Anomalous scaling, nonlocality, and anisotropy in a model of the passively advected vector field

LT Adzhemyan, NV Antonov, AV Runov - Physical Review E, 2001 - APS
LT Adzhemyan, NV Antonov, AV Runov
Physical Review E, 2001APS
A model of the passive vector quantity advected by the Gaussian velocity field with the
covariance∝ δ (t− t′)| x− x′| ɛ is studied; the effects of pressure and large-scale
anisotropy are discussed. The inertial-range behavior of the pair correlation function is
described by an infinite family of scaling exponents, which satisfy exact transcendental
equations derived explicitly in d dimensions by means of the functional techniques. The
exponents are organized in a hierarchical order according to their degree of anisotropy, with …
Abstract
A model of the passive vector quantity advected by the Gaussian velocity field with the covariance∝ δ (t− t′)| x− x′| ɛ is studied; the effects of pressure and large-scale anisotropy are discussed. The inertial-range behavior of the pair correlation function is described by an infinite family of scaling exponents, which satisfy exact transcendental equations derived explicitly in d dimensions by means of the functional techniques. The exponents are organized in a hierarchical order according to their degree of anisotropy, with the spectrum unbounded from above and the leading (minimal) exponent coming from the isotropic sector. This picture extends to higher-order correlation functions. Like in the scalar model, the second-order structure function appears nonanomalous and is described by the simple dimensional exponent: S 2∝ r 2− ɛ. For the higher-order structure functions, S 2 n∝ r n (2− ɛ)+ Δ n, the anomalous scaling behavior is established as a consequence of the existence in the corresponding operator product expansions of “dangerous” composite operators, whose negative critical dimensions determine the anomalous exponents Δ n< 0. A close formal resemblance of the model with the stirred Navier-Stokes equation reveals itself in the mixing of relevant operators and is the main motivation of the paper. Using the renormalization group, the anomalous exponents are calculated in the O (ɛ) approximation, in large d dimensions, for the even structure functions up to the twelfth order.
American Physical Society
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