10 research outputs found
Magnetic Helicity Conservation and Inverse Energy Cascade in Electron Magnetohydrodynamic Wave Packets
Electron magnetohydrodynamics (EMHD) provides a fluid-like description of
small-scale magnetized plasmas. An EMHD wave (also known as whistler wave)
propagates along magnetic field lines. The direction of propagation can be
either parallel or anti-parallel to the magnetic field lines. We numerically
study propagation of 3-dimensional (3D) EMHD wave packets moving in one
direction. We obtain two major results: 1. Unlike its magnetohydrodynamic (MHD)
counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave
packets traveling in one direction create opposite traveling wave packets via
self-interaction and cascade energy to smaller scales. 2. EMHD wave packets
traveling in one direction clearly exhibit inverse energy cascade. We find that
the latter is due to conservation of magnetic helicity. We compare inverse
energy cascade in 3D EMHD turbulence and 2-dimensional (2D) hydrodynamic
turbulence.Comment: Phys. Rev. Lett., accepted (4pages, 4 figures
A little inflation at the cosmological QCD phase transition
We reexamine the recently proposed "little inflation" scenario that allows
for a strong first order phase-transition of QCD at non-negligible baryon
number in the early universe and its possible observable consequences. The
scenario is based on the assumptions of a strong mechanism for baryogenesis and
a quasistable QCD-medium state which triggers a short inflationary period of
inflation diluting the baryon asymmetry to the value observed today. The
cosmological implications are reexamined, namely effects on primordial density
fluctuations up to dark matter mass scales of M_{max} \sim 1 M_{\astrosun},
change in the spectral slope up to M_{max} \sim 10^6 M_{\astrosun},
production of seeds for the present galactic and extragalactic magnetic fields
and a gravitational wave spectrum with a peak frequency around . We discuss the issue of nucleation in more detail and
employ a chiral effective model of QCD to study the impact on small scale
structure formation.Comment: 18 pages, 12 figures, several extensions to the text and structure
formation part was rephrased for better readabilit
Two-Loop Corrections to Higgs Production at LEP
We evaluate the two-loop correction to the
coupling in the Standard Model by means of a low-energy theorem, assuming that
the top quark is much heavier than the Higgs boson. We then construct a
heavy-top-quark effective Lagrangian for the interaction that
accommodates the and
corrections and derive from it the corresponding corrections to the
decay as well as those to Higgs-boson production at LEP1, via ,
and at LEP2, via . In all cases, the leading
terms are considerably screened by their QCD corrections, if the on-shell
renormalization scheme with as a basic parameter is employed.Comment: 11 pages, latex, no figure
CKM Matrix and Standard-Model CP Violation
The currently favored model of CP violation is based on phases in the
Cabibbo-Kobayashi-Maskawa (CKM) matrix describing the weak charge-changing
couplings of quarks. The present status of parameters of this matrix is
described. Tests of the theory, with particular emphasis on the study of B
meson decays, are then noted. Some remarks are made regarding the possible
origin of the baryon asymmetry of the universe; the corresponding coupling
pattern of the leptons could shed light on the question. Some possibilities for
non-standard physics are discussed.Comment: 16 pages, latex, 8 figures. Invited talk at Fourth KEK Topical
Conference on Flavour Physics, 29 -- 31 October 1996. To be published in
Nucl. Phys. B (Proc. Suppl.