Upcoming Talks
This is a list of all upcoming talks for the next two weeks. Talks are from 3:454:45 p.m. in the Colloquium or Seminar Room, unless otherwise specified.

Oct12

A rigidity theorem for generalized odometersKostya MedynetsUnited States Naval AcademyOperator Algebras and Dynamics Seminars
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We show that generalized odometers are continuously orbit equivalent if and only if the sequences of finiteindex subgroups defining the systems are virtually isomorphic. For minimal equicontinuous $Z^d$systems the continuous orbit equivalence implies that the acting groups have finite index subgroups (having the same index) whose actions are piecewise conjugate. This result extends M.~Boyle's flipconjugacy theorem originally established for $\Z$actions. As a corollary we obtain a dynamical classification of the restricted isomorphism between generalized BunceDeddens $C*$algebras. We also show that the full group associated with a generalized odometer is amenable if and only if the acting group is amenable.

Oct14

Eric Mazur on "Assessment: the silent killer of learning"Sommer GentryUnited States Naval AcademyTime: 12:00 PMTeaching Seminar
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Presentation and discussion of "Assessment: the silent killer of learning," a lecture (available on YouTube) by physicist Eric Mazur of Harvard University. Mazur suggests that we should give up on the "ranking students" purpose of assessment because that can't be done fairly or reliably unless you ask only rote memorization questions. Instead, focus on the "give feedback" purpose of assessment, make feedback immediate, and ask authentic questions that are driven by the competencies we actually desire our students to have.

Oct14

PostQuantum CryptographyProf. Timothy HodgesUniversity of CincinnatiTime: 03:45 PMColloquium Series
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A review of the general situation and some discussion about the mathematical problems that arise.

Oct16

Wall to wall optimal transportProf. Charles DoeringUniversity of MichiganTime: 12:00 PMApplied Math Seminar
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How much stuff can be transported by an incompressible flow containing a specified amount of kinetic energy or enstrophy? We study this problem for steady 2D flows focusing on passive tracer transport between two parallel impermeable walls, employing the calculus of variations to find divergencefree velocity field with a given intensity budget that maximize transport between the walls. The maximizing velocity fields, i.e. the optimal flows, consist of arrays of (convectionlike) cells. Results are reported in terms of the Nusselt number Nu, the convective enhancement of transport normalized by the flowfree diffusive transport, and the Péclect number Pe, the dimensionless gauge of the strength of the flow. For both energy and enstrophy constraints we find that as Pe increases, the maximum transport is achieved by cells of decreasing aspect ratio. For each of the two flow intensity constraints, we also consider buoyancydriven flows the same constraint to see how scalings for transport reported in the literature compare with the absolute upper bounds. This work provides new insight into both steady optimal transport and turbulent transport, an increasingly lively area of research in geophysical, astrophysical, and engineering fluid dynamics. This work is joint with Gregory P. Chini (New Hampshire), Pedram Hassanzadeh (Harvard) and Andre Sousa (Michigan).

Oct19

Oct21