Ultracold polarized Fermi gas at intermediate temperatures

We consider non-zero temperature properties of the polarized two-component Fermi gas. We point out that stable polarized paired states which are more stable than their phase separated counterparts with unpolarized superfluid region can exist below the critical temperature. We also solve the system behavior in a trap using the local density approximation and find gradually increasing polarization in the center of the system as the temperature is increased. However, in the strongly interacting region the central polarization increases most rapidly close to the mean-field critical temperature, which is known to be substantially higher than the critical temperature for superfluidity. This indicates that most of the phase separation occurs in the fluctuation region prior to superfluidity and that the polarization in the actual superfluid is modest.Comment: Final published versio

Changes in Behavior, Movement, and Home Ranges of Largemouth Bass Following Large-scale Hydrilla Removal in Lake Seminole, Georgia

About 1,200 ha of hydrilla ( Hydrilla verticillata L.f. Royle) was eliminated in the Spring Creek embayment of Lake Seminole, Georgia, using a drip-delivery application of fluridone (1- methyl-3-phenyl-5-[3-(trifluoromethl) phenyl]-4(1H)-pyridinone) in 2000 and 2001. Two groups of 15 and 20 largemouth bass (Micropterus salmoides Lacepede) were implanted with 400-day radio tags in February 2000 and 2001 to determine changes in movement and behavior before and after hydrilla reduction.(PDF contains 8 pages.

Essays on Debt in Macroeconomics

My dissertation consists of three chapters, where the common theme among them is debt and saving. My work contributes to our understanding of how debt markets function for entrepreneurs, large corporations and households. The first chapter studies how entrepreneurs used personal borrowing to fund their businesses during the Great Recession. One of the defining characteristics of this period was a “credit crunch” during which the supply of credit dropped for all borrowers. I show that changes in the finances of entrepreneurs between 2007 and 2009 are consistent with entrepreneurs using personal assets to secure lending for their businesses and overcome this credit crunch. In particular, I find that home equity loan balances increased by 10%, despite a 12% drop in the value of aggregate housing stock. Entrepreneurs were responsible for 76% of the increase in home equity loan balances, while they only represent 13% of the population. In the second chapter, I study the use of credit ratings by large corporations in the bond market. Over the last 25 years, there has been a drastic change in the distribution of corporate bond ratings: between 1985 and 2010 the number of firms issuing AAA or AA-rated debt dropped by 70%, while the number of firms issuing debt with lower ratings increased. I propose a mechanism whereby investors learn about firms through credit ratings and publicly available financial information and develop a model that incorporates this mechanism such that firms must devote resources to improving their rating. Under general conditions, the number of high-rated firms decreases in response to an increase in public signal accuracy. The third chapter explores the role of financial market access on household consumption inequality. The standard macroeconomic models of consumption and saving with stochastic income processes have failed to match the rise in consumption inequality between 1980 and 2004. I present a model with idiosyncratic earnings risk and endogenous market segmentation between incomplete and complete markets for financial assets. This model improves upon the qualitative predictions regarding between-group and within-group consumption inequality of a standard incomplete markets model and a standard complete markets model with limited commitment

The 2S(+) - 2P separation in KO

The 2S(+) - 2P separation in KO is investigated using large basis sets and high levels of correlation treatment. Relativistic effects are included at the Dirac-Fock level and reduce the separation only slightly. The basis set superposition error is considered in detail. On the basis of these calculations, our best estimate places the 2p sub 3/2 state about 200 cm(exp -1) above the ground 2 sigma(+) state in agreement with our previous estimate

Climate change adaptation planning for an internationally important wetland, the Muir–Byenup System Ramsar Site in south-west Australia

Wetlands, already declining worldwide because of human activities, are at increasing risk from climate change. Despite the Ramsar Convention requirement to maintain the ecological character of wetlands listed as internationally important, there is little guidance for wetland managers to actually do this, let alone plan for and implement adaptation to climate change. This study developed a checklist for planning climate change adaptation and used it to consider adaptation options for the Muir–Byenup System Ramsar site in Australia. Under climate change the site will be subject to future warming and drying, affecting hydrology, bird breeding and feeding, vegetation, peat and threatened species. Fire and wetland acidification are likely to increase. The study found that planning for climate change adaptation had not been widely undertaken for Ramsar sites and, where it had, managers mainly planned information gathering activities and ‘no regrets’ actions rather than innovative or transformative approaches. New management approaches and policy settings that encompass the dynamic nature of wetlands are needed because maintaining wetlands in their current state will be difficult under climate change. The development and sharing of targeted information and training for wetland managers and stakeholders could facilitate a better understanding and uptake of adaptation at wetlands

All-electron molecular Dirac-Hartree-Fock calculations: The group 4 tetrahydrides CH4, SiH4, GeH4, SnH4 and PbH4

A basis-set-expansion Dirac-Hartree-Fock program for molecules is described. Bond lengths and harmonic frequencies are presented for the ground states of the group 4 tetrahydrides, CH4, SiH4, GeH4, SnH4, and PbH4. The results are compared with relativistic effective core potential (RECP) calculations, first-order perturbation theory (PT) calculations and with experimental data. The bond lengths are well predicted by first-order perturbation theory for all molecules, but non of the RECP's considered provides a consistent prediction. Perturbation theory overestimates the relativistic correction to the harmonic frequencies; the RECP calculations underestimate the correction

Bright soliton trains of trapped Bose-Einstein condensates

We variationally determine the dynamics of bright soliton trains composed of harmonically trapped Bose-Einstein condensates with attractive interatomic interactions. In particular, we obtain the interaction potential between two solitons. We also discuss the formation of soliton trains due to the quantum mechanical phase fluctuations of a one-dimensional condensate.Comment: 4 pages, 2 figures, submitted to PR

Deformation of a Trapped Fermi Gas with Unequal Spin Populations

The real-space densities of a polarized strongly-interacting two-component Fermi gas of $^6$Li atoms reveal two low temperature regimes, both with a fully-paired core. At the lowest temperatures, the unpolarized core deforms with increasing polarization. Sharp boundaries between the core and the excess unpaired atoms are consistent with a phase separation driven by a first-order phase transition. In contrast, at higher temperatures the core does not deform but remains unpolarized up to a critical polarization. The boundaries are not sharp in this case, indicating a partially-polarized shell between the core and the unpaired atoms. The temperature dependence is consistent with a tricritical point in the phase diagram.Comment: Accepted for publication in Physical Review Letter

Response to Comment on "Pairing and Phase Separation in a Polarized Fermi Gas"

Zwierlein and Ketterle rely on subjective arguments and fail to recognize important differences in physical parameters between our experiment and theirs. We stand by the conclusions of our original report