230 research outputs found
The Bullet cluster at its best: weighing stars, gas and dark matter
We present a new strong lensing mass reconstruction of the Bullet cluster (1E
0657-56) at z=0.296, based on WFC3 and ACS HST imaging and VLT/FORS2
spectroscopy. The strong lensing constraints underwent substantial revision
compared to previously published analysis, there are now 14 (six new and eight
previously known) multiply-imaged systems, of which three have
spectroscopically confirmed redshifts (including one newly measured from this
work). The reconstructed mass distribution explicitly included the combination
of three mass components: i) the intra-cluster gas mass derived from X-ray
observation, ii) the cluster galaxies modeled by their fundamental plane
scaling relations and iii) dark matter. The model that includes the
intra-cluster gas is the one with the best Bayesian evidence. This model has a
total RMS value of 0.158" between the predicted and measured image positions
for the 14 multiple images considered. The proximity of the total RMS to
resolution of HST/WFC3 and ACS (0.07-0.15" FWHM) demonstrates the excellent
precision of our mass model. The derived mass model confirms the spatial offset
between the X-ray gas and dark matter peaks. The fraction of the galaxy halos
mass to total mass is found to be f_s=11+/-5% for a total mass of 2.5+/-0.1 x
10^14 solar mass within a 250 kpc radial aperture.Comment: Accepted by A&A 15 pages, 12 figure
Nonquantum Gravity
One of the great challenges for 21st century physics is to quantize gravity
and generate a theory that will unify gravity with the other three fundamental
forces of nature. This paper takes the (heretical) point of view that gravity
may be an inherently classical, i.e., nonquantum, phenomenon and investigates
the experimental consequences of such a model. At present there is no
experimental evidence of the quantum nature of gravity and the liklihood of
definitive tests in the future is not at all certain. If gravity is, indeed, a
nonquantum phenomenon, then it is suggested that evidence will most likely
appear at mesoscopic scales.Comment: essentially the same as the version that appears in Foundations of
Physics, 39, 331 (2009
Contested firm governance, institutions and the undertaking of corporate restructuring practices in Germany
This article investigates the undertaking of corporate restructuring practices (employee downsizing and wage moderation) in Germany from 2008 to 2015. The article presents a political perspective that draws on the insights of the power resources approach and of institutional analyses. The theoretical framework highlights how institutional arrangements structure power relations within companies by empowering, in an asymmetrical manner, different categories of firm stakeholders (employees, managers and shareholders) as well as shaping how they relate to each other in an interactive manner. The articleâs empirical findings point to the importance of extensive, but contingent, corporate restructuring in Germany. Companies are more likely to implement âdefensiveâ corporate restructuring practices under conditions of high leverage/debt than when confronted by shareholder value driven investors, thereby reflecting the presence of overlapping interests between employees and managers
Pain shared, pain halved? Cooperation as a coping strategy for innovation barriers
The paper analyses the relationship between the perception of barriers to innovation and the firmâs propensity to cooperate to mitigate their effect. First, we look at whether cooperation with research organizations or private firms is associated with experiencing different types of barriers, for example, financial constraints, lack of human capital or uncertain market demand. Second, we test whether experiencing several types of barriers simultaneously has a super-modular effect on the propensity to cooperate tout court, and the choice of cooperation partner. We find that having to face a single, specific constraint leads to firms âsharing the painâ with cooperation partnersâboth research organization and other firms. However, the results of a super-modularity test show that having to cope with different barriers is a deterrent to establishing cooperation agreements, especially when firms lack finance, adequate skills and information on technology or markets. The paper adds to the innovation literature by identifying the factors associated with firmsâ coping with different barriers by applying a selective cooperation strategy
Women's experiences of postnatal distress: a qualitative study
Women can experience a range of psychological problems after birth, including anxiety, depression and adjustment disorders. However, research has predominantly focused on depression. Qualitative work on women's experiences of postnatal mental health problems has sampled women within particular diagnostic categories so not looked at the range of potential psychological problems. The aims of this study were to explore how women experienced and made sense of the range of emotional distress states in the first postnatal year
Bank performance and executive pay: tournament or teamwork
We investigate the relationship between the dispersion of executive pay and bank performance/valuation by examining two competing theories, the tournament theory (hierarchical wage structure) and the equity fairness theory (compressed wage structure). The key variable of executive pay dispersion is measured using a hand-collected dataset composed of 63 banks from OECD countries and 29 banks from developing countries. The dataset covers the period 2004 to 2012. By combining and modifying a translog profit function and a pay-dispersion model, we are able to address the potential problems of relying on reduced-form estimation. In our subsample of developed and civil law countries, where bank performance is measured by either Tobinâs Q or by the price-to-book ratio, the overall impact of executive pay dispersion is mostly negative, and we find supporting evidence for the equity fairness theory, except for very high levels of dispersion. There is a non-linear effect, as banks perform best when there is either very low or very high executive pay dispersion. For developing country sample banks, greater executive pay dispersion has a negative impact on bank profit. In our subsample of common law countries, however, we find no evidence of a significant impact of executive pay dispersion on bank performance. We conclude that lower executive pay dispersion, a proxy for teamwork, is mostly effective in enhancing bank performance in a significant section of sample banks, i.e., civil law and developing countries
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