Time and dark matter from the conformal symmetries of Euclidean space

The quotient of the conformal group of Euclidean 4-space by its Weyl subgroup results in a geometry possessing many of the properties of relativistic phase space, including both a natural symplectic form and non-degenerate Killing metric. We show that the general solution posesses orthogonal Lagrangian submanifolds, with the induced metric and the spin connection on the submanifolds necessarily Lorentzian, despite the Euclidean starting pont. By examining the structure equations of the biconformal space in an orthonormal frame adapted to its phase space properties, we also find that two new tensor fields exist in this geometry, not present in Riemannian geometry. The first is a combination of the Weyl vector with the scale factor on the metric, and determines the timelike directions on the submanifolds. The second comes from the components of the spin connection, symmetric with respect to the new metric. Though this field comes from the spin connection it transforms homogeneously. Finally, we show that in the absence of conformal curvature or sources, the configuration space has geometric terms equivalent to a perfect fluid and a cosmological constant.Comment: 26 pages, no figures. Appreciable introductory material added. Results substantially strengthened and explained. New results concerning dark matter and dark energy candidates added to this versio

Mechanical phase mapping of meteorites: Combining EDX and nanoindentation

Meteorites are perhaps one of the most tangible aspects of outer space. With their irregular, ablated surfaces and intricate Widmanstätten microstructures, they truly appear to be otherworldly. The internal microstructure and composition of meteorites has been intensively studied and classified by astro- and geo-chemists to study their origins and formation processes [1]. However, other than some microhardness testing in the 1950s [2], very little has been done to characterize the mechanical behavior of these unique pieces of other worlds. With the advent of modern, high speed nanoindentation techniques, it is now possible to map the mechanical features of materials over square millimeters of area with micron-level resolution in a reasonable amount of time. Please click Additional Files below to see the full abstract

Improving Language Proficiency Through Effective Use Of Authentic Assessments In High School Spanish Courses

The research question addressed is: How can high school Spanish students improve language proficiency through the use of authentic assessments? This capstone documents the research and design of a high school Spanish language curriculum. The capstone explores methods and strategies used to teach world languages throughout the twentieth century to American students and provides analysis of the popular trends in foreign language instruction over the years. The author illustrates the curriculum model and identifies the performance-based assessments used to evaluate student’s proficiency in Spanish. The capstone goes on to highlight the limitations and challenges of creating a performance-based, proficiencycentered curriculum which relies on authentic assessments to measure learning goals. It also provides recommendations for using the curriculum. Spanish curriculum is divided into categories based on what specific language performance skill is being assessed

How General and Special Educators’ Conceptualizations of Critical Thinking Influence Their Pedagogy for Students with Disabilities in Secondary English Inclusive Classrooms

The purpose of the study was to explore the intersection of critical thinking, teachers’ thought processes and values, and students with disabilities. More specifically, the researcher sought to reach a stronger understanding of how general and special educators’ decisions to explicitly and/or implicitly embed critical thinking into English course content for students with and without disabilities at the secondary level are influenced by teachers’ conceptualizations of critical thinking. The study utilized case study methods with four participants who teach in co-teaching pairs (i.e., a general and special educator who comprise the co-teaching partnership in 9th Lit, and a general and special educator who comprise the co-teaching partnership in Multicultural Lit), located within one high school in a suburban area of a major metropolitan city. The overarching research question asks, How general and special educators’ conceptualizations of critical thinking influence their pedagogy for students with disabilities in secondary English inclusive classrooms? The three sub-questions embedded within the overarching research question were: 1) How do teachers define, understand, and view critical thinking? (theory-based) 2) How do teachers frame the aptitude and achievement of students with disabilities in light of their philosophies, ideologies, and attitudes and their conceptualizations of critical thinking? (theory-based) 3) How and when do teachers incorporate critical thinking into the classroom for students with disabilities? (practice-based) In order to address these research questions, data were collected in the form of in-depth biographical and semi-structured interviews, classroom observations and informal conversations, and visual representations of critical thinking. Cross-case analysis of the data illuminated four themes, with each theme situated in a unique educational context: 1) New problems exist with the old problems, in terms of the societal and institutional factors that influence student success and critical thinking 2) Teachers and students may practice critical thinking without theorizing it, which explores the conceptual underpinnings of critical thinking in the classroom 3) Within the walls of schools, teachers prepare students for life beyond the walls of schools, linking students from an educational context to a real-world context 4) In the context of academic achievement, not every student can reach the pre-established goal, but every student can reach a student-centered goal, These assertions illuminated through data analysis reflect seemingly contradictory ideas. Yet, conceptualizing the study’s cross-case findings through the frame of these themes and these contexts speaks to the complexities in teachers’ ideologies and instructional practices for students with disabilities in secondary English inclusive classrooms, particularly regarding how teachers foster critical thinking for students with disabilities

Fracture of silicon at low length scales

At small length scales, perhaps no material is more industrially important than silicon. It enabled the information age, and micro-electro-mechanical systems (MEMS) made of silicon are increasingly integrated into our daily lives via smartphones. Classically, silicon is known as a brittle material, whose sharp brittle-ductile transition (BDT) occurs within a matter of one or two degrees Celsius at a temperature between 500 and 800 °C depending on the microstructure, strain rate, and crystal orientation [1]. However, recent advances in sample miniturization has revealed that plastic compressive deformation can occur in silicon at room temperature if the sample size is reduced below 400 nm [2]. This raised the question of whether silicon’s intrinsic fracture toughness also changed at reduced length scales. The development of many new micro-geometries for measurement of fracture toughness allowed this question to be comprehensively answered for the micron length scale – with the answer being no [3]. However, this didn’t necessitate that the BDT was unaffected. Please click Additional Files below to see the full abstract

Economic Efficiency of Short-Term Versus Long-Term Water Rights Buyouts

Because of the decline of the Ogallala Aquifer, water districts, regional water managers, and state water officers are becoming increasingly interested in conservation policies. This study evaluates both short-term and long-term water rights buyout policies. This research develops dynamic production functions for the major crops in the Texas Panhandle. The production functions are incorporated into optimal temporal allocation models that project annual producer behavior, crop choices, water use, and aquifer declines over 60 years. Results suggest that long-term buyouts may be more economically efficient than short-term buyouts.dynamic production function, nonlinear optimization, Ogallala Aquifer, water rights buyout, Agribusiness, Environmental Economics and Policy, Q30, Q32, Q38,

Nanoindentation Under Dynamic Conditions

Nanoindentation has emerged as a leading technique for the investigation of mechanical properties on small volumes of material. Extensive progress has been made in the last 20 years in refining the nstrumentation of nanoindentation systems and in analysis of the resulting data. Recent development has enabled investigation of materials under several dynamic conditions. The palladium-hydrogen system has a large miscibility gap, where the palladium lattice rapidly expands to form a hydrogen-rich β phase upon hydrogenation. Nanoindentation was used to investigate the mechanical effects of these transformations on foils of palladium. Study of palladium foils, which had been cycled through hydrogenation and dehydrogenation, allowed the extent of the transformed region to be determined. Unstable palladium foils, which had been hydrogenated and were subject to dynamic hydrogen loss, displayed significant hardening in the regions which were not expected to have transformed. The reason for this remains unclear. Impact indentation, where the indenter encounters the sample at relatively high speeds, can be used to probe the strain rate dependence of materials. By combining impact indentation and elevated temperature indentation, the strain rate dependence of the superelasticity of nickel-titanium was probed over a range of temperatures. Similar trends in elastic energy ratios with temperature were observed with the largest elastic proportions occurring at the Austenite finish transformation temperature. Multiple impact and scratch indentation are two modes of indentation which are thought to approximate erosive and abrasive wear mechanisms, respectively. These were utilised to investigate the wear resistance of several novel coatings formed by plasma electrolytic oxidation (PEO) of Ti-6Al4-V. Multiple impact indentation results appear to subjectively rank the erosive wear performance of both ductile and brittle materials. Comparison of normalised performance of coating systems on aluminium in abrasive wear to scratch hardness showed similar degrees of resistance.This material is based upon work supported under a National Science Foundation Graduate Research Fellowship. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Additional support for this work was provided by funding from the Atomic Weapons Establishment

Scalable Agent-Based Modeling for Complex Financial Market Simulations

In this study, we developed a computational framework for simulating large-scale agent-based financial markets. Our platform supports trading multiple simultaneous assets and leverages distributed computing to scale the number and complexity of simulated agents. Heterogeneous agents make decisions in parallel, and their orders are processed through a realistic, continuous double auction matching engine. We present a baseline model implementation and show that it captures several known statistical properties of real financial markets (i.e., stylized facts). Further, we demonstrate these results without fitting models to historical financial data. Thus, this framework could be used for direct applications such as human-in-the-loop machine learning or to explore theoretically exciting questions about market microstructure's role in forming the statistical regularities of real markets. To the best of our knowledge, this study is the first to implement multiple assets, parallel agent decision-making, a continuous double auction mechanism, and intelligent agent types in a scalable real-time environment