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Self-interacting Dark Matter
In astrophysics and particle physics, self-interacting dark matter (SIDM) is an alternative class of dark matter particles which have strong interactions, in contrast to the standard cold dark matter model (CDM). SIDM was postulated in 2000 as a solution to the core-cusp problem. In the simplest models of DM self-interactions, a Yukawa-type potential and a force carrier φ mediates between two dark matter particles. On galactic scales, DM self-interaction leads to energy and momentum exchange between DM particles. Over cosmological time scales this results in isothermal cores in the central region of dark matter haloes. If the self-interacting dark matter is in hydrostatic equilibrium, its pressure and density follow: :\nabla P_\chi/\rho_\chi = \nabla \Phi_ = \nabla (\Phi_\chi + \Phi_b) where \Phi_ and \Phi_ are the gravitational potential of the dark matter and a baryon respectively. The equation naturally correlates the dark matter distribution to that of the baryonic matter d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysics
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline said, Astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–''what'' they are, rather than ''where'' they are." Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, ''astrophysicists'' apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MACS J0025
MACS J0025.4-1222 is a galaxy cluster created by the collision of two galaxy clusters, and is part of the MAssive Cluster Survey (MACS). Like the earlier discovered Bullet Cluster, this cluster shows a clear separation between the centroid of the intergalactic gas (of majority of the normal, or baryonic, mass) and the colliding clusters. In the image, intergalactic gas is shown in pink and the mass centroids of the colliding clusters in blue, showing the separation of the two, similar to the Bullet Cluster. It provides independent, direct evidence for dark matter and supports the view that dark matter particles interact with each other only very weakly. Details The shown image is a composite of separate exposures made by Hubble Space Telescope ACS and WFPC2 detectors and the Chandra ACIS detector. The Hubble images were taken on November 5, 2006, and June 6, 2007. The visible light images from Hubble showed gravitational lensing which allowed astronomers to infer the distri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basic Books
Basic Books is a book publisher founded in 1950 and located in New York, now an imprint of Hachette Book Group. It publishes books in the fields of psychology, philosophy, economics, science, politics, sociology, current affairs, and history. History Basic Books originated as a small Greenwich Village-based book club marketed to psychoanalysts. Arthur Rosenthal took over the book club in 1950, and under his ownership it soon began producing original books, mostly in the behavioral sciences. Early successes included Ernest Jones's ''The Life and Work of Sigmund Freud'', as well as works by Claude Lévi-Strauss, Jean Piaget and Erik Erikson. Irving Kristol joined Basic Books in 1960, and helped Basic to expand into the social sciences. Harper & Row purchased the company in 1969. In 1997, HarperCollins announced that it would merge Basic Books into its trade publishing program, effectively closing the imprint and ending its publishing of serious academic books. That same year, B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambridge University Press
Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the oldest university press in the world. It is also the King's Printer. Cambridge University Press is a department of the University of Cambridge and is both an academic and educational publisher. It became part of Cambridge University Press & Assessment, following a merger with Cambridge Assessment in 2021. With a global sales presence, publishing hubs, and offices in more than 40 countries, it publishes over 50,000 titles by authors from over 100 countries. Its publishing includes more than 380 academic journals, monographs, reference works, school and university textbooks, and English language teaching and learning publications. It also publishes Bibles, runs a bookshop in Cambridge, sells through Amazon, and has a conference venues business in Cambridge at the Pitt Building and the Sir Geoffrey Cass Sports and Social Centre. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda-CDM Model
The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parameterization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda (Greek Λ) associated with dark energy; second, the postulated cold dark matter (abbreviated CDM); and third, ordinary matter. It is frequently referred to as the ''standard model'' of Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos: * the existence and structure of the cosmic microwave background * the large-scale structure in the distribution of galaxies * the observed abundances of hydrogen (including deuterium), helium, and lithium * the accelerating expansion of the universe observed in the light from distant galaxies and supernovae The model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a conco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strongly Interacting Massive Particle
Strongly interacting massive particles (SIMPs) are hypothetical particles that interact strongly between themselves and weakly with ordinary matter, but could form the inferred dark matter despite this. Strongly interacting massive particles have been proposed as a solution for the ultra-high-energy cosmic-ray problem and the absence of cooling flows in galactic clusters. Various experiments and observations have set constraints on SIMP dark matter from 1990 onward. . SIMP annihilations would produce significant heat. DAMA set limits with NaI(Tl) crystals. Measurements of Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...'s heat excess exclude SIMPs from 150 MeV to 104 GeV. Earth's heat flow significantly constrains any cross section. See also * * * Refere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abell 3827
ESO 146-5 (ESO 146-IG 005) is the designation given to a giant interacting elliptical galaxy in the center of the Abell 3827 cluster. It is well noted due to its strong gravitational lensing effect, measurements of which show the galaxy to be one of the most massive in the known universe. Physical characteristics This interacting galaxy was found 1.4 billion light years away in the center of Abell 3827. A huge halo of stars is surrounding its interacting nuclei. It has immense gravity that holds the cluster together due to its mass. Its unusual shape has led to the conclusion that each one of the nuclei was formed from multiple collisions of smaller galaxies, and now the nuclei are merging to form a single huge elliptical galaxy. Gravitational lensing calculations appeared to show that there is a large dark matter mass lagging the top left nucleus, possibly explained by it being self-interacting dark matter. commentarThe Possible First Signs of Self-interacting Dark Matter/ref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ESO 146-5
ESO 146-5 (ESO 146-IG 005) is the designation given to a giant interacting elliptical galaxy in the center of the Abell 3827 cluster. It is well noted due to its strong gravitational lensing effect, measurements of which show the galaxy to be one of the most massive in the known universe. Physical characteristics This interacting galaxy was found 1.4 billion light years away in the center of Abell 3827. A huge halo of stars is surrounding its interacting nuclei. It has immense gravity that holds the cluster together due to its mass. Its unusual shape has led to the conclusion that each one of the nuclei was formed from multiple collisions of smaller galaxies, and now the nuclei are merging to form a single huge elliptical galaxy. Gravitational lensing calculations appeared to show that there is a large dark matter mass lagging the top left nucleus, possibly explained by it being self-interacting dark matter. commentarThe Possible First Signs of Self-interacting Dark Matter/ref> ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ScienceDaily
''Science Daily'' is an American website launched in 1995 that aggregates press releases and publishes lightly edited press releases (a practice called churnalism) about science, similar to Phys.org and EurekAlert!. The site was founded by married couple Dan and Michele Hogan in 1995; Dan Hogan formerly worked in the public affairs department of Jackson Laboratory The Jackson Laboratory (often abbreviated as JAX) is an independent, non-profit biomedical research institution which was founded by a eugenicist. It employs more than 3,000 employees in Bar Harbor, Maine; Sacramento, California; Farmington, ... writing press releases. The site makes money from selling advertisements. As of 2010, the site said that it had grown "from a two-person operation to a full-fledged news business with worldwide contributors". At the time, it was run out of the Hogans' home, had no reporters, and only reprinted press releases. In 2012, Quantcast ranked it at 614 with 2.6 million U.S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three generations of fermions, but ordinary matter is made only from the first fermion generation. The first generation consists of up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quarks cannot exist on their own but form hadrons. Hadrons that contain an odd number of quarks are called baryons and those that contain an even number are called mesons. Two baryons, the proton and the neutron, make up most of the mass of ordinary matter. Mesons are unstable and the longest-lived last for only a few hundredt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supermassive Black Holes
A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, not even light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way has a supermassive black hole in its Galactic Center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars. Two supermassive black holes have been directly imaged by the Event Horizon Telescope: the black hole in the giant elliptical galaxy Messier 87 and the black hole at the Milky Way’s center. Description Supermassive blac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it is the oldest continuously published magazine in the United States. ''Scientific American'' is owned by Springer Nature, which in turn is a subsidiary of Holtzbrinck Publishing Group. History ''Scientific American'' was founded by inventor and publisher Rufus Porter in 1845 as a four-page weekly newspaper. The first issue of the large format newspaper was released August 28, 1845. Throughout its early years, much emphasis was placed on reports of what was going on at the U.S. Patent Office. It also reported on a broad range of inventions including perpetual motion machines, an 1860 device for buoying vessels by Abraham Lincoln, and the universal joint which now can be found in nearly every automobile manufactured. Current issues includ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
