Description Of Universe Research Articles

Hubble tension as a guide for refining the early Universe: Cosmologies with explicit local Lorentz and diffeomorphism violation

This paper is dedicated to assessing modified cosmological settings based on the gravitational Standard-Model Extension (SME). Our analysis rests upon the Hubble tension (HT), which is a discrepancy between the observational determination of the Hubble parameter via data from the Cosmic Microwave Background (CMB) and Type Ia supernovae, respectively. While the latter approach is model-independent, the former highly depends on the model used to describe the physics of the early Universe. Motivated by the HT, we take into account two recently introduced cosmological models as test frameworks of the pre-CMB era. These settings involve local Lorentz and diffeomorphism violation parameterized by nondynamical SME background fields $s_{00}$ and $s^{ij}$, respectively. We aim at explaining the tension in the measured results of the cosmic expansion rate in early and late epochs by resorting to these two modified cosmologies as potential descriptions of the pre-CMB era. As long as the HT does not turn out to be a merely systematic effect, it can serve as a criterion for exploring regions of the parameter space in certain pre-CMB new-physics candidates such as SME cosmologies. By setting extracted limits on SME coefficients into perspective with already existing bounds in the literature, we infer that none of the aforementioned models are suitable pre-CMB candidates for fixing the HT. In this way, new physics arising from the particular realizations of Lorentz and diffeomorphism violation studied in this paper does not explain the HT. Our paper exemplifies how to exploit this discrepancy as a novel possibility of refining our description of the early Universe.

Hackathon as an instrument for innovation in collaborative networks: a bibliometric analysis

Objective: The objective of this study is to analyze hackathon contributions as an instrument for innovation in collaborative networks.
 Methodology: A bibliometry was performed in the Scopus and Web of Science bases through the Bibliometrix packages and the R Studio software. Publications analysis techniques were used describing the year and the group of origin (by Bradford Law), authorship analysis by the authors' relevance and their productivity (by Lotka Law), scientific contributions by country and collaboration between countries, Quotations of document with the cloud of word, as well as a thematic description of the hackathons universe.
 Results: An exponential increase in scientific hackathon publications from 2019 has been verified. Hackathon studies address and connect the theme mainly with innovation, collaboration, open data, education and covid-19. The increase of hackathon studies occurred during the pandemic period.
 Limitations: The study was delimited in two databases (Scopus and Web of Science), and in the English language. The expansion to other bases and languages ​​can produce different results from the above, and represents a limitation of this study.
 Originality: The analyzes performed in this study made it possible to structuring the scientific literature on hackathon.

Spectral distortions from axion monodromy inflation

With the advent of new missions to probe spectral distortions of the cosmic microwave background with unprecedented precision, the study of theoretical predictions of these signals becomes a promising avenue to test our description of the early Universe. Meanwhile, axion monodromy still offers a viable framework to describe cosmic inflation. In order to explore new constraints on inflationary models based on axion monodromy while aiming at falsifying this scenario, we compute the spectral distortions predicted by this model, revealing oscillatory features that are compatible with Planck data. Further, the predicted distortions are up to 10% larger than the signals obtained from the fiducial ΛCDM model and are observable in principle. However, contrasting with the predictions of the simplest power-law inflationary potentials challenges the falsifiability of axion monodromy as it would require to reduce at least 100 times the current forecast error of the PIXIE satellite, which shall be possible at some projected observational setups.

Physical Eschatology: On the Nature of "the New Heavens and the New Earth"

For centuries, Christian believers have endured hardships and persecution with the hope of an eschatological transformation of life as we know it. While on this Earth we experience pain, suffering and death, the Bible speaks of a future transformation of physical reality, a “new heaven and a new earth” (Rev 21:1). However, how should Christians interpret this expression? Is it a physical description of the new universe? Or is it a reference to a change in political, social or spiritual conditions of society as a whole? How does this expression appear in the Old Testament and how is it used by New Testament writers? This article focuses on these questions and points to the intertextual elements between both Testaments while searching for a coherent interpretation of that emblematic expression.

A quantum state for the late Universe

We consider the quantum description of a toy model universe in which the Schwarzschild-de Sitter geometry emerges from the coherent state of a massless scalar field. Although highly idealised, this simple model allows us to find clear hints supporting the conclusion that the reaction of the de Sitter background to the presence of matter sources induces i) a modified Newtonian dynamics at galactic scales and ii) different values measured for the present Hubble parameter. Both effects stem from the conditions required to have a normalisable quantum state.

The S8 tension in light of updated redshift-space distortion data and PAge approximation

One of the most prominent challenges to the standard Lambda cold dark matter ($\Lambda$CDM) cosmology is the tension between the structure growth parameter $S_8$ constrained by the cosmic microwave background (CMB) data and the smaller one suggested by the cosmic shear data. Recent studies show that, for $\Lambda$CDM cosmology, redshift-space distortion (RSD) data also prefers a smaller $S_8$ that is $\sim 2$-$3\sigma$ lower than the CMB value, but the result is sensitive to the cosmological model. In the present work we update the RSD constraint on $S_8$ with the most up-to-date RSD data set where the correlation between data points are properly taken into account. To reduce the model dependence, we add in our Monte Carlo Markov Chain calculation the most up-to-date data sets of Type Ia supernovae (SN) and baryon acoustic oscillations (BAO), whose correlation with RSD is also taken into account, to constrain the background geometry. For $\Lambda$CDM cosmology we find $S_8= 0.812 \pm 0.026$, which is $\sim 2\sigma$ larger than previous studies, and hence is consistent with the CMB constraint. By replacing $\Lambda$CDM with the Parameterization based on cosmic Age (PAge), an almost model-independent description of the late universe, we find that the RSD + SN + BAO constraint on $S_8$ is insensitive to the cosmological model.

Holographic Description of the Early Universe

The holographic principle is applied to a description of the Universe in the early stage of its evolution. As an example, we examine a cosmological model with a bounce with subsequent transition to the early stage of inflation. We investigate cosmological models based on a viscous liquid with a generalized equation of state in terms of the holographic cutoff proposed by Nojiri and Odintsov. Within the framework of these models, we have calculated the infrared radius in terms of the particle horizon or the event horizon. Energy conservation laws are obtained from the holographic point of view. The viscous liquid describing the bounce and the early Universe is presented as a generalization of holographic energy.

A type- and scope-safe universe of syntaxes with binding: their semantics and proofs

Abstract The syntax of almost every programming language includes a notion of binder and corresponding bound occurrences, along with the accompanying notions of α-equivalence, capture-avoiding substitution, typing contexts, runtime environments, and so on. In the past, implementing and reasoning about programming languages required careful handling to maintain the correct behaviour of bound variables. Modern programming languages include features that enable constraints like scope safety to be expressed in types. Nevertheless, the programmer is still forced to write the same boilerplate over again for each new implementation of a scope-safe operation (e.g., renaming, substitution, desugaring, printing), and then again for correctness proofs. We present an expressive universe of syntaxes with binding and demonstrate how to (1) implement scope-safe traversals once and for all by generic programming; and (2) how to derive properties of these traversals by generic proving. Our universe description, generic traversals and proofs, and our examples have all been formalised in Agda and are available in the accompanying material available online at https://github.com/gallais/generic-syntax.

Cosmological inflationary studying around the type IV singularity within f(T) gravity

In this paper, we investigate the effects of Type IV singularity through [Formula: see text] gravity description of inflationary Universe, where [Formula: see text] denotes the torsion scalar. With the Friedmann equations of the theory, we reconstruct a [Formula: see text] model according to a given Hubble rate susceptible to describe the inflationary era near the Type IV singularity. One obtains an interesting well-known [Formula: see text] model but with additional constant parameter [Formula: see text] staying as the Type IV singularity contribution. Moreover, we calculate the Hubble flow parameters in order to determine the dynamical evolution of the cosmological system. The results show that some of the Hubble flow parameters are small near the Type IV singularity and become singular at Type IV singularity, indicating that a dynamical instability of the cosmological system occurs at that point. This means that the dynamical cosmological evolution up to that point ceases to be the final attractor since the system is abruptly interrupted. Furthermore, by considering the [Formula: see text] trace anomaly equation, the previous result on the Type IV singularity is consolidated by the conditional instability coming from the de Sitter inflationary description of the reconstructed [Formula: see text] model. The model leads to instability strongly governed by the Type IV singularity parameter [Formula: see text] is viewed as the graceful exit from inflation. Our theoretical [Formula: see text] description based on slow-roll parameters not only confirms some observational data on spectral index and the scalar-to-tensor ratio from Planck data and BICEP[Formula: see text]/Keck-Array data, but also shows the property of [Formula: see text] gravity in describing the early and late-time evolution of our Universe.

Religious ritual and sociopolitical ideologies: Circumcision costumes in the Turkish marketplace

Male circumcision is a widely practised Islamic ritual in Turkey regardless of families’ level of devotion. It is traditionally celebrated with a party where boys wear special ‘circumcision’ costumes. Concentrating on these costumes, this study examines the construction, interaction and intersection between religion, masculinity, nationalism, militarism and neo-Ottomanism, by investigating costumes available between 2014 and 2019 and exploring previous studies and archival resources on circumcision celebrations in the Ottoman and Turkish contexts, such as photographs and memoirs. By doing so, it identifies three main styles: classic, modern military and neo-Ottoman. Classic circumcision costumes emerged in the early twentieth century, while modern military style spread in the 1970s under the influence of the Turkish political sphere. The variety and availability of circumcision costumes has enormously increased since the 1990s due to the country’s economic upsurge. Under AKP rule, particularly in the 2010s, there has been a rise in Islam(ism) and neo-Ottomanism, which has been reflected and propagated through popular culture, particularly Ottoman-themed TV dramas. This has influenced the emergence and development of ‘neo-Ottoman’ circumcision costumes. Following the description of the stylistic universe of circumcision costumes, this article develops a semiotic square, which illustrates contradictions of ‘modernities’ and ‘modernity’, contrarieties of ‘historicity’ and ‘utopia’ and implications of ‘modernity’ and ‘tradition’ in each of the three styles.

On the quantum description of the early universe

Why is it interesting to try to understand the origin of the universe? Everything we observe today, including our existence, arose from that event. Although we still do not have a theory that allows us to describe the origin itself, the study of the very early era of the universe involves the ideal terrain to analyze the interface between two of today’s most successful physical theories, General Relativity and Quantum physics. But it is also an area in which we have a large number of observational data to test our theoretical ideas. Two of the fathers of Quantum physics, Niels Bohr and Werner Heisenberg, shared some thoughts that could be described with these words: Quantum physics tells us that there is a line between the observed and the observer, and therefore science should be limited to what is observed. We must give up a complete, objective and realistic theory of the world. This article will orbit around these ideas and summarizes how it is that today, from recent works, we are in a position to try to challenge them (at least in part) through cosmology, seeking the quantum description of the early universe.

Incompleteness of General Relativity Regarding Einstein's Program

The detection of gravitational waves substantiates the undeniable achievement of general relativity theory by increasing its theoretical and experimental accuracy. One century after predicting it has set again Einstein's works at the front of research. Absence of quantum particle associated to gravitation emphasizes that general relativity theory remains not included in the standard model of physics. Then Einstein’s disagreement about it incompleteness regarding wave-particle and matter-field becomes actualized. In order to circumvent these difficulties he privileged field, rather than matter for universe description in his program. In consequence a scalar field e(r0,t0) propagating at speed of light c yields matter from standing waves moving at speed strictly inferior to c, and interactions from progressive waves. Electromagnetic interactions derive from local variations of frequencies, and gravitation from local variations of speed of light. A space-like amplitude functions u0(k0r0) supplements fundamental time-like functions of classical and quantum mechanics. It tends toward Dirac’s distribution Delta (r0) in geometrical optics approximation conditions, when frequencies are infinitely high, and then hidden.
 
 More generally, it allows theoretical economies by deriving energy-momentum conservation laws, and least action law. Quantum domain corresponds to wave optics approximation conditions. Variations of frequencies give rise to an adiabatic constant, formally identical with Planck's constant, leading to first quantification for electromagnetic interactions and to second quantification for matter.

A type and scope safe universe of syntaxes with binding: their semantics and proofs

Almost every programming language’s syntax includes a notion of binder and corresponding bound occurrences, along with the accompanying notions of α-equivalence, capture avoiding substitution, typing contexts, runtime environments, and so on. In the past, implementing and reasoning about programming languages required careful handling to maintain the correct behaviour of bound variables. Modern programming languages include features that enable constraints like scope safety to be expressed in types. Nevertheless, the programmer is still forced to write the same boilerplate over again for each new implementation of a scope safe operation (e.g., renaming, substitution, desugaring, printing, etc.), and then again for correctness proofs. We present an expressive universe of syntaxes with binding and demonstrate how to (1) implement scope safe traversals once and for all by generic programming; and (2) how to derive properties of these traversals by generic proving. Our universe description, generic traversals and proofs, and our examples have all been formalised in Agda and are available in the accompanying material. NB. we recommend printing the paper in colour to benefit from syntax highlighting in code fragments.

Incompleteness of Standard Model regarding Einstein’s Program

The Standard Model of Particles gathers almost the whole present knowledge in theoretical physics, in a consistent system. It describes the universe as constituted fundamentally of particles, both for matter and for interactions. It is incomplete since it does not include gravitation with the three other interactions, and leans upon elementary particles such as electrons or quarks, which are considered as point-like with no known internal structure. The Einstein’s program offers means to circumvent these difficulties. It is founded upon a scalar field e (r0,t0) propagating at speed of light c, as a consistent system for universe description. Standing waves correspond to matter, which kinematical and dynamical properties are formally identical. Their space-like amplitude function u0(k0r0), supplements usual fundamental time-like equations of classical and quantum mechanics. In geometrical optics approximation conditions, when frequencies are infinitely high, and then hidden, u0(k0r0) yields Dirac’s distribution δ(r0), describing a particle as a singularity. The scalar field e(r0,t0) brings theoretical economy by yielding also the energy-momentum conservation laws, and the least action law, with determination of the Lagrangian.The frequency variations of the field e (r0,t0) are linked to electromagnetic interaction, constituted by progressive waves. Quantum domain corresponds to wave optics approximation conditions, with wave-particle duality. Adiabatic variations of frequencies, give rise to introduction of an adiabatic constant, formally identical with Planck's constant, with unification of first quantification for interactions and second quantification for matter. Local variations of speed of light yield gravitation interaction and General Relativity framework.

Cosmological Van Der Waals Model with Viscosity in an Inflationary Universe

The evolution of the Universe in the early (inflationary) stage of its development in the spatially flat Friedmann–Lemaitre–Robertson–Walker metric is considered. A theoretical model, described by a van der Waals fluid with the effect of bulk viscosity taken into account is investigated. A solution of the gravitation equation for the energy density is found and an analytical expression for the scale factor has been obtained. To verify the reliability of the cosmological model, the inflation parameters, the spectral index, and the scalartensor ratio were calculated. A comparison of these parameters with data obtained from observations of the Planck satellites is carried out. Conditions for the applicability of the van der Waals model with viscosity to the description of an inflationary Universe are obtained.

Trojan Horse cross section measurements and their impact on primordial nucleosynthesis

Big Bang Nucleosynthesis (BBN) nucleosynthesis requires several nuclear physics inputs and, among them, an important role is played by nuclear reaction rates. They are among the most important input for a quantitative description of the early Universe. An up-to-date compilation of direct cross sections of d(d,p)t, d(d,n)3He and 3He(d,p)4He reactions is given, being these ones among the most uncertain bare-nucleus cross sections.An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The result of these recent measurements is reviewed and compared with the available direct data. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN (0.01<T9 <10) and compared with up-to-date reaction rate compilations. Their value were therefore used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances of D, 3,4He and 7Li. These ones were then compared with the observational primordial abundance estimates in different astrophysical sites. A comparison was also performed with calculations using other reaction rates compilations available in literature.

Effective fluid description of the dark universe

We propose an effective anisotropic fluid description for a generic infrared-modified theory of gravity. In our framework, the additional component of the acceleration, commonly attributed to dark matter, is explained as a radial pressure generated by the reaction of the dark energy fluid to the presence of baryonic matter. Using quite general assumptions, and a microscopic description of the fluid in terms of a Bose–Einstein condensate of gravitons, we find the static, spherically symmetric solution for the metric in terms of the Misner–Sharp mass function and the fluid pressure. At galactic scales, we correctly reproduce the leading MOND-like log⁡(r) and subleading (1/r)log⁡(r) terms in the weak-field expansion of the potential. Our description also predicts a tiny (of order 10−6 for a typical spiral galaxy) Machian modification of the Newtonian potential at galactic scales, which is controlled by the cosmological acceleration.

Reappraisal of Polytypism in Layered Double Hydroxides: Consequences of Cation Ordering in the Metal Hydroxide Layer

Recent diffraction studies on layered double hydroxides have shown that the three-layer polytypes that were thought to crystallize in rhombohedral symmetry are actually one-layer polytypes of monoclinic symmetry. However, the prevailing Bookin and Drits (1993) scheme of polytypism, which is based on the widely accepted cation-disordered structure model, fails to predict the occurrence of low symmetry (monoclinic and orthorhombic) polytypes among the layered double hydroxides. In this work, a cation-ordered metal hydroxide layer (layer group p312/m or c12/m1) is chosen as the basic building block. Application of the structural synthon approach enables the description of the complete universe of polytypes comprising 1H, 1M1–7, 2H, 2O, 3R, 3H, 6H, and 6R among others (M: monoclinic; O: orthorhombic). These polytypes are characterized by their unique stacking vectors. The polytypes of large unit cell volume are obtained by a combination of two or more stacking vectors. This work has relevance to the understa...

Nonlinear electrodynamics and regular black holes

In this work, an exact regular black hole solution in General Relativity is presented. The source is a nonlinear electromagnetic field with the algebraic structure $$ T^{0}_{0}=T^{1}_{1} $$ for the energy–momentum tensor, partially satisfying the weak energy condition but not the strong energy condition. In the weak field limit, the EM field behaves like the Maxwell field. The solution corresponds to a charged black hole with $$q\le 0.77$$ $$\hbox {m}$$ . The metric, the curvature invariants, and the electric field are regular everywhere. The BH is stable against small perturbations of spacetime and using the Weinhold metric, geometrothermodynamical stability has been investigated. Finally we investigate the idea that the observable universe lives inside a regular black hole. We argue that this picture might provide a viable description of universe.

Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: Stability, ringdown, and gravitational-wave emission

Gravitational waves emitted by distorted black holes---such as those arising from the coalescence of two neutron stars or black holes---carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory, and {\bf(i)} find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations; {\bf(ii)} discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally {\bf(iii)} show that future ringdown detections with large signal-to-noise ratio would improve current constraints on the coupling parameter of the theory.