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Events During the Week of January 30th through February 6th, 2022

Monday, January 31st, 2022

Public Research Seminar
"Building a habitable planet: an emerging view of volatile chemistry in planet-forming disks"
Time: 9:00 am
Place: Wisconsin Institutes for Discovery, Orchard Room
Speaker: Jennifer Bergner, University of Chicago
Abstract: Planets form within disks composed of gas, ice, and dust in orbit around young stars. The distribution of volatiles (gas+ice) within these disks profoundly impacts both the chemical and physical outcomes of planet formation-- including the delivery of prebiotic building blocks to new worlds. In this talk, I will highlight our recent advances in disentangling how organic complexity is built up during the star and planet formation sequence, the role of interstellar inheritance in setting disk volatile compositions, and the distinctive volatile chemistry at play during the planet formation epoch. These insights are gained by combining telescope observations, ice chemistry experiments, and disk chemistry simulations, each of which contributes an indispensable piece of the puzzle. Taken together, we are assembling a more complete picture of the chemical environment which regulates the formation, composition, and potential habitability of planetesimals and planets. Web Link:
Host: Hannah Zanowski, Assistant Professor Department of Atmospheric and Oceanic Sciences
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Tuesday, February 1st, 2022

Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
Properties of the neutron star crust: Quantifying and correlating uncertainties with improved nuclear physics.
Time: 2:00 pm
Speaker: Jerome Margueron, CNRS/IN2P3
Abstract: The understanding of neutron star (NS) properties from fundamental nuclear physics inputs requires the precise determination of the relation between nuclear physics uncertainties and dense matter predictions. This became possible recently due to advances in theoretical efforts to predict properties of nuclei and dense nuclear matter, and advances in experimental nuclear physics that are now providing more stringent constraints. In addition, recent observations of NS radii by NICER and tidal deformabilities by the LIGO-Virgo collaboration have also reached the accuracy to better constrain the dense matter equation of state (EOS). These developments motivate the construction of models that can provide a unified description of the EOS of the crust and the core. For this purpose we have employed the well-known compressible liquid-drop model to correlate uncertainties associated with neutron star crust properties with theoretical estimates of the uncertainties associated with the EOS of homogeneous neutron and nuclear matter. We also quantify the impact due to the finite size of nuclear clusters in the crust. We find for instance that the finite-size effects impact the crust composition, but have a negligible effect on the net isospin asymmetry in the crust, which is largely determined by the bulk properties. We also discuss the link between low density neutron matter predictions from microscopic nuclear approaches and the crust properties. Finally by adopting a unified model to describe the crust and the core of NSs and disregarding phase transition in dense matter, we tighten the correlation between their global properties such as their mass-radius relationship, moment of inertia, crust thickness, and tidal deformability with uncertainties associated with the nuclear Hamiltonians.
Host: Baha Balantekin
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Wednesday, February 2nd, 2022

Physics ∩ ML Seminar
Equivariant Neural Fields: A Roadmap Towards Generalizable Neural Representation and Inference
Time: 11:00 am
Place: Chamberlin 5280 (Zoom link also available for online participants who signed up on our mailing list)
Speaker: Ge Yang, IAIFI and MIT
Abstract: Generalization is a central problem in deep learning research because it directly affects how much data and compute it costs to achieve good performance. In other words better generalization makes better performance more accessible. In this talk, we begin by looking at a few interesting situations where modern neural networks fail to generalize. We discuss the components responsible for these failures, and ways to fix them. Then we introduce continuous neural representation and neural fields as a unifying theme. As part of the roadmap, I will lay down key technical milestones, and specific applications in control, reinforcement learning, and scene understanding.
Host: Gary Shiu
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Thursday, February 3rd, 2022

Public Research Seminar
Life in the Light: Photochemical Insights Towards Life as a Planetary Phenomenon
Time: 9:00 am
Place: Wisconsin Institute of Discovery, Orchard Room
Speaker: Dr. Sukrit Ranjan, Northwestern University
Abstract: Advances in origins-of-life chemistry are transforming our understanding of how life emerged on Earth, while upcoming space missions and telescopes offer the prospect of detecting life on other worlds. Fundamental to both quests is interaction of UV radiation with molecular systems (photochemistry). Photochemistry controls the chemical context for the origin of life on Earth and influences the molecular signposts with which we hope to detect life elsewhere. I will share photochemical work which refines our understanding of early Earth environments, and demonstrate how such understanding enables assessment and improvement of theories of origins-of-life chemistry. I will discuss photochemical efforts to elucidate potential atmospheric biosignatures of life on other worlds, and show how the search for life on other worlds may enable tests of theories of the origin of life. In sum, I will review theoretical, experimental, and observational work towards understanding the origin and distribution of life in the universe through the lens of photochemistry.

Zoon Link:
Host: Coco Zhang, UW Astronomy Department
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R. G. Herb Condensed Matter Seminar
Time: 10:00 am
Speaker: Andrei Derevianko, University of Nevada, Reno
Abstract: CANCELLED.
Host: Mark Saffman
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Recent Results from MicroBooNE Addressing the MiniBooNE Anomaly Using Deep-Learning-Based Reconstruction
Time: 2:30 pm
Place: Chamberlin 4274 (or
Speaker: Lauren Yates, Fermilab
Abstract: The MicroBooNE experiment uses a liquid argon time projection chamber (LArTPC) located on-axis in the Booster Neutrino Beam at Fermilab to perform a wide variety of physics measurements. Recently, MicroBooNE released its first results addressing the nature of the anomalous excess of low-energy interactions previously observed by the MiniBooNE collaboration. This seminar will focus on an approach that isolates electron neutrino interactions consistent with the kinematics of charged-current quasi-elastic (CCQE) events. The topology of such signal events has a final state with one electron and one proton (1e1p). Multiple novel techniques are employed to identify a 1e1p final state, including particle identification that uses two methods of deep-learning-based LArTPC image analysis and event selection using a boosted decision-tree ensemble trained to recognize two-body scattering kinematics.
Host: Lu Lu
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R. G. Herb Condensed Matter Seminar
Time: 4:00 pm
Place: Cancelled
Speaker: Justyna Zwolak, NIST
Abstract: Cancelled
Host: Mark Eriksson
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Friday, February 4th, 2022

Theory Seminar (High Energy/Cosmology)
Maximizing Direct Detection with HYPER Dark Matter
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Robert Mcgehee, University of Michigan
Abstract: In this talk, we estimate the maximum direct detection cross section for sub-GeV dark matter scattering off nucleons. For dark matter masses in the range of 10 keV − 100 MeV, cross sections greater than 10^(−36) - 10^(−30) cm^2 seem implausible. We introduce a dark matter candidate which realizes this maximum cross section: HighlY interactive ParticlE Relics (HYPERs). After HYPERs freeze-in, a dark sector phase transition decreases the mass of the mediator which connects HYPERs to the visible sector. This increases the HYPER’s direct detection cross section, but in such a way as to leave the HYPER’s abundance unaffected and avoid conflict with measurements of Big Bang Nucleosynthesis and the Cosmic Microwave Background. HYPERs present a benchmark for direct detection experiments in a parameter space with few known dark matter models.
Host: George Wojcik
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Physics Department Colloquium
Quantum computing with neutral Yb atoms
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Jeff Thompson, Princeton
Abstract: Quantum computing with neutral atoms has progressed rapidly in recent years, combining large system sizes, flexible and dynamic connectivity, and quickly improving gate fidelities. The pioneering work in this field has been implemented using alkali atoms, primarily rubidium and cesium. However, divalent, alkaline-earth-like atoms such as ytterbium offer significant technical advantages. In this talk, I will present our progress on quantum computing using 171-Yb atoms, including high-fidelity imaging, nuclear spin qubits with extremely long coherence times, and two-qubit gates on nuclear spins using Rydberg states [1,2]. I will also discuss several unexpected benefits of alkaline-earth-atoms: an extremely robust and power-efficient local gate addressing scheme [3], and a novel approach to quantum error correction called “erasure conversion”, which has the potential to implement the surface code with a threshold exceeding 4%, using the unique level structure of 171-Yb to convert spontaneous emission events into erasure errors [4]. Time permitting, I will also discuss a new project to implement very high fidelity quantum computing and simulation using circular Rydberg states with 100-second lifetimes [5]. [1] S. Saskin et al, Phys. Rev. Lett. 122, 143002 (2019). [2] A. P. Burgers et al, arXiv:2110.06902 (2021). [3] S. Ma, A. P. Burgers, et al, arXiv: 2112.06799 (2021). [4] Y. Wu, et al: arXiv:2201.03540 (2022). [5] S. R. Cohen et al, PRX Quantum 2, 030322 (2021).
Host: Shimon Kolkowitz
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