Events at Physics |
Events During the Week of December 1st through December 8th, 2024
Sunday, December 1st, 2024
- Academic Calendar
- Thanksgiving recess
- Abstract: *Note: actual end time may vary.*
Monday, December 2nd, 2024
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Tearing-mediated reconnection in magnetohydrodynamic poorly ionized plasmas
- Time: 12:05 pm - 1:00 pm
- Place: 1610 Engineering Hall
- Speaker: Elizabeth Tolman, Flatiron Institute
- Abstract: Many plasma environments, such as star-forming molecular clouds, the solar chromosphere, and the diffuse interstellar medium, are poorly ionized and threaded by dynamically important magnetic fields. We use theory and computation to study tearing-mediated reconnection in such poorly ionized systems. In this work, we focus on the onset and linear evolution of this process. In poorly ionized plasmas, magnetic nulls on scales below vA,n0/𝜈 ni0, with vA,n0 the neutral Alfvén speed and 𝜈 ni0 the neutral–ion collision frequency, will self-sharpen via ambipolar diffusion. This sharpening occurs at an increasing rate, inhibiting the onset of reconnection. Once the current sheet becomes thin enough, however, ions decouple from neutrals and the thinning of the CS slows, allowing the onset of tearing in a time of order 𝜈 ni0 . We find that the wavelength and growth rate of the mode that first disrupts the forming sheet can be predicted from a poorly ionized tearing dispersion relation; as the plasma recombination rate increases and ionization fraction decreases, the growth rate becomes an increasing multiple of 𝜈 ni0 and the wavelength becomes a decreasing fraction of vA,n0/𝜈 ni0. After reconnection onsets in a current sheet, the system enters a nonlinear phase characterized by a stochastic plasmoid chain, but the characteristics of this chain differ from those of a stochastic plasmoid chain in fully ionized plasma. The plasma in the plasmoids is characterized by an ionization fraction which is much larger than that of the background plasma. Our results could have significant implications for understanding of several important astrophysical processes, including the transport of cosmic rays in the interstellar medium.
- Host: Vladimir Zhdankin, John Sarff
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Advanced Fuel Oscillating Fusion Reactor
- Time: 4:00 pm - 5:00 pm
- Place: 106 Engineering Research Building (access via Materials Science Building)
- Speaker: Richard Nebel, Tibbar Plasma Technologies, Inc
- Abstract: A new type of fusion reactor is presented. This device produces fusion by the collision of two oscillating plasma rings. This is a linear device similar in shape to a magnetic mirror with direct energy converters on its ends. Analysis shows that this system can create net energy gain, even with an advanced fuel like p-11B. This advanced fuel eliminates neutrons and thus eliminates radioactive byproducts. It is compact and can provide terrestrial power and power for space propulsion.
- Host: John Sarff
Tuesday, December 3rd, 2024
- Graduate Program Event
- Virtual Open House for underrepresented Physics-PhD Applicants
- Time: 10:00 am - 11:00 am
- Place:
- Abstract: Applicants to the UW-Madison Physics PhD program from diverse or underrepresented populations are invited to join faculty, staff and current students for a virtual open house to learn about admissions, PhD program requirements and life in Madison. We'll have plenty of time for Q&A.
- Host: Sharon Kahn
- Climate & Diversity
- Current Issues in Physics: TedTalk: How Black Queer Culture Shaped History - Channing Gerard Joseph
- Time: 12:00 pm - 1:00 pm
- Place: Chamberlin 5310 or over Zoom
- Abstract: The Climate and Diversity Committee is planning to host their regular Current Issues in Physics Discussion 12/3/24 at 12pm, in Chamberlin 5310 or over Zoom. This video is an excellent way to discuss the intersectionality of lived experiences.
- Preliminary Exam
- Investigating Potential Time Dependence in the Cosmic Ray Anisotropy
- Time: 2:00 pm - 4:00 pm
- Place: 5280 CH or
- Speaker: Perri Zilberman, Physics PhD Graduate Student
- Abstract: The cosmic ray flux has been found to be nearly isotropic on the sky, however a significant and robust anisotropy has been found by IceCube as well as a number of other experiments. This anisotropy is likely in part caused by cosmic rays interacting with the magnetic field of the heliosphere. The heliosphere is dynamic, largely due to changes in solar activity. This suggests that the Cosmic Ray Anisotropy should similarly vary in time, in step with the heliosphere, though there is not a consistent picture of how such a time variation would present itself observationally. Considering this, we present a model-independent method to test for time variation in the Cosmic Ray Anisotropy. This method is then validated using a sample of data from the IceCube Neutrino Observatory.
- Host: Albrecht Karle
- Wisconsin Quantum Institute
- Quantum Coffee Hour
- Time: 3:00 pm - 4:00 pm
- Place: Rm.5294, Chamberlin Hall
- Abstract: Please join us for the WQI Quantum Coffee today at 3PM in the Physics Faculty Lounge (Rm.5294 in Chamberlin Hall). This series, which takes place approximately every other Tuesday, aims to foster a casual and collaborative atmosphere where faculty, post-docs, students, and anyone with an interest in quantum information sciences can come together. There will be coffee and treats.
Wednesday, December 4th, 2024
- Preliminary Exam
- Protocol for robust quantum networks
- Time: 2:00 pm - 4:00 pm
- Place: 5280 Chamberlin Hall or
- Speaker: Omar Khaled Nagib Abdelhakim Mohamed, Physics PhD Graduate Student
- Abstract: Quantum networks consist of quantum nodes (e.g., atomic qubits) connected by remote entanglement. For scalable quantum networks, it is essential to engineer interactions between remote atomic qubits. This is typically achieved through two-qubit gates between atomic qubits in cavities and flying photons. Previous schemes have been sensitive to experimental imperfections, with fidelities limited to the range of 75–80%. I propose an atom-photon CZ gate that utilizes doubly degenerate ground and excited state energy levels to mediate the atom-light interaction. The setup consists of a cavity and a Mach-Zehnder interferometer. The gate operates by converting error-inducing photons into losses, making the scheme less sensitive to errors compared to previous schemes.
I will also discuss my research progress on two additional projects. The first project proposes the use of Grover's algorithm in a cavity to efficiently prepare entangled states of many qubits. The second project is a mathematical and numerical method that enables fast simulation of open quantum systems through the use of generalized inverses. - Host: Mark Saffman
- Theory Seminar (High Energy/Cosmology)
- Quantum gravity as a lattice model
- Time: 4:00 pm - 5:30 pm
- Place: Chamberlin 5280
- Speaker: Monica Jinwoo Kang, UPenn, Philadelphia
- Abstract: As it is essential to have a quantum theory of gravity for understanding the fundamental principles underlying black hole thermodynamics, constructing and studying quantum gravity has been a constant desire in modern theoretical physics. I will construct the explicit framework to build a formalism to construct a lattice model of space time and quantum gravity. I will present explicit toy models of quantum gravity with this framework. I will utilize quantum gravity in the semi-classical regime by taking quantum field theory as its framework and demonstrate that the notion of entanglement, which is central in the quantum nature of physics, plays an important role in studying quantum gravity.
- Host: Gary Shiu
Thursday, December 5th, 2024
- R. G. Herb Condensed Matter Seminar
- Special Seminar by Graduate Students
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Abigail Shearrow (UW-Madison) and Steffen Bollmann (MPISSR-Stuttgart )
- Abstract: First Talk (30min)
Abigail Shearrow:
"Noise and efficiency of a Josephson mm-wave detector"
Second Talk (30min)
Steffen Bollmann
"Topological Green's function zeros in an exactly solved model and beyond"
- Host: Alex Levchenko
- Astronomy Colloquium
- New Insights Into Novae
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Elias Aydi, Texas Tech University
- Abstract: Novae are panchromatic transients triggered by a thermonuclear runaway on the surfaces of white dwarf stars in interacting binaries. Our understanding of how novae are powered has been altered with the Fermi gamma-ray telescope establishing novae as bright GeV gamma-ray sources and thus a new class of particle accelerators in our Galaxy. This unexpected discovery underscores the complexity of novae and their value as laboratories for studying shocks and particle acceleration. In this talk I will highlight our ongoing multi-wavelength/multi-messenger efforts aimed at understanding how shocks work in novae. These efforts can help us probe critical but poorly understood physical processes, such as common envelope interaction, super-Eddington luminosities, particle acceleration efficiency, and dust formation around explosive transients, and are essential for a better understanding of other shock-powered transients in the Universe such as supernovae, stellar mergers, and tidal disruption events.
- Host: Melinda Soares-Furtado
- Astronomy Colloquium
- New Insights Into Novae
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Elias Aydi, Texas Tech University
- Abstract: Novae are panchromatic transients triggered by a thermonuclear runaway on the surfaces of white dwarf stars in interacting binaries. Our understanding of how novae are powered has been altered with the Fermi gamma-ray telescope establishing novae as bright GeV gamma-ray sources and thus a new class of particle accelerators in our Galaxy. This unexpected discovery underscores the complexity of novae and their value as laboratories for studying shocks and particle acceleration. In this talk I will highlight our ongoing multi-wavelength/multi-messenger efforts aimed at understanding how shocks work in novae. These efforts can help us probe critical but poorly understood physical processes, such as common envelope interaction, super-Eddington luminosities, particle acceleration efficiency, and dust formation around explosive transients, and are essential for a better understanding of other shock-powered transients in the Universe such as supernovae, stellar mergers, and tidal disruption events.
- Host: Melinda Soares-Furtado
Friday, December 6th, 2024
- Preliminary Exam
- X-Ray Fluorescence Imaging of Early Print
- Time: 10:00 am - 12:00 pm
- Place: Sterling Hall, Room B343
- Speaker: Minhal Gardezi, Physics PhD Graduate Student
- Abstract: Print is one of humanity’s most impactful technologies, yet much of its origins remain unclear, particularly surrounding the earliest instances of moveable metal type print. While there is documentation of Korean printers using metal type as early as 1234, none of the metal types used for these earliest prints have been preserved and their metal compositions remain unknown. Even fewer technical details are known about the first European metal type press invented by Johannes Gutenberg in the mid 15th century, despite its major role in launching the Renaissance period in Europe by revolutionizing Western information dissemination. Working in collaboration with an interdisciplinary team of scholars, technical personnel, and scientists, my work aims to fill in the gaps in knowledge surrounding early print technology through X-ray fluorescence (XRF) imaging of early printed documents. XRF scans of around 50 early print specimens from across Korea and Europe (including an early 15th century bound Korean folio and fragments of an original 42-line Gutenberg Bible) as well as 7 pre-Gutenberg Arabic block prints revealed clear metal content only in the documents printed using metal type. Through collaboration with print scholars, I obtained and produced controlled test prints made using metal types with known alloys and nonmetal inks. XRF scans of these test prints confirmed the leaching of metals from the types into the paper. Here I will present my findings and propose XRF imaging as a compelling research technique for ascertaining whether a historical document was printed using metal type and, if so, determining the metal type alloy. My work adds valuable information to scholarly studies comparing early print technologies that aims to determine whether print may have arrived in Europe from Asia.
- Host: Uwe Bergmann
- Preliminary Exam
- Topological Data Analysis for Cosmology
- Time: 2:00 pm - 3:30 pm
- Place: 5310 Chamberlin
- Speaker: Jacky Yip, Physics PhD Graduate Student
- Abstract: The shape of data contains a great deal of information. We apply persistent homology, a tool in topological data analysis, to build summary statistics from the topology of the large-scale structure of the universe at late times. Employing the Quijote simulations, we perform a Fisher forecast and obtain constraints on cosmological parameters and primordial non-Gaussianity amplitudes. The result is that our topological summary is generally more informative compared with conventional 2-point and 3-point statistics, and combining the approaches allows for more constraining power due to breaking parameter degeneracies. We also demonstrate a pipeline for inference.
- Host: Gary Shiu