The effect of structure formation on the expansion of the universe

Observations of the expansion rate of the universe at late times disagree by a factor of 1.5-2 with the prediction of homogeneous and isotropic models based on ordinary matter and gravity. We discuss how the departure from linearly perturbed homogeneity and isotropy due to structure formation could explain this discrepancy. We evaluate the expansion rate in a dust universe which contains non-linear structures with a statistically homogeneous and isotropic distribution. The expansion rate is found to increase relative to the exactly homogeneous and isotropic case by a factor of 1.1-1.3 at some tens of billion of years. The timescale follows from the cold dark matter transfer function and the amplitude of primordial perturbations without additional free parameters.Comment: 6 pages, 1 figure. Awarded Honorable Mention in the 2008 Gravity Research Foundation essay competition. More extended treatment of the topics can be found in arXiv:0801.2692v

Cosmological acceleration from structure formation

We discuss the Buchert equations, which describe the average expansion of an inhomogeneous dust universe. In the limit of small perturbations, they reduce to the Friedmann-Robertson-Walker equations. However, when the universe is very inhomogeneous, the behaviour can be qualitatively different from the FRW case. In particular, the average expansion rate can accelerate even though the local expansion rate decelerates everywhere. We clarify the physical meaning of this paradoxical feature with a simple toy model, and demonstrate how acceleration is intimately connected with gravitational collapse. This provides a link to structure formation, which in turn has a preferred time around the era when acceleration has been observed to start.Comment: 6 pages, awarded honorable mention in the 2006 Gravity Research Foundation essay competitio

Collaboration and Research Practice in Intelligence

Close, intensive research collaboration between universities, companies, and the public sector can open up new and different opportunities for qualitative research, and provide analytic and empirical insights that otherwise might be difficult to obtain. The aim of this paper is to explore collaboration as a means of doing research with the intelligence community. Experiences from a research project concerning dilemmas the practitioners face in their organization within the Swedish Armed Forces, serve as a starting point for this reflective discussion. It is argued here that collaboration is suitable when change is required. The mutual learning between the actors feeds into change processes. However, such collaboration raises fundamental ethical issues that are complex and highlight various academic, institutional, and personal perspectives. Collaborations should not be a set of “how-to” recipes, but rather a research activity that can have substantial rewards for researchers and practitioners alike

Against the impairment argument: A reply to Hendricks

In an article of this journal, Perry Hendricks makes a novel argument for the immorality of abortion. According to his impairment argument, abortion is immoral because: (a) it is wrong to impair a fetus to the nth degree, such as causing the fetus to have fetal alcohol syndrome (FAS); (b) it is wrong to impair a fetus to the n+1 degree (to cause the fetus to be more impaired than to have FAS); (c) killing the fetus impairs the fetus to the n+1 degree (causes it to be more impaired than to have FAS); (d) abortion kills the fetus; (e) therefore, abortion is immoral. The impairment argument is a promising account for the wrongness of abortion because it does not rely on the controversial metaphysical premise that a fetus is a person. This article aims to show, that despite some immediate advantages over the rival theories of the immorality of abortion there is a reason to believe that the impairment argument is untenable. That is because there are goods that can be achieved by abortion but that cannot be achieved by impairing the fetus

Moral Case for Legal Age Change

Should a person who feels his legal age does not correspond with his experienced age be allowed to change his legal age? In this paper, I argue that in some cases people should be allowed to change their legal age. Such cases would be when: 1) the person genuinely feels his age differs significantly from his chronological age and 2) the person’s biological age is recognized to be significantly different from his chronological age and 3) age change would likely prevent, stop or reduce ageism, discrimination due to age, he would otherwise face. I also consider some objections against the view that people should be allowed to change their legal age and find them lacking