706 research outputs found
Renormalization-group approach to the stochastic Navier--Stokes equation: Two-loop approximation
The field theoretic renormalization group is applied to the stochastic
Navier--Stokes equation that describes fully developed fluid turbulence. The
complete two-loop calculation of the renormalization constant, the
function, the fixed point and the ultraviolet correction exponent is performed.
The Kolmogorov constant and the inertial-range skewness factor, derived to
second order of the \eps expansion, are in a good agreement with the
experiment. The possibility of the extrapolation of the \eps expansion beyond
the threshold where the sweeping effects become important is demonstrated on
the example of a Galilean-invariant quantity, the equal-time pair correlation
function of the velocity field. The extension to the -dimensional case is
briefly discussed.Comment: 20 pages, 3 figure
Premartensitic Transition in Ni2+xMn1-xGa Heusler Alloys
The temperature dependencies of the resistivity and magnetization of a series
of Ni2+XMn1-XGa (X = 0 - 0.09) alloys were investigated. Along with the
anomalies associated with ferromagnetic and martensitic transitions,
well-defined anomalies were observed at the temperature of premartensitic
transformation. The premartensitic phase existing in a temperature range 200 -
260 K in the stoichiometric Ni2MnGa is suppressed by the martensitic phase with
increasing Ni content and vanishes in Ni2.09Mn0.91Ga composition
The Cosmological Gene Project: cluster analysis of the atmospheric fluctuations on arcmin-scale imaging of the Cosmic Microwave Background
We discuss some aspects of the Cosmological Gene Project started at the
Special Astrophysical Observatory (Russia) in 1999. The goal of the project is
to measure the anisotropy and polarization of the Cosmic Microwave Background
(CMB) and investigation of atmospheric fluctuations and foreground on
arcmin-scales using the radio-telescope RATAN-600. We develop the cluster
analysis of one-dimensional random fields for the application to the RATAN-600
scans. We analyze the specific properties of peak clusterisation in the
RATAN-600 scans which to separate the primordial CMB signal from noise.Comment: Submitted to Astronomy & Astrophysic
O(1/N_f) Corrections to the Thirring Model in 2<d<4
The Thirring model, that is, a relativistic field theory of fermions with a
contact interaction between vector currents, is studied for dimensionalities
2<d<4 using the 1/N_f expansion, where N_f is the number of fermion species.
The model is found to have no ultraviolet divergences at leading order provided
a regularization respecting current conservation is used. Explicit O(1/N_f)
corrections are computed, and the model shown to be renormalizable at this
order in the massless limit; renormalizability appears to hold to all orders
due to a special case of Weinberg's theorem. This implies there is a universal
amplitude for four particle scattering in the asymptotic regime. Comparisons
are made with both the Gross-Neveu model and QED.Comment: 22 pages in plain TeX, with 7 figs included using psfig.tex (Minor
conceptual changes - algebra unaffected
- …