mass generation mechanism
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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 natural phenomena. This is in contrast to experimental physics, which uses experim ...
, a mass generation mechanism is a theory that describes the origin of
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
from the most fundamental laws of
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
. Physicists have proposed a number of models that advocate different views of the origin of mass. The problem is complicated because the primary role of
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
is to mediate
gravitational interaction In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
between bodies, and no theory of gravitational interaction reconciles with the currently popular Standard Model of
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) an ...
. There are two types of mass generation models: gravity-free models and models that involve gravity.


Background


Electroweak theory and the Standard Model

The
Higgs mechanism In the Standard Model of particle physics, the Higgs mechanism is essential to explain the generation mechanism of the property "mass" for gauge bosons. Without the Higgs mechanism, all bosons (one of the two classes of particles, the other be ...
is based on a symmetry-breaking scalar field potential, such as the quartic. The Standard Model uses this mechanism as part of the Glashow–Weinberg–Salam model to unify
electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...
and weak interactions. This model was one of several that predicted the existence of the scalar Higgs boson.


Gravity-free models

In these theories, as in the Standard Model itself, the
gravitational interaction In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
either is not involved or does not play a crucial role.


Technicolor

Technicolor Technicolor is a series of Color motion picture film, color motion picture processes, the first version dating back to 1916, and followed by improved versions over several decades. Definitive Technicolor movies using three black and white films ...
models break electroweak symmetry through gauge interactions, which were originally modeled on quantum chromodynamics.


Coleman-Weinberg mechanism

Coleman–Weinberg mechanism generates mass through spontaneous symmetry breaking through radiative corrections.


Other theories

*
Unparticle physics In theoretical physics, unparticle physics is a speculative theory that conjectures a form of matter that cannot be explained in terms of particles using the Standard Model of particle physics, because its components are scale invariant. Howard ...
and the unhiggs models posit that the Higgs sector and Higgs boson are scaling invariant, also known as unparticle physics. * UV-Completion by Classicalization, in which the unitarization of the WW scattering happens by creation of classical configurations. * Symmetry breaking driven by non-equilibrium dynamics of quantum fields above the electroweak scale. *Asymptotically safe
weak interaction In nuclear physics and particle physics, the weak interaction, which is also often called the weak force or weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction ...
s based on some nonlinear sigma models. * Models of composite W and Z vector bosons. *
Top quark condensate In particle physics, the top quark condensate theory (or top condensation) is an alternative to the Standard Model fundamental Higgs field, where the Higgs boson is a composite field, composed of the top quark and its antiquark. The top quark-antiq ...
.


Gravitational models

* Extra-dimensional Higgsless models use the fifth component of the gauge fields in place of the Higgs fields. It is possible to produce electroweak symmetry breaking by imposing certain boundary conditions on the extra dimensional fields, increasing the
unitarity In quantum physics, unitarity is the condition that the time evolution of a quantum state according to the Schrödinger equation is mathematically represented by a unitary operator. This is typically taken as an axiom or basic postulate of quant ...
breakdown scale up to the energy scale of the extra dimension. Through the AdS/QCD correspondence this model can be related to technicolor models and to ''UnHiggs'' models, in which the Higgs field is of unparticle nature. * Unitary Weyl gauge. If one adds a suitable gravitational term to the standard model action with gravitational coupling, the theory becomes locally scale-invariant (i.e. Weyl-invariant) in the unitary gauge for the local SU(2). Weyl transformations act multiplicatively on the Higgs field, so one can fix the Weyl gauge by requiring that the Higgs scalar be a constant. *
Preon In particle physics, preons are point particles, conceived of as sub-components of quarks and leptons. The word was coined by Jogesh Pati and Abdus Salam, in 1974. Interest in preon models peaked in the 1980s but has slowed, as the Standard Mode ...
and models inspired by preons such as the Ribbon model of Standard Model particles by
Sundance Bilson-Thompson Sundance Osland Bilson-Thompson is an Australian theoretical particle physicist. He has developed the idea that certain preon models may be represented topologically, rather than by treating preons as pointlike particles. His ideas have attracte ...
, based in
braid theory A braid (also referred to as a plait) is a complex structure or pattern formed by interlacing two or more strands of flexible material such as textile yarns, wire, or hair. The simplest and most common version is a flat, solid, three-strande ...
and compatible with loop quantum gravity and similar theories. This model not only explains the origin of mass, but also interprets electric charge as a topological quantity (twists carried on the individual ribbons), and colour charge as modes of twisting. * In the theory of superfluid vacuum, masses of elementary particles arise from interaction with a physical
vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...
, similarly to the gap generation mechanism in
superfluid Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two ...
s. The low-energy limit of this theory suggests an effective potential for the Higgs sector that is different from the Standard Model's, yet it yields the mass generation. Under certain conditions, this potential gives rise to an elementary particle with a role and characteristics similar to the Higgs boson.


References

{{reflist, 25em Standard Model Physics beyond the Standard Model Mass