visitors on a regular basis.

This is a four-year full-time employed position, but PhD positions usually 
(but not necessarily) include 20% teaching, in which case they are 
prolonged for one more year. The successful candidate is expected to start 
in August-September 2014, although this is to some extent negotiable.

The application deadline is December 15, 2013. See 
http://www.csc.kth.se/~jakobn/openings/D-2013-0620-Eng.php for the full, 
formal announcement with more information and instructions for how to 
apply. Informal enquiries about this position are welcome and may be sent 
to Jakob Nordstrom.