Bad Babies; or, Vacuum Selection and The Arrow of Time
Year: 2007
Type: preprint
Abstract: Even if string theory has a landscape of internally consistent universes, and even if one has a mechanism for actually creating these universes [as “baby universes”], it may well prove to be the case that the babies will not resemble the Universe we observe. For they may not have an Arrow of time: even if some of them have basic physical laws essentially identical to those we have discovered, they may have the wrong initial conditions. We argue that it is extremely difficult, indeed probably impossible, for a baby universe to have an Arrow of time [of the kind we observe]. Therefore it cannot resemble our Universe. The only Universe[s] with an Arrow like ours may be the one[s] that was [were] “created from nothing”, in accordance with the Ooguri-Vafa-Verlinde “entropic principle”.1. The Arrow of Time and its Uses One of the most basic observations about our Universe is also one of the most difficult to explain: the existence of an Arrow of time [1][2][3][4]. Whether one examines the entropy that the early Universe might have had due to black holes [1] or uses “holographic” estimates of that entropy [4], the conclusion is that the initial conditions must have been “non-generic ” to an almost unimaginable degree. The difficulties involved in explaining this extraordinary feature of the Universe have recently attracted some attention, leading to a variety of proposed solutions [5][6][7][8]. In this challenge, however, there lies a great opportunity. For if an Arrow of time is something that is very difficult to establish, if in fact extremely few universes have an Arrow, then the Arrow becomes a powerful tool for selecting universes in any theory that presents us with a multitude of them. That is, demanding the existence of an Arrow may allow us to rule out large classes of universes which might have exactly the right gauge group, spectrum of particles, and so on — which might, in short, have everything except the right initial conditions. The importance of settling this question can hardly be overstated: in particular, it is clear that nothing meaningful can be said about populating the string landscape [9] until one has a good understanding of the Arrow. For whatever an “observer ” may be, one can feel confident that such devices do not exist if there is no
Source: arXiv (Cornell University)
Author: Brett McInnes
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2292050945