In this paper, we establish Desch-Schappacher type multiplicative and additive perturbation theorems for existence families for arbitrary order abstract Cauchy problems in a Banach space: u(n)(t) = Au(t) (t ≥ 0); u(j)(0) = xj (0 ≤ j ≤ n− 1). As a consequence, we obtain such perturbation results for regularized semigroups and regularized cosine operator functions. An example is also given to ill...

Flow equations method of continuous unitary transformations is used to eliminate the minimal quark-gluon interaction in the light-front quantized QCD Hamiltonian. The coupled differential equations in the two lowest Fock sectors correspond to the renormalization of the light-front gluon mass and the generation of effective quark-antiquark interaction. The influence of the renormalization of the...

Radiative decays of heavy quark bound states have been investigated in the framework of perturbative QCD and have been used to measure the QCD coupling at scales of the order of the heavy quark mass (for recent studies see Refs. [1-3], and references therein). Away from the boundaries of the phase space, the inclusive spectra are expected to be well described by first or second order perturbati...

Igor Klebanov * Department of Physics Joseph Henry Laboratories Princeton University Princeton, N J 08544 These lectures review the fundamentals of the Skyrme model of baryons and its relationship with the non-relativistic quark model and the large-N QCD. Special emphasis is placed on the problems the model experiences in perturbative treatment of SU(3) breaking. It is argued that the strange q...

Recent work suggests that fundamental and Dirichlet strings, and their (p, q) bound states, may be observed as cosmic strings. The evolution of cosmic string networks, and therefore their observational signals, depends on what happens when two strings collide. We study this in string perturbation theory for collisions between all possible pairs of strings; different cases involve sphere, disk, ...

The additive exponential noise channel with additive exponential interference (AENC-AEI) known non-causally at the transmitter is studied. This channel can be considered as an exponential version of the discrete memoryless channel with state known non-causally at the encoder considered by Gelfand and Pinsker. We make use of Gelf’and-Pinsker’s classic capacity Theorem to derive inner and outer b...

A relativistic equation is deduced for the bound state of two particles, by assuming a proper boundary condition for the propagation of the negative-energy states. It reduces to the (one-body)Dirac equation in the infinite limit of one of the constituent mass. It also has the symmetries to assure the existence of the anti-bound-state with the same mass. The interaction kernel(pseudo-potential) ...

Perturbative QeD may be subdivided into separately gauge-invariant sectors according to the projection of non-abelian color weights onto linearly independent basis elements. We exploit the general Lie group structure of the theory to give an algorithm for finding these gauge-invariant sets and present several examples of its use. The planar sector and the systematks of the non-planar correction...

A system of two Korteweg-de Vries equations coupled by small linear and nonlinear terms, which is a model of a resonant interaction between two internal gravity-wave modes in a shallow stratified liquid, is considered. The present paper is a continuation of a preceding one, where only the linear coupling was dealt with. Various dynamical processes involving one-mode solitons are investigated. I...

We derive the (matrix-valued) Feynman rules of mass perturbation theory of the massive Schwinger model for non-zero vacuum angle θ. Further, we discuss the properties of the three-boson bound state and compute – by a partial resummation of the mass perturbation series – its mass and its partial decay widths.