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# The past light-come of C 2 at τ = −1 and the past light cone of C 1 between τ and τ + δτ for τ > r − 1.

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In a metastable de Sitter space any object has a finite life expectancy
beyond which it undergoes vacuum decay. However, by spreading into different
parts of the universe which will fall out of causal contact of each other in
future, a civilization can increase its collective life expectancy, defined as
the average time after which the last settlem...

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## Citations

... the number of membranes that hit an observer per unit time. We will now do so by geometric means, as in [37]. ...

... This equation gives the probability that a bubble which was born at conformal time τ 0 actually makes it to conformal time τ (see [37]). In terms of proper time, we have ...

A number of Swampland conjectures and in particular the Trans-Planckian Censorship Conjecture (TCC) suggest that de Sitter space is highly unstable if it exists at all. In this paper we construct effective theories of scalars rolling on potentials which are dual to a chain of short-lived dS spaces decaying from one to the next through a cascade of non-perturbative nucleation of bubbles. We find constraints on the effective potential resulting from various swampland criteria, including TCC, Weak Gravity Conjecture and Distance Conjecture. Surprisingly we find that TCC essentially incorporates all the other ones, and leads to a subclass of possible dual effective potentials. These results marginally rule out emergence of eternal inflation in the dual effective theory. We discuss some cosmological implications of our observations.

... The work[30] discusses these points in great detail, including implications for holography. Related lifetimes for dS or general FLRW spacetimes are also discussed in[31]. We thank Ashoke Sen for brining these subtleties and references to our attention.5 ...

A bstract
Constructing an explicit compactification yielding a metastable de Sitter (dS) vacuum in a UV consistent string theory is an incredibly difficult open problem. Motivated by this issue, as well as the conjecture that all non-supersymmetric AdS vacua must decay, we discuss the alternative possibility of realizing an effective four-dimensional dS cosmology on a codimension-one bubble wall separating two AdS 5 vacua. The construction further elaborates on the scenario of arXiv:1807.01570 , where the aforementioned cosmology arises due to a non-perturbative decay and is embedded in a five-dimensional bulk in a time dependent way. In this paper we discuss the relation between this scenario and the weak gravity conjecture and further develop the details of the four-dimensional cosmology. We provide a bulk interpretation for the dS temperature as the Unruh temperature experienced by an accelerated observer riding the bubble. A source of four-dimensional matter arises from a string cloud in the bulk, and we examine the consequences for the particle mass spectrum. Furthermore, we show how effective four-dimensional Einstein gravity on the bubble is obtained from the five-dimensional Gauss equation. We conclude by outlining some implications that this paradigm will have for holography, inflation, the standard model, and black holes.

... [7][8][9] ). When discussing the future of our Universe and illustrating how a continuing accelerated expansion would look like, one again appeals to "future cosmology" in both research [10][11][12][13] and popular science articles. [14][15][16][17] A lot of research and popular literature has been devoted to the subject of habitable planets, where one often "depicts" how life would look like with different kinds of suns 18 including "life in the early Universe". ...

It is generally believed that in the epoch prior to the formation of the first stars, the Universe was completely dark (the period is therefore known as the Dark Ages). Usually the start of this epoch is placed at the photon decoupling. In this work we investigate the question whether there was enough light during the dark epoch for a human eye to see. We use the black body spectrum of the Universe to find the flux of photon energy for different temperatures and compare them with visual limits of blindness and darkness. We find that the Dark Ages actually began approximately 5 million years later than commonly stated.

A number of Swampland conjectures and in particular the Trans‐Planckian Censorship Conjecture (TCC) suggest that de Sitter space is highly unstable if it exists at all. In this paper we construct effective theories of scalars rolling on potentials which are dual to a chain of short‐lived dS spaces decaying from one to the next through a cascade of non‐perturbative nucleation of bubbles. We find constraints on the effective potential resulting from various swampland criteria, including TCC, Weak Gravity Conjecture and Distance Conjecture. Surprisingly we find that TCC essentially incorporates all the other ones, and leads to a subclass of possible dual effective potentials. These results marginally rule out emergence of eternal inflation in the dual effective theory. We discuss some cosmological implications of our observations.