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Little Higgs
In particle physics, little Higgs models are based on the idea that the Higgs boson is a pseudo-Goldstone boson arising from some global symmetry breaking at a TeV energy scale. The goal of little Higgs models is to use the spontaneous breaking of such approximate global symmetries to stabilize the mass of the Higgs boson(s) responsible for electroweak symmetry breaking. The little Higgs models predict a naturally-light Higgs particle. Loop cancellation The main idea behind the little Higgs models is that the one-loop contribution to the tachyonic Higgs boson mass coming from the top quark cancels.Other one-loop contributions are small enough that they don't really matter: The Yukawa coupling of the top quark is enormous because of its huge mass, and all the other fermions' Yukawa couplings and gauge couplings are negligible by comparison. The simplified reason for that cancellation is that a loop's contribution is proportional to the coupling constant of one of the SU(2) groups ... [...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] |
Direct Product Of Groups
In mathematics, specifically in group theory, the direct product is an operation that takes two groups and and constructs a new group, usually denoted . This operation is the group-theoretic analogue of the Cartesian product of sets and is one of several important notions of direct product in mathematics. In the context of abelian groups, the direct product is sometimes referred to as the direct sum, and is denoted G \oplus H. Direct sums play an important role in the classification of abelian groups: according to the fundamental theorem of finite abelian groups, every finite abelian group can be expressed as the direct sum of cyclic groups. Definition Given groups (with operation ) and (with operation ), the direct product is defined as follows: The resulting algebraic object satisfies the axioms for a group. Specifically: ;Associativity: The binary operation on is associative. ;Identity: The direct product has an identity element, namely , where is the identity e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-Higgs-doublet Model
The two-Higgs-doublet model (2HDM) is an extension of the Standard Model of particle physics. 2HDM models are one of the natural choices for beyond-SM models containing two Higgs doublets instead of just one. There are also models with more than two Higgs doublets, for example three Higgs doublet models etc. The addition of the second Higgs doublet leads to a richer phenomenology as there are five physical scalar states viz., the CP even neutral Higgs bosons and (where is heavier than by convention), the CP odd pseudoscalar and two charged Higgs bosons . The discovered Higgs boson is measured to be CP even, so one can map either or with the observed Higgs. A special case occurs when \cos(\beta - \alpha) \rightarrow 0, the alignment limit, in which the lighter CP even Higgs boson has couplings exactly like the SM-Higgs boson. In another limit such limit, where \sin(\beta - \alpha) \rightarrow 0, the heavier CP even boson, i.e. is SM-like, leaving to be the lighter tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Composite Higgs Models
In particle physics, composite Higgs models (CHM) are speculative extensions of the Standard Model (SM) where the Higgs boson is a bound state of new strong interactions. These scenarios are models for physics beyond the SM presently tested at the Large Hadron Collider (LHC) in Geneva. In all composite Higgs models the recently discovered Higgs boson is not an elementary particle (or point-like) but has finite size, perhaps around 10−18 meters. This dimension may be related to the Fermi scale (100 GeV) that determines the strength of the weak interactions such as in β-decay, but it could be significantly smaller. Microscopically the composite Higgs will be made of smaller constituents in the same way as nuclei are made of protons and neutrons. History Often referred to as "natural" composite Higgs models, CHMs are constructions that attempt to alleviate fine-tuning or "naturalness" problem of the Standard Model. These typically engineer the Higgs boson as a naturally light p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ann Nelson
Ann Elizabeth Nelson (April 29, 1958 – August 4, 2019) was a particle physicist and professor of physics in the Particle Theory Group at the University of Washington from 1994 until her death. Nelson received a Guggenheim Fellowship in 2004, and she was elected to the American Academy of Arts and Sciences in 2011 and the National Academy of Sciences in 2012. She was a recipient of the 2018 J. J. Sakurai Prize for Theoretical Particle Physics, presented annually by the American Physical Society and considered one of the most prestigious prizes in physics. Education Born in Baton Rouge, Louisiana, Nelson earned her Bachelor of Science degree at Stanford University in 1980, and her Ph.D. degree at Harvard University under the supervision of Howard Georgi in 1984. Career After a post doctoral fellowship at the Harvard Society of Fellows from 1984-1987, Nelson became an assistant professor at Stanford University in 1987. In 1990 Nelson moved to UC San Diego, and then in 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Howard Georgi
Howard Mason Georgi III (born January 6, 1947) is an American theoretical physicist and the Mallinckrodt Professor of Physics and Harvard College Professor at Harvard University. He is also Director of Undergraduate Studies in Physics. He was Co-Master and then Faculty Dean of Leverett House with his wife, Ann Blake Georgi, from 1998 to 2018. His early work was in Grand Unification and gauge coupling unification within SU(5) and SO(10) groups (see Georgi–Glashow model). Education Georgi graduated from Pingry School in 1964, graduated from Harvard College in 1967 and obtained his Ph.D. from Yale University in 1971. He was Junior Fellow in the Harvard Society of Fellows from 1973–76 and a Senior Fellow from 1982-1998. Career In early 1974 Georgi (with Sheldon Glashow) published the first grand unified theory (GUT), the Minimal SU(5) Georgi–Glashow model. Georgi independently (alongside Harald Fritzsch and Peter Minkowski) published a minimal SO(10) GUT model in 1974. Geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nima Arkani-Hamed
Nima Arkani-Hamed ( fa, نیما ارکانی حامد; born April 5, 1972) is an American-Canadian "Curriculum Vita, updated 4-17-15" sns.ias.edu; accessed December 4, 2015. of Iranian descent, with interests in , quantum fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extra Dimensions
In physics, extra dimensions are proposed additional space or time dimensions beyond the (3 + 1) typical of observed spacetime, such as the first attempts based on the Kaluza–Klein theory. Among theories proposing extra dimensions are: * Large extra dimension, mostly motivated by the ADD model, by Nima Arkani-Hamed, Savas Dimopoulos, and Gia Dvali in 1998, in an attempt to solve the hierarchy problem. This theory requires that the fields of the Standard Model are confined to a four-dimensional membrane, while gravity propagates in several additional spatial dimensions that are large compared to the Planck scale.For a pedagogical introduction, see * Warped extra dimensions, such as those proposed by the Randall–Sundrum model (RS), based on warped geometry where the universe is a five-dimensional anti-de Sitter space and the elementary particles except for the graviton are localized on a (3 + 1)-dimensional brane or branes. * Universal extra dimension, propo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimension
In physics and mathematics, the dimension of a Space (mathematics), mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any Point (geometry), point within it. Thus, a Line (geometry), line has a dimension of one (1D) because only one coordinate is needed to specify a point on itfor example, the point at 5 on a number line. A Surface (mathematics), surface, such as the Boundary (mathematics), boundary of a Cylinder (geometry), cylinder or sphere, has a dimension of two (2D) because two coordinates are needed to specify a point on itfor example, both a latitude and longitude are required to locate a point on the surface of a sphere. A two-dimensional Euclidean space is a two-dimensional space on the Euclidean plane, plane. The inside of a cube, a cylinder or a sphere is three-dimensional (3D) because three coordinates are needed to locate a point within these spaces. In classical mechanics, space and time are different categ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gauge Group
In physics, a gauge theory is a type of field theory in which the Lagrangian (and hence the dynamics of the system itself) does not change (is invariant) under local transformations according to certain smooth families of operations ( Lie groups). The term ''gauge'' refers to any specific mathematical formalism to regulate redundant degrees of freedom in the Lagrangian of a physical system. The transformations between possible gauges, called ''gauge transformations'', form a Lie group—referred to as the '' symmetry group'' or the ''gauge group'' of the theory. Associated with any Lie group is the Lie algebra of group generators. For each group generator there necessarily arises a corresponding field (usually a vector field) called the ''gauge field''. Gauge fields are included in the Lagrangian to ensure its invariance under the local group transformations (called ''gauge invariance''). When such a theory is quantized, the quanta of the gauge fields are called '' gauge bo ... [...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 quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Standard Model, the Higgs particle is a massive scalar boson with zero spin, even (positive) parity, no electric charge, and no colour charge, that couples to (interacts with) mass. It is also very unstable, decaying into other particles almost immediately. The Higgs field is a scalar field, with two neutral and two electrically charged components that form a complex doublet of the weak isospin SU(2) symmetry. Its " Mexican hat-shaped" potential leads it to take a nonzero value ''everywhere'' (including otherwise empty space), which breaks the weak isospin symmetry of the electroweak interaction, and via the Higgs mechanism gives mass to many particles. Both the field and the boson are named after physicist Peter Higgs, who in 1964, along ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimensional Deconstruction
In theoretical physics, dimensional deconstruction is a method to construct ''4''-dimensional theories that behave as higher-dimensional theories in a certain range of higher energies. The resulting theory is a gauge theory whose gauge group is a direct product of many copies of the same group; each copy may be interpreted as the gauge group located at a particular point along a new, discrete, "deconstructed" ''(d+1)''st dimension. The spectrum of matter fields is a set of bifundamental representations expressed by a quiver diagram that is analogous to lattices in lattice gauge theory. "Deconstruction" in physics was introduced by Nima Arkani-Hamed, Andy Cohen and Howard Georgi, and independently by Christopher T. Hill, Stefan Pokorski and Jing Wang. Deconstruction is a lattice approximation to the real space of extra dimensions, while maintaining the full gauge symmetries and yields the low energy effective description of the physics. This leads to a rationale for extensions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
