41 research outputs found
Thermally activated Hall creep of flux lines from a columnar defect
We analyse the thermally activated depinning of an elastic string (line
tension ) governed by Hall dynamics from a columnar defect modelled
as a cylindrical potential well of depth for the case of a small
external force An effective 1D field Hamiltonian is derived in order to
describe the 2D string motion. At high temperatures the decay rate is
proportional to with a constant of order of the
critical force and U(F) \sim{\left ({\epsilon V_{0}})}^{{1}/{2}}{V_{0}/{F}}
the activation energy. The results are applied to vortices pinned by columnar
defects in superclean superconductors.Comment: 12 pages, RevTeX, 2 figures inserte
Two-Loop O(alpha_s G_F M_Q^2) Heavy-Quark Corrections to the Interactions between Higgs and Intermediate Bosons
By means of a low-energy theorem, we analyze at O(alpha_s G_F M_Q^2) the
shifts in the Standard-Model W^+W^-H and ZZH couplings induced by virtual
high-mass quarks, Q, with M_Q >> M_Z, M_H, which includes the top quark.
Invoking the improved Born approximation, we then find the corresponding
corrections to various four- and five-point Higgs-boson production and decay
processes which involve the W^+W^-H and ZZH vertices with one or both of the
gauge bosons being connected to light-fermion currents, respectively. This
includes e^+e^- -> f anti-f H via Higgs-strahlung, via W^+W^- fusion (with f =
nu_e), and via ZZ fusion (with f = e), as well as H -> 2V -> 4f (with V = W,
Z).Comment: 20 pages (Latex); Physical Review D (to appear
Magnetic Field Amplification in Galaxy Clusters and its Simulation
We review the present theoretical and numerical understanding of magnetic
field amplification in cosmic large-scale structure, on length scales of galaxy
clusters and beyond. Structure formation drives compression and turbulence,
which amplify tiny magnetic seed fields to the microGauss values that are
observed in the intracluster medium. This process is intimately connected to
the properties of turbulence and the microphysics of the intra-cluster medium.
Additional roles are played by merger induced shocks that sweep through the
intra-cluster medium and motions induced by sloshing cool cores. The accurate
simulation of magnetic field amplification in clusters still poses a serious
challenge for simulations of cosmological structure formation. We review the
current literature on cosmological simulations that include magnetic fields and
outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure