KTH / CSC / Teorigruppen / Jakob Nordström / Forskning

Forskning

På denna webbsida finns forskningsartiklar, doktorsavhandling, examensarbetesrapport, bilder från några föredrag och diverse annat forskningsrelaterat. För att det ska gå lättare att hålla sidan uppdaterad delar den innehållet med sin engelska tvillingsida, och eftersom all min forskning bedrivs på engelska förekommer det en hel del av det språket nedan.

Forskningsartiklar

• Yuval Filmus, Massimo Lauria, Jakob Nordström, Neil Thapen, and Noga Zewi. Space Complexity in Polynomial Calculus. Submitted, 2011.
• Trinh Huynh and Jakob Nordström. On the Virtue of Succinct Proofs: Amplifying Communication Complexity Hardness to Time-Space Trade-offs in Proof Complexity. To appear in Proceedings of the 44th Annual ACM Symposium on Theory of Computing (STOC '12), May 2012.
• Jakob Nordström. New Wine into Old Wineskins: A Survey of Some Pebbling Classics with Supplemental Results. Manuscript in preparation. To appear in Foundations and Trends in Theoretical Computer Science. Current draft version available for download—comments are welcome.  
• Jakob Nordström. Pebble Games, Proof Complexity, and Time-Space Trade-offs. To appear in Logical Methods in Computer Science, 2012.  
• Arnab Bhattacharyya, Elena Grigorescu, Jakob Nordström, and Ning Xie. On the Semantics of Local Characterizations for Linear-Invariant Properties. Submitted, 2011.  
• Jakob Nordström and Alexander Razborov. On Minimal Unsatisfiability and Time-Space Trade-offs for k-DNF Resolution. In Proceedings of the 38th International Colloquium on Automata, Languages and Programming (ICALP '11), pages 642-653, July 2011.  
• Jakob Nordström. On the Relative Strength of Pebbling and Resolution. To appear in ACM Transactions on Computational Logic, 2011.  
• Eli Ben-Sasson and Jakob Nordström. Understanding Space in Proof Complexity: Separations and Trade-offs via Substitutions (Extended Abstract). In Proceedings of the 2nd Symposium on Innovations in Computer Science (ICS '11), pages 401-416, January 2011.  
• Eli Ben-Sasson and Jakob Nordström. Understanding Space in Proof Complexity: Separations and Trade-offs via Substitutions. Technical Report TR10-125, Electronic Colloquium on Computational Complexity (ECCC), August 2010.   This is a merged and updated version of the two ECCC technical reports TR09-034 and TR09-047, which two papers it subsumes.
• Jakob Nordström. On the Relative Strength of Pebbling and Resolution (Extended Abstract). In Proceedings of the 25th Annual IEEE Conference on Computational Complexity (CCC '10), pages 151-162, June 2010.  
• Jakob Nordström. A Simplified Way of Proving Trade-off Results for Resolution. Information Processing Letters, volume 109, number 18, pages 1030-1035, August 2009.  
• Jakob Nordström. Narrow Proofs May Be Spacious: Separating Space and Width in Resolution. SIAM Journal on Computing, volume 39, issue 1, pages 59-121, May 2009. (Special issue on STOC '06.)  
• Eli Ben-Sasson and Jakob Nordström. Short Proofs May Be Spacious: An Optimal Separation of Space and Length in Resolution. Technical Report TR09-002, Electronic Colloquium on Computational Complexity (ECCC), January 2009.  
• Eli Ben-Sasson and Jakob Nordström. Short Proofs May Be Spacious: An Optimal Separation of Space and Length in Resolution. In Proceedings of the 49th Annual IEEE Symposium on Foundations of Computer Science (FOCS '08), pages 709-718, October 2008.  
• Jakob Nordström and Johan Håstad. Towards an Optimal Separation of Space and Length in Resolution (Extended Abstract). In Proceedings of the 40th Annual ACM Symposium on Theory of Computing (STOC '08), pages 701-710, May 2008.  
• Jakob Nordström and Johan Håstad. Towards an Optimal Separation of Space and Length in Resolution. Technical Report TR08-026, Electronic Colloquium on Computational Complexity (ECCC), February 2008.  
• Jakob Nordström. Narrow Proofs May Be Spacious: Separating Space and Width in Resolution (Extended Abstract). In Proceedings of the 38th Annual ACM Symposium on Theory of Computing (STOC '06), pages 507-516, May 2006. Delad vinnare av Danny Lewin Best Student Paper Award.  

Doktorsavhandling

Jakob Nordström. Short Proofs May Be Spacious: Understanding Space in Resolution. PhD thesis, Royal Institute of Technology, Stockholm, Sweden, May 2008. Belönad med Ackermann Award 2009 för "enastående avhandlingar inom datavetenskaplig logik" av European Association for Computer Science Logic.  

Examensarbetesrapport

Jakob Nordström. Stålmarck's Method Versus Resolution: A Comparative Theoretical Study. Master's thesis TRITA-NA-E0184, Stockholm University, Stockholm, Sweden, 2001.  

Några föredrag

• Understanding the Hardness of Proving Formulas in Propositional Logic. Updated version of a survey talk about SAT solving, proof complexity, and time-space trade-offs in resolution and other proof systems given at Stockholm University, November 2011.
• On Minimal Unsatisfiability and Time-Space Trade-offs for k-DNF Resolution. Brief talk given at ICALP '11, July 2011.
• On Proof Complexity Lower Bounds and Possible Connections to SAT Solving. Brief talk given at the Synergies in Lower Bounds workshop at Aarhus University, June-July 2011, and (slightly modified) at the Oberwolfach workshop Mathematical Logic: Proof Theory, Constructive Mathematics, November 2011.
• On the Semantics of Local Characterizations for Linear-Invariant Properties. Brief talk given at the Dagstuhl seminar on Computational Complexity of Discrete Problems, March 2011.
• On the Semantics of Local Characterizations for Linear-Invariant Properties. Talk given in the Theory Group seminar series at KTH, November 2010, and (slightly modified) at the Technion – Israel Institute of Technology, Haifa, December 2010.
• Understanding the Hardness of Proving Formulas in Propositional Logic. Survey talk about SAT solving, proof complexity, and resolution time-space trade-offs given at Lund University, October 2010 and in a slightly expanded and more technical version at the Complexity and Finite Models (CMF 2011) workshop in Paris, June 2011.
• Understanding Space in Proof Complexity: Separations and Trade-offs via Substitutions. Brief overview talk, with a slightly more applied angle, given at the Propositional Proof Complexity: Theory and Practice workshop at FLoC '10, July 2010, and (in a slightly shorter version) at ICS '11, January 2011.
• Understanding Space in Proof Complexity: Separations and Trade-offs via Substitutions. Yet another survey talk about my PhD thesis and some subsequent work, but with a slightly more applied angle, given at the International Workshop on Tractability at Microsoft Research Cambridge, UK, July 2010.
• On the Relative Strength of Pebbling and Resolution. Brief overview talk given at CCC '10, June 2010, and in the Theory Group seminar series at KTH, October 2010. (also available in video from Harvard)
• Understanding Space in Proof Complexity: Separations and Trade-offs via Substitutions. Survey talk about my PhD thesis and some subsequent work given in the CSAIL Theory of Computation Colloquium series, April 2010 and then (slightly modified) at the University of Toronto and the Royal Institute of Technology, May 2010. Yet another modified and updated version of this talk, but with the title Understanding the Hardness of Proving Formulas in Propositional Logic, was given at the proof complexity workshop in Banff, Canada, October 2011.
• Understanding Space in Proof Complexity. Survey talk about my PhD thesis and some subsequent work given at the Ackermann Award ceremony at CSL '09, September 2009.
• Understanding Space in Proof Complexity: Separations and Trade-offs via Substitutions. Brief overwiev talk about the ECCC reports TR09-034 and TR09-047 given at the Barriers in Computational Complexity workshop in Princeton, August 2009. (also available in video from the Center for Computational Intractability)
• Guest lectures about proof complexity in the MIT Advanced Complexity Theory course, April 2009. Handwritten lecture notes and (mostly accurate) scribed notes for lecture 1  and lecture 2. 
• Understanding Space in Resolution: Optimal Lower Bounds and Exponential Trade-offs. Talk about our FOCS '08 paper and ECCC report TR09-034 given at the Dagstuhl seminar on Computational Complexity of Discrete Problems, September 2008, and (slightly modified) in the MIT CSAIL Algorithms and Complexity Seminar series, October 2008.
• Short Proofs May Be Spacious: An Optimal Separation of Space and Length in Resolution. Brief overview talk given at FOCS '08, October 2008.
• Towards an Optimal Separation of Space and Length in Resolution. Brief overview talk given at STOC '08 and at the NORDITA Physics of distributed information systems (PhysDIS) workshop, May 2008.
• Towards an Optimal Separation of Space and Length in Resolution. Talk given at the Technion – Israel Institute of Technology, Haifa, and the Weizmann Institute of Science, Rehovot, in Israel in March 2008. Some technical slides in the appendix.
• Narrow Proofs May Be Spacious: Separating Space and Width in Resolution. Very detailed technical talk in the Theory Group seminar series at KTH, June 2006.
• Narrow Proofs May Be Spacious: Separating Space and Width in Resolution. Brief overview talk given at STOC '06, May 2006.
• Narrow Proofs May Be Spacious: Separating Space and Width in Resolution. Somewhat detailed talk given at the Dagstuhl seminar on Complexity of Boolean Functions in March 2006 and (slightly modified) at the Isaac Newton Institute Workshop New Directions in Proof Complexity in Cambridge, UK, in April 2006. (also available in audio from the Isaac Newton Institute)
• Short Proofs Are Narrow (Well, Sort of), But Are They Tight? Fairly technical talk about width and space in resolution in the Theory Group PhD student seminar series, KTH, April 2006.
• Stålmarck's Method versus Resolution: A Comparative Theoretical Study. Rather informal overview of the subject matter of my Master's thesis, November 2001.
• Stålmarck's Method versus Resolution: A Comparative Theoretical Study. More technical account of the most important results in my Master's thesis, November 2001.

Diverse

• [på svenska] Jakob Nordström. Kort populärvetenskaplig sammanfattning av min doktorsavhandling. Försök till kort (knappt 2 sidor) sammanfattning av ungefär vad min doktorsavhandling handlar om och varför man är intresserad av att undersöka den typen av frågor, september 2009.  
• [på svenska] Jakob Nordström. Om formler, bevis och andra komplexa saker. Något förkortad och översatt version av inledningskapitlet i min doktorsavhandling Short Proofs May Be Spacious: Understanding Space in Resolution, maj 2008.