1,063 research outputs found
Synonymy and stratigraphic ranges of Belemnopsis in the Heterian and Ohauan Stages (Callovian-Tithonian), southwest Auckland, New Zealand.
Belemnopsis stevensi, Belemnopsis maccrawi, and Belemnopsis sp. A (Challinor 1979a) are synonymous; B. stevensi has priority. New belemnite material from Kawhia Harbour and Port Waikato, together with graphical study methods, indicates that many small fragmentary specimens associated with B. stevensi in the lower part of its stratigraphic range are probably the same taxon. B. stevensi has been found only in the Middle and Upper Heterian Stage (Lower Kimmeridgian) at Kawhia and only in the Lower Ohauan Stage (Upper Kimmeridgian) at Port Waikato. This apparently disjunct distribution is attributed to poor exposure in the relevant sections. Belemnopsis kiwiensis n.sp., Belemnopsis cf. sp. B, Belemnopsis sp. B, Belemnopsis sp. D, and Belemnopsis spp. are associated with B. stevensi near the lowest known point in its stratigraphic range. The distribution of stratigraphically useful belemnites within the Heterian and Ohauan Stages is: Conodicoelites spp. (Lower Heterian; correlated with Lower Callovian); Belemnopsis annae (Lower and Middle Heterian; Lower Callovian/Lower Kimmeridgian); Belemnopsis stevensi (Middle Heterian/Lower Ohauan; Kimmeridgian); Belemnopsis keari (Upper Heterian; Kimmeridgian); Belemnopsis trechmanni (Upper Ohauan; Upper Kimmeridgian/Middle Tithonian). The apparently extreme range of Belemnopsis annae remains unexplained. Klondyke Sandstone (new) is recognised as the basal member of Moewaka Formation (Port Waikato area)
Asymmetric Beams and CMB Statistical Anisotropy
Beam asymmetries result in statistically-anisotropic cosmic microwave
background (CMB) maps. Typically, they are studied for their effects on the CMB
power spectrum, however they more closely mimic anisotropic effects such as
gravitational lensing and primordial power asymmetry. We discuss tools for
studying the effects of beam asymmetry on general quadratic estimators of
anisotropy, analytically for full-sky observations as well as in the analysis
of realistic data. We demonstrate this methodology in application to a
recently-detected 9 sigma quadrupolar modulation effect in the WMAP data,
showing that beams provide a complete and sufficient explanation for the
anomaly.Comment: updated to match PRD version + typo correction in Eq. B
(1+3) Covariant Dynamics of Scalar Perturbations in Braneworlds
We discuss the dynamics of linear, scalar perturbations in an almost
Friedmann-Robertson-Walker braneworld cosmology of Randall-Sundrum type II
using the 1+3 covariant approach. We derive a complete set of frame-independent
equations for the total matter variables, and a partial set of equations for
the non-local variables which arise from the projection of the Weyl tensor in
the bulk. The latter equations are incomplete since there is no propagation
equation for the non-local anisotropic stress. We supplement the equations for
the total matter variables with equations for the independent constituents in a
cold dark matter cosmology, and provide solutions in the high and low-energy
radiation-dominated phase under the assumption that the non-local anisotropic
stress vanishes. These solutions reveal the existence of new modes arising from
the two additional non-local degrees of freedom. Our solutions should prove
useful in setting up initial conditions for numerical codes aimed at exploring
the effect of braneworld corrections on the cosmic microwave background (CMB)
power spectrum. As a first step in this direction, we derive the covariant form
of the line of sight solution for the CMB temperature anisotropies in
braneworld cosmologies, and discuss possible mechanisms by which braneworld
effects may remain in the low-energy universe.Comment: 22 pages replaced with additional references and minor corrections in
Revtex4, and accepted for publication in Phys. Rev.
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