5,477 research outputs found
Relationship between Interplanetary Conditions and Changes in the Geomagnetic Field to Understand the Causes of Geomagnetically Induced Currents
Geomagnetically Induced Currents (GICs) are electrical currents induced in ground-level conductive networks, like power lines and pipelines, which can cause costly damage to infrastructure. GICs are induced in response to fast changes in the geomagnetic field (GMF) according to Faraday’s Law of Electromagnetic Induction. The purpose of this study was to identify the parameters of the solar wind and interplanetary shocks which are most strongly correlated with large, fast changes in the magnitude of the GMF. GMF data is 1-min averaged time series of mid- and high-latitude magnetometer measurements in the Sym/H and AL indices, respectively. For solar wind data, I used an existing database of fast-forward interplanetary shocks compiled from measurements made by the WIND spacecraft. I performed t-tests, and created linear fits to determine which parameter(s) are likely responsible for large 1-min changes in the Sym/H and AL indices. Large changes in Sym/H are most strongly correlated with speed jump at the shock and the change in the square root of dynamic pressure and large changes in AL with speed jump at the shock. To determine the causes of events with larger 1-min changes than the fit, I created a subset of shocks which follow the trend with the same distribution as the outliers to find causes for the outliers. This revealed that faster shock and stronger upstream magnetic field are associated with stronger GMF changes
Factorizing -matrices and the XXZ spin-1/2 chain: A diagrammatic perspective
Using notation inherited from the six-vertex model, we construct diagrams
that represent the action of the factorizing -matrices associated to the
finite length XXZ spin-1/2 chain. We prove that these -matrices factorize
the tensor corresponding with elements of the permutation
group. We consider in particular the diagram for the tensor , which cyclically permutes the spin chain. This leads us to a diagrammatic
construction of the local spin operators and in terms of
the monodromy matrix operators.Comment: 26 pages, extra references added, typographical errors correcte
Integrability of the Wess_Zumino-Witten model as a non-ultralocal theory
We consider the 2--dimensional Wess--Zumino--Witten (WZW) model in the
canonical formalism introduced in a previous paper by two of us. Using an
-- matrix approach to non--ultralocal field theories we find the Poisson
algebra of monodromy matrices and of conserved quantities with a new,
non--dynamical, matrix.Comment: Revised version. 3 references added. 13 pages, latex, no figure
Open spin chains with generic integrable boundaries: Baxter equation and Bethe ansatz completeness from SOV
We solve the longstanding problem to define a functional characterization of
the spectrum of the transfer matrix associated to the most general spin-1/2
representations of the 6-vertex reflection algebra for general inhomogeneous
chains. The corresponding homogeneous limit reproduces the spectrum of the
Hamiltonian of the spin-1/2 open XXZ and XXX quantum chains with the most
general integrable boundaries. The spectrum is characterized by a second order
finite difference functional equation of Baxter type with an inhomogeneous term
which vanishes only for some special but yet interesting non-diagonal boundary
conditions. This functional equation is shown to be equivalent to the known
separation of variable (SOV) representation hence proving that it defines a
complete characterization of the transfer matrix spectrum. The polynomial
character of the Q-function allows us then to show that a finite system of
equations of generalized Bethe type can be similarly used to describe the
complete transfer matrix spectrum.Comment: 28 page
Local density dependent potential for compressible mesoparticles
We focus on finding a coarse grained description able to reproduce the
thermodynamic behavior of a molecular system by using mesoparticles
representing several molecules. Interactions between mesoparticles are modelled
by an interparticle potential, and an additional internal equation of state is
used to account for the thermic contribution of coarse grained internal degrees
of freedom. Moreover, as strong non-equilibrium situations over a wide range of
pressure and density are targeted, the internal compressibility of these
mesoparticles has to be considered. This is done by introducing a dependence of
the potential on the local environment of the mesoparticles, either by defining
a spherical local density or by means of a Voronoi tessellation. As an example,
a local density dependent potential is fitted to reproduce the Hugoniot curve
of a model of nitromethane, where each mesoparticle represents one thousand
molecules
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