Varying constants, Gravitation and Cosmology

Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

A particular linear programming model is constructed to predict the diets of each of 14 species of generalist herbivores at the National Bison Range, Montana. The herbivores have body masses ranging over seven orders of magnitude and belonging to two major taxa: insects and mammals. The linear programming model has three feeding constraints: digestive capacity, feeding time and energy requirements. A foraging strategy that maximizes daily energy intake agrees very well with the observed diets. Body size appears to be an underlying determinant of the foraging parameters leading to diet selection. Species that possess digestive capacity and feeding time constraints which approach each other in magnitude have the most generalized diets. The degree that the linear programming models change their diet predictions with a given percent change in parameter values (sensitivity) may reflect the observed ability of the species to vary their diets. In particular, the species which show the most diet variability are those whose diets tend to be balanced between monocots and dicots. The community-ecological parameters of herbivore body-size ranges and species number can possibly be related to foraging behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47765/1/442_2004_Article_BF00377109.pd

Older adults’ preferences for formal social support of autonomy and dependence in pain: development and validation of a scale

Chronic pain among older adults is common and often disabling. Pain-related formal social support (e.g., provided by staff at day-care centres, nursing homes), and the extent to which it promotes functional autonomy or dependence, plays a significant role in the promotion of older adults’ ability to engage in their daily activities. Assessing older adults’ preferences for pain-related social support for functional autonomy or dependence could contribute to increase formal social support responsiveness to individuals’ needs. Therefore, this study aimed at developing and validating the Preferences for Formal Social Support of Autonomy and Dependence in pain Inventory (PFSSADI). One hundred and sixty five older adults with chronic musculoskeletal pain (Mage=79.1, 67.3% women), attending day-care centers, completed the PFSSADI, the revised Formal Social Support for Autonomy and Dependence in Pain Inventory, and a measure of desire for (in)dependence; the PFSSADI was filled out again 6 weeks later. Confirmatory factor analyses showed a structure of two correlated factors (r= .56): (a) Preferences for Autonomy Support (?=.99); and (b) Preferences for Dependence Support (?=.98). The scale showed good test-retest reliability, sensitivity and discriminant and concurrent validity; the higher the preferences for dependence support the higher the desire for dependence (r=.33) and the lower the desire for independence (r=-.41). The PFSSADI is an innovative tool, which may contribute to explore the role of pain-related social support responsiveness on the promotion of older adults’ functional autonomy when in pain.info:eu-repo/semantics/acceptedVersio