73 research outputs found
Universal properties of three-dimensional magnetohydrodynamic turbulence: Do Alfv\'en waves matter?
We analyse the effects of the propagating Alfv\'en waves, arising due to
non-zero mean magnetic fields, on the nonequilibrium steady states of
three-dimensional (3d) homogeneous Magnetohydrodynamic (MHD) turbulence. In
particular, the effects of Alfv\'en waves on the universal properties of 3dMHD
turbulence are studied in a one-loop self-consistent mode-coupling approach. We
calculate the kinetic- and magnetic energy-spectra. We find that {\em even} in
the presence of a mean magnetic field the energy spectra are Kolmogorov-like,
i.e., scale as in the inertial range where is a Fourier
wavevector belonging to the inertial range. We also elucidate the multiscaling
of the structure functions in a log-normal model by evaluating the relevant
intermittency exponents, and our results suggest that the multiscaling
deviations from the simple Kolmogorov scaling of the structure functions
decrease with increasing strength of the mean magnetic field. Our results
compare favourably with many existing numerical and observational results.Comment: To appear in JSTAT (2005
The dynamo effect - A dynamic renormalisation group approach
The Dynamo effect is used to describe the generation of magnetic fields in
astrophysical objects. However, no rigorous derivation of the dynamo equation
is available. We justify the form of the equation using an Operator Product
Expansion (OPE) of the relevant fields. We also calculate the coefficients of
the OPE series using a dynamic renormalisation group approach and discuss the
time evolution of the initial conditions on the initial seed magnetic field.Comment: submitted to EP
Dynamical Structure Factor of Fulde-Ferrell-Larkin-Ovchinnikov Superconductors
Superconductor with a spatially-modulated order parameter is known as
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor. Using the
time-dependent Ginzburg-Landau (TDGL) formalism we have theoretically studied
the temporal behaviour of the equal-time correlation function, or the structure
factor, of a FFLO superconductor following a sudden quench from the unpaired,
or normal, state to the FFLO state. We find that quenching into the ordered
FFLO phase can reveal the existence of a line in the mean-field phase diagram
which cannot be accessed by static properties.Comment: 2 pages, Poster presented at 57TH DAE SOLID STATE PHYSICS SYMPOSIUM,
2012. Mainly based on arXiv:1210.220
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