Events at Physics

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Events During the Week of April 2nd through April 9th, 2023

Monday, April 3rd, 2023

Academic Calendar
Students begin enrolling for Summer term courses according to their appointment times
Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, URL:
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Academic Calendar
Enrollment appointment times for Fall term assigned to students (throughout week)
Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, URL:
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Plasma Physics (Physics/ECE/NE 922) Seminar
Cosmic Ray Transport Theory in light of Milky Way Data
Time: 12:00 pm
Place: 2241 Chamberlin Hall
Speaker: Philipp Kempski, Princeton University
Abstract: Relativistic cosmic rays (CRs) may play an important role in the evolution of galaxies and clusters by driving galactic winds and heating diffuse gas. As a result, “CR feedback” has become a key ingredient in galaxy evolution models. However, a fundamental limitation of these models is that the nature of CR feedback is a very strong function of the assumed CR transport. Getting a better handle on the microphysics of CR propagation is therefore essential for understanding the macrophysics of CR feedback in galaxies. In this talk, I will discuss theoretical models of CR propagation and how CR spectra measured at Earth help us constrain their transport physics. I will show that existing theories of CR transport remain uncertain and are generally not in good agreement with local observations, which suggests that there may be a significant theoretical gap in our understanding of CR propagation.
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Tuesday, April 4th, 2023

Academic Calendar
Election Day In Wisconsin, including same-day registration
Time: 7:00 am
Abstract: Wisconsin Election for Supreme Court, Mayor, Alders, School Board, and Judges.. Statewide Office: Supreme Court. Local Offices: School Board, Mayor, Alders, and Judges. Go to to find your polling place, see what is on your ballot, and check your registration. If you are not registered at your current address, you can register at your assigned polling place on Election Day. See for information on registration, and voter ID. CONTACT: URL:
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Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
Constraints on axion-like polarization oscillations in the CMB with POLARBEAR
Time: 2:00 pm
Place: Meeting ID: 912 3071 4547 NOTE: All participants and hosts are now required to sign into a Zoom account prior to joining meetings hosted by UC Berkeley.
Speaker: Jacob Spisak, UCSD
Abstract: Very light pseudoscalar fields, often referred to as axions, are compelling dark matter candidates and can potentially be detected through their coupling to the electromagnetic field. Recently a novel detection technique using the cosmic microwave background (CMB) was proposed, which relies on the fact that the axion field oscillates at a frequency equal to its mass in appropriate units, leading to a time-dependent birefringence. For appropriate oscillation periods this allows the axion field at the telescope to be detected via the induced sinusoidal oscillation of the CMB linear polarization. I will discuss how we search for this effect using the POLARBEAR telescope and the constraints we place.

Zoom Meeting
Meeting ID: 912 3071 4547
NOTE: All participants and hosts are now required to sign into a Zoom account prior to joining meetings hosted by UC Berkeley.
Host: Baha Balantekin
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Wednesday, April 5th, 2023

Theory Seminar (High Energy/Cosmology)
Detecting Axion-Like Particles with Primordial Black Holes
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Tao Xu, Oklahoma U.
Abstract: Primordial black holes, which may constitute some or all of the dark matter today, offer a fascinating opportunity to explore the physics of our universe. One unique feature of primordial black holes is their Hawking radiation process, which can produce new particles that may be secluded from the Standard Model sector. Future gamma-ray experiments, such as the e-ASTROGAM and AMEGO telescopes, provide exciting prospects for detecting the Hawking radiation signal. In this talk, I will introduce the indirect detection search for primordial black holes and discuss how the gamma-ray spectra can be used to detect axion-like particles. By analyzing the gamma-ray energy distribution, we will see that the axion-like particle decay can modify the Hawking radiation spectrum relative to the Standard Model prediction. These observations will offer a new method to probe the parameters of axion-like particle mass and photon coupling.
Host: George Wojcik
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Thursday, April 6th, 2023

Astronomy Colloquium
Reverberation mapping the inner environments of AGN
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Yasaman Homayouni, Penn State University
Abstract: Reliable measurements of black hole mass and accretion-disk structure are critical to understanding the growth history of black holes and galaxy evolution over cosmic time. Beyond the local Universe, the gold standard for black hole mass and accretion-disk structure is reverberation mapping. I will present the latest results from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project and show how it has transformed our understanding of supermassive black holes by dramatically expanding the number of quasars with reliable mass and accretion structure at z > 0.3. I will also present a promising new method for reliably measuring mass and accretion structure of early black holes using direct accretion-disk structure measurement from future massive time-domain quasar studies with SDSS-V and LSST.
Host: Ke Zhang
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Friday, April 7th, 2023

Physics Department Colloquium
Cosmic Neutrinos at the Highest Energies
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Stephanie Wissel, Penn State
Abstract: Neutrinos are powerful probes of both astrophysics and fundamental particle physics at the highest energies. Weakly interacting and uncharged, they propagate undeterred and unabsorbed through the universe. In the last decade, we have observed a flux of high-energy (TeV-scale) neutrinos and through a multi-messenger lens — the combined observations of neutrinos and other messengers like photons — we are starting to see hints of energetic neutrino sources for the first time. At higher energies still, beyond the PeV scale, we can probe the most energetic sources of both neutrinos and cosmic rays, but current neutrino experiments become too small to observe a sizable flux. With long propagation lengths in both ice and air, radio detection offers an attractive solution to building the gigaton-scale detectors needed by allowing us to build sparse detectors sensitive to neutrinos over hundreds of kilometers. In this talk, I will review the landscape of current radio neutrino experiments, how they may lead to discoveries of neutrinos in a new energy band, and what they can reveal about the multi-messenger universe.
Host: Albrecht Karle
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