LamarkNewAge
Member Posts: 2497 Joined: 12-22-2015
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Message 1 of 2 (917899)
04-19-2024 3:33 PM
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Bother the Dark Energy Spectroscopic Instrument (DESI) and Dark Energy Survey observation results were releases this year, in April and January, respectively. Whether our Universe is Flat, Open, or Closed (Closed=Big Crunch), is up for debate. The Multiverse theory prefers and/or requires an infinite universe, for one thing. Everything I LINK will be new stuff. This will be my only old journal link
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Is the Lopsided Universe an Open Universe?
Marc Kamionkowski
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
September 9, 2013• Physics 6, 98
The recently confirmed sky-wide asymmetry in the cosmic microwave background might be explained by assuming the Universe is slightly curved just beyond the cosmic horizon. The density of matter and energy appears to vary more strongly on one side of the sky versus the other. That surprising assessment is based on corroborating evidence from two recent in-depth studies of the cosmic microwave background (CMB)—the thermal radiation left over from the big bang. To explain this hemispheric asymmetry, previous models [1] assumed the distribution of matter/energy fluctuations behaves differently beyond a particular distance scale, which is just a bit larger than the size of the observable Universe. However, the origin of this fundamental distance scale was left unexplained. Now, Andrew Liddle and Marina Cortês of the University of Edinburgh, UK, postulate [2] that this distance scale may represent the radius of curvature in a negatively curved (or “open”) Universe. In Physical Review Letters, the researchers show how a curvature-induced asymmetry can arise naturally if the Universe is open and was born via a process called bubble nucleation. Cosmologists have learned much about our Universe from using the CMB as a cosmic temperature gauge. The spatial fluctuations in the microwave signal provide a window into the primordial density fluctuations that seeded galaxies and other cosmic structures. These fluctuations have been measured with exquisite precision by two recent space missions: the Planck satellite [3] and the Wilkinson Microwave Anisotropy Probe (WMAP) [4]. The data have confirmed many of the predictions of inflation, a hypothesized period of accelerated expansion occurring a tiny fraction of a second after the big bang. But some discrepancies, or “anomalies,” remain. In particular, the prediction of statistical homogeneity—the similarity of the distribution of primordial density fluctuations everywhere in space—has been called into question by the CMB measurements. Both the Planck Collaboration and the WMAP team have reported a difference in these fluctuations on two opposing hemispheres of the sky, roughly divided along the ecliptic plane (the plane defined by the orbit of the Earth around the Sun). The average temperature is the same in both hemispheres, but the variance (or spread) is roughly 10%
larger on one side of the sky compared to the other when the data are divided into patches that are 3∘
wide or larger (see Fig. 1, top). Before proceeding, it should be mentioned that the statistical significance of the result is still under debate. While the asymmetry is significant at the ≳3σ
level, some question whether it is simply a consequence of the “look-elsewhere” effect: i.e., we test for all kinds of anomalies in the CMB, and the investigated parameter space is so vast that it’s no surprise that, by chance, one of the parameters shows a positive result. Cosmological models make statistical predictions about the distribution of temperature fluctuations on an ensemble of CMB skies, but we have only one CMB sky to observe. Therefore, if the observed asymmetry is a statistical fluke, we are stuck with it because there is no way to increase the statistics on this particular measurement. But if the asymmetry is real and not just a statistical fluke, then it is extremely important. It may well be a remnant of the preinflationary Universe! Physics - Is the Lopsided Universe an Open Universe?
Data is coming in other areas: The Dark Energy Spectroscopic Instrument (DESI) just released results this month. Popular Mechanics urges us to consider our fortunate timing.
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A New Study Says We May Be Living in a Variable Universe
Dark energy's grip on the cosmos could be more fickle than scientists once believed. BY DARREN ORFPUBLISHED: APR 18, 2024 6:30 AM EST .... And now, a new cosmological map developed by the Dark Energy Spectroscopic Instrument (DESI) is creating a few more. DESI—outfitted at Kitt Peak National Observatory in Tucson, Arizona—just commenced a five-year effort to make the most detailed map of the known universe, including 40 million galaxies stretched across 11 billion years. .... “We do see, indeed, [see] a hint that the properties of dark energy would not correspond to a simple cosmological constant,” astrophysicist at the Lawrence Berkeley lab Palanque-Delabrouille told The New York Times. “And this is the first time we have that…[but] I wouldn’t call it evidence yet. It’s too, too weak.” This new data comes at an important time for cosmology’s investigations into the underpinning of everything—and it’s also not the cosmological model’s only competitor. This week, a meeting at London’s Royal Society will question this standard view, with astronomers bringing evidence of the universe’s “lopsidedness” along with groundbreaking (and perplexing) data from the James Webb Space Telescope. All of this comes in preparation for large sky surveys scheduled to come online in the next couple years, including the Vera C. Rubin Observatory and Nancy Grace Roman Space Telescope. A New Study Says We May Be Living in a Variable Universe
Here was the event calenar Challenging the standard cosmological model | Royal Society
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World’s top cosmologists convene to question conventional view of the universe | Space | The Guardian Sun 14 Apr 2024 08.47 EDT World’s top cosmologists convene to question conventional view of the universe
Meeting at London’s Royal Society will scrutinise basic model first formulated in 1922 that universe is a vast, even expanse with no notable features
....
The conference brings together some of the scientists behind the recent anomalous findings. These include observations that suggest the universe is expanding more quickly in some regions than others, hints at megastructures in the night sky and evidence for cosmic flows – vast celestial rivers of material on a scale that cannot be readily accommodated within conventional theories. Dr Nathan Secrest, of the US Naval Observatory and a collaborator with Sarkar, is presenting findings that raise the possibility that the universe is slightly lopsided. After analysing a catalogue of more than 1m quasars (extremely luminous galactic cores), the team found that one hemisphere of the sky appeared to host roughly 0.5% more sources than the other. It may not sound like a major discrepancy but, according to Sarkar, if confirmed it would undermine the basis for dark energy, which is supposed to be the dominant component of the universe. “It would mean that two-thirds of the universe has just disappeared,” Sarkar said. Dr Konstantinos Migkas, of Leiden University, will share findings that the Hubble constant – the rate at which the universe is expanding – appears to vary across space. “Our results add another problematic piece to the puzzle,” Migkas said. At a local scale, at least, this suggests that observations do not match predictions of the standard model. “We can’t extrapolate that it’s wrong over the full universe,” he added. Alexia Lopez, a PhD student at the University of Central Lancashire, has discovered what appear to be cosmic megastructures, named Big Ring and Giant Arc. These shapes, traced out by galaxies and galaxy clusters, occur on a scale beyond which the universe should be smooth and effectively featureless. “When we’re finding a list of structures that are exceeding this scale, are they challenging this assumption that is so fundamental in cosmology?” said Lopez. “Maybe there needs to be more of a critical analysis of our standard model.” Sarkar suggests that belief in the standard model of cosmology has been so deeply ingrained that it is treated as “the religion”. “I find that frankly annoying that this principle hasn’t been checked,” he said, although not everyone agrees with this characterisation.
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Futurism
Top Astronomers Gather to Confront Possibility They Were Very Wrong About the Universe
Victor Tangermann
Mon, 15 April 2024 at 11:19 am GMT-5·2-min read A number of high-profile astronomers are set to convene at London's Royal Society to question some of the most fundamental aspects of our understanding of the universe. As The Guardian reports, the luminaries of cosmology will be re-examining some basic assumptions about the universe — right down to the over-a-century-old theory that it's expanding at a constant rate. .... "We have great data, but the theoretical basis is past its sell-by date," he added. "More and more people are saying the same thing and these are respected astronomers." Reality Check
A number of researchers have found evidence that the universe may be expanding more quickly in some areas compared to others, raising the tantalizing possibility that megastructures could be influencing the universe's growth in significant ways. Sarkar and his colleagues, for instance, are suggesting that the universe is "lopsided" after studying over a million quasars, which are the active nuclei of galaxies where gas and dust are being gobbled up by a supermassive black hole. The team found that one hemisphere actually hosted slightly more of these quasars, suggesting one area of the night sky was more massive than the other, undermining our conception of dark energy, a hypothetical form of energy used to explain why the universe is expanding at an accelerated rate. "It would mean that two-thirds of the universe has just disappeared," Sarkar told The Guardian. Other researchers have suggested that the cosmological constant, which has been used for decades as a way to denote the rate of the universe's expansion, actually varies across space, which would contradict the standard model of physics. In short, astronomers are more than ready to reevaluate the century-old footsteps they've been following to gain a better understanding of the universe around us. "I find that frankly annoying that this principle hasn’t been checked," Sarkar told the British newspaper. "We need more exploration on where, if at all, the standard model breaks down," Canadian-American astronomer and Carnegie Observatories director Wendy Freedman added. "I don’t think there is an obvious thing that is going to stand the test of time." Top Astronomers Gather to Confront Possibility They Were Very Wrong About the Universe
The Dark Energy evidence is causing some to question the cosmological principle, though the problem probably has more to do with different gravitational effects in areas of different densities. From the University of Oxford, Department of Physics
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'Lopsided' Universe could mean revision of standard cosmological model | University of Oxford Department of Physics 'Lopsided' Universe could mean revision of standard cosmological model
7 September 2022 Dr Sebastian von Hausegger and Professor Subir Sarkar from the Rudolf Peierls Centre for Theoretical Physics at Oxford, together with their collaborators Dr Nathan Secrest (US Naval Observatory, Washington), Dr Roya Mohayaee (Institut d’Astrophysique, Paris) and Dr Mohamed Rameez (Tata Institute of Fundamental Research, Mumbai), have made a surprising discovery about the Universe. Their paper is in press in Astrophysical Journal Letters. The researchers used observations of over a million quasars and half a million radio sources to test the ‘cosmological principle’ which underlies modern cosmology. It says that when averaged on large scales the Universe is isotropic and homogeneous. This allows a simple mathematical description of space-time – the Friedmann-Lemaître-Robertson-Walker (FLRW) metric – which enormously simplifies the application of Einstein’s general theory of relativity to the Universe as a whole, thus yielding the standard cosmological model. Interpretation of observational data in the framework of this model has however led to the astounding conclusion that about 70% of the Universe is in the form of a mysterious ‘dark energy’ which is causing its expansion rate to accelerate. This has been interpreted as arising from the zero-point fluctuations of the quantum vacuum, with the associated energy scale set by H0, the present rate of expansion of the universe. However, this is quite inexplicable in the successful Standard Model (quantum field theory) of fundamental interactions, the characteristic energy scale of which is higher by a factor of 1044. So, while the standard cosmological model (called ΛCDM) describes the observational data well, its main component, dark energy, has no physical basis. Testing foundational assumptions
This is what motivated the researchers to re-examine its underlying assumptions. Professor Sarkar says: ‘When the foundations of today’s standard cosmological model were laid a hundred years ago, there was no data. We didn’t even know then that we live in a galaxy – just one among a hundred billion others. Now that we do have data, we can, and should, test these foundational assumptions since a lot rests on them – in particular the inference that dark energy dominates the Universe.’ .... In fact, the Universe today is manifestly not homogeneous and isotropic. Astronomical surveys reveal a filamentary structure of galaxies, clusters of galaxies, and superclusters of clusters … and this ‘cosmic web’ extends to the deepest scales currently probed of about 2 billion light years. The conventional wisdom is that, while clumpy on small scales, the distribution of matter becomes homogeneous when averaged on scales larger than about 300 million light years. The Hubble expansion is smooth and isotropic on large scales, while on small scales the gravitational effect of inhomogeneities give rise to ‘peculiar’ velocities eg our nearest neighbour the Andromeda galaxy is not receding in the Hubble flow – rather it is falling towards us. Back in 1966, the cosmologist Dennis Sciama noted that because of this, the cosmic microwave background (CMB) radiation from the Big Bang could not be uniform on the sky. It must exhibit a ‘dipole anisotropy’ ieappear hotter in the direction of our local motion and colder in the opposite direction. This was indeed found soon afterwards and is attributed to our motion at about 370 km/s towards a particular direction (in the constellation of Crater). Accordingly, a special relativistic ‘boost’ is applied to all cosmological data (redshifts, apparent magnitudes etc) to transform them to the reference frame in which the universe is isotropic, since it is in this ‘cosmic rest frame’ that the Friedmann-Lemaître equations of the standard cosmological model hold. Application of these equations to the corrected data then indicates that the Hubble expansion rate is accelerating, as if driven by Einstein’s Cosmological Constant Λ, aka dark energy. The cosmological principle How can we check if this is true? If the dipole anisotropy in the CMB is due to our motion, then there must be a similar dipole in the sky distribution of all cosmologically distant sources. This is due to ‘aberration’ because of the finite speed of light – as was recognised by Oxford astronomer James Bradley in 1727, long before Einstein’s formulation of the special theory of relativity which predicts this effect. Such sources were first identified with radio telescopes; the relativist George Ellis and radio astronomer John Baldwin noted in 1984 that with a uniform sky map of at least a few hundred thousand such sources, this dipole could be measured and compared with the standard expectation. It was not however until this millennium that the first such data became available – the NRAO VLA Sky Survey (NVSS) catalogue of radio sources. The dipole amplitude turned out to be higher than expected, although its direction was consistent with that of the CMB. However, the uncertainties were large, so the significance of the discrepancy was not compelling. Two years ago, the present team of researchers upped the stakes by analysing a bigger catalogue of 1.4 million quasars mapped by NASA’s Wide-field Infrared Explorer (WISE). They found a similar discrepancy but at much higher significance. Dr von Hausegger comments: ‘If distant sources are not isotropic in the rest frame in which the CMB is isotropic, it implies a violation of the cosmological principle … which means going back to square one! So, we must now seek corroborating evidence to understand what causes this unexpected result.’ In their recent paper, the researchers have addressed this by performing a joint analysis of the NVSS and WISE catalogues after performing various detailed checks to demonstrate their suitability for the purpose. These catalogues are systematically independent and have almost no shared objects so this is equivalent to performing two independent experiments. The dipoles in the two catalogues, made at widely different wavelengths, are found to be consistent with each other. The consistency of the two dipoles improves upon boosting to the frame in which the CMB is isotropic (assuming its dipole to be kinematic in origin), which suggests that cosmologically distant radio galaxies and quasars may have an intrinsic anisotropy in this frame. The joint significance of the discrepancy between the rest frames of radiation and matter now exceeds 5σ (ie a probability of less than 1 in 3.5 million of being a fluke). ‘This issue can no longer be ignored,’ comments Professor Sarkar. ‘The validity of the FLRW metric itself is now in question!’ Potential paradigm-changing finding
New data with which to check this potentially paradigm-changing finding will soon come from the Legacy Survey of Space and Time (LSST) to be carried out at the Vera C Rubin Observatory in Chile. Oxford Physics is closely involved in this project, along with many other institutions in the UK and all over the world. Professor Ian Shipsey who has been a member of LSST since 2008, is excited about the prospect of carrying out fundamental cosmological tests. ‘As a particle physicist, I am acutely aware that the foundations of the Standard Model of particle physics are constantly under scrutiny. One of the reasons I joined LSST, and have worked for so long on it, is precisely to enable powerful tests of the foundations of the standard cosmological model,’ he says. To this end, Dr Hausegger and Professor Sarkar are leading projects in the LSST Dark Energy Science Collaboration to use the forthcoming data to test the homogeneity and isotropy of the Universe. ‘We will soon know if the standard cosmological model and the inference of dark energy are indeed valid,’ concludes Professor Sarkar. A challenge to the standard cosmological model, Secrest et al, Astrophysical Journal Letters, 937 (2022) L31
Also see:
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https://www.space.com/universe-expansion-rate-may-vary.html
The Universe
Surprise! The universe's expansion rate may vary from place to place
News
By Mike Wall published April 9, 2020 The new results challenge a core tenet of modern cosmology.
There are 25 comments the hot Space.com story above. It looks at the expansion rate being different in different parts of the universe. And what the implications are. It considers previously unconsidered gravitational clusters being responsible for different speeds of Dark Energy.
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Futurism
Our Universe Is Swallowing Baby Parallel Universes As It Expands, Scientists Suggest
Maggie Harrison Dupré
February 8, 2024·2 min read Our Universe Is Swallowing Baby Parallel Universes As It Expands, Scientists Suggest
Above is a fascinating look at Dark Energy issues and the multiverse. Our Universe might be Open, but an open universe is still infinite.
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