Cosmological Research Articles

Erratum: Observations in statistically homogeneous, locally inhomogeneous cosmological toy-models without FLRW backgrounds

Erratum: Observations in statistically homogeneous, locally inhomogeneous cosmological toy-models without FLRW backgrounds

Created Co-creator, a Theory of Human Becoming in an Era of Science and Technology

Scientific discoveries and the emergence of cosmological theories such as the Big Bang Theory and evolution have challenged the Christian doctrine of creation and its reliability on many fronts, because the discoveries appear to contradict the Christian account as to how creation unfolded. Hefner sees the situation as an additional interpretative task to theologians. He, however, posits that scientific discoveries are an opportunity to communicate the Christian message through social and scientific experience to bring meaning to broader society. He expresses the notion that religion will remain relevant only if it measures up to science, because we are in a science and technology era. Hefner, therefore, introduced the concept of created co-creator as a metaphor and analytical tool to explain the meaning and purpose of humans within the biosphere. The concept is characterized by the ability to communicate religion through science and to relate with available models of origin. This work expounds on the concept of created co-creator’s ability to explain human technological trajectory in theology. There is also an effort to establish a relationship between Hefner’s concept and Haraway’s cyborg with an emphasis on the concept’s ability to communicate the Christian doctrine of creation through scientific knowledge and why such an enterprise is useful.

La metáfora del hilo en la práctica artística. Alegorías de un viaje

Bajo la premisa de que, la tradición alegórica se ha trasladado durante siglos al imaginario popular colectivo gracias a la incesante transmisión de ciertas cosmogonías, mitos y leyendas por medio de todo tipo de medios como los orales, los impresos o los audiovisuales, el presente texto tiene como objetivo otear cómo el arte contemporáneo sigue generando procesos de semiosis fundamentados en este tipo de evocaciones, centrándonos únicamente en el enclave interpretativo del hilo y sus adyacentes –como la acción de tejer–. Nos ayudaremos para ello de los estudios sobre mitología antigua y cultura indígena de autores como Danesi (2004), Pintado (2012) Aguilera (2014) y Fernández (2012), para relacionarlos con la práctica artística, especialmente en torno a la obra de dos autoras contemporáneas que han hecho del hilo su material plástico: en este caso, artistas de la talla de la chino-estadounidense Beili Liu y la franco-americana Louise Joséphine Bourgeois.

Causality in curved spacetimes: The speed of light and gravity

Within the low-energy effective field theories of QED and gravity, the low-energy speed of light or that of gravitational waves can typically be mildly superluminal in curved spacetimes. Related to this, small scattering time advances relative to the curved background can emerge from known effective field theory coefficients for photons or gravitons. We clarify why these results are not in contradiction with causality, analyticity or Lorentz invariance, and highlight various subtleties that arise when dealing with superluminalities and time advances in the gravitational context. Consistent low-energy effective theories are shown to self-protect by ensuring that any time advance and superluminality calculated within the regime of validity of the effective theory is necessarily unresolvable, and cannot be argued to lead to a macroscopically larger lightcone. Such considerations are particularly relevant for putting constraints on cosmological and gravitational effective field theories and we provide explicit criteria to be satisfied so as to ensure causality.

Cosmological Special Theory of Relativity

In the Cosmological Special Relativity Theory, we study Maxwell equations, electromagnetic wave equation and function.

Sam McBride, Tolkien's Cosmology: Divine Beings and Middle-earth

Sam McBride, <i>Tolkien's Cosmology: Divine Beings and Middle-earth</i>

Gravitational theory of cosmology, galaxies and galaxy clusters

A modified gravitational theory explains early universe and late time cosmology, galaxy and galaxy cluster dynamics. The modified gravity (MOG) theory extends general relativity (GR) by three extra degrees of freedom: a scalar field G, enhancing the strength of the Newtonian gravitational constant G_N, a gravitational, spin 1 vector graviton field phi _mu , and the effective mass mu of the ultralight spin 1 graviton. For t < t_mathrm{rec}, where t_mathrm{rec} denotes the time of recombination and re-ionization, the density of the vector graviton rho _phi > rho _b, where rho _b is the density of baryons, while for t > t_mathrm{rec} we have rho _b > rho _phi . The matter density is parameterized by Omega _M=Omega _b+Omega _phi +Omega _r where Omega _r=Omega _gamma +Omega _nu . For the cosmological parameter values obtained by the Planck Collaboration, the CMB acoustical oscillation power spectrum, polarization and lensing data can be fitted as in the Lambda CDM model. When the baryon density rho _b dominates the late time universe, MOG explains galaxy rotation curves, the dynamics of galaxy clusters, galaxy lensing and the galaxy clusters matter power spectrum without dominant dark matter.

Propagation of Massive Scalar Fields in Pre-Big Bang Cosmologies

We investigate the linear and semilinear massive Klein-Gordon equations in geometrical frameworks of type "Conformal Cyclic Cosmology" of R. Penrose, or "Singular Bouncing Scenario" as well. We give sufficient conditions on the decay of the mass to the fields be able to propagate across the Big-Bang.

Radial derivatives as a test of pre-big bang events on the Planck data

ABSTRACT Although the search for azimuthal patterns in cosmological surveys is useful to characterize some effects depending exclusively on an angular distance within the standard model, they are considered as a key distinguishing feature of some exotic scenarios, such as bubble collisions or conformal cyclic cosmology (CCC). In particular, the CCC is a non-stardard framework that predicts circular patterns on the cosmic microwave background intensity fluctuations. Motivated by some previous works that explore the presence of radial gradients, we apply a methodology based on the radial derivatives to the latest release of Planck data. The new approach allows exhaustive studies to be performed at all-sky directions at a healpix resolution of Nside = 1024. Specifically, two different analyses are performed focusing on weight functions in both small (up to a 5-deg radius) and large scales. We present a comparison between our results and those shown by An, Meissner &amp; Nurowski (2017) and An et al. (2018). In addition, a possible polarization counterpart of these circular patterns is also analysed for the most promising case. Taking into account the limitations to characterize the significance of the results, including the possibility of suffering a look-elsewhere effect, no strong evidence of the kind of circular patterns expected from CCC is found in the Planck data for either the small or the large scales.

Jump ship, shift gears, or just keep on chugging: Assessing the responses to tensions between theory and evidence in contemporary cosmology

When is it reasonable to abandon a scientific research program? When would it be premature? We take up these questions in the context of a contemporary debate at the border between astrophysics and cosmology, the so-called “small-scale challenges” to the concordance model of cosmology (ΛCDM) and its cold dark matter paradigm. These challenges consist in discrepancies between the outputs of leading cosmological simulations and observational surveys, and have garnered titles such as the Missing Satellites, Too Big To Fail, and Cusp/Core problems. We argue that these challenges do not currently support a wholesale abandonment or even modification of cold dark matter. Indeed, the nature of the challenges suggests prioritizing the incorporation of known physics into cosmological simulations.

A fundamental step towards the cosmological 21 cm signal

A fundamental step towards the cosmological 21 cm signal

Novel screening with two bodies: summing the ladder in disformal scalar-tensor theories

When augmenting our cosmological models or gravitational theories with an additional light scalar field, any coupling between matter and this scalar can affect the orbital motion of binary systems. Ordinarily, the new force mediated by the scalar can be naturally the same order of magnitude as the usual gravitational force and therefore is tightly constrained. We show that a disformal coupling between the scalar and matter can lead to a novel screening mechanism in which these fifth forces are suppressed by several orders of magnitude at sufficiently small separations and large relative velocities (such as solar system scales). This is a result of resumming a class of ladder diagrams, which suppresses the propagation of scalar signals between the two bodies. Moreover, we are able to relate potential ambiguities in this resummation to non-perturbative effects (which are invisible to perturbation theory). As a result, solar system tests and future gravitational wave observations can now be used to place meaningful constraints on scalar-tensor theories with disformal couplings. We exemplify this using observational bounds on the precession of planetary orbits.

UMA REFLEXÃO SOBRE O USO DE ANALOGIAS NO ENSINO DE CIÊNCIAS E O DESDOBRAMENTO MULTIMODAL DA REALIDADE: O EXEMPLO DE TÓPICOS DA TEORIA DA EVOLUÇÃO BIOLÓGICA

As analogias são uma fonte heurística de pensamento para compreensão ou transição de ideias para a formação dos conceitos científicos, sendo muito utilizadas por cientistas e no cotidiano. Neste ensaio, buscamos fazer uma aproximação do conceito de analogia modal da teoria dooyeweerdiana com a Metodologia de Ensino com Analogia (MECA), no intuito de enriquecer as percepções ordinárias dos signos e a abertura cultural analítica científica. Realizamos uma pesquisa de sondagem sobre métodos de ensino com uso de analogias, para em seguida expormos conceitos da teoria cosmonômica de Dooyeweerd buscando fundamentar o conceito de analogia modal, abertura cultural e princípio Shalom. Por fim, evidenciamos o diálogo dessa concepção filosófica dooyeweerdiana com o uso da MECA no exemplo da analogia da Árvore da Vida de Charles Darwin. Nessa interação percebemos o enriquecimento (abertura cultural) de relações analógicas já conhecidas de desenvolvimento evolutivo, extinção e aparecimento de espécimes em função dos órgãos vegetais gomos, folhas e ramos; a construção de novas relações analógicas modais para outros órgãos e situações em que o vegetal comumente sobrevive, como a presença dos seres nos meios ambientais distintos (aquáticos, terrestres e aéreos) e reprodução de caráter teleológico em relação aos órgãos de raízes e frutos; e também a discursividade do equilíbrio para o contexto social e ambiental por meio do princípio Shalom.

Comment on "Hiding the Cosmological Constant".

We comment on S. Carlip's recent Letter "Hiding the Cosmological Constant" [Phys. Rev. Lett. 123, 131302].

The Cosmology of Lists in Ancient and Contemporary Societies

The Cosmology of Lists in Ancient and Contemporary Societies

The logic and politics of cosmology

The logic and politics of cosmology

Photon mass limits driven by axions, Lorentz violation, chiral and gravitational anomalies in non-Riemannian spaces, and helical dynamo seeds

In this paper two types of applications of Cartan torsion to cosmology and quantum field theory are given. The first is given by massive photon axial torsion mixing through non-minimal coupling. It is shown that chiral anomalies induce upper limits on the photon mass and galactic dynamo seeds. In this example we obtain magnetic field seeds of the order of 10−16 G from a strong chiral battery magnetic field of the order of 1030 G. This cosmic magnetic field is in accordance with previous magnetic dynamo seed limits as 10−22 G ≤ Bseed ≤ 10−12 G given by Barrow et al. (Phys. Rev. D, 86, 023533 (2012). doi: 10.1103/PhysRevD.86.023533 ). In this example, as in the Prokopec et al. (Phys. Rev. Lett. 89, 101301 (2002). doi: 10.1103/PhysRevLett.89.101301 ) torsionless case, which associates Dolgov anomalies to photon mass limits, we show that at early universe scales, 10−32 eV is a very stringent limit. Here we can show that the parameter [Formula: see text], which is well within the lower bound of r needed for the magnetic field to seed galactic dynamos. Helical magnetic fields are obtained. One can also derive massive photon limits from axial chiral anomalies with torsion degrees of freedom (Duncan et al. Nucl. Phys. B, 387, 215 (1992). doi: 10.1016/0550-3213(92)90052-D ) leading to photon mass of the order of 10−11 eV. Dynamo equations are obtained from anomalous Maxwell equations as well as magnetic wave equations with photon mass, which are analytically solved. In the second example one shows that Chern–Simons (CS) current is affected by the presence of minimal coupled torsion. In this case as well one obtains a photon mass limit of the order 10−18 eV. Gravitational anomalies in Riemann–Cartan spacetime with axial torsion are also obtained. Recently, Terrano et al. (Phys. Rev. Lett. 122, 231301 (2019). doi: 10.1103/PhysRevLett.122.231301 ) computed dark matter mass constraints of the order of 10−23 eV from spin-polarised torsion balances, which has given some support for torsion theories of Einstein–Cartan type. Here, however, we deal with torsion with dynamical degrees of freedom. Lorentz violation in non-Riemannian CS currents are investigated.

Philosophical discussions around cosmology

This paper is a continuation of the previous work: V. Prits and V. Kuznetsov “The main fea- tures of the cosmological picture of the world.” After examining some of the discussions around newborn cosmology, the article considers cosmological problems from the point of view of the philosophy of modern cosmology. It is emphasized that today a single and coordi- nated view of cosmology and its philosophy has not been formed. The main objectives of the study are were, firstly, to identify some philosophical, methodological and anthropological problems in the study of the Universe and, secondly, to focus on the interac- tion of philosophy and cosmology. It has been revealed that the cosmological principles on which almost all cosmological theories and models are based have a long and dramatic ideological history and philosophical founda- tion, and the concept of “Multiverse” is saturated with ontological and epistemological puzzles. The principles of Bruno-Copernicus and the anthropic cosmological principles are proposed to be considered in the light of the discovery of exoplanets.

Primordial black holes from pre-big bang inflation

We discuss the possibility of producing a significant fraction of dark matter in the form of primordial black holes in the context of the pre-big bang inflationary scenario. We take into account, to this purpose, the enhancement of curvature perturbations possibly induced by a variation of the sound-speed parameter cs during the string phase of high-curvature inflation. After imposing all relevant observational constraints, we find that the considered class of models is compatible with the production of a large amount of primordial black holes in the mass range relevant to dark matter, provided the sound-speed parameter is confined in a rather narrow range of values, 0.003 ≲ cs ≲ 0.01.

The case for a Casimir cosmology.

The cosmological constant, also known as dark energy, was believed to be caused by vacuum fluctuations, but naive calculations give results in stark disagreement with fact. In the Casimir effect, vacuum fluctuations cause forces in dielectric media, which is very well described by Lifshitz theory. Recently, using the analogy between geometries and media, a cosmological constant of the correct order of magnitude was calculated with Lifshitz theory (Leonhardt 2019 Ann. Phys. (New York) 411, 167973. (doi:10.1016/j.aop.2019.167973)). This paper discusses the empirical evidence and the ideas behind the Lifshitz theory of the cosmological constant without requiring prior knowledge of cosmology and quantum field theory.This article is part of a discussion meeting issue ‘The next generation of analogue gravity experiments’.