File Name: difference between dark matter and dark energy .zip
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Invisible dark matter makes up most of the universe — but we can only detect it from its gravitational effects. Galaxies in our universe seem to be achieving an impossible feat. They are rotating with such speed that the gravity generated by their observable matter could not possibly hold them together; they should have torn themselves apart long ago. The same is true of galaxies in clusters, which leads scientists to believe that something we cannot see is at work. They think something we have yet to detect directly is giving these galaxies extra mass, generating the extra gravity they need to stay intact.
We consider several cosmological models which allow for nongravitational direct couplings between dark matter and dark energy. The distinguishing cosmological features of these couplings can be probed by current cosmological observations, thus enabling us to place constraints on these specific interactions which are composed of the conformal and disformal coupling functions. We perform a global analysis in order to independently constrain the conformal, disformal, and mixed interactions between dark matter and dark energy by combining current data from: Planck observations of the cosmic microwave background radiation anisotropies, a combination of measurements of baryon acoustic oscillations, a supernova type Ia sample, a compilation of Hubble parameter measurements estimated from the cosmic chronometers approach, direct measurements of the expansion rate of the Universe today, and a compilation of growth of structure measurements. We find that in these coupled dark-energy models, the influence of the local value of the Hubble constant does not significantly alter the inferred constraints when we consider joint analyses that include all cosmological probes. Moreover, the parameter constraints are remarkably improved with the inclusion of the growth of structure data set measurements. We find no compelling evidence for an interaction within the dark sector of the Universe. COVID has impacted many institutions and organizations around the world, disrupting the progress of research.
Both the dark matter and dark energy issues are considered essential for a deeper understanding of the evolutionary universe. According to studies, dark matter and dark energy have had a strong influence on the structure and evolution of the universe. In addition, dark matter makes up almost twenty-seven percent of the universe, with the remaining five percent being baryonic matter. It is not known exactly what dark matter is, and in order to explain the missing mass of the universe it is commonly accepted that the study of dark energy and dark matter lies at the forefront of modern research and is considered of paramount importance for the development of 21 st century physics. The focus of this special issue is on questions regarding dark matter and dark energy and their relation to General Relativity and modified theories of gravity. In addition, we hope that the addressing of questions on basic open issues in these areas regarding, for example, the composition of dark matter or the way it is produced, and the true identity of dark energy, may provide some new answers, thereby expanding the acquired corpus of knowledge about dark matter and dark energy and yielding a better insight into their physics.
The visible universe — including Earth, the sun, other stars , and galaxies — is made of protons, neutrons, and electrons bundled together into atoms. Perhaps one of the most surprising discoveries of the 20th century was that this ordinary, or baryonic, matter makes up less than 5 percent of the mass of the universe. The rest of the universe appears to be made of a mysterious, invisible substance called dark matter 25 percent and a force that repels gravity known as dark energy 70 percent. Scientists have not yet observed dark matter directly.
The visible universe — including Earth, the sun, other stars , and galaxies — is made of protons, neutrons, and electrons bundled together into atoms. Perhaps one of the most surprising discoveries of the 20th century was that this ordinary, or baryonic, matter makes up less than 5 percent of the mass of the universe. The rest of the universe appears to be made of a mysterious, invisible substance called dark matter 25 percent and a force that repels gravity known as dark energy 70 percent. Scientists have not yet observed dark matter directly. It doesn't interact with baryonic matter and it's completely invisible to light and other forms of electromagnetic radiation, making dark matter impossible to detect with current instruments.
This creation of spacetime results in metric expansion around mass points in addition to the usual curvature due to stress-energy sources of the gravitational field. A recent modification of Einstein's theory of general relativity by Chadwick, Hodgkinson, and McDonald incorporating spacetime expansion around mass points, which accounts well for the observed galactic rotation curves, is adduced in support of the proposal. The hypothetical dark energy is invisible, and can be thought of as an intrinsic property of spacetime rather than usual matter stress-energy that is the source of spacetime curvature. An ostensibly separate phenomenon—the flattening of galactic rotation curves with radial distance—is also well known e. MOND has been successful in fitting the observed rotation curves, but it has the drawback of being an ad hoc alteration to the basic gravitational theory.
While some of these results have been noted previously, the strength here lies in that we do not assume a particular cosmological model. We incorporate Milky Way dark matter halo profile uncertainties, as well as an accounting of diffuse gamma-ray emission uncertainties in dark matter annihilation models for the Galactic Center Extended gamma-ray excess GCE detected by the Fermi Gamma Ray Space Telescope. The range of particle annihilation rate and masses expand when including these unknowns. However, empirical determinations of the Milky Way halo's local density and density profile leave the signal region to be in considerable tension with dark matter annihilation searches from combined dwarf galaxy analyses. The GCE and dwarf tension can be alleviated if: one, the halo is extremely concentrated or strongly contracted; two, the dark matter annihilation signal differentiates between dwarfs and the Galactic Center; or, three, local stellar density measures are found to be significantly lower, like that from recent stellar counts, pushing up the local dark matter density.
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Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained by accepted theories of gravity unless more matter is present than can be seen.Reply
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