arXiv subjects
Publications and source records attributed to W. -Y. P. Hwang.
Bubble collisions in cosmological phase transitions are explored, taking the non-abelian character of the gauge fields into account. Both the QCD and electroweak phase transitions are considered. Numerical solutions of the field equations in several limits are presented.
The light cone QCD sum rules are derived for the $πNN$ coupling $g_{πNN}$ and $πNN(1535)$ coupling $g_{πNN^\ast}$. The contribution from the excited states and continuum is subtracted cleanly through double Borel transformation. We first improve the original sum rule for $g_{πNN}$ and determine the value of the pion wave function at the middle point $ϕ_π(u_0 ={1\over 2})=(1.5\pm 0.2)$ at $μ=1$GeV, which is a fundamental nonperturbative quantity like the quark condensate. Our calculation shows that the $πN N(1535)$ coupling is strongly suppressed.
We apply the method of QCD sum rules in the presence of external electromagnetic fields $F_{μν}$ to the problem of the electromagnetic decays of various vector mesons, such as $ρ\toπγ$, $K^\ast\to Kγ$ and $η'\toργ$. The induced condensates obtained previously from the study of baryon magnetic moments are adopted, thereby ensuring the parameter-free nature of the present calculation. Further consistency is reinforced by invoking various QCD sum rules for the meson masses. The numerical results on the various radiative decays agree very well with the experimental data.
We calculate the on-shell $Σ^0$-$Λ$ mixing parameter $θ$ with the method of QCD sum rule. Our result is $θ(m^2_{Σ^0}) =(-)(0.5\pm 0.1)$MeV. The electromagnetic interaction is not included.
The method of QCD sum rules in the presence of external elctromagnetic fields is used to calculate the $Ω$ magnetic moment $μ_{Ω^-}$ and $Σ^0$-$Λ$ transition magnetic moment $μ_{Σ^0Λ}$, with the susceptibilities obtained previously from the study of octet baryon magnetic moments. The results $μ_{Ω^-}=-1.92μ_N$ and $μ_{Σ^0Λ}=1.5μ_N$ are in good agreement with the recent experimental data.