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DTSTART;TZID=America/New_York:20231110T160000
DTEND;TZID=America/New_York:20231110T170000
DTSTAMP:20231108T144126Z
CREATED:20231106T025239Z
LAST-MODIFIED:20231108T144126Z
UID:292-1699632000-1699635600@pages.vassar.edu
SUMMARY:(Colloquium) Hung Tong\, The University of Alabama
DESCRIPTION:Colloquium Talk\nHung Tong\, The University of Alabama\nFriday November 10\, 2023 at 4PM\nRocky  312 \nTitle: Robust and Flexible Model-Based Clustering for Incomplete Data \nAbstract: Model-based clustering is an important class of cluster analysis that aims to produce smaller groups of similar observations in a data set by means of finite mixture models. Since real data often contain outliers\, exhibit skewness\, and come in the form of partially observed records\, developing robust and flexible model-based clustering methods for incomplete data has been a particularly active research area in recent years. Herein\, we introduce the contaminated normal mixture for robust clustering as well as our newly developed framework for fitting it to data sets with values missing at random. Regarding flexible clustering\, we discuss our work in extending special and limiting cases of the generalized hyperbolic mixture to both complete and incomplete data sets. All these mixture models are implemented and available in the R package MixtureMissing\, offering a wide range of model-based clustering options to address various data challenges of researchers.
URL:https://pages.vassar.edu/mathstats/event/colloquium-hung-tong-the-university-of-alabama/
CATEGORIES:Colloquium
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231106T160000
DTEND;TZID=America/New_York:20231106T170000
DTSTAMP:20231106T025139Z
CREATED:20231106T024908Z
LAST-MODIFIED:20231106T025139Z
UID:290-1699286400-1699290000@pages.vassar.edu
SUMMARY:(Colloquium) Katherine Brumberg\, University of Pennsylvania
DESCRIPTION:Colloquium Talk\nKatherine Brumberg\, University of Pennsylvania\, Wharton School\nMonday November 6\, 2023 at 4PM\nRocky  312 \nTitle: Optimal Stratification to Address Selection Bias in Observational Studies \nAbstract: Randomized controlled trials are the gold standard for determining a treatment effect. However\, they are oftentimes too costly\, infeasible\, or unethical to carry out. In such situations\, we turn to observational studies\, where the treatment assignment is not randomized. This results in selection bias\, leading to incomparable treatment and control groups. One of the most common techniques to address this is propensity score stratification\, where we form strata that contain both treated and control individuals who look similar initially so that we can calculate a treatment effect within each stratum. However\, propensity score stratification may leave residual imbalances in the covariate distributions between the treated and control groups. Our new technique of optimal refinement addresses this by splitting each propensity score stratum in two in such a way that optimizes the resulting covariate balance. \n\nIn this talk\, we will assume no background knowledge\, starting with a brief overview of the foundational ideas of randomized controlled trials\, observational studies\, stratification\, propensity scores\, and standardized mean differences.  We will then move to discussing our new technique of optimal refinement. We will start by carefully defining the objective as an integer program. Because solving integer programs is often computationally intractable\, we will use randomized rounding\, an approximation algorithm\, to obtain a provably good solution. We will look at the performance of this method both in simulations and via a real-world example studying the effect of right heart catheterization on 30-day mortality.
URL:https://pages.vassar.edu/mathstats/event/colloquium-katherine-brumberg-university-of-pennsylvania/
LOCATION:Rockefeller Hall 312
CATEGORIES:Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231102T150000
DTEND;TZID=America/New_York:20231102T160000
DTSTAMP:20231026T135616Z
CREATED:20230926T031404Z
LAST-MODIFIED:20231026T135616Z
UID:156-1698937200-1698940800@pages.vassar.edu
SUMMARY:(Colloquium) Karen Parshall\, University of Virginia
DESCRIPTION:Colloquium Talk\nProfessor Karen Parshall\, University of Virginia\nThursday November 2nd\, 2023 at 3PM\nRocky 300 \n \nTitle: Growing Research-Level Mathematics in 1930s America: An Historical Paradox \nAbstract: World War I had marked a break in business as usual within the American mathematical research community. In its aftermath\, there was a stirring sense of entering into “a new era in the development of our science.”  And then the stock market crashed. Would it be possible in such newly straitened times to sustain into the 1930s the momentum that American mathematicians had managed to build in the 1920s? This talk will explore the contours of an answer to that question.
URL:https://pages.vassar.edu/mathstats/event/colloquium-talk-3/
CATEGORIES:Colloquium
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DTSTART;TZID=America/New_York:20231026T150000
DTEND;TZID=America/New_York:20231026T160000
DTSTAMP:20231025T185628Z
CREATED:20230926T031308Z
LAST-MODIFIED:20231025T185628Z
UID:154-1698332400-1698336000@pages.vassar.edu
SUMMARY:(Colloquium) Joe Kraisler\, Amherst College
DESCRIPTION:Colloquium Talk\nProfessor Joe Kraisler\, Amherst College\nThursday October 26\, 2023 at 3PM\nRocky 300 \n \nTitle: Topological Insulators and the SSH Model \nAbstract: Electronic band theory was one of the early 20th century achievements of quantum mechanics and placed solids into three categories: conductors\, semiconductors\, and insulators. However\, starting in the 1980s with the discovery of the Quantum Hall Effect\, a new phase of matter known as Topological Insulators (TIs) were theorized and eventually realized. These materials act as insulators in the interior\, or bulk\, while allowing electrons to freely move along the boundary\, or edge\, of the material. Additionally\, there is a relationship between the a) number of states which exist on the boundary and b) a property of the interior which is protected under small defects. This relationship is often referred to as the Bulk-Edge Correspondence. \nWe will study the simplest example of a 1-dimensional topological insulator\, the SSH (Su-Schrieffer-Heeger) model of polyacetylene\, and prove the bulk edge correspondence for this particular system. No previous physics knowledge is required.
URL:https://pages.vassar.edu/mathstats/event/colloquium-talk-2/
CATEGORIES:Colloquium
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231003T160000
DTEND;TZID=America/New_York:20231003T170000
DTSTAMP:20230928T013632Z
CREATED:20230925T163351Z
LAST-MODIFIED:20230928T013632Z
UID:119-1696348800-1696352400@pages.vassar.edu
SUMMARY:(Colloquium) Colin Adams\, Williams College
DESCRIPTION:Join us for our first colloquium talk of the semester by Professor Colin Adams of Williams College on Tuesday October 3 at 4PM in Rocky 203. \n \nBlown Away: What Knot to do When Sailing \nColin Adams\nWilliams College \nBeing a tale of adventure on the high seas involving great risk to the tale teller\, and how an understanding of the mathematical theory of knots saved his bacon. No nautical or mathematical background assumed! \nTuesday\, October 3rd\, 4pm\nRocky 203
URL:https://pages.vassar.edu/mathstats/event/colloquium-talk/
LOCATION:Rockefeller Hall 203
CATEGORIES:Colloquium
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