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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Using recent results from numerical relativity simulations of black holemergers, we revisit previous studies of cosmological black hole spin evolution.We show that mergers are very unlikely to yield large spins, unless alignmentof the spins of the merging holes with the orbital angular momentum is veryefficient. We analyze the spin evolution in three specific scenarios: (1) spinevolves only through mergers, (2) spin evolves through mergers and prolongedaccretion episodes, (3) spin evolves through mergers and short-lived (chaotic)accretion episodes. We study how different diagnostics can distinguish betweenthese evolutionary scenarios, assessing the discriminating power ofgravitational-wave measurements and X-ray spectroscopy. Gravitational radiationcan produce three different types of spin measurements, yielding respectivelythe spins of the two black holes in a binary inspiral prior to merger, the spinof the merger remnant (as encoded in the ringdown waves), and the spin of``single'' black holes during the extreme mass-ratio inspiral (EMRI) of compactobjects. The latter spin population is also accessible to iron-linemeasurements. We compute and compare the spin distributions relevant for thesedifferent observations. If iron-line measurements and gravitational-waveobservations of EMRIs only yield dimensionless spins j=J/M^2>0.9, thenprolonged accretion should be responsible for spin-up, and chaotic accretionscenarios would be very unlikely. If only a fraction of the whole population oflow-redshift black holes spins rapidly, spin-alignment during binary mergers(rather than prolonged accretion) could be responsible for spin-ups.

Cosmological black hole spin evolution by mergers and accretion