Physics, Astrophysics and Cosmology with Gravitational Waves

Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers), and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version <http://www.livingreviews.org/lrr-2009-2

An acetylated form of histone H2A.Z regulates chromosome architecture in Schizosaccharomyces pombe

Histone variant H2A.Z has a conserved role in genome stability, although it remains unclear how this is mediated. Here we demonstrate that the fission yeast Swr1 ATPase inserts H2A.Z (Pht1) into chromatin and Kat5 acetyltransferase (Mst1) acetylates it. Deletion or an unacetylatable mutation of Pht1 leads to genome instability, primarily caused by chromosome entanglement and breakage at anaphase. This leads to the loss of telomere-proximal markers, though telomere protection and repeat length are unaffected by the absence of Pht1. Strikingly, the chromosome entanglement in pht1Delta anaphase cells can be rescued by forcing chromosome condensation before anaphase onset. We show that the condensin complex, required for the maintenance of anaphase chromosome condensation, prematurely dissociates from chromatin in the absence of Pht1. This and other findings suggest an important role for H2A.Z in the architecture of anaphase chromosomes

The Power of the Weak: How Informal Power-Sharing Shapes the Work of the UN Security Council

To what extent is the work of international organizations shaped by their most powerful members? Can minor powers influence the decisions taken by these organizations? This dissertation presents the argument that great powers engage in power-sharing in order to attain unanimity inside international organizations, which enhances compliance and increases the effect of the signals these organizations convey to the public. The pursuit of unanimity lends weight even to votes that are not needed for the adoption of a proposal under the formal rules. It enables minor powers to exert more influence inside international organizations than they could if the formal rules and/or the balance of material power between member states determined the outcome of decision-making in international organizations. An analysis of the UN Security Council tests this argument. The dissertation identifies a series of informal power-sharing practices in the Security Council, which systematically depart from the organization's formal rules, and which promote consensus and augment minor powers' influence far beyond what one would expect on the basis of the material capabilities and voting power of these states. In turn, these informal power-sharing practices are motivated by great powers' desire to attain unanimous support for the policies enacted in the Security Council, irrespective of the body's formal voting rules. Survey experiments demonstrate the rationale behind great powers' pursuit of unanimity. They show that a policy's endorsement by a united Security Council has a much larger signaling effect on public opinion than the policy's approval by a divided Council. Qualitative case studies and novel design-based causal inference that exploits natural experiments show that minor powers strongly influence the deployment of UN peace operations and UN counter-terrorism sanctions, and that minor powers also use their influence in the Council to attain side-payments. Minor powers' influence is particularly strong during crises, when great powers are most eager to secure small states' votes through power-sharing. Interviews with diplomats in seven countries and quantitative analyses of exogenous variation in minor powers' representation on the Security Council under pre-determined rotation rules trace minor powers' influence to informal power-sharing practices in the Council

Upper limits on gravitational wave emission from 78 radio pulsars

We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO 600 gravitational wave detectors. The data from both runs have been combined coherently to maximize sensitivity. For the first time, pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor of 10. For example, our tightest upper limit on the gravitational strain is 2.6×10-25 for PSR J1603-7202, and the equatorial ellipticity of PSR J2124–3358 is less than 10-6. Furthermore, our strain upper limit for the Crab pulsar is only 2.2 times greater than the fiducial spin-down limit