40,499 research outputs found

    Symmetric-Gapped Surface States of Fractional Topological Insulators

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    We construct the symmetric-gapped surface states of a fractional topological insulator with electromagnetic Īø\theta-angle Īøem=Ļ€3\theta_{em} = \frac{\pi}{3} and a discrete Z3\mathbb{Z}_3 gauge field. They are the proper generalizations of the T-pfaffian state and pfaffian/anti-semion state and feature an extended periodicity compared with their of "integer" topological band insulators counterparts. We demonstrate that the surface states have the correct anomalies associated with time-reversal symmetry and charge conservation.Comment: 5 pages, 33 references and 2 pages of supplemental materia

    Generating entanglement with low Q-factor microcavities

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    We propose a method of generating entanglement using single photons and electron spins in the regime of resonance scattering. The technique involves matching the spontaneous emission rate of the spin dipole transition in bulk dielectric to the modified rate of spontaneous emission of the dipole coupled to the fundamental mode of an optical microcavity. We call this regime resonance scattering where interference between the input photons and those scattered by the resonantly coupled dipole transition result in a reflectivity of zero. The contrast between this and the unit reflectivity when the cavity is empty allow us to perform a non demolition measurement of the spin and to non deterministically generate entanglement between photons and spins. The chief advantage of working in the regime of resonance scattering is that the required cavity quality factors are orders of magnitude lower than is required for strong coupling, or Purcell enhancement. This makes engineering a suitable cavity much easier particularly in materials such as diamond where etching high quality factor cavities remains a significant challenge

    Quantum Thetas on Noncommutative T^4 from Embeddings into Lattice

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    In this paper we investigate the theta vector and quantum theta function over noncommutative T^4 from the embedding of R x Z^2. Manin has constructed the quantum theta functions from the lattice embedding into vector space (x finite group). We extend Manin's construction of the quantum theta function to the embedding of vector space x lattice case. We find that the holomorphic theta vector exists only over the vector space part of the embedding, and over the lattice part we can only impose the condition for Schwartz function. The quantum theta function built on this partial theta vector satisfies the requirement of the quantum theta function. However, two subsequent quantum translations from the embedding into the lattice part are non-additive, contrary to the additivity of those from the vector space part.Comment: 20 pages, LaTeX, version to appear in J. Phys.

    Fracture mechanics approach to design analysis of notches, steps and internal cut-outs in planar components

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    A new approach to the assessment and optimization of geometric stress-concentrating features is proposed on the basis of the correspondence between sharp crack or corner stressfield intensity factors and conventional elastic stress concentration factors (SCFs) for radiused transitions. This approach complements the application of finite element analysis (FEA) and the use of standard SCF data from the literature. The method makes it possible to develop closed-form solutions for SCFs in cases where corresponding solutions for the sharp crack geometries exist. This is helpful in the context of design optimization. The analytical basis of the correspondence is shown, together with the limits on applicability where stress-free boundaries near the stress concentrating feature are present or adjacent features interact. Examples are given which compare parametric results derived from FEA with closed-form solutions based on the proposed method. New information is given on the stress state at a 90Ā° corner or width step, where the magnitude of the stress field intensity is related to that of the corresponding crack geometry. This correspondence enables the user to extend further the application of crack-tip stress-field intensity information to square-cornered steps, external U-grooves, and internal cut-outs

    The origins of media trust in a young democracy

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    Declining trust in news media has often been recognized as one of the major challenges facing modern journalism with potentially detrimental consequences for democratic processes. In this article, we examine the predictive potential of cultural-political and performance factors on public trust in news media in the context of a young democracy. Specifically, we have analyzed to what extent citizensā€™ populist attitudes and perceptions of journalistic roles relate to the levels of media trust using data from an online survey of Serbian respondents (N = 200). The findings showed that support for populism did not significantly predict trust in news media in general after controlling for relevant factors, most importantly political trust. However, populist attitudes were found to be related to the amount of trust citizens have in distinct types of news media ā€“i.e., those who support populism exhibited less trust in public broadcasters than in online news outlets. The analyses also revealed that the more Serbian citizens perceived news media as being successful at performing interpretive and mobilizing roles, the more trust they placed in the media
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