We investigate the dynamo problem in the limit of small magnetic Prandtl number (Pm) using a shell model of magnetohydrodynamic turbulence. The model is designed to satisfy conservation laws of total energy, cross helicity and magnetic helicity in the limit of inviscid fluid and null magnetic diffusivity. The forcing is chosen to have a constant injection rate of energy and no injection of kine...

The motto of high energy QCD is the quark helicity conservation which is often believed to entail the s-channel helicity conservation (SCHC) at small x. Here I review the recent work ([ 1, 2, 3, 4, 5], which shows this belief is groundless and there is an extremely rich helicity-flip physics at small x. The backbone of DIS is the Compton scattering (CS) γ μp → γ ∗ ′ ν p , which at small-x can b...

A gauge-invariant and hence physically meaningful definition of magnetic helicity density for random fields is proposed, using the Gauss linking formula, as the density of correlated field line linkages. This definition is applied to the random small-scale field in weakly inhomogeneous turbulence, whose correlation length is small compared with the scale on which the turbulence varies. For inho...

Electrons emitted in the radiative decay μ− → e−ν̄eνμγ have a significant probability of being right-handed, even in the limit me → 0. Such “wrong-helicity” electrons, arising from helicity-flip bremsstrahlung, contribute an amount α 4π Γ0 to the muon decay width (Γ0 ≡ G 2 Fm 5 μ/(192π )). We use the helicity-flip splitting function Dhf (z) of Falk and Sehgal (Phys. Lett. B 325, 509 (1994)) to o...

Magnetic field relaxation is determined by both the field’s geometry and its topology. For relaxation processes, however, it turns out that its topology is a much more stringent constraint. As quantifier for the topology we use magnetic helicity and test whether it is a stronger condition than the linking of field lines. Further, we search for evidence of other topological invariants, which giv...

V13K, a 26-residue peptide, has been shown to have strong antimicrobial activity, negligible hemolytic activity, and significant anticancer activity. In the present work, V13K was used as the framework to investigate the influence of helicity, as influenced by d-amino acid substitutions in the center of the peptide polar and non-polar faces of the amphipathic helix, on biological activity. The ...

To fix the notation, let us start by giving some details on the helicity eigenstates basis. The helicity operator is defined as S = [p̂⇥ ~ ]z and its eigenstates, |ksi, with s = ±1, satisfy the relation S|k±i = ±|k±i. A simple calculation shows in particular that |k±i can be expressed in terms of the standard spin eigenstates, |k "i and |k #i, as |k±i = (exp ( i✓k)|k "i± i|k #i)/ p 2 with ✓k = a...