We calculate all the four-photon helicity amplitudes at the one-loop level in a massive theory using multiple-cut methods. The amplitudes are derived in scalar QED, QED and QED theories. We will see the origin of rational terms. We extend the calculation to the simplest six-photon helicity amplitude where all photons have the same helicity.

Helicity transfer in a shell model of turbulence is investigated. In particular, we study the scaling behavior of helicity transfer in a dynamical model of turbulence lacking inversion symmetry. We present some phenomenological and numerical support to the idea that Helicity becomes -at scale small enougha passively-advected quantity. “oυτoι συνǫχθǫιν, αλλα συμφιλǫιν ǫφυν” ANTIΓONH “non sono na...

STUDY OF MAGNETIC HELICITY IN SOLAR ACTIVE REGIONS AND ITS RELATIONSHIP WITH SOLAR ERUPTIONS by Sung-Hong Park It is generally believed that eruptive phenomena in the solar atmosphere such as solar flares and coronal mass ejections (CMEs) occur in solar active regions with complex magnetic structures. The magnetic complexity is quantified in terms of twists, kinks, and interlinkages of magnetic...

The change of helicity for magnetic reconnection is calculated with the help of a kinematic model. The results connrm the approximate conservation of magnetic helicity for reconnection in an almost ideal plasma as e. g. the solar corona. Diierent examples show the contributions of twist or linkage of ux tubes to the total helicity change in the process. However, they also show that helicity may...

The role of magnetic helicity in astrophysical large-scale dynamos is reviewed and compared with cases where there is no energy supply and an initial magnetic field can only decay. In both cases magnetic energy tends to get redistributed to larger scales. Depending on the efficiency of magnetic helicity fluxes, the decay of a helical field can speed up. Likewise, the saturation of a helical dyn...

Mass currents in astrophysics generate gravitomagnetic fields of enormous complexity. Gravitomagnetic helicity, direct analogy with magnetic is a measure entwining the field lines. We discuss helicity within gravitoelectromagnetic (GEM) framework linearized general relativity. Furthermore, we employ spacetime curvature approach to GEM order determine for static observers Kerr spacetime.

Kinetic helicity is one of the invariants of the Euler equations that is associated with the topology of vortex lines within the fluid. In superfluids, the vorticity is concentrated along vortex filaments. In this setting, helicity would be expected to acquire its simplest form. However, the lack of a core structure for vortex filaments appears to result in a helicity that does not retain its k...

Helicity was calculated in Hurricane Bonnie (1998) using tropospheric-deep dropsonde soundings from the NASA Convection and Moisture Experiment. Large helicity existed downshear of the storm center with respect to the ambient vertical wind shear. It was associated with veering, semicircular hodographs created by strong, vortex-scale, radial-vertical flow induced by the shear. The most extreme v...

Helicity was calculated in Hurricane Bonnie (1998) using tropospheric-deep dropsonde soundings from the Convection and Moisture Experiment conducted by NASA. Large helicity existed downshear of the storm center with respect to the ambient vertical wind shear. It was associated with veering, semi-circular hodographs created by strong, vortex-scale, radial-vertical flow induced by the shear. The ...

We extend the Kolmogorov phenomenology for the scaling of energy spectra in high-Reynolds-number turbulence, to explicitly include the effect of helicity. There exists a time scale tau(H) for helicity transfer in homogeneous, isotropic turbulence with helicity. We arrive at this time scale using the phenomenological arguments used by Kraichnan to derive the time scale tau(E) for energy transfer...