165 research outputs found

    Terahertz imaging and spectroscopy of large-area single-layer graphene

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    We demonstrate terahertz (THz) imaging and spectroscopy of a 15x15-mm^2 single-layer graphene film on Si using broadband THz pulses. The THz images clearly map out the THz carrier dynamics of the graphene-on-Si sample, allowing us to measure sheet conductivity with sub-mm resolution without fabricating electrodes. The THz carrier dynamics are dominated by intraband transitions and the THz-induced electron motion is characterized by a flat spectral response. A theoretical analysis based on the Fresnel coefficients for a metallic thin film shows that the local sheet conductivity varies across the sample from {\sigma}s = 1.7x10^-3 to 2.4x10^-3 {\Omega}^-1 (sheet resistance, {\rho}s = 420 - 590 {\Omega}/sq).Comment: 6 pages, 5 figure

    Rotation and Spin in Physics

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    We delineate the role of rotation and spin in physics, discussing in order Newtonian classical physics, special relativity, quantum mechanics, quantum electrodynamics and general relativity. In the latter case, we discuss the generalization of the Kepler formula to post-Newtonian order (c2(c^{-2}) including spin effects and two-body effects. Experiments which verify the theoretical results for general relativistic spin-orbit effects are discussed as well as efforts being made to verify the spin-spin effects

    Chaotic scalar fields as models for dark energy

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    We consider stochastically quantized self-interacting scalar fields as suitable models to generate dark energy in the universe. Second quantization effects lead to new and unexpected phenomena is the self interaction strength is strong. The stochastically quantized dynamics can degenerate to a chaotic dynamics conjugated to a Bernoulli shift in fictitious time, and the right amount of vacuum energy density can be generated without fine tuning. It is numerically observed that the scalar field dynamics distinguishes fundamental parameters such as the electroweak and strong coupling constants as corresponding to local minima in the dark energy landscape. Chaotic fields can offer possible solutions to the cosmological coincidence problem, as well as to the problem of uniqueness of vacua.Comment: 30 pages, 3 figures. Replaced by final version accepted by Phys. Rev.

    Introduction to “Binary Binds”: Deconstructing Sex and Gender Dichotomies in Archaeological Practice

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    YesGender archaeology has made significant strides toward deconstructing the hegemony of binary categorizations. Challenging dichotomies such as man/woman, sex/gender, and biology/culture, approaches informed by poststructuralist, feminist, and queer theories have moved beyond essentialist and universalist identity constructs to more nuanced configurations. Despite the theoretical emphasis on context, multiplicity, and fluidity, binary starting points continue to streamline the spectrum of variability that is recognized, often reproducing normative assumptions in the evidence. The contributors to this special issue confront how sex, gender, and sexuality categories condition analytical visibility, aiming to develop approaches that respond to the complexity of theory in archaeological practice. The papers push the ontological and epistemological boundaries of bodies, personhood, and archaeological possibility, challenging a priori assumptions that contain how sex, gender, and sexuality categories are constituted and related to each other. Foregrounding intersectional approaches that engage with ambiguity, variability, and difference, this special issue seeks to “de-contain” categories, assumptions, and practices from “binding” our analytical gaze toward only certain kinds of persons and knowledges, in interpretations of the past and practices in the present
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