Undergraduate Honors Program - Physics and Astronomy Department
http://hdl.handle.net/1803/569
Mon, 05 Dec 2022 22:27:24 GMT2022-12-05T22:27:24ZUndergraduate Honors Program - Physics and Astronomy Departmenthttps://ir.vanderbilt.edu:443/bitstream/id/270f3e51-2d99-4590-acca-3343e251c176/
http://hdl.handle.net/1803/569
Expected Host Galaxy Properties of PTA Detectable Massive Black Hole Binaries
http://hdl.handle.net/1803/16997
Expected Host Galaxy Properties of PTA Detectable Massive Black Hole Binaries
Cella, Katharine
Massive black hole binaries (MBHB) produce gravitational waves (GW) that will be detectable with pulsar timing arrays within the next few years. We determine the properties of the host galaxies of MBHB at the time they are producing detectable GW. The population of MBHB systems we evaluate is from the Illustris cosmological simulations taken in tandem with post processing semi-analytic models of environmental factors in the evolution of binaries. Upon evolving to the frequency regime detectable by pulsar timing arrays, we calculate the detection probability of each system using a variety of different values for red and white noise. We average over multiple realizations of the universe by re-sampling the host galaxy properties using a kernel density estimator to approximate the statistical distributions of the universe. Excitingly, we find that detectable systems have host galaxies that are clearly distinct from the overall population. With conservative noise factors, we found that stellar metallicity, for example, peaks at approximately twice solar metallicity as opposed to the total population of galaxies which peaks at approximately solar metallicity. Additionally, the most detectable systems are brighter and more red in color than the overall population. These results can be used to develop effective search strategies for identifying host galaxies and electromagnetic counterparts following GW detections.
Mon, 06 Dec 2021 00:00:00 GMThttp://hdl.handle.net/1803/169972021-12-06T00:00:00ZAnalytic Solutions of Two Electrons in Harmonic Confinement in an Optical Cavity
http://hdl.handle.net/1803/16996
Analytic Solutions of Two Electrons in Harmonic Confinement in an Optical Cavity
Huang, Chenhang
The possibility to control quantum systems with photons has stimulated
recent interest in the study of quantum optical systems. While
simple classical quantum systems admit well-known solutions, analysis
of light-coupling quantum regimes remains lacking. In this work,
we obtain analytic solutions for a light-coupling electron pair in harmonic
confinement in a cavity by separating center-of-mass (CM) and
relative motions. The CM part can be calculated in closed form or
by exact diagonalization of the Hamiltonian, and the relative part is
quasi-exactly solvable. We analyze the 2D results produced by the
exact diagonalization method and reach conclusions on the effects of
different system parameters. We also present 1D numerical simulations
by Stochastic Variational Method (SVM) using Explicitly Correlated
Gaussian (ECG) bases, which agree with our analysis in 2D. Our analytic
solutions may provide a valuable calibration point for simulations
in the quantum optical regime.
Vanderbilt physics honor thesis of Chenhang Huang, in partial fulfillment of the requirements for the honor degree of
Bachelor of Arts in Physics. Advisor: Kalman Varga.
Wed, 01 Dec 2021 00:00:00 GMThttp://hdl.handle.net/1803/169962021-12-01T00:00:00ZAxionlike Dark Energy and Particle Decay in theFuture of the Accelerating Universe
http://hdl.handle.net/1803/16488
Axionlike Dark Energy and Particle Decay in theFuture of the Accelerating Universe
Norton, Cameron
The 1998 discovery that the universe was accelerating in its expansion has yet to be explained
theoretically, meriting the continual theoretical and observational study of this phenomena.
In this thesis, we undergo a phenomenological study of the cosmological implications of this
“dark energy” in two different ways.
In the first part of this thesis, we examine the cosmological evolution of ultralight axionlike (ULA) scalar fields with potentials of the form V (φ) = m2f
2
[1 − cos (φ/f)]2
, with
particular emphasis on the deviation in their behavior from the corresponding small-φ powerlaw approximations to these potentials: V (φ) ∝ φ
2n
. We show that in the slow-roll regime,
when φ˙2/2 V (φ), the full ULA potentials yield a more interesting range of possibilities for
quintessence than do the corresponding power law approximations. For rapidly oscillating
scalar fields, we derive the equation of state parameter and oscillation frequency for the ULA
potentials and show how they deviate from the corresponding power-law values. We derive
an analytic expression for the equation of state parameter that better approximates the ULA
value than does the pure power-law approximation.
In the second part, we study particle decay in the future of the accelerating universe. We
generalize the result that in a cosmological constant dominated universe, the decay of matter
into relativistic particles can never cause radiation to once again dominate over matter. We
study both models of dark energy comprised of quintessence and cosmologies ending in a “big
rip” in this context.
Fri, 30 Apr 2021 00:00:00 GMThttp://hdl.handle.net/1803/164882021-04-30T00:00:00ZA web-based application of the Cellular Force Inference Toolkit (CellFIT)
http://hdl.handle.net/1803/10366
A web-based application of the Cellular Force Inference Toolkit (CellFIT)
Xu, Xiaojia
Given an image of an epithelial cell sheet, CellFIT can infer cellular forces by segmenting the image into individual cells, constructing equilibrium equations for the points where cells meet at triple junctions, and finding a least-squares solution for the tensions at cell-cell interfaces. Similarly, cellular pressures can be estimated by constructing Laplace equations that relate the edge tensions, curvatures and cellular pressure differences. Despite these capabilities, the accessibility of CellFIT to scientists of all backgrounds is not yet optimized. We will present an updated web-based application of CellFIT that allows users to access the software from a browser. The updated version includes improved error handling and the implementation of additional functionality for reading and processing image stacks. Application of the web-based CellFIT to time-resolved image stacks of wound healing in Drosophila epithelia demonstrates spatial and temporal variations in cellular forces as the wounds close.
Thu, 18 Apr 2019 00:00:00 GMThttp://hdl.handle.net/1803/103662019-04-18T00:00:00Z