An example of Berglund-H\"ubsch mirror symmetry for a Calabi-Yau complete intersection

We study an example of complete intersection Calabi-Yau threefold due to Libgober and Teitelbaum arXiv:alg-geom/9301001, and verify mirror symmetry at a cohomological level. Direct computations allow us to propose an analogue to the Berglund-H\"ubsch mirror symmetry setup for this example arXiv:hep-th/9201014. We then follow the approach of Krawitz to propose an explicit mirror map arXiv:0906.0796.Comment: 18 pages, 4 table

Estimating the galaxy power spectrum of the VIPERS galaxy distribution.

The power spectrum is a statistic that describes the clustering of matter in Fourier space. The shape and amplitude of the power are directly predicted by theory and direct measurements of the power can constrain cosmological parameters. The large size of recent surveys has opened new windows in the observation of secondary features of the galaxy power spectrum such as the Baryonic Acoustic Oscillations (BAO), which used as standard ruler can infer dark energy properties, and Redshift-Space Distortions (RSD), which thanks to the anisotropic observed clustering in redshift space can discriminate between different theories of gravity. In this thesis, we apply the power spectrum statistic to the VIMOS Public Extragalactic Redshift Survey (VIPERS) distribution of galaxies in order to study the underlying clustering of matter. VIPERS is an ongoing spectroscopic survey, composed of two fields, W1 and W4, with the aim of mapping the spatial distribution of galaxies within a large volume of the z 3c 1 Universe. The main properties of VIPERS are the high redshift range surveyed 0.4 < z < 1.2 and the high sampling rate at those redshifts. Its main goal is the measurement of the anisotropy of the galaxy clustering in redshift space in order to constrain the growth rate of structure at a mean redshift hzi 3c 0.8, never reached by other surveys. Even the measure of the galaxy power spectrum at these redshifts is something new. Our goal is to estimate the clustering of matter in Fourier space constraining the cosmological quantities that mainly affect the power spectrum shape such as the matter density and the baryonic fraction. The approach used to estimate the galaxy power spectrum is quite classical and has been used in past surveys such as the Two Degree Field Galaxy Redshift Survey (2dFGRS). We describe the power spectrum estimator using a novel simulation approach called \u201c\u393\u201d-simulation, including the main properties of a real survey such as the cone-like geometry and the density gradient function of the redshift. The main factor that alters our power spectrum measurement is the window function, due to the limited size of the sample, which is not negligible even for a box geometry. We show a method to correctly take into account the window function effects including it with a three dimensional convolution with the input model of the simulation. To analyse the potential of the VIPERS sample for extracting cosmological information, we use a set of VIPERS mock catalogues drawn from the MultiDark simulation. We analyse all the selection function effects of the survey, such as the sampling strategy and the decreasing mean density, in our estimation and study their effect on the recovered power spectrum. The VIPERS window function is problematic due to the small angular coverage, strongly suppressing the clustering in Fourier space at large scales and completely damping the BAO signal. We measure the window function of VIPERS which will be used to perform a three dimensional convolution with the theoretical model generated from the tested cosmology. RSD also determine the observed clustering and, in the simplest case, their impact could be divided in two regimes. Small scale effects due to the high non-linear velocity of galaxies inside virialised structures are corrected with a simple velocity dispersion model, an empirical prediction of the behaviour of the clustering in redshift space. Large scale effects due to the linear in-fall of galaxies in high density peaks, which increase the observed clustering of matter, are included with the Kaiser term dependent on the linear growth rate of matter. We include these two terms before applying the 3D convolution of the model with the window function. Some tests are performed on VIPERS mock catalogues to recover the known cosmological information of the simulation with a chi-square technique and, in all cases, we were able to extract the input cosmology with lower systematics errors than statistical ones. Finally we apply this approach to the data dividing the full survey into four subsamples, two redshift bins, 0.6 < z1 < 0.9 and 0.9 < z2 < 1.1, for each field. Despite the different window functions in each subsample due to small differences in volume and in geometry, the four measurements are consistent with each other. This is due to the fact that, at large scales, statistical fluctuations related to cosmic variance are much bigger with respect to small differences in the window. Even the overall amplitude is similar between the two redshift bins because the lower amplitude expected for the higher redshift power spectrum (because structures were less compact in the past) is compensated by the higher bias factor. We compare the measured power spectrum from data with some theoretical models in order to extract the baryonic fraction and the amount of matter density in the Universe. The probability contours display evidence of a well-known degeneracy previously observed in other surveys (such as 2dFGRS) between the two recovered parameters in the determination of the overall shape of the matter power spectrum. Increasing the matter density of the Universe in fact shifts the power spectrum toward higher modes enhancing the clustering at the scales sampled by VIPERS. In this case to compensate the increase of power, the good fit is given by models with high baryonic fraction necessary to suppress the power at those scales. Vice-versa a low-M Universe does not need a high baryonic fraction. This degeneracy is broken combining the two redshift bins with a joint likelihood. Finally, we provide an estimation of the matter density fixing all the other cosmological parameters to the best known values. We evaluate the matter density to be M = 0.272+0.027 120.031 in perfect agreement with Planck (once we rescale the Hubble factor from the Hubble Space Telescope used for the estimation of M to be consistent with the Planck one) and with the matter density estimated from the VIPERS Public Data Release-1 measurements of the clustering ratio

Estimating the galaxy power spectrum of the VIPERS galaxy distribution.

The power spectrum is a statistic that describes the clustering of matter in Fourier space. The shape and amplitude of the power are directly predicted by theory and direct measurements of the power can constrain cosmological parameters. The large size of recent surveys has opened new windows in the observation of secondary features of the galaxy power spectrum such as the Baryonic Acoustic Oscillations (BAO), which used as standard ruler can infer dark energy properties, and Redshift-Space Distortions (RSD), which thanks to the anisotropic observed clustering in redshift space can discriminate between different theories of gravity. In this thesis, we apply the power spectrum statistic to the VIMOS Public Extragalactic Redshift Survey (VIPERS) distribution of galaxies in order to study the underlying clustering of matter. VIPERS is an ongoing spectroscopic survey, composed of two fields, W1 and W4, with the aim of mapping the spatial distribution of galaxies within a large volume of the z ∼ 1 Universe. The main properties of VIPERS are the high redshift range surveyed 0.4 < z < 1.2 and the high sampling rate at those redshifts. Its main goal is the measurement of the anisotropy of the galaxy clustering in redshift space in order to constrain the growth rate of structure at a mean redshift hzi ∼ 0.8, never reached by other surveys. Even the measure of the galaxy power spectrum at these redshifts is something new. Our goal is to estimate the clustering of matter in Fourier space constraining the cosmological quantities that mainly affect the power spectrum shape such as the matter density and the baryonic fraction. The approach used to estimate the galaxy power spectrum is quite classical and has been used in past surveys such as the Two Degree Field Galaxy Redshift Survey (2dFGRS). We describe the power spectrum estimator using a novel simulation approach called “Γ”-simulation, including the main properties of a real survey such as the cone-like geometry and the density gradient function of the redshift. The main factor that alters our power spectrum measurement is the window function, due to the limited size of the sample, which is not negligible even for a box geometry. We show a method to correctly take into account the window function effects including it with a three dimensional convolution with the input model of the simulation. To analyse the potential of the VIPERS sample for extracting cosmological information, we use a set of VIPERS mock catalogues drawn from the MultiDark simulation. We analyse all the selection function effects of the survey, such as the sampling strategy and the decreasing mean density, in our estimation and study their effect on the recovered power spectrum. The VIPERS window function is problematic due to the small angular coverage, strongly suppressing the clustering in Fourier space at large scales and completely damping the BAO signal. We measure the window function of VIPERS which will be used to perform a three dimensional convolution with the theoretical model generated from the tested cosmology. RSD also determine the observed clustering and, in the simplest case, their impact could be divided in two regimes. Small scale effects due to the high non-linear velocity of galaxies inside virialised structures are corrected with a simple velocity dispersion model, an empirical prediction of the behaviour of the clustering in redshift space. Large scale effects due to the linear in-fall of galaxies in high density peaks, which increase the observed clustering of matter, are included with the Kaiser term dependent on the linear growth rate of matter. We include these two terms before applying the 3D convolution of the model with the window function. Some tests are performed on VIPERS mock catalogues to recover the known cosmological information of the simulation with a chi-square technique and, in all cases, we were able to extract the input cosmology with lower systematics errors than statistical ones. Finally we apply this approach to the data dividing the full survey into four subsamples, two redshift bins, 0.6 < z1 < 0.9 and 0.9 < z2 < 1.1, for each field. Despite the different window functions in each subsample due to small differences in volume and in geometry, the four measurements are consistent with each other. This is due to the fact that, at large scales, statistical fluctuations related to cosmic variance are much bigger with respect to small differences in the window. Even the overall amplitude is similar between the two redshift bins because the lower amplitude expected for the higher redshift power spectrum (because structures were less compact in the past) is compensated by the higher bias factor. We compare the measured power spectrum from data with some theoretical models in order to extract the baryonic fraction and the amount of matter density in the Universe. The probability contours display evidence of a well-known degeneracy previously observed in other surveys (such as 2dFGRS) between the two recovered parameters in the determination of the overall shape of the matter power spectrum. Increasing the matter density of the Universe in fact shifts the power spectrum toward higher modes enhancing the clustering at the scales sampled by VIPERS. In this case to compensate the increase of power, the good fit is given by models with high baryonic fraction necessary to suppress the power at those scales. Vice-versa a low-M Universe does not need a high baryonic fraction. This degeneracy is broken combining the two redshift bins with a joint likelihood. Finally, we provide an estimation of the matter density fixing all the other cosmological parameters to the best known values. We evaluate the matter density to be M = 0.272+0.027 −0.031 in perfect agreement with Planck (once we rescale the Hubble factor from the Hubble Space Telescope used for the estimation of M to be consistent with the Planck one) and with the matter density estimated from the VIPERS Public Data Release-1 measurements of the clustering ratio

The population of ULXs in the spiral galaxy NGC 2276

We present results for X-ray point sources in the Sc galaxy NGC 2276, obtained by analyzing Chandra data. The galaxy is known to be very active in many wavelengths, possibly due to gravitational interaction with the central elliptical of the group, NGC 2300. However, previous XMM-Newton observations resulted in the detection of only one bright ULX and extended hot gas emission. We present here the X-ray population in NGC 2276 which comprises 17 sources. We found that 6 of them are new ULX sources in this spiral galaxy resolved for the first time by Chandra. We constructed the Luminosity Function that can be interpreted as mainly due of High Mass X-ray binaries, and estimate the Star Formation rate (SFR) to be SFR ~ 5-10 M_sun/yr.Comment: 4 pages, 4 figures, Proceedings of the meeting 'Ultra-Luminous X-ray sources and Middle Weight Black Holes', ESAC, Madrid, Spain, May 201

Queen Christina’s heroic virtue and its religious implications

Heroic virtue is a recurrent theme in poems and panegyrics written for Queen Christina of Sweden, both before and after her abdication.This article focus on the use of heroic virtue in some poems and academic discourses dedicated to Christina, both before and after her conversion to Catholicism, taking a particular interest in its religious implications.The claim for heroicity stands as a political argument during the queen’s time in Sweden and as a programmatic position for her academy in Rome, Accademia Reale, both in its philosophical and poetical activity

An example of Berglund-Hübsch mirror symmetry for a Calabi-Yau complete intersection

We study an example of complete intersection Calabi-Yau threefold due to Libgober and Teitelbaum, and verify mirror symmetry at a cohomological level. Direct computations allow us to propose an analogue to the Berglund-H\"ubsch mirror symmetry setup for this example . We then follow the approach of Krawitz to propose an explicit mirror map

SPH simulation of periodic wave breaking in the surf zone. A detailed fluid dynamic validation

The estimation of wave breaking and run-up on sloped beaches is a relevant issue in different coastal engineering applications. The present study stresses on the capabilities of a Smoothed Particle Hydrodynamics (SPH) solver, with optimal numerical and physical parameters, to accurately simulate the complex flow field in the surf zone and run-up region. Numerical results are compared with high quality experimental measurements of the local flow field in terms of instantaneous and phase averaged values. The selected test case regards the propagation and breaking of regular non-linear waves on a smooth impermeable plane slope. The comparison is based on a complete set of 128 consecutive non-linear regular waves. The level of accuracy of the numerical results and the ability of the model to reproduce the periodic flow in the surf-zone is provided. Current limitations and uncertainty sources are identified and discussed to guide future developments

Forced and natural dynamics of a clamped flexible fiber in wall turbulence

We characterize the dynamical behavior of a clamped flexible fiber immersed in wall turbulence over a wide range of natural frequencies by means of direct numerical simulations. Only two flapping states are possible: one where the fiber oscillates at the characteristic frequency of the largest turbulent eddies and another where the natural structural response dominates. The former is obtained in the more flexible cases, while the latter in the more rigid ones. We observe here for the first time that in the turbulence dominated regime the fiber always sways at a frequency proportional to the largest scale of the flow, regardless of its structural parameters. The hindrance of the clamp to the wall prevents the synchronization of the fiber with turbulent eddies of comparable size.Comment: 6+4 pages, 6+3 figure