# Magnetic monopole

magnetic monopolesmagnetic chargemonopolemonopolesDirac monopoleDirac quantization conditionisolated magnetic polesMagnetricityDirac magnetic monopoleDirac quantization conditions
In particle physics, a magnetic monopole is a hypothetical elementary particle that is an isolated magnet with only one magnetic pole (a north pole without a south pole or vice versa).wikipedia
306 Related Articles

### Magnet

permanent magnetmagnetspermanent magnets
In particle physics, a magnetic monopole is a hypothetical elementary particle that is an isolated magnet with only one magnetic pole (a north pole without a south pole or vice versa). Therefore, the ordinary phenomena of magnetism and magnets have nothing to do with magnetic monopoles.
In this approach, the divergence of the magnetization ∇·M inside a magnet and the surface normal component M·n are treated as a distribution of magnetic monopoles.

### Gauss's law for magnetism

Gauss' law for magnetismGauss's lawfor magnetism
Gauss's law for magnetism, one of Maxwell's equations, is the mathematical statement that magnetic monopoles do not exist.
It is equivalent to the statement that magnetic monopoles do not exist.

### Maxwell's equations

Maxwell equationsMaxwell equationMaxwell’s equations
Gauss's law for magnetism, one of Maxwell's equations, is the mathematical statement that magnetic monopoles do not exist.
Gauss's law for magnetism states that there are no "magnetic charges" (also called magnetic monopoles), analogous to electric charges.

### Magnetic dipole

dipolemagnetic dipoles
The ends of a flux tube form a magnetic dipole, but since they move independently, they can be treated for many purposes as independent magnetic monopole quasiparticles.
In particular, a magnetic monopole, the magnetic analogue of an electric charge, has never been observed.

### Paul Dirac

DiracPaul Adrien Maurice DiracP. A. M. Dirac
The quantum theory of magnetic charge started with a paper by the physicist Paul Dirac in 1931.
He proposed and investigated the concept of a magnetic monopole, an object not yet known empirically, as a means of bringing even greater symmetry to James Clerk Maxwell's equations of electromagnetism.

### Magnetic moment

magnetic dipole momentmagnetic momentsdipole moment
However, an improved understanding of electromagnetism in the nineteenth century showed that the magnetism of lodestones was properly explained not by magnetic monopole fluids, but rather by a combination of electric currents, the electron magnetic moment, and the magnetic moments of other particles.
(To date, no isolated magnetic monopoles have been experimentally detected.) A magnetic dipole is the limit of either a current loop or a pair of poles as the dimensions of the source are reduced to zero while keeping the moment constant.

### Elementary charge

eelectron chargecharge
In this paper, Dirac showed that if any magnetic monopoles exist in the universe, then all electric charge in the universe must be quantized (Dirac quantization condition).
Paul Dirac persuasively argued in 1931 that if magnetic monopoles exist, then electric charge must be quantized; however, it is unknown whether magnetic monopoles actually exist.

### 't Hooft–Polyakov monopole

monopolesmassive magnetic monopoles
The Dirac monopole is a singular solution of Maxwell's equation (because it requires removing the worldline from spacetime); in more complicated theories, it is superseded by a smooth solution such as the 't Hooft–Polyakov monopole.
In theoretical physics, the 't Hooft–Polyakov monopole is a topological soliton similar to the Dirac monopole but without any singularities.

### Dirac string

This semi-infinite line is called the Dirac string and its effect on the wave function is analogous to the effect of the solenoid in the Aharonov–Bohm effect.
In physics, a Dirac string is a hypothetical one-dimensional curve in space, conceived of by the physicist Paul Dirac, stretching between two Dirac magnetic monopoles with opposite magnetic charges, or from one magnetic monopole out to infinity.

### Magnetic field

magnetic fieldsmagneticmagnetic flux density
First, electric currents create magnetic fields according to Ampère's law.
(Such vector fields are called solenoidal vector fields.) This property is called Gauss's law for magnetism and is equivalent to the statement that there are no isolated magnetic poles or magnetic monopoles.

### Magnetism

magneticmagneticsmagnetic properties
Therefore, the ordinary phenomena of magnetism and magnets have nothing to do with magnetic monopoles.
Nevertheless, some theoretical physics models predict the existence of these magnetic monopoles.

### Grand Unified Theory

grand unified theoriesgrand unification theorygrand unification
Modern interest in the concept stems from particle theories, notably the grand unified and superstring theories, which predict their existence.
Some GUTs, such as the Pati-Salam model, predict the existence of magnetic monopoles.

### Inflation (cosmology)

cosmic inflationinflationcosmological inflation
Specifically, more recent theories of cosmic inflation drastically reduce the predicted number of magnetic monopoles, to a density small enough to make it unsurprising that humans have never seen one.
Many physicists also believe that inflation explains why the universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the universe is flat, and why no magnetic monopoles have been observed.

### Aharonov–Bohm effect

Aharonov-Bohm effectAharonov–Bohmnonlocality
This semi-infinite line is called the Dirac string and its effect on the wave function is analogous to the effect of the solenoid in the Aharonov–Bohm effect. The wave function of an electrically charged particle (a "probe charge") that orbits the "equator" generally changes by a phase, much like in the Aharonov–Bohm effect.
The magnetic Aharonov–Bohm effect is also closely related to Dirac's argument that the existence of a magnetic monopole can be accommodated by the existing magnetic source-free Maxwell's equations if both electric and magnetic charges are quantized.

### Proton decay

decayproton half-lifeprotons decay
) For these reasons, monopoles became a major interest in the 1970s and 80s, along with the other "approachable" predictions of GUTs such as proton decay.
Some beyond-the-Standard Model grand unified theories (GUTs) explicitly break the baryon number symmetry, allowing protons to decay via the Higgs particle, magnetic monopoles, or new X bosons with a half-life of 10 31 to 10 36 years.

### Magnetic flux

fluxfluxes definition of flux used in electromagnetism
So that the phase a charged particle gets when going in a loop is the magnetic flux through the loop.
(A "closed surface" is a surface that completely encloses a volume(s) with no holes.) This law is a consequence of the empirical observation that magnetic monopoles have never been found.

### String theory

string theoriststringstring theories
So in a consistent holographic theory, of which string theory is the only known example, there are always finite-mass monopoles.
For example, the standard Big Bang model does not explain why the universe appears to be same in all directions, why it appears flat on very large distance scales, or why certain hypothesized particles such as magnetic monopoles are not observed in experiments.

### Dyon

More accurately, GUTs predicted a range of particles known as dyons, of which the most basic state was a monopole.
A dyon with a zero electric charge is usually referred to as a magnetic monopole.

### Bogomolny equations

Bogomolny equation
In mathematics, the Bogomolny equations for magnetic monopoles are the equations F A = *D A φ, where F A is the curvature of a connection A on a G-bundle over a 3-manifold M, φ is a section of the corresponding adjoint bundle and * is the Hodge star operator on M.

### Blas Cabrera Navarro

Blas Cabrera
Although there have been tantalizing events recorded, in particular the event recorded by Blas Cabrera Navarro on the night of February 14, 1982 (thus, sometimes referred to as the "Valentine's Day Monopole" ), there has never been reproducible evidence for the existence of magnetic monopoles.
Blas Cabrera Navarro (born September 21, 1946 in Paris, France) is a Stanley G. Wojcicki Professor of Physics at Stanford University best known for his experiment in search of magnetic monopoles.

### Spin ice

There are a number of examples in condensed-matter physics where collective behavior leads to emergent phenomena that resemble magnetic monopoles in certain respects, including most prominently the spin ice materials.
Experiments have found evidence for the existence of deconfined magnetic monopoles in these materials, with properties resembling those of the hypothetical magnetic monopoles postulated to exist in vacuum.

### MoEDAL experiment

MoEDAL
The MoEDAL experiment, installed at the Large Hadron Collider, is currently searching for magnetic monopoles and large supersymmetric particles using nuclear track detectors and aluminum bars around LHCb's VELO detector.
MoEDAL shares the cavern at Point 8 with LHCb, and its prime goal is to directly search for the magnetic monopole (MM) or dyon and other highly ionizing stable massive particles (SMPs) and pseudo-stable massive particles.

### Big Bang

Big Bang theoryThe Big Bangbig-bang
Cosmological models of the events following the Big Bang make predictions about what the horizon volume was, which lead to predictions about present-day monopole density.
The magnetic monopole objection was raised in the late 1970s.

### Wu–Yang monopole

Wu-Yang monopole
It describes a magnetic monopole which is pointlike and has a potential which behaves like 1/r everywhere.

### P. Buford Price

Another experiment in 1975 resulted in the announcement of the detection of a moving magnetic monopole in cosmic rays by the team led by P. Buford Price.
The particle was tentatively identified as a magnetic monopole in 1975 by Price and some colleagues.