arXiv subjects

Leonardo Campanelli

Publications and source records attributed to Leonardo Campanelli.

23 records · Page 2Linked to original sources

arXiv2007

Evolution of Magnetic Fields in Freely Decaying Magnetohydrodynamic Turbulence

We study the evolution of magnetic fields in freely decaying magnetohydrodynamic turbulence. By quasi-linearizing the Navier-Stokes equation, we solve analytically the induction equation in quasi-normal approximation. We find that, if the magnetic field is not helical, the magnetic energy and correlation length evolve in time respectively as E_B \propto t^{-2(1+p)/(3+p)} and ξ_B \propto t^{2/(3+p)}, where p is the index of initial power-law spectrum. In the helical case, the magnetic helicity is an almost conserved quantity and forces the magnetic energy and correlation length to scale as E_B \propto (log t)^{1/3} t^{-2/3} and ξ_B \propto (log t)^{-1/3} t^{2/3}.

astro-ph↗

arXiv2006

Primordial Magnetic Fields and the Peccei-Quinn Scale

A strong primordial magnetic field can induce a relaxation of the present bound on the PQ-constant. We show that, considering the present limits on primordial magnetic fields, a value for the PQ-constant very close to the GUT scale is not excluded. This result naturally opens the possibility for the axion to be defined in the context of the GUT theories.

astro-ph↗

arXiv2006

Baryogenesis and CP-Violating Domain Walls in the Background of a Magnetic Field

Within the domain wall-mediated electroweak baryogenesis, we study fermion scattering off a CP-violating wall in the background of an uniform magnetic field. In particular, we calculate the asymmetry between the reflection coefficients for right-handed and left-handed chiral fermions, ΔR = R_{R \to L} - R_{L \to R}, which is of relevance to non local baryogenesis mechanisms.

astro-ph↗

arXiv2004

Scattering of Dirac and Majorana Fermions off Domain Walls

We investigate the interaction of fermions having both Dirac and left-handed and right-handed Majorana mass terms with vacuum domain walls. By solving the equations of motion in thin-wall approximation, we calculate the reflection and transmission coefficients for the scattering of fermions off walls.

hep-ph↗

arXiv2004

Scaling Laws in Magnetohydrodynamic Turbulence

We analyze the decay laws of the kinetic and magnetic energies and the evolution of correlation lengths in freely decaying incompressible magnetohydrodynamic (MHD) turbulence. Scale invariance of MHD equations assures that, in the case of constant dissipation parameters ({\it i.e.} kinematic viscosity and resistivity) and null magnetic helicity, the kinetic and magnetic energies decay in time as $E \sim t^{-1}$, and the correlation lengths evolve as $ξ\sim t^{1/2}$. In the helical case, assuming that the magnetic field evolve towards a force-free state, we show that (in the limit of large magnetic Reynolds number) the magnetic helicity remains constant, the kinetic and magnetic energies decay as $E_v \sim t^{-1}$ and $E_B \sim t^{-1/2}$ respectively, while both the kinetic and magnetic correlation lengths grow as $ξ\sim t^{1/2}$.

astro-ph↗