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Topic: Fermion


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In the News (Sat 15 Dec 18)

  
 Fermion - Wikipedia, the free encyclopedia
Composite particles composed of fermions may be either fermions or bosons, depending on the number of fermionic constituents: Particles composed of an even number of fermions are themselves bosons (such as mesons); those composed of an odd number of fermions are themselves fermions (such as baryons).
The elementary particles that make up ordinary matter are fermions, belonging to either the quarks (which form protons and neutrons) or the leptons (such as electrons).
The Pauli exclusion principle of fermions is responsible for "rigidness" of ordinary matter and for the stability of the electron shells of atoms, making complex chemistry possible.
en.wikipedia.org /wiki/Fermion   (209 words)

  
 Fermion condensate - Wikipedia, the free encyclopedia
A chiral condensate (also called fermion condensate or quark condensate) is an order parameter for chiral symmetry breaking in a theory with massless fermions.
Since the Cooper pair has electric charge, this fermion condensate breaks the electromagnetic gauge symmetry of a superconductor, giving rise to the wonderful electromagnetic properties of such states.
A helium-3 atom is a fermion and at very low temperatures, they form two-atom Cooper pairs which are bosonic and condense into a superfluid.
en.wikipedia.org /wiki/Fermion_condensate   (342 words)

  
 Fermion Index
The Fermion Index calculated for each species is the sum of all fermion atomic isotopes in the mineral species' empirical formula.
The calculation of the fermion index is fairly straightforward, each element in the periodic table is generally composed of a mixture of isotopes.
For each element, the fermion index is the sum of all fermion atomic isotopes times the natural abundance.
webmineral.com /help/FermionIndex.shtml   (240 words)

  
 fermion concept from the Astronomy knowledge base   (Site not responding. Last check: 2007-10-22)
Fermions include the baryons, the leptons and their antiparticles, and obey the Pauli exclusion principle (cf.
Fermions obey the exclusion principle, which says that no two fermions can exist in an atom in the same quantum state; in practice this restricts the number of electrons, which are fermions, permitted in each electron shell.
Leptons include the electron family and the muon family., Elementary particle that does not participate in the strong interactions, including electrons, muons, and neutrinos., Elementary particle that have no measurable size and are not influenced by the strong nuclear force.
www.csi.uottawa.ca:4321 /astronomy/fermion.html   (597 words)

  
 Fermion   (Site not responding. Last check: 2007-10-22)
Theory proposes that all matter is composed of fundamental fermions, and that fermions obey the Pauli exclusion principle, which forbids more than one fermion from occupying the same quantum state.
Fermions are produced and annihilated in particle-antiparticle pairs.
The Fermi-Dirac distribution equation which is used to compute the average number of fermions in a particular energy state was developed in 1926 by the physicists Enrico Fermi and P.A.M. Dirac.
home.earthlink.net /~tdp/fermion.html   (224 words)

  
 Physics Newsletter: Spring00: Heavy fermion superconductivity   (Site not responding. Last check: 2007-10-22)
The term "heavy fermion" is used in condensed matter physics to describe metallic materials having very large electronic mass enhancement arising from an antiferromagnetic interaction between conduction electrons and local magnetic moments (d- or f-electron type) residing on a sublattice of atoms in the metal.
In the case of heavy fermion superconductivity, the idea that some sort of magnetic interaction may mediate pairing comes from pressure experiments.
There are a number of heavy fermion materials for which the low-temperature ground state is a magnetically ordered one.
www.physics.fsu.edu /PhysicsNewsletter/Spring00/Heavy.htm   (567 words)

  
 IRC#physics-maze#fermion   (Site not responding. Last check: 2007-10-22)
Fermions are quantum objects which have "half-integral" quantum spins - that is, spins of 1/2, or 3/2, or 5/2,...
Because of this, no two fermions can be in the same quantum state at the same time.
This is why the electrons in an atom fill up successively higher "rungs" on their "ladder" of energy levels.
www.moo.uklinux.net /kinsler/ircph/maze/fermion.html   (86 words)

  
 Composite Fermion
Composite fermions are a new class of fermions discovered in condensed matter physics.
A composite fermion is the bound state of an electron and an even number of quantized vortices (often thought of as an electron carrying an even number of magnetic flux quanta).
Composite fermions were originally predicted theoretically to explain the remarkable phenomenon of the "fractional quantum Hall effect" (FQHE), but are now known to describe a superstructure that encompasses other phenomena as well.
www.phys.psu.edu /~jain/cf.html   (619 words)

  
 EXPERIMENTAL PHYSICS: ON THE FERMION SUPERFLUID
Fermions are particles whose intrinsic angular momentum (or spin) is an odd multiple of h/2(pi), where (h) is the Planck constant.
The dramatically different thermodynamic properties of fermions and bosons at low temperature are a direct result of quantum statistical effects.
The fermions are arranged in the trap in a cloud with relatively large spatial distribution and large kinetic energy, which can be interpreted as being the result of an outward "Fermi pressure" (2,3).
scienceweek.com /2004/sa040924-6.htm   (1277 words)

  
 Fast Breaking Comment by M. Brian Maple
In the Ce- and U-based heavy fermion superconductors, the heavy fermion state and the superconductivity are both believed to be due to the interaction between the localized magnetic dipole moments of the Ce or U ions and the spins of the conduction electrons.
In a metal that exhibits heavy fermion behavior, the conduction electrons have effective masses that can be as large as several hundred times the mass of the free electron.
In the Ce- and U-based heavy fermion compounds, the heavy fermion state is believed to be associated with the Kondo effect wherein the magnetic dipole moments of the Ce- or U-ions are compensated by oppositely oriented spins of the conduction electrons, rendering the compound nonmagnetic at low temperatures.
www.esi-topics.com /fbp/2003/august03-MBrianMaple.html   (982 words)

  
 NIST/University of Colorado Scientists Create New Form of Matter: A Fermionic Condensate
This magnetic field coaxed the fermion atoms to match up into pairs, akin to the pairs of electrons that produce superconductivity, the phenomenon in which electricity flows with no resistance.
However, even if two fermions are not bound into one molecule, but merely move together in a correlated fashion, then as a pair they can act like a boson, and undergo condensation.
Instead, pairing of fermions is caused by the collective behavior of many atoms, similar to what causes “Cooper pairs” of electrons to form in a superconductor.
www.nist.gov /public_affairs/releases/fermi_condensate.htm   (1235 words)

  
 Physics News Update
BEC was first observed in 1995 for the case of bosonic rubidium atoms (at NIST/Colorado), lithium atoms (Rice Univ), and sodium atoms (MIT).
Meanwhile, fermion atoms (with half-integral overall spin) must avoid consorting with each other in any unified quantum state (a behavior enforced by the Pauli exclusion principle, which also dictates how electrons in atoms group into discrete shells---a grouping with implications for all chemical relationships).
Such Cooper pairing of fermion atoms (at work in bringing about the superfluid state in liquid helium-3) does not seem to have occurred yet in the present BEC experiments with gases.
www.aip.org /enews/physnews/2003/split/663-1.html   (435 words)

  
 Fermion Lie Algebras and Microscopic Theories of Nuclear Structure
Because of the algebraic structure of the theory, there is a rich set of symmetry limits in which analytical solutions to complex many-body problems may be obtained.
This method utilizes Lie algebras defined microscopically in the fermion degrees of freedom, and has been developed primarily by Cheng-Li Wu, Da Hsuan Feng, and myself, with important contributions from a number of other people.
It has been suggested that the similarities evident in the previous figure are one example of the effect of dynamical fermion symmetries in complex nuclei [gui93].
csep10.phys.utk.edu /guidry/Math-9-94html/math-root-save.html   (1724 words)

  
 Electron - Wikipedia, the free encyclopedia
This is a limitation described by the Heisenberg uncertainty principle, which, in this instance, simply states that the more accurately we know a particle's position, the less accurately we can know its momentum, and vice versa.
The electron has spin ½ and is a fermion (it obeys Fermi-Dirac statistics).
In addition to its intrinsic angular momentum, an electron has a magnetic moment along its spin axis.
en.wikipedia.org /wiki/Electron   (1686 words)

  
 Many-body wave function and fermion node - research L. Mitas   (Site not responding. Last check: 2007-10-22)
Note that the wave function fulfills the periodical boundary conditions as the infinite solid is represented by the periodically repeating supercell.
The fermion node represents a boundary condition in the so-called fixed-node quantum Monte Carlo methods which solve the Schrodinger equation by exploring the power and efficiency of a combination of analytical insights and stochastic techniques.
Although the fermion node is extremely complex, the stochastic methods can deal with these and other many-body effects very efficiently.
altair.physics.ncsu.edu /fnode.html   (296 words)

  
 MSN Encarta - Search Results - Fermion
Fermion, one of the two main classes of fundamental particles that make up matter and energy.
Fermions play an important role in the structure of...
Exclusively for MSN Encarta Premium Subscribers--quickly search thousands of articles from magazines such as Time, Newsweek, The Atlantic Monthly, and Smithsonian.
ca.encarta.msn.com /Fermion.html   (54 words)

  
 Fermion ~ The Bird   (Site not responding. Last check: 2007-10-22)
Fermion used to love to sit on the curtain header and watch over all the computers.
Fermion and the other Cockatiels live on their cages that sit on a large platform that goes across the room.
Boson loves Fermion and shares the top of the cages with her.
www.fermion.net /birds   (1474 words)

  
 fermion.html   (Site not responding. Last check: 2007-10-22)
The first heavy fermion superconductor, CeCu2Si2, was discovered in 1979.
Finally, two heavy fermion compounds, UPt3 and (U,Th)Be13, exhibit phase transitions within the superconducting state.
We have shown with heat capacity measurements that the defects reduce the transition temperatures in our heavy fermion samples by comparable amounts to previous work in high-temperature and other superconductors.
london.ucdavis.edu /~zieve/Research/heavy.html   (429 words)

  
 Boson-Fermion Condensates
Following is another chart with the total percentages of nuclear fermion/boson composition and whether the element has a fermionic or bosonic electron configuration.
Thus we see that all of the ORMUS elements except nickel have a significant percentage of fermionic isotopes and half of them have fermionic electron configurations.
Therefore, it seems likely that, at the very least, the odd numbered elements would have to be in diatomic (or larger) fermionic condensate configurations in order to exhibit the bosonic behaviors that may correlate to the strange abilities mentioned above.
www.subtleenergies.com /ormus/tw/boson.htm   (417 words)

  
 MAGNETISM IN HEAVY FERMION SYSTEMS
Magnetism in Heavy Fermion Systems is a review volume which covers an important subset of topics in the field of heavy fermion and non-Fermi liquid physics.
The topics covered include heavy fermion superconductivity, muon spin relaxation in small-moment heavy fermions, neutron scattering from heavy fermions, random localized magnetism in heavy fermions, and magnetism in Pr-containing cuprates.
One feature of the book which should be helpful to graduate students and new workers in the field is the extensive references and a separate list of review articles.
www.worldscibooks.com /physics/4460.html   (224 words)

  
 fermion
Fermions may be classified as leptons, such as the electron, and hadrons, such as the proton, neutron, mesons, and so on.
The exclusion principle, formulated by Austrian–US physicist Wolfgang Pauli in 1925, asserts that no two fermions in the same system (such as an atom) can possess the same position, energy state, spin, or other quantized property.
Helicon Publishing is a division of Research Machines plc.
www.tiscali.co.uk /reference/encyclopaedia/hutchinson/m0031906.html   (125 words)

  
 Fermion atoms jiggling together in an ultra-cold, jelly-like state of matter   (Site not responding. Last check: 2007-10-22)
Bosons are socially oriented and tend to stick together, while fermions are solitary entities, preferring to go it alone.
Fermionic superfluid gases — the atomic equivalent of superconducting electrons — might serve as rudimentary blueprints for creating superconductors that work at much higher temperatures.
What the team discovered was a jelly-like gas that wobbled for increasingly longer times as the temperature decreased -- the first direct signs of a fermion atom superfluid and the beginnings of a new model for exploring the possibility of extremely high- temperature superconductors.
www.azonano.com /news.asp?newsID=137   (1480 words)

  
 The Quantum Pontiff » My Fermion is a Boson
These two authors show that it is possible to convert any local fermion model into a local model with qubits (or qudits), i.e they effectively solve the problem of creating a Jordan-Wigner transform on higher dimensional lattices.
One of the points that Wen likes to raise from this work is the question of whether fermions are actually fundamental.
From what I understand, while there are examples of fermions arising from these local interacting boson modes, it is not known how to do this with chiral fermions.
dabacon.org /pontiff?p=1064   (989 words)

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