69,853 research outputs found

    A First Experimental Limit on In-matter Torsion from Neutron Spin Rotation in Liquid He-4

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    We report the first experimental upper bound to our knowledge on possible in-matter torsion interactions of the neutron from a recent search for parity violation in neutron spin rotation in liquid He-4. Our experiment constrains a coefficient ζ\zeta consisting of a linear combination of parameters involving the time components of the torsion fields TμT^\mu and AμA^\mu from the nucleons and electrons in helium which violates parity. We report an upper bound of ∣ζ∣<9.1x10−23|\zeta|<9.1x10^{-23} GeV at 68% confidence level and indicate other physical processes that could be analyzed to constrain in-matter torsion.Comment: 12 pages, typo correcte

    Simple ultraviolet-based soft-lithography process for fabrication of low-loss polymer polysiloxanes-based waveguides

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    A simple ultraviolet (UV)-based soft-lithography process is used for fabrication of polymer polysiloxanes (PSQ-L) waveguides. The imprint process is first done on the cladding PSQ-LL layer and is followed by a spin-coating step to fill the imprinted features with core PSQ-LH layer material. The optical loss of the straight PSQ-L waveguides is characterised by the Fabry-Perot method for the first time. Even with non-polished facet of the waveguide, the Fabry-Perot resonance spectrum is obtained. An upper limit scattering loss of the waveguide is extracted to be less than 0.8 +/- 0.2 dB/cm for TE mode and 1.3 +/- 0.2 dB/cm for TM mode at 1550 nm. The fully transferred pattern and low scattering loss proves it to be an effective way to replicate low-loss polymer PSQ-L-based waveguides

    Electron beam profile imaging in the presence of coherent optical radiation effects

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    High-brightness electron beams with low energy spread at existing and future x-ray free-electron lasers are affected by various collective beam self-interactions and microbunching instabilities. The corresponding coherent optical radiation effects, e.g., coherent optical transition radiation, render electron beam profile imaging impossible and become a serious issue for all kinds of electron beam diagnostics using imaging screens. Furthermore, coherent optical radiation effects can also be related to intrinsically ultrashort electron bunches or the existence of ultrashort spikes inside the electron bunches. In this paper, we discuss methods to suppress coherent optical radiation effects both by electron beam profile imaging in dispersive beamlines and by using scintillation imaging screens in combination with separation techniques. The suppression of coherent optical emission in dispersive beamlines is shown by analytical calculations, numerical simulations, and measurements. Transverse and longitudinal electron beam profile measurements in the presence of coherent optical radiation effects in non-dispersive beamlines are demonstrated by applying a temporal separation technique.Comment: 12 pages, 11 figures, submitted to Phys. Rev. ST Accel. Beam

    On determination of the geometric cosmological constant from the OPERA experiment of superluminal neutrinos

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    The recent OPERA experiment of superluminal neutrinos has deep consequences in cosmology. In cosmology a fundamental constant is the cosmological constant. From observations one can estimate the effective cosmological constant Λeff\Lambda_{eff} which is the sum of the quantum zero point energy Λdarkenergy\Lambda_{dark energy} and the geometric cosmological constant Λ\Lambda. The OPERA experiment can be applied to determine the geometric cosmological constant Λ\Lambda. It is the first time to distinguish the contributions of Λ\Lambda and Λdarkenergy\Lambda_{dark energy} from each other by experiment. The determination is based on an explanation of the OPERA experiment in the framework of Special Relativity with de Sitter space-time symmetry.Comment: 7 pages, no figure

    Detections of water ice, hydrocarbons, and 3.3um PAH in z~2 ULIRGs

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    We present the first detections of the 3um water ice and 3.4um amorphous hydrocarbon (HAC) absorption features in z~2 ULIRGs. These are based on deep rest-frame 2-8um Spitzer IRS spectra of 11 sources selected for their appreciable silicate absorption. The HAC-to-silicate ratio for our z~2 sources is typically higher by a factor of 2-5 than that observed in the Milky Way. This HAC `excess' suggests compact nuclei with steep temperature gradients as opposed to predominantly host obscuration. Beside the above molecular absorption features, we detect the 3.3um PAH emission feature in one of our sources with three more individual spectra showing evidence for it. Stacking analysis suggests that water ice, hydrocarbons, and PAH are likely present in the bulk of this sample even when not individually detected. The most unexpected result of our study is the lack of clear detections of the 4.67um CO gas absorption feature. Only three of the sources show tentative signs of this feature and at significantly lower levels than has been observed in local ULIRGs. Overall, we find that the closest local analogs to our sources, in terms of 3-4um color, HAC-to-silicate and ice-to-silicate ratios, as well as low PAH equivalent widths are sources dominated by deeply obscured nuclei. Such sources form only a small fraction of ULIRGs locally and are commonly believed to be dominated by buried AGN. Our sample suggests that, in absolute number, such buried AGN are at least an order of magnitude more common at z~2 than today. The presence of PAH suggests that significant levels of star-formation are present even if the obscured AGN typically dominate the power budget.Comment: 39 pages, 14 figures, accepted for publication in Ap
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