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In astronomy, dark matter is a hypothetical form of matter that appears not to interact with light or the electromagnetic field. Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be seen. Such effects occur in the context of formation and evolution of galaxies, gravitational lensing, the observable universe's current structure, mass position in galactic collisions, the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies.
In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a consequence of flavor and color combinations and antimatter, the fermions and bosons are known to have 48 and 13 variations, respectively. Among the 61 elementary particles embraced by the Standard Model number are electrons and other leptons, quarks, and the fundamental bosons. Subatomic particles such as protons or neutrons, which contain two or more elementary particles, are known as composite particles.
Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combination of protons and neutrons is called nuclear physics.
In cosmology, the cosmological constant, alternatively called Einstein's cosmological constant, is the constant coefficient of a term that Albert Einstein temporarily added to his field equations of general relativity. He later removed it; however, much later it was revived and reinterpreted as the energy density of space, or vacuum energy, that arises in quantum mechanics. It is closely associated with the concept of dark energy.
In physics, there are four observed fundamental interactions that form the basis of all known interactions in nature: gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Some speculative theories have proposed a fifth force to explain various anomalous observations that do not fit existing theories. The characteristics of this fifth force depend on the hypothesis being advanced. Many postulate a force roughly the strength of gravity with a range of anywhere from less than a millimeter to cosmological scales. Another proposal is a new weak force mediated by W′ and Z′ bosons.
The no-hair theorem states that all stationary black hole solutions of the Einstein–Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three independent externally observable classical parameters: mass, electric charge, and angular momentum. Other characteristics are uniquely determined by these three parameters, and all other information about the matter that formed a black hole or is falling into it "disappears" behind the black-hole event horizon and is therefore permanently inaccessible to external observers after the black hole "settles down". Physicist John Archibald Wheeler expressed this idea with the phrase "black holes have no hair", which was the origin of the name.
The CERN Axion Solar Telescope (CAST) is an experiment in astroparticle physics to search for axions originating from the Sun. The experiment, sited at CERN in Switzerland, was commissioned in 1999 and came online in 2002 with the first data-taking run starting in May 2003. The successful detection of solar axions would constitute a major discovery in particle physics, and would also open up a brand new window on the astrophysics of the solar core.
In particle physics, deep inelastic scattering is the name given to a process used to probe the insides of hadrons, using electrons, muons and neutrinos. It was first attempted in the 1960s and 1970s and provided the first convincing evidence of the reality of quarks, which up until that point had been considered by many to be a purely mathematical phenomenon. It is an extension of Rutherford scattering to much higher energies of the scattering particle and thus to much finer resolution of the components of the nuclei.
Jonathan Richard "John" Ellis is a British-Swiss theoretical physicist.
Astroparticle physics, also called particle astrophysics, is a branch of particle physics that studies elementary particles of astrophysical origin and their relation to astrophysics and cosmology. It is a relatively new field of research emerging at the intersection of particle physics, astronomy, astrophysics, detector physics, relativity, solid state physics, and cosmology. Partly motivated by the discovery of neutrino oscillation, the field has undergone rapid development, both theoretically and experimentally, since the early 2000s.
In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. Assuming that the lambda-CDM model of cosmology is correct, dark energy is the dominant component of the universe, contributing 68% of the total energy in the present-day observable universe while dark matter and ordinary (baryonic) matter contribute 26% and 5%, respectively, and other components such as neutrinos and photons are nearly negligible. Dark energy's density is very low: 7×10−30 g/cm3, much less than the density of ordinary matter or dark matter within galaxies. However, it dominates the universe's mass–energy content because it is uniform across space.
The chameleon is a hypothetical scalar particle that couples to matter more weakly than gravity, postulated as a dark energy candidate. Due to a non-linear self-interaction, it has a variable effective mass which is an increasing function of the ambient energy density—as a result, the range of the force mediated by the particle is predicted to be very small in regions of high density but much larger in low-density intergalactic regions: out in the cosmos chameleon models permit a range of up to several thousand parsecs. As a result of this variable mass, the hypothetical fifth force mediated by the chameleon is able to evade current constraints on equivalence principle violation derived from terrestrial experiments even if it couples to matter with a strength equal or greater than that of gravity. Although this property would allow the chameleon to drive the currently observed acceleration of the universe's expansion, it also makes it very difficult to test for experimentally.
In astrophysics and cosmology scalar field dark matter is a classical, minimally coupled, scalar field postulated to account for the inferred dark matter.
Amanda Weltman is a South African theoretical physicist. She is best known for co-authoring a series of papers proposing "chameleon gravity" to explain the existence of dark energy. She is currently a professor and South African Research Chair at the University of Cape Town.
Jennifer Anne Thomas,, is a British experimental particle physicist and professor at University College London. She has been a pioneer in the development of particle detectors, and the recipient of the Michael Faraday medal and prize in 2018 for her "outstanding investigations into the physics of neutrino oscillations".
Joanna Dunkley is a British astrophysicist and Professor of Physics at Princeton University. She works on the origin of the Universe and the Cosmic microwave background (CMB) using the Atacama Cosmology Telescope, the Simons Observatory and the Large Synoptic Survey Telescope (LSST).
Valerie Gibson, also known as Val Gibson, is an Emeritus Professor of Physics and former Head of the High Energy Physics group of the Cavendish Laboratory at the University of Cambridge.
Philippa K. Browning is a Professor of Astrophysics in the Jodrell Bank Centre for Astrophysics at the University of Manchester. She specialises in the mathematical modelling of fusion plasmas.
Beate Heinemann is a German particle physicist who has held positions at universities in Europe and the United States. She is the Director in charge of Particle Physics at the DESY laboratory in Hamburg and full professor of particle physics at the university of Hamburg.
The James Clerk Maxwell Medal and Prize is awarded by the Institute of Physics (IOP) in theoretical physics. The award is made "for exceptional early-career contributions to theoretical physics." It was awarded every two years between 1962 and 1970 and has since been awarded annually. It is named in honour of James Clerk Maxwell.
References
- 1 2 3 4 Physics, Institute of. "Award-winning early-career physicist is put in the spotlight". www.iop.org. Archived from the original on 2018-06-12. Retrieved 2018-06-12.
- 1 2 3 4 "Profile - Electromagnetic Zone". Electromagnetic Zone. Retrieved 2018-06-12.
- ↑ Burrage, Clare Joanna (2009). Scalar fields and the accelerated expansion of the universe. jisc.ac.uk (PhD thesis). University of Cambridge. OCLC 890152846. EThOS uk.bl.ethos.611090. Archived from the original on 2018-06-20. Retrieved 2018-06-20.
- ↑ "Dr. Clare Burrage - AcademiaNet". www.academia-net.org. Retrieved 2018-06-12.
- ↑ Merali, Zeeya (2009-05-29). "Dark-energy particle spotted?". Nature. doi:10.1038/news.2009.531. ISSN 0028-0836.
- ↑ "Members of the Group". www.desy.de. Retrieved 2018-06-12.
- ↑ Burrage, Clare; Davis, Anne-Christine; Shaw, Douglas J. (2009-05-21). "Active Galactic Nuclei Shed Light on Axion-like-Particles". Physical Review Letters. 102 (20): 201101. arXiv: 0902.2320 . Bibcode:2009PhRvL.102t1101B. doi:10.1103/PhysRevLett.102.201101. ISSN 0031-9007. PMID 19519013. S2CID 34372894.
- ↑ "Evidence mounts for axion-like particles – Physics World". Physics World. 2009-02-18. Retrieved 2018-06-12.
- 1 2 Physics, Institute of. "2015 Maxwell medal and prize". www.iop.org. Archived from the original on 2018-06-12. Retrieved 2018-06-12.
- ↑ "Clare Burrage". royalsociety.org. Retrieved 2018-06-12.
- ↑ "Clare Burrage". royalsociety.org. Retrieved 2018-06-12.
- ↑ "Searching for dark energy candidates using atom interferometry". Imperial College London. Retrieved 2018-06-12.
- ↑ "Dr Clare Burrage takes science to the dark side". Young Post | South China Morning Post. Retrieved 2018-06-12.
- ↑ "Science Alive 2016: Discover science in our daily lives | British Council". www.britishcouncil.hk. Retrieved 2018-06-12.
- ↑ Sixty Symbols (2015-02-13), Shining Light Through Walls - Sixty Symbols , retrieved 2018-06-12
- ↑ Sixty Symbols (2015-05-01), Chameleon Particles and Dark Energy - Sixty Symbols , retrieved 2018-06-12
- ↑ Butterworth, Jon (2015-02-15). "Dark Matter: an Axion to grind? | Jon Butterworth | Life & Physics". the Guardian. Retrieved 2018-06-12.
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