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Events During the Week of April 23rd through April 30th, 2023

Monday, April 24th, 2023

Plasma Physics (Physics/ECE/NE 922) Seminar
Dipole Traps for Non-neutral and Pair Plasma Studies
Time: 12:00 pm
Place: 2241 Chamberlin Hall
Speaker: Matthew Stoneking, Lawrence University
Abstract: The root source of the ubiquitous instabilities that lead to turbulence in magnetized plasmas can, in many cases, be traced to the asymmetry in the masses of the ions and electrons constituting the plasma. The APEX (A Positron-Electron eXPeriment) project aims to test predictions that a “pair plasma” composed of positively and negatively charged particles of equal mass should be remarkably stable to the micro-instabilities that seem universal to magnetized plasma. We are building a levitated dipole trap that uses a high-temperature superconducting coil along with a high-capacity accumulation system for positrons, to create the world’s first short Debye length magnetized electron-positron plasma. Experiments in support of this project are also underway to test the accessibility of long-lived thermal equilibrium states for pure electron plasma in a dipole field.
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Tuesday, April 25th, 2023

Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
Time: 2:00 pm
Place: Join Zoom Meeting
Speaker: Carla Fröhlich , NC State University
Host: Baha Balantekin
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Wednesday, April 26th, 2023

GREAT IDEAS Coffee Hour - Cancelled
Time: 12:15 pm - 1:15 pm
Abstract: GREAT IDEAS is cancelled for this week.

GREAT IDEAS stands for Group for Reading, Educating, And Talking about Inclusion, Diversity, Equity, & Advocacy in Science. It is a multimedia reading group dedicated to amplifying the experiences of underrepresented groups in science and academia in order to become better advocates for our peers. GREAT IDEAS is open to everyone (students/ faculty/ staff/ etc), and all are welcome and encouraged to engage with the material and contribute to the discussions. To keep a welcoming and safe environment for everyone, we ask that everyone understand and adhere to our community guidelines for the discussions. If you would like to submit an article for a future GREAT IDEAS discussion, you can do so on this form.
Host: GMaWiP and Climate and Diversity Committee (contact Jessie Thwaites or R. Sassella with questions)
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Theory Seminar (High Energy/Cosmology)
Status of negative coupling modifiers for extended Higgs sectors
Time: 1:00 pm - 2:30 pm
Place: Chamberlin 5280
Speaker: Carlos Henrique de Lima, Carleton University
Abstract: In this work, we study the status of negative coupling modifiers in extended Higgs sectors, focusing on the ratio of coupling modifiers that probes custodial symmetry violation λWZ=κW/κZ. Higgs sectors with multiplets larger than doublets are the only weakly coupled models that give tree-level modifications to λWZ, and we explore all such models allowed by the constraint from the ρ parameter and perturbative unitarity. This class of models has a custodial symmetry violating potential, while the vacuum configuration preserves the symmetry. We apply precision measurements from ATLAS and CMS and show that each data set can exclude a vast set of models with λWZ<0 at greater than 95\% confidence level. We give evidence that λWZ<0 is excluded in all weakly coupled models.
Host: George Wojcik
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Thursday, April 27th, 2023

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Landscape of CP Violation in Long-Baseline Neutrino Oscillation Experiments
Time: 2:30 pm - 3:30 pm
Place: CH4274 or
Speaker: Sanjib Kumar Agarwalla, Institute of Physics, Bhubaneswar/UW-Madison
Abstract: One of the fundamental properties of particles is their behavior under the CP (charge-parity) transformation and a violation of the CP symmetry may have an important connection to the observed baryon asymmetry in the Universe. In the lepton sector, the landmark discovery of non-zero 1-3 mixing angle by the Daya Bay experiment established the standard three-flavor oscillation picture of neutrinos and opened the door for a completely new and independent source of CP invariance violation in neutrino oscillation experiments. In the intensity frontier, the currently running and upcoming high-precision long-baseline neutrino oscillation experiments are the most promising avenues to observe a difference between neutrino and antineutrino transition probabilities - providing a smoking gun signature of leptonic CP violation. In this talk, after having an insightful discussion on the critical role of CP asymmetries in the appearance and disappearance channels, I will present in detail the capabilities of the next-generation long-baseline neutrino oscillation experiments DUNE and T2HK in isolation and combination to establish the leptonic CP violation at high confidence level. I will show how the possible complementarity among the on-axis DUNE and off-axis T2HK experiments can enhance the sensitivity towards leptonic CP violation by suppressing the parameter degeneracies.
Host: Francis Halzen
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Astronomy Colloquium
High-Resolution Far-Infrared Spectroscopy
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Darek Lis, Jet Propulsion Laboratory, California Institute of Technology
Abstract: The far-infrared spectral range includes rotational transitions of light hydride molecules, such as water, as well as key fine-structure lines of neutral and ionized atoms. I will present a recent SOFIA spectroscopic study of atomic oxygen on the line of sight toward Sagittarius B2, and its implications for the overall oxygen budget in the diffuse and translucent spiral arm clouds. I will also review isotopic measurements of the D/H ratio in cometary water, carried out over the past 35 years with ground-based and space facilities, and their implications for the origin of Earth’s oceans. I will discuss prospects for continuing such measurements with future NASA facilities.
Host: Ke Zhang
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Friday, April 28th, 2023

Physics Department Colloquium
On Ising’s Model of Ferromagnetism
Time: 3:30 pm - 6:00 pm
Place: 2241 Chamberlin Hall
Speaker: Peter Armitage, Johns Hopkins University
Abstract: The 1D Ising model is a classical model of great historical significance for both classical and quantum statistical mechanics. Developments in the understanding of the Ising model have fundamentally impacted our knowledge of thermodynamics, critical phenomena, magnetism, conformal quantum field theories, particle physics, and fractionalization in many-body systems. Despite the theoretical impact of the Ising model there have been very few good 1D realizations of it in actual real material systems. However, it has been pointed out recently, that the material CoNb2O6, has a number of features that may make it the most ideal realization we have of the Ising model in one dimension. In this talk I will discuss the surprisingly complex physics resulting in this simple model and review the history of “Ising’s model” from both a scientific and human perspective. In the modern context I will review recent experiments by my group and others on CoNb2O6. In particular I will show how low frequency light in the THz range gives unique insight into the tremendous zoo of phenomena arising in this simple model system. =========================================================================================================== [#1] C. M. Morris, R. Valdés Aguilar, A. Ghosh, S. M. Koohpayeh, J. Krizan, R. J. Cava, O. Tchernyshyov, T. M. McQueen, N. P. Armitage, "A hierarchy of bound states in the 1D ferromagnetic Ising chain CoNb2O6 investigated by high resolution time-domain terahertz spectroscopy", Phys. Rev. Lett. 112, 137403 (2014). [#2] C. M. Morris, Nisheeta Desai, J. Viirok, D. Hüvonen, U. Nagel, T. Rõõm, J. W. Krizan, R. J. Cava, T. M. McQueen, S. M. Koohpayeh, Ribhu K. Kaul, and N. P. Armitage, "Duality and domain wall dynamics in a twisted Kitaev chain", Nat. Phys. 17 832 (2021).
Host: Alex Levchenko
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