|  Path-Integral Approach to Quantum Field Theory | 
In General, Flat Space
  $ Def: A scalar quantum
    field theory in d dimensions is a Borel measure dμ on
    the space \({\cal D}'({\mathbb R}^d)\) of real-valued distributions f
    over \(\mathbb R\)d, satisfying:
    (1) Euclidean invariance; (2) Osterwalder-Schrader Positivity; (3) Regularity.
  * Smoothness: The test
    functions to which we apply the operator-valued fields φ (i.e.,
    the configuration space) cannot be just smooth ones, because then the
    2-point functions would go to a constant as Δx →
    0, which they don't [except in (0+1)-dimensional quantum mechanics]; They are
    instead very rough [& Streater]; > s.a. field theory.
  * Results: It follows that
    there exists a Hilbert space carrying a unitary representation of the
    Poincaré group P, with a distinguished P-invariant
    vector |0\(\rangle\) and a class of unbounded self-adjoint (field) operators
    {φ(f), f ∈ C\(_0^\infty(\mathbb R^d\))},
    which satisfy locality and transform correctly under  P.
  @ General references: Rzewuski 69;
    Abers & Lee PRP(73);
    Taylor 76; Nash 78;
    Itzykson & Zuber 80;
    Fradkin NPB(93);
    Mosel 03;
    LaChapelle IMTA-mp/06;
    Vargas a1412 [measures on path spaces];
    Blasone et al a1703 [and inequivalent representations].
  @ Heuristic: Ramond 81;
    Rivers 87;
    Das 19.
  @ Constructive: Glimm & Jaffe 87;
    Rivasseau 91.
  @ Field redefinitions: Apfeldorf et al MPLA(01)ht/00;
    Latorre & Morris IJMPA(01)ht-proc;
    > s.a. quantum field theory.
  @ Other pictures:
    Rosenfelder et al ht/98-proc [world-line representation];
    Jackson et al a0810 [sums over multiparticle paths].
  @ Related topics: Steinhaus JPCS(12) [discretization and reparametrization invariance];
    Edwards et al a1812-proc [first quantization approach].
Specific Flat Space Theories > s.a. electroweak
  theory; quantum field theory; parametrized
  theories; types of quantum field theories.
  @ Scalar fields: Klauder PRD(76) [augmented action, non-Gaussian measure];
    Gosselin & Polonyi AP(98) [Klein-Gordon];
    Hawking & Hertog PRD(02)ht/01 [4th-order, and ghosts];
    Kaya PRD(04) [self-interacting];
    Isham & Savvidou JMP(02) [foliation operator];
    Bohacik & Prešnajder ht/05-conf
      [φ4, non-perturbative];
    Belokurov & Shavgulidze a1112 [continuous and discontinuous functions];
    Kaya CQG(15)-a1212 [measure for in-in path integral];
    > s.a. quantum klein-gordon fields.
  @ Maxwell theory:
    Bordag et al JPA(98) [in dielectrics];
    Muslih NCB(00) [canonical form];
    > s.a. gauge theories; QED.
  @ Fermions / spinors:
    Floreanini & Jackiw PRD(88);
    Pugh PRD(88);
    Nielsen & Rohrlich NPB(88);
    Jacobson PLB(89);
    Aliev et al NPB(94);
    Bodmann et al qp/98-proc,
    JMP(99)mp/98;
    Polonyi PLB(99)ht/98,
    ht/98 [Dirac equation];
    Smirnov JPA(99);
    Hiroshima & Lorinczi JFA-a0706 [spin-1/2 Pauli-Fierz model];
    Briggs et al IJMPA(13)-a1109 [in cartesian and spherical coordinates];
    > s.a. dirac quantum field theory; types of path integrals.
  @ Supersymmetric theories: Rogers PLB(87);
    O'Connor JPA(90),
    JPA(90),
    JPA(91);
    Niemi & Pasanen PLB(91);
    Ellicott et al AP(91) [gauge theory].
  @ Related topics:
    Bashkirov & Sardanashvily IJTP(04)ht [covariant Hamiltonian];
    > s.a. lattice gauge theory.
Other Quantum Field Theories
  @ For Riemannian geometries:
    Carfora & Marzuoli PRL(89).
  @ For topological field theories:
    Cugliandolo et al PLB(90);
    Kaul & Rajaraman PLB(90).
  @ In curved spacetime: Jaffe & Ritter CMP(07)ht/06 [Euclidean];
    Baldazzi et al a1901 [Lorentzian, without Wick rotation].
  @ Related topics: Fleischhack & Lewandowski mp/01 [limits of validity].
  > Gravity-related: covariant quantum gravity;
    path-integral quantum gravity; quantum cosmology.
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  send feedback and suggestions to bombelli at olemiss.edu – modified 22 dec 2019