# Shadow Extra Dimension & Fuzzy Branes via Exorcized Infinite Derivative Field Theory

Authors
Publication Date
Jan 18, 2022
Source
HAL
Keywords
Language
English
Particle physics models with extra dimensions of space (EDS's) and branes are very interesting extensions beyond the standard model (BSM), allowing to shed new light on electroweak and flavor naturalness. Usually, such models are formulated in the framework of \emph{local} effective field theories (EFT's). The scope of this article is to propose new model building issues in BSM constructions with EDS and branes, arising in the framework of \emph{exorcized} (ghost-free) \emph{infinite derivative field theories} (IDFT's), which are intrinsically \emph{nonlocal} above some ultraviolet (UV) scale $\Lambda_{NL}$. First, with a warped EDS, the warp transmutation of the mass term of a brane-localized scalar field is revisited, where it is shown that $\Lambda_{NL}$ is also redshifted. This may provide a new way to solve the little hierarchy problem related to the Higgs boson mass. Moreover, if the (redshifted) $\Lambda_{NL}$ is around the mass scale of the first Kaluza-Klein (KK) excitations of the bulk fields, it is argued that it would be much more difficult to probe the KK tower in an experiment, which is reminiscent to the UV opaqueness of IDFT's: such EDS is then dubbed \emph{shadow}. After that, it is shown that a 4D field localized on a $\delta$-like 3-brane is still delocalized in the bulk on a distance $\mathcal{O}(1/\Lambda_{NL})$ of the brane position, such as 2 fields localized on 2 different $\delta$-like branes are allowed to interact with suppressed couplings, which is impossible in a local EFT. By using this new possibility of \emph{fuzzy} branes, a new realization of the split fermion idea is presented, allowing to build new BSM models of flavor.