Inferring black-hole orbital dynamics from numerical-relativity gravitational waveforms

Binary-black-hole dynamics cannot be related to the resulting gravitational-wave signal by a constant retarded time. This is due to the non-trivial dynamical spacetime curvature between the source and the signal. In a numerical-relativity simulation there is also some ambiguity in the black-hole dynamics, which depend on the gauge (coordinate) choices used in the numerical solution of Einstein's equations. It has been shown previously that a good approximation to the direction of the binary's time-dependent orbital angular momentum $\mathbf{\hat{L}}(t)$ can be calculated from the gravitational-wave signal. This is done by calculating the direction that maximises the quadrupolar $(\ell=2,|m|=2)$ emission. The direction depends on whether we use the Weyl scalar $\psi_4$ or the gravitational-wave strain $h$, but these directions are nonetheless invariant for a given binary configuration. We treat the $\psi_4$-based direction as a proxy to $\mathbf{\hat{L}}(t)$. We investigate how well the the binary's orbital phase, $\phi_{\rm orb}(t)$, can also be estimated from the signal. For this purpose we define a quantity $\Phi(t)$ that agrees well with $\phi_{\rm orb}(t)$. One application is to studies that involve injections of numerical-relativity waveforms into gravitational-wave detector data.Comment: 12 pages with 10 figure

Gender and family firms: an interdisciplinary approach

This study contributes to developing our understanding of gender and family business, a topic so crucial to recent policies about competitive growth. It does so by providing an interdisciplinary synthesis of some major theoretical debates. It also contributes to this understanding by illuminating the role of women and their participation in the practices of the family and the business. Finally, it explores gender relations and the notion that leadership in family business may take complex forms crafted within constantly changing relationships. Leadership is introduced as a concept that captures the reality of women and men in family firms in a better way than other concepts used by historians or economists like ownership and management.genere, gender, empresa familiar, family firms, leadership, lideratge

Measurability of precession and eccentricity for heavy binary-black-hole mergers

Gravitational wave detections offer insights into the astrophysical populations of black holes in the universe and their formation processes. Detections of binaries consisting of black holes lying outside the bulk distribution of the astrophysical population are particularly intriguing. In this study, we perform an injection analysis within the intermediate-mass black hole range, utilizing the NR surrogate model NRSur7dq4 and a selection of NR waveforms from the SXS and RIT catalogues. Our investigation focuses on the detectability of precession and its potential degeneracy with eccentricity, especially for short signals with only a few cycles in band. While total mass, mass ratio, and $\chi_\mathrm{eff}$ are generally well recovered, the recovery of $\chi_\mathrm{p}$ is largely limited, and noise significantly impacts the recovery of some parameters for short signals. We also find that eccentricity lower than 0.2 is insufficient to mimic precession in parameter estimation when assuming a quasi-circular signal. Our results suggest that a certain degree of precession is necessary to produce evidence of high precession in parameter estimation, but it remains challenging to conclusively determine which effect is responsible for the high precession observed in events like GW190521. We emphasize the importance of caution when interpreting properties of a binary from short signals and highlight the potential benefits of future third generation detectors and eccentric waveform models for more exhaustive exploration of parameter space.Comment: 16 pages, 13 figure

Iowa State Welcomes New Dean of Home Economics: Faculty Adds Fifteen to Staff

With the arrival of Miss Anna J. Richardson in Ames in time for winter quarter registration, Iowa State will welcome her new dean of the Home Economics division. Miss Edna Walls, who has served as acting dean since the death of Dean MacKay in August, 1921, will continue as vice-dean

Towards a precision description of precessing black-hole-binaries

There have been a number of gravitational wave events detected by the LIGO and Virgo detectors in recent years. Aside from simply detecting these signals we want to be able to make confident statements about the properties of the systems that emit them-- such as the masses and spins of the compact objects that make up the binaries that produce gravitational waves. Inferring these properties enables us to draw conclusions about the population of compact binaries in the universe and their formation mechanisms. To do this we compare the detected signals with theoretical predictions of the signals from sources with known properties. The aim of this thesis has been to provide a precision description of precessing black-hole-binary systems and the gravitational wave signals they produce. Due to the non-linearity of the Einstein equation, we can only obtain analytical solutions for the gravitational waves emitted by a source while the two black holes are inspiralling towards each other. Obtaining the waveforms during merger and ringdown requires numerical relativity. In order to explore the phenomenology of precessing signals we produced a catalogue of single spin numerical relativity simulations spanning the precessing parameter space up to mass ratio 8 and spin magnitude 0.8. The waveforms from these simulations can be used for direct comparisons with detected signals or for the development of waveform models. The catalogue presented here provides the basis of the tuned precessing model that forms the bulk of this thesis. We also further developed a method to reliably specify the orientation of a precessing binary at a given point in the waveform. For waveforms extracted from numerical relativity simulations this method also gives us a way of estimating the time shift between the waveform and dynamics data, thus giving us a way to specify the spins at the same point in the waveform. This is useful both for performing a direct comparison between a numerical waveform and a detected signal and for developing a tuned model of precessing systems based on numerical waveforms. It is too computationally expensive to perform the number of numerical simulations required to densely sample the parameter space of precessing binaries. We therefore produced a phenomenological model of the signal from precessing binaries. This model is based on the idea that it is possible to ``twist up'' a non-precessing waveform in order to get a precessing waveform. The model presented here focusses on modelling the precession effects rather than the non-precessing waveform. We used a model from post-Newtonian theory for the precession effects during inspiral and produced a phenomenological model for the effects during merger and ringdown. This phenomenological model has been tuned to the catalogue of numerical simulations described above

A SYSTEMATIC REVIEW INVESTIGATING THE EFFECTS OF FAMILY INVOLVEMENT IN THE CARE OF THE ADOLESCENT DIABETIC

Background This study investigates the effects of family involvement in the care of the adolescent diabetic. Diabetes mellitus affects people and their families worldwide. Managing diabetes requires a daily execution of complex and demanding health behaviours, which becomes more complicated when coupled with the critical growth period of adolescence. Diabetic adolescents are a vulnerable group of individuals that commonly show poor glycaemic control. It is therefore important to understand how adolescents can be effectively supported in attaining good glycaemic control before they reach adulthood. Methods A systematic review was undertaken to review interventions that encourage family involvement in the care of the diabetic adolescent, and determine whether family involvement was a factor in improving glycaemic control. Electronic databases were searched using search terms determined using PICOS (population, intervention, comparison, outcomes, and study design), and additional studies were identified using reference lists from selected studies. Studies were put through a systematic selection process using inclusion and exclusion criteria before data extraction. Finally, data was extracted and critically analysed using a quality assessment tool. Results The systematic process identified eight randomised controlled trials that examined family involvement in the care of the diabetic adolescent, these were then analysed to identify themes and discussed. The themes identified were; glycaemic control, treatment adherence, teamwork/ family involvement, and diabetes related family conflict. The review demonstrated that increased family involvement in the care of the diabetic adolescent improves glycaemic control. Family involvement also improved treatment adherence, however did show links to increased diabetes-related family conflict. Conclusion The review states that sustained parental involvement in diabetes care (from childhood age 0-10 through adolescence age 10-19) should be encouraged because it does improve glycaemic control. Families can be encouraged to remain involved in the care of their children’s diabetes through to adolescence during clinic visits, which would not call for additional resources