18,059 research outputs found
Lagrangian description of world-line deviations
We introduce a Lagrangian which can be varied to give both the equation of
motion and world-line deviations of spinning particles simultaneously.Comment: to appear in IJT
Revolutions and Second-Best Solutions: Education for Sustainable Development in Higher Education
General relativistic spinning fluids with a modified projection tensor
An energy-momentum tensor for general relativistic spinning fluids compatible
with Tulczyjew-type supplementary condition is derived from the variation of a
general Lagrangian with unspecified explicit form. This tensor is the sum of a
term containing the Belinfante-Rosenfeld tensor and a modified perfect-fluid
energy-momentum tensor in which the four-velocity is replaced by a unit
four-vector in the direction of fluid momentum. The equations of motion are
obtained and it is shown that they admit a Friedmann-Robertson-Walker
space-time as a solution.Comment: Submitted to General Relativity and Gravitatio
Does selection for growth rate in broilers affect their resistance and tolerance to Eimeria maxima?
Putative fishery-induced changes in biomass and population size structures of demersal deep-sea fishes in ICES Sub-area VII, Northeast Atlantic Ocean
This work was supported by a series of NERC grants to the principal investigators including NE/C512961/1. The results of the early joint SAMS and IOS surveys were digitized with support from EU MAST Contract MAS2-CT920033 1993–1995, and data analyses was supported by EU FP7 Projects HERMES and HERMIONE. We thank Alain Zuur from Highland Statistics Ltd. for advice with the statistical analyses and Odd Aksel Bergstad for valuable comments that helped to improve the manuscript. We thank the ships’ companies of the RRS Challenger and RRS Discovery.Peer reviewedPublisher PD
Dark matter annihilation and decay profiles for the Reticulum II dwarf spheroidal galaxy
The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most
attractive targets for indirect searches of dark matter. In this work, we
reconstruct the dark matter annihilation (J-factor) and decay profiles for the
newly discovered dSph Reticulum II. Using an optimized spherical Jeans analysis
of kinematic data obtained from the Michigan/Magellan Fiber System (M2FS), we
find Reticulum II's J-factor to be among the largest of any Milky Way dSph. We
have checked the robustness of this result against several ingredients of the
analysis. Unless it suffers from tidal disruption or significant inflation of
its velocity dispersion from binary stars, Reticulum II may provide a unique
window on dark matter particle properties.Comment: 5 pages, 4 figures. Match the ApJL accepted versio
Evaluation of a ln tan integral arising in quantum field theory
We analytically evaluate a dilogarithmic integral that is prototypical of
volumes of ideal tetrahedra in hyperbolic geometry. We additionally obtain new
representations of the Clausen function Cl_2 and the Catalan constant
G=Cl_2(\pi/2), as well as new relations between sine and Clausen function
values.Comment: 24 pages, no figure
Climatically driven loss of calcium in steppe soil as a sink for atmospheric carbon
During the last several thousand years the semi‐arid, cold climate of the Russian steppe formed highly fertile soils rich in organic carbon and calcium (classified as Chernozems in the Russian system). Analysis of archived soil samples collected in Kemannaya Steppe Preserve in 1920, 1947, 1970, and fresh samples collected in 1998 indicated that the native steppe Chernozems, however, lost 17–28 kg m−2 of calcium in the form of carbonates in 1970–1998. Here we demonstrate that the loss of calcium was caused by fundamental shift in the steppe hydrologic balance. Previously unleached soils where precipitation was less than potential evapotranspiration are now being leached due to increased precipitation and, possibly, due to decreased actual evapotranspiration. Because this region receives low levels of acidic deposition, the dissolution of carbonates involves the consumption of atmospheric CO2. Our estimates indicate that this climatically driven terrestrial sink of atmospheric CO2 is ∼2.1–7.4 g C m−2 a−1. In addition to the net sink of atmospheric carbon, leaching of pedogenic carbonates significantly amplified seasonal amplitude of CO2 exchange between atmosphere and steppe soil
The Cooling Flow to Accretion Flow Transition
Cooling flows in galaxy clusters and isolated elliptical galaxies are a
source of mass for fueling accretion onto a central supermassive black hole. We
calculate the dynamics of accreting matter in the combined gravitational
potential of a host galaxy and a central black hole assuming a steady state,
spherically symmetric flow (i.e., no angular momentum). The global dynamics
depends primarily on the accretion rate. For large accretion rates, no simple,
smooth transition between a cooling flow and an accretion flow is possible; the
gas cools towards zero temperature just inside its sonic radius, which lies
well outside the region where the gravitational influence of the central black
hole is important. For accretion rates below a critical value, however, the
accreting gas evolves smoothly from a radiatively driven cooling flow at large
radii to a nearly adiabatic (Bondi) flow at small radii. We argue that this is
the relevant parameter regime for most observed cooling flows. The transition
from the cooling flow to the accretion flow should be observable in M87 with
the {\it Chandra X-ray Observatory}.Comment: emulateapj.sty, 10 pages incl. 5 figures, to appear in Ap
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