We suggest the modification of the standard approach to TMDs. The modification consists in the consideration of the small bT operator product expansion in the different operator basis. Instead of power expansion we suggest to use the Laguerre polynomial expansion. Within such a scheme the first term of OPE saturates TMDs in the wider range of bT in comparison to the power expansion that decreas...

A quantum realization of the Relativistic Harmonic Oscillator is realized in terms of the spatial variable x and d dx (the minimal canonical representation). The eigenstates of the Hamiltonian operator are found (at lower order) by using a perturbation expansion in the constant c−1. Unlike the Foldy-Wouthuysen transformed version of the relativistic hydrogen atom, conventional perturbation theo...

We show that Chern-Simons gauge theory with appropriate cutoffs is equivalent, term by term in perturbation theory, to a Fermionic theory with a nonlocal interaction term. When an additional cutoff is placed on the Fermi fields, this Fermionic theory gives rise to a convergent perturbation expansion. This leads us to conjecture that Chern-Simons gauge theory also gives rise to convergent pertur...

We show how to construct path integrals for quantum mechanical systems where the space of configurations is a general non-compact symmetric space. Associated with this path integral is a perturbation theory which respects the global structure of the system. This perturbation expansion is evaluated for a simple example and leads to a new exactly soluble model. This work is a step towards the con...

S-wave Kp scattering into various channels near threshold are analyzed in heavybaryon chiral perturbation theory with Λ(1405) introduced as an independent field. This is the approach that predicted the critical density 2 <∼ ρc/ρ0 <∼ 3 for negatively charged kaon condensation. We show that chiral perturbation expansion treating the Λ(1405) as elementary is consistent with all threshold data incl...

The perturbative renormalization group(RG) equation is applied to resum divergent series of perturbative wave functions of quantum anharmonic oscillator. It is found that the resummed series gives the cumulant of the naive perturbation series. It is shown that a reorganization of the resummed series reproduce the correct asymptotic form of the wave function at x → ∞ when the perturbation expans...

After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion–pion scattering to two–loop accuracy. In the pion–nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy–nucleon expansion is used to construct the effective pion...

The strong coupling expansion coefficients for the ordinary and renormalized energies of the ground and first excited states of the quartic, sextic, octic and decadic anharmonic oscillators with the Hamiltonian 2 + 2 + 2 , 2 3 4 5 are computed. The expansion coefficients are also computed for higher excited states of the quartic oscillator. The large-order beha viour of the coefficients, the ra...

ABSTRACT: We investigate the mechanism of spin gap formation in a two-dimensional model relevant to Mott insulators such as CaV4O9. From the perturbation expansion and quantum Monte Carlo calculations, the origin of the spin gap is ascribed to the four-site plaquette singlet in contrast to the dimer gap established in the generalized dimerized Heisenberg model. We investigate the mechanism of s...

Apparent large failures of perturbation theory in lattice gauge theory at g* 5 1.0 result from the use of the bare coupling constant of the lattice regulator in the perturbative expansion. They can be cured by the use of a coupling constant defined by some physical process. Thissituation is thesame as that encountered in dimensionally regularized perturbation theory, where the use of a coupling...