English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

In the framework of the Schwinger-Dyson equation and the Bethe-Salpeterequation in the improved ladder approximation, we calculate the S parameter andan analogue of the \pi^+ - \pi^0 mass difference \Delta m_\pi^2 \equivm_{\pi^+}^2 -m_{\pi^0}^2 as well as the NG boson decay constant f_\pi on thesame footing in the large N_f QCD, through the difference between the vectorcurrent correlator \Pi_{VV} and the axial-vector current correlator \Pi_{AA}.Approaching the chiral phase transition point \alpha_*\to \alpha_{\rm cr}(=\pi/4) from the broken phase, where \alpha_* is the the gauge coupling on theinfrared fixed point, \Delta m_\pi^2 as well as f_\pi^2 goes to zero with theessential-singularity scaling (Miransky scaling), while the ratio indicates ablowing up enhancement reflecting the characteristic behavior of the large N_fQCD as a walking theory which is expected to scale as \Delta m_\pi^2/f_\pi^2\sim (\alpha_*/\alpha_{\rm cr}-1)^{-1/2}. On the other hand, the S parametertakes values somewhat smaller than that of the real-life QCD and indicatesslightly decreasing tendency as we approach the phase transition point.Comment: Change of title & abstract, new reference, new discussions on  ultraviolet contributions from outside of those explicitly calculated. 32  pages, 12 figure

The + - 0 Mass Difference and the S Parameter in Large Nf QCD