Cosmological Implications Research Articles

Quantifying the Tension between Cosmological Models and JWST Red Candidate Massive Galaxies

We develop a Python tool to estimate the tail distribution of the number of dark matter halos beyond a mass threshold and in a given volume in a light-cone. The code is based on the extended Press–Schechter model and is computationally efficient, typically taking a few seconds on a personal laptop for a given set of cosmological parameters. The high efficiency of the code allows a quick estimation of the tension between cosmological models and the red candidate massive galaxies released by the James Webb Space Telescope, as well as scanning the theory space with the Markov Chain Monte Carlo method. As an example application, we use the tool to study the cosmological implication of the candidate galaxies presented in Labbé et al. The standard Λ cold dark matter (ΛCDM) model is well consistent with the data if the star formation efficiency can reach ∼0.3 at high redshift. For a low star formation efficiency ϵ ∼ 0.1, the ΛCDM model is disfavored at ∼2σ–3σ confidence level.

Central Engine and Spectral Energy Distribution Properties of High Redshift Gamma Ray Blazars

We report on the properties of central engines in the γ-ray blazars located at high redshifts beyond z > 0.4, where the extra-galactic background light (EBL) starts affecting their γ-ray spectra. The physical engine that provides power to the blazars of very high bolometric luminosity is assumed to be a highly collimated jet of matter moving relativistically away from the supermassive black hole (SMBH), located in the central region of the host galaxy, in a direction aligned toward the Earth. Due to their peculiar geometry and special physical conditions, blazars at redshifts beyond z > 0.4 are bright enough to be detected in the γ-ray energy band. In this work, we investigate the physical properties of high-z γ-ray blazars detected by the Large Area Telescope (LAT) on board the Fermi satellite. We also study the properties of their emission regions and the central engines and discuss cosmological and astrophysical implications.

Using Pulsar Parameter Drifts to Detect Subnanohertz Gravitational Waves.

Gravitational waves with frequencies below 1nHz are notoriously difficult to detect. With periods exceeding current experimental lifetimes, they induce slow drifts in observables rather than periodic correlations. Observables with well-known intrinsic contributions provide a means to probe this regime. In this Letter, we demonstrate the viability of using observed pulsar timing parameters to discover such "ultralow" frequency gravitational waves, presenting two complementary observables for which the systematic shift induced by ultralow-frequency gravitational waves can be extracted. Using existing data for these parameters, we search the ultralow-frequency regime for continuous-wave signals, finding a sensitivity near the expected prediction from inspirals of supermassive black holes. We do not see an excess in the data, setting a limit on the strain of 1.3×10^{-12} at 450pHz with a sensitivity dropping approximately quadratically with frequency until 10pHz. Our search method opens a new frequency range for gravitational wave detection and has profound implications for astrophysics, cosmology, and particle physics.

Domesticating the Cosmic: Elemental Fire and the Tamil Festival of Lights

This article is about the calendrical, climactic and especially cosmological implications of Karthigai Deepam, an ancient Tamil celebration pivoted around the lighting of lamps that precedes Deepavali, the quintessential, ubiquitous but also comparatively recent festival of lights. Karthigai Deepam signals the end of the rains, intensifying winter chills and winds and shorter days. Juxtaposing festival observances in homes and those in temples, I demonstrate how its overriding concerns with generating light and warmth are part of ritual efforts to defend against elemental and existential threats of darkness and cold. Linking sacred time and mythical events with chronological time and human activities, this calendrical ritual joins together the divine and the mortal. Tracing the movement of fire and its various iterations as it traverses and connects the natural, cosmic, temple and home, this festival, I propose, renders the cosmic intimate and the intimate cosmic. Some rituals not only embody but also put cosmology into dynamic practice.

Stability of the de-Sitter spacetime. The anisotropic case

We elaborate on the cosmological implications of the recently established non-perturbative O(D,D)-symmetric approach. Following the α′-complete Friedmann equations, we provide a qualitative description of the dynamics of anisotropy perturbations. We find that the spacetime stability depends on the sign of the generalized dilaton time derivative. We consider isotropic limits and find possible mechanism for pre-big bang cosmology, governed by the value of cosmological constant.

Integrated microcavity electric field sensors using Pound-Drever-Hall detection

Discerning weak electric fields has important implications for cosmology, quantum technology, and identifying power system failures. Photonic integration of electric field sensors is highly desired for practical considerations and offers opportunities to improve performance by enhancing microwave and lightwave interactions. Here, we demonstrate a high-Q microcavity electric field sensor (MEFS) by leveraging the silicon chip-based thin film lithium niobate photonic integrated circuits. Using the Pound-Drever-Hall detection scheme, our MEFS achieves a detection sensitivity of 5.2 μV/(mHz\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{{{{{{{{\\rm{Hz}}}}}}}}}$$\\end{document}), which surpasses previous lithium niobate electro-optical electric field sensors by nearly two orders of magnitude, and is comparable to atom-based quantum sensing approaches. Furthermore, our MEFS has a bandwidth that can be up to three orders of magnitude broader than quantum sensing approaches and measures fast electric field amplitude and phase variations in real-time. The ultra-sensitive MEFSs represent a significant step towards building electric field sensing networks and broaden the application spectrum of integrated microcavities.

Qualitative behaviour of higher-curvature gravity with boundary terms i.e the f(Q) gravity models by dynamical system analysis

The higher-curvature gravity with boundary terms i.e the f(Q) theories, grounded on non-metricity as a fundamental geometric quantity, exhibit remarkable efficacy in portraying late-time universe phenomena. The aim is to delineate constraints on two prevalent models within this framework, namely the Log-square-root model and the Hyperbolic tangent-power model, by employing the framework of Big Bang Nucleosynthesis (BBN). The approach involves elucidating deviations induced by higher-curvature gravity with boundary terms in the freeze-out temperature (Tf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{f}$$\\end{document}) concerning its departure from the standard Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM evolution. Subsequently, constraints on pertinent model parameters are established by imposing limitations on |δTfTf|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\vert \\frac{\\delta T_{f}}{T_{f}}\\vert $$\\end{document} derived from observational bounds. This investigation employs dynamical system analysis, scrutinizing both background and perturbed equations. The study systematically explores the phase space of the models, identifying equilibrium points, evaluating their stability, and comprehending the system’s trajectory around each critical point. Moreover, the application of “Center Manifold Theory” facilitates the examination of stability properties at non-hyperbolic points. The principal findings of this analysis reveal the presence of a matter-dominated saddle point characterized by the appropriate matter perturbation growth rate. Subsequently, this phase transitions into a stable phase of a dark-energy-dominated, accelerating universe, marked by consistent matter perturbations. Overall, the study substantiates observational confrontations, affirming the potential of higher-curvature gravity with boundary terms as a promising alternative to the Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM concordance model. The methodological approach underscores the significance of dynamical systems as an independent means to validate and comprehend the cosmological implications of these theories.

Gauged global strings

We investigate the string solutions and cosmological implications of the gauge U(1)Z × global U(1)PQ model. With two hierarchical symmetry-breaking scales, the model exhibits three distinct string solutions: a conventional global string, a global string with a heavy core, and a gauge string as a bound state of the two global strings. This model reveals rich phenomenological implications in cosmology. During the evolution of the universe, these three types of strings can form a Y-junction configuration. Intriguingly, when incorporating this model with the QCD axion framework, the heavy-core global strings emit more axion particles compared to conventional axion cosmic strings due to their higher tension. This radiation significantly enhances the QCD axion dark matter abundance, thereby opening up the QCD axion mass window. Consequently, axions with masses exceeding ~ 10−5 eV have the potential to constitute the whole dark matter abundance. Furthermore, in contrast to conventional gauge strings, the gauge strings in this model exhibit a distinctive behavior by radiating axions.

A calculative cosmography: Geodesy and absolute space

Visual signifiers of absolute space such as grids, points, and straight lines are often identified with absolute space as a concept, to the extent that critiques of one are taken to apply to the other. This article argues that this is a misidentification that forecloses attention to meaningful dimensions of the coordinate grid while muddling the concept of absolute space. Attending to the geodetic science that gives rise to these visual signifiers shows that the space they are used to construct is entirely relational, and that the mythless rationalism with which they and absolute space are commonly associated can be productively questioned through attention to geodesy’s performative and cosmological implications. This raises the question of how we might better understand absolute space. The suggested answer is a cosmological claim that can be pursued and pictured but never realized. Absolute space is absolute as a sovereign can be: neither empirically nor visually, but as a motivating idea that presents itself as an explanation.

Shedding light on neutrino self-interactions with solar antineutrino searches

Solar antineutrinos are absent in the standard solar model prediction. Consequently, solar antineutrino searches emerge as a powerful tool to probe new physics capable of converting neutrinos into antineutrinos. In this study, we highlight that neutrino self-interactions, recently gaining considerable attention due to their cosmological and astrophysical implications, can lead to significant solar antineutrino production. We systematically explore various types of four-fermion effective operators and light scalar mediators for neutrino self-interactions. By estimating the energy spectra and event rates of solar antineutrinos at prospective neutrino detectors such as JUNO, Hyper-Kamiokande, and THEIA, we reveal that solar antineutrino searches can impose stringent constraints on neutrino self-interactions and probe the parameter space favored by the Hubble tension.

On CCGG, the De Donder‐Weyl Hamiltonian formulation of canonical gauge gravity

AbstractThis short paper gives a brief overview of the manifestly covariant canonical gauge gravity (CCGG) that is rooted in the De Donder‐Weyl Hamiltonian formulation of relativistic field theories, and the proven methodology of the canonical transformation theory. That framework derives, from a few basic physical and mathematical assumptions, equations describing generic matter and gravity dynamics with the spin connection emerging as a Yang Mills‐type gauge field. While the interaction of any matter field with spacetime is fixed just by the transformation property of that field, a concrete gravity ansatz is introduced by the choice of the free (kinetic) gravity Hamiltonian. The key elements of this approach are discussed and its implications for particle dynamics and cosmology are presented. New insights: Anomalous Pauli coupling of spinors to curvature and torsion of spacetime, spacetime with (A)dS ground state, inertia, torsion and geometrical vacuum energy, Zero‐energy balance of the Universe leading to a vanishing cosmological constant and torsional dark energy.

Exotic spin-dependent interactions through unparticle exchange

The potential discovery of unparticles could have far-reaching implications for particle physics and cosmology. For over a decade, high-energy physicists have extensively studied the effects of unparticles. In this study, we derive six types of nonrelativistic potentials between fermions induced by unparticle exchange in coordinate space. We consider all possible combinations of scalar, pseudo-scalar, vector, and axial-vector couplings to explore the full range of possibilities. Previous studies have only examined scalar-scalar (SS), pseudoscalar-pseudoscalar (PP), vector-vector (VV), and axial-axial-vector (AA) type interactions, which are all parity even. We propose SP and VA interactions to extend our understanding of unparticle physics, noting that parity conservation is not always guaranteed in modern physics. We explore the possibilities of detecting unparticles through the long-range interactions they may mediate with ordinary matter. Dedicated experiments using precision measurement methods can be employed to search for such interactions. We discuss the properties of these potentials and estimate constraints on their coupling constants based on existing experimental data. Our findings indicate that for some particular values of the scaling dimension dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document}, the coupling between scalar or vector unparticles and fermions is constrained by several orders of magnitude more tightly than the previous limits. The underlying reason for this improvement is analyzed. Limits are also set on the newly proposed SP and VA interactions for continuous dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document} values, allowing the exploration of the dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document} dependence of the constraints. It turns out that the bounds exhibit an exponential decay trend with the increasing dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document}.

Nonequilibrium Schwinger-Keldysh formalism for density matrix states: Analytic properties and implications in cosmology

Motivated by cosmological Hartle-Hawking and microcanonical density matrix prescriptions for the quantum state of the Universe we develop a Schwinger-Keldysh in-in formalism for generic nonequilibrium dynamical systems with the initial density matrix. We build the generating functional of in-in Green’s functions and expectation values for a generic density matrix of the Gaussian type and show that the requirement of particle interpretation selects a distinguished set of positive/negative frequency basis functions of the wave operator of the theory, which is determined by the density matrix parameters. Then we consider a special case of the density matrix determined by the Euclidean path integral of the theory, which in the cosmological context can be considered as a generalization of the no-boundary pure state to the case of the microcanonical ensemble, and show that in view of a special reflection symmetry its Wightman Green’s functions satisfy Kubo-Martin-Schwinger periodicity conditions which hold despite the nonequilibrium and nonstationary nature of the physical setup. Rich analyticity structure in the complex plane of the time variable reveals the combined Euclidean-Lorentzian evolution of the theory, which depending on the properties of the initial density matrix can be interpreted as a decay of a classically forbidden quantum state. Published by the American Physical Society 2024

Peter Strawson’s Descriptive Metaphysics and its Cosmological Implications

Peter Strawson’s Descriptive Metaphysics and its Cosmological Implications

Detection of Gravitational Waves with Semi Classical Features and Resulting Cosmological Implications

Detection of Gravitational Waves with Semi Classical Features and Resulting Cosmological Implications

Interacting dark energy: clarifying the cosmological implications and viability conditions

In this study, cosmological models are considered, where dark matter and dark energy are coupled and may exchange energy through non-gravitational interactions with one other. These interacting dark energy (IDE) models have previously been introduced to address problems with the standard ΛCDM model of cosmology (which include the coincidence problem, Hubble tension and S_8 discrepancy). However, conditions ensuring positive energy densities have often been overlooked. Assuming two different linear dark energy couplings, Q = δ H ρ_de and Q = δ H ρ_dm, we find that negative energy densities are inevitable if energy flows from dark matter to dark energy (iDMDE regime) and that consequently, we should only seriously consider models where energy flows from dark energy to dark matter (iDEDM regime). To additionally ensure that these models are free from early time instabilities, we need to require that dark energy is in the `phantom' (ω<-1) regime. This has the consequence that model Q=δ H ρ_dm will end with a future big rip singularity, while Q = δ H ρ_de may avoid this fate with the right choice of cosmological parameters.

Viscous effect in the late time evolution of phantom universe

We investigate the cosmological implications of a phantom dark energy model with bulk viscosity. We explore this model as a possible way to resolve the big rip singularity problem that plagues the phantom models. We use the latest type Ia supernova and Hubble parameter data to constrain the model parameters and find that the data favor a significant bulk viscosity over a non-constant potential term for the phantom field. We perform a dynamical analysis of the model and show that the only stable and physical attractor corresponds to a phantom-dominated era with a total equation of state that can be greater than -1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-1$$\\end{document} due to the viscosity. We also study the general effect of viscosity on the phantom field and the late time evolution of the universe. We apply the statefinder diagnostic to the model and find that it approaches a nearby fixed point asymptotically, indicating that the universe can escape the big rip singularity with the presence of bulk viscosity. We conclude that bulk viscosity can play an important role in affecting the late-time behavior as well as alleviating the singularity problem of the phantom universe.

Progenitor-age dependence of type Ia supernova luminosity and its cosmological implication

Progenitor-age dependence of type Ia supernova luminosity and its cosmological implication

Anisotropic power-law inflation for a generalized model of two scalar and two vector fields

Cosmological implication of a generalized model of two scalar and two vector fields, in which both scalar fields are non-minimally coupled to each vector field, is studied in this paper. In particular, we will seek a set of new anisotropic power-law inflationary solutions to this model. Additionally, the stability of the obtained solutions will be examined by using the dynamical system approach. As a result, we will show that this set of solutions turns out to be stable and attractive during the inflationary phase as expected due to the existence of the unusual couplings between two scalar and two vector fields. Notably, we will point out that the existence of phantom field will lead to an instability of the corresponding anisotropic power-law inflation.

Viscous exotic fluid interacting with dark matter and future infinite singularities

By making use of two viable Lagrangian [Formula: see text] models, we investigate the behavior of the state parameter of the interacting viscous dark energy. We, from constant deceleration parameter, explore the cosmological implications of the viscosity and interaction between the dark energy and dark matter in terms of redshift. We then construct the viscosity and the interaction parameters that are respectively parameterized by [Formula: see text] and [Formula: see text] and obtain interesting results. Later, we investigate the behavior of some bulk viscosity models describing little rip and pseudo rip future singularities within [Formula: see text] modified gravity. We obtain interesting gravitational equations of motion for viscous dark energy coupled with dark matter. The solution of these equations gives us an analytic expression for characteristic properties of these cosmological models.