Renormalization of Feynman amplitudes and parametric integral representation

A new substraction formula is presented to renormalize Feynman amplitudes written in Schwinger's integral representation. The substractions are generated by an operator acting on the integrand, which only depends on the total number of internal lines but is completely independent of the structure of the graph. This formulation is also valid for non-renormalizable theories and is shown to reduce to Zimmermann'sR-operation for scalar theories. It satisfies in any case Bogoliubov's recursive formula and yields an explicit tool for actual computations of renormalized Feynman amplitudes with a minimal number of substractions.     

Non-Commutative Complete Mellin Representation for Feynman Amplitudes

We extend the complete Mellin (CM) representation of Feynman amplitudes to the non-commutative quantum field theories. This representation is a versatile tool. It provides a quick proof of meromorphy of Feynman amplitudes in parameters such as the dimension of space–time. In particular it paves the road for the dimensional renormalization of these theories. This complete Mellin representation also allows the study of asymptotic behavior under rescaling of arbitrary subsets of external invariants of any Feynman amplitude.      

Integral representation for the dimensionally renormalized Feynman amplitude

A compact convergent integral representation for dimensionally renormalized Feynman amplitudes is explicitly constructed. The subtracted integrand is expressed as a distribution in the Schwinger -parametric space, and is obtained by applying upon the bare integrand a new subtraction operatorR' which respects Zimmermann's forest structure.     

Asymptotic expansions in limits of large momenta and masses

Asymptotic expansions of renormalized Feynman amplitudes in limits of large momenta and/or masses are proved. The corresponding asymptotic operator expansions for theS-matrix, composite operators and their time-ordered products are presented. Coefficient functions of these expansions are homogeneous within a regularization of dimensional or analytic type. Furthermore, they are explicitly expressed in terms of renormalized Feynman amplitudes (at the diagrammatic level) and certain Green functions (at the operator level).     

Circuit based graphs for renormalized perturbation theory

A generalization of graph theory is introduced and used to obtain Feynman parametric formulas relevant to renormalized amplitudes. The generalization of graph theory is based upon circuit coefficients instead of the usual incidence matrix. The parametric formulas presented are valid for amplitudes which have been renormalized, as in the Zimmermann formulation, by subtracting Taylor terms in momentum space.The research reported in this paper was supported in part by the Max-Planck-Institut für Physik, München, by the German and American Fulbright Commission in Bonn, and by the Department of Mathematics of the University of Virginia, Charlottesville.     

高频波激发低频磁场和离子声波的重整化强湍动理论

本文给出了高温等离子体中高频波激发低频磁场和离子声波强湍动过程的重整化理论,以便改善通常的弱非线性处理方法,从Vlasov-Maxwell方程组出发,在Fourier表象中得到了包含“最发散”和“次发散”效应互相耦合的高频和低频传播于重整化方程组,从而获得了高、低频振荡粒子重整化分布函数和场的耦合关系。在“最发散”重整化近似下,我们求解了高低频传播子方程组,得到了展开到v₄(高频湍动场能密度与等离子体热能密度之比)一次方的近似解和重整化介电函数等表达式。然后,在Fourier逆变换下导得了我们所要的时空表用中重整化强湍动方程组。最后,作为一个说明重整化作用的例子,在一维稳态下求解了孤立子的形式。 关键词：     

A points-splitting and dimensional renormalization

We consider Feynman amplitudes which are doubly regularized by means of complete points splitting of vertices and continuation in the dimension of space-time. We show how to construct a subtraction operator which leads to polynomial counterterms and to a renormalized amplitude which is finite as the regularizations are removed in either order, and corresponds to the dimensionally renormalized result in the limit of no points splitting.     

Minimal renormalization without ɛ-expansion: Amplitude functions in three dimensions

The minimal subtraction scheme and the Borel resummation method are used to calculate the amplitudes of renormalized correlation functions aboveT _c for then-vector model in three dimensions. Accurate representations are given for the effective amplitudes of the renormalized expressions of the correlation length, of the susceptibility and of the specific heat forn=1, 2, 3. The resummed higher-order contributions turn out to yield only small corrections to the low-order approximations. These results complement a recent calculation of renormalization-group functions and provide the basis for accurate analyses of the critical behavior in three dimensions including the amplitude functions.     

The convergence of BPH renormalization

The convergence of the integrals defining BPH renormalized Feynman amplitudes is derived from the known additive structure of analytic renormalization.     

Renormalization of position space amplitudes in a massless QFT

Ultraviolet renormalization of position space massless Feynman amplitudes has been shown to yield associate homogeneous distributions. Their degree is determined by the degree of divergence while their order—the highest power of logarithm in the dilation anomaly—is given by the number of (sub)divergences. In the present paper we review these results and observe that (convergent) integration over internal vertices does not alter the total degree of (superficial) ultraviolet divergence. For a conformally invariant theory internal integration is also proven to preserve the order of associate homogeneity. The renormalized 4-point amplitudes in the φ⁴ theory (in four space-time dimensions) are written as (non-analytic) translation invariant functions of four complex variables with calculable conformal anomaly.Our conclusion concerning the (off-shell) infrared finiteness of the ultraviolet renormalized massless φ⁴ theory agrees with the old result of Lowenstein and Zimmermann [23].     

Feynman amplitudes with confinement included

Amplitudes for any multipoint Feynman diagram are written taking into account vacuum background confining field. Higher order gluon exchanges are treated within background perturbation theory. For amplitudes with hadrons in initial or final states vertices are shown to be expressed by the corresponding wave function with the renormalized z factors. Examples of two-point functions, three-point functions (form factors), and decay amplitudes are explicitly considered. The text was submitted by the author in English.     

Dimensional renormalization and factorization

The problem of formulating a high-energy factorization explicitly in terms of dimensionally renormalized operators and coefficient functions is analyzed in the context of deep-inelastic scattering in renormalizable scalar theories. The coefficient functions that emerge are found to be the finite parts of dimensionally continued on-shell amplitudes, and are readily amenable to explicit computation. As a byproduct, an explicit forest formula emerges for the mass-singularity poles of on-shell amplitudes in renormalizable theories. The extension to gauge theories is briefly discussed at the leading twist level. The method is compared to the alternative approach to factorization whereby a finite hard part is defined by factorizing off mass-singularities.     

The Temperature Zero Limit

We prove that, for a broad class of many-fermion models, the amplitudes of renormalized Feynman diagrams converge to their temperature zero values in the limit as the temperature tends to zero.     

Renormalization Group Maps for Ising Models in Lattice-Gas Variables

Real-space renormalization group maps, e.g., the majority rule transformation, map Ising-type models to Ising-type models on a coarser lattice. We show that each coefficient in the renormalized Hamiltonian in the lattice-gas variables depends on only a finite number of values of the renormalized Hamiltonian. We introduce a method which computes the values of the renormalized Hamiltonian with high accuracy and so computes the coefficients in the lattice-gas variables with high accuracy. For the critical nearest neighbor Ising model on the square lattice with the majority rule transformation, we compute over 1,000 different coefficients in the lattice-gas variable representation of the renormalized Hamiltonian and study the decay of these coefficients. We find that they decay exponentially in some sense but with a slow decay rate. We also show that the coefficients in the spin variables are sensitive to the truncation method used to compute them.     

Minimal renormalization without ε-expansion

The minimal subtraction scheme and the Borel resummation method are used to calculate the amplitudes of renormalized correlation functions belowT _c for the three-dimensional ⁴ model with a oneccomponent order parameter. Accurate representations are given for the effective amplitudes of the renormalized expressions of the order parameter, of the susceptibility and of the specific heat. The resummed higher-order contributions to the order parameter,and to the specific heat turn out to yield only small corrections to the low-order approximations. Our results provide the basis for accurate analyses of the critical behavior of Ising-type systems in three dimensions belowT _c including the amplitude functions.     

On the formalism of relativistic many body theory

The thermodynamic potential is constructed as an effective action functional of the various n point amplitudes (n ? 4). One of the functionals is used to obtain the equations of state as simple, convergent expressions involving the conventionally renormalized charges and masses.     

On renormalization and complex space-time dimensions

The method of using the dimension of space-time as a complex parameter introduced recently to regularize Feynman amplitudes is extended to an arbitrary Feynman graph. The method has promise of being particularly well-suited to gauge theories. It is shown how the renormalized amplitude, together with the Lagrangian counter-terms, may be extracted directly, following the method of analytic renormalization.     

Finite renormalizations of 0Sp(N, 4) supersymmetry

The calculation of the one-loop effective potential of the Wess-Zumino model is carried out using Green functions which propagate fields inn-dimensional anti-de Sitter space. The divergent parts of the amplitudes are independent of the choice of boundary conditions. The finite counterterms can be adjusted in such a way that the renormalized action be supersymmetric invariant. Addressing the question of the survival of the supersymmetry invariance of the vacuum state, we derive the result of the persistence of supersymmetry in the semiclassical approximation.     

Infinitely divisible distribution functions of class L and the Lee-Yang theorem

It is shown that the free-energy density of a large class of ferromagnets satisfying the Lee-Yang property is to be connected with the limit characteristic function of a suitably renormalized sum of independent and non-identically distributed random variables. Using the canonical representation formulae of such characteristic functions, various chains of inequalities are derived for the Ursell functions.     

Infrared singularities in the dimensional regularization scheme

Infrared singularities arising in some renormalized amplitudes of quantum electrodynamics are analyzed using the dimensional regularization method. We define infrared and ultraviolet convergent regions in the ν complex plane (ν is the number of dimensions of space time). It turns out that these regions do not overlap for quantum electrodynamics. Nevertheless, it is shown that there exists a unique analytic continuation from the infrared convergent region which allows us to interpret the infrared divergence in the renormalized electron self-energy amplitude as an isolated singularity at ν = 4. This statement seems to be true at all orders of perturbation theory. We also prove that the double limit μ → 0, ν → 4 (μ is the auxiliary photon mass) does not exist in quantum electrodynamics and we conjecture that this lack of uniformity provides theoretical support for the ansatz of Marciano and Sirlin.