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

The mutual information $I(A,B)$ of pairs of spatially separated regionssatisfies, for any $d$-dimensional CFT, a set of structural physical propertiessuch as positivity, monotonicity, clustering, or Poincar\'e invariance, amongothers. If one imposes the extra requirement that $I(A,B)$ is extensive as afunction of its arguments (so that the tripartite information vanishes for anyset of regions, $I_3(A,B,C)\equiv 0$), a closed geometric formula involvingintegrals over $\partial A$ and $\partial B$ can be obtained. We explorewhether this "Extensive Mutual Information" model (EMI), which in factdescribes a free fermion in $d=2$, may similarly correspond to an actual CFT ingeneral dimensions. Using the long-distance behavior of $I_{\rm\scriptscriptstyle EMI}(A,B)$ we show that, if it did, it would necessarilyinclude a free fermion, but also that additional operators would have to bepresent in the model. Remarkably, we find that $I_{\rm \scriptscriptstyleEMI}(A,B)$ for two arbitrarily boosted spheres in general $d$ exactly matchesthe result for the free fermion current conformal block$G^d_{\Delta=(d-1),J=1}$. On the other hand, a detailed analysis of thesubleading contribution in the long-distance regime rules out the possibilitythat the EMI formula represents the mutual information of any actual CFT oreven any limit of CFTs. These results make manifest the incompleteness of theset of known constraints required to describe the space of allowed entropyfunctions in QFT.

Is the EMI model a QFT? An inquiry on the space of allowed entropy functions