Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr

Why we choose, how we choose, what we choose: the influence of decision initiation motives on decision making

Ilona McNeill wilde inzicht krijgen in waarom mensen beginnen met het nemen van beslissingen, en hoe hun redenen vervolgens hun keuze beïnvloeden. Zo kan je op zoek gaan naar een nieuwe telefoon, omdat je oude kapot is gegaan (het is noodzaak). Maar je kan ook op zoek gaan naar een nieuwe telefoon, omdat je het wel tijd vindt voor een nieuw model (plezier/gemaksmotief). McNeill toont dat onze redenen wel degelijk invloed hebben op hoe we kiezen. Iemand die noodzakelijk een nieuwe telefoon moest hebben, zou wel eens met een ander model de winkel uit zou kunnen lopen dan iemand die vond dat het tijd was voor een nieuw model. McNeill laat ook zien dat er niet een bepaalde manier is van keuzes maken die het beste is voor iedereen. Zo werkt het voor sommige mensen beter om zich tijdens het beslissen te focussen op wat ze kunnen leren van deze beslissing (denk aan algemene wijnkennis bij het uitzoeken van een fles), terwijl andere zich beter gewoon op de uitkomst kunnen richten (het uitzoeken van de juiste wijn voor een bepaalde gelegenheid). Dit heeft niet alleen invloed op welke keuze gemaakt wordt; het heeft ook invloed op hoe men zijn uiteindelijke keuze waardeert. Als je kiest op een wijze die het beste bij jou past, is de kans groot dat je de keuze ook meer waardeert. McNeill concludeert dat als je mensen wilt motiveren om een bepaalde beslissing te nemen, het belangrijk is om niet alleen te kijken naar wat hier het sterkste motief zou kunnen zijn. Kijk vooruit en bedenk je ook welke invloed dit soort motief zal hebben indien er daadwerkelijk met beslissen begonnen wordt

Predicting risk-mitigating behaviors from indecisiveness and trait anxiety: Two cognitive pathways to task avoidance

Past research suggests that indecisiveness and trait anxiety may both decrease the likelihood of performing risk-mitigating preparatory behaviors (e.g., preparing for natural hazards) and suggests two cognitive processes (perceived control and worrying) as potential mediators. However, no single study to date has examined the influence of these traits and processes together. Examining them simultaneously is necessary to gain an integrated understanding of their relationship with risk-mitigating behaviors. We therefore examined these traits and mediators in relation to wildfire preparedness in a two-wave field study among residents of wildfire-prone areas in Western Australia (total N = 223). Structural equation modeling results showed that indecisiveness uniquely predicted preparedness, with higher indecisiveness predicting lower preparedness. This relationship was fully mediated by perceived control over wildfire-related outcomes. Trait anxiety did not uniquely predict preparedness or perceived control, but it did uniquely predict worry, with higher trait anxiety predicting more worrying. Also, worry trended toward uniquely predicting preparedness, albeit in an unpredicted positive direction. This shows how the lack of performing risk-mitigating behaviors can result from distinct cognitive processes that are linked to distinct personality traits. It also highlights how simultaneous examination of multiple pathways to behavior creates a fuller understanding of its antecedents

Predicting delay in residents’ decisions on defending v. evacuating through antecedents of decision avoidance

In the event of a wildfire, Australian residents of wildfire-prone areas have a choice to defend their home or evacuate early. However, rather than deciding on and preparing for one of these fire-responses ahead of time, most residents delay deciding on defending v. evacuating (e.g. they wait and see instead). Recent research has shown that delaying this decision is associated with reduced levels of preparedness for both responses and on the day of a fire, an increased risk to life and property. The current study empirically examined what predicts this decision delay regarding one’s fire-response by measuring two personality traits and several decision-related factors. A longitudinal survey study of residents of multiple wildfire-prone areas in Western Australia showed that the strongest predictor of delaying their decision to defend v. evacuate was a lack of difference in perceived values of defending v. evacuating. These findings have important implications for the design of interventions to reduce the risks associated with such delay. For one, agencies could utilise residents’ value base to reduce decision delay. Alternatively, they could focus on the formation of proper contingency plans and stress the necessity to prepare well for both defending and evacuating

A value- and expectancy-based approach to understanding residents

To motivate residents to evacuate early in case of a wildfire threat, it is important to know what factors underlie their response-related decision-making. The current paper examines the role of the value and expectancy tied to potential outcomes of defending vs evacuating on awareness of a community fire threat. A scenario study among 339 Western Australians revealed that residents intending to leave immediately on awareness of a community fire threat differ from those not intending to leave immediately in both value and expectancy. For one, intended leavers were more likely than those intending to defend their property to have children. Also, the data showed a trend towards intended leavers being less likely to have livestock. Furthermore, intended leavers placed less importance on the survival of their property than those with other expressed intentions. They also reported lower expectancies regarding the likelihood of achieving positive outcomes by defending than those intending to defend or wait and see before deciding what to do. Finally, intended leavers perceived it more likely that they would avoid harm to their pets by evacuating than those intending to defend throughout or wait and see. These findings have important implications for strategies to influence residents’ response-related decision-making

The price of a piece of cheese:Value from fit between epistemic needs and a learning versus outcome focus

In decision making, people can focus on decisional outcomes (outcome focus), but they can also focus on gaining knowledge about the decisional domain (learning focus). Furthermore, people differ in the strength of their epistemic needstheir preference for developing a rich and accurate understanding of the world. We invoke the regulatory fit theory to predict that higher epistemic needs better fit a learning focus than lower epistemic needs, resulting in a greater increase in valuation of the chosen option when a learning rather than an outcome focus is induced. This general hypothesis was tested and supported in three studies, each focusing on a different proxy to epistemic needs. Thus, individuals experienced greater value when they had lower expertise (Study 1), higher need for assessment (Study 2), and higher need for cognition (Study 3) when a learning rather than an outcome focus was induced. Implications for work on epistemic needs, regulatory fit theory, and decision-making practice are discussed. Copyright (C) 2011 John Wiley & Sons, Ltd