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Naturalness (physics)
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. Throughout the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theoretical Physics
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict List of natural phenomena, natural phenomena. This is in contrast to experimental physics, which uses experimental tools to probe these phenomena. The advancement of science generally depends on the interplay between experimental studies and theory. In some cases, theoretical physics adheres to standards of mathematical rigour while giving little weight to experiments and observations.There is some debate as to whether or not theoretical physics uses mathematics to build intuition and illustrativeness to extract physical insight (especially when normal experience fails), rather than as a tool in formalizing theories. This links to the question of it using mathematics in a less formally rigorous, and more intuitive or heuristic way than, say, mathematical physics. For example, while developing special relativity, Albert E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Higgs Boson
The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particle physics theory. In the Standard Model, the Higgs particle is a massive scalar boson that Coupling (physics), couples to (interacts with) particles whose mass arises from their interactions with the Higgs Field, has zero Spin (physics), spin, even (positive) Parity (physics), parity, no electric charge, and no color charge, colour charge. It is also very unstable, particle decay, decaying into other particles almost immediately upon generation. The Higgs field is a scalar field with two neutral and two electrically charged components that form a complex doublet (physics), doublet of the weak isospin SU(2) symmetry. Its "Spontaneous symmetry breaking#Sombrero potential, sombrero potential" leads it to take a nonzero value everywhere (inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coleman–Weinberg Potential
The Coleman–Weinberg model represents quantum electrodynamics of a scalar field in four-dimensions. The Lagrangian for the model is :L = -\frac (F_)^2 + , D_ \phi, ^2 - m^2 , \phi, ^2 - \frac , \phi, ^4 where the scalar field is complex, F_=\partial_\mu A_\nu-\partial_\nu A_\mu is the electromagnetic field tensor, and D_=\partial_\mu-\mathrm i (e/\hbar c)A_\mu the covariant derivative containing the electric charge e of the electromagnetic field. Assume that \lambda is nonnegative. Then if the mass term is tachyonic, m^20 the vacuum expectation of the field \phi is zero. At the classical level the latter is true also if m^2=0. However, as was shown by Sidney Coleman and Erick Weinberg, even if the renormalized mass is zero, spontaneous symmetry breaking still happens due to the radiative corrections (this introduces a mass scale into a classically conformal theory - the model has a conformal anomaly). The same can happen in other gauge theories. In the broken phase the flu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersymmetry
Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It proposes that for every known particle, there exists a partner particle with different spin properties. There have been multiple experiments on supersymmetry that have failed to provide evidence that it exists in nature. If evidence is found, supersymmetry could help explain certain phenomena, such as the nature of dark matter and the hierarchy problem in particle physics. A supersymmetric theory is a theory in which the equations for force and the equations for matter are identical. In theoretical physics, theoretical and mathematical physics, any theory with this property has the ''principle of supersymmetry'' (SUSY). Dozens of supersymmetric theories exist. In theory, supersymmetry is a type of Spacetime symmetries, spacetime symmetry betwe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feynman Diagram
In theoretical physics, a Feynman diagram is a pictorial representation of the mathematical expressions describing the behavior and interaction of subatomic particles. The scheme is named after American physicist Richard Feynman, who introduced the diagrams in 1948. The calculation of probability amplitudes in theoretical particle physics requires the use of large, complicated integrals over a large number of variables. Feynman diagrams instead represent these integrals graphically. Feynman diagrams give a simple visualization of what would otherwise be an arcane and abstract formula. According to David Kaiser, "Since the middle of the 20th century, theoretical physicists have increasingly turned to this tool to help them undertake critical calculations. Feynman diagrams have revolutionized nearly every aspect of theoretical physics." While the diagrams apply primarily to quantum field theory, they can be used in other areas of physics, such as solid-state theory. Frank Wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Higgs Field
The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particle physics theory. In the Standard Model, the Higgs particle is a massive scalar boson that Coupling (physics), couples to (interacts with) particles whose mass arises from their interactions with the Higgs Field, has zero Spin (physics), spin, even (positive) Parity (physics), parity, no electric charge, and no color charge, colour charge. It is also very unstable, particle decay, decaying into other particles almost immediately upon generation. The Higgs field is a scalar field with two neutral and two electrically charged components that form a complex doublet (physics), doublet of the weak isospin SU(2) symmetry. Its "Spontaneous symmetry breaking#Sombrero potential, sombrero potential" leads it to take a nonzero value everywhere (inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirac Field
In quantum field theory, a fermionic field is a quantum field whose Quantum, quanta are fermions; that is, they obey Fermi–Dirac statistics. Fermionic fields obey canonical anticommutation relations rather than the canonical commutation relations of bosonic fields. The most prominent example of a fermionic field is the ''Dirac field'', which describes fermions with Spin (physics), spin-1/2: electrons, protons, quarks, etc. The Dirac field can be described as either a 4-component spinor or as a pair of 2-component Weyl spinors. Spin-1/2 Majorana fermions, such as the hypothetical neutralino, can be described as either a dependent 4-component Majorana spinor or a single 2-component Weyl spinor. It is not known whether the neutrino is a Majorana fermion or a Dirac fermion; observing double beta decay#neutrinoless double beta decay, neutrinoless double-beta decay experimentally would settle this question. Basic properties Free (non-interacting) fermionic fields obey canonical antico ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yukawa Coupling
In particle physics, Yukawa's interaction or Yukawa coupling, named after Hideki Yukawa, is an interaction between particles according to the Yukawa potential. Specifically, it is between a scalar field (or pseudoscalar field) \ \phi\ and a Dirac field \ \psi\ of the type The Yukawa interaction was developed to model the strong force between hadrons. A Yukawa interaction is thus used to describe the nuclear force between nucleons mediated by pions (which are pseudoscalar mesons). A Yukawa interaction is also used in the Standard Model to describe the coupling between the Higgs field and massless quark and lepton fields (i.e., the fundamental fermion particles). Through spontaneous symmetry breaking, these fermions acquire a mass proportional to the vacuum expectation value of the Higgs field. This Higgs-fermion coupling was first described by Steven Weinberg in 1967 to model lepton masses. Classical potential If two fermions interact through a Yukawa interaction mediated by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Large Hadron Collider
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator. It was built by the CERN, European Organization for Nuclear Research (CERN) between 1998 and 2008, in collaboration with over 10,000 scientists, and hundreds of universities and laboratories across more than 100 countries. It lies in a tunnel in circumference and as deep as beneath the France–Switzerland border near Geneva. The first collisions were achieved in 2010 at an energy of 3.5 tera-electronvolts (TeV) per beam, about four times the previous world record. The discovery of the Higgs boson at the LHC was announced in 2012. Between 2013 and 2015, the LHC was shut down and upgraded; after those upgrades it reached 6.5 TeV per beam (13.0 TeV total collision energy). At the end of 2018, it was shut down for maintenance and further upgrades, and reopened over three years later in April 2022. The collider has four crossing points where the accelerated particles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mu Problem
In theoretical physics, the problem is a problem of supersymmetric theories, concerned with understanding the parameters of the theory. Background The supersymmetric Higgs mass parameter appears as the following term in the superpotential: . It is necessary to provide a mass for the fermionic superpartners of the Higgs bosons, i.e. the higgsinos, and it enters as well the scalar potential of the Higgs bosons. To ensure that and get a non-zero vacuum expectation value after electroweak symmetry breaking, should be of the order of magnitude of the electroweak scale, many orders of magnitude smaller than the Planck scale (), which is the natural cutoff scale. This brings about a problem of naturalness: Why is that scale so much smaller than the cutoff scale? And why, if the term in the superpotential has different physical origins, do the corresponding scale happen to fall so close to each other? Before LHC, it was thought that the soft supersymmetry breaking terms shoul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gian Francesco Giudice
Gian Francesco Giudice (born 25 January 1961) is an Italian theoretical physicist working at CERN in particle physics and cosmology. Academic career After graduating in physics from the University of Padua in 1984, Giudice obtained in 1988 his PhD in theoretical physics from the International School for Advanced Studies in Trieste. Between 1988 and 1990 he was Research Associate at the Fermi National Accelerator Laboratory near Chicago. Between 1990 and 1992 he was Research Fellow in the Physics Department of the University of Texas at Austin, in the group led by Steven Weinberg. After being employed by the Istituto Nazionale di Fisica Nucleare of Italy, in 1993 he moved to CERN, where is currently the Head of the Theoretical Physics Department. Academician of the Accademia dei Lincei, the Istituto Veneto di Scienze, Lettere ed Arti, and Accademia Galileiana, he has been awarded the Jacques Solvay Chair in Physics at the Université libre de Bruxelles (2013), Distinguished Visi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riccardo Barbieri
Riccardo Barbieri (born 1944) is an Italian theoretical physicist and a professor at the Scuola Normale Superiore di Pisa. He has written more than two hundred research papers in the field of theoretical elementary particle physics, and has been particularly influential in physics beyond the Standard Model. Research career Riccardo Barbieri received his undergraduate education in 1963-67 at the Scuola Normale Superiore in Pisa and at the University of Pisa. His ''laurea'' advisor was Pietro Menotti. During his professionalization classes (''perfezionamento'') in 1967-69 at the Scuola Normale Superiore and in later years he worked on higher-order radiative corrections in Quantum Electrodynamics with Ettore Remiddi. In the 1970s he turned to computations in Quantum Chromodynamics, collaborating in particular with Raoul Gatto and Zoltan Kunszt. In 1976 at CERN, he made the prediction, later experimentally verified, of the hadronic widths of the three charmonium P-waves. In 1980 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
