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Doublet–triplet Splitting Problem
In particle physics, the doublet–triplet (splitting) problem is a problem of some Grand Unified Theories, such as SU(5), SO(10), and E_6. Grand unified theories predict Higgs bosons (doublets of SU(2)) arise from representations of the unified group that contain other states, in particular, states that are triplets of color. The primary problem with these color triplet Higgs is that they can mediate proton decay in supersymmetric theories that are only suppressed by two powers of GUT scale (i.e. they are dimension 5 supersymmetric operators). In addition to mediating proton decay, they alter gauge coupling unification. The doublet–triplet problem is the question 'what keeps the doublets light while the triplets are heavy?' Doublet–triplet splitting and the μ-problem In 'minimal' SU(5), the way one accomplishes doublet–triplet splitting is through a combination of interactions \int d^2\theta \; \lambda H_ \Sigma H_ + \mu H_ H_ where \Sigma is an adjoint of SU(5) and is ... [...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 hundredths of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroweak Interaction
In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of the same force. Above the unification energy, on the order of 246 GeV,The particular number 246 GeV is taken to be the vacuum expectation value v = (G_\text \sqrt)^ of the Higgs field (where G_\text is the Fermi coupling constant). they would merge into a single force. Thus, if the temperature is high enough – approximately 1015 K – then the electromagnetic force and weak force merge into a combined electroweak force. During the quark epoch (shortly after the Big Bang), the electroweak force split into the electromagnetic and weak force. It is thought that the required temperature of 1015 K has not been seen widely throughout the unive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frank Wilczek
Frank Anthony Wilczek (; born May 15, 1951) is an American theoretical physicist, mathematician and Nobel laureate. He is currently the Herman Feshbach Professor of Physics at the Massachusetts Institute of Technology (MIT), Founding Director of T. D. Lee Institute and Chief Scientist at the Wilczek Quantum Center, Shanghai Jiao Tong University (SJTU), distinguished professor at Arizona State University (ASU) and full professor at Stockholm University. Wilczek, along with David Gross and H. David Politzer, was awarded the Nobel Prize in Physics in 2004 "for the discovery of asymptotic freedom in the theory of the strong interaction". In May 2022, he was awarded the Templeton Prize for Progress Toward Research or Discoveries about Spiritual Realities. Early life and education Born in Mineola, New York, Wilczek is of Polish and Italian origin. His grandparents were immigrants, who "really did work with their hands", according to Wilczek, but Frank's father took night ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Savas Dimopoulos
Savas Dimopoulos (; el, Σάββας Δημόπουλος; born 1952) is a particle physicist at Stanford University. He worked at CERN from 1994 to 1997. Dimopoulos is well known for his work on constructing theories beyond the Standard Model. Life He was born an ethnic Greek in Istanbul, Turkey and later moved to Athens due to ethnic tensions in Turkey during the 1950s and 1960s. Education and career Dimopoulos studied as an undergraduate at the University of Houston. He went to the University of Chicago and studied under Yoichiro Nambu for his doctoral studies. After completing his Ph.D. in 1979, he briefly went to Columbia University before taking a faculty position at Stanford University in 1980. During 1981 and 1982 he was also affiliated with the University of Michigan, Harvard University and the University of California, Santa Barbara. From 1994 to 1997 he was on leave from Stanford University and was employed by CERN. Dimopoulos is well known for his work on construct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steven Weinberg
Steven Weinberg (; May 3, 1933 – July 23, 2021) was an American theoretical physicist and Nobel laureate in physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic interaction between elementary particles. He held the Josey Regental Chair in Science at the University of Texas at Austin, where he was a member of the Physics and Astronomy Departments. His research on elementary particles and physical cosmology was honored with numerous prizes and awards, including the 1979 Nobel Prize in physics and the 1991 National Medal of Science. In 2004, he received the Benjamin Franklin Medal of the American Philosophical Society, with a citation that said he was "considered by many to be the preeminent theoretical physicist alive in the world today." He was elected to the U.S. National Academy of Sciences, Britain's Royal Society, the American Philosophical Society, and the American Academy of Arts and Sciences. Weinb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GUT Scale
The grand unification energy \Lambda_, or the GUT scale, is the energy level above which, it is believed, the electromagnetic force, weak force, and strong force become equal in strength and unify to one force governed by a simple Lie group. The exact value of the grand unification energy (if grand unification is indeed realized in nature) depends on the precise physics present at shorter distance scales not yet explored by experiments. If one assumes the Desert and supersymmetry, it is at around 1025 eV or 10^ GeV (≈ 1.6 megajoules). Some Grand Unified Theories (GUTs) can predict the grand unification energy but, usually, with large uncertainties due to model dependent details such as the choice of the gauge group, the Higgs sector, the matter content or further free parameters. Furthermore, at the moment it seems fair to state that there is no agreed ''minimal GUT''. The unification of the electroweak force and the strong force with the gravitational force in a so-called "Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Higgsino
In particle physics, for models with N=1 supersymmetry a higgsino, symbol , is the superpartner of the Higgs field. A higgsino is a Dirac fermionic field with spin and it refers to a weak isodoublet with hypercharge half under the Standard Model gauge symmetries. After electroweak symmetry breaking higgsino fields linearly mix with U(1) and SU(2) gauginos leading to four neutralinos and two charginos that refer to physical particles. While the two charginos are charged Dirac fermions (plus and minus each), the neutralinos are electrically neutral Majorana fermions. In an R-parity-conserving version of the Minimal Supersymmetric Standard Model, the lightest neutralino typically becomes the lightest supersymmetric particle (LSP). The LSP is a particle physics candidate for the dark matter of the universe since it cannot decay to particles with lighter mass. A neutralino LSP, depending on its composition can be bino, wino or higgsino dominated in nature and can have different zone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersymmetry
In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories exist. Supersymmetry is a spacetime symmetry between two basic classes of particles: bosons, which have an integer-valued spin and follow Bose–Einstein statistics, and fermions, which have a half-integer-valued spin and follow Fermi–Dirac statistics. In supersymmetry, each particle from one class would have an associated particle in the other, known as its superpartner, the spin of which differs by a half-integer. For example, if the electron exists in a supersymmetric theory, then there would be a particle called a ''"selectron"'' (superpartner electron), a bosonic partner of the electron. In the simplest supersymmetry theories, with perfectly " unbroken" supersymmetry, each pair of superpartners would share the same mass and intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hierarchy Problem
In theoretical physics, the hierarchy problem is the problem concerning the large discrepancy between aspects of the weak force and gravity. There is no scientific consensus on why, for example, the weak force is 1024 times stronger than gravity. Technical definition A hierarchy problem occurs when the fundamental value of some physical parameter, such as a coupling constant or a mass, in some Lagrangian is vastly different from its effective value, which is the value that gets measured in an experiment. This happens because the effective value is related to the fundamental value by a prescription known as renormalization, which applies corrections to it. Typically the renormalized value of parameters are close to their fundamental values, but in some cases, it appears that there has been a delicate cancellation between the fundamental quantity and the quantum corrections. Hierarchy problems are related to fine-tuning problems and problems of naturalness. Over the past decade ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersymmetric
In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories exist. Supersymmetry is a spacetime symmetry between two basic classes of particles: bosons, which have an integer-valued spin and follow Bose–Einstein statistics, and fermions, which have a half-integer-valued spin and follow Fermi–Dirac statistics. In supersymmetry, each particle from one class would have an associated particle in the other, known as its superpartner, the spin of which differs by a half-integer. For example, if the electron exists in a supersymmetric theory, then there would be a particle called a ''"selectron"'' (superpartner electron), a bosonic partner of the electron. In the simplest supersymmetry theories, with perfectly " unbroken" supersymmetry, each pair of superpartners would share the same mass and inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proton Decay4
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ratio). Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as " nucleons" (particles present in atomic nuclei). One or more protons are present in the nucleus of every atom. They provide the attractive electrostatic central force which binds the atomic electrons. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol ''Z''). Since each element has a unique number of protons, each element has its own unique atomic number, which determines the number of atomic electrons and consequently the chemical characteristics of the element. The word ''proton'' is Greek for "first", and this name was given to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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