# Glossary of string theory

This page is a glossary of terms in string theory, including related areas such as supergravity, supersymmetry, and high energy physics.
* Conventions
* αβγ
* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* XYZ
* See also
* References

## Conventions
### -bein

    A suffix indicating a frame, where the first part is a German word indicating the dimension (as in zweibein, vierbein, and so on).

### -ino

    The superpartners of bosons are often denoted by the suffix -ino; for example, photon/photino.

### s-

    The superpartners of fermions are often denoted by adding s- at the beginning; for example, quark/squark.

## αβγ
### α

    1. Fine-structure constant
    2. Regge slope, or inverse of the string tension
    3. A Fourier coefficient of a spacetime coordinate.
    4. α$_s$ is the strong coupling constant

### β

    1. One of the two conformal superghost fields β, γ used in the BRST quantization of the superstring
    2. Euler beta function
    3. Beta function describing the change of coupling constant under the renormalization group flow

### γ

    1. Dirac matrix
    2. One of the two conformal superghost fields β, γ used in the BRST quantization of the superstring
    3. World-sheet metric γ$_{ab}$(σ,τ)
    4. Photon
    5. Euler constant .57721...

### Γ

    1. Lattice
    2. Euler Gamma function
    3. Dirac matrix
    4. Width of some scattering process

### δ

    1. Kronecker delta function
    2. An infinitesimal change in something; for example δL is an infinitesimal change in L

### Δ

    1. Propagator
    2. Delta baryon, a baryon with 3 light quarks and isospin 3/2
    3. Laplace operator in Euclidean space or more generally a Riemannian manifold

### ε

    1. Small positive real number
    2. Antisymmetric tensor

### η

    1. Flat Lorentzian metric on spacetime
    2. Dedekind eta function, a weight 1/2 modular form
    3. Eta meson, a neutral flavor meson with PC = –+

### θ

    1. Theta function
    2. θ$_c$ is the Cabbibo angle
    3. θ$_w$ is the Weinberg angle, also called the weak mixing angle

### Λ

    1. Cosmological constant
    2. Large energy or large mass cutoff in regularization
    3. Lambda baryon, a baryon with 2 light quarks and isospin 0

### μ

    1. Renormalization scale, with the dimensions of mass
    2. Muon

### ν

    Neutrino

### Ξ

    1. Xi baryon, a baryon with 1 light quark

### π

    1. 3.14159...
    2. Pion

### Π

    The momentum density conjugate to X

### ρ

    Rho meson, a light meson with PC = ––

### σ

    1. Spacelike coordinate on the world-sheet
    2. Scattering cross section
    3. Pauli matrix
    4. See #sigma model

### Σ

    1. Sigma baryon, a baryon with 2 light quarks and isospin 1

### τ

    1. Timelike coordinate on the world-sheet
    2. Element of the upper half plane
    3. Tauon

### Υ

    Upsilon meson (bb)

### φ

    Scalar field

### χ

    Neutral-flavor heavy meson with PC = ++

### ψ

    1. Spinor field
    2. Psi meson (cc)

### Ω

    1. Density of something in the universe; for example, Ω$_ν$ is the neutrino density
    2. Omega baryon, a baryon with no light quarks

### ' (prime)

    X′ means ∂X/∂σ.

### dot above letter

    Ẋ means ∂X/∂τ
    1. A covariant derivative
    2. The del operator.
    The D'Alembert operator, or non-Euclidean Laplacian.
    A commutator: [A,B] = AB–BA.
    An anticommutator: {A,B} = AB+BA.

## A
### A

    1. A connection 1-form
    2. Short for antiperiodic, a boundary condition on strings.
    3. Short for axial vector
    4. An asymmetry

### action

    Main article: action (physics) A function S on the space of fields given (formally) by the integral of the Lagrangian density over spacetime, whose stationary points are the solutions of the equations of motion.

### ADE

    Main article: ADE classification Refers to the ADE classification (A$_n$,D$_n$, E$_6$, E$_7$, E$_8$) of simply laced Dynkin diagrams, and to several related classifications of Lie algebras, singularities and so on.

### ADHM

    Initials of Atiyah, Drinfeld, Hitchin, and Manin, as in the ADHM construction of instantons.

### ADM

    Initials of Arnowitt, Deser, and Misner, as in ADM energy, a way of defining the global energy in an asymptotically flat spacetime, or ADM decomposition of a metric, or ADM formalism.

### AdS

    Anti-de Sitter, as in anti-de Sitter space, a Lorentzian analogue of hyperbolic space

### AdS/CFT

    Anti-de Sitter/conformal field theory, especially the AdS/CFT correspondence.

### ALE

    Asymptotically locally Euclidean

### ALEPH

    ALEPH experiment at LEP

### AMSB

    Anomaly mediation supersymmetry breaking

### ASD

    Anti self-dual (connection)

### ATLAS

    The ATLAS experiment at CERN, a particle detector.

### axino

    Main article: Axino A hypothetical supersymmetric partner of an axion.

### axion

    Main article: Axion A hypothetical scalar particle whose mass arises from a coupling rather than from a mass term in the Lagrangian, used to resolve the strong CP problem.

## B
### b

    1. One of the two conformal ghost fields b, c used in the BRST quantization of the bosonic string.
    2. A bottom quark.

### B

    1. Baryon number
    2. Short for boson.
    3. Short for baryon.
    4. Short for backward;for example, σ$_B$ is the cross section for backward scattering.
    5. a bottom meson.

### BAO

    Baryon acoustic oscillation

### BB

    Big Bang

### BBN

    Big Bang nucleosynthesis

### bino

    Main article: gaugino A hypothetical supersymmetric partner of the gauge field corresponding to weak hypercharge.

### BIon

    A BPS solution representing an infinite string ending on a D-brane. Named after the Born–Infeld action.

### BPS

    Main article: BPS state A state related to the Bogomol'nyi–Prasad–Sommerfield bound.

### BR

    Branching ratio

### BRST quantization

    Main article: BRST quantization Short for Becchi, Rouet, Stora and Tyutin, who introduced the BRST quantization of gauge theories.

### brane

    Short for membrane. a higher-dimensional manifold moving in spacetime. See also p-brane, D-brane.

### BTZ

    Initials of Bañados–Teitelboim–Zanelli, as in BTZ black hole, a black hole in 2+1-dimensional gravity.

### BV

    Batalin–Vilkovisky, as in Batalin–Vilkovisky formalism.

## C
### c

    1. The speed of light, when not using units where this is 1.
    2. A central charge of the Virasoro algebra or similar algebra.
    3. One of the two conformal ghost fields b, c used in the BRST quantization of the bosonic string.
    4. A Chern class.
    5. A charm quark.

### C

    1. Charge, especially the charge symmetry.

### Calabi–Yau

    Main article: Calabi–Yau manifold A Kähler manifold with vanishing Ricci curvature, used for compactifying string theories.

### CAR

    Canonical anticommutation relations

### CBR

    Cosmic background radiation

### CC

    1. Charged current (weak interaction).
    2. Complex conjugate
    3. Compatibility condition

### CCR

    Canonical commutation relation
    CCR and CAR algebras

### CDF

    Collider Detector at Fermilab

### CDM

    Cold dark matter

### CERN

    Conseil Européen pour la Recherche Nucléaire

### chargino

    Main article: chargino A hypothetical charged supersymmetric partner of a gauge boson.

### Chern–Simons

    1. Main article: Chern–Simons theory
    2. Main article: Chern–Simons form

### chiral

    1. Not invariant under the parity symmetry. The word comes from the Greek χειρ meaning "hand"; the terms "left-handed" and "right-handed" are often used to describe chiral objects. Main article: Chirality (physics)
    2. A chiral multiplet is a type of supermutliplet of a supersymmetry algebra.

### CIPT

    Contour improved perturbation theory

### CKG

    Short for conformal Killing group.

### CKM

    The Cabibbo–Kobayashi–Maskawa matrix.

### CKS

    Short for conformal Killing spinor.

### CKV

    Short for conformal Killing vector.

### CFT

    Conformal field theory

### Chan–Paton

    A Chan–Paton charge is a degree of freedom carried by an open string on its endpoints.

### cl

    1. Short for classical (for example, S$_{cl}$ is the classical action).
    2. CL is short for confidence limit.

### closed

    A closed string is one with no ends.

### CM

    Center of mass (frame)

### CMBR

    Cosmic microwave background radiation

### CMS

    1. The Compact Muon Solenoid at CERN, a particle detector.
    2. Short for the Center-of-Momentum System, a coordinate system where the total momentum is 0.

### compactification

    A method for reducing the apparent dimension of spacetime by wrapping the string around a compact manifold.

### cosmological constant

    Main article: cosmological constant The constant term of the Lagrangian, inducing a term in the action proportional to the volume of spacetime

### CP

    Short for Charge–Parity, as in CP symmetry.

### CPC

    Short for Charge–Parity conservation.

### CPT

    Short for Charge–Parity–Time, as in CPT symmetry or CPT theorem.

### CPV

    Short for Charge–Parity violation.

### critical

    The critical dimension is the spacetime dimension in which a string or superstring theory is consistent; usually 26 for string theories and 10 for superstring theories.

### CVC

    Conserved vector current.

### CY

    Short for Calabi–Yau, as in Calabi–Yau manifold, a Ricci-flat Kähler manifold, often used for compactifying superstring theories.

## D
### d

    1. The exterior derivative of a form.
    2. A down quark.
    3. The dimension of spacetime.

### D

    1. Short for Dirichlet, as in D-brane
    2. The dimension of spacetime
    3. A connection or differential operator
    4. A Dynkin diagram of an orthogonal group in even dimensions.
    5. A charmed meson.

### D0

    Main article: DØ experiment

### Dp-brane

    Main article: D-brane Short for Dirichlet (mem)brane, a submanifold (of dimension p+1) on which the ends of strings are constrained to lie, so that the strings satisfy Dirichlet boundary conditions.

### D-string

    A D1-brane

### DBI

    Short for Dirac–Born–Infeld, as in the DBI action, an action based on the Born–Infeld action, a modification of the Maxwell action of electrodynamics.

### DDF

    Initials of Del Guidice, Di Vecchia, and Fubini, as in Del Guidice–Di Vecchia–Fubini operator, operators generating an oscillator algebra.

### DELPHI

    DELPHI experiment at LEP.

### DESY

    Deutsches Elektronen-Synchrotron

### DGLAP

    Initials of Dokshitzer–Gribov–Lipatov–Altarelli–Parisi who introduced the DGLAP evolution equation in QCD.

### Diff

    Diffeomorphism or diffeomorphism group.

### dilatino

    Main article: dilatino A supersymmetric partner of the dilaton.

### dilaton

    Main article: dilaton A massless scalar particle, related to dilations of spacetime.

### Dirichlet

    Dirichlet boundary conditions on an open string say that the ends of the string are fixed (often lying on a D-brane).

### DIS

    Deep inelastic scattering

### DLCQ

    Discrete light-cone quantization

### DM

    Dark matter

### DØ

    Main article: DØ experiment

### Dp-brane

    Main article: D-brane Short for Dirichlet (mem)brane, a submanifold (of dimension p+1) on which the ends of strings are constrained to lie, so that the strings satisfy Dirichlet boundary conditions.

### DR

    1. Short for dimensional regularization.
    2. Short for dimensional reduction, a way of constructing theories from simpler theories in higher dimensions, sometimes by making fields invariant under some spacelike translations.

### dS

    de Sitter, as in de Sitter space, a Lorentzian analogue of a sphere

### dS/CFT

    de Sitter/conformal field theory, especially the dS/CFT correspondence.

### dual resonance model

    Main article: Dual resonance model An early precursor of string theory.

### duality

    Main article: String duality A hidden connection between two different theories, such as S-duality, T-duality, U-duality, mysterious duality.

### DY

    Initials of Drell–Yan, as in DY process.

### dyon

    Main article: Dyon A hypothetical particle with both electrical and magnetic charge.

## E
### e

    1. Euler's constant
    2. A frame
    3. An electron

### E

    Energy

### E6

    Main article: E6 (mathematics) E$_6$ is the exceptional Lie algebra of rank 6 and dimension 78.

### E7

    Main article: E7 (mathematics) E$_7$ the exceptional Lie algebra of rank 7 and dimension 133.

### E8

    Main article: E8 (mathematics) E$_8$ the exceptional Lie algebra of rank 8 and dimension 248.

### eff

    Short for effective (field theory).

### EFT

    Effective field theory, a low-energy approximation to a theory.

### einbein

    A frame in 1 dimension

### elfbein

    A frame in 11 dimensions

### energy–momentum tensor

    Main article: Energy–momentum tensor A symmetric tensor T (also called the stress-energy tensor) describing the variation of the action under changes in the metric, whose components give the local energy, momentum and stress densities. In flat spacetimes it can also be given by combining the Noether currents of the translation symmetries.

### EWSB

    Electro-weak symmetry breaking.

## F
### F

    1. A curvature form of a connection
    2. The world-sheet fermion number.
    3. Short for fermion
    3. Short for forward;for example, σ$_F$ is the cross section for backward scattering.

### F4

    Main article: F4 (mathematics) F$_4$ is the exceptional Lie algebra of rank 4 and dimension 52.

### FCNC

    Flavor-changing neutral current.

### field

    A section of a fiber bundle

### FOPT

    Fixed-order perturbation theory.

### F-string

    Fundamental string

### F-theory

    Main article: F-theory Possibly an abbreviation of father theory. A 12-dimensional string theory introduced by Vafa.

### FRW

    Friedman–Robertson–Walker metric on spacetime

## G
### g

    1. A metric
    2. A coupling constant
    3. The genus of a Riemann surface.
    4. A gluon.

### G

    1. Newton's gravitational constant, sometimes written G$_N$.
    2. The Fermi coupling constant for weak interactions, sometimes written G$_F$.
    3. G$_n$ is an odd element of the Ramond or Neveu–Schwarz superalgebra.

### G2

    Main article: G2 (mathematics) The exceptional Lie algebra of rank 2 and dimension 14, or a G2 manifold with G$_2$ holonomy.

### gaugino

    A spin 1/2 supersymmetric partner of a gauge boson.

### gh

    Abbreviation for ghost; for example, S$_{gh}$ is the ghost action.

### ghost

    A vector of negative norm.

### GKO

    Short for Goddard–Kent–Olive. The GKO construction, also called the coset construction, is a way of constructing unitary discrete series representations of the Virasoro algebra.

### GL

    A general linear group.

### gluino

    Main article: gluino A hypothetical supersymmetric partner of a gluon.

### gluon

    Main article: gluon A gauge boson associated with the strong force.

### GMSB

    Gauge mediated supersymmetry breaking.

### goldstino

    Main article: goldstino A massless spin 1/2 particle associated with spontaneous breakdown of supersymmetry, analogous to the Goldstone boson.

### GR

    General relativity

### graviton

    Main article: graviton A conjectural spin 2 massless particle responsible for gravity.

### gravitino

    Main article: gravitino A supersymmetric partner of the graviton.

### Green

    Named for Michael Green.

### GS

    Green–Schwarz formalism, a way of incorporating supersymmetry into string theory that is supersymmetric in 10-dimensional spacetime.

### GSO

    Short for Ferdinando Gliozzi, Joël Scherk, and David A. Olive, as in the GSO projection, a projection in superstring theory that eliminates tachyons.

### GSW

    The 2-volume work on superstring theory by Green, Schwarz, and Witten.

### GUT

    Grand unified theory, a hypothetical theory unifying the strong and electroweak forces.

### GWS

    Glashow–Weinberg–Salem theory of the electroweak force.

### GZK

    The Greisen–Zatsepin–Kuzmin limit on the energy of cosmic background radiation from distant sources.

## H
### h

    1. The weight of a field (for example, its eigenvalue for L$_0$).
    2. Hermitian; for example, h.c. stands form hermitian conjugate.

### H

    1. The Hamiltonian.
    2. The Higgs boson.
    3. The Hubble constant.

### Haag–Łopuszański–Sohnius theorem

    Main article: Haag–Łopuszański–Sohnius theorem A theorem describing the possible supersymmetries of a quantum field theory, generalizing the Coleman–Mandula theorem.

### Hagedorn temperature

    Main article: Hagedorn temperature The temperature above which the partition function diverges due to the exponentially increasing number of string states.

### hc

    Hermitian conjugate

### HCMS

    Hadronic center of mass (frame)

### HDM

    Higgs doublet model

### HE

    Short for heterotic-E$^2$ $_8$, a heterotic string theory based on the group E$^2$ $_8$.

### helicity

    Main article: Helicity (particle physics) The projection of the spin of a massless particle in the direction of its momentum.

### HERA

    Hadron Elektron Ring Anlage

### heterotic

    Main article: heterotic string Named after the Greek word heterosis, meaning hybrid vigour. A hybrid of bosonic string theory and superstring theory, introduced by David Gross, Jeffrey Harvey, Emil Martinec, and Ryan Rohm in 1985.

### Higgs boson

    Main article: Higgs boson A massive scalar particle related to the spontaneous symmetry breaking mechanism in the electroweak theory.

### Higgsino

    Main article: Higgsino A hypothetical supersymmetric partner of a Higgs boson.

### HO

    Short for heterotic-orthogonal, a heterotic string theory based on the orthogonal group O$_{32}$(R).

### holographic principle

    Main article: Holographic principle

### HQET

    Main article: Heavy quark effective theory

### Hyperkaehler

    Main article: Hyperkähler manifold A Riemannian manifold with holonomy contained in the compact form of the symplectic group.

### Hypermultiplet

    Main article: Hypermultiplet A type of supermultiplet (representation) of an extended supersymmetry algebra.

## I
### i

    √–1

### I

    Isospin.

### IGM

    Intergalactic medium

### inflation

    Main article: Inflation (cosmology) A hypothetical very rapid increase in the size of the very early universe.

### instanton

    Main article: Instanton A self-dual or anti-self-dual connection in a principal bundle over a four-dimensional Riemannian manifold.

### int

    Short for interaction; for example, H$_{int}$ might be an interaction Hamiltonian.

### inv

    Short for invisible; for example, Γ$_{inv}$ is the width for invisible decays (those unobseverd by an experiment).

## J
### J

    1. A current
    2. A source
    3. Spin.

## K
### k

    A momentum

### K

    A kaon (a strange meson).

### K3

    Main article: K3 surface A simply connected compact complex surface of Kodaira dimension 0

### K-theory

    Main articles: K-theory and K-theory (physics) A cohomology theory based on vector bundles.

### Kac–Moody algebra

    Main article: Kac–Moody algebra A central extension of a loop algebra.

### Kaehler

    Named after Erich Kähler
    1. A Kähler manifold is a complex manifold with a compatible Riemannian metric.
    2. A Kähler metric is the metric on a Kähler manifold.
    3. A Kähler potential is a function of superfields used to construct a Lagrangian.

### Kalb–Ramond field

    Main article: Kalb–Ramond field

### KK

    Kaluza–Klein

### KM

    1. The Kobayashi–Maskawa mechanism for CP violation.
    2. Kac–Moody algebra.

### KZ

    Initials of Knizhnik and Zamolodchikov, as in KZ equation, a differential equation related to the primary fields of a current algebra.

## L
### L

    1. A Lagrangian
    2. L$_n$ is an element of the Virasoro algebra.
    3. An abbreviation for left (moving modes).
    4. Lepton number
    5. Short for lepton

### L3

    L3 experiment at LEP.

### Lagrangian (field theory)

    Main article: Lagrangian (field theory) A function on the jet space of a fiber bundle.

### landscape

    Main article: String theory landscape The (conjectural) moduli space of all (vacuums of) string theories.

### LEP

    The Large Electron–Positron Collider at CERN.

### lepton

    Main article: lepton An elementary particle of spin 1/2 that is unaffected by the strong force.

### LH

    Left-handed

### LHC

    The large hadron collider at CERN.

### little string theory

    Main article: Little string theory

### LL

    Double logarithmic

### LO

    Leading order (term)

### LQG

    Loop quantum gravity

### LQC

    Loop quantum cosmology

### LSP

    Abbreviation for lightest supersymmetric particle.

### LSS

    Large scale structure (of the universe).

## M
### m

    A mass of a fermion. For example, m$_t$ is the mass of the top quark t.

### M

    The mass of a boson; for example, M$_Z$ is the mass of the Z-boson.

### Majorana spinor

    Main articles: Majorana fermion and Majorana spinor A fermion or spinor with a reality condition, in spacetimes of dimension 2, 3, 4 mod 8.

### Majorana–Weyl spinor

    Main articles: Majorana–Weyl fermion and Majorana–Weyl spinor A half-spinor with a reality condition, in spacetimes of dimension 2 mod 8.

### Mandelstam variable

    Main article: Mandelstam variables A sum or difference of two of the four incoming or outgoing momenta of a 2-particle interaction.

### M(atrix) theory

    Main article: Matrix string theory One of several non-perturbative formulations of string theory or M-theory using infinite matrices.

### membrane

    Main article: Membrane (M-theory) A higher dimensional analogue of a string.

### MC

    Monte Carlo integration

### MCG

    Main article: Mapping class group

### minimal model

    Certain solvable conformal field theories.

### Mirror symmetry (string theory)

    Main article: Mirror symmetry (string theory) A partly conjectural relation between a type IIA superstring theory compactified on a Calabi–Yau manifold and a type IIB superstring theory compactified on a different "mirror" Calabi–Yau manifold.

### MLLA

    Modified leading logarithm approximation.

### MNS

    Maki–Nakagawa–Sakata matrix for neutrino mixing

### monopole

    Main articles: Magnetic monopole, Dirac monopole, Wu–Yang monopole, 't Hooft–Polyakov monopole, Seiberg-Witten monopole, and Monopole (mathematics) A hypothetical particle similar to a "magnet with only one pole".

### Montonen–Olive duality

    Main article: Montonen–Olive duality An early case of S-duality.

### MS

    minimal subtraction (a renormalization scheme). MS is the modified minimal subtraction scheme.

### MSM

    Abbreviation for minimal standard model.

### MSSM

    Abbreviation for minimal supersymmetric standard model.

### mSUGRA

    Minimal model of supergravity.

### M-theory

    Main article: M-theory An 11-dimensional theory introduced in the second string theory revolution to unify the 5 known superstring theories. The letter M has been said to stand for membrane, matrix, magic, mystery, monster, and so on.

### MSW

    Mikheyev–Smirnov–Wolfenstein effect concerning neutrino oscillations in matter.

### multiplet

    A linear representation of a Lie algebra or group.
    A collection of elementary particles corresponding to a basis of a representation.

## N
### N

    1. The number of times each irreducible real spinor representation appears in the fermionic part of a supersymmetry algebra or super Minkowski space. It is often used in the description of an extended supersymmetry algebra, as in N=2 superconformal algebra and so on.
    2. A nucleon, a baryon with 3 light quarks and isospin 1/2 (such as a proton or neutron).
    3. The number of some type of particle.

### Nambu–Goto action

    Main article: Nambu–Goto action An action for strings, proportional to the area of the worldsheet.

### NC

    Neutral current (weak interaction).

### Neumann

    Neumann boundary conditions on an open string say that the momentum normal to the boundary of the world-sheet is zero.

### neutralino

    Main article: Neutralino A hypothetical supersymmetric partner of a gauge boson with zero charge.

### Neveu

    Named for André Neveu.

### Neveu–Schwarz algebra

    Main article: Neveu–Schwarz algebra A supersymmetric extension of the Virasoro algebra, similar to the Ramond algebra.

### NG

    1. Short for Nambu–Goto, as in Nambu–Goto action.
    2. Short for Nambu–Goldstone, as in Nambu–Goldstone boson.

### NLL

    Next to leading logarithmic (term).

### NLO

    Next to leading order (term).

### NLSP

    next-to-lightest sypersymmetric particle

### NMSSM

    Next-to-Minimal Supersymmetric Standard Model.

### NNLL

    Next to next to leading logarithmic (term).

### NNLO

    Next to next to leading order (term).

### NNNLL

    Next to next to next to leading logarithmic (term).

### no-ghost theorem

    Main article: No-ghost theorem A theorem stating that some hermitian form is positive semidefinite, in other words has no ghosts (negative norm vectors). The name is a word-play on no-go theorem.

### NR

    Non-relativistic

### NRQCD

    Non-relativistic quantum chromodynamics

### NS

    Neveu–Schwarz, especially the Neveu–Schwarz algebra

### NS–NS

    A sector with Neveu–Schwarz conditions on left and right moving modes.

### NS–R

    A sector with Neveu–Schwarz conditions on left moving modes and Ramond conditions on right moving modes.

### NUT

    The initials of E. Newman, L. Tamburino, and T. Unti, mainly used in Taub–NUT vacuum, a solution to Einsteins' equations.

## O
### O

    An orthogonal group

### OCQ

    Short for old covariant quantization

### OPAL

    The OPAL detector at LEP.

### open

    An open string is one with two ends.

### operator product expansion

    Main article: Operator product expansion A description of short-distance singularities of fields.

### orbifold

    Main article: orbifold Something that looks locally like a manifold quotiented by the action of a finite group.

### OSp

    A Lie superalgebra.

## P
### p

    A momentum

### P

    1. Parity, especially the parity symmetry.
    2. Short for periodic, a boundary condition on strings (as opposed to A for antiperiodic).
    3. Pseudoscalar (current)
    4. Momentum
    5. One of the bosonic elements of a supersymmetry algebra.

### p-brane

    A p+1 dimensional membrane, where p is a non-negative integer. The dimension of membranes is often given by their space dimension, which is 1 less than their full spacetime dimension.

### PCAC

    partially conserved axial vector current

### PDF

    Parton distribution function.

### PDG

    Particle Data Group.

### photino

    Main article: photino A hypothetical supersymmetric partner of the photon.

### photon

    Main article: photon The neutral spin 1 gauge boson of the electromagnetic field.

### PMNS

    Pontecorvo–Maki–Nakagawa–Sakata matrix for neutrino mixing

### Polyakov action

    Main article: Polyakov action A modification of the Nambu–Goto action for strings that eliminates the square root.

### PQ

    Peccei–Quinn, as in Peccei–Quinn theory.

### PQCD

    Perturbative quantum chromodynamics.

### prepotential

    A function used to construct the vector superfield in supersymmetric gauge theory and Seiberg–Witten theory.

### primary field

    A field killed by the positive weight operators of the Virasoro algebra (or similar algebra); in other words, a lowest weight vector.

### Princeton string quartet

    David Gross, Jeffrey Harvey, Emil Martinec, and Ryan Rohm, who introduced the heterotic string in 1985.

### PSL

    Projective special linear group.

## Q
### q

    A quark.

### Q

    1. The BRST operator.
    2. A charge
    3. One of the fermionic generators of a supersymmetry algebra.

### quark

    Main article: quark A strongly interacting elementary particle of spin 1/2.

### QCD

    Main article: Quantum chromodynamics

### QED

    Main article: Quantum electrodynamics

## R
### R

    1. Short for Ramond, as in Ramond sector.
    2. A curvature tensor Main articles: Scalar curvature, Ricci curvature, and Riemann curvature
    3. An abbreviation for right (moving modes).
    4. A radius
    5. R-symmetry is a symmetry of extended supersymmetry algebras.

### Ramond

    Named for Pierre Ramond.

### Ramond algebra

    Main article: Ramond algebra A supersymmetric extension of the Virasoro algebra, similar to the Neveu–Schwarz algebra.

### Rarita–Schwinger

    Main articles: Rarita–Schwinger equation and Rarita–Schwinger field Refers to spin 3/2 fermions.

### Regge

    1. Physicist Tullio Regge.
    2. Regge trajectory: the squared mass of a hadronic resonance is roughly linear in the spin, with the constant of proportionality called the Regge slope.

### revolution

    Any new idea in string theory. In particular the first superstring revolution refers to the discoveries in the mid 1980s such as the cancellation of gravitational anomalies and the heterotic string, and the second superstring revolution refers to the discoveries in the mid 1990s, such as D-branes, M-theory, and matrix theory and the AdS/CFT correspondence.

### RG

    Renormalization group.

### RGE

    Renormalization group equation.

### RH

    Right-handed

### R–NS

    A sector with Ramond conditions on left moving modes and Neveu–Schwarz conditions on right moving modes.

### RNS

    Ramond–Neveu–Schwarz, as in RNS formalism, a way of incorporating supersymmetry into string theory that is supersymmetric on the world sheet.

### R-parity

    Main article: R-parity A Z$_2$ symmetry of supersymmetric models.

### R-R

    Short for Ramond–Ramond sector

## S
### s

    1. A strange quark.
    2. A Mandelstam variable

### S

    1. An action
    2. A scattering matrix.
    3. The transformation τ → –1/τ of the upper half plane
    4. Scalar (current)
    5. Short for super or supersymmetric

### S-brane

    A brane similar to a D-brane, with Dirichlet boundary conditions in the time direction.

### S-duality

    Main article: S-duality Strong–weak duality, a string duality relating theories with a large coupling constant to theories with a small coupling constant

### SBB

    Standard Big Bang model of the universe

### SCFT

    Superconformal field theory, a supersymmetric extension of conformal field theory

### Schwarz

    Named for John Henry Schwarz

### Seiberg duality

    Main article: Seiberg duality

### SGA

    Abbreviation for Spectrum-generating algebra

### short supermultiplet

    A supermultiplet (representation) related to BPS states

### sigma model

    Main articles: Sigma model and Non-linear sigma model A classical or quantum model based on the maps from a base manifold to a target manifold.

### SL

    Special linear group

### SLAC

    Stanford Linear Accelerator Center

### SLC

    Stanford Linear Collider

### slepton

    Main article: slepton Hypothetical supersymmetric partner of a lepton

### SM

    Main article: Standard Model

### sneutrino

    Main article: sneutrino Hypothetical supersymmetric partner of a neutrino

### SO

    Special orthogonal group

### Sp

    Symplectic group

### sphaleron

    Main article: Sphaleron Static solution to the electroweak field equations

### squark

    Main article: squark Supersymmetric partner of a quark.

### SSB

    Spontaneous symmetry breaking

### SSM

    Standard solar model

### stress–energy tensor

    Alternative name for the #energy–momentum tensor.

### string field theory

    Main article: string field theory

### SU

    Special unitary group

### SUGRA

    Short for supergravity

### superconformal algebra

    Main articles: Neveu–Schwarz algebra and Ramond algebra A supersymmetric analogue of the Virasoro algebra of conformal symmetries in 2 dimensions

### superfield

    Main article: Superfield A supersymmetric analogue of a quantum or classical field

### supergravity

    Main article: supergravity A supersymmetric extension of general relativity

### supermultiplet

    Main article: Supermultiplet A representation of a supersymmetry algebra

### superpotential

    Main article: Superpotential A function of chiral superfield not depending on their superderivatives or spacetime derivatives, used to form a Lagrangian.

### superspace

    Main article: superspace A supersymmetric analogue of spacetime

### superstring

    Main article: superstring A supersymmetric analogue of a string

### supersymmetry

    Main articles: supersymmetry and supersymmetry algebra A generalization of a Lie superalgebra, where the Lie bracket [a,b] is sometimes given by ab+ba rather than ab–ba.

### SUSY

    An abbreviation for supersymmetry.

### SYM

    Supersymmetric Yang–Mills

## T
### t

    1. A top quark.
    2. A Mandelstam variable.
    3. Time.

### T

    1. The energy–momentum tensor.
    2. Time, especially the time symmetry.
    3. The transformation τ → τ+1 of the upper half plane.
    4. A torus.
    5. The string tension.
    6. Temperature.
    7. Tensor (current)

### T-duality

    Main article: T-duality A string duality relating theories on a large spacetime to theories on a small spacetime. In particular it exchanges type IIA and IIB superstring theory.

### tachyon

    Main article: Tachyon A particle of imaginary mass moving faster than light.

### TOE

    Theory of everything

### type IIB

    Main article: Type I string theory Main article: Type II string theory A type of superstring or the corresponding low-energy supergravity theory. The Roman numeral I or II refers to the number of d=10 supersymmetries, and types IIA or IIB are distinguished by whether the supersymmetries of left and right movers have opposite or identical chiralities.

## U
### u

    1. An up quark.
    2. A Mandelstam variable.

### U

    A unitary group.

### U-duality

    Main article: U-duality Short for "unified duality". A string duality relating two different string theories.

### UED

    Universal extra dimensions

### UV

    Short for ultra-violet, often referring to short-distance singularities.

## V
### V

    1. A vertex operator.
    2. Vector (current)

### V-A

    Vector-Axial vector

### vector superfield

    A type of superfield related to vector supermultiplets.

### VEV

    Vacuum expectation value of an operator.

### vielbein

    A frame

### vierbein

    A frame in 4 dimensions. Sometimes used for a frame in an arbitrary number of dimension by authors who do not care that "vier" means four in German.

### Veneziano amplitude

    Main article: Veneziano amplitude The Euler beta function interpreted as a scattering amplitude.

### vertex operator

    Main article: vertex operator

### Virasoro algebra

    Main article: Virasoro algebra A central extension of the Witt algebra of polynomial vector fields on a circle.

## W
### w

    A complex number

### W

    A W-boson

### W-algebra

    Main article: W-algebra A sort of generalization of the Virasoro algebra

### Weyl

    1. Named after Hermann Weyl
    2. A Weyl transformation is a rescaling of the world-sheet metric.
    3. Weyl spinor, an element of a half-spin representation in even spacetime dimensions.

### WIMP

    Weakly interacting massive particle

### wino

    Main article: wino (particle) A hypothetical supersymmetric partner of the W-boson.

### Witten

    Named for Edward Witten.

### WMAP

    Wilkinson Microwave Anisotropy Probe

### world sheet

    The 2-dimensional subset of spacetime swept out by a moving string.

### world-volume

    The p+1-dimensional spacetime volume swept out by a p-brane, as in world-volume action.

### WZW

    Initials of Wess, Zumino, (Novikov), and Witten, as in the WZW model, a σ-model with a group as the target space.

## XYZ
### x

    A real number

### X

    Used for coordinates in Minkowski space.

### y

    A real number

### YBE

    Yang–Baxter equation

### YM

    Yang–Mills

### z

    A complex number

### Z

    1. A partition function
    2. The Z boson.
    An element of the center of an extended supersymmetry algebra.

### ZEUS

    Main article: ZEUS (particle detector)

### zino

    Main article: gaugino A hypothetical supersymmetric partner of the Z-boson.

### zweibein

    A frame in 2 dimensions