--- title: "Glossary of string theory" chunk: 3/5 source: "https://en.wikipedia.org/wiki/Glossary_of_string_theory" category: "reference" tags: "science, encyclopedia" date_saved: "2026-05-05T07:51:24.096924+00:00" instance: "kb-cron" --- 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, 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 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 GN. 2. The Fermi coupling constant for weak interactions, sometimes written GF. 3. 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 1. The weight of a field (for example, its eigenvalue for L0). 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 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-E28, a heterotic string theory based on the group E28. 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 √–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 1. A current 2. A source 3. 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 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 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. Ln 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) 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.