Kinematics of Circumgalactic Gas

Crystal Martin
University of California, Santa Barbara
November 27, 2018

Most of the baryons associated with galaxy halos reside in the
circumgalactic medium. A significant fraction of the mass is at
temperatures well below the halo virial temperature.  What holds
the cool CGM up?  I will present new measurements of the kinematics
of circumgalactic gas.  The data show that much of the low-ionization
CGM rotates in the same direction as the galactic disk, suggesting
substantial centrifugal support.  Disturbances from galactic winds

Homotopical effects of k-dilation

Larry Guth
Massachusetts Institute of Technology
November 27, 2018
Back in the 70s, Gromov started to study the relationship between the Lipschitz constant of a map (also called the dilation) and its topology. The Lipschitz constant describes the local geometric features of the map, and the problem is to understand how it relates to the global geometric features of the map -- a bit like trying to understand the relationship between the curvature of a Riemannian manifold and its topology.

Monotone Circuit Lower Bounds from Resolution

Mika Goos
Member, School of Mathematics
November 27, 2018
For any unsatisfiable CNF formula F that is hard to refute in the Resolution proof system, we show that a gadget-composed version of F is hard to refute in any proof system whose lines are computed by efficient communication protocols---or, equivalently, that a monotone function associated with F has large monotone circuit complexity. As an application, we show that a monotone variant of XOR-SAT has exponential monotone circuit complexity, which improves qualitatively on the monotone vs. non-monotone separation of Tardos (1988).

Classical Verification of Quantum Computations

Urmila Mahadev
UC Berkeley
November 26, 2018
We present the first protocol allowing a classical computer to interactively verify the result of an efficient quantum computation. We achieve this by constructing a measurement protocol, which allows a classical string to serve as a commitment to a quantum state. The protocol forces the prover to behave as follows: the prover must construct an n qubit state of his choice, non-adaptively measure each qubit in the Hadamard or standard basis as directed by the verifier, and report the measurement results to the verifier.

The min-max width of unit volume three-spheres

Lucas Ambrozio
University of Warwick; Member, School of Mathematics
November 20, 2018
The (Simon-Smith) min-max width of a Riemannian three dimensional sphere is a geometric invariant that measures the tightest way, in terms of area, of sweeping out the three-sphere by two-spheres. In this talk, we will explore the properties of this geometric invariant as a functional on the space of unit volume
metrics.

This is joint work with Rafael Montezuma.