The Quantized O(1,2)/O(2)×Z2O(1,2)/O(2)\times Z_2 Sigma Model Has No Continuum Limit in Four Dimensions. I. Theoretical Framework

The nonlinear sigma model for which the field takes its values in the coset space $O(1,2)/O(2)\times Z_2$ is similar to quantum gravity in being perturbatively nonrenormalizable and having a noncompact curved configuration space. It is therefore a good model for testing nonperturbative methods that may be useful in quantum gravity, especially methods based on lattice field theory. In this paper we develop the theoretical framework necessary for recognizing and studying a consistent nonperturbative quantum field theory of the $O(1,2)/O(2)\times Z_2$ model. We describe the action, the geometry of the configuration space, the conserved Noether currents, and the current algebra, and we construct a version of the Ward-Slavnov identity that makes it easy to switch from a given field to a nonlinearly related one. Renormalization of the model is defined via the effective action and via current algebra. The two definitions are shown to be equivalent. In a companion paper we develop a lattice formulation of the theory that is particularly well suited to the sigma model, and we report the results of Monte Carlo simulations of this lattice model. These simulations indicate that as the lattice cutoff is removed the theory becomes that of a pair of massless free fields. Because the geometry and symmetries of these fields differ from those of the original model we conclude that a continuum limit of the $O(1,2)/O(2)\times Z_2$ model which preserves these properties does not exist.Comment: 25 pages, no figure

The Quantized O(1,2)/O(2)×Z2O(1,2)/O(2)\times Z_2 Sigma Model Has No Continuum Limit in Four Dimensions. II. Lattice Simulation

A lattice formulation of the $O(1,2)/O(2)\times Z_2$ sigma model is developed, based on the continuum theory presented in the preceding paper. Special attention is given to choosing a lattice action (the ``geodesic'' action) that is appropriate for fields having noncompact curved configuration spaces. A consistent continuum limit of the model exists only if the renormalized scale constant $\beta_R$ vanishes for some value of the bare scale constant~$\beta$. The geodesic action has a special form that allows direct access to the small-$\beta$ limit. In this limit half of the degrees of freedom can be integrated out exactly. The remaining degrees of freedom are those of a compact model having a $\beta$-independent action which is noteworthy in being unbounded from below yet yielding integrable averages. Both the exact action and the $\beta$-independent action are used to obtain $\beta_R$ from Monte Carlo computations of field-field averages (2-point functions) and current-current averages. Many consistency cross-checks are performed. It is found that there is no value of $\beta$ for which $\beta_R$ vanishes. This means that as the lattice cutoff is removed the theory becomes that of a pair of massless free fields. Because these fields have neither the geometry nor the symmetries of the original model we conclude that the $O(1,2)/O(2)\times Z_2$ model has no continuum limit.Comment: 32 pages, 7 postscript figures, UTREL 92-0

The triviality and non-triviality of Lambda-Phi-4 model in different spacetime dimensions

Our research is an attempt to resolve the triviality status of the Lambda-PHI-4 model in 4-dimensions. The dynamics of the real valued scalar field PHI of the Lambda-PHI-4 model in d-dimensional Euclidean space is described by the action SE[PHI]=Integration(d^(d)x(1/2(deluPHI)^2+1/2m^2PHI^2+1/4!LambdaPHI^4) where m^2 and lambda are the bare mass and bare coupling constant respectively. Because of the close resemblance between this Lambda-PHI-4 model and the Higgs model,the triviality status of this model, that is, whether the field PHI self-interact or behaves like a free field has been of much interest. It is known that the Lambda-PHI-4 model is trivial in dimensions more than 4 and non-trivial in dimensions less than 4.However,in 4-dimensions, the triviality status of this model is not known decisively [1].RP1/06FS

Domain-specificity of self-concept and parent expectation influences on short-term and long-term learning of physics

Background: Students' academic self-concepts are known to be domain specific. Researchers have also identified two related components of self-concept:cognitive (how competent students feel about a subject domain) and affective (their interest in the subject). This paper examines whether both components are domain specific. Research has also shown that parents tend to influence children's academic behaviours and choices, but it is unclear whether parent influences would also be domain specific. Aim: This paper examined whether both the cognitive and affective components of self-concept in learning were domain specific with regard to learning physics and whether students' perceived parent support in learning physics would have short-term and long-term influences. Sample: A sample of secondary 1 students (7th graders) in Singapore responded to 29 items in a survey about their selfconcepts in learning physics (competence and interest), self-concepts in English (competence and interest), perceived parent expectations in physics, engagement in learning physics (a short-term outcome), and aspiration to learn physics in future (a longterm outcome). Method: Structural equation modelling was conducted to establish the 7 factors. Path analysis examined the relations of physics self-concepts to engagement (a short-term outcome) and aspiration (a long-term outcome). The paths from parent expectations were also examined. Result: The cognitive and affective components of self-concept were highly correlated, but only within respective domains. Physics self-concepts were uncorrelated with English self-concepts. The path from competence in physics to engagement was statistically significant, but not the path to aspiration. Paths from interest in physics to both outcomes were positive. Competence in English did not have positive relations with outcomes in physics, but interest in English had a positive relation with engagement in physics. Parent expectations had positive influences on both engagement and aspiration. Conclusion: The results provided partial support for the domain specificity of both the cognitive and affective components of self-concept. Parental influences tended to be strong even when the impacts of self-concepts are controlled

International Nosocomial Infection Control Consortium report, data summary of 50 countries for 2010-2015: Device-associated module

•We report INICC device-associated module data of 50 countries from 2010-2015.•We collected prospective data from 861,284 patients in 703 ICUs for 3,506,562 days.•DA-HAI rates and bacterial resistance were higher in the INICC ICUs than in CDC-NHSN's.•Device utilization ratio in the INICC ICUs was similar to CDC-NHSN's. Background: We report the results of International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2010-December 2015 in 703 intensive care units (ICUs) in Latin America, Europe, Eastern Mediterranean, Southeast Asia, and Western Pacific. Methods: During the 6-year study period, using Centers for Disease Control and Prevention National Healthcare Safety Network (CDC-NHSN) definitions for device-associated health care-associated infection (DA-HAI), we collected prospective data from 861,284 patients hospitalized in INICC hospital ICUs for an aggregate of 3,506,562 days. Results: Although device use in INICC ICUs was similar to that reported from CDC-NHSN ICUs, DA-HAI rates were higher in the INICC ICUs: in the INICC medical-surgical ICUs, the pooled rate of central line-associated bloodstream infection, 4.1 per 1,000 central line-days, was nearly 5-fold higher than the 0.8 per 1,000 central line-days reported from comparable US ICUs, the overall rate of ventilator-associated pneumonia was also higher, 13.1 versus 0.9 per 1,000 ventilator-days, as was the rate of catheter-associated urinary tract infection, 5.07 versus 1.7 per 1,000 catheter-days. From blood cultures samples, frequencies of resistance of Pseudomonas isolates to amikacin (29.87% vs 10%) and to imipenem (44.3% vs 26.1%), and of Klebsiella pneumoniae isolates to ceftazidime (73.2% vs 28.8%) and to imipenem (43.27% vs 12.8%) were also higher in the INICC ICUs compared with CDC-NHSN ICUs. Conclusions: Although DA-HAIs in INICC ICU patients continue to be higher than the rates reported in CDC-NSHN ICUs representing the developed world, we have observed a significant trend toward the reduction of DA-HAI rates in INICC ICUs as shown in each international report. It is INICC's main goal to continue facilitating education, training, and basic and cost-effective tools and resources, such as standardized forms and an online platform, to tackle this problem effectively and systematically