title: Glossary of string theory
text: # 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
  