Constrained realizations of Gaussian random fields are used in cosmology to design special initial conditions for numerical simulations. We review this approach and its application to density peaks ...providing several worked-out examples. We then critically discuss the recent proposal to use constrained realizations to modify the linear density field within and around the Lagrangian patches that form dark-matter haloes. The ambitious concept is to forge 'genetically modified' haloes with some desired properties after the non-linear evolution. We demonstrate that the original implementation of this method is not exact but approximate because it tacitly assumes that protohaloes sample a set of random points with a fixed mean overdensity. We show that carrying out a full genetic modification is a formidable and daunting task requiring a mathematical understanding of what determines the biased locations of protohaloes in the linear density field. We discuss approximate solutions based on educated guesses regarding the nature of protohaloes. We illustrate how the excursion-set method can be adapted to predict the non-linear evolution of the modified patches and thus fine tune the constraints that are necessary to obtain pre-selected halo properties. This technique allows us to explore the freedom around the original algorithm for genetic modification. We find that the quantity which is most sensitive to changes is the halo mass-accretion rate at the mass scale on which the constraints are set. Finally, we discuss constraints based on the protohalo angular momenta.
Food Heritage and Nationalism in Europe contends that food is a fundamental element of heritage, and a particularly important one in times of crisis. Arguing that food, taste, cuisine and gastronomy ...are crucial markers of identity that are inherently connected to constructions of place, tradition and the past, this book demonstrates how they play a role in intangible, as well as tangible, heritage.
Featuring contributions from experts working across Europe and beyond, and adopting a strong historical and transnational perspective, this book examines the various ways in which food can be understood and used as heritage. Including explorations of imperial spaces, migrations and diasporas, the role of commercialization processes, and institutional practices within political and cultural domains, this volume considers all aspects of this complex issue. Arguing that the various European cuisines are the result of exchanges, hybridities and complex historical processes, Porciani and the chapter authors offer up a new way of deconstructing banal nationalism and of moving away from the idea of static identities.
Suggesting a new and different approach to the idea of so-called national cuisines, Food Heritage and Nationalism in Europe will be a compelling read for academic audiences in museum and heritage studies, cultural and food studies, anthropology and history.
Food Heritage and Nationalism in Europe contends that food is a fundamental element of heritage, and a particularly important one in times of crisis. Arguing that food, taste, cuisine and gastronomy ...are crucial markers of identity that are inherently connected to constructions of place, tradition and the past, the book demonstrates how they play a role in intangible, as well as tangible, heritage.
Featuring contributions from experts working across Europe and beyond, and adopting a strong historical and transnational perspective, the book examines the various ways in which food can be understood and used as heritage. Including explorations of imperial spaces, migrations and diasporas; the role of commercialisation processes, and institutional practices within political and cultural domains, this volume considers all aspects of this complex issue.
Arguing that the various European cuisines are the result of exchanges, hybridities and complex historical processes, Porciani and the chapter authors offer up a new way of deconstructing banal nationalism and of moving away from the idea of static identities. Suggesting a new and different approach to the idea of so-called national cuisines, Food Heritage and Nationalism in Europe will be a compelling read for academic audiences in museum and heritage studies, cultural and food studies, anthropology and history.
Abstract
The clustering of dark matter haloes with fixed mass depends on their formation history, an effect known as assembly bias. We use zoom N-body simulations to investigate the origin of this ...phenomenon. For each halo at redshift z = 0, we determine the time in which the physical volume containing its final mass becomes stable. We consider five examples for which this happens at z ∼ 1.5 and two that do not stabilize by z = 0. The zoom simulations show that early-collapsing haloes do not grow in mass at z = 0 while late-forming ones show a net inflow. The reason is that ‘accreting’ haloes are located at the nodes of a network of thin filaments feeding them. Conversely, each ‘stalled’ halo lies within a prominent filament that is thicker than the halo size. Infalling material from the surroundings becomes part of the filament while matter within it recedes from the halo. We conclude that assembly bias originates from quenching halo growth due to tidal forces following the formation of non-linear structures in the cosmic web, as previously conjectured in the literature. Also the internal dynamics of the haloes change: the velocity anisotropy profile is biased towards radial (tangential) orbits in accreting (stalled) haloes. Our findings reveal the cause of the yet unexplained dependence of halo clustering on the anisotropy. Finally, we extend the excursion-set theory to account for these effects. A simple criterion based on the ellipticity of the linear tidal field combined with the spherical-collapse model provides excellent predictions for both classes of haloes.
ABSTRACT We present a method to test the isotropy of the magnitude-redshift relation of Type Ia Supernovae (SNe Ia) and single out the most discrepant direction (in terms of the signal-to-noise ...ratio) with respect to the all-sky data. Our technique accounts for possible directional variations of the corrections for SNe Ia and yields all-sky maps of the best-fit cosmological parameters with arbitrary angular resolution. To show its potential, we apply our method to the high-redshift SNe Ia from the recent Union2.1 compilation, building maps with three different angular resolutions. We use a Monte Carlo method to estimate the statistical significance with which we could reject the null hypothesis that the magnitude-redshift relation is isotropic based on the properties of the observed most discrepant directions. We find that, based on pure signal-to-noise arguments, the null hypothesis cannot be rejected at any meaningful confidence level. However, if we also consider that the strongest deviations in the Union2.1 sample closely align with the dipole temperature anisotropy of the cosmic microwave background, we find that the null hypothesis should be rejected at the 95%-99% confidence level, slightly depending on the angular resolution of the study. If this result is not due to a statistical fluke, it might either indicate that the SN data have not been cleaned from all possible systematics or even point toward new physics. We finally discuss future perspectives in the field for achieving larger and more uniform data sets that will vastly improve the quality of the results and optimally exploit our method.
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