From GusWiki

Contents 1 Academic Papers 1.1 Causality 1.2 Information Retrieval / NLP 1.3 Student modeling 1.4 Logic 1.5 ToDo 2 Half-Baked Ideas 3 Project Proposals 4 Papers for classes, or for fun 4.1 2004 4.2 2003 4.3 2002 4.4 2001 4.5 2000 4.6 1990's 5 See also

[edit] Academic Papers

[edit] Causality

• Gustavo Lacerda, Peter Spirtes, Joseph Ramsey, Patrik O. Hoyer - Discovering Cyclic Causal Models by Independent Components Analysis Proceedings of the 24th Conference on Uncertainty in Artificial Intelligence (UAI-2008) (plenary talk [video])

Generalizes the LiNGAM method to deal with cycles, and proposes stability as a partial solution to the underdetermination. Cyclic SEMs correspond to linear dynamical systems.

• P. O. Hoyer, A. Hyvärinen, R. Scheines, P. Spirtes, J. Ramsey, G. Lacerda, and S. Shimizu - “Causal discovery of linear acyclic models with arbitrary distributions” Proceedings of the 24th Conference on Uncertainty in Artificial Intelligence (UAI-2008)

How to intelligently combine LiNGAM with methods based on conditional independence tests (this is useful when it may be the case that more than 1, but not all error terms are Gaussian). (Future work: to make this smoother, use a Bayesian search that considers many equivalence classes)

• Gustavo Lacerda, Peter Spirtes, Joseph Ramsey - Learning Structural Equation Models (SEMs) from observational data: the two approaches (poster) Presented at the Student Symposium at IPAM GSS2007.

Presents the problem (which the paper above solves), before we knew how to intelligently combine them. See above Hoyer et al, UAI2008.

[edit] Information Retrieval / NLP

• S. Fissaha Adafre, W.R. van Hage, J. Kamps, G. Lacerda de Melo, and M. de Rijke - The University of Amsterdam at CLEF 2004, In: C. Peters and F. Borri, editors, Working Notes for the CLEF 2004 Workshop, pages 91-98, 2004.

I think this paper was a blend of many people's independent projects. My part was building a bilingual Portuguese-English dictionary from a parallel corpus. Since were had a very large corpus, no machine learning, or clever word-alignment algorithms were needed. Instead, I created a score that used index-proximity, a cognate heuristic, and word-length correlations; and bootstrapped from a hand-made dictionary of 100 word-pairs.

[edit] Student modeling

• Matsuda, N., Cohen, W. W., Sewall, J., Lacerda, G., & Koedinger, K. R. (2008) - Why tutored problem solving may be better than example study: Theoretical implications from a simulated-student study. In Proceedings of the International Conference on Intelligent Tutoring Systems.

• Matsuda, N., Cohen, W. W., Sewall, J., Lacerda, G., & Koedinger, K. R. (2007) - Predicting students performance with SimStudent that learns cognitive skills from observation. In R. Luckin, K. R. Koedinger & J. Greer (Eds.), Proceedings of the international conference on Artificial Intelligence in Education (pp. 467-476). Amsterdam, Netherlands: IOS Press.

• Noboru Matsuda, William W. Cohen, Jonathan Sewall, Gustavo Lacerda, and Kenneth R. Koedinger - Evaluating a Simulated Student using Real Students Data for Training and Testing, (AIED 2007)

• Noboru Matsuda, William W. Cohen, Jonathan Sewall, Gustavo Lacerda, and Kenneth R. Koedinger - Predicting Students’ Performance with SimStudent: Learning Cognitive Skills from Observation (International Conference on User Modeling 2007).

[edit] Logic

• Gustavo Lacerda - An Information-Theoretic Upper Bound on the Length of the Shortest Proof (draft) (2008) - not sure where to submit

"Short theorems can't have arbitrarily long proofs as their shortest proof"

Uses the (uncomputable) -:Busy Beaver function to bound the length of the shortest proof for any given axiom system. My first (and probably my last) contribution to mathematical logic. I wonder if this result might be considered too easy for publication.

[edit] ToDo

links for (wikitalk page (containing the abstract), PDF in print, best PDF, code, errata)

[edit] Half-Baked Ideas

My ideas at the half-bakery (old ones)

[edit] Project Proposals

• A QED Project for Science: The Promises of Computer-Level Formalization (2006)

• Formalizing Science Intuitively (2004)

• Using weak definitions in formal mathematics

[edit] Papers for classes, or for fun

[edit] 2004

• "Modeling Cognitive Theories of Autism: Interpretations of the Executive Dysfunction Theory"

• "Automatic Bilingual Dictionary Building from a Parallel Corpus". The results were published at Adafre, van Hage, Kamps, Lacerda, de Rijke - "The University of Amsterdam at CLEF 2004"

• with Henrik Nordmark: "Identifying Structure in the Narratives of Portuguese-Speaking Children.": reports on experiments performed with Portuguese children at the Spaarndammer School.

[edit] 2003

• with Samson de Jager: "Comparing Baltag-Moss-Solecki Update Logic with Burrows-Abadi-Needham Logic of Authentication"

• with Dr. Jacques Robin, I gave a lecture about logic in AI, including non-monotonic logic, abduction, referential opacity & modal epistemic logic, and different systems for belief revision (most of the material came from Russell&Norvig)

• independent: "Incenting Honest Reporting of Probability Estimates": a non-trivial problem with a very elegant solution which I didn't know about at the time: proper scoring rules. Available as a blog post.

[edit] 2002

• independent: "An Introduction to Tuning Theory." About the small-integer-ratio theory of consonance, and the tradeoff between just intervals and transposibility: Defined utility measures. I suggest that the perception of consonance will be dependent on the instrument's harmonic series.

[edit] 2001

• independent: "Stochastic Simulation of a Sexual Population with a Sickle-Cell-Anemia like disease", where the simulations show that the frequency of this sometimes-beneficial (heterozygous individuals) allele tends to reach an equilibrium.

• with Dr. Karl Voss: "Using Wavelets for Lossy Data Compression": discusses how to pick a basis, presents evaluation measures, demonstration.

[edit] 2000

• with Paul Jakowski: "Non-Parametric Kernel Density Estimation in a Circular Domain": investigated the distribution of emails over the course of a day and treated the issue of smoothing.

• with Dr. Alexei Ashikhmin: "An efficient algorithm for error-correction in noisy channels": about my work at Bell Labs. On this talk, I explained algebraically why the simple Viterbi algorithm works.

[edit] 1990's

• 1999: with Dr. David Farmer: "On the number of Roots of Polynomials over Finite Fields": simple algebraic number theory applied to a seemingly-unexplored problem, intuitions supported by experiments on the computer.

• 1997: high school Extended Essay: sphere falling in a viscous liquid, where I generalize Stokes Law to account for the effect of walls. An empirical law is observed and partially justified by theory.

[edit] See also

• Notebooks, my attempt at a Wikipedia-like guide to my research interests. This includes:
  • basic concepts that could I teach in an introductory class (my notebooks reflect my particular way of thinking about them)
  • ideas of my own