Proton decay suppression in a supersymmetric SO(10) model

We propose a mechanism for sufficient suppression of dimension-5 operators for proton decay in a supersymmetric SO(10) model. This mechanism is analogue to the double seesaw mechanism in studying neutrino masses. Only an intermediate VEV instead of an intermediate scale is required so that gauge coupling unification is maintained. The VEV is generated by introducing an anomalous U(1) symmetry whose breaking is at higher scale. The proton decay amplitudes are suppressed by this VEV over the GUT scale. We use $\textbf{45+54}$ in breaking GUT symmetry. $\textbf{120}$ is included so that fermion sector is fully realistic. Assuming a minimal fine-tuning in the Higgs doublet sector, $\textrm{tan}\beta$ of order one is predicted.Comment: Several small corrections, 13 pages, no figur

Connection between proton decay suppression and seesaw mechanism in supersymmetric SO(10) models

We propose a mechanism to suppress proton decay induced by dimension-5 operators in a supersymmetric SO(10) model. Proton lifetime is directly connected with the intermediate vacuum expectation value which is responsible for the seesaw mechanism. The model shows many consistencies with the present theoretical results such as the components of the two Higgs doublets in the minimal supersymmetric standard model.Comment: 11 pages, no figure. Several minor correction

Essays on consumption choice

The dissertation consists of three essays that study consumption choices and their policy implications. The first chapter tests the life-cycle permanent income hypothesis via an experimental approach. University students are asked to provide their consumption choices in hypothetical circumstances. Background information such as their numerical and financial literacy are collected in the experiment. The data suggest that the subjects' consumption choices do not necessarily support the life-cycle permanent income hypothesis. The consumption levels chosen by some subjects vary greatly when they face the same total remaining lifetime resources, but different composition of these resources between net and human wealth. This consumption error varies across gender and is affected by the subjects' numerical and financial ability. The results have important implications for policymakers. In the second chapter a censored quadratic model is used to examine whether soda taxes affect consumption. Households that do and do not consume soda are taken into account. The results show that in states that have a higher soda than food tax or that have just increased the soda tax rates, households consume significantly less soda. Households that have more children and are located in areas with a small population assign significantly larger weight to soda in their total utility. The price elasticity of soda consumption is high. The unconditional price elasticity is larger than the conditional price elasticity, which is measured using households that do purchase soda. Also, the price elasticity for low-income households is greater than for high-income households. The results presented may be important to policymakers setting soda taxes to prevent obesity. Following the second chapter, a modified three-good censored utility model is used to examine if beer and wine taxes affect alcohol consumption. This study provides empirical estimates of price elasticities on beer and wine, which suggests that beer taxes may not be a good avenue for policymakers to consider in counteracting the serious consequence of alcohol abuse. However, wine taxes may be effective in reducing alcohol abuse, especially for low-income households

Proton decay in a supersymmetric SO(10) model with missing partner mechanism

The extended supersymmetric SO(10) model with missing partner mechanism is studied. An intermediate vacuum expectation value is incorporated which corresponds to the see-saw scale. Gauge coupling unification is not broken explicitly. Proton decay is found to satisfy the present experimental limits at the cost of fine-tuning some parameters.Comment: 14 pages; Several improvements, References adde

Galacto-forensic of LMC's orbital history as a probe for the dark matter potential in the outskirt of the Galaxy

The 3D observed velocities of the Large and Small Magellanic Clouds(LMC and SMC) provide an opportunity to probe the Galactic potential in the outskirt of the Galactic halo. Based on a canonical NFW model of the Galactic potential, Besla et al.(2007) reconstructed LMC and SMC's orbits and suggested that they are currently on their first perigalacticon passage about the Galaxy. Motivated by several recent revisions of the Sun's motion around the Galactic center, we re-examine the LMC's orbital history and show that it depends sensitively on the dark-matter's mass distribution beyond its present Galactic distance. We utilize results of numerical simulations to consider a range of possible structural and evolutionary models for the Galactic potentials. We find that within the theoretical and observational uncertainties, it is possible for the LMC to have had multiple perigalacticon passages on the Hubble time scale, especially if the Galactic circular velocity at the location of the Sun is greater than $\sim 228$km s$^{-1}$. Based on these models, a more accurate determination of the LMC's motion may be used to determine the dark matter distribution in the outskirt of the Galactic halo.Comment: 9 pages, 10 figures. Accepted for publication in Ap

Migration and Growth of Protoplanetary Embryos I: Convergence of Embryos in Protoplanetary Disks

According to the core-accretion scenario, planets form in protostellar disks through the condensation of dust, coagulation of planetesimals, and emergence of protoplanetary embryos. At a few AU in a minimum mass nebula, embryos' growth is quenched by dynamical isolation due to the depletion of planetesimals in their feeding zone. However, embryos with masses ($M_p$) in the range of a few Earth masses ($M_\oplus$) migrate toward a transition radius between the inner viscously heated and outer irradiated regions of their natal disk. Their limiting isolation mass increases with the planetesimals surface density. When $M_p > 10 M_\oplus$, embryos efficiently accrete gas and evolve into cores of gas giants. We use numerical simulation to show that, despite streamline interference, convergent embryos essentially retain the strength of non-interacting embryos' Lindblad and corotation torque by their natal disks. In disks with modest surface density (or equivalently accretion rates), embryos capture each other in their mutual mean motion resonances and form a convoy of super Earths. In more massive disks, they could overcome these resonant barriers to undergo repeated close encounters including cohesive collisions which enable the formation of massive cores.Comment: 9 pages, 6 figures, accepted for publication in Ap

Language modeling for automatic speech recognition in telehealth

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (January 11, 2007)Includes bibliographical references.Vita.Thesis (M.S.) University of Missouri-Columbia 2005.Dissertations, Academic -- University of Missouri--Columbia -- Computer science.Standard statistic n-gram language models play a critical and indispensable role in automatic speech recognition (ASR) applications. Though helpful to ASR, it suffers from a practical problem when lacking sufficient in-domain training data that come from same or similar sources as the task text. In order to improve language model performance, various datasets need to be used to supplement the in-domain training data. This thesis investigates effective approaches to language modeling for telehealth which consists of doctor-patient conversation speech in medical specialty domain. Efforts were made to collect and analyze various datasets for training as well as to find a method for modeling target language. By effectively defining word classes, and by combining class and word trigram language models trained separately from in-domain and out-of-domain datasets, large improvements were achieved in perplexity reduction over a baseline word trigram language model that simply interpolates word trigram models trained from different data sources