2,015 research outputs found

    Leading QCD-induced four-loop contributions to the β\beta-function of the Higgs self-coupling in the SM and vacuum stability

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    We present analytical results for the leading top-Yukawa and QCD contribution to the β\beta-function for the Higgs self-coupling λ\lambda of the Standard Model at four-loop level, namely the part yt4gs6\propto y_t^4 g_s^6 independently confirming a result given in [1]. We also give the contribution yt2gs6\propto y_t^2 g_s^6 of the anomalous dimension of the Higgs field as well as the terms ytgs8\propto y_t g_s^8 to the top-Yukawa β\beta-function which can also be derived from the anomalous dimension of the top quark mass. We compare the results with the RG functions of the correlators of two and four scalar currents in pure QCD and find a new relation between the anomalous dimension γ0\gamma_0 of the QCD vacuum energy and the anomalous dimension γmSS\gamma_m^{SS} appearing in the RG equation of the correlator of two scalar currents. Together with the recently computed top-Yukawa and QCD contributions to βgs\beta_{g_s} [2,3] the β\beta-functions presented here constitute the leading four-loop contributions to the evolution of the Higgs self-coupling. A numerical estimate of these terms at the scale of the top-quark mass is presented as well as an analysis of the impact on the evolution of λ\lambda up to the Planck scale and the vacuum stability problem.Comment: v2: This is the version accepted by JHEP; extended discussion of the numerics and vacuum stability analysis; references added; plot adde

    Four-loop renormalization of QCD with a reducible fermion representation of the gauge group: anomalous dimensions and renormalization constants

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    We present analytical results at four-loop level for the renormalization constants and anomalous dimensions of an extended QCD model with one coupling constant and an arbitrary number of fermion representations. One example of such a model is the QCD plus gluinos sector of a supersymmetric theory where the gluinos are Majorana fermions in the adjoint representation of the gauge group. The renormalization constants of the gauge boson, ghost and fermion fields are analytically computed as well as those for the ghost-gluon vertex, the fermion-gluon vertex and the fermion mass. All other renormalization constants can be derived from these. Some of these results were already produced in Feynman gauge for the computation of the beta-function of this model, which was recently published. Here we present results for an arbitrary gauge parameter.Comment: v2: version accepted by JHEP, extended discussion of the treatment of Majorana spinor

    Avenues and incentives for commercial use of a low-gravity environment

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    The scientific and commercial utilization of the low-g environments for materials research and for process and product development is considered. Any products of commercial interest which necessitate processing in space will probably be low volume, high value items. To encourage the commercialization of materials processing in low-g, NASA, in parallel with establishing and demonstrating the scientific/technological precepts for analyzing and using a low-g environment, is establishing the legal and management mechanisms to share in the cost and risk of early commercial ventures, and is now working with commercial firms on a case-by basis to explore applications of this new technology to specific needs of the company

    Commercialization of Materials Processing in Space

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    The primary motivation of the Materials Processing in Space program is the scientific and commercial utilization of the effects of the unique environments of space on material processes. The reduction or elimination of the pervasive influences of gravity on Earth-based process mechanisms affords opportunities for understanding and improving ground-based processing or producing select materials in space which, typically, would be of low volume, high value commercial interest. Additionally, the unlimited, if not hard vacuum of space affords equally interesting influences on material processes. To evolve the commercialization of Materials Processing in Space, the program seeks to establish and demonstrate the scientific/technological precepts for analyzing and using the space environment and, in parallel, to establish the legal and management mechanisms to implement commercial ventures

    Cavity-assisted squeezing of a mechanical oscillator

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    We investigate the creation of squeezed states of a vibrating membrane or a movable mirror in an opto-mechanical system. An optical cavity is driven by squeezed light and couples via radiation pressure to the membrane/mirror, effectively providing a squeezed heat-bath for the mechanical oscillator. Under the conditions of laser cooling to the ground state, we find an efficient transfer of squeezing with roughly 60% of light squeezing conveyed to the membrane/mirror (on a dB scale). We determine the requirements on the carrier frequency and the bandwidth of squeezed light. Beyond the conditions of ground state cooling, we predict mechanical squashing to be observable in current systems.Comment: 7.1 pages, 3 figures, submitted to PR

    Opto-mechanical transducers for long-distance quantum communication

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    We describe a new scheme to interconvert stationary and photonic qubits which is based on indirect qubit-light interactions mediated by a mechanical resonator. This approach does not rely on the specific optical response of the qubit and thereby enables optical quantum interfaces for a wide range of solid state spin and charge based systems. We discuss the implementation of quantum state transfer protocols between distant nodes of a large scale network and evaluate the effect of the main noise sources on the resulting state transfer fidelities. For the specific examples of electronic spin qubits and superconducting charge qubits we show that high fidelity quantum communication protocols can be implemented under realistic experimental conditions.Comment: Version as accepted by PR

    Paper Session I-A - Advanced Solid Rocket Motor (ASRM)

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    The Advanced Solid Rocket Motor (ASRM) is a150-in. diameter segmented motor design that incorporates substantive design changes to improve the reliability and design safety margins of the space shuttle system. The new motor thrust characteristics are tailored to preclude the necessity for throttling the Space Shuttle Main Engines (SSME) during the period of maximum dynamic pressure. This reduces or eliminates about 175 criticality 1/1R failure modes for the shuttle system. Furthermore, the ASRM is designed to provide a 12,000 Ib payload improvement which will support space station development and other critical NASA missions. To achieve the level of process control and automation needed for high quality, reproducibility, and improved reliability, NASA concluded that a substantially new modern, fully-automated facility is required. Sites selected to produce and test the ASRM are the TVA Yellow Creek Mississippi site and the Stennis Space Center site, respectively. The ASRM design/program evolved from Phase A studies conducted in late 1986 and Phase B studies conducted from mid-1987 to April 1988. All major solid propulsion contractors participated in these studies. The study results culminated in the release of an ASRM Request for Proposals (phase C/D) October 31, 1988. Authority to proceed (ATP) with the Development and Verification Program is currently planned for April 1, 1989, with the first ASRM Shuttle development flight tentatively scheduled for late 1994
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