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A Larger Estimate of the Entropy of the Universe

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arxiv 0909.3983 v3 pith:CWRBM2GN submitted 2009-09-22 astro-ph.CO

A Larger Estimate of the Entropy of the Universe

classification astro-ph.CO
keywords entropyuniverseobservableestimatemakeblackcalculatecaveats
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Using recent measurements of the supermassive black hole (SMBH) mass function, we find that SMBHs are the largest contributor to the entropy of the observable universe, contributing at least an order of magnitude more entropy than previously estimated. The total entropy of the observable universe is correspondingly higher, and is S_obs = 3.1+3.0-1.7x10^104 k. We calculate the entropy of the current cosmic event horizon to be S_CEH = 2.6+-0.3x10^122 k, dwarfing the entropy of its interior, S_CEHint = 1.2+1.1-0.7x10^103 k. We make the first tentative estimate of the entropy of weakly interacting massive particle dark matter within the observable universe, S_dm = 10^87-10^89 k. We highlight several caveats pertaining to these estimates and make recommendations for future work.

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