1,322 research outputs found
Helix surfaces in the special linear group
We characterize helix surfaces (constant angle surfaces) in the special
linear group . In particular, we give an explicit local
description of these surfaces in terms of a suitable curve and a 1-parameter
family of isometries of .Comment: Minor corrections. To appear in Annali di Matematica Pura e
Applicata. arXiv admin note: substantial text overlap with arXiv:1206.127
Biconservative surfaces in BCV-spaces
Biconservative hypersurfaces are hypersurfaces with conservative
stress-energy tensor with respect to the bienergy functional, and form a
geometrically interesting family which includes that of biharmonic
hypersurfaces. In this paper we study biconservative surfaces in the
3-dimensional Bianchi-Cartan-Vranceanu spaces, obtaining their characterization
in the following cases: when they form a constant angle with the Hopf vector
field; when they are SO(2)-invariant.Comment: 12 page
Solar Variability Induced in a Dynamo Code by Realistic Meridional Circulation Variations
In this work we use an already-published method to infer a variation profile for the solar meridional circulation over the last 250 years. We feed this variation profile into a numerical dynamo code, and we reconstruct a sunspot time series that acts as a proxy for solar cycle activity. We perform three simulations with slightly different parameters, and the results are compared with the observational data. The medium and large correlation coefficients between reconstructed and observational time series seem to indicate that variations in meridional circulation play an important role in the modulation of solar activity
Effects of cyclic fluctuations in meridional circulation using a low-order dynamo model
We develop and subsequently explore the solution space of a simple flux transport dynamo model that incorporates a time-dependent large-scale meridional circulation. Based on recent observations, we prescribed an analytical form for the amplitude of this circulation and study its impact in the evolution of the magnetic field. We find that cyclic variations in the amplitude and frequency of the meridional flow affect the strength of the solar cycle. Variations in the amplitude of the fluctuations influence the shape of the solar cycle but are only relevant to the cycle's strength variations when they occur at a frequency different from or out of phase of the solar cycle's
On the effective action of the vacuum photon splitting in Lorentz-violating QED
We consider one-loop radiative corrections from Lorentz- and CPT- violating
extended QED to address the specific problem of finding explicitly an effective
action describing amplitude of photon triple splitting. We show that it is not
possible to find a nonzero photon triple splitting effective action, at least
by using the derivative expansion method (at zero external momenta), up to
leading order in the Lorentz- and CPT- violating parameter.Comment: 4 pages, version to appear in EP
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