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 discuss two dimensional $QCD (N_c\to\infty)$ with fermions in thefundamental as well as adjoint representation. We find factorial growth $\sim(g^2N_c\pi)^{2k}\frac{(2k)!(-1)^{k-1}}{(2 \pi)^{2k}}$ in the coefficients ofthe large order perturbative expansion. We argue that this behavior is relatedto classical solutions of the theory, instantons, thus it has nonperturbativeorigin. Phenomenologically such a growth is related to highly excited states inthe spectrum. We also analyze the heavy-light quark system $Q\bar{q}$ withinoperator product expansion (which it turns out to be an asymptotic series).Some vacuum condensates $\la\bar{q}(x_{\mu}D_{\mu})^{2n}q\ra\sim (x^2)^n\cdotn!$ which are responsible for this factorial growth are also discussed. Weformulate some general puzzles which are not specific for 2D physics, but areinevitable features of any asymptotic expansion. We resolve these apparentpuzzles within $QCD_2$ and we speculate that analogous puzzles might occur inreal 4-dimensional QCD as well.Comment: latex, 26 pages. A final version to appear in Phys. Rev.

physical review. d. particles, fields, gravitation, and cosmology/physical review. d. particles and fields

Lessons from two-dimensional QCD (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>→</mml:mo><mml:mi>∞</mml:mi></mml:math>): Vacuum structure, asymptotic series, instantons, and all that

Lessons from two-dimensional QCD (N→∞): Vacuum structure, asymptotic series, instantons, and all that