COBE Constraints on a Compact Toroidal Low-density Universe

In this paper, the cosmic microwave background (CMB) anisotropy in a multiply-connected compact flat 3-torus model with the cosmological constant is investigated. Using the COBE-DMR 4-year data, a full Bayesian analysis revealed that the constraint on the topology of the flat 3-torus model with low-matter-density is less stringent. As in compact hyperbolic models, the large-angle temperature fluctuations can be produced as the gravitational potential decays at the $\Lambda$-dominant epoch well after the last scattering. The maximum allowed number $N$ of images of the cell (fundamental domain) within the observable region at present is approximately 49 for $\Omega_m=0.1$ and $\Omega_\Lambda=0.9$ whereas $N\sim8$ for $\Omega_m=1.0$ and $\Omega_\Lambda=0$.Comment: 13 pages using RevTeX, 5 eps files, typos correcte

Scientific modelling can be accessible, interoperable and user friendly: A case study for pasture and livestock modelling in Spain

This article describes the adaptation of a non-spatial model of pastureland dynamics, including vegetation life cycle, livestock management and nitrogen cycle, for use in a spatially explicit and modular modelling platform (k.LAB) dedicated to make data and models more interoperable. The aim is to showcase to the social-ecological modelling community the delivery of an existing, monolithic model, into a more modular, transparent and accessible approach to potential end users, regional managers, farmers and other stakeholders. This also allows better usability and adaptability of the model beyond its originally intended geographical scope (the Cantabrian Region in the North of Spain). The original code base (written in R in 1,491 lines of code divided into 13 files) combines several algorithms drawn from the literature in an opaque fashion due to lack of modularity, non-semantic variable naming and implicit assumptions. The spatiotemporal rewrite is structured around a set of 10 namespaces called PaL (Pasture and Livestock), which includes 198 interoperable and independent models. The end user chooses the spatial and temporal context of the analysis through an intuitive web-based user interface called k.Explorer. Each model can be called individually or in conjunction with the others, by querying any PaL-related concepts in a search bar. A scientific dataflow and a provenance diagram are produced in conjunction with the model results for full transparency. We argue that this work demonstrates key steps needed to create more Findable, Accessible, Interoperable and Reusable (FAIR) models beyond the selected example. This is particularly essential in environments as complex as agricultural systems, where multidisciplinary knowledge needs to be integrated across diverse spatial and temporal scales in order to understand complex and changing problems. © 2023 Marquez Torres et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The authors would like to thank Joan Busqué who created and shared the original Puerto model and the team lead by José Barquín at the Hydrological Institute of Cantabria (IHC). Special thanks to Simone Langhans and Ken Bagstad who suggested revisions to the article. Robinson et al. (2014) for logistic support for EarthEnv-DEM90

Affine equation of state from quintessence and k-essence fields

We explore the possibility that a scalar field with appropriate Lagrangian can mimic a perfect fluid with an affine barotropic equation of state. The latter can be thought of as a generic cosmological dark component evolving as an effective cosmological constant plus a generalized dark matter. As such, it can be used as a simple, phenomenological model for either dark energy or unified dark matter. Furthermore, it can approximate (up to first order in the energy density) any barotropic dark fluid with arbitrary equation of state. We find that two kinds of Lagrangian for the scalar field can reproduce the desired behaviour: a quintessence-like with a hyperbolic potential, or a purely kinetic k-essence one. We discuss the behaviour of these two classes of models from the point of view of the cosmological background, and we give some hints on their possible clustering properties.Comment: 9 pages, 6 figures. Minor updates, accepted by CQ

Goodness-of-fit tests of Gaussianity: constraints on the cumulants of the MAXIMA data

In this work, goodness-of-fit tests are adapted and applied to CMB maps to detect possible non-Gaussianity. We use Shapiro-Francia test and two Smooth goodness-of-fit tests: one developed by Rayner and Best and another one developed by Thomas and Pierce. The Smooth tests test small and smooth deviations of a prefixed probability function (in our case this is the univariate Gaussian). Also, the Rayner and Best test informs us of the kind of non-Gaussianity we have: excess of skewness, of kurtosis, and so on. These tests are optimal when the data are independent. We simulate and analyse non-Gaussian signals in order to study the power of these tests. These non-Gaussian simulations are constructed using the Edgeworth expansion, and assuming pixel-to-pixel independence. As an application, we test the Gaussianity of the MAXIMA data. Results indicate that the MAXIMA data are compatible with Gaussianity. Finally, the values of the skewness and kurtosis of MAXIMA data are constrained by |S| \le 0.035 and |K| \le 0.036 at the 99% confidence level.Comment: New Astronomy Reviews, in pres

Discrete event front tracking simulator of a physical fire spread model

International audienceSimulation of moving interfaces, like a fire front usually requires the resolution of a large scale and detailed domain. Such computing involves the use of supercomputers to process the large amount of data and calculations. This limitation is mainly due to the fact that large scale of space and time is usually split into nodes, cells or matrices, and the solving methods often require small time steps. This paper presents a novel method that enables the simulation of large scale/high resolution systems by focusing on the interface. Unlike the conventional explicit and implicit integration schemes, it is based on the discrete-event approach, which describes time advance in terms of increments of physical quantities rather than discrete time stepping. Space as well is not split into discrete nodes or cells, but we use polygons with real coordinates. The system is described by the behaviour of its interface, and evolves by computing collision events of this interface in the simulation. As this simulation technique is suited for a class of models that can explicitly provide rate of spread for a given configuration, we developed a specific radiation based propagation model of physical wildland fire. Simulations of a real large scale fire performed with an implementation of our method provide very interesting results in less than 30 seconds with a 3 metres resolution with current personal computers

Implications for quintessence models from MAXIMA-1 and BOOMERANG-98

Prompted by the recent MAXIMA-1 and BOOMERANG-98 measurements of the cosmic microwave background (CMB) anisotropy power spectrum, and motivated by the results from the observation of high-redshift Type Ia supernovae, we investigate CMB anisotropies in quintessence models in order to characterize the nature of the dark energy today. We perform a Bayesian likelihood analysis, using the MAXIMA-1 and BOOMERANG-98 published bandpowers, in combination with COBE/DMR, to explore the space of quintessence parameters: the quintessence energy density \Omega_\phi and equation of state w_\phi. We restrict our analysis to flat, scale-invariant, inflationary adiabatic models. We find that this simple class of inflationary models, with a quintessence component \Omega_\phi < ~0.7, -1 < = w_\phi < ~-0.5, is in good agreement with the data. Within the assumptions of our analysis, pure quintessence models seem to be slightly favored, although the simple cosmological constant scenario is consistent with the data.Comment: 4 pages, 3 figures. Reflects version accepted for publication by ApJ Letter

Cosmological parameters and the WMAP data revisited

Several recent papers have made claims about the detection of an asymmetric distribution of large scale power in the cosmic microwave background anisotropy as measured by the WMAP satellite. In this paper, we investigate how the estimates of particular cosmological parameters vary when inferred from power spectra computed separately on the northern and southern hemispheres in three frames of reference. We focus our investigation on the three specific parameters to which the analysis is most sensitive, the spectral index n, the amplitude of fluctuations A and the optical depth tau. When using a gaussian prior on the spectral index n centred at n=1 with a flat prior on the optical depth tau, the preferred value for the optical depth (derived in the reference frame of maximum asymmetry) in the north is tau=0 with upper limit tau<0.08, whereas in the south we find tau=0.24 +0.06/-0.07 (68% confidence level). The latter result is inconsistent with tau=0 at the 2 sigma level. The estimated optical depth of tau=0.17 on the (nearly) full sky found by the WMAP collaboration and confirmed independently here, could thus in large part originate in structure associated with the southern hemisphere. Furthermore, putting a prior on tau, we find values of the spectral index which are inconsistent between the opposite hemispheres. The exact values depend on the prior on tau. While our results should not be considered more than suggestive, the significance of the parameter differences in the two hemispheres being typically of order 2 sigma, if they are confirmed with the higher sensitivity WMAP 2-year data then it may be necessary to question the assumption of cosmological isotropy and the conceptual framework within which studies of the CMB anisotropy are made.Comment: submitted to MNRA

A game theory model to explore the role of cooperation and diversity in community food security: the case of Southern Malawi

The Sustainable Development Goals aim at ending food insecurity by 2030. Therefore, civil society needs to understand the inherent complexities of both socio-economic and ecological dynamics and their interdependencies. In particular, the behavioural dynamics that underpin human agents are crucial in driving the final outcomes in terms of community food security and require further attention. Using household behaviour within a rural village of Southern Malawi as an example, we describe a game theory model representing cropping strategies: (1) cooperation, as driven by other-regarding preferences, and (2) conformation, the tendency to converge to similar crop planting choices as opposed to differentiation (and thus crop diversity). We find that the latter plays a crucial role in driving the system towards successful strategies: how individuals relate to social norms has greater effect. Cooperation is only necessary for community success when the community converges on crop planting choices. On the contrary, differentiation, the affirmation of the individual unique identity, can succeed with or without cooperation. We further elaborate on the idea that community level sustainability can be reached through different pathways, which might require food exchange mechanisms within and beyond the system boundaries. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.This research is supported by the Basque Government through the BERC 2018-2021 program and by the Ikertzaile Doktoreentzako Hobekuntzarako doktoretza-ondoko Programa and by Spanish Ministry of Economy and Competitiveness MINECO through BC3 María de Maeztu excellence accreditation MDM-2017-0714 and by the Leverhulme TrustResearch Fellowship “CREATE: the network components of creativity and success. This work was also inspired and partially funded by the ASSETS (Attaining Sustainable Services from Ecosystems) project (NERC/ESPA NE-J002267-1)

What's Behind Acoustic Peaks in the Cosmic Microwave Background Anisotropies

We give a brief review of the physics of acoustic oscillations in Cosmic Microwave Background (CMB) anisotropies. As an example of the impact of their detection in cosmology, we show how the present data on CMB angular power spectrum on sub-degree scales can be used to constrain dark energy cosmological models.Comment: 6 pages, proceedings to the TAUP2001 conference, LNGS, Italy, Sept. 200