Block, SkipCaptcha, apieditor, Automoderated users, Bots, edit, ratelimit-exempt
58,183
edits
Changes
Spelling, Grammar, and General Cleanup, typos fixed: labor intensive → labor-intensive, 1930's → 1930s, well-known → well known
The differences between basic QM and Field Theory are these: in QM, the interactions between more than two particles are increasingly difficult to model, and the creation and destruction of particles cannot be modeled at all. In contrast, Field Theory can describe states containing arbitrary numbers of particles of different energies, masses, charges and types. Field Theory also provides an elegant framework for describing the interactions between particles, and the creation of new particles and destruction of old ones-- for example, the emission and absorption of photons by electrons, and vice versa.<ref>Bjorken and Drell. <i>Quantum Field Theory</i> Chapter 3; McGraw Hill Inc. (1980)</ref>
The differences between basic QM and Field Theory are these: in QM, the interactions between more than two particles are increasingly difficult to model, and the creation and destruction of particles cannot be modeled at all. In contrast, Field Theory can describe states containing arbitrary numbers of particles of different energies, masses, charges and types. Field Theory also provides an elegant framework for describing the interactions between particles, and the creation of new particles and destruction of old ones-- for example, the emission and absorption of photons by electrons, and vice versa.<ref>Bjorken and Drell. <i>Quantum Field Theory</i> Chapter 3; McGraw Hill Inc. (1980)</ref>
Like all physical theories since the mid-1930's, QFT is "Lorentz invariant". That is, it is consistent with [[Theory of Relativity|Special Relativity]]. However, as discussed below, it does not explain gravity in a manner consistent with the curvature of spacetime in General Relativity.
Like all physical theories since the mid-1930s, QFT is "Lorentz invariant". That is, it is consistent with [[Theory of Relativity|Special Relativity]]. However, as discussed below, it does not explain gravity in a manner consistent with the curvature of spacetime in General Relativity.
QFT bases the mathematical work on an assumption that elementary particles can be treated as "point-like objects of zero intrinsic size."<ref>http://theory.caltech.edu/people/jhs/strings/str114.html</ref>
QFT bases the mathematical work on an assumption that elementary particles can be treated as "point-like objects of zero intrinsic size."<ref>http://theory.caltech.edu/people/jhs/strings/str114.html</ref>
The electromagnetic force models interactions between electrically charged particles, and historically resulted from a unification of the electrical and magnetic fields, which were once thought to be separate fields.
The electromagnetic force models interactions between electrically charged particles, and historically resulted from a unification of the electrical and magnetic fields, which were once thought to be separate fields.
The weak nuclear force<ref>Chris Quigg. <i>Gauge Theories of the Strong, Weak, and Electromagnetic Interactions</i> Chapter 6; Benjamin/Cummings Co. (1983).</ref> is most well-known for mediating radioactive atomic decays, in which (for example) a proton in a nucleus will turn into a neutron (which remains in the nucleus), and a positron and neutrino, which are emitted. Non-nuclear particles such as electrons also participate in the weak force. Neutrinos only participate in the weak force, and have extremely low mass, making their observation very difficult. The weak nuclear force only exerts force when particles are extremely close together.
The weak nuclear force<ref>Chris Quigg. <i>Gauge Theories of the Strong, Weak, and Electromagnetic Interactions</i> Chapter 6; Benjamin/Cummings Co. (1983).</ref> is most well known for mediating radioactive atomic decays, in which (for example) a proton in a nucleus will turn into a neutron (which remains in the nucleus), and a positron and neutrino, which are emitted. Non-nuclear particles such as electrons also participate in the weak force. Neutrinos only participate in the weak force, and have extremely low mass, making their observation very difficult. The weak nuclear force only exerts force when particles are extremely close together.
The strong nuclear force holds together the protons and neutrons in an atomic nucleus, and the quarks within protons, neutrons, and mesons.<ref>Chris Quigg. <i>Gauge Theories of the Strong, Weak, and Electromagnetic Interactions</i> Chapter 8; Benjamin/Cummings Co. (1983).</ref> Because protons all have the same charge, they repel each other strongly, and the strong nuclear force is necessary to overcome this and hold them together in a nucleus; likewise for the quarks inside protons, neutrons and mesons. Unlike electromagnetism, which can extend over long distances, the strong nuclear force only exerts force when particles are extremely close together; but at close range, it is enormously stronger than electromagnetism.
The strong nuclear force holds together the protons and neutrons in an atomic nucleus, and the quarks within protons, neutrons, and mesons.<ref>Chris Quigg. <i>Gauge Theories of the Strong, Weak, and Electromagnetic Interactions</i> Chapter 8; Benjamin/Cummings Co. (1983).</ref> Because protons all have the same charge, they repel each other strongly, and the strong nuclear force is necessary to overcome this and hold them together in a nucleus; likewise for the quarks inside protons, neutrons and mesons. Unlike electromagnetism, which can extend over long distances, the strong nuclear force only exerts force when particles are extremely close together; but at close range, it is enormously stronger than electromagnetism.
Calculations involving field theory are universal throughout high-energy particle physics. Here we will briefly summarize a few more notable successes.
Calculations involving field theory are universal throughout high-energy particle physics. Here we will briefly summarize a few more notable successes.
As stated above, one the greatest achievements of QED is the very labor intensive, but extremely precise, calculation of the angular magnetic moment of the electron. In classical quantum mechanics, the magnetic moment of the electron, called <i>g</i>, should be exactly 2.0. The very small deviation from 2 is called the anomalous magnetic moment, and can be experimentally measured to extremely high precision. The very labor-intensive theoretical predictions<ref>G. Gabrielse, D. Hanneke, T. Kinoshita, M. Nio, and B. Odom, ''New Determination of the Fine Structure Constant from the Electron g Value and QED,'' Phys. Rev. Lett. 97, 030802 (2006), Erratum, Phys. Rev. Lett. 99, 039902 (2007).</ref> from QED match the experimental measurement to one part in a billion<ref>B. Odom, D. Hanneke, B. D'Urso, and G. Gabrielse, ''New Measurement of the Electron Magnetic Moment Using a One-Electron Quantum Cyclotron,'' Phys. Rev. Lett. 97, 030801 (2006).</ref>, a precision unparalleled in all of science. Also, the magnetic moment of the muon can be predicted to one part in a billion.
As stated above, one the greatest achievements of QED is the very labor-intensive, but extremely precise, calculation of the angular magnetic moment of the electron. In classical quantum mechanics, the magnetic moment of the electron, called <i>g</i>, should be exactly 2.0. The very small deviation from 2 is called the anomalous magnetic moment, and can be experimentally measured to extremely high precision. The very labor-intensive theoretical predictions<ref>G. Gabrielse, D. Hanneke, T. Kinoshita, M. Nio, and B. Odom, ''New Determination of the Fine Structure Constant from the Electron g Value and QED,'' Phys. Rev. Lett. 97, 030802 (2006), Erratum, Phys. Rev. Lett. 99, 039902 (2007).</ref> from QED match the experimental measurement to one part in a billion<ref>B. Odom, D. Hanneke, B. D'Urso, and G. Gabrielse, ''New Measurement of the Electron Magnetic Moment Using a One-Electron Quantum Cyclotron,'' Phys. Rev. Lett. 97, 030801 (2006).</ref>, a precision unparalleled in all of science. Also, the magnetic moment of the muon can be predicted to one part in a billion.
Also, as stated above, the Electroweak Theory, a unification of QED and weak force, predicted the existence and approximate mass of the Z boson before its observation.<ref>Chris Quigg. <i>Gauge Theories of the Strong, Weak, and Electromagnetic Interactions</i> Chapter 6; Benjamin/Cummings Co. (1983).</ref>
Also, as stated above, the Electroweak Theory, a unification of QED and weak force, predicted the existence and approximate mass of the Z boson before its observation.<ref>Chris Quigg. <i>Gauge Theories of the Strong, Weak, and Electromagnetic Interactions</i> Chapter 6; Benjamin/Cummings Co. (1983).</ref>