Colloquia are held on Thursdays at 12:40pm in Room N304 of the Science and Engineering Center, unless otherwise noted. Pizza and soda are provided at 12:15. All are welcome.

**14-Jan** Dr. Harry Ringermacher, General Electric Global Research Center, *Why does the Hubble Classification of Spiral Galaxies Correlate Poorly with their Arm Angle-of-Pitch ?*

Since Hubble himself classified spiral galaxies according to arm sweep and bulge size (Sa, Sb and Sc types representing increasing sweep with decreasing bulge), one might naturally expect that the carefully measured angle-of-pitch of arms in spiral galaxies should correlate very well with Hubble Type. In fact, ever since Danvers plotted arm-pitch vs Hubble Type in 1942 to recent measurements by Kennicutt and Seigar, little or no correlation has been found. We prove there are two root causes: 1) misclassification of galaxies, and, most critically; (2) the assumption that “average pitch”, used by all astronomers in measuring galaxy pitch, is a good correlation parameter. We introduce a new formula that describes the natural pitch variation of all spiral galaxies dependent only on a single “pitch-parameter”. The pitch parameter of our formula, for the first time, produces an excellent correlation to Hubble Type in a study of 21 galaxies. Representative examples of fitted galaxies will be shown.

**7-Jan** Dr. Sarah Demers, Yale University, *Hunting for New Physics at the LHC*

CERN’s Large Hadron Collider (LHC) brings a new energy frontier to particle physics with the potential for discoveries of new physics. The thousands of physicists collaborating on the LHC experiments are in the final stages of preparation for the 2010 run and are analyzing the collisions that began in December, 2009. In this talk I will introduce the LHC and the ATLAS experiment and discuss some of the ways in which we hope to add to our understanding of the fundamental particles and forces in nature.

**4-Feb** Mark Kostuk *Using Chaotic Synchronization for Nonlinear State and Parameter Estimation: Theory and Applications from Bird-Brains to Barotropic Vorticity.*

Nonlinear systems abound in nature; unfortunately when studying such systems it is usually only possible to measure an incomplete portion of its dynamical state. Due to the possible existence of chaos in the dynamics, this presents the researcher with a problem if they have a representative model of the system and wish to use these measurements to uncover information about any of its unknown parameters. Alternatively, what if the exact underlying physics of the system are known and one would like to predict its future behavior; this is only possible if one has complete knowledge of its current state. In this talk I will discuss this general problem, why standard estimation techniques may fail, and how we use the phenomena of chaotic synchronization -in the form of an optimization problem- to gain a complete estimate of the state and any unknown parameters of a nonlinear system from incomplete data. I will demonstrate its successful application to a wide variety of nonlinear problems, from neuron models of the vocal center of the zebra finch to simplified fluid-dynamics models of the ocean. In addition, this method can be used to filter noisy measurements, and to provide a measure with which to choose between competing models. Crucially for large problems, such as weather forecasting, it is also possible to determine the number of measurements that are necessary for such estimations to be successful.

**11-Feb **Matt Martin ’06 RPI *Title TBA*

**4-Mar** Alex Handin ’10 *Senior Thesis Research Presentation*