Unified theory of nuclear reactions

The authors review the theory and phenomenology of instantons in quantum chromodynamics (QCD). After a general overview, they provide a pedagogical introduction to semiclassical methods in quantum mechanics and field theory. The main part of the review summarizes our understanding of the instanton liquid in QCD and the role of instantons in generating the spectrum of light hadrons. The authors also discuss properties of instantons at finite temperature and how instantons can provide a mechanism for the chiral phase transition. They give an overview of the role of instantons in some other models, in particular low-dimensional sigma models, electroweak theory, and supersymmetric QCD.

http://wonka.physics.ncsu.edu/~tmschaef/physics/RevModPhys_Instantons.pdf

Instantons in QCD

The topic of cosmic strings provides a bridge between the physics of the very small and the very large They are predicted by some unified theories of particle interactions If they exist, they may help to explain some of the largest-scale structures seen in the Universe today They are `topological defects' that may have been formed at phase transitions in the very early history of the Universe, analogous to those found in some condensed-matter systems --- vortex lines in liquid helium, flux tubes in type-II superconductors, or disclination lines in liquid crystals In this review, we describe what they are, why they have been hypothesized and what their cosmological implications would be The relevant background from the standard models of particle physics and cosmology is described in section 1 In section 2, we review the idea of symmetry breaking in field theories, and show how the defects formed are constrained by the topology of the manifold of degenerate vacuum states We also discuss the different types of cosmic strings that can appear in different field theories Section 3 is devoted to the dynamics of cosmic strings, and section 4 to their interaction with other fields The formation and evolution of cosmic strings in the early Universe is the subject of section 5, while section 6 deals with their observational implications Finally, the present status of the theory is reviewed in section 7

Cosmic strings

Energy levels of Z = 11−21 nuclei (IV)

Energy levels of A = 21−44 nuclei (V)

A chiral soliton model of nucleon and delta

We propose a model of the nucleon and delta based on the idea that strong QCD forces on length scales \ensuremath{\sim}0.2--1 fm result in hidden chiral SU(2)\ifmmode\times\else\texttimes\fi{}SU(2) symmetry and that there is a separation of roles between these forces which are also responsible for binding quarks in hadrons and the forces which produce absolute confinement. This leads us to study a linear \ensuremath{\sigma} model describing the interactions of quarks, \ensuremath{\sigma} mesons, and pions. We have solved this model in the semiclassical (mean-field) approximation for the hedgehog baryon state. We refer to this solution as a chiral soliton. In the semiclassical approximation the hedgehog state is a linear combination of N and \ensuremath{\Delta}. We project this state onto states of good spin and isospin to calculate matrix elements of various operators in these states. Our results are in reasonable agreement with the observed properties of the nucleon. The mesonic contributions to ${g}_{A}$ and \ensuremath{\sigma}(\ensuremath{\pi}N) are about two to three times too large, suggesting the need for quantum corrections.

Manoj K. Banerjee

Papers

A chiral soliton model of nucleon and delta

Chiral model for nucleon and delta

Direct interaction theory of inelastic scattering. Part I

Direct interaction theory of inelastic scattering: Part III. Numerical calculations

Direct interaction theory of inelastic scattering