Nonperturbative Vacuum Research Articles

Toward a theory of the strong interactions

A systematic study is made of the relevant degrees of freedom and the dynamics of quantum chromodynamics (QCD). We find that the dynamical properties of QCD are, to a large extent, a consequence of the structure of the vacuum arising from the tunneling between degenerate, classically stable, vacuums, and that the relevant degrees of freedom can be taken to be the Euclidean path histories that can be used to calculate the tunneling in the semiclassical approximation. This nonperturbative vacuum structure appears well suited to the major features of QCD, i.e., the dimensional transmutation that determines the size of the hadrons and the strong-interaction coupling constant, the source of dynamical chiral symmetry breaking, and the mechanism responsible for quark confinement.

Vacuum polarization phenomenology: The μ mesic atom X-ray discrepancy and the [formula omitted] separation in the [formula omitted] system

The possible existence of non-perturbative vacuum polarization modifications and the possible existence of a weakly-coupled light scalar boson have been recently proposed to explain the apparent μ-mesic atom X-ray discrepancy. Their effects are shown to introduce in the separation of the 2 P 3 2 and 2 S 1 2 levels of the (μ 4He) + system a discrepancy between recent experiment and theory - otherwise in agreement - of the same level as the original μ-mesic atom X-ray discrepancy.

Comments on proposed explanations for the muonic-atom x-ray discrepancy

Two proposed explanations for the apparent muonic-atom x-ray discrepancy are the possible existence of nonperturbative vacuum polarization modifications and the possible existence of a weakly coupled light scalar boson. We show that a nonperturbative decrease in the vacuum polarization spectral function implies a reduction in the vertex for a timelike photon to couple to an electron-positron pair. This would lower by a few percent the rate for ${\ensuremath{\pi}}^{0}$ Dalitz decay and suggests observable effects in the colliding beam reactions ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{e}^{+}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\mu}}^{\ensuremath{\mp}}$. Turning to the scalar-boson hypothesis, we use neutron-electron and electron-deuteron scattering data to show that a scalar particle with mass lighter than about 0.6 MeV cannot be invoked to explain the muonic discrepancy. We conclude by discussing the useful role which isotope effects and pionic-atom experiments might play in determining the phenomenological structure of the extra potential implied by the discrepancy.

Analytic solution for tachyon condensation in open string field theory

We propose a new basis in Witten’s open string field theory, in which the star product simplifies considerably. For a convenient choice of gauge the classical string field equation of motion yields straightforwardly an exact analytic solution that represents the nonperturbative tachyon vacuum. The solution is given in terms of Bernoulli numbers and the equation of motion can be viewed as novel Euler–Ramanujan-type identity. It turns out that the solution is the Euler–Maclaurin asymptotic expansion of a sum over wedge states with certain insertions. This new form is fully regular from the point of view of level truncation. By computing the energy difference between the perturbative and nonperturbative vacua, we prove analytically Sen’s first conjecture.