Theoretical tools for CMB physics

This review presents, in a self-consistent manner, those analytical tools that are relevant for the analysis of the physics of CMB anisotropies generated in different theoretical models of the early Universe. After introducing the physical foundations of the Sachs-Wolfe effect, the origin and evolution of the scalar, tensor and vector modes of the geometry is treated in both gauge-invariant and gauge-dependent descriptions. Some of the recent progresses in the theory of cosmological perturbations are scrutinized with particular attention to their implications for the adiabatic and isocurvature paradigms, whose description is reviewed both within conventional fluid approaches and within the the Einstein-Boltzmann treatment. Open problems and theoretical challenges for a unified theory of the early Universe are outlined in light of their implications for the generation of large-scale anisotropies in the CMB sky and in light of the generation of stochastic backgrounds of relic gravitons between few Hz and the GHz.Comment: 147 pages, 6 figures; minor corrected typo

Hippocampal volumes are important predictors for memory function in elderly women

<p>Abstract</p> <p>Background</p> <p>Normal aging involves a decline in cognitive function that has been shown to correlate with volumetric change in the hippocampus, and with genetic variability in the APOE-gene. In the present study we utilize 3D MR imaging, genetic analysis and assessment of verbal memory function to investigate relationships between these factors in a sample of 170 healthy volunteers (age range 46–77 years).</p> <p>Methods</p> <p>Brain morphometric analysis was performed with the automated segmentation work-flow implemented in FreeSurfer. Genetic analysis of the APOE genotype was determined with polymerase chain reaction (PCR) on DNA from whole-blood. All individuals were subjected to extensive neuropsychological testing, including the California Verbal Learning Test-II (CVLT). To obtain robust and easily interpretable relationships between explanatory variables and verbal memory function we applied the recent method of conditional inference trees in addition to scatterplot matrices and simple pairwise linear least-squares regression analysis.</p> <p>Results</p> <p>APOE genotype had no significant impact on the CVLT results (scores on long delay free recall, CVLT-LD) or the ICV-normalized hippocampal volumes. Hippocampal volumes were found to decrease with age and a right-larger-than-left hippocampal asymmetry was also found. These findings are in accordance with previous studies. CVLT-LD score was shown to correlate with hippocampal volume. Multivariate conditional inference analysis showed that gender and left hippocampal volume largely dominated predictive values for CVLT-LD scores in our sample. Left hippocampal volume dominated predictive values for females but not for males. APOE genotype did not alter the model significantly, and age was only partly influencing the results.</p> <p>Conclusion</p> <p>Gender and left hippocampal volumes are main predictors for verbal memory function in normal aging. APOE genotype did not affect the results in any part of our analysis.</p

Full tensorial characterization of PZN-12%PT single crystal by resonant ultrasound spectroscopy

International audienceAn experimental setup based on the electrical excitation of a piezoelectric sample is proposed for resonant ultrasound spectroscopy measurements. The detection of the mechanical vibrations is performed by means of a laser interferometer. At the same time, the free vibrations of piezoelectric parallelepipeds of tetragonal and hexagonal symmetries are modeled taking into account the effect of the sample metalization. The paper presents the full elastic, piezoelectric and dielectric tensors of two PMN-34.5%PT ceramic and PZN-12%PT single crystal cubes