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/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

We conjecture that the phase transitions in QCD at large number of coloursN\gg 1 is triggered by the drastic change in the instanton density. As a resultof it, all physical observables also experience some sharp modification in the\theta behaviour. This conjecture is motivated by the holographic model of QCDwhere confinement -deconfinement phase transition indeed happens precisely attemperature T=T_c where $\theta$ dependence of the vacuum energy experiences asudden change in behaviour: from N^2\cos(\theta/N) at T<T_c to\cos\theta\exp(-N) at T>T_c. This conjecture is also supported by recentlattice studies. We employ this conjecture to study a possible phase transitionas a function of \kappa\equiv N_f/N from confinement to conformal phase in theVeneziano limit N_f\sim N when number of flavours and colours are large, butthe ratio \kappa is finite. Technically, we consider an operator which gets itsexpectation value solely from nonperturbative instaton effects. When \kappaexceeds some critical value \kappa> \kappa_c the integral over instanton sizeis dominated by small-size instatons, making the instanton computationsreliable with expected \exp(-N) behaviour. However, when \kappa<\kappa_c, theintegral over instaton size is dominated by large-size instantons, and theinstanton expansion breaks down. This regime with \kappa<\kappa_c correspondsto the confinement phase. We also compute the variation of the critical\kappa_c(T, \mu) when the temperature and chemical potential T, \mu \ll\Lambda_{QCD} slightly vary. We also discuss the scaling(x_i-x_j)^{-\gamma_{\rm det}} in the conformal phase.

Conformal window in QCD for large numbers of colours and flavours