## Colloquium

##### Tuesday, October 28, 2014 at 3:30p.m.

**Charles R. Doering** (*Depts. of Physics, Mathematics and Center for Study of Complex Systems, University of Michigan, Ann Arbor*)

**Abstract:**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 divergence-free 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 (convection like) cells. Results are reported in terms of the Nusselt number Nu, the convective enhancement of transport normalized by the flow-free diffusive transport, and the Péclet 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 buoyancy-driven flows the same constraint to see how the 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 is joint work with Pedram Hassanzadeh (Berkeley/Harvard) and Gregory ...

### Monday, 27 October 2014

#### Topology Seminar

*The higher Morita category of E_n-algebras*at 2:30p.m. in VinH 570

**Rune Haugseng**(

*Max-Planck Institute for Mathematics*)

I will discuss a construction of a higher category of E_n-algebras and iterated bimodules, generalizing the classical bicategory of algebras and bimodules. This leads to ...
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#### Automorphic Forms and Number Theory

### Tuesday, 28 October 2014

#### Climate Seminar

*Understanding early agricultural impacts on climate with dynamical systems*at 11:15a.m. in VinH 570

**Alice Nadeau**(

*U of M Mathematics Department*)

#### Combinatorics Study Group

#### Colloquium

*Wall to wall optimal transport*at 3:30p.m. in VinH 16

**Charles R. Doering**(

*Depts. of Physics, Mathematics and Center for Study of Complex Systems, University of Michigan, Ann Arbor*)

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 ...
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#### Geometric Analysis Learning Seminar

### Wednesday, 29 October 2014

#### Student Stochastic Seminar

*An Introduction to Noise Sensitivity*at 2:00p.m. in VinH 570

**Zach Hamaker**(

*IMA*)

We will introduce the concept of noise sensitivity and outline some of its connections to percolation. In doing so, we will use several tools from ...
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#### Algebraic Geometry

*Virtual invariants on Quot schemes over del Pezzo surfaces*at 2:30p.m. in Vincent Hall 313

**Daniel Schultheis**(

*U of M*)

. The Quot scheme over a smooth projective curve C offers a compactification of the space of maps from C to a Grassmannian. Numerous mathematicians ...
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#### PDE Seminar

*On the quasiconvergence property of solutions of reaction-diffusion equations on R*at 3:35p.m. in VinH 206

**Professor Peter Polacik**(

*University of Minnesota*)

We examine bounded solutions of semilinear parabolic equations on the real line. Such a solution u(.,t) is called quasiconvergent if it approaches a set of ...
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### Thursday, 30 October 2014

#### Math Club Seminar

*Ramsey Theory*at 12:20p.m. in VinH 570

**Christian Gaetz**(

*University of Minnesota*)

Ramsey’s Theorem states that if the edges of a sufficiently large complete graph are 2-colored, there will exist a complete monochromatic sub-graph of the desired ...
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#### Algebra Reading Seminar

### Friday, 31 October 2014

#### Combinatorics Problem Session

*All are welcome to pose a short combinatorics problem, or discuss problems posed by others*at 2:30p.m. in VinH 570

**to be announced**

#### Probability Seminar

*Asymptotic results for the longest common subsequence problem*at 2:30p.m. in VinH 207

**Umit Islak**(

*U of M Mathematics Department*)

Let (X_k)_{k \geq 1} and (Y_k)_{k\geq1} be two independent sequences of i.i.d. random variables having the same law and taking their values in a finite ...
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#### Lie Theory Seminar

#### Combinatorics Seminar

*Toric arrangements -- towards setting up a combinatorial theory*at 3:35p.m. in VinH 570

**Emanuele Delucchi**(

*University of Bremen*)

Recent work of De Concini, Procesi and Vergne on vector partition functions gave a new impulse to the study of toric arrangements from an algebraic, ...
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#### MCFAM Seminar

*Yield Curves and Eventual Total Positivity*at 5:30p.m. in VinH 16

**Dr. Carlos Tolmasky**(

*Institute of Mathematics and Its Applications (IMA) - University of Minnesota*)

Principal components analysis has become widely used in a variety of fields. In finance and, more specifically, in the theory of interest rate derivative modeling, ...
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