Colloquium Calendar

"The IceCube Neutrino Observatory and the Beginning of Neutrino Astrophysics"

The IceCube Neutrino Observatory is the world’s largest neutrino detector, instrumenting a cubic kilometer of ice at the geographic South Pole. IceCube was  designed to detect high-energy astrophysical neutrinos from potential cosmic ray acceleration sites such as active galactic nuclei, gamma ray bursts and supernova remnants. IceCube announced the detection of a diffuse flux of astrophysical neutrinos in 2013, including the highest energy neutrinos ever detected. In September 2018, IceCube observed a neutrino in coincidence with a flaring blazar. I will discuss the latest results from IceCube and discuss prospects for future upgrades and expansions of the detector.

Cancelled

"Phase Transformation and Interfacial Coupling in Heterostructures of Low-Dimensional Materials"

The rapid advances in low-dimensional materials of various crystalline symmetries and elemental compositions have generated rich functionalities. Artificially stacking or stitching dissimilar materials via construction of heterostructures further offers unprecedent potential for tailoring the properties of individual constituents and giving rise to exotic quantum phenomena. In this talk, I will first discuss how we utilize lateral heterostructures to induce phase transition in an inorganic transition metal dichalcogenide core-shell architecture and to unravel the microscopic process of insulator-to-metal transition in a correlated organic charge transfer complex system. I will then discuss the formation of new two-dimensional Sn phases enabled by interfacial coupling on hexagonal boron nitride monolayer on metal (h-BN/metal), which potentially provides a new avenue for engineering electronic and topological properties of 2D Sn.

"Explaining the Orbits of Ultra-Short-Period Planets Through Disk-Planet and Star-Planet Interactions"

Ultra-short-period planets (USPs) reside interior to the expected truncation radius for a typical T Tauri disk, requiring extra explanations for their current orbital locations beyond simple disk migration. In particular, once a planet migrates close to the disk truncation radius, Type I torques will go to zero or switch direction depending on the stellar and disk conditions, and the result is that the planet is expected to stop migration and become trapped. In this presentation, we explain how for suitable disk parameters, magnetically-driven sub-Keplerian gas flow in the inner disk can naturally counteract these effects and subsequently produce USPs at their observed orbital radii. The sub-Keplerian gas flow provides a headwind to small planets, providing a strong torque which can overcome the effects of outwards Type I migration in the inner disk. We also discuss how post-disk dispersal, stellar evolution can lead to a particularly intriguing geometry of system containing ultra-short period planets in high multiplicity systems where the ultra-short period planet and the outer planets exist in two different dynamical states. This has manifested in the observational data as a small number of stars hosting systems of tightly packed coplanar inner planets as well as an ultra-short period planet, where the orbit of the latter is misaligned relative to the mutual plane of the former.

"Dimensional Dancing"

I am a visual artist whose practice incorporates science and technology. I have collaborated with experts ranging from aerospace engineers to astrophysicists. I will present a number of projects that open innovative ways of seeing and thinking, from the creation of a neurodiverse AI entity to my current collaboration with KU professors Agnieszka Miedlar and Daniel Tapia Takaki (part of the Spencer Museum of Art’s Integrated Arts Research Initiative). Moving between locations, situations, perspectives and disciplines can disrupt existing understandings and open new paths for knowledge building, insight, and communication. Questions are generated by a shift in perspective, a step sideways into an unexpected conversation. Cross-disciplinary collaborations can operate as innovative structures, integrated and substantive to all participant’s respective fields. This talk will introduce methods and models of generative thinking. What new questions can be asked? What new discoveries will be made?

"40 Years of the Standard Model"

We'll discuss how the Standard Model of particle physics grew from its uncertain infancy to its formidable adulthood. After some nostalgia about the successes of the theory we'll attempt to take a clear-eyed look at its present status.

“Engineering Correlation and Topology in Two-Dimensional Moire Superlattices”

Van der Waals heterostructures of atomically thin crystals offer an exciting new platform to design novel electronic and optical properties. In this talk, I will describe a general approach to engineer correlated and topological physics using moire superlattice in two dimensional heterostructures. One example is the transition metal dichalcogenide moire superlattices, where a rich set of correlated insulator and generalized Wigner crystal states can be observed. The other example is the ABC trilayer graphene (TLG) and hexagonal boron nitride (hBN) moire superlattice, in which both the bandwidth and the topology of the electronic band can be controlled electrically. It allows us to realize many quantum phases, ranging from Mott insulator and superconductivity to orbital ferromagnetism and Chern insulator, all in a single device through electrostatic gating. 

“Italian delicacies served up in a neutron star crust”

The matter in the outermost layer, or “crust,” of a neutron star (the remnant of a supernova) is believed to host a variety of phases in which dense regions of nucleons are filled with voids of lower density. The presence of the phases, euphemistically referred to as “nuclear pasta” because of their resemblance to the shapes of lasagna, gnocchi, and spaghetti, may affect the emission of neutrinos, the primary mechanism by which the neutron star cools. In this talk, molecular dynamics and a set of topological and geometric descriptors (volume, area, mean curvature, and its Euler characteristic—a number that represents the phase’s topology) are used to accurately identify the pasta phases predicted by dynamical simulations, a labeling scheme that could be used to directly map the shape of a pasta phase to its effect on neutrino emission and neutron star cooling. Ref. https://link.springer.com/article/10.1007%2Fs11467-020-1004-2.