Earlysupermassiveblack-holeseedsfrom Kaluza–Klein enhancedsmall-scalestructureformation

Theexistenceof supermassiveblackholes(M≳109M⊙)atredshiftsz≳6
remainsafundamental challenge forthestandardΛCDMcosmologicalmodel. Amajor
bottleneckmaybethescarcityofheavy-seedhosts: inΛCDM,atomic-coolinghalos(M∼
107–108M⊙, Tvir ≳104K) capableof hostingdirect-collapseblackholes (DCBHs) are
exponentiallyrareatz≳12, limitingboththeabundanceofseedsandthetimeavailable
forEddingtonaccretion. Herewe showthat apreviouslyderivedKaluza–Klein (KK)
enhancementofthematterpowerspectrum[19]—arisingfromthefreeze-inofKKmoduli
darkmatterwithh1,1=40K¨ahlermoduli—raisesthecomovingnumberdensityofatomic
coolinghalosby factorsof 6–53(Sheth–Tormen)at z=10–15,withtheenhancement
growingto∼260–800at z=18–20. The samemechanismshifts theeffectivecollapse
epochto substantiallyearlier times, openinga temporalwindowof∆t≳500Myr for
Eddingtonaccretion—sufficient togrowaDCBHseedof105M⊙formedatz≃15to
MBH∼5×109M⊙byz≃7. Crucially, reconcilingthepredictedhaloreservoirwith
theobservedquasarabundancerequiresaseedefficiencyofonlyfseed∼10−10–10−9,well
belowtypicalastrophysical suppressionestimates fromLyman–Wernerregulation,metal
enrichment, orradiative feedback. Noadditionalparametersare introduced: thepower
spectrumenhancementPKK=(8/3)2PΛCDM,derivedfromtheKKfreeze-inmechanismin
Pinto[19], isfixedbythesametopological integerh1,1=40thatdeterminesthedarkmatter
relicdensityanddarkenergyequationofstateinthesameframework.Theenhancement
isasecondaryconsequenceof theKKfreeze-inmechanismalreadyshowntoexplainthe
JWSThigh-redshiftgalaxyexcess, suggestingthatthegalaxyanomalyandtheearlySMBH
populationaretwoobservational facesofthesameunderlyingcosmologicalphysics.