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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present a broad conceptual introduction to some new ideas innon-perturbative QFT. The large-$N$ orbifold-orientifold equivalence connects anatural large-$N$ limit of QCD to QCD with adjoint fermions. QCD(adj) withperiodic boundary conditions and double-trace deformation of Yang-Mills theorysatisfy large-$N$ volume independence, a type of orbifold equivalence. CertainQFTs that satisfy volume independence at $N=\infty$ exhibit adiabaticcontinuity at finite-$N$, and also become semi-classically calculable on small$\mathbb R^3 \times S^1$. We discuss the role of monopole-instantons, andmagnetic and neutral bion saddles in connection to mass gap, and center andchiral symmetry realizations. Neutral bions also provide a weak couplingsemiclassical realization of infrared-renormalons. These considerations helpmotivate the necessity of complexification of path integrals (Picard-Lefschetztheory) in semi-classical analysis, and highlights the importance of hiddentopological angles. Finally, we briefly review the resurgence program, whichpotentially provides a novel non-perturbative continuum definition of QFT. Allthese ideas are continuously connected.

New Methods in QFT and QCD: From Large-N Orbifold Equivalence to Bions and Resurgence