The influence of twin boundaries on the Flux Line Lattice structure in YBaCuO: a study by Small Angle Neutron Scattering

The influence of Twin Boundaries (TB) on the Flux Line Lattice(FLL) structure was investigated by Small Angle Neutron Scattering (SANS). YBaCuO single crystals possessing different TB densities were studied. The SANS experiments show that the TB strongly modify the structure of the FLL. The flux lines meander as soon as the magnetic field makes an angle with the TB direction. According to the value of this angle but also to the ratio of the flux lines density over the TB density, one observes that the FLL exhibits two different unit cells in the plane perpendicular to the magnetic field. One is the classical hexagonal and anisotropic cell while the other is affected by an additional deformation induced by the TB. We discuss a possible relation between this deformation and the increase of the critical current usually observed in heavily twinned samples.Comment: accepted for publication in Phys Rev

The skewed weak lensing likelihood: why biases arise, despite data and theory being sound

We derive the essentials of the skewed weak lensing likelihood via a simple hierarchical forward model. Our likelihood passes four objective and cosmology-independent tests which a standard Gaussian likelihood fails. We demonstrate that sound weak lensing data are naturally biased low, since they are drawn from a skewed distribution. This occurs already in the framework of Lambda cold dark matter. Mathematically, the biases arise because noisy two-point functions follow skewed distributions. This form of bias is already known from cosmic microwave background analyses, where the low multipoles have asymmetric error bars. Weak lensing is more strongly affected by this asymmetry as galaxies form a discrete set of shear tracer particles, in contrast to a smooth shear field. We demonstrate that the biases can be up to 30 per cent of the standard deviation per data point, dependent on the properties of the weak lensing survey and the employed filter function. Our likelihood provides a versatile framework with which to address this bias in future weak lensing analyses

The decrease of the critical current of coated conductors when a perpendicular magnetic field is applied : a Josephson effect point of view

A large decrease is observed in the critical current density of YBCO coated conductors (CC) and related compounds when a strong perpendicular magnetic field is applied. While measurements are generally carried out at 77K only, here we present a magnetic technique permitting to determine the critical current per unit width of conductor (Icr/w) in a large temperature range. We report measurements carried out on various CCs that show that, in addition to the reduction in the critical temperature that can be attributed to the low value of the irreversibility field near Tc, the field application results in a large decrease of Icr/w at all temperatures. We ascribe this reduction to the Josephson behaviour of the twin boundaries included in the YBCO layer

On the road to percent accuracy III: non-linear reaction of the matter power spectrum to massive neutrinos

We analytically model the non-linear effects induced by massive neutrinos on the total matter power spectrum using the halo model reaction framework of Cataneo et al. In this approach, the halo model is used to determine the relative change to the matter power spectrum caused by new physics beyond the concordance cosmology. Using standard fitting functions for the halo abundance and the halo mass–concentration relation, the total matter power spectrum in the presence of massive neutrinos is predicted to per cent-level accuracy, out to k=10hMpc−1⁠. We find that refining the prescriptions for the halo properties using N-body simulations improves the recovered accuracy to better than 1 per cent. This paper serves as another demonstration for how the halo model reaction framework, in combination with a single suite of standard Λ cold dark matter (ΛCDM) simulations, can recover per cent-level accurate predictions for beyond ΛCDM matter power spectra, well into the non-linear regime

Accuracy requirements on intrinsic alignments for Stage-IV cosmic shear

In the context of cosmological weak lensing studies, intrinsic alignments (IAs) are one of the most In the context of cosmological weak lensing studies, intrinsic alignments (IAs) are one of the most complicated astrophysical systematic\rev{s} to model, given the poor understanding of the physical processes that cause them. A number of modelling frameworks for IAs have been proposed in the literature, both purely phenomenological or grounded on a perturbative treatment of symmetry-based arguments. However, the accuracy with which any of these approaches is able to describe the impact of IAs on cosmic shear data, particularly on the comparatively small scales ([Math Processing Error]) to which this observable is sensitive, is not clear. Here we quantify the level of disagreement between the true underlying intrinsic alignments and the theoretical model used to describe them that can be allowed in the context of cosmic shear analyses with future Stage-IV surveys. We consider various models describing this "IA residual’', covering both physics-based approaches, as well as completely agnostic prescriptions. The same qualitative results are recovered in all cases explored: for a Stage-IV cosmic shear survey, a mis-modelling of the IA contribution at the [Math Processing Error] level produces shifts of [Math Processing Error] on the final cosmological parameter constraints. Current and future IA models should therefore aim to achieve this level of accuracy, a prospect that is not unfeasible for models with sufficient flexibility

Understanding the potential for marine megafauna entanglement risk from renewable marine energy developments

PublishedThis is the final version of the article. Available from the Scottish National Heritage via the link in this record.Commissioned Report No. 791 Project no: 14635 Contractor: Scottish Association for Marine Science Research Services Ltd and the University of Exeter Year of publication: 2014Scottish Natural Heritag

Enhancing the cosmic shear power spectrum

Applying a transformation to a non-Gaussian field can enhance the information content of the resulting power spectrum, by reducing the correlations between Fourier modes. In the context of weak gravitational lensing, it has been shown that this gain in information content is significantly compromised by the presence of shape noise. We apply clipping to mock convergence fields, a technique which is known to be robust in the presence of noise and has been successfully applied to galaxy number density fields. When analysed in isolation the resulting convergence power spectrum returns degraded constraints on cosmological parameters. However, substantial gains can be achieved by performing a combined analysis of the power spectra derived from both the original and transformed fields. Even in the presence of realistic levels of shape noise, we demonstrate that this approach is capable of reducing the area of likelihood contours within the Ωm − σ8 plane by more than a factor of 3

Constraining modified gravity with weak-lensing peaks

\ua9 2024 The Author(s)It is well established that maximizing the information extracted from upcoming and ongoing stage-IV weak-lensing surveys requires higher order summary statistics that complement the standard two-point statistics. In this work, we focus on weak-lensing peak statistics to test two popular modified gravity models, f(R) and nDGP, using the FORGE and BRIDGE weak-lensing simulations, respectively. From these simulations, we measure the peak statistics as a function of both cosmological and modified gravity parameters simultaneously. Our findings indicate that the peak abundance is sensitive to the strength of modified gravity, while the peak two-point correlation function is sensitive to the nature of the screening mechanism in a modified gravity model. We combine these simulated statistics with a Gaussian Process Regression emulator and a Gaussian likelihood to generate stage-IV forecast posterior distributions for the modified gravity models. We demonstrate that, assuming small scales can be correctly modelled, peak statistics can be used to distinguish general relativity from f(R) and nDGP models at the 2σ level with a stage-IV survey area of 300 and 1000 deg2, respectively. Finally, we show that peak statistics can constrain log10 (|fR0|) = −6 per cent to 2 per cent precision, and log10(H0rc) = 0.5 per cent to 25 per cent precision

Are transnational tobacco companies' market access strategies linked to economic development models? A case study of South Korea.

Transnational tobacco companies (TTCs) have used varied strategies to access previously closed markets. Using TTCs' efforts to enter the South Korean market from the late 1980s as a case study, this article asks whether there are common patterns in these strategies that relate to the broader economic development models adopted by targeted countries. An analytical review of the existing literature on TTCs' efforts to access emerging markets was conducted to develop hypotheses relating TTCs' strategies to countries' economic development models. A case study of Korea was then undertaken based on analysis of internal tobacco industry documents. Findings were consistent with the hypothesis that TTCs' strategies in Korea were linked to Korea's export-oriented economic development model and its hostile attitude towards foreign investment. A fuller understanding of TTCs' strategies for expansion globally can be derived by locating them within the economic development models of specific countries or regions. Of foremost importance is the need for governments to carefully balance economic and public health policies when considering liberalisation

Magnetic moment of welded HTS samples: dependence on the current flowing through the welds

We present a method to calculate the magnetic moments of the high-temperature superconducting (HTS) samples which consist of a few welded HTS parts. The approach is generalized for the samples of various geometrical shapes and an arbitrary number of welds. The obtained relations between the sample moment and the density of critical current, which flows through the welds, allow to use the magnetization loops for a quantitative characterization of the weld quality in a wide range of temperatures and/or magnetic fields.Comment: RevTeX4, 4 pages, 2 figures. Submitted to Supercond. Sci. Techno