824 research outputs found
Survival, reproduction and congestion: The spaceship problem re-examined
This paper re-examines the spaceship problem, i.e. the design of the optimal population under a fixed living space, by focusing on the dilemma between adding new beings and extending the life of existing beings. For that purpose, we characterize, under time-additive individual welfare depending negatively on population density, the preference ordering of a utilitarian social planner over lifetime-equal histories, i.e. histories with demographic conditions yielding an equal finite number of life-periods (imposed by resources constraints). The analysis of the spaceship problem contradicts widespread beliefs about the populationism of Classical Utilitarianism and the antipopulationism of Average Utilitarianism. We also study the invariance property exhibited by various utilitarian rankings to the total space available and to individual preferences. Finally, we compare histories for a spaceship with a stationary population, and try to accomodate intuitions about posterity and renewal of populations.environmental congestion ; fertility ; longevity ; population ethics ; utilitarianism ; renewal
The unphysical nature of "Warp Drive"
We will apply the quantum inequality type restrictions to Alcubierre's warp
drive metric on a scale in which a local region of spacetime can be considered
``flat''. These are inequalities that restrict the magnitude and extent of the
negative energy which is needed to form the warp drive metric. From this we are
able to place limits on the parameters of the ``Warp Bubble''. It will be shown
that the bubble wall thickness is on the order of only a few hundred Planck
lengths. Then we will show that the total integrated energy density needed to
maintain the warp metric with such thin walls is physically unattainable.Comment: 11 pages, 3 figures, latex. This revision corrects a typographical
sign error in Eq. (3
On Logical Analysis of Relativity Theories
The aim of this paper is to give an introduction to our axiomatic logical
analysis of relativity theories.Comment: 19 pages, 1 figure
Doubly-Special Relativity: First Results and Key Open Problems
I examine the results obtained so far in exploring the recent proposal of
theories of the relativistic transformations between inertial observers that
involve both an observer-independent velocity scale and an observer-independent
length/momentum scale. I also discuss what appear to be the key open issues for
this research line.Comment: 29 page
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