What is the thing behind me?

Andrew Wetzel

awetzel{at}berkeley{dot}edu

UC Berkeley
Astronomy Department
601 Campbell Hall
Berkeley, CA 94720
 
 

About Me

I am a graduate student working on my Ph.D. in Astrophysics at UC Berkeley. I am interested in theoretical cosmology and my adviser is Martin White.

Current Research Interests

Large-scale structure. Halo substructure and its connection to galaxy evolution. Formation, evolution, and merging of galaxies and galaxy clusters. Fueling of quasars/AGN.

Undergraduate Education

My undergraduate years were spent at Harvey Mudd College. I graduated in 2005 with a B.S. in physics and a minor in music.

My senior thesis research was in string theory with Vatche Sahakian.

Undergraduate Research

I spent the summer of 2005 with the Theoretical Astrophysics Group at Los Alamos National Laboratory, working with Daniel Holz on dark matter halo formation and merger histories.

During my senior year at Harvey Mudd College, I pursued research in string theory with Vatche Sahakian. One of the fundamental postulates of string theory is that the building blocks of the universe include objects extended in more than one spatial direction, such as strings and membranes. Strings can be closed, looping around on themselves, or open, in which case their ends are connected to dynamical “defects” in space or solitons known as D-branes. My research focused on the D-brane dielectric effect, a phenomenon arising in string theory analogous to the polarization of uniform charges in a background E&M field. In string theory, an isolated collection of D0 branes can be bound together with open strings ending on them. When placed in a background electric flux, the electric force will counteract the collapse of the branes, supporting a configuration in the shape of a “fuzzy” sphere since the D0 brane spatial coordinates become non-commutative. My project involved understanding whether this dielectric effect could arise from purely gravitational forces. We found that, barring a runaway potential in the non-Pauli matrix modes, a stable vacuum solution of the D0-brane potential could arise, permitting the desired fuzzy sphere. Here is my senior thesis. The first few pages are a good introduction to string theory. The rest is a good bit of fun math...

During summer 2004, I participated in the physics REU program at the University of Chicago, conducting research with Simon Swordy in high-energy experimental astrophysics. I helped in the development of TrICE, a “Track Imaging Cerenkov Experiment” telescope designed to measure cosmic rays in the PeV energy range. Previously, cosmic ray telescopes have observed the indirect Cerenkov light produced as the cosmic rays collide with atmospheric molecules. However, this method of detection is limited, as it does not allow for an accurate determination of the atomic number of the cosmic rays. Since TRICE requires high optical precision to distinguish the direct Cerenkov light of a cosmic ray from light produced by the subsequent atmospheric interactions, my goal was to discover whether the mechanical design tolerances of the telescope would allow for the needed precision. I developed a simulation to model the design parameters of the telescope and trace light rays as they propagate through and measure the size of the light image on the telescope’s detector. Here is a paper summarizing TrICE design and my research.

During summer 2003, I participated in Los Alamos National Laboratory’s Distinguished Students Program, conducting research with Nelson Hoffman in plasma physics applied to inertial confinement fusion (ICF). While controlled fusion research has been pursued for the last 50 years, the current development of the National Ignition Facility at Lawrence Livermore National Laboratory makes the prospect of break-even energy output possible. Furthermore, this research is crucial to our fundamental understanding of plasma dynamics. To create fusion conditions, spherical capsules containing deuterium-tritium fuel are imploded by an array of high-energy lasers, and the subsequent inertia propels the fuel to the high temperature-density required to induce fusion. To study this, we developed a simplified analog of an ICF implosion and analytically explored solutions of the governing nonlinear differential equations. We discovered that the reaction rate was minimized for a specific ratio of pressures inside to outside the capsule. I also studied high energy density plasmas in ICF using BUCKY, a finite-difference 1-D radiation hydrodynamics code, examining how the peak temperature of the plasma during implosion scaled with the radius of the capsule given specific initial conditions. Here is my paper on analyzing the non-linear differential equations governing our ICF model.

During summer 2002, I assisted in research of crop and soil science with Donald Tanaka at the USDA Northern Great Plains Research Laboratory. My work involved determining seed yield using various crop sequences across several growing seasons and understanding how these crop sequences affect soil composition. I measured soil and crop samples from the fields and in lab, with emphasis on chemical analysis, plant water use, and soil composition.

Dark Matters: an article on dark matter that I wrote for the Berkeley Science Review, a popular science journal focusing on Berkeley research.

The Large-Scale Structure of the Universe: slides from a public talk I gave to the Eastbay Astronomical Society during August 2008.