2,264 research outputs found
A Redshift Dependent Color-Luminosity Relation in Type 1a Supernovae
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 model and has a
significance equivalent to 13 standard deviations, as evaluated by randomly
shuffling the data. Extending the existing color correction to a relation
linear in redshift improves the goodness of fit by more than 50
units, an equivalent 7- significance, while adding only one parameter.
The 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
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 to 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
New structure function data at small Bjorken 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
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
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 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, or , and the .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
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 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
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
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
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 , .Comment: 10 pages, Late
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