A compendium of chameleon constraints

The chameleon model is a scalar field theory with a screening mechanism that explains how a cosmologically relevant light scalar can avoid the constraints of intra-solar-system searches for fifth-forces. The chameleon is a popular dark energy candidate and also arises in f(R) theories of gravity. Whilst the chameleon is designed to avoid historical searches for fifth-forces it is not unobservable and much effort has gone into identifying the best observables and experiments to detect it. These results are not always presented for the same models or in the same language, a particular problem when comparing astrophysical and laboratory searches making it difficult to understand what regions of parameter space remain. Here we present combined constraints on the chameleon model from astrophysical and laboratory searches for the first time and identify the remaining windows of parameter space. We discuss the implications for cosmological chameleon searches and future small-scale probes

The XMM cluster survey: Testing chameleon gravity using the profiles of clusters

The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the clusters weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, z = 0.02). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (0.1 R0| R0| on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey

The XMM Cluster Survey: testing chameleon gravity using the profiles of clusters

The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the clusters weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, z = 0.02). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (0.1 < z < 1.2), including 12 new to the literature, using X-ray data from the XMM Cluster Survey and weak lensing data from the Canada-France-Hawaii-Telescope Lensing Survey. Using a multiparameter Markov chain Monte Carlo analysis, we constrain the two chameleon gravity parameters (beta and phi∞). Our fits are consistent with general relativity, not requiring a fifth force. In the special case of f(R) gravity (where beta = &surd;{1/6}), we set an upper limit on the background field amplitude today of |fR0| < 6 × 10-5 (95 per cent CL). This is one of the strongest constraints to date on |fR0| on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey

Tests of chameleon gravity

Theories of modified gravity, where light scalars with non-trivial self-interactions and non-minimal couplings to matter—chameleon and symmetron theories—dynamically suppress deviations from general relativity in the solar system. On other scales, the environmental nature of the screening means that such scalars may be relevant. The highly-nonlinear nature of screening mechanisms means that they evade classical fifth-force searches, and there has been an intense effort towards designing new and novel tests to probe them, both in the laboratory and using astrophysical objects, and by reinterpreting existing datasets. The results of these searches are often presented using different parametrizations, which can make it difficult to compare constraints coming from different probes. The purpose of this review is to summarize the present state-of-the-art searches for screened scalars coupled to matter, and to translate the current bounds into a single parametrization to survey the state of the models. Presently, commonly studied chameleon models are well-constrained but less commonly studied models have large regions of parameter space that are still viable. Symmetron models are constrained well by astrophysical and laboratory tests, but there is a desert separating the two scales where the model is unconstrained. The coupling of chameleons to photons is tightly constrained but the symmetron coupling has yet to be explored. We also summarize the current bounds on f(R) models that exhibit the chameleon mechanism (Hu and Sawicki models). The simplest of these are well constrained by astrophysical probes, but there are currently few reported bounds for theories with higher powers of R. The review ends by discussing the future prospects for constraining screened modified gravity models further using upcoming and planned experiments

Simulation tests of galaxy cluster constraints on chameleon gravity

We use two new hydrodynamical simulations of $\Lambda$CDM and $f(R)$ gravity to test the methodology used by Wilcox et al. 2015 (W15) in constraining the effects of a fifth force on the profiles of clusters of galaxies. We construct realistic simulated stacked weak lensing and X-ray surface brightness cluster profiles from these cosmological simulations, and then use these data projected along various lines-of-sight to test the spherical symmetry of our stacking procedure. We also test the applicability of the NFW profile to model weak lensing profiles of clusters in $f(R)$ gravity. Finally, we test the validity of the analytical model developed in W15 against the simulated profiles. Overall, we find our methodology is robust and broadly agrees with these simulated data. We also apply our full Markov Chain Monte Carlo (MCMC) analysis from W15 to our simulated X-ray and lensing profiles, providing consistent constraints on the modified gravity parameters as obtained from the real cluster data, e.g. for our $\Lambda$CDM simulation we obtain $|f_{\rm{R}0}| < 8.3 \times 10^{-5}$ (95% CL), which is in good agreement with the W15 measurement of $|f_{\rm{R}0}| < 6 \times 10^{-5}$. Overall, these tests confirm the power of our methodology which can now be applied to larger cluster samples available with the next generation surveys.Comment: 12 pages, 15 figure

“Nivel de satisfacción de gestantes atendidas según tipo de parto en la clínica good hope, febrero – abril 2016”

Objective: To determine the level of satisfaction of the pregnant women attended at the Good Hope Clinic in the established period, to determine satisfaction with dimensions of quality and according to type of delivery. Design: Cross Section Analytical Study. Institution: Good Hope Clinic. Participants: Puerperal attended. Methods: The SERVPERF-GP Survey was adapted and validated by our research group, informed consent was obtained and applied to 345 women treated at the Good Hope Clinic from February to April 2016. Main outcome measure: Level of satisfaction of users. Results: 62.6% are between 29 and 38 years old, 83.2% have a higher education degree, 59.4% are married, 52.5% have 1 child. 78.3% had a cesarean delivery. Satisfaction was observed in 98.3% (CI 95%). The value of the highest mean was in the dimension: Tangible Aspects m:5.71 +/- 0.45. The level of satisfaction is higher in vaginal delivery in relation to cesarean section (p <0.00). No significant differences were found in the comparison by age, parity, marital status or degree of education. Conclusions: The level of overall satisfaction found was high. The dimension that reached the greatest value was that of "tangible aspects". There is a significant difference in the level of satisfaction of women according to the type of delivery, in favor of vaginal delivery compared to cesarean delivery.Objetivos: Determinar el nivel de satisfacción de las gestantes atendidas en la Clínica Good Hope en el período establecido, determinar la satisfacción por dimensiones de la calidad y según tipo de parto. Diseño: Estudio Analítico de Corte Transversal. Institución: Clínica Good Hope. Participantes: Puérperas. Métodos: Se empleó la Encuesta SERVPERF-GP adaptada y validada por nuestro grupo de investigación, se obtuvo el consentimiento informado y se aplicó a 345 mujeres atendidas en la Clínica Good Hope en el periodo febrero a abril de 2016. Principal medida de resultado: Nivel de satisfacción de usuarias. Resultados: El 62.6% tiene entre 29 y 38 años, 83.2% tiene grado de instrucción superior, 59.4% son casadas, 52.5% tiene 1 hijo. El 78.3% tuvo parto por cesárea. Se observó satisfacción en el 98.3% (IC 95%). El valor media más elevado estuvo en la dimensión: Aspectos Tangibles m: 5.71+/-0.45. El nivel de satisfacción es mayor en parto vaginal en relación a cesárea (p<0.00). No se encontraron diferencias significativas en la comparación por edad, paridad, estado civil ni grado de instrucción. Conclusión: El nivel de satisfacción global hallado fue elevado. La dimensión que alcanzo mayor valor fue la de “aspectos tangibles”. Existe diferencia significativa en el nivel de satisfacción de las mujeres según tipo de parto, a favor del parto vaginal en comparación con la cesárea.Trabado de investigacio

Nivel de satisfacción de gestantes atendidas según tipo de parto en la clínica Good Hope, febrero – abril 2016

Objective: To determine the level of satisfaction of the pregnant women attended at the Good Hope Clinic in the established period, to determine satisfaction with dimensions of quality and according to type of delivery. Design: Cross Section Analytical Study. Institution: Good Hope Clinic. Participants: Puerperal attended. Methods: The SERVPERF-GP Survey was adapted and validated by our research group, informed consent was obtained and applied to 345 women treated at the Good Hope Clinic from February to April 2016. Main outcome measure: Level of satisfaction of users. Results: 62.6% are between 29 and 38 years old, 83.2% have a higher education degree, 59.4% are married, 52.5% have 1 child. 78.3% had a cesarean delivery. Satisfaction was observed in 98.3% (CI 95%). The value of the highest mean was in the dimension: Tangible Aspects m:5.71 +/- 0.45. The level of satisfaction is higher in vaginal delivery in relation to cesarean section (p <0.00). No significant differences were found in the comparison by age, parity, marital status or degree of education. Conclusions: The level of overall satisfaction found was high. The dimension that reached the greatest value was that of "tangible aspects". There is a significant difference in the level of satisfaction of women according to the type of delivery, in favor of vaginal delivery compared to cesarean delivery.Objetivos: Determinar el nivel de satisfacción de las gestantes atendidas en la Clínica Good Hope en el período establecido, determinar la satisfacción por dimensiones de la calidad y según tipo de parto. Diseño: Estudio Analítico de Corte Transversal. Institución: Clínica Good Hope. Participantes: Puérperas. Métodos: Se empleó la Encuesta SERVPERF-GP adaptada y validada por nuestro grupo de investigación, se obtuvo el consentimiento informado y se aplicó a 345 mujeres atendidas en la Clínica Good Hope en el periodo febrero a abril de 2016. Principal medida de resultado: Nivel de satisfacción de usuarias. Resultados: El 62.6% tiene entre 29 y 38 años, 83.2% tiene grado de instrucción superior, 59.4% son casadas, 52.5% tiene 1 hijo. El 78.3% tuvo parto por cesárea. Se observó satisfacción en el 98.3% (IC 95%). El valor media más elevado estuvo en la dimensión: Aspectos Tangibles m: 5.71+/-0.45. El nivel de satisfacción es mayor en parto vaginal en relación a cesárea (p<0.00). No se encontraron diferencias significativas en la comparación por edad, paridad, estado civil ni grado de instrucción. Conclusión: El nivel de satisfacción global hallado fue elevado. La dimensión que alcanzo mayor valor fue la de “aspectos tangibles”. Existe diferencia significativa en el nivel de satisfacción de las mujeres según tipo de parto, a favor del parto vaginal en comparación con la cesárea.Trabado de investigacio