(1:00-1:15)
[42 - 180-269]: Searching for Carbon in the Intergalactic Medium
James Haworth†★, Reza Monadi†Department of Physics, †Frost Support, ★Speaker
Since the 1960s, quasars have been used as ‘probes’ of the intergalactic medium, by utilizing spectroscopy techniques to visually inspect spectra for atomic absorption lines. In recent years, a number of spectroscopic deep space surveys, including the survey being conducted by the Dark Energy Spectroscopic Instrument, have produced a wealth of quasar spectra, necessitating automated methods to search for intergalactic medium absorbers. In our research, we use data from the Dark Energy Spectroscopic Instrument to detect carbon IV absorption in the intergalactic medium, informing us about the redshift and density of these absorbers. Our Bayesian approach informs our detections from previously assembled carbon IV catalogs. We then validate our code’s effectiveness by injecting and recovering simulated absorption lines in real spectra. When complete, we believe our catalog will represent the largest collection of known metal absorption systems to date. This catalog will serve to better inform theories about early stellar and galactic evolution. |
(1:15-1:30)
[43 - 180-269]: The role of local winds and a semi-persistent coastal front on the diurnal heat budget in an upwelling bay
April Thibodeau1†★§, Ryan Walter1★, Piero Mazzini2, Thomas Connolly3, Christopher Edwards4, Ian Robbins51 Department of Physics, 2 Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA, USA, 3 Moss Landing Marine Laboratories, San José State University, Moss Landing, CA, USA, 4 Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA, 5 Department of Biological Sciences, †Frost Support, §Santa Rosa Creek Foundation Support, ★Speaker
Coastal embayments in nearshore upwelling systems (“upwelling bays”) play a disproportionately large role in regional oceanography. In these systems, local diurnal wind forcing and thermal gradients associated with an upwelling shadow front that forms between warmer sheltered waters inside the bay and colder recently upwelled waters outside the bay strongly influence local temperature dynamics. Despite their importance to local ecosystems, there are no long-term studies that assess the heat budget inside upwelling bays. In this study, we analyzed approximately two years of water temperature throughout the water column using an autonomous profiler in a small upwelling bay in central California (San Luis Obispo Bay). We coupled these measurements with local meteorological data and in-situ temperature measurements made outside the bay to investigate how local diurnal wind forcing and the presence of the upwelling shadow front modify the diurnal heat budget inside the bay. Over the study period, strong seasonality in regional upwelling coincided with changes in local wind forcing, front strength (bulk temperature difference between inside and outside the bay), and temperature structure, from which we identified various forcing regimes to quantify the diurnal heat budget. During the non-upwelling season when the front was largely absent, the heat budget was primarily a balance between changes in heat content and surface heat fluxes, regardless of local wind forcing strength. This was also the primary balance during the upwelling season when local winds were weak. In contrast, during the upwelling season when the upwelling shadow front was persistent and the local winds were strong, increasing front strength led to increasingly large residual heat fluxes, which were interpreted to be due to advection (advective fluxes not calculated directly). These results highlight the importance of both local wind forcing and frontal intensity on the heat budget inside the upwelling bay, with significant implications. |
(1:30-1:45)
[44 - 180-269]: The Dance of Stars: Megamaser Galaxies and their Supermassive Black Holes
Chandrasekhar Kappagantula1★, Nico Winkel2, Raymond Remigio3, Tommaso Treu3, Vardha Bennert11 Department of Physics, 2 , 3 UCLA, ★Speaker
Many galaxies are known to contain supermassive black holes (SMBHs) in their centers. Studying the relationship between the SMBH and its host galaxy gives insights into the origin and evolution of galaxies. Of particular interest are Active Galactic Nuclei (AGNs) – galaxies with SMBHs that “accrete” (gravitationally attract) dust and gas, emitting large amounts of light. Under the AGN unification model, it is theorized that the different types of AGNs we see – type-1 vs. type-2 – are actually the same phenomenon, differing only by the angle from which we view the AGN. While measuring the mass of SMBHs is relatively straightforward for type-1 AGNs, it is possible for type-2 AGNs only in megamaser galaxies. However, megamaser galaxies seem to be outliers on the correlation between the mass of the SMBH and the stellar kinematics of the host galaxy followed tightly by type-1 AGNs and quiescent galaxies. Existing spectroscopic data is based on apertures – for the most precise stellar kinematics measurements, we here use 3D spectroscopy of 21 megamaser galaxies. Our results will show if the offset can be explained by observational bias. If the offset exists, it questions the AGN unified model, implying an underlying physical difference between type-1 and type-2 AGN. |
(1:45-2:00)
[45 - 180-269]: Investigation of Topological Features in Lepton-Number Violating Seesaw Extensions
Sanjay Sreejith★, Thomas GutierrezDepartment of Physics, ★Speaker
The vacuum manifold of the Standard Model electroweak sector has a trivial homotopy group, and no topologically protected monopoles. We investigate how lepton-number–violating seesaw extensions of the electroweak theory can modify the topology of the vacuum manifold. In particular, we study how the symmetry-breaking patterns associated with such extensions introduce non-trivial homotopy groups that support topological defects such as monopoles or cosmic strings. |
(2:00-2:15)
[46 - 180-269]: Influence of guest atom on framework in type-I silicon clathrates
William Cranney-Fee1†★, Zoe Jackson Delos Angeles2, Matthew Jenkins1†, Michael Baitinger3, Matthew Beekman11 Department of Physics, 2 Department of Materials Engineering, 3 Max-Planck-Institute for Chemical Physics for Solids, †Frost Support, ★Speaker
To date, several hundred distinct compositions of intermetallic or structurally related inorganic clathrates have been experimentally prepared, with as many crystallographic studies published. Nonetheless, a comprehensive collective analysis and interpretation of structural trends with composition have yet to be reported. As a first step toward this goal, we present results from a collective analysis of crystallographic data for type-I silicon clathrates, $\text{M}_{8-x}\text{Si}_{46}$ (M = Na, Sr, Ba, K, Rb, and Cs), from the available literature to elucidate how the framework responds to alkali and alkaline-earth metal guest atoms of different size. The analysis focuses on trends in unit cell size, atomic positions, and bond lengths, which reflect the response of the framework to guest atoms. Rather than simple rigid expansion, the analysis shows the polyhedral framework cages change shape in a systematic way to accommodate guest atoms of larger size. The details of this response of the framework to guest size in clathrate-I with pure silicon frameworks will be discussed. |
(2:15-2:30)
[47 - 180-269]: CUPID’s Irreducible Background: Pileup Rejection through a Deep Learning Lens
C.J. DuHamel★, Thomas GutierrezDepartment of Physics, ★Speaker
The CUORE (Cryogenic Underground Observatory for Rare Events) experiment is searching for neutrinoless double beta decay ($0\nu\beta\beta$) at the Gran Sasso National Laboratory. Neutrinos are currently treated as Dirac fermions, particles distinct from their antiparticle, making this decay forbidden in the Standard Model. However, observation of neutrinoless double beta decay would indicate neutrinos are Majorana fermions, particles that are their own antiparticle. CUORE currently sets the best lower limit on the half-life for neutrinoless double beta decay in Tellurium-130. CUPID (CUORE Upgrade with Particle Identification) is an experiment in development that will look for neutrinoless double beta decay in Molybdenum-100 at much higher sensitivity.
However, the transition to Molybdenum results in a higher rate of two-neutrino double beta decay ($2\nu\beta\beta$), significantly increasing the likelihood of “pileup events”. Pileup occurs when two events are detected by the same detector near simultaneously. Due to the relatively slow response time of the detectors, this may result in a detector response that appears to have the same energy as neutrinoless double beta decay. Thus, we need a reliable way of rejecting these events, for which we can turn to deep neural network. While previous attempts convolve over the image in one dimension, we aim to investigate the phase portrait of the pulse (the time derivative of the amplitude versus the amplitude) as a more informative data representation for pileup rejection, utilizing a two dimensional convolutional neural network (CNN) instead. |
(2:30-2:45)
[48 - 180-269]: Transformer Network Representations of Quantum Many-Body Ground States
Spandan Suthar†★, Ian Powell†Department of Physics, †Frost Support, ★Speaker
Neural networks are often used in quantum physics research as tools for representing quantum states. An effective application is in conjunction with variational methods, as trial wave functions with the capacity to express complex features such as cross-site correlations at system sizes where classical methods tend to fall short. Transformer neural networks represent a subset of these variational models, with a particular affinity for capturing relationships across large sequences of tokens and demonstrating an ability to generalize the skills they are optimized for well beyond their initial training curricula. This talk aims to convey the main principles that make this approach effective for representing many-body systems, including token representations of site information, importance sampling routines, observable estimation, and methods for recovering wave functions from a transformer's native sampling probabilities. |
(2:45-3:00)
[49 - 180-269]: Investigation of Ester Amide Ylidenenorbornadiene Ring Opening Polymerization and Fragmentation
Sonia Patil★, Hannah Gamsaragan†, Simran Singh†, Daniel Bercovici†Department of Chemistry and Biochemistry, †Frost Support, ★Speaker
Ester amide ylidenenorbornadienes (EA-YNDs) can be used to form dynamic covalent linkages that are capable of tunable fragmentation via retro-[4+2]cycloaddition. EA-YND dimers were prepared by a [4+2] cycloaddition between sec-butanol fulvenes and ester amide alkyne dimers. A model EA-YND dimer with hexyl amide and methyl ester subtituents was used to perform a ring-opening polymerization of ?-caprolactone to yield a polymer with a target molecular weight of 10 kDa. The polymer was reacted with propanethiol to yield a mixture of diastereomers, similarly capable of fragmentation. The polymer post-fragmentation has a molecular weight of half its original. Characterization and fragmentation of this polymer were monitored via NMR and GPC. Our group has extensively studied the stereoelectronic effects on the fragmentation kinetics of EA-YND dynamic covalent linkages breaking apart, and will apply this to our polymer system.
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