Events at Physics |
Events on Tuesday, April 7th, 2009
- Chaos & Complex Systems Seminar
- A search for the simplest chaotic partial differential equation
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Charlie Brummitt, UW Department of Physics
- Abstract: A search for the simplest chaotic partial differential equation (PDE) concludes that the Kuramoto-Sivashinsky equation is likely the simplest chaotic PDE. We enumerate all of the equations with one quadratic or cubic nonlinearity that are "simpler" than the Kuramoto-Sivashinsky equation and test them for chaos, but none appear to be chaotic. Nevertheless, the search finds a strikingly simple PDE that is chaotic in the discrete limit of finitely many, coupled ordinary differential equations (ODEs). Analysis of this finite system indicates why the chaos vanishes in the limit of infinitely many ODEs.
- Astronomy Colloquium
- Massive Star Clusters in the Milky Way: The known and the known unkowns
- Time: 3:45 pm - 5:00 pm
- Place: 6515 Sterling Hall
- Speaker: Margaret Hanson, University of Cincinnati Physics Dept
- Abstract: The GLIMPSE survey of the Spitzer Space Telescope has provided unprecedented views to study the stellar population of the inner plane
of the Milky Way galaxy. Numerous groups have used this survey to identify new massive stellar cluster candidates. Follow up study of
these candidates indicate about half are true, bound clusters (theknown). The remaining are 'false positives': high density fields of unassociated stars, mimicking a true cluster. What is not so easy to estimate is the number of 'false negatives' from present surveys. These are clusters which exist, but are not detected in current searches (known unknowns). A cluster might not be detected because the core is not concentrated enough, it is highly extinguished, or there may be significant biases in the selection criteria used. In order to derive critical characteristics of the Milky Way's massive cluster population, such as the cluster mass function and cluster lifetimes, one must estimate the characteristics of stellar clusters that are presently missed by current surveys. Our group has taken on this daunting task to constrain the known unknowns via a sophisticated stellar cluster image simulation tool, MASSCLEAN, we've developed. I will present our preliminary efforts that make the first attempt to understand the biases of current searches, provide guidance on preparing more effective searches and our goal of ultimately estimating the characteristics of the massive cluster population of the entire Milky Way galaxy.
<br>
- Host: Prof John Gallagher