Berkeley Undergraduate Researchers

Hong Joo Ryoo, Former student;
John Hopkins graduate student, working with Sean Carroll

Received the prestigious NSF GRFP Graduate Fellowship for his PhD research proposal on the role of the three-body system in quantum computations of scattering observables.

The strong nuclear force governs the behavior of protons, neutrons, and other hadrons. Its underlying theory, Quantum Chromodynamics (QCD), describes interactions between quarks and gluons. At high energies, these inter- actions can be treated using perturbative techniques. However, at low energies, the theory becomes strongly coupled and non-perturbative, making it extremely difficult to extract predictions using traditional analytic methods. read more

Hong Joo Ryoo

Alex Wang, Former N3AS student;
University of Hong Kong, Physics Doctoral Program

Publication on arXiv.org
by Shengzhu Wang, Antón Baleato Lizancos, and José Luis Bernal:
Delensing CMB B-modes using galaxy surveys: the effect of galaxy bias and matter clustering non-linearities →

The B-mode of polarization of the CMB is a uniquely powerful probe of gravitational waves produced in the very early Universe. But searches for primordial B-mode anisotropies must contend with gravitational lensing, which induces late-time B-modes not associated with gravitational waves. These lensing B-modes can be removed — i.e., delensed — using observations of the E-modes and a proxy of the matter fluctuations along the line of sight that caused the deflections. read more

Nathan Olson, Former N3AS student

Honors thesis supervised by Prof. White:
Forecasting Constraints on Primordial Non-Gaussianity: A Tomographic Study with SPHEREx →

The measurement of primordial non-Gaussianity (PNG) is one of the key targets for upcoming cosmological surveys as detecting it would provide invaluable information about the physics of the early universe. read more

Catherine Welch, current INT UW/N3AS student

Publication on arXiv.org
by Mia Kumamoto and Catherine Welch:
Effects of Landau quantization on neutrino emission and absorption →

Some neutron stars known as magnetars possess very strong magnetic fields, with surface fields as large as and internal fields that are possibly stronger. Recent observations of the radio pulsar GLEAM-X J1627 suggest it may have a surface field as strong as . In the presence of a strong magnetic field, the energy levels of electrons and protons are quantized and the Direct Urca process allows neutron stars to cool rapidly, even at low density. For the case of magnetic fields , we find features in the emissivity due to energy quantization that are not captured by the frequently employed quasiclassical approximation… read more

Brandon Lem, Former N3AS student;
Michigan State University, Physics Doctoral Program

Publication accepted by Physical Review D
by Daniel J. Heimsoth , Brandon Lem, Anna M. Suliga, Calvin W. Johnson, A. Baha Balantekin et. al.:
Uncertainties on the EFT coupling limits for direct dark matter detection experiments stemming from uncertainties of target properties →

Direct detection experiments are still one of the most promising ways to unravel the nature of dark matter. To fully understand how well these experiments constrain the dark matter interactions with the Standard Model particles, all the uncertainties affecting the calculations must be known. It is especially critical now because direct detection experiments recently moved from placing limits only on the two elementary spin independent and spin dependent operators to the complete set of possible operators coupling dark matter and nuclei in nonrelativistic theory. In our work, we estimate the effect of nuclear configuration-interaction uncertainties on the exclusion bounds for one of the existing xenon-based experiments for all fifteen operators. We find that for operator number 13 the uncertainty on the coupling between the dark matter and nucleon can reach more than 50% for dark matter masses between 10 and 1000 GeV.

Santiago Rodriguez, Former student;
REU Coordinator, Space Sciences Laboratory

Publication on arXiv.org
by Lucas Johns and Santiago Rodriguez:
Collisional flavor pendula and neutrino quantum thermodynamics →

Neutrino flavor oscillation occurs because neutrinos emitted in a certain flavor are composed of a superposition of different neutrino mass states. In a dense enough environment, neutrino self-interactions synchronize flavor on large scales. In the two-flavor approximation, the resulting dynamics show similar behavior to the classical spinning top and inverted pendulum under some conditions. We explore the neutrino flavor pendulum with the addition of charged-current interactions and absorption/emission processes. In addition, investigating their effects in densities and time scales relevant to the isotropic and monochromatic emission of neutrinos from core-collapse supernovae, similar to neutrino the bulb model. We are able to identify the synchronized and bipolar modes of oscillation and constrain the polarization pendulum to a sphere and a circle in flavor space.

In 2023, Santiago has presented this research at the American Physical Society Far West Section, in San Diego.

Danial Baradaran, current N3AS student

Publication accepted by Physical Review D
by Danial Baradaran, Boryana Hadzhiyska, Martin J. White, and Noah Sailer:
Predicting the 21 cm field with a Hybrid Effective Field Theory approach →

A detection of the 21 cm signal can provide a unique window of opportunity for uncovering complex astrophysical phenomena at the epoch of reionization and placing constraints on cosmology at high redshifts, which are usually elusive to large-scale structure surveys. In this work, we provide a theoretical model based on a quadratic bias expansion capable of recovering the 21 cm power spectrum with high accuracy sufficient for upcoming ground-based radio interferometer experiments. In particular, we develop a hybrid effective field theory (HEFT) model in redshift space that leverages the accuracy of N-body simulations with the predictive power of analytical bias expansion models, and test it against the Thesan suite of radiative transfer hydrodynamical simulations… read more

Danial Baradaran

Malika Golshan, Former student;
SULI intern at LBL

Publication on arXiv.org
by Malika Golshian and Adrian Bayer:
Massive νs through the CNN lens: interpreting the field-level neutrino mass information in weak lensing →

Neutrinos, once thought to be massless according to the standard model, have proven otherwise due to the fascinating observation of neutrino flavor oscillations. In our research project, we take a unique approach by harnessing the power of machine learning to address a crucial question: Can computers aid in distinguishing between mass-bearing and massless neutrinos? By leveraging Convolutional Neural Networks (CNNs) on simulated weak lensing maps, our goal is to achieve a more accurate measurement of neutrino mass using cosmological methods.

I am deeply grateful to both my mentors. Vanessa, my initial mentor, provided me with a solid foundation and inspiration for this project. Adrian then became my mentor while transitioning to his postdoctoral position at Princeton. His unwavering dedication and expertise guided me through the intricacies of data analysis.

Malika Golshan