The EFT stringy viewpoint on large distances

A bstract We observe a direct relation between the existence of fundamental axionic strings, dubbed EFT and infinite distance limits in 4d $$ \mathcal{N} N = 1 EFTs coupled to gravity. The backreaction strings can be interpreted as RG flow their couplings, allows one probe different regimes within field space theory. propose that any limit realised an string flow. show along such becomes asymptotically tensionless, so eventually breaks down. This provides upper bound for maximal range with finite cut-off, reproduces Swampland Distance Conjecture from bottom-up perspective. Even if there are typically other towers particles becoming light, we mass leading tower scales m 2 ? \mathcal{T} T w Planck units, tension positive integer. Our results hold even presence non-trivial potential, long its energy scale remains well below cut-off. check both proposals large classes compactifications, finding only values , 3 realised.