| 1. |
- Allanach, Benjamin C., et al.
(author)
-
Simple and statistically sound strategies for analysing physical theories
- 2022
-
In: Reports on progress in physics (Print). - : Institute of Physics Publishing (IOPP). - 0034-4885 .- 1361-6633. ; 85:5
-
Research review (peer-reviewed)abstract
- Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at Zenodo.
|
|
| 2. |
- Balázs, Csaba, et al.
(author)
-
Cosmological constraints on decaying axion-like particles : a global analysis
- 2022
-
In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :12
-
Journal article (peer-reviewed)abstract
- Axion-like particles (ALPs) decaying into photons are known to affect a wide range of astrophysical and cosmological observables. In this study we focus on ALPs with masses in the keV–MeV range and lifetimes between 104 and 1013 seconds, corresponding to decays between the end of Big Bang Nucleosynthesis and the formation of the Cosmic Microwave Background (CMB). Using the CosmoBit module of the global fitting framework GAMBIT, we combine state-of-the-art calculations of the irreducible ALP freeze-in abundance, primordial element abundances (including photodisintegration through ALP decays), CMB spectral distortions and anisotropies, and constraints from supernovae and stellar cooling. This approach makes it possible for the first time to perform a global analysis of the ALP parameter space while varying the parameters of ΛCDM as well as several nuisance parameters. We find a lower bound on the ALP mass of around ma > 300 keV, which can only be evaded if ALPs are stable on cosmological timescales. Future observations of CMB spectral distortions with a PIXIE-like mission are expected to improve this bound by two orders of magnitude.
|
|
| 3. |
- Bloor, Sanjay, et al.
(author)
-
The GAMBIT Universal Model Machine : from Lagrangians to likelihoods
- 2021
-
In: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 81:12
-
Journal article (peer-reviewed)abstract
- We introduce the GAMBIT Universal Model Machine (GUM), a tool for automatically generating code for the global fitting software framework GAMBIT, based on Lagrangian-level inputs. GUM accepts models written symbolically in FeynRules and SARAH formats, and can use either tool along with MadG rap h and CaIcHEP to generate GAMBIT model, collider, dark matter, decay and spectrum code, as well as GAMBIT interfaces to corresponding versions of SPheno, micrOMEGAs, Pythia and Vevacious (C++). In this paper we describe the features, methods, usage, pathways, assumptions and current limitations of GUM. We also give a fully worked example, consisting of the addition of a Majorana fermion simplified dark matter model with a scalar mediator to GAMBIT via GUM, and carry out a corresponding fit.
|
|
| 4. |
- Keddie, Amanda, et al.
(author)
-
What needs to happen for school autonomy to be mobilised to create more equitable public schools and systems of education?
- 2023
-
In: The Australian Educational Researcher. - : Springer. - 0311-6999 .- 2210-5328. ; 50:5, s. 1571-1597
-
Journal article (peer-reviewed)abstract
- The series of responses in this article were gathered as part of an online mini conference held in September 2021 that sought to explore different ideas and articulations of school autonomy reform across the world (Australia, Canada, England, Ireland, the USA, Norway, Sweden and New Zealand). It centred upon an important question: what needs to happen for school autonomy to be mobilised to create more equitable public schools and systems of education? There was consensus across the group that school autonomy reform creates further inequities at school and system levels when driven by the logics of marketisation, competition, economic efficiency and public accountability. Against the backdrop of these themes, the conference generated discussion and debate where provocations and points of agreement and disagreement about issues of social justice and the mobilisation of school autonomy reform were raised. As an important output of this discussion, we asked participants to write a short response to the guiding conference question. The following are these responses which range from philosophical considerations, systems and governance perspectives, national particularities and teacher and principal perspectives.
|
|
| 5. |
- Malbet, F., et al.
(author)
-
Faint objects in motion: the new frontier of high precision astrometry
- 2021
-
In: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 51:3, s. 845-886
-
Journal article (peer-reviewed)abstract
- Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of Earth-mass habitable worlds around the nearest stars, to distant Milky Way objects, and out to the Local Group of galaxies. As we enter the era of the James Webb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local Universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry missions: NEAT proposed for the ESA M3 opportunity, micro-NEAT for the S1 opportunity, and Theia for the M4 and M5 opportunities. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this White Paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review instrumentation and mission profiles.
|
|
| 6. |
- Renk, Janina J., et al.
(author)
-
CosmoBit : a GAMBIT module for computing cosmological observables and likelihoods
- 2021
-
In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2
-
Journal article (peer-reviewed)abstract
- We introduce CosmoBit, a module within the open-source GAMBIT software framework for exploring connections between cosmology and particle physics with joint global fits. CosmoBit provides a flexible framework for studying various scenarios beyond ACDM, such as models of inflation, modifications of the effective number of relativistic degrees of freedom, exotic energy injection from annihilating or decaying dark matter, and variations of the properties of elementary particles such as neutrino masses and the lifetime of the neutron. Many observables and likelihoods in CosmoBit are computed via interfaces to AlterBBN, CLASS, DarkAges, MontePython, MultiModeCode, and plc. This makes it possible to apply a wide range of constraints from large-scale structure, Type Ia supernovae, Big Bang Nucleosynthesis and the cosmic microwave background. Parameter scans can be performed using the many different statistical sampling algorithms available within the GAMBIT framework, and results can be combined with calculations from other GAMBIT modules focused on particle physics and dark matter. We include extensive validation plots and a first application to scenarios with non-standard relativistic degrees of freedom and neutrino temperature, showing that the corresponding constraint on the sum of neutrino masses is much weaker than in the standard scenario.
|
|
| 7. |
- Renk, Janina J., 1990-
(author)
-
Delving in the Dark : Searching for Signatures of Non-Standard Physics in Cosmological and Astrophysical Observables
- 2020
-
Doctoral thesis (other academic/artistic)abstract
- The dark sectors of our Universe, dark matter and dark energy, together constitute about 96 % of the total energy content of the Universe. To date, we only have observational evidence for their existence. What is still lacking is a complete theoretical framework consistent with all observational data to embed a dark matter particle or component into the standard models of particle physics and cosmology, as well as an explanation for the nature or origin of dark energy.Since the discovery of these dark components decades ago, a variety of different theories have been proposed to overcome the shortcomings of our current standard models. To assess the viability of these non-standard theories, they ideally should be tested against all relevant available datasets. In this thesis, I show two examples of how cosmological and astrophysical observables are used to constrain or even rule out non-standard cosmological models. Further, I present the first software tool that provides a general framework to test non-standard physics with global fits to data from particle physics and cosmology simultaneously.The first example is minimally coupled covariant Galileons, a modification of General Relativity to explain dark energy without the need for a fine-tuned cosmological constant. I demonstrate how the combination of constraints arising from the integrated Sachs-Wolf effect and the propagation speed of gravitational waves can rule out all three branches of the theory.The second example shows how the existence and parameter space of cosmic superstrings can be constrained. These are the hypothesised fundamental building blocks of Type IIb Superstring theory, stretched out to cosmological scales during the phase of inflation. The theory can be tested through the unique microlensing signature of cosmic superstrings when crossing the line of sight of an observer monitoring a point-like source. I show how, based on simulations, we can estimate the expected detection rates from observations of distant Type Ia Supernovae and stars in Andromeda; from these estimates I assess the implications for the theory.Finally, I present CosmoBit, a new module for the Global and Modular Beyond-Standard Model Inference Tool (GAMBIT). \gambit allows the user to test a variety of extensions to the Standard Model of particle physics against data from, e.g. collider searches, dark matter direct and indirect detection experiments, as well as laboratory measurements of neutrino properties. CosmoBit augments this with the inclusion of cosmological likelihoods. This addition opens up the possibility to test a given model against data from, e.g. the Big Bang Nucleosynthesis proceeding minutes after the Big Bang, probes of the Cosmic Microwave Background ~ 380,000 years later, and (laboratory) measurements from the present day, 13.8 billion years after the Big Bang. Including measurements that span several different epochs and orders of magnitude in energy, the combination of CosmoBit with other GAMBIT modules provides a promising tool for shedding light on the dark sectors of the Universe.
|
|
