Construction of a perturbatively correct light-front Hamiltonian for a (2+1)-dimensional gauge theory

We discuss a perturbation theory on the light front regularized by a method analogous to Pauli–Villars regularization for the (2+1)-dimensional SU(N)-symmetric gauge theory. This allows constructing a correct renormalized light-front Hamiltonian.     

Study of the higher-order asymptotic behavior of quantum field expansions in the theory of two-dimensional fully developed turbulence

We use a simplified (0+1)-dimensional theory to develop approaches for studying the higher-order asymptotic behavior of quantum field expansions in the two-dimensional theory of fully developed turbulence. We consider the asymptotic behavior of the correlation function in the small-time limit in the theory of fully developed turbulence and derive and investigate the stationarity equation. We show that the perturbation series in this limit has a finite convergence radius.     

Composite operators,operator expansion,and Galilean invariance in the theory of fully developed turbulence. Infrared corrections to Kolmogorov scaling

The quantum-field renormalization group and operator expansion are used to investigate the infrared asymptotic behavior of the velocity correlation function in the theory of fully developed turbulence. The scaling dimensions of all composite operators constructed from the velocity field and its time derivatives are calculated, and their contributions to the operator expansion are determined. It is shown that the asymptotic behavior of the equal-time correlation function is determined by Galilean-invariant composite operators. The corrections to the Kolmogorov spectrum associated with the operators of canonical dimension 6 are found. The consequences of Galilean invariance for the renormalized composite operators are considered.State University, St. Petersburg. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 100, No. 3, pp. 382–401, September, 1994.     

Renormalization group in the problem of fully developed turbulence of a compressible fluid

A model of fully developed turbulence of a compressible liquid (gas), based on the stochastic Navier-Stokes equation, is considered by means of the renormalization group. It is proved that the model is multiplicatively renormalized in terms of the “velocity-logarithm of density” variables. The scaling dimensions of the fields and parameters are calculated in the one-loop approximation. Dependence of the effective sound velocity and the Mach number on the integral turbulence scale L is studied. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 110, No. 3, pp. 385–398, March, 1997.     

The Renormalized Two-Scale Method

We show that, by uniting the two-scale method with the counterterm method of renormalized perturbation, one obtains approximate solutions of nonlinear motions which hold for all times.     

The Mass Shell in the Semi-Relativistic Pauli–Fierz Model

We consider the semi-relativistic Pauli–Fierz model for a single free electron interacting with the quantized radiation field. Employing a variant of Pizzo’s iterative analytic perturbation theory we construct a sequence of ground state eigenprojections of infra-red cutoff, dressing transformed fiber Hamiltonians and prove its convergence, as the cutoff goes to zero. Its limit is the ground state eigenprojection of a certain renormalized fiber Hamiltonian. The ground state energy is an exactly twofold degenerate eigenvalue of the renormalized Hamiltonian, while it is not an eigenvalue of the original fiber Hamiltonian unless the total momentum is zero. These results hold true, for total momenta inside a ball about zero of arbitrary radius ${\mathfrak{p} > 0}$ , provided that the coupling constant is sufficiently small depending on ${\mathfrak{p}}$ and the ultra-violet cutoff. Along the way we prove twice continuous differentiability and strict convexity of the ground state energy as a function of the total momentum inside that ball.     

Stochastic properties of autowave turbulence elimination

The complex spatio-temporal behavior due to spiral breakup and wave interaction, in a 2D reaction diffusion system is eliminated by spatially uniform perturbation. This autowave turbulence is modeled by a stochastic process of defect production and annihilation. The constructed solution agrees well with probabilities – in particular probability to have no defects – estimated from the reaction diffusion system. The time to extinction, related to the probability of eliminating all defects, depends on the medium size and the applied perturbation amplitude.     

On some problems in perturbation theory of smooth invariant tori of dynamical systems

Problems related to perturbation theory of smooth invariant tori of dynamical systems in an-dimensional Euclidean spaceR ⁿ are considered. The clarification of these problems plays an important role for perturbation theory suggested by the author in [1] and extends the scope of its application.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 12, pp. 1665–1699, December, 1994.     

Diagram equations of the theory of fully developed turbulence

Skeleton diagram equations of turbulence theory — the Dyson equations and the equations for vertices of three types — are obtained nonperturbatively. Their derivation is based on the use of an equation in functional derivatives for the characteristic functional of a hydrodynamic system described by Navier-Stokes equations in the presence of an external random force. The iterative solution of these equations reproduces the perturbation series for second moments that is usually obtained in a more complicated way and also the series for the third moments.Institute of Problems in Mechanics, Russian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 101, No. 1, pp. 28–37, October, 1994.     

Weakly Nonlinear Analysis of a Localized Disturbance in Poiseuille Flow

In this article, we investigate, via a perturbation analysis, some important nonlinear features related to the process of transition to turbulence in a wall-bounded flow subject to a spatially localized disturbance that is harmonic in time. We show that the perturbation expansion, truncated at second order, is able to capture the generation of streamwise vorticity as a weakly nonlinear effect. The results of the perturbation approach are discussed in comparison with direct numerical simulation data for a sample case by extracting the contribution of the different orders. The main aim is to provide a tool to select the most effective nonlinear interactions to enlighten the essential features of the transitional process.     

Anomaly Problem in the N=1 Supersymmetric Electrodynamics as a Consequence of the Inconsistency of the Dimensional Reduction Method

We compare the calculation of the two-loop -function in the N=1 supersymmetric electrodynamics regularized via higher derivatives and via dimensional reduction. We show that the renormalized effective action is the same for both regularizations. But in the method of higher derivatives, unlike in the dimensional reduction, the -function defined as the derivative of the renormalized coupling constant with respect to log turns out to be purely one-loop. The anomaly problem therefore does not occur in this regularization, because in the method of higher derivatives, the diagrams with counterterm insertions make a nonzero contribution, which is evaluated exactly in all orders of the perturbation theory. When dimensional reduction is used, this contribution is zero. We argue that this result is a consequence of the mathematical inconsistency of the dimensional reduction method and that just this inconsistency leads to the anomaly problem.     

Principle of maximal randomness and parity violation in turbulence

We show that in the self-consistent equations for equal-time correlation functions of velocity fluctuations obtained in the model of developed turbulence based on the maximal randomness principle, infrared divergences are absent from all orders of the perturbation theory. We analyze the additional ultraviolet (UV) divergences that appear in the two-loop approximation of the self-consistent equations. We show that in the system with conserved parity, these divergences can be eliminated using the existing ambiguity in the solution. In the case of parity violation in the system, the UV divergences have a logarithmic form, which can indicate a deviation from the Kolmogorov scaling.     

Weak solutions to a nonlinear variational wave equation and some related problems

In this paper we present some results on the global existence of weak solutions to a nonlinear variational wave equation and some related problems. We first introduce the main tools, the L ^p Young measure theory and related compactness results, in the first section. Then we use the L ^p Young measure theory to prove the global existence of dissipative weak solutions to the asymptotic equation of the nonlinear wave equation, and comment on its relation to Camassa-Holm equations in the second section. In the third section, we prove the global existence of weak solutions to the original nonlinear wave equation under some restrictions on the wave speed. In the last section, we present global existence of renormalized solutions to two-dimensional model equations of the asymptotic equation, which is also the so-called vortex density equation arising from sup-conductivity.     

Self-similar random fields

The present paper is devoted to a survey of results of recent years in the theory of self-similar fields and convergence of renormalized transformations to such fields (limit theorems) and also applications in the theory of critical phenomena of statistical physics and quantum field theory.Translated from Itogi Nauki i Tekhniki, Seriya Teoriya Veroyatnostei, Matematicheskaya Statistika, Teoreticheskaya Kibernetika, Vol. 20, pp. 3–52, 1983.     

Explicit Formulas for GJMS-Operators and Q-Curvatures

We describe GJMS-operators as linear combinations of compositions of natural second-order differential operators. These are defined in terms of Poincaré–Einstein metrics and renormalized volume coefficients. As special cases, we derive explicit formulas for conformally covariant third and fourth powers of the Laplacian. Moreover, we prove related formulas for all Branson’s Q-curvatures. The results settle and refine conjectural statements in earlier works. The proofs rest on the theory of residue families introduced in Juhl (Progress in Mathematics, vol. 275. Birkhäuser Verlag, Basel, 2009).     

New perturbation theory representation of the conformal symmetry breaking effects in gauge quantum field theory models

We propose a hypothesis on the detailed structure for the representation of the conformal symmetry breaking term in the basic Crewther relation generalized in the perturbation theory framework in QCD renormalized in the [`(MS)]\overline {MS} scheme. We establish the validity of this representation in the O(α _s ⁴ ) approximation. Using the variant of the generalized Crewther relation formulated here allows finding relations between specific contributions to the QCD perturbation series coefficients for the flavor nonsinglet part of the Adler function D _A ^ns for the electron-positron annihilation in hadrons and to the perturbation series coefficients for the Bjorken sum rule S _Bjp for the polarized deep-inelastic lepton-nucleon scattering. We find new relations between the α _s ⁴ coefficients of D _A ^ns and S _Bjp . Satisfaction of one of them serves as an additional theoretical verification of the recent computer analytic calculations of the terms of order α _s ⁴ in the expressions for these two quantities.     

Inhomogeneous boundary value problem for nonstationary compressible Navier–Stokes equations

The existence of global weak renormalized solutions to the evolution flow problems for compressible Navier–Stokes equations is established. The in/out flow problem in a bounded domain in three spatial dimensions is considered. A general mathematical theory for the flow problem is developed. Bibliography: 15 titles.     

A one-dimensional model for dispersive wave turbulence

Summary A family of one-dimensional nonlinear dispersive wave equations is introduced as a model for assessing the validity of weak turbulence theory for random waves in an unambiguous and transparent fashion. These models have an explicitly solvable weak turbulence theory which is developed here, with Kolmogorov-type wave number spectra exhibiting interesting dependence on parameters in the equations. These predictions of weak turbulence theory are compared with numerical solutions with damping and driving that exhibit a statistical inertial scaling range over as much as two decades in wave number. It is established that the quasi-Gaussian random phase hypothesis of weak turbulence theory is an excellent approximation in the numerical statistical steady state. Nevertheless, the predictions of weak turbulence theory fail and yield a much flatter (|k|^−1/3) spectrum compared with the steeper (|k|^−3/4) spectrum observed in the numerical statistical steady state. The reasons for the failure of weak turbulence theory in this context are elucidated here. Finally, an inertial range closure and scaling theory is developed which successfully predicts the inertial range exponents observed in the numerical statistical steady states.     

Scaling laws and vanishing-viscosity limits for wall-bounded shear flows and for local structure in developed turbulence

Scaling laws for wall-bounded turbulence are derived and their properties are analyzed via vanishing-viscosity asymptotics; a comparison of the results with recent experiments shows that the observed scaling law differs significantly from the customary logarithmic law of the wall. The Izakson-Millikan-von Mises derivation of turbulence structure, properly interpreted, confirms this analysis. Analogous relations for the local structure of turbulence are given, including results on the scaling of the higher-order structure functions; these results suggest that there are no Reynolds-number-independent corrections to the Kolmogorov exponent and thus that the classical 1941 version of the Kolmogorov theory already gives the limiting behavior. The use of small-viscosity asymptotics is explained, and the consequences of the theory and of the experimental evidence for the Navier-Stokes equations and for the statistical theory of turbulence are discussed. © 1997 John Wiley & Sons, Inc.     

Interpolation between sequence transformations

Levin's sequence transformation [1] and a structurally very similar sequence transformation [4] behave quite differently in convergence acceleration and summation processes. In particular, it was found recently that Levin's transformation fails completely in the case of the strongly divergent Rayleigh-Schrödinger and renormalized perturbation expansions for the ground state energies of anharmonic oscillators, whereas the structurally very similar sequence transformation gives very good results [14,17]. For a more detailed investigation of these phenomena, a sequence transformation is constructed which — depending on a continuous parameter — is able to interpolate between Levin's transformation and the other sequence transformation. Some numerical examples, which illustrate the properties of the interpolating sequence transformation, are presented.