9,077 research outputs found

    Strong spin-lattice coupling in multiferroic HoMnO3_{3}: Thermal expansion anomalies and pressure effect

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    Evidence for a strong spin-lattice coupling in multiferroic HoMnO_3 is derived from thermal expansion measurements along a- and c-axis. The magnetoelastic effect results in sizable anomalies of the thermal expansivities at the antiferromagnetic (T_N) and the spin rotation (T_{SR}) transition temperatures as well as in a negative c-axis expansivity below room temperature. The coupling between magnetic orders and dielectric properties below T_N is explained by the lattice strain induced by the magnetoelastic effect. At T_{SR} various physical quantities show discontinuities that are thermodynamically consistent with a first order phase transition

    Low temperature dielectric anomalies in HoMnO_3: The complex phase diagram

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    The dielectric constant of multiferroic hexagonal HoMnO_3 exhibits an unprecedented diversity of anomalies at low temperatures (1.8 K< T <10 K) and under external magnetic fields related to magnetic phase transitions in the coupled system of Ho moments, Mn spins, and ferroelectric polarization. The derived phase diagram is far more complex than previously assumed including reentrant phases, phase transitions with distinct thermal and field hysteresis, as well as several multicritical points. Magnetoelastic interactions introduce lattice anomalies at the magnetic phase transitions. The re-evaluation of the T-H phase diagram of HoMnO_3 is demanded.Comment: 12 pages, 3 figure

    Controlling Curriculum Redesign with a Process Improvement Model

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    A portion of the curriculum for a Management Information Systems degree was redesigned to enhance the experiential learning of students by focusing it on a three-semester community-based system development project. The entire curriculum was then redesigned to have a project-centric focus with each course in the curriculum contributing to the success of students’ learning experiences. Implementation of this new design involved an evolutional enhancement from an existing traditional curriculum with modifications proceeding in stages over a four-year period. Early on, it was recognized that the curriculum redesign was progressing through a series of stages similar to that encountered in software engineering processes. As a result, the general guidelines and framework developed for continuous improvement in software engineering: the Capability Maturity Model were adopted and modified for guiding the curriculum redesign. This paper presents a description of the authors’ experiences in implementing a curriculum redesign from one based on a traditional course-based design to a project-centric design using the Capability Maturity Model as a process improvement tool. Our successful experience with using this tool suggests a need for the development of a specialized process improvement tool for future use on similar curriculum redesign

    Hubungan Gaya Belajar Dengan Hasil Belajar Siswa Pada Pembelajaran Biologi Kelas X Sman 2 Sungai Tarab Kabupaten Tanah Datar

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    The purpose of this study was to determine whether there is a relationship of learning styles to student learning outcomes in learning biology. The strength of the relationship can be seen in the interpretation of the correlation table. This research is ex post facto with research subjects are students of class X SMAN 2 Sungaitarab the 2015/2016 academic year are 71 people with the sampling technique used was random sampling with an error rate of 5%. Data collection method for variable learning style is by questionnaire, while studying biology outcome variables using vocational school documentation data analysis technique used is the product moment correlation with the level of significance of the analysis results is set at 5%. The results showed that there are no significant and positive relationship between learning styles to student learning outcomes in learning biology, this is evidenced by rhitung (0.089) <rtabel (0, 235), the Ha Ho is rejected and accepted. Based on the results of the study showed no significant positive relationship between the three variables of learning styles to student learning outcomes in the subjects of biology, it is thus test this hypothesis does not support the research

    Marginally Trapped Surfaces in the Nonsymmetric Gravitational Theory

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    We consider a simple, physical approach to the problem of marginally trapped surfaces in the Nonsymmetric Gravitational Theory (NGT). We apply this approach to a particular spherically symmetric, Wyman sector gravitational field, consisting of a pulse in the antisymmetric field variable. We demonstrate that marginally trapped surfaces do exist for this choice of initial data.Comment: REVTeX 3.0 with epsf macros and AMS symbols, 3 pages, 1 figur

    Stability of Horava-Lifshitz Black Holes in the Context of AdS/CFT

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    The anti--de Sitter/conformal field theory (AdS/CFT) correspondence is a powerful tool that promises to provide new insights toward a full understanding of field theories under extreme conditions, including but not limited to quark-gluon plasma, Fermi liquid and superconductor. In many such applications, one typically models the field theory with asymptotically AdS black holes. These black holes are subjected to stringy effects that might render them unstable. Ho\v{r}ava-Lifshitz gravity, in which space and time undergo different transformations, has attracted attentions due to its power-counting renormalizability. In terms of AdS/CFT correspondence, Ho\v{r}ava-Lifshitz black holes might be useful to model holographic superconductors with Lifshitz scaling symmetry. It is thus interesting to study the stringy stability of Ho\v{r}ava-Lifshitz black holes in the context of AdS/CFT. We find that uncharged topological black holes in λ=1\lambda=1 Ho\v{r}ava-Lifshitz theory are nonperturbatively stable, unlike their counterparts in Einstein gravity, with the possible exceptions of negatively curved black holes with detailed balance parameter ϵ\epsilon close to unity. Sufficiently charged flat black holes for ϵ\epsilon close to unity, and sufficiently charged positively curved black holes with ϵ\epsilon close to zero, are also unstable. The implication to the Ho\v{r}ava-Lifshitz holographic superconductor is discussed.Comment: 15 pages, 6 figures. Updated version accepted by Phys. Rev. D, with corrections to various misprints. References update

    Undetermined states: how to find them and their applications

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    We investigate the undetermined sets consisting of two-level, multi-partite pure quantum states, whose reduced density matrices give absolutely no information of their original states. Two approached of finding these quantum states are proposed. One is to establish the relation between codewords of the stabilizer quantum error correction codes (SQECCs) and the undetermined states. The other is to study the local complementation rules of the graph states. As an application, the undetermined states can be exploited in the quantum secret sharing scheme. The security is guaranteed by their undetermineness.Comment: 6 pages, no figur

    Topological twisted sigma model with H-flux revisited

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    In this paper we revisit the topological twisted sigma model with H-flux. We explicitly expand and then twist the worldsheet Lagrangian for bi-Hermitian geometry. we show that the resulting action consists of a BRST exact term and pullback terms, which only depend on one of the two generalized complex structures and the B-field. We then discuss the topological feature of the model.Comment: 16 pages. Appendix adde
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