39 research outputs found
The variation of G in a negatively curved space-time
Scalar-tensor (ST) gravity theories provide an appropriate theoretical
framework for the variation of Newton's fundamental constant, conveyed by the
dynamics of a scalar-field non-minimally coupled to the space-time geometry.
The experimental scrutiny of scalar-tensor gravity theories has led to a
detailed analysis of their post-newtonian features, and is encapsulated into
the so-called parametrised post-newtonian formalism (PPN). Of course this
approach can only be applied whenever there is a newtonian limit, and the
latter is related to the GR solution that is generalized by a given ST solution
under consideration. This procedure thus assumes two hypothesis: On the one
hand, that there should be a weak field limit of the GR solution; On the other
hand that the latter corresponds to the limit case of given ST solution. In the
present work we consider a ST solution with negative spatial curvature. It
generalizes a general relativistic solution known as being of a degenerate
class (A) for its unusual properties. In particular, the GR solution does not
exhibit the usual weak field limit in the region where the gravitational field
is static. The absence of a weak field limit for the hyperbolic GR solution
means that such limit is also absent for comparison with the ST solution, and
thus one cannot barely apply the PPN formalism. We therefore analyse the
properties of the hyperbolic ST solution, and discuss the question o defining a
generalised newtonian limit both for the GR solution and for the purpose of
contrasting it with the ST solution. This contributes a basic framework to
build up a parametrised pseudo-newtonian formalism adequate to test ST
negatively curved space-times.Comment: 7 pages, 5 figures. Contribution to the Joint European and National
Astronomy Meeting (JENAM) 2010; based on a talk given by JPM in the "From
Varying Couplings to Fundamental Physics" Symposiu
Lifestyle gambling, indebtedness and anxiety: A deviant leisure perspective
While once subject to wide-ranging state control, gambling has successfully culturally embedded itself within the normalised and legitimised forms of leisure such as the night-time economy, sports fandom and online forums of socialisation. Consequently, this article argues that existing research which conceptualises gambling as separate from everyday life is largely obsolete in the contemporary context. We argue here that gambling has become an integral feature of the wider masculine weekend leisure experience, intimately connected to an infantilised consumer identity that is peculiar to late-capitalism. This article, drawing upon ongoing ethnographic research among what we term ‘lifestyle gamblers’, utilises a deviant leisure perspective to problematise the myriad harms that emerge from this relationship, situated within a broader critique of consumerism and global capitalism. While social gambling is defended fiercely by the industry, this article argues that an identity-based culture of sports-betting that attaches fragile social and cultural capital to the allure of the gambling win encourages the chasing of losses and impulsive betting. Underscored by a culture of readily available and high-interest credit, we explore how gamblers in a technologically accelerated culture develop a pathological relationship to money as it becomes desublimated and loses its symbolic value. Such processes, exacerbated by the promise of consumer culture, have the potential to cast these young adults into a paralysing reality of indebtedness that is fraught with depression, stress, domestic instability and destructive behaviours of consumption
Exploring Cosmic Origins with CORE: Survey requirements and mission design
Future observations of cosmic microwave background (CMB) polarisation havethe potential to answer some of the most fundamental questions of modernphysics and cosmology. In this paper, we list the requirements for a future CMBpolarisation survey addressing these scientific objectives, and discuss thedesign drivers of the CORE space mission proposed to ESA in answer to the "M5"call for a medium-sized mission. The rationale and options, and themethodologies used to assess the mission's performance, are of interest toother future CMB mission design studies. CORE is designed as a near-ultimateCMB polarisation mission which, for optimal complementarity with ground-basedobservations, will perform the observations that are known to be essential toCMB polarisation scienceand cannot be obtained by any other means than adedicated space mission
Euclid preparation XXVIII. Forecasts for ten different higher-order weak lensing statistics
Recent cosmic shear studies have shown that higher-order statistics (HOS) developed by independent teams now outperform standard two-point estimators in terms of statistical precision thanks to their sensitivity to the non-Gaussian features of large-scale structure. The aim of the Higher-Order Weak Lensing Statistics (HOWLS) project is to assess, compare, and combine the constraining power of ten different HOS on a common set of Euclid-like mocks, derived from N-body simulations. In this first paper of the HOWLS series, we computed the nontomographic (Ωm, σ8) Fisher information for the one-point probability distribution function, peak counts, Minkowski functionals, Betti numbers, persistent homology Betti numbers and heatmap, and scattering transform coefficients, and we compare them to the shear and convergence two-point correlation functions in the absence of any systematic bias. We also include forecasts for three implementations of higher-order moments, but these cannot be robustly interpreted as the Gaussian likelihood assumption breaks down for these statistics. Taken individually, we find that each HOS outperforms the two-point statistics by a factor of around two in the precision of the forecasts with some variations across statistics and cosmological parameters. When combining all the HOS, this increases to a 4.5 times improvement, highlighting the immense potential of HOS for cosmic shear cosmological analyses with Euclid. The data used in this analysis are publicly released with the paper
Varying constants, Gravitation and Cosmology
Fundamental constants are a cornerstone of our physical laws. Any constant
varying in space and/or time would reflect the existence of an almost massless
field that couples to matter. This will induce a violation of the universality
of free fall. It is thus of utmost importance for our understanding of gravity
and of the domain of validity of general relativity to test for their
constancy. We thus detail the relations between the constants, the tests of the
local position invariance and of the universality of free fall. We then review
the main experimental and observational constraints that have been obtained
from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites
dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic
microwave background and big bang nucleosynthesis. At each step we describe the
basics of each system, its dependence with respect to the constants, the known
systematic effects and the most recent constraints that have been obtained. We
then describe the main theoretical frameworks in which the low-energy constants
may actually be varying and we focus on the unification mechanisms and the
relations between the variation of different constants. To finish, we discuss
the more speculative possibility of understanding their numerical values and
the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit
EELT-HIRES the high-resolution spectrograph for the E-ELT
The first generation of E-ELT instruments will include an optic-infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study.This work was supported from the Italian National Institute for Astrophysics (Istituto Nazionale Italiano di Astrofisica, INAF). RM , DB, CH, MF, XS, DQ and MGH acknowledge support from the UK Science and Technology Facilities Council (STFC). MGH is supported by the ERC Advanced grant Emergence-32056. This work was supported by Fundaçao para a Ciência e a Tecnologia (FCT, Portugal), project ref. PTDC/FIS-AST/1526/2014, through national funds and by FEDER through COMPETE2020 (ref. POCI-01-0145-FEDER-016886), as well as through grant UID/FIS/04434/2013 (POCI-01-0145-FEDER-007672). P.F. and N.C.S. also acknowledge the support from FCT through Investigador FCT contracts of reference IF/01037/2013, IF/00169/2012, and IF/00028/2014, respectively, and POPH/FSE (EC) by FEDER funding through the program “Programa Operacional de Factores de Competitividade - COMPETE”. P.F. further acknowledge support from FCT in the form of exploratory projects of reference IF/01037/2013CP1191/CT0001 and IF/00028/2014/CP1215/CT0002. PJA acknowledges financial support from AYA2011-30147-C03-01 and AYA2014-54348-C3-1-R by MINECO/Spain, partially supported by FEDER funds/EU. Research activities of the Board of Stellar Astronomy, at the Federal University of Rio Grande do Norte are supported by continuous grant of CNPq, FAPERN and CAPES brazilian agencies and by the INCT INEspaço. E.D.M and V.Zh.A. also acknowledge the support from the FCT (Portugal) in the form of the grants SFRH/BPD/76606/2011 and SFRH/BPD/70574/2010, respectively
Quantum Spacetime Phenomenology
I review the current status of phenomenological programs inspired by
quantum-spacetime research. I stress in particular the significance of results
establishing that certain data analyses provide sensitivity to effects
introduced genuinely at the Planck scale. And my main focus is on
phenomenological programs that managed to affect the directions taken by
studies of quantum-spacetime theories.Comment: 125 pages, LaTex. This V2 is updated and more detailed than the V1,
particularly for quantum-spacetime phenomenology. The main text of this V2 is
about 25% more than the main text of the V1. Reference list roughly double
Exploring cosmic origins with CORE: Mitigation of systematic effects
We present an analysis of the main systematic effects that could impact the measurement of CMB polarization with the proposed CORE space mission. We employ timeline-to-map simulations to verify that the CORE instrumental set-up and scanning strategy allow us to measure sky polarization to a level of accuracy adequate to the mission science goals. We also show how the CORE observations can be processed to mitigate the level of contamination by potentially worrying systematics, including intensity-to-polarization leakage due to bandpass mismatch, asymmetric main beams, pointing errors and correlated noise. We use analysis techniques that are well validated on data from current missions such as Planck to demonstrate how the residual contamination of the measurements by these effects can be brought to a level low enough not to hamper the scientific capability of the mission, nor significantly increase the overall error budget. We also present a prototype of the CORE photometric calibration pipeline, based on that used for Planck, and discuss its robustness to systematics, showing how CORE can achieve its calibration requirements. While a fine-grained assessment of the impact of systematics requires a level of knowledge of the system that can only be achieved in a future study phase, the analysis presented here strongly suggests that the main areas of concern for the CORE mission can be addressed using existing knowledge, techniques and algorithms
Cosmology intertwined: A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies
The standard Cold Dark Matter (CDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0 σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade’s experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density m, and the amplitude or rate of the growth of structure (σ8, f σ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions