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Events on Friday, May 6th, 2022

Academic Calendar
Last class day
Time: 12:00 am
Abstract: *Note: actual end time may vary.*
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Academic Calendar
Final exam block
Time: 12:00 am
Abstract: *Note: actual end time may vary.* May 2-7, 2022
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Plasma Physics (Physics/ECE/NE 922) Seminar
Hot Atmospheres of Cool Stars: From Physical Conditions to Physical Processes
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Dr. Nancy S. Brickhouse, 2022 Distinguished Alumni Awardee, Senior Science Advisor Center for Astrophysics, Harvard University & Smithsonian
Abstract: Observations of cool star atmospheres show a broad range of physical conditions, with some stars having peak electron temperatures around a few MK like the Sun, while others show peaks above 20 MK. The X-ray luminosities of some quiescent coronae are as much as five orders of magnitude larger than the Sun’s. For the past three decades we have used ultraviolet and X-ray spectrometers to determine the physical conditions ---electron temperature, electron density, elemental abundances --- for a relatively small sample of cool stars (mostly the brightest). The youngest stars show a hot accretion shock in addition to an active corona, although the resolving powers of instruments to date are not sufficient to cleanly separate the two components. We are proposing Arcus, a NASA medium-scale explorer mission (MIDEX), to study structure and evolution in the Universe. Arcus will host a grating spectrometer of sufficient spectral resolution to go beyond the measurement of physical conditions to the exploration of the physical processes that produce the high energy emission.
Host: Prof. John Sarff
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Theory Seminar (High Energy/Cosmology)
String Solutions Without Supersymmetry
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Savdeep Sethi, University of Chicago
Abstract: The first part of the talk will briefly overview some no-go results on the string landscape. The second part of the talk will describe a way to potentially evade those no-go results by building non-classical string solutions. Specifically, I will outline a strategy to construct non-supersymmetric string solutions. I will also describe an explicit AdS solution where various swampland conjectures can be examined.
Host: George Wojcik
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Thesis Defense
Metasurfaces for Mid-Infrared Applications
Time: 3:00 pm
Place: 5310 Chamberlin Hall
Speaker: Gregory Holdman, Physics PhD Graduate Student
Abstract: Metasurfaces are thin, periodically patterned subwavelength strcuture that exhibit optical properties not present in their constituent materials. The modes and spectral features can be used for applications often considered impossible with conventional optics such as perfect reflectivity, strong mode confinement, and other goals. In this talk, I will present work on two types of metasurfaces operating in the mid-infared. The first project studies the thermal stability of a "laser sail", a metasurface designed to be both highly reflective and have low absorption. This sail could one day be used as a spacecraft. With a GW-scale laser, the radiation pressure could accelerate the surface to a signicant fraction of the speed of light. The second project studies the possibility of integrating graphene into a metasurface exhibiting extremely narrow spectral features in order to modulate the frequency of the mode in situ. Such a device would find applications in free-space optical communication and trace gas sensing.
Host: Victor Brar
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Physics Department Colloquium
The topology of tuning a non-Hermitian instrument: knots, braids, and exceptional points
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Jack Harris, Yale
Abstract: It may seem unlikely that rich mathematical structures still remain to be uncovered in small arrays of classical, linear oscillators. However, oscillators that combine non-reciprocal elements with loss (or gain) have provided a number of surprises in recent years. My talk will describe how these systems are naturally connected to braid groups, knot theory, and other topological structures. I will give a pedagogical introduction to this topic (with lots of pictures!) and will present measurements of these phenomena in a cavity optomechanical system.
Host: Shimon Kolkowitz
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