388 research outputs found

    How Should Institutions of Higher Education Define and Measure Student Success? Student Success as Liberal Education Escapes Definition and Measurement

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    [First paragraph] The question structuring this chapter begins with the presumption that we should define and measure student success. The perspective missing from this question is: What possibilities exist for versions of student success in excess of its definition and measurement? Measurements ask us to standardize definitions of success—say, four-year graduation—and work to produce all students in this image. As a former academic adviser, I can read a university catalog and tell you the quickest pathways to graduation a university has to offer. This makes me an asset to institutions that place a value on student success as measured by graduation rates, but does shuttling students to majors with comparatively lax degree requirements produce an expansive version of student success? I am the last person to argue that metrics of student success such as college graduation lack all meaning. However, when measurements of achievements like college graduation become the focus of student affairs practice, they warp our institutions and our students in their image.1 I use graduation here as it is the most frequently cited definition of student success today, but this logic follows no matter what definition you substitute in its place. In what follows, I argue that definitions and measurements of student success construct student realities in ways that are counterproductive to liberal education, and liberal education is the ineffable outcome of higher education that produces students capable of changing the structures of our profoundly problematic world

    Construction of some missing eigenvectors of the XYZ spin chain at the discrete coupling constants and the exponentially large spectral degeneracy of the transfer matrix

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    We discuss an algebraic method for constructing eigenvectors of the transfer matrix of the eight vertex model at the discrete coupling parameters. We consider the algebraic Bethe ansatz of the elliptic quantum group Eτ,η(sl2)E_{\tau, \eta}(sl_2) for the case where the parameter η\eta satisfies 2Nη=m1+m2τ2 N \eta = m_1 + m_2 \tau for arbitrary integers NN, m1m_1 and m2m_2. When m1m_1 or m2m_2 is odd, the eigenvectors thus obtained have not been discussed previously. Furthermore, we construct a family of degenerate eigenvectors of the XYZ spin chain, some of which are shown to be related to the sl2sl_2 loop algebra symmetry of the XXZ spin chain. We show that the dimension of some degenerate eigenspace of the XYZ spin chain on LL sites is given by N2L/NN 2^{L/N}, if L/NL/N is an even integer. The construction of eigenvectors of the transfer matrices of some related IRF models is also discussed.Comment: 19 pages, no figure (revisd version with three appendices

    Finding critical points using improved scaling Ansaetze

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    Analyzing in detail the first corrections to the scaling hypothesis, we develop accelerated methods for the determination of critical points from finite size data. The output of these procedures are sequences of pseudo-critical points which rapidly converge towards the true critical points. In fact more rapidly than previously existing methods like the Phenomenological Renormalization Group approach. Our methods are valid in any spatial dimensionality and both for quantum or classical statistical systems. Having at disposal fast converging sequences, allows to draw conclusions on the basis of shorter system sizes, and can be extremely important in particularly hard cases like two-dimensional quantum systems with frustrations or when the sign problem occurs. We test the effectiveness of our methods both analytically on the basis of the one-dimensional XY model, and numerically at phase transitions occurring in non integrable spin models. In particular, we show how a new Homogeneity Condition Method is able to locate the onset of the Berezinskii-Kosterlitz-Thouless transition making only use of ground-state quantities on relatively small systems.Comment: 16 pages, 4 figures. New version including more general Ansaetze basically applicable to all case

    Uniformity transition for ray intensities in random media

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    This paper analyses a model for the intensity of distribution for rays propagating without absorption in a random medium. The random medium is modelled as a dynamical map. After N iterations, the intensity is modelled as a sum S of N contributions from different trajectories, each of which is a product of N independent identically distributed random variables xk, representing successive focussing or de-focussing events. The number of ray trajectories reaching a given point is assumed to proliferate exponentially: N=ΛN, for some Λ>1. We investigate the probability distribution of S. We find a phase transition as parameters of the model are varied. There is a phase where the fluctuations of S are suppressed as N → ∞, and a phase where the S has large fluctuations, for which we provide a large deviation analysis

    Thermodynamic Comparison and the Ideal Glass Transition of A Monatomic Systems Modeled as an Antiferromagnetic Ising Model on Husimi and Cubic Recursive Lattices of the Same Coordination Number

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    Two kinds of recursive lattices with the same coordination number but different unit cells (2-D square and 3-D cube) are constructed and the antiferromagnetic Ising model is solved exactly on them to study the stable and metastable states. The Ising model with multi-particle interactions is designed to represent a monatomic system or an alloy. Two solutions of the model exhibit the crystallization of liquid, and the ideal glass transition of supercooled liquid respectively. Based on the solutions, the thermodynamics on both lattices was examined. In particular, the free energy, energy, and entropy of the ideal glass, supercooled liquid, crystal, and liquid state of the model on each lattice were calculated and compared with each other. Interactions between particles farther away than the nearest neighbor distance are taken into consideration. The two lattices show comparable properties on the transition temperatures and the thermodynamic behaviors, which proves that both of them are practical to describe the regular 3-D case, while the different effects of the unit types are still obvious.Comment: 27 pages, 13 figure

    Classical phase transitions in a one-dimensional short-range spin model

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    Ising's solution of a classical spin model famously demonstrated the absence of a positive-temperature phase transition in one-dimensional equilibrium systems with short-range interactions. No-go arguments established that the energy cost to insert domain walls in such systems is outweighed by entropy excess so that symmetry cannot be spontaneously broken. An archetypal way around the no-go theorems is to augment interaction energy by increasing the range of interaction. Here we introduce new ways around the no-go theorems by investigating entropy depletion instead. We implement this for the Potts model with invisible states.Because spins in such a state do not interact with their surroundings, they contribute to the entropy but not the interaction energy of the system. Reducing the number of invisible states to a negative value decreases the entropy by an amount sufficient to induce a positive-temperature classical phase transition. This approach is complementary to the long-range interaction mechanism. Alternatively, subjecting positive numbers of invisible states to imaginary or complex fields can trigger such a phase transition. We also discuss potential physical realisability of such systems.Comment: 29 pages, 11 figure

    A sufficient criterion for integrability of stochastic many-body dynamics and quantum spin chains

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    We propose a dynamical matrix product ansatz describing the stochastic dynamics of two species of particles with excluded-volume interaction and the quantum mechanics of the associated quantum spin chains respectively. Analyzing consistency of the time-dependent algebra which is obtained from the action of the corresponding Markov generator, we obtain sufficient conditions on the hopping rates for identifing the integrable models. From the dynamical algebra we construct the quadratic algebra of Zamolodchikov type, associativity of which is a Yang Baxter equation. The Bethe ansatz equations for the spectra are obtained directly from the dynamical matrix product ansatz.Comment: 19 pages Late

    Analysing the temporal water quality dynamics of Lake Basaka, Central Rift Valley of Ethiopia

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    Abstract: This study presents the general water quality status and temporal quality dynamics of Lake Basaka water in the past about 5 decades. Water samples were collected and analysed for important physico-chemical quality parameters following standard procedures. The result showed that Lake Basaka water is highly saline and alkaline and experiencing a general reducing trends in ionic concentrations of quality parameters due to the dilution effect. About 10-fold reduction of total ionic concentration occurred in the Lake over the period of 2 decades (1960-1980). There was a sharp and fast decline in EC, Cl, SO4, Na, and K ions from early 1960s up to the late 1980s, and then became relatively stable. Some ions (eg. Na, Ca, Mg, Cl, SO4) are showing increment in recent years. This characteristics of the lake water is terrible in relation to its potential to inundate the nearby areas in the near future. The expansion of such quality water has negative effects on the water resources of the region, especially soil quality, drainage and groundwater, in terms of salinity, sodicity and specific ion toxicity. The regimes of soil moisture, solute and groundwater could be affected, concurrently affecting the productivity and sustainability of the sugar estate. Thus, there is an urgent need to identify the potential sources of water and chemicals to the lake and devise an appropriate mitigation and/or remedial measures

    Algebraic Bethe ansatz method for the exact calculation of energy spectra and form factors: applications to models of Bose-Einstein condensates and metallic nanograins

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    In this review we demonstrate how the algebraic Bethe ansatz is used for the calculation of the energy spectra and form factors (operator matrix elements in the basis of Hamiltonian eigenstates) in exactly solvable quantum systems. As examples we apply the theory to several models of current interest in the study of Bose-Einstein condensates, which have been successfully created using ultracold dilute atomic gases. The first model we introduce describes Josephson tunneling between two coupled Bose-Einstein condensates. It can be used not only for the study of tunneling between condensates of atomic gases, but for solid state Josephson junctions and coupled Cooper pair boxes. The theory is also applicable to models of atomic-molecular Bose-Einstein condensates, with two examples given and analysed. Additionally, these same two models are relevant to studies in quantum optics. Finally, we discuss the model of Bardeen, Cooper and Schrieffer in this framework, which is appropriate for systems of ultracold fermionic atomic gases, as well as being applicable for the description of superconducting correlations in metallic grains with nanoscale dimensions. In applying all of the above models to physical situations, the need for an exact analysis of small scale systems is established due to large quantum fluctuations which render mean-field approaches inaccurate.Comment: 49 pages, 1 figure, invited review for J. Phys. A., published version available at http://stacks.iop.org/JPhysA/36/R6
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