5,736 research outputs found
Mechanistic Links Between the Sedimentary Redox Cycle and Marine Acid-Base Chemistry
The redox state of Earth's surface is controlled on geological timescales by the flow of electrons through the sedimentary rock cycle, mediated largely by the weathering and burial of CâSâFe phases. These processes buffer atmospheric pOâ. At the same time, COâ influxes and carbonate burial control seawater acidâbase chemistry and climate over long timescales via the carbonateâsilicate cycle. However, these two systems are mechanistically linked and impact each other via charge balance in the hydrosphere. Here, we use a lowâorder Earth system model to interrogate a subset of these connections, with a focus on changes that occur during perturbations to electron flow through the sedimentary rock cycle. We show that the net oxidation or reduction of the Earth's surface can play an important role in controlling acidâbase processes in the oceans and thus climate, and suggest that these links should be more fully integrated into interpretive frameworks aimed at understanding Earth system evolution throughout Precambrian and Phanerozoic time
Symmetry energy in nuclear density functional theory
The nuclear symmetry energy represents a response to the neutron-proton
asymmetry. In this survey we discuss various aspects of symmetry energy in the
framework of nuclear density functional theory, considering both
non-relativistic and relativistic self-consistent mean-field realizations
side-by-side. Key observables pertaining to bulk nucleonic matter and finite
nuclei are reviewed. Constraints on the symmetry energy and correlations
between observables and symmetry-energy parameters, using statistical
covariance analysis, are investigated. Perspectives for future work are
outlined in the context of ongoing experimental efforts.Comment: 14 pages, 8 figures, submitted to the Special EPJA Issue on "Symmetry
Energy
Central depression in nuclear density and its consequences for the shell structure of superheavy nuclei
The influence of the central depression in the density distribution of
spherical superheavy nuclei on the shell structure is studied within the
relativistic mean field theory. Large depression leads to the shell gaps at the
proton Z=120 and neutron N=172 numbers, while flatter density distribution
favors N=184 for neutrons and leads to the appearance of a Z=126 shell gap and
to the decrease of the size of the Z=120 shell gap. The correlations between
the magic shell gaps and the magnitude of central depression are discussed for
relativistic and non-relativistic mean field theories.Comment: 5 page
B-Spline Finite Elements and their Efficiency in Solving Relativistic Mean Field Equations
A finite element method using B-splines is presented and compared with a
conventional finite element method of Lagrangian type. The efficiency of both
methods has been investigated at the example of a coupled non-linear system of
Dirac eigenvalue equations and inhomogeneous Klein-Gordon equations which
describe a nuclear system in the framework of relativistic mean field theory.
Although, FEM has been applied with great success in nuclear RMF recently, a
well known problem is the appearance of spurious solutions in the spectra of
the Dirac equation. The question, whether B-splines lead to a reduction of
spurious solutions is analyzed. Numerical expenses, precision and behavior of
convergence are compared for both methods in view of their use in large scale
computation on FEM grids with more dimensions. A B-spline version of the object
oriented C++ code for spherical nuclei has been used for this investigation.Comment: 27 pages, 30 figure
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