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
-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: Fine-structure constant Regge slope, or inverse of the string tension How are these related? There is only one dimensional constant in string theory, and that is the inverse string tension $$\alpha^{\prime}$$ with units of area. Sometimes $$\alpha^{\prime}$$ is therefore replaced by a length $$l_s=\sqrt{\alpha^{\prime}}$$. The string tension is mostly defined as the fraction
 * $$\frac{1}{2\pi\alpha^{\prime}}.$$

Tension is energy or work per unit length. In natural units $$c=1$$ and $$\hbar=1$$, and hence $$\alpha^{\prime}$$ has dimension of length/energy or length/mass. Since $$\hbar$$ has the dimension of action, i.e. momentum times length, it follows that in natural units mass =1/length, and so $$\alpha^{\prime}$$ has the unit of area. The slope $$\alpha^{\prime}$$ of a Regge trajectory $$\alpha(M^2)$$ in Regge theory is the derivative of spin $$S$$ or angular momentum with respect to mass-squared, i.e.
 * $$\frac{dS}{dM^2}.$$

Since angular momentum is moment of momentum $$p$$, i.e. length times mass with $$c=1$$, $$S$$ is dimensionless in natural units, and $$\alpha^{\prime}$$ has units of $$1/M^2$$ or area like the inverse string tension.

A Fourier coefficient of a spacetime coordinate. αs is the strong coupling constant

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

γ: Dirac matrix One of the two conformal superghost fields β, γ used in the BRST quantization of the superstring World-sheet metric γab(σ,τ) Photon Euler constant .57721...

Γ: Lattice Euler Gamma function Dirac matrix Width of some scattering process

δ: Kronecker delta function An infinitesimal change in something; for example δL is an infinitesimal change in L

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

ε: Small positive real number Antisymmetric tensor

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

θ: Theta function θc is the Cabbibo angle θw is the Weinberg angle, also called the weak mixing angle

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

μ: Renormalization scale, with the dimensions of mass Muon

ν: Neutrino

Ξ: Xi baryon, a baryon with 1 light quark

π: 3.14159... Pion

Π: The momentum density conjugate to X

ρ: Rho meson, a light meson with PC = ––

σ: Spacelike coordinate on the world-sheet Scattering cross section Pauli matrix See

Σ: Sigma baryon, a baryon with 2 light quarks and isospin 1

τ: Timelike coordinate on the world-sheet Element of the upper half plane Tauon

Υ: Upsilon meson (b$\overline{b}$)

φ: Scalar field

χ: Neutral-flavor heavy meson with PC = ++

ψ: Spinor field Psi meson (c$\overline{c}$)

Ω: Density of something in the universe; for example, Ων is the neutrino density Omega baryon, a baryon with no light quarks

!$@
' (prime): X&prime; means ∂X/∂σ.

dot above letter: Ẋ means ∂X/∂τ

∇: A covariant derivative 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: A connection 1-form Short for antiperiodic, a boundary condition on strings. Short for axial vector An asymmetry

action: 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: Refers to the ADE classification (An,Dn, E6, E7, E8) 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: A hypothetical supersymmetric partner of an axion.

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

B: Baryon number Short for boson. Short for baryon. Short for backward;for example, σB is the cross section for backward scattering. a bottom meson.

BAO: Baryon acoustic oscillation

BB: Big Bang

BBN: Big Bang nucleosynthesis

bino: 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: A state related to the Bogomol'nyi–Prasad–Sommerfield bound.

BR: Branching ratio

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

C: Charge, especially the charge symmetry.

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

CAR: Canonical anticommutation relations

CBR: Cosmic background radiation

CC: Charged current (weak interaction). Complex conjugate 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: A hypothetical charged supersymmetric partner of a gauge boson.

Chern–Simons:

chiral: 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. 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: Short for classical (for example, Scl is the classical action). CL is short for confidence limit.

closed: A closed string is one with no ends.

CM: Center of mass (frame)

CMB: CMBR: Cosmic microwave background radiation

CMS: The Compact Muon Solenoid at CERN, a particle detector. 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: 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: The exterior derivative of a form. A down quark. The dimension of spacetime.

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

D0:

D-brane: Dp-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: A supersymmetric partner of the dilaton.

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:

Dp-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: Short for dimensional regularization. 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: An early precursor of string theory.

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: A hypothetical particle with both electrical and magnetic charge.

E
e: Euler's constant A frame An electron

E: Energy

E6: E6 is the exceptional Lie algebra of rank 6 and dimension 78.

E7: E7 the exceptional Lie algebra of rank 7 and dimension 133.

E8: E8 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: 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: A curvature form of a connection The world-sheet fermion number. Short for fermion Short for forward;for example, σF is the cross section for backward scattering.

F4: F4 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: Possibly an abbreviation of father theory. A 12-dimensional string theory introduced by Vafa.

FRW: Friedman–Robertson–Walker metric on spacetime

G
g: A metric A coupling constant The genus of a Riemann surface. A gluon.

G: Newton's gravitational constant, sometimes written GN. The Fermi coupling constant for weak interactions, sometimes written GF. Gn is an odd element of the Ramond or Neveu–Schwarz superalgebra.

G2: The exceptional Lie algebra of rank 2 and dimension 14, or a G2 manifold with G2 holonomy.

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

gh: Abbreviation for ghost; for example, Sgh 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: A hypothetical supersymmetric partner of a gluon.

gluon: A gauge boson associated with the strong force.

GMSB: Gauge mediated supersymmetry breaking.

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

GR: General relativity

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

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: The weight of a field (for example, its eigenvalue for L0). Hermitian; for example, h.c. stands form hermitian conjugate.

H: The Hamiltonian. The Higgs boson. The Hubble constant.

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

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

h.c.: 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: The projection of the spin of a massless particle in the direction of its momentum.

HERA: Hadron Elektron Ring Anlage

heterotic: 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: A massive scalar particle related to the spontaneous symmetry breaking mechanism in the electroweak theory.

Higgsino: A hypothetical supersymmetric partner of a Higgs boson.

HO: Short for heterotic-orthogonal, a heterotic string theory based on the orthogonal group O32(R).

holographic principle:

HQET:

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

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

I
i: $\sqrt{–1}$

I: Isospin.

IGM: Intergalactic medium

inflation: A hypothetical very rapid increase in the size of the very early universe.

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, Hint might be an interaction Hamiltonian.

inv: Short for invisible; for example, Γinv is the width for invisible decays (those unobseverd by an experiment).

J
J: A current A source Spin.

K
k: A momentum

K: A kaon (a strange meson).

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

K-theory: A cohomology theory based on vector bundles.

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

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

Kalb–Ramond field:

KK: Kaluza–Klein

KM: The Kobayashi–Maskawa mechanism for CP violation. 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: A Lagrangian Ln is an element of the Virasoro algebra. An abbreviation for left (moving modes). Lepton number Short for lepton

L3: L3 experiment at LEP.

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

landscape: The (conjectural) moduli space of all (vacuums of) string theories.

LEP: The Large Electron–Positron Collider at CERN.

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:

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, mt is the mass of the top quark t.

M: The mass of a boson; for example, MZ is the mass of the Z-boson.

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

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

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

matrix theory: M(atrix) theory: One of several non-perturbative formulations of string theory or M-theory using infinite matrices.

M-brane: membrane: A higher dimensional analogue of a string.

MC: Monte Carlo integration

MCG:

minimal model: Certain solvable conformal field theories.

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: A hypothetical particle similar to a "magnet with only one pole".

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

MS: minimal subtraction (a renormalization scheme). $\overline{MS}$ 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: 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: 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. A nucleon, a baryon with 3 light quarks and isospin 1/2 (such as a proton or neutron). The number of some type of particle.

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

Neveu: Named for André Neveu.

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

NG: Short for Nambu–Goto, as in Nambu–Goto action. 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: 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.

OPE: operator product expansion: A description of short-distance singularities of fields.

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: Parity, especially the parity symmetry. Short for periodic, a boundary condition on strings (as opposed to A for antiperiodic). Pseudoscalar (current) Momentum 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: A hypothetical supersymmetric partner of the photon.

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

PMNS: Pontecorvo–Maki–Nakagawa–Sakata matrix for neutrino mixing

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: 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: The BRST operator. A charge One of the fermionic generators of a supersymmetry algebra.

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

QCD:

QED:

R
R: Short for Ramond, as in Ramond sector. A curvature tensor An abbreviation for right (moving modes). A radius R-symmetry is a symmetry of extended supersymmetry algebras.

Ramond: Named for Pierre Ramond.

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

Rarita–Schwinger: Refers to spin 3/2 fermions.

Regge: Physicist Tullio Regge. 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: A Z2 symmetry of supersymmetric models.

R-R: Short for Ramond–Ramond sector

S
s: A strange quark. A Mandelstam variable

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

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

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:

SGA: Abbreviation for Spectrum-generating algebra

short supermultiplet: A supermultiplet (representation) related to BPS states

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: Hypothetical supersymmetric partner of a lepton

SM:

sneutrino: Hypothetical supersymmetric partner of a neutrino

SO: Special orthogonal group

Sp: Symplectic group

sphaleron: Static solution to the electroweak field equations

squark: Supersymmetric partner of a quark.

SSB: Spontaneous symmetry breaking

SSM: Standard solar model

stress–energy tensor: Alternative name for the.

string field theory:

SU: Special unitary group

SUGRA: Short for supergravity

superconformal algebra: A supersymmetric analogue of the Virasoro algebra of conformal symmetries in 2 dimensions

superfield: A supersymmetric analogue of a quantum or classical field

supergravity: A supersymmetric extension of general relativity

supermultiplet: A representation of a supersymmetry algebra

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

superspace: A supersymmetric analogue of spacetime

superstring: A supersymmetric analogue of a string

supersymmetry: 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: A top quark. A Mandelstam variable. Time.

T: The energy–momentum tensor. Time, especially the time symmetry. The transformation τ → τ+1 of the upper half plane. A torus. The string tension. Temperature. Tensor (current)

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: A particle of imaginary mass moving faster than light.

ToE: TOE: Theory of everything

type I: type II: type IIA: type IIB: 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: An up quark. A Mandelstam variable.

U: A unitary group.

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: A vertex operator. 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: The Euler beta function interpreted as a scattering amplitude.

vertex operator:

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: A sort of generalization of the Virasoro algebra

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

WIMP: Weakly interacting massive particle

wino: 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.

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

ZEUS:

zino: A hypothetical supersymmetric partner of the Z-boson.

zweibein: A frame in 2 dimensions