Is the strong-interaction proton-proton scattering length renormalization scale dependent in effective field theory?

It is shown that the strong-interaction ${}^1S_0$ proton-proton scattering length in very low-energy effective field theory does not depend on the renormalization scale, if the electromagnetic interaction is "switched off" consistently.Comment: 9 pages, no figures, ReVTEX

How to define physical properties of unstable particles

In the framework of effective quantum field theory we address the definition of physical quantities characterizing unstable particles. With the aid of a one-loop calculation, we study this issue in terms of the charge and the magnetic moment of a spin-1/2 resonance. By appealing to the invariance of physical observables under field redefinitions we demonstrate that physical properties of unstable particles should be extracted from the residues at complex (double) poles of the corresponding S-matrix.Comment: 11 pages, 3 figures, REVTeX

Doublet channel neutron-deuteron scattering in leading order effective field theory

The doublet channel neutron-deuteron scattering amplitude is calculated in leading order effective field theory (EFT). It is shown that this amplitude does not depend on a constant contact interaction three-body force. Satisfactory agreement with available data is obtained when only two-body forces are included.Comment: Conference talk (Gegelia) at "Mesons & Light Nuclei '01" Prague, Czech Republic, 2-6 July, 2001, 5 pages, RevTe

Regularization, renormalization and "peratization" in effective field theory for two nucleons

We discuss conceptual aspects of renormalization in the context of effective field theories for the two-nucleon system. It is shown that, contrary to widespread belief, renormalization scheme dependence of the scattering amplitude can only be eliminated up to the order the calculations are performed. We further consider an effective theory for an exactly solvable quantum mechanical model which possesses a long- and short-range interaction to simulate pionful effective field theory. We discuss the meaning of low-energy theorems in this model and demonstrate their validity in calculations with a finite cutoff $\Lambda$ as long as it is chosen of the order of the hard scale in the problem. Removing the cutoff by taking the limit $\Lambda \to \infty$ yields a finite result for the scattering amplitude but violates the low-energy theorems and is, therefore, not compatible with the effective field theory framework.Comment: 22 pages, 2 figures, to appear in Eur. Phys. J.

Can the Fundamental Theory Of Everything be Renormalizable?

Some considerations showing that renormalizable theories with consistent perturbative theries can not be nonperturbatively finite (in terms of bare parameters) are provided. Accordingly any fundamental unified theory has to be either non renormalizable or order by order finite.Comment: 3 pages (LaTEX file