Surviving in a Metastable de Sitter Space-Time

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 settlement disappears due to vacuum decay. We study in detail the collective life expectancy of two comoving objects in de Sitter space as a function of the initial separation, the horizon radius and the vacuum decay rate. We find that even with a modest initial separation, the collective life expectancy can reach a value close to the maximum possible value of 1.5 times that of the individual object if the decay rate is less than 1% of the expansion rate. Our analysis can be generalized to any number of objects, general trajectories not necessarily at rest in the comoving coordinates and general FRW space-time. As part of our analysis we find that in the current state of the universe dominated by matter and cosmological constant, the vacuum decay rate is increasing as a function of time due to accelerated expansion of the volume of the past light cone. Present decay rate is about 3.7 times larger than the average decay rate in the past and the final decay rate in the cosmological constant dominated epoch will be about 56 times larger than the average decay rate in the past. This considerably weakens the lower bound on the half-life of our universe based on its current age.

Comments: LaTex file, 36 pages, 14 figures; v2: appendix added giving computation of decay rate for general equation of state

Similar Publications

We give a brief overview of the current status of Double Field Theory on Group Manifolds (DFTWZW). Therefore, we start by reviewing some basic notions known from Double Field Theory (DFT) and show how they extend/generalize into the framework of Double Field Theory on Group Manifolds. In this context, we discuss the relationship between both theories and the transition from DFTWZW to DFT. Read More

We study the supersymmetric extensions of the $O(3)$ $\sigma$-model in $1+1$ and $2+1$ dimensions. We show that it is possible to construct non-equivalent supersymmetric versions of a given model sharing the same bosonic sector and free from higher-derivative terms. Read More

We generalize the method of computing functional determinants with excluded zero mode developed by McKane and Tarlie to the differential operators with degenerate zero modes. We consider a $2\times 2$ matrix differential operator with two independent zero modes and show that its functional determinant can be expressed only in terms of these modes in the spirit of Gel'fand-Yaglom approach. Our result can be easily extended to the case of $N\times N$ matrix differential operators with $N$ zero modes. Read More

We study spin chain analogs of the two-dimensional Kitaev honeycomb lattice model, which allows us to relate Anderson resonating valence bond states with superconductivity in an exact manner. In addition to their connection with p-wave superconductivity, such chains can be used for topological quantum computation as a result of the emergent Z_2 symmetry, as we show using Majorana fermions. We then focus on the problem of two coupled chains (ladders) : using Majorana fermions, we derive an analytical expression for the energy spectrum in the general case, which allows us to compare the square ladder and the honeycomb ribbon. Read More

We study the projective properties of planar zeros of tree-level scattering amplitudes in various theories. Whereas for pure scalar field theories we find that the planar zeros of the five-point amplitude do not enjoy projective invariance, coupling scalars to gauge fields gives rise to tree-level amplitudes whose planar zeros are determined by homogeneous polynomials in the stereographic coordinates labelling the direction of flight of the outgoing particles. In the case of pure gauge theories, this projective structure is generically destroyed if string corrections are taken into account. Read More

We conjecture a formula for the generating function of virtual $\chi_y$-genera of moduli spaces of rank 2 sheaves on minimal surfaces of general type. Specializing this conjecture to virtual Euler characteristics, we recover (part of) a formula of C. Vafa and E. Read More

We extend the idea of conformal attractors in inflation to non-canonical sectors by developing a non-canonical conformally invariant theory from two different approaches. In the first approach, namely, ${\cal N}=1$ supergravity, the construction is more or less phenomenological, where the non-canonical kinetic sector is derived from a particular form of the K$\ddot{a}$hler potential respecting shift symmetry. In the second approach i. Read More

A semi-classical analysis of backreaction in an expanding Universe with a conformally coupled scalar field and vacuum energy is presented. It is shown that a local observer perceives de Sitter space to contain a constant thermal energy density despite the dilution from expansion due to a continuous flux of energy radiated from the horizon. The self-consistent solution for the Hubble rate is found to be gradually evolving and at late times deviates significantly from de Sitter. Read More

In this paper we systematically construct simply transitive homogeneous spacetime solutions of the three-dimensional Minimal Massive Gravity (MMG) model. In addition to those that have analogs in Topologically Massive Gravity, such as warped AdS and pp-waves, there are several solutions genuine to MMG. Among them, there is a stationary Lifshitz metric with the dynamical exponent z=-1 and an anisotropic Lifshitz solution where all coordinates scale differently. Read More

Both classical and quantum waves can form vortices: with helical phase fronts and azimuthal current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. Read More