2,108 research outputs found
Energy and volume of vector fields on spherical domains
We present in this paper a \boundary version" for theorems about minimality
of volume and energy functionals on a spherical domain of threedimensional
Euclidean sphere
The utility of surface magnetic field measurements in the MAGSAT program
To take full advantage of the global, vector, survey by the Magsat satellite, and international program of augmented surface measurements was proposed. For secular variation and upper mantle conductivity the proposed measurements are global. The repeat station measurements for secular variation should be occupied at 2-3 year intervals. A special observing period in November and December of 1979 is proposed during which simultaneous, continuous, global measurements for upper mantle conductivity studies are to be gathered. Finally, it is recommended that the networks in operation during the IMS extend their operation through the Fall of 1980 to provide correlative data useful for high latitude disturbance studies and for crustal conductivity studies
On the 2D Dirac oscillator in the presence of vector and scalar potentials in the cosmic string spacetime in the context of spin and pseudospin symmetries
The Dirac equation with both scalar and vector couplings describing the
dynamics of a two-dimensional Dirac oscillator in the cosmic string spacetime
is considered. We derive the Dirac-Pauli equation and solve it in the limit of
the spin and the pseudo-spin symmetries. We analyze the presence of cylindrical
symmetric scalar potentials which allows us to provide analytic solutions for
the resultant field equation. By using an appropriate ansatz, we find that the
radial equation is a biconfluent Heun-like differential equation. The solution
of this equation provides us with more than one expression for the energy
eigenvalues of the oscillator. We investigate these energies and find that
there is a quantum condition between them. We study this condition in detail
and find that it requires the fixation of one of the physical parameters
involved in the problem. Expressions for the energy of the oscillator are
obtained for some values of the quantum number . Some particular cases which
lead to known physical systems are also addressed.Comment: 15 pages, 8 figures, matches published versio
Decomposition of stochastic flows with automorphism of subbundles component
We show that given a -structure on a differentiable manifold , if
the group of automorphisms of is big enough, then there exists the
quotient of an stochastic flows by , in the sense that where , the remainder has
derivative which is vertical but transversal to the fibre of . This
geometrical context generalizes previous results where is a Riemannian
manifold and is decomposed with an isometric component, see Liao
\cite{Liao1} and Ruffino \cite{Ruffino}, which in our context corresponds to
the particular case of an SO(n)-structure on .Comment: To appear in Stochastics and Dynamics, 201
A stochastic approach to the closure of accessible sets of control systems with application on homogeneous spaces
Given a control system on a compact manifold M, we study conditions for the foliation defined by the accessible sets to be dense in M. For this, we relate the control system to a stochastic differential equation and, by the support theorem, we give a characterization of the density in terms of the infinitesimal generator of the diffusion and its invariant measures.33351953
Initial geomagnetic field model from MAGSAT
Magsat data from magnetically quiet days were used to derive a thirteenth degree and order spherical harmonic geomagnetic field model, MGST(3/80). The model utilized both scalar and vector data and fit that data with standard deviations of 8, 52, 55 and 97 nT for the scalar magnitude, B sub r, B sub theta and B sub phi respectively. When compared with earlier models, the Earth's dipole moment continues to decrease at a rate of about 26 nT/year. Evaluation of earlier models with Magsat data shows that the scalar field at the Magsat epoch is best predicted by the POGO(2/72) model but that the AWC/75 and IGS/75 are better for predicting vector fields
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