http://hdl.handle.net/2374.OX/4071 2013-05-20T19:51:42Z http://hdl.handle.net/2374.OX/108117 Fermion Pairing and BEC-BCS Crossover in Novel Systems Liao, Renyuan This dissertation covers my theoretical work in the field of pairing of fermions and BCS-BEC crossover behavior in various condensed matter systems. High temperature superconductors, heavy fermion systems, 2D semiconductors undergoing a semiconductor-superconductor transition, and ultracold atomic Fermi gases are examples of novel systems that provide us with a rich playground to study pairing phenomena such as superconductivity or superfluidity. In this dissertation, with ultracold fermions in mind, I attempt to address some of the outstanding theoretical issues regarding pairing of fermions for arbitrary interactions, and for arbitrary population and mass imbalance. In so doing, I explore pairing in Bose-Einstein condensation (BEC) and Bardeen-Cooper-Schrieffer (BCS) regimes, and the behavior at the BEC-BCS crossover. I investigate the stability of paired many-fermion ground states, e.g., superfluidity and phase separated states; and possible phase transitions between these ground states. The specific projects that I undertake at the mean-field level are: interplay of intra- and inter- species pairing correlations in determining s-wave pairing in spin-population imbalanced Fermi systems; p-wave pairing in systems with mismatched fermi surfaces; stability of “breached pairs” states with p-wave symmetry in BEC and BCS regimes; use of Bogoliubov-de Gennes equations to study spatial variation of the pairing order parameter; and superconductivity with unconventional pairing symmetries in 2D systems with an “inherent” gaps, such as in semiconducting systems. In the case of s-wave pairing in a spin-population imbalanced system, while the system phase separates into normal and superfluid components, I show that the inclusion of intra-species correlation stabilizes a supefluid phase, up to a critical polarization, on the BCS side. For S=1, ms=0 triplet p-wave pairing in a population imbalanced system, I obtain a rich phase diagram. In addition to the states Δ±1 propto Y1±1, a multitude of “mixed” SF states formed of linear combinations of Y1m's give global energy minimum under a phase stability condition. States with local minimum are also obtained. With increased polarization, the global minimum SF states may undergo a quantum phase transition to the local minimum SF states. I also study effects of finite temperature (T) and of mass imbalance (r) between the species. Though the features of the phase diagram are not changed qualitatively from the equal mass (r=1) case, the critical temperature Tc shows some interesting behavior for large polarization. Our p-wave pairing provides an arena to study “breached pairing” (BP), i.e., phase separation in momentum space. While this is not stable in BCS regime for s-wave pairing, I find that p-wave BP phases may be stable in both BCS and BEC regimes for arbitrary mass ratio, r. To explore many-body effects beyond mean-field, I study the effects of quantum fluctuations on equilibrium and pairing properties in BEC and BCS regimes and near the crossover (unitarity limit). I apply this to systems subjected to p-wave Feshbach resonance and compare with the results for the s-wave case. I also study the effects of these fluctuations on possible suppression of the superfluid transition temperature from dilute to dense regimes and at unitarity, and find the suppression factor of 2.2 to be quite robust, except close to unitarity. Specific systems to which my work may apply are population imbalanced cold atomic systems, 2D systems with “inherent gap”, such as semiconducting systems, and strongly correlated Fermi systems close to the unitarity limit at the BEC-BCS crossover. My research utilizes method of many-body quantum field theory, quantum statistical mechanics, diagrammatic perturbation theory, notions of superconductivity and superfluidity at and beyond mean-field level. In many instances, I have developed detailed and reliable computer codes relevant to my work. 2009-04-10T08:54:08Z http://hdl.handle.net/2374.OX/108116 Combining the Power of Poetry, Repeated Readings, and Community Volunteers for Literacy Intervention: The Poetry Academy Wilfong, Lori Georgianne The purpose of the this study was to examine the effective use of community volunteers in four third grade classrooms at one rural elementary school in Northeast Ohio in a program called the Poetry Academy. A sequential-explanatory mixed methods research paradigm framed this study. The research questions were: (1) Does the Poetry Academy have an effect on student’s fluency and comprehension scores, as shown through the use of a curriculum-based measurement given before and after the implementation of the program, measuring (a) words correct per minute (WCPM); (b) word recognition; and (c) score on a retelling? (2) Does the Poetry Academy have an effect on students’ attitude towards reading, as measured both before and after the implementation of the program by the Elementary Reading Attitude Survey (McKenna & Kear, 1990)? (3) What observations or changes have students, parents, teachers, and volunteers observed in the students towards reading, if any, during the implementation of the program? and (4) What have students, parents, teachers, and volunteers observed as advantages and disadvantages of the program? Thirty-six students were purposefully sampled from a population of 86 third graders to participate in the Poetry Academy based on their score on a curriculum-based assessment measuring words correct per minute, word recognition, and a score on a retelling. During the eleven weeks of the program, six volunteers read poetry with the sampled students in a weekly cycle. Components of repeated reading (Homan, Klesius, & Hite, 1993; Khun & Stahl, 2003; Samuels, 1979; Therrien, 2004), listening-while-reading (Lionetti & Cole, 2004; Rasinski, 1990), assisted reading (Hoskisson & Krohm, 1974; Kuhn & Stahl, 2004), and modeling (Chard, Vaughn, & Tyler, 2002) were used during their ten minute, weekly sessions. Findings reveal that significant gain was made in the treatment population when compared to the control group in the areas of words correct per minute, word recognition, and attitude toward academic reading, while a marginally significant gain was made in the area of comprehension. Change in the treatment group was observed by the students, themselves, volunteers, teachers, and parents and included an increase in confidence when reading and improved attitude toward school. The most notable contribution of this study is the combination of tutoring methods used during the ten minute, weekly sessions between volunteer and Poetry Academy student. Using the methods described above, the volunteers were able to affect change in students identified as disfluent when compared to national norms (Hasbrouck & Tindal, 2006). Also significant is the use of poetry. The Poetry Academy used poetry with positive results with students. Teachers, students, volunteers, and parents mentioned the short nature of poetry, combined with its usually humorous text, in conjunction with the improvements of the apprentices in their reading skills and attitudes towards reading. The use of poetry in the classroom could be used to help build confidence in students, as well as improve their reading skills and attitudes (Certo, 2004; Homan et al., 1993; Moyer, 1982; Perfect, 2005; Rasinski, 2000; Rasinski et al., 1994). 2009-04-10T08:53:56Z http://hdl.handle.net/2374.OX/108115 “Doing Gender” in Doctor-patient Interactions: Gender Composition of Doctor-patient Dyads and Communication Patterns MacArthur, Kelly Rhea There are many well documented gender differences in language, but explanations for why they exist vary. Taking a distinctly sociological approach, this thesis uses the “doing gender” framework to analyze gender in interactions. Drawing on past literature on women and men generally and on women and men physicians specifically, this research examines how gender affects doctor-patient communication. Using medical student-standardized patient interactions, several different specific communication behaviors are measured to indicate if women physicians conduct more patient-centered, partnership-building medical encounters and if they have communication skills that are considered to be better than men physicians’. Results show that women physicians do not have medical encounters that indicate greater patient-centered care or greater symmetrical encounters than men physicians do. The results of this study suggest that the influence of patients in forming doctor-patient interactions should not be ignored, as they typically have been in past studies. As with all social interactions, women and men are always “doing gender” in doctor-patient interactions even though diminished gender effects on communication are found here. If gender differences in language were due to essentialist, natural differences between the two sexes, they would be consistent across contexts, which the results of this study show they are not. 2009-04-10T08:53:43Z http://hdl.handle.net/2374.OX/108114 A Comparative Study of Approaches to Teaching Melodic Dictation Sisley, Beth Ann Recent studies show that tonic induction, pitch collection induction, development of memory, and attentive listening are important for a melodic dictation class. Melodic dictation textbooks published in the twenty-first century reflect these findings and have changed their emphasis when compared to earlier publications. In newer textbooks, there is a greater emphasis on hearing melodies in a functional context and memorizing the melodies. Less information is provided for score setup of melodic dictation exercises in newer textbooks. Students are expected to infer the key, tonic, and starting pitch. In some cases, they are expected to determine the meter signature. This study will describe several different methods currently used for melodic dictation, and it will provide a curriculum for working with college freshman musicians. There is little published research on this topic, and I hope that this study will be useful to current and future theorists in their teaching. 2009-04-10T08:53:31Z