On the stability of Einstein static universe at background level in massive bigravity

We study the static cosmological solutions and their stability at background level in the framework of massive bigravity theory with Friedmann-Robertson-Walker (FRW) metrics. By the modification proposed in the cosmological equations subject to a perfect fluid we obtain new solutions interpreted as the Einstein static universe. It turns out that the non-vanishing size of initial scale factor of Einstein static universe depends on the non-vanishing three-dimensional spatial curvature of FRW metrics and also the graviton's mass. By dynamical system approach and numerical analysis, we find that the extracted solutions for closed and open universes can be stable for some viable ranges of equation of state parameter, viable values of fraction of two scale factors, and viable values of graviton's mass obeying the hierarchy $m << M_Pl$ which is more cosmologically motivated.Comment: 14 pages, 8 figures, 5 tables, major revisio

Classical and quantum cosmology of minimal massive bigravity

In a Friedmann-Robertson-Walker (FRW) space-time background we study the classical cosmological models in the context of recently proposed theory of nonlinear minimal massive bigravity. We show that in the presence of perfect fluid the classical field equations acquire contribution from the massive graviton as a cosmological term which is positive or negative depending on the dynamical competition between two scale factors of bigravity metrics. We obtain the classical field equations for flat and open universes in the ordinary and Schutz representation of perfect fluid. Focusing on the Schutz representation for flat universe, we find classical solutions exhibiting singularities at early universe with vacuum equation of state. Then, in the Schutz representation, we study the quantum cosmology for flat universe and derive the Schrodinger-Wheeler-DeWitt equation. We find its exact and wave packet solutions and discuss on their properties to show that the initial singularity in the classical solutions can be avoided by quantum cosmology. Similar to the study of Hartle-Hawking no-boundary proposal in the quantum cosmology of de Rham, Gabadadze and Tolley (dRGT) massive gravity, it turns out that the mass of graviton predicted by quantum cosmology of the minimal massive bigravity is large at early universe. This is in agreement with the fact that at early universe the cosmological constant should be large.Comment: 13 pages, 6 figures, published online, Phys. Lett. B (2016

Quality of life after cesarean and vaginal delivery

Objective: Cesarean rates in recent decades have been increasing and a number of studies have shown that cesarean increases maternal morbidities. The aim of this study is to compare the quality of life after cesarean and vaginal delivery. Methods: This prospective study was carried out on 356 pregnant women visiting urban health centers in Shahroud City, Northeast Iran, in 2011. The subjects completed the quality of life questionnaire in the third trimester of pregnancy and at 8 weeks postpartum. Results: In primiparas, the mean global QOL scores for the cesarean and vaginal delivery groups were 67.65±12.7 and 72.12±11.8, respectively. Also, the scores for the physical, psychological and social domains of QOL as well as the global score of QOL were higher in the vaginal delivery group than the cesarean group (p<0.05). In the case of primiparas, multiple regression analysis revealed that after adjusting for education, desirability of pregnancy and the General Health Questionnaire score, the delivery type remained as a predictor of the scores for the physical (R2=1.7%; B=-3.826; p=0.031; CI [-7.301, -.350]) and social (R2=2.5%; B=-5.708; p=0.017; CI [-10.392, -1.023]) domains of QOL and the global QOL score (R2=2.6%; B=-4.065; p=0.006; CI [-6.964, -1.164]). While multiparas, there was no relationship between QOL and type of delivery. Conclusion: In this sample of low-risk women, cesarean negatively affected the QOL of primiparas. More studies with larger sample sizes should be conducted to examine the effects of cesarean on QOL in both primiparas and multiparas within a shorter period after delivery. © OMSB, 2013

On the Order of the Schur Multiplier of a Pair of Finite p-Groups

In 1998, G. Ellis defined the Schur multiplier of a pair $(G,N)$ of groups and mentioned that this notion is a useful tool for studying pairs of groups. In this paper, we characterize the structure of a pair of finite $p$-groups $(G,N)$ in terms of the order of the Schur multiplier of $(G,N)$ under some conditions.Comment: 11 pages, to appear in Journal of Advanced Research in Pure Mathematic

Validation of the World Health Organization-5 well-being index; assessment of maternal well-being and its associated factors

Objective: The aim of this study was to validate the World Health Organization-5 Well-Being Index (WHO-5) in a sample of pregnant Iranian women, to explore the changes in maternal well-being from pregnancy to postpartum, and to determine the factors associated with maternal well-being. Materials and Methods: This study included 341 pregnant women that presented to healthcare centers affiliated with Shahroud University of Medical Sciences, Iran, in 2011. The participants completed the General Health Questionnaire (GHQ-28) and Farsi version of WHO-5 during the third trimester of pregnancy and at 2 months postpartum. Results: Cronbach's alpha coefficient for WHO-5 items was 0.85. The correlation coefficient between WHO-5 and GHQ-28 was -0.64 (P < 0.001). Exploratory factor analysis yielded 1 factor with an eigen value equal to 3.15, which explained 63.1% of the total variance. Confirmatory factor analysis confirmed the 1-factor structure. The area under ROC curve was 0.82. A WHO-5 cut-off score of <50 exhibited optimal sensitivity (0.84) and specificity (0.59) for identifying psychological symptoms (GHQ-28 score ≥24). There was a significant difference between third trimester (58.4 ± 22) and postpartum (64.1 ± 22.3) mean WHO-5 scores (P < 0.001). Maternal level of education (OR = 1.130; 95% CI: 1.307, 1.232) was the only predictor of maternal well-being during third trimester. Breastfeeding difficulty (OR = 0.923; 95% CI: 0.882, 0.965) and maternal well-being scores during third trimester (OR = 1.038; 95% CI: 1.019, 1.058) were predictors of maternal well-being during the postpartum period. Conclusions: The Farsi version of WHO-5 was observed to be a reliable and valid instrument for screening psychological symptoms in pregnant Iranian women. The present findings show that maternal well-being improved following childbirth