New Astronomy Reviews最新文献

{"title":"Challenges for ΛCDM: An update","authors":"L. Perivolaropoulos,&nbsp;F. Skara","doi":"10.1016/j.newar.2022.101659","DOIUrl":"10.1016/j.newar.2022.101659","url":null,"abstract":"<div><p>A number of challenges to the standard <span><math><mi>Λ</mi></math></span>CDM model have been emerging during the past few years as the accuracy of cosmological observations improves. In this review we discuss in a unified manner many existing signals in cosmological and astrophysical data that appear to be in some tension (<span><math><mrow><mn>2</mn><mi>σ</mi></mrow></math></span> or larger) with the standard <span><math><mi>Λ</mi></math></span><span>CDM model as specified by the Cosmological Principle, General Relativity and the Planck18 parameter values. In addition to the well-studied </span><span><math><mrow><mn>5</mn><mi>σ</mi></mrow></math></span> challenge of <span><math><mi>Λ</mi></math></span>CDM (the Hubble <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> tension) and other well known tensions (the growth tension, and the lensing amplitude <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>L</mi></mrow></msub></math></span> anomaly), we discuss a wide range of other less discussed less-standard signals which appear at a lower statistical significance level than the <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span><span> tension some of them known as ’curiosities’ in the data) which may also constitute hints towards new physics. For example such signals include cosmic dipoles (the fine structure constant </span><span><math><mi>α</mi></math></span><span><span>, velocity and quasar dipoles), CMB asymmetries, </span>BAO Ly</span><span><math><mi>α</mi></math></span><span><span> tension, age of the Universe issues, the Lithium problem, small scale curiosities like the core–cusp and missing satellite problems, quasars </span>Hubble diagram, oscillating short range gravity signals etc. The goal of this pedagogical review is to collectively present the current status (2022 update) of these signals and their level of significance, with emphasis on the Hubble tension and refer to recent resources where more details can be found for each signal. We also briefly discuss theoretical approaches that can potentially explain some of these signals.</span></p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"95 ","pages":"Article 101659"},"PeriodicalIF":6.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72391134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relativistic models for anisotropic compact stars: A review","authors":"Jitendra Kumar ,&nbsp;Puja Bharti","doi":"10.1016/j.newar.2022.101662","DOIUrl":"10.1016/j.newar.2022.101662","url":null,"abstract":"<div><p><span>The Einstein–Maxwell (or Einstein) system of field equations plays a substantial role in the modeling of compact stars. Although due to its non-linearity getting an exact solution for the system of field equations is a difficult task, the solutions of field equations have a long and rich history. It took a year for Karl Schwarzschild to obtain the first exact solution of Einstein’s field equations since general theory of relativity was published. The number of viable solutions has been growing since then. Many authors have adopted several methods to obtain the solution. Different models have been constructed for a variety of applications. To produce feasible models of compact stars, a considerable amount of effort has been applied in gaining an understanding of the properties of anisotropic matter. Theoretical study indicates that pressure within compact stars with extreme internal density and strong gravity is mostly anisotropic. Anisotropy was found sufficient for the study of compact stars with the dense nuclear matter. It is claimed that it is important to consider the pressure experienced to be anisotropic whenever relativistic fluids are involved. In this review article, we have discussed different ways of generating a </span>static<span> spherically symmetric anisotropic fluid model. The purpose of the article is to present a simple classification scheme for static and spherically symmetric anisotropic fluid solutions. The known solutions are reviewed and compartmentalized as per the proposed scheme so that we can illustrate general ideas about these solutions without being exhaustive.</span></p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"95 ","pages":"Article 101662"},"PeriodicalIF":6.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76793391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The IAU working definition of an exoplanet","authors":"A. Lecavelier des Etangs ,&nbsp;Jack J. Lissauer","doi":"10.1016/j.newar.2022.101641","DOIUrl":"10.1016/j.newar.2022.101641","url":null,"abstract":"<div><p><span>In antiquity, all of the enduring celestial bodies<span> that were seen to move relative to the background sky of stars were considered planets. During the Copernican revolution, this definition was altered to objects orbiting around the Sun, removing the Sun and Moon but adding the Earth to the list of known planets. The concept of planet is thus not simply a question of nature, origin, composition, mass or size, but historically a concept related to the motion of one body </span></span><em>around</em> the other, in a hierarchical configuration.</p><p>After discussion within the IAU Commission F2 “Exoplanets and the Solar System”, the criterion of the star-planet mass ratio has been introduced in the definition of the term “exoplanet”, thereby requiring the hierarchical structure seen in our Solar System for an object to be referred to as an exoplanet. Additionally, the planetary mass<span> objects orbiting brown dwarfs, provided they follow the mass ratio criterion, are now considered as exoplanets. Therefore, the current working definition of an exoplanet, as amended in August 2018 by IAU Commission F2 “Exoplanets and the Solar System”, reads as follows:</span></p><p><span><span><em>Objects with true masses below the limiting mass for thermonuclear fusion of </em><em>deuterium</em><em> (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars, brown dwarfs or </em></span><em>stellar remnants</em><em> and that have a mass ratio with the central object below the</em></span> <span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span>/<span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>5</mn></mrow></msub></math></span> <em>instability</em> (<span><math><mrow><mi>M</mi><mo>/</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>central</mi></mrow></msub><mo>&lt;</mo><mn>2</mn><mo>/</mo><mrow><mo>(</mo><mn>25</mn><mo>+</mo><msqrt><mrow><mn>621</mn></mrow></msqrt><mo>)</mo></mrow><mo>≈</mo><mn>1</mn><mo>/</mo><mn>25</mn></mrow></math></span>) <em>are “planets”, no matter how they formed.</em></p><p><em>The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System, which is a mass sufficient both for self-gravity to overcome rigid body forces and for clearing the neighborhood around the object’s orbit.</em></p><p>Here we discuss the history and the rationale behind this definition.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"94 ","pages":"Article 101641"},"PeriodicalIF":6.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76586794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Black holes at cosmic dawn in the redshifted 21cm signal of HI","authors":"I.F. Mirabel ,&nbsp;L.F. Rodríguez","doi":"10.1016/j.newar.2022.101642","DOIUrl":"10.1016/j.newar.2022.101642","url":null,"abstract":"<div><p>The first stars (Pop III stars) and Black Holes (BHs) formed in galaxies at Cosmic Dawn (CD) have not been observed and remain poorly constrained. Theoretical models predict that indirect insights of those Pop III stars and BHs could be imprinted as an absorption signal in the 21cm line of the atomic hydrogen (HI) in the cold Intergalactic Medium (IGM), against the Cosmic Microwave Background (CMB), when the Universe was less than 200 million years old. The first tentative observation of an HI absorption in the 21cm line at redshifts z &gt; 15 by the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) has stimulated a great deal of research. To explain the additional large amplitude of that absorption signal a plethora of models based on exotic physics and on astrophysical sources have been proposed. Among the latter are models that propose the existence of an additional synchrotron Cosmic Radio Background (CRB) from BH-jet sources of comparable intensity to that of the CMB that boosts the HI absorption signal at CD. The discovery of radio loud supermassive black holes (SMBHs) of ~10⁹ M_⊙ in high-z quasars of up to z ~7.5 suggests the existence of a CRB component from growing BHs at z &gt; 15, of unknown intensity.</p><p>To match the onset of the EDGES signal a CRB of comparable intensity to that of the CMB would be required. With no judgment on whether the EDGES signal is of cosmic origin or not, here we provide approximate calculations to analyze highly redshifted HI absorption signals taking that of EDGES as an example to explore what could be learned on BHs at CD. Assuming a BH mass to radio luminosity ratio as observed in radio-loud Supermassive BHs (SMBHs) of ∼10⁹ M_⊙ in quasars at redshifts z = 6 – 7, by simple calculations we find that rapidly growing radio luminous BHs of Intermediate Mass (IMBHs) , in their way to become SMBHs, are the only type of astrophysical radio sources of a CRB that can explain the onset of the EDGES absorption at z = 18 – 20. At those redshifts the EDGES signal would imply that the global mass density of IMBHs must be dominant over that of stars, more than 70% of the maximum of Stellar Mass Density (SMD) expected at those high redshifts. This suggests that those IMBHs are formed before, and growing faster than the bulk of stars, with no need of a large mass contribution from stellar-mass BH remnants of typical Pop III stars. The highly redshifted signals from these IMBHs at cosmic dawn may be detected at long radio wavelengths with the next generation of ultrasensitive interferometers such as the Square Kilometer Array (SKA), in the infrared with the James Webb Space Telescope (JWST), and in the X-rays with future space missions.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"94 ","pages":"Article 101642"},"PeriodicalIF":6.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1387647322000021/pdfft?md5=f320818fe7143b82da599dcaeb650e1c&pid=1-s2.0-S1387647322000021-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78324150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The INTEGRAL view on black hole X-ray binaries","authors":"S.E. Motta ,&nbsp;J. Rodriguez ,&nbsp;E. Jourdain ,&nbsp;M. Del Santo ,&nbsp;G. Belanger ,&nbsp;F. Cangemi ,&nbsp;V. Grinberg ,&nbsp;J.J.E. Kajava ,&nbsp;E. Kuulkers ,&nbsp;J. Malzac ,&nbsp;K. Pottschmidt ,&nbsp;J.P. Roques ,&nbsp;C. Sánchez-Fernández ,&nbsp;J. Wilms","doi":"10.1016/j.newar.2021.101618","DOIUrl":"https://doi.org/10.1016/j.newar.2021.101618","url":null,"abstract":"<div><p><span><em>INTEGRAL</em></span> is an ESA mission in fundamental astrophysics that was launched in October 2002. It has been in orbit for over 18 years, during which it has been observing the high-energy sky with a set of instruments specifically designed to probe the emission from hard X-ray and soft <span><math><mi>γ</mi></math></span>-ray sources. This paper is devoted to the subject of black hole binaries, which are among the most important sources that populate the high-energy sky. We present a review of the scientific literature based on <em>INTEGRAL</em> data, which has significantly advanced our knowledge in the field of relativistic astrophysics. We briefly summarise the state-of-the-art of the study of black hole binaries, with a particular focus on the topics closer to the <em>INTEGRAL</em> science. We then give an overview of the results obtained by <em>INTEGRAL</em> and by other observatories on a number of sources of importance in the field. Finally, we review the main results obtained over the past 18 years on all the black hole binaries that <em>INTEGRAL</em> has observed. We conclude with a summary of the main contributions of <em>INTEGRAL</em> to the field, and on the future perspectives.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"93 ","pages":"Article 101618"},"PeriodicalIF":6.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.newar.2021.101618","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72276448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fifteen-plus years of INTEGRAL science","authors":"Edward P․J․ van den Heuvel ,&nbsp;Guillaume Bélanger ,&nbsp;Lorraine Hanlon ,&nbsp;Erik Kuulkers","doi":"10.1016/j.newar.2021.101633","DOIUrl":"https://doi.org/10.1016/j.newar.2021.101633","url":null,"abstract":"","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"93 ","pages":"Article 101633"},"PeriodicalIF":6.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72276903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Jets from young stars","authors":"T.P. Ray ,&nbsp;J. Ferreira","doi":"10.1016/j.newar.2021.101615","DOIUrl":"10.1016/j.newar.2021.101615","url":null,"abstract":"<div><p>Jets are ubiquitous in the Universe and are seen from a large number of astrophysical objects including active galactic nuclei, gamma ray bursters, micro-quasars, proto-planetary nebulae, young stars and even brown dwarfs. In every case they seem to be accompanied by an accretion disk and, while the detailed physics may change, it has been suggested that the same basic mechanism is responsible for generating the jet. Although we do not understand what that mechanism is, or even if it is universal, it is thought to involve the centrifugal ejection of matter from the disk along magnetic field lines. For a number of reasons, in particular their proximity and the abundant range of diagnostics to determine their characteristics, jets from young stars and their associated outflows may offer us the best opportunity to discover how jets are generated and the nature of the link between outflows and their accretion disks. Recently it has become clear that jets may be fundamental to the star formation process in removing angular momentum from the surrounding protoplanetary disk thereby allowing accretion to proceed. Moreover, with the realization that planetary formation begins much earlier than previously thought, jets may also help forge planets by determining initial environmental characteristics. This seems to be particularly true within the so-called terrestrial planet forming zone. Here we review observations of jets from young stars which have greatly benefitted from new facilities such as ALMA, space observatories like Spitzer, Herschel and HST, and radio facilities like LOFAR and the VLA. Interferometers such as CHARA and GRAVITY are starting to make inroads into resolving how they are launched, and we can look forward to a bright future in our understanding of this phenomenon when JWST and the SKA come on stream. In addition, we examine the various magnetohydrodynamic models for how jets from young stars are thought to be generated and how observations may help us select between these various options.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"93 ","pages":"Article 101615"},"PeriodicalIF":6.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.newar.2021.101615","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92495400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INTEGRAL reloaded: Spacecraft, instruments and ground system","authors":"Erik Kuulkers ,&nbsp;Carlo Ferrigno ,&nbsp;Peter Kretschmar ,&nbsp;Julia Alfonso-Garzón ,&nbsp;Marius Baab ,&nbsp;Angela Bazzano ,&nbsp;Guillaume Bélanger ,&nbsp;Ian Benson ,&nbsp;Antony J. Bird ,&nbsp;Enrico Bozzo ,&nbsp;Søren Brandt ,&nbsp;Elliott Coe ,&nbsp;Isabel Caballero ,&nbsp;Floriane Cangemi ,&nbsp;Jérôme Chenevez ,&nbsp;Bradley Cenko ,&nbsp;Nebil Cinar ,&nbsp;Alexis Coleiro ,&nbsp;Stefano De Padova ,&nbsp;Roland Diehl ,&nbsp;Ugo Zannoni","doi":"10.1016/j.newar.2021.101629","DOIUrl":"https://doi.org/10.1016/j.newar.2021.101629","url":null,"abstract":"<div><p>The European Space Agency’s INTErnational Gamma-Ray Astrophysics Laboratory (ESA/INTEGRAL) was launched aboard a Proton-DM2 rocket on 17 October 2002 at 06:41 CEST, from Baikonur in Kazakhstan. Since then, INTEGRAL has been providing long, uninterrupted observations (up to about 47<!--> <!--> <!-->h, or 170<!--> <!--> <!-->ksec, per satellite orbit of 2.7 days) with a large field-of-view (FOV, fully coded: 100 deg<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>), millisecond time resolution, keV energy resolution, polarization measurements, as well as additional wavelength coverage at optical wavelengths. This is realized by two main instruments in the 15<!--> <!--> <!-->keV to 10<!--> <!--> <!-->MeV energy range, the spectrometer SPI (spectral resolution 3<!--> <!-->keV at 1.8<!--> <!--> <!-->MeV) and the imager IBIS (angular resolution: 12<!--> <!-->arcmin FWHM), complemented by X-ray (JEM-X; 3–35<!--> <!--> <!-->keV) and optical (OMC; Johnson V-band) monitor instruments. All instruments are co-aligned to simultaneously observe the target region. A particle radiation monitor (IREM) measures charged particle fluxes near the spacecraft. The Anti-coincidence subsystems of the main instruments, built to reduce the background, are also very efficient all-sky <span><math><mi>γ</mi></math></span>-ray detectors, which provide virtually omni-directional monitoring above <span><math><mo>∼</mo></math></span>75<!--> <!--> <!-->keV. Besides the long, scheduled observations, INTEGRAL can rapidly (within a couple of hours) re-point and conduct Target of Opportunity (ToO) observations on a large variety of sources.</p><p>INTEGRAL observations and their scientific results have been building an impressive legacy: The discovery of currently more than 600 new high-energy sources; the first-ever direct detection of ⁵⁶Ni and ⁵⁶Co radio-active decay lines from a Type Ia supernova; spectroscopy of isotopes from galactic nucleo-synthesis sources; new insights on enigmatic positron annihilation in the Galactic bulge and disk; and pioneering gamma-ray polarization studies. INTEGRAL is also a successful actor in the new multi-messenger astronomy introduced by non-electromagnetic signals from gravitational waves and from neutrinos: INTEGRAL found the first prompt electromagnetic radiation in coincidence with a binary neutron star merger.</p><p>Up to now more than 1750 scientific papers based on INTEGRAL data have been published in refereed journals. In this paper, we will give a comprehensive update of the satellite status after more than 18 years of operations in a harsh space environment, and an account of the successful Ground Segment.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"93 ","pages":"Article 101629"},"PeriodicalIF":6.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.newar.2021.101629","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72276901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The episodic and multiscale Galactic Centre","authors":"Aaron Bryant,&nbsp;Alfred Krabbe","doi":"10.1016/j.newar.2021.101630","DOIUrl":"https://doi.org/10.1016/j.newar.2021.101630","url":null,"abstract":"<div><p>Within the central few hundred parsecs of the Milky Way, extending from longitude l = −1° to 1.5°, lies the Central Molecular Zone of the Galactic Centre. This extraordinary region is defined by a diverse variety of ISM features in numerous stages of evolution. Molecular cloud H₂ volume densities range from 10^3-8 cm⁻³ with an average of 10⁴ cm⁻³, two orders of magnitude above that of the galactic disk. The CMZ contains ∼3-5 × 10⁷ M_☉ of molecular gas, corresponding to around 5-10% of the content of the entire galaxy, and a similar fraction of its infrared luminosity. Gas temperatures, pressures and turbulent mach numbers are also significantly raised here, providing one of the more extreme environments for star formation within our observational reach.</p><p>We have hence been provided with a unique laboratory for probing the effects of these environments on the interplay between the ISM and star formation, and high resolution observations of both individual features and the large-scale structure of the CMZ can improve our understanding of the formation and evolution of this region, which we can then apply to similar regions in nearby galaxies.</p><p>This review will address historical and recent advancements in our observational and theoretical interpretations of the morphologies, dynamics and processes occurring in the ISM and massive stellar populations in the central few hundred parsecs. It will demonstrate how, across various spatial scales, episodic cycles of star formation, matter transport and feedback can be identified and potentially linked to observed features. The evolutionary states of molecular clouds, star forming regions and stellar clusters can be linked to their positions along orbits spanning the CMZ, and may be regulated by episodic processes such as material inflow or feedback. The concentric series of expanding bubbles and fronts visible in various electromagnetic bands can be related to echoes of past activity in the central cluster and Sgr A*. The ensemble of stellar ages and populations in the highly inhospitable environment of the central few parsecs points towards a series of accretion and starburst events.</p><p>The range of timescales and spatial scales involved in the aforementioned processes raises the possibility of a nested series of episodic cycles occurring concurrently, in which shorter timescale cycles regulate longer ones. The resulting complex and highly time-variable picture can help to explain many of the currently observed characteristics of the Galactic Centre, such as its deficient star forming efficiency, and can be applied to our understanding of the evolution of the galaxy as a whole.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"93 ","pages":"Article 101630"},"PeriodicalIF":6.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1387647321000178/pdfft?md5=b8d2d94d7b1da9b0989c58710ecba0ee&pid=1-s2.0-S1387647321000178-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72276449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Brief review of recent advances in understanding dark matter and dark energy","authors":"Eugene Oks","doi":"10.1016/j.newar.2021.101632","DOIUrl":"10.1016/j.newar.2021.101632","url":null,"abstract":"<div><p>Dark sector, constituting about 95% of the Universe, remains the subject of numerous studies. There are lots of models dealing with the cause of the effects assigned to “dark matter” and “dark energy”. This brief review is devoted to the <em>very recent</em><span><span><span> theoretical advances in these areas: only to the advances achieved in the last few years. For example, in section devoted to particle dark matter we overview recent publications on sterile neutrinos, self-interacting dark matter, dibarions (hexaquarks), dark matter from primordial “bubbles”, primordial black holes<span> as dark matter, axions escaping from neutron stars, and dark and usual matter interacting via the fifth dimension. We also overview the second flavor of hydrogen atoms: their existence was proven by analyzing atomic experiments and is also evidenced by the latest astrophysical observations of the 21 cm </span></span>spectral line<span> from the early Universe<span>. While discussing non-particle models of the cause of dark matter effects, we refer to modified Newtonian dynamics and modifications of the strong equivalence principles. We also consider exotic compact objects, primordial black holes, and retardation effects. Finally, we review recent studies on the cause of “dark energy effects”. Specifically, we cover two disputes that arose in 2019 and 2020 on whether the observations of </span></span></span>supernovas<span>, previously interpreted as the proof of the existence of dark energy, could have alternative explanations. Besides, we note a study of 2021, where dark energy is substituted by a new hypothetical type of dark matter having a magnetic-type interaction. We also refer to the recent model of a system of nonrelativistic neutral gravitating particles providing an alternative explanation of the entire dynamics of the Universe expansion – without introducing dark energy or new gravitational degrees of freedom.</span></span></p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"93 ","pages":"Article 101632"},"PeriodicalIF":6.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90769335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}