Problems Of Modern Cosmology Research Articles

Discovering strongly lensed quasar candidates with catalogue-based methods from DESI Legacy Surveys

Context. The Hubble tension, revealed by a ~5σ discrepancy between measurements of the Hubble-Lemaitre constant among observations of the early and local Universe, is one of the most significant problems in modern cosmology. In order to better understand the origin of this mismatch, independent techniques to measure H0, such as strong lensing time delays, are required. Notably, the sample size of such systems is key to minimising the statistical uncertainties and cosmic variance, which can be improved by exploring the datasets of large-scale sky surveys such as Dark Energy Spectroscopic Instrument (DESI). Aims. We identify possible strong lensing time-delay systems within DESI by selecting candidate multiply imaged lensed quasars from a catalogue of 24 440 816 candidate QSOs contained in the ninth data release of the DESI Legacy Imaging Surveys (DESI-LS). Methods. Using a friend-of-friends-like algorithm on spatial co-ordinates, our method generates an initial list of compact quasar groups. This list is subsequently filtered using a measure of the similarity of colours among a group’s members and the likelihood that they are quasars. A visual inspection finally selects candidate strong lensing systems based on the spatial configuration of the group members. Results. We identified 620 new candidate multiply imaged lensed quasars (101 grade-A, 214 grade-B, 305 grade-C). This number excludes 53 known spectroscopically confirmed systems and existing candidate systems identified in other similar catalogues. When available, these new candidates will be further checked by combining the spectroscopic and photometric data from DESI.

The Laws of Nature and the Problems of Modern Cosmology

The notion that nature is subject to laws is exciting from many different viewpoints. This paper is based on the context of modern cosmology. It will list the significant interdisciplinary implications generated by various aspects of the contemporary scientific discussion about the status of laws of nature, especially their dynamic nature. Recent work highlights how multiple aspects of the observed universe still lack explanation and that several problems of standard cosmology still form the object of debate. Considering these issues, several proposals have been made that entail a revision of the concept of the law of nature, according to which the nature of time and of the relation between causality and natural laws ought to be reconsidered using approaches or viewpoints which point to philosophical issues. We argue that Tim Maudlin’s concept of Fundamental Law of Temporal Evolution (FLOTE) and Nancy Cartwright’s notion of the nomological machine provide new insights and valuable tools that can be used in the analysis of the status of laws in the context of cosmology and of complex systems theory. The limits of the traditional approach to laws of nature and their mathematical formulation are highlighted in this context, as well as the fact that many of the ultimate properties of nature may turn out to be formally unpredictable or uncomputable.

Kant's approach to understanding space from the perspective of modern natural science

The logical-historical subtext of Kant's definition of space and time as pure forms of sensory knowledge is investigated. The author analyzes the thinker's revision of the concept of a priori, his assertion of the existence of a priori synthetic judgments that serve as the basis for the formulation of the problem of the possibility of a priori forms of sensuality. In the center of the consideration is Kant's correlation of the categories of substance and form, matter and form, spatial incongruence as justifications of transcendental aesthetics. Special emphasis is placed on the differentiation, even the opposition of the categories of matter and form, substance and form by the thinker. The main method is hermeneutical reinterpretation of Kant's legacy from the standpoint of achievements and problems of modern cosmology. The main conclusions of this study are: 1) The formulation of the problem of the human dimension of our Universe in Kant's philosophy, which echoes the anthropic principle widely discussed in physics and testifies to the enduring projective significance of the philosopher's creativity.2) In this regard, it is permissible to attribute a priori forms of sensuality to the innate features of the human body. The three-dimensionality of the form of human sensory perception in the models of eleven-dimensional space-time discussed in modern science determines the very fact of the possibility of its existence. 3) In Kantian philosophy, the question is not raised how the form is attached to the essence. The development of modern elementary particle physics and cosmology in geometrodynamic content has come close to this priority issue.

CARTAN DECOMPOSITION OF THE DE SITTER GROUP SO(1,4). QUATERNION EULER ANGLES

Over the last twenty years, the de Sitter and anti-de Sitter spaces of various dimensions have become the focus of all theoretical high-energy physics. This is primarily due to the correspondence between supergravity in the five-dimensional anti-de Sitter space and supersymmetric field theory in four dimensions. The anti-de Sitter space turned out to be the most suitable manifold, on which nonperturbative results were obtained in the theory of superstrings and on which the theory of higher spin fields is naturally built. In turn, de Sitter's space is closely connected with the problems of modern cosmology, being essentially the theoretical basis of inflationary cosmology. On the other hand, de Sitter space-time and quantum field theory on this manifold are the subject of intensive study, mainly in connection with the task of constructing a quantum theory of gravitation in curved spaces. The central issue in the study of fields in the de Sitter space is a detailed analysis of a homogeneous group to this space — the de Sitter group. It is necessary to classify and describe homogeneous spaces of the group SO (1,4) up to subgroups SO (1,3) (Lorentz group), SO (4) (maximal compact subgroup of the group SO (1,4)), and SU (2). This problem is considered by determining all homogeneous spaces of the form M = SO (1,4) / H, where H is a stationary subgroup. The elements of the group are represented as the product of one-parameter matrices, which allows you to clearly see the relevance with the Euler angles in the classical three-dimensional case.

Clustering dependence of Chandra COSMOS Legacy AGN on host galaxy properties

AbstractThe presence of a super massive BH in almost all galaxies in the Universe is an accepted paradigm in astronomy. How these BHs form and how they co-evolve with the host galaxy is one of the most intriguing unanswered problems in modern Cosmology and of extreme relevance to understand the issue of galaxy formation. Clustering measurements can powerfully test theoretical model predictions of BH triggering scenarios and put constraints on the typical environment where AGN live in, through the connection with their host dark matter halos. In this talk, I will present some recent results on the AGN clustering dependence on host galaxy properties, such as galaxy stellar mass, star formation rate and specific BH accretion rate, based on X-ray selected Chandra COSMOS Legacy Type 2 AGN. We found no significant AGN clustering dependence on galaxy stellar mass and specif BHAR for Type 2 COSMOS AGN at mean z ∼ 1.1, with a stellar - halo mass relation flatter than predicted for non active galaxies in the Mstar range probed by our sample. We also observed a negative clustering dependence on SFR, with AGN hosting halo mass increasing with decreasing SFR. Mock catalogs of active galaxies in hosting dark matter halos with logMh[Msun] > 12.5, matched to have the same X-ray luminosity, stellar mass and BHAR of COSMOS AGN predict the observed Mstar - Mh, BHAR - Mh and SFR-Mh relations, at z ∼ 1.

On the Phenomenology of an Accelerated Large-Scale Universe

In this review paper, several new results towards the explanation of the accelerated expansion of the large-scale universe is discussed. On the other hand, inflation is the early-time accelerated era and the universe is symmetric in the sense of accelerated expansion. The accelerated expansion of is one of the long standing problems in modern cosmology, and physics in general. There are several well defined approaches to solve this problem. One of them is an assumption concerning the existence of dark energy in recent universe. It is believed that dark energy is responsible for antigravity, while dark matter has gravitational nature and is responsible, in general, for structure formation. A different approach is an appropriate modification of general relativity including, for instance, f ( R ) and f ( T ) theories of gravity. On the other hand, attempts to build theories of quantum gravity and assumptions about existence of extra dimensions, possible variability of the gravitational constant and the speed of the light (among others), provide interesting modifications of general relativity applicable to problems of modern cosmology, too. In particular, here two groups of cosmological models are discussed. In the first group the problem of the accelerated expansion of large-scale universe is discussed involving a new idea, named the varying ghost dark energy. On the other hand, the second group contains cosmological models addressed to the same problem involving either new parameterizations of the equation of state parameter of dark energy (like varying polytropic gas), or nonlinear interactions between dark energy and dark matter. Moreover, for cosmological models involving varying ghost dark energy, massless particle creation in appropriate radiation dominated universe (when the background dynamics is due to general relativity) is demonstrated as well. Exploring the nature of the accelerated expansion of the large-scale universe involving generalized holographic dark energy model with a specific Nojiri-Odintsov cut-off is presented to finalize the paper.

Ultracompact Minihalos as Probes of Inflationary Cosmology.

Cosmological inflation generates primordial density perturbations on all scales, including those far too small to contribute to the cosmic microwave background. At these scales, isolated ultracompact minihalos of dark matter can form well before standard structure formation, if the perturbations have sufficient amplitude. Minihalos affect pulsar timing data and are potentially bright sources of gamma rays. The resulting constraints significantly extend the observable window of inflation in the presence of cold dark matter, coupling two of the key problems in modern cosmology.

Towards the theory of regular accelerating Universe in Riemann-Cartan space-time

The problems of modern cosmology and attempts of its solution are considered. The applying of gravitation theory in the Riemann-Cartan space-time as the most natural generalization of Einstein gravitation theory in order to solve the principal cosmological problems is discussed. The gravitation theory in the Riemann-Cartan space-time leading to the solution of the problem of cosmological singularity and dark energy problem is analyzed.

Physics Essay: Six Baseless and Irrational Problems in Modern Cosmology

<p class="1Body">Analyzes the Big Bang theory, recession of galaxies, Hubble's law, multi-dimensional space, curved space and black hole in modern cosmology and points out that these six theories are all baseless and irrational, contrary to classical science. Promotes the use of plain view of the universe - the materialist view of space–time-mass-energy to study the universe. The observations and understanding of the universe are very limited now. Cosmology should be realistic, not based on irrational models.</p>

Gravitational lensing of twisted electromagnetic waves

The recent research in the field of classical and quantum optics has allowed for establishing that an electromagnetic wave possesses not only energy and momentum but also angular momentum. The wave front of an electromagnetic wave having an angular momentumis twisted with respect to the direction of motion. In the present paper, using the model of seven-dimensional space-time developed by the author, the motion of twisted electromagnetic waves in gravitational fields is considered. It is shown that the existence of an angular momentum of an electromagnetic wave leads to smaller values of the gravitational redshift than at zero angular momentum. The motion of electromagnetic waves near a massive object is also considered. It is shown that the gravitational deflection angle of an electromagnetic wave with a nonzero angular momentum is larger than in the case of zero angular momentum. The author believes that this approach will allow for explaining the gravitational lensing using only baryonic matter and also provide a new look at some problems of modern cosmology.

Fluctuation-dissipation dynamics of cosmological scalar fields

We show that dissipative effects have a significant impact on the evolution of cosmological scalar fields, leading to friction, entropy production and field fluctuations. We explicitly compute the dissipation coefficient for different scalar fields within the Standard Model and some of its most widely considered extensions, in different parametric regimes. We describe the generic consequences of fluctuation-dissipation dynamics in the post-inflationary universe, focusing in particular on friction and particle production, and analyze in detail two important effects. Firstly, we show that dissipative friction delays the process of spontaneous symmetry breaking and may even damp the the motion of a Higgs field sufficiently to induce a late period of warm inflation. Along with dissipative entropy production, this may parametrically dilute the abundance of dangerous thermal relics. Secondly, we show that dissipation can generate the observed baryon asymmetry without symmetry restoration, and we develop in detail a model of dissipative leptogenesis. We further show that this generically leads to characteristic baryon isocurvature perturbations that can be tested with CMB observations. This work provides a fundamental framework to go beyond the leading thermal equilibrium semi-classical approximation in addressing fundamental problems in modern cosmology.

Zeldovich's legacy in the Discovery and Understanding of the Cosmic Web

AbstractModeling and understanding the structure of the universe is one the most interesting problems in modern cosmology. It is also an extremely difficult problem. Despite spectacular achievements in observations and computational capabilities at present there is no comprehensive theory of the structure formation. There are successful theoretical models however most of them rely on assumptions and various fits which are not fully physically justified. The Zeldovich Approximation is a rare exception. Suggested more than forty years ago it remains one of the most successful and profound analytic models of structure formation. Some of results stemmed from the Zeldovich Approximation will be briefly reviewed.

Gravitational lensing in WDM cosmologies: the cross-section for giant arcs

The nature of the dark sector of the Universe remains one of the outstanding problems in modern cosmology, with the search for new observational probes guiding the development of the next generation of observational facilities. Clues come from tension between the predictions from {\Lambda}CDM and observations of gravitationally lensed galaxies. Previous studies showed that galaxy clusters in the {\Lambda}CDM are not strong enough to reproduce the observed number of lensed arcs. This work aims to constrain the warm dark matter cosmologies by means of the lensing efficiency of galaxy clusters drawn from these alternative models. The lensing characteristics of two samples of simulated clusters in the warm dark matter ({\Lambda}WDM) and cold dark matter ({\Lambda}CDM) cosmologies have been studied. The results show that even though the CDM clusters are more centrally concentrated and contain more substructures, the WDM clusters have slightly higher lensing efficiency than their CDM counterparts. The key difference is that WDM clusters have more extended and more massive subhaloes than CDM analogues. These massive substructures significantly stretch the critical lines and caustics and hence they boost the lensing efficiency of the host halo. Despite the increase in the lensing efficiency due to the contribution of massive substructures in the WDM clusters, this is not enough to resolve the arc statistics problem.

Gravitation and Special Relativity

A mathematical derivation of Maxwell's equations for gravitation, based on a mathematical proof of Faraday's Law, is presented. The theory provides a linear, relativistic Lagrangian field theory of gravity in a weak field, and paves the way to a better understanding of the structure of the energy-momentum tensor in the Einstein Field Equations. Hence it is directly relevant to problems in modern cosmology. The derivation, independent of the perturbation theory of Einstein's equations, puts the gravitational and electromagnetic fields on an equal footing for weak fields, contrary to generally held views. The historical objections to a linear Lorentz invariant field theory of gravity are refuted for weak fields.

New Classes of Off-Diagonal Cosmological Solutions in Einstein Gravity

In this work, we apply the anholonomic deformation method for constructing new classes of anisotropic cosmological solutions in Einstein gravity and/or generalizations with nonholonomic variables. There are analyzed four types of, in general, inhomogeneous metrics, defined with respect to anholonomic frames and their main geometric properties. Such spacetimes contain as particular cases certain conformal and/or frame transforms of the well known Friedman-Robertson-Walker, Bianchi, Kasner and Godel universes and define a great variety of cosmological models with generic off-diagonal metrics, local anisotropy and inhomogeneity. It is shown that certain nonholonomic gravitational configurations may mimic de Sitter like inflation scenaria and different anisotropic modifications without satisfying any classical false-vacuum equation of state. Finally, we speculate on perspectives when such off-diagonal solutions can be related to dark energy and dark matter problems in modern cosmology.

Constraining Dark Energy and Cosmological Transition Redshift with Type Ia Supernovae

The property of dark energy and the physical reason for the acceleration of the present universe are two of the most difficult problems in modern cosmology. The dark energy contributes about two-thirds of the critical density of the present universe from the observations of type-Ia supernovae (SNe Ia) and anisotropy of cosmic microwave background (CMB). The SN Ia observations also suggest that the universe expanded from a deceleration to an acceleration phase at some redshift, implying the existence of a nearly uniform component of dark energy with negative pressure. We use the ``Gold'' sample containing 157 SNe Ia and two recent well-measured additions, SNe Ia 1994ae and 1998aq to explore the properties of dark energy and the transition redshift. For a flat universe with the cosmological constant, we measure Ω M = 0.28 −0.05 +0.04 , which is consistent with Riess et al. The transition redshift is z T = 0.60 −0.08 +0.06 . We also discuss several dark energy models that define w ( z ) of the parameterized equation of state of dark energy including one parameter and two parameters ( w ( z ) being the ratio of the pressure to energy density). Our calculations show that the accurately calculated transition redshift varies from z T = 0.29 −0.06 +0.07 to z T = 0.60 −0.08 +0.06 across these models. We also calculate the minimum redshift z c at which the current observations need the universe to accelerate.

The present and the future of the CMB anisotropy and polarization

In this paper we discuss briefly some new problems of modern cosmology which arose after the BOOMERANG and MAXIMA-1 successful missions. We focus on statistics of high peaks of the CMB anisotropy and discuss possible inner structure of such peaks in the future observational data of MAP and PLANCK missions. We have investigated geometrical and statistical properties of the CMB polarization around such isolated high peaks of anisotropy in the presence of a polarized pixel noise and point sources. The structure of polarization fields in the vicinity of singular points with zero polarization is very sensitive to the level of pixel noises and point sources in the CMB maps.

Problems of modern cosmology: how dominant is the vacuum?

It would be hard to find a cosmologist today who does not believe that the vast bulk of the Universe (95% or more) is hidden from our eyes. We review the evidence for this remarkable consensus, and for the latest proposal, that the mysterious dark matter consists of as many as four separate ingredients: baryons, massive neutrinos, new "exotic" dark matter particles, and vacuum energy, also known as the cosmological constant (lambda). Of these, only baryons fit within standard theoretical physics; the others, if their existence is confirmed, will mean rewriting textbooks. Fresh experimental evidence has recently appeared for and against all four components, so that the subject is in a state of turmoil and excitement. The past 3 years in particular have seen the fourth (vacuum) component come into new prominence, largely at the expense of the third (exotic dark matter). We conclude our review by exploring the possibility that the energy density of the vacuum is in fact so dominant as to leave little room for significant amounts of exotic dark matter.

Nonlinear dynamics of the large-scale structure in the universe

This paper briefly reviews the nonlinear gravitational dynamics in an expanding universe. The gravitational instability is believed to play a key role in the formation of the large-scale structure of the universe, amplifying primordial small-amplitude random density fluctuations of Gaussian type and then, at the nonlinear stage, transforming them into thin dense pancakes, filaments, and compact clumps of matter. Although there are evidences that the distribution of galaxies and the distribution of the underlying mass density are not quite the same, it is widely accepted that they become similar when smoothed with a window of a sufficiently large size. At present the formation of galaxies themselves is very poorly understood and is not discussed here. We discuss scales in the range roughly from 1 Mpc to 100 Mpc (≈ 3 × 10 24 - 3 × 10 26 cm). The lower limit is at least 50 times greater than the size of the luminous part of a large galaxy, and the upper limit is at least 30 times smaller than the size of the observed universe. The problem of the formation of the large-scale structure is one of the key problems in modern cosmology and has too many aspects to mention in a short paper. Instead I review only the nonlinear evolution of density inhomogeneities on scales in question, which occured relatively recently. The paper discusses mainly analytical and semianalytical methods used in examining the nonlinear gravitational dynamics of the large-scale structure, though many hints were found in N-body simulations which have played a very important role in confronting theoretical models with observations.

Philosophical Problems of Modern Cosmology

Philosophical Problems of Modern Cosmology