Axion-Assisted Electroweak Baryogenesis

We consider a hidden-valley gauge sector, G, with strong coupling scale Lambda~TeV and CP-violating topological parameter, theta, as well as a new axion degree of freedom which adjusts theta to near zero in the current universe. If the G-sector couples to the Standard Model via weak-scale states charged under both, then in the early universe it is possible for the CP-violation due to theta (which has not yet been adjusted to zero by the hidden axion) to feed in to the SM and drive efficient baryogenesis during the electroweak (EW) phase transition, independent of the effectively small amount of CP violation present in the SM itself. While current constraints on both the new axion and charged states are easily satisfied, we argue that the LHC can investigate the vast majority of parameter space where EW-baryogenesis is efficiently assisted, while the hidden axion should comprise a significant fraction of the dark matter density. In the supersymmetric version, the ``messenger'' matter communicating between the SM- and G-sectors naturally solves the little hierarchy problem of the MSSM. The connection of the hidden scale and masses of the ``quirk''-like messengers to the EW scale via the assisted electroweak baryogenesis mechanism provides a reason for such new hidden valley physics to lie at the weak scale.Comment: 22+1 pages, 3 figure

The Goldstini Variations

We study the 'goldstini' scenario of Cheung, Nomura, and Thaler, in which multiple independent supersymmetry (SUSY) breaking sectors lead to multiple would-be goldstinos, changing collider and cosmological phenomenology. In supergravity, potentially large corrections to the previous prediction of twice the gravitino mass for goldstini masses can arise when their scalar partners are stabilized far from the origin. Considerations arising from the complexity of realistic string compactifications indicate that many of the independent SUSY-breaking sectors should be conformally sequestered or situated in warped Randall-Sundrum-like throats, further changing the predicted goldstini masses. If the sequestered hidden sector is a metastable SUSY-breaking sector of the Intriligator-Seiberg-Shih (ISS) type then multiple goldstini can originate from within a single sector, along with many supplementary 'modulini', all with masses of order twice the gravitino mass. These fields can couple to the Supersymmetric Standard Model (SSM) via the 'Goldstino Portal'. Collider signatures involving SSM sparticle decays can provide strong evidence for warped-or-conformally-sequestered sectors, and of the ISS mechanism of SUSY breaking. Along with axions and photini, the Goldstino Portal gives another potential window to the hidden sectors of string theory.Comment: 30 pages, 3 figures; v2 minor changes, references adde

From Serra to Sancho: Music and Pageantry in the California Missions

The topic of conversation is Craig Russell\u27s book From Serra to Sancho: Music and Pageantry in the California Missions, published in 2009 by Oxford University Press. Craig is joined in conversation by Dan Krieger, professor emeritus and local historian.https://digitalcommons.calpoly.edu/convocpauth/1005/thumbnail.jp

Serra and Sacred Song at the Founding of California\u27s First Missions

No Abstract

Efficient holographic proofs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1996.Includes bibliographical references (p. 57-63).by Alexander Craig Russell.Ph.D

Residual stress measurement and structural integrity evaluation of SLM Ti-6Al-4V

Includes bibliographical references.The constant drive toward cleaner, more powerful and more efficient jet turbines in the aerospace industry has narrowed the gap between the aircraft performance envelope requirements and the material limits. The most advanced turbine engines are incredibly complex in design and the weight-saving requirements have placed significant pressure on material capabilities and the manufacturing systems. The next generation of manufacturing methodologies are being developed in the Additive Manufacturing (AM) arena from which Selective Laser Melting (SLM) has emerged as a promising candidate for producing highly complex components. Selective Laser Melting is a laser-based AM technique which builds 3-dimensionsal parts from CAD models in a layerwise fashion..

Doctor of Philosophy

dissertationEnzymatic biofuel cells use enzymes to catalyze electrochemical reactions, directly converting chemical energy to electricity. In this research, three enzymatic biofuel cell devices were created and a focus was placed on their electrode structure in order to improve current density, power density, and/or biocompatibility. The first device, a flow-through glucose biofuel cell, was fabricated from laser-cut poly(methyl methacrylate) and utilized a porous anode to increase current density through improved mass transfer. The maximum current and power density of 705 μA cm-2 and 146 μW cm-2 were among the highest for a flowing biofuel cell in the literature. The second device was a contact lens lactate biofuel cell fabricated in two iterations: one using buckypaper electrodes and the other with carbon paste electrodes, both electrode types being molded into a contact lens. These were the first reported examples of a biofuel cell on a contact lens. The first prototype suffered from poor stability as well as biocompatibility issues, but the second prototype was more stable and amenable to possibly being worn on the eye. The current and power density of the second prototype were, respectively, 22 ± 4 μA cm-2 and 2.4 ± 0.9 μW cm-2 at 0.18 ± 0.06 V. As the device was limited by its cathode, simulations were created to investigate two important factors: carbon nanotube (CNT) connectivity to the electrode and enzyme loading on the CNT surface. It was found that ca. 20% of the CNTs were connected to the electrode; furthermore, only 1-2% of the enzyme was wired to the electrode through the CNT network and roughly 20% of the CNT surfaces were in communication with enzyme. The ferrocene redox polymer/lactate oxidase enzyme-mediator anode system used on the second contact lens biofuel cell prototype performed very well, so it was also used in the third device-a self-powered lactate sensor. Coupled with a bilirubin oxidase cathode, the sensor had a detection range between 0-5 mM lactate, a sensitivity of 45 μA cm-2 mM-1, and a current and power density of 657 ± 17 μA cm-2, 122 ± 5 μW cm-2, respectively