2,264 research outputs found

    A Redshift Dependent Color-Luminosity Relation in Type 1a Supernovae

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    Type 1a supernova magnitudes are used to fit cosmological parameters under the assumption the model will fit the observed redshift dependence. We test this assumption with the Union 2.1 compilation of 580 sources. Several independent tests find the existing model fails to account for a significant correlation of supernova color and redshift. The correlation of magnitude residuals relative to the ΛCDM\Lambda CDM model and color×redshiftcolor \times redshift has a significance equivalent to 13 standard deviations, as evaluated by randomly shuffling the data. Extending the existing B−VB-V color correction to a relation linear in redshift improves the goodness of fit χ2\chi^{2} by more than 50 units, an equivalent 7-σ\sigma significance, while adding only one parameter. The color−redshiftcolor-redshift correlation is quite robust, cannot be attributed to outliers, and passes several tests of consistency. We review previous hints of redshift dependence in color parameters found in bin-by-bin fits interpreted as parameter bias. We show that neither the bias nor the change Δχ2\Delta \chi^{2} of our study can be explained by those effects. The previously known relation that bluer supernovae have larger absolute luminosity tends to empirically flatten out with increasing redshift. The best-fit cosmological dark energy density parameter is revised from ΩΛ=0.71±0.02 \Omega_{\Lambda} =0.71 \pm 0.02 to ΩΛ=0.74±0.02 \Omega_{\Lambda} = 0.74 \pm 0.02 assuming a flat universe. One possible physical interpretation is that supernovae or their environments evolve significantly with increasing redshift.Comment: 6 pages, 3 figures. Accepted for publication in MNRAS Letters. Contains few corrections and extra added details to 1303.0580v

    Small-X Quarks at HERA Predict the Ultra High Energy Neutrino-Nucleon Cross Section

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    New structure function data at small Bjorken xx from HERA are used along with next-to-leading order QCD evolution to predict a cross section for charged-current interactions of ultrahigh energy neutrinos with nucleons. This new result is over twice the size of previous estimates and has important implications for cosmic ray experiments now underway as well as for KM3 arrays (cubic kilometer-scale neutrino telescopes) now in the planning stages.Comment: KITCS94-9-1, 9 pages (REVTeX) plus 3 postscript figures all uuencode

    The Virgo Alignment Puzzle in Propagation of Radiation on Cosmological Scales

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    We reconsider analysis of data on the cosmic microwave background on the largest angular scales. Temperature multipoles of any order factor naturally into a direct product of axial quantities and cosets. Striking coincidences exist among the axes associated with the dipole, quadrupole, and octupole CMB moments. These axes also coincide well with two other axes independently determined from polarizations at radio and optical frequencies propagating on cosmological scales. The five coincident axes indicate physical correlation and anisotropic properties of the cosmic medium not predicted by the conventional Big Bang scenario. We consider various mechanisms, including foreground corrections, as candidates for the observed correlations. We also consider whether the propagation anomalies may be a signal of ``dark energy'' in the form of a condensed background field. Perhaps {\it light propagation} will prove to be an effective way to look for the effects of {\it dark energy}.Comment: 24 pages, 4 figures, minor changes, no change in result or conclusions. to appear in IJMP

    Analysis Tools for Discovering Strong Parity Violation at Hadron Colliders

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    Several arguments suggest parity violation may be observable in high energy strong interactions. We introduce new analysis tools for describing the azimuthal dependence of multi-particle distributions, or "azimuthal flow." Analysis uses the representations of the orthogonal group O(2) and dihedral groups DND_{N} necessary to define parity correctly in two dimensions. Classification finds that collective angles used in event-by-event statistics represent inequivalent tensor observables that cannot generally be represented by a single "reaction plane". Many new parity-violating observables exist that have never been measured, while many new parity-conserving observables formerly lumped together are now distinguished. We use the concept of "event shape sorting" to suggest separating right- and left-handed events, and we discuss the effects of transverse and longitudinal spin. The analysis tools are statistically robust, and can be applied equally to low or high multiplicity events at the Tevatron, RHICRHIC or RHIC SpinRHIC\, Spin, and the LHCLHC.Comment: 18 pages, 2 figures. Final version, accepted for publication in PRD. Updated references. Modified presentation and discussion of previous wor

    Hadron Helicity Violation in Exclusive Processes: Quantitative Calculations in Leading Order QCD

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    We study a new mechanism for hadronic helicity flip in high energy hard exclusive reactions. The mechanism proceeds in the limit of perfect chiral symmetry, namely without any need to flip a quark helicity. The fundamental feature of the new mechanism is the breaking of rotational symmetry of the hard collision by a scattering plane in processes involving independent quark scattering. We show that in the impulse approximation there is no evidence for of the helicity violating process as the energy or momentum transfer Q2Q^2 is increased over the region 1 GeV^2 < Q^2 < 100 GeV^2. In the asymptotic region Q^2> 1000 GeV^2, a saddle point approximation with doubly logarithmic accuracy yields suppression by a fraction of power of Q^2. ``Chirally--odd" exclusive wave functions which carry non--zero orbital angular momentum and yet are leading order in the high energy limit, play an important role.Comment: uuencoded LaTeX file (21 pages) and PostScript figure

    Connection between the elastic GEp/GMp and P to Delta form factors

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    It is suggested that the falloff in Qsq of the P to Delta magnetic form factor GM* is related to the recently observed falloff of the elastic electric form factor GEp/GMp. Calculation is carried out in the framework of a GPD mechanism

    Indication of Anisotropy in Electromagnetic Propagation over Cosmological Distances

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    We report a systematic rotation of the plane of polarization of electromagnetic radiation propagating over cosmological distances. The effect is extracted independently from Faraday rotation, and found to be correlated with the angular positions and distances to the sources. Monte Carlo analysis yields probabilistic P-values of order 10^(-3) for this to occur as a fluctuation. A fit yields a birefringence scale of order 10^(25) meters. Dependence on redshift z rules out a local effect. Barring hidden systematic bias in the data, the correlation indicates a new cosmological effect.Comment: 5 pages, 1 figure, ReVTeX. For more information, see http://www.cc.rochester.edu/college/rtc/Borge/aniso.htm

    Anisotropy in the Distribution of Galactic Radio Polarizations

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    Radiation traversing the observable universe provides powerful ways to probe anisotropy of electromagnetic propagation. A controversial recent study claimed a signal of dipole character. Here we test a new and independent data set of 361 points under the null proposal of {\it statistical independence} of linear polarization alignments relative to galaxy axes, versus angular positions. The null hypothesis is tested via maximum likelihood analysis of best fits among numerous independent types of factored distributions. We also examine single-number correlations which are parameter free, invariant under coordinate transformations, and distributed very robustly. The statistics are shown explicitly not to depend on the uneven distribution of sources on the sky. We find that the null proposal is not supported at the level of less than 5% to less than 0.1% by several independent statistics. The signal of correlation violates parity, that is, symmetry under spatial inversion, and requires a statistic which transforms properly. The data indicate an axis of correlation, on the basis of likelihood determined to be [R.A.=(0h,9m)±(1h,0m)[{\rm R.A.}=(0^{\rm h},9^{\rm m}) \pm (1^{\rm h},0^{\rm m}), Decl.=−1o±15o]{\rm Decl.} = -1^o\pm 15^o].Comment: 10 pages, Late
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