States in Quantum Field Theory  

In General > s.a. entanglement; Lamb Shift; photon; Plasma; states in quantum mechanics.
@ Space of states: Kijowski RPMP(76) [as a direct limit]; Field & Hughston JMP(99) [geometry, coherent states].
@ Using projective techniques: Okołów CQG(13)-a1304; Lanéry & Thiemann JGP(17)-a1411, JGP(17)-a1411, a1411 [projective limits, states as projective families of density matrices]; Kijowski & Okołów JMP(17)-a1605 [modified construction].
@ Criteria for physically reasonable states: Lechner & Sanders a1511 [modular nuclearity].

Semiclassical States, Classicality > s.a. Classicalization; decoherence; semiclassical quantum mechanics.
* Idea: Two ways of obtaining the classical limit of a quantum field theory are to do a semiclassical expansion of the generating function for correlation functions, and to use 't Hooft's approach and calculate the N → ∞ limit of a Yang-Mills theory.
@ General references: Komar PR(64) [macroscopic distinguishability]; Hepp CMP(74) [correlation functions]; Maslov & Shvedov TMP(98)ht/97 [divergences and renormalization]; Anastopoulos IJTP(99); Lisewski qp/99 [hydrodynamic limit]; Shvedov ht/01, JMP(02)ht/01; Aarts & Berges PRL(02) [far from equilibrium]; Honegger & Rieckers LMP(03) [semiclassical bosonic states]; Park LMP(07)-a0705 [semiclassical theories and Frobenius manifolds]; Mahajan & Padmanabhan GRG(08)-a0708, GRG(08)-a0708 [and particle production]; Yokomizo & Barata JMP(09)-a0907 [non-uniqueness of classical limits and particles vs field]; Burgess et al JCAP(10)-a1005 [breakdown of semiclassical methods]; González-Arroyo & Nuevo PRD(12)-a1205 [quantum corrections to time evolution]; Marian & Marian PRA(13)-a1308 [relative entropy as an exact measure of non-Gaussianity]; Cattaneo et al a1311-ln [semiclassical quantization, and Abelian Chern-Simons theory]; Varela a1404 [as decoherence-free-subspace].
@ Coupled / hybrid quantum and classical fields: Juárez-Aubry et al a1907 [initial-value problem].
@ Quantum to classical transition: Lombardo PhD(98)gq; Everitt et al PRA(09)-a0710; > s.a. classical limit of quantum mechanics.
@ Degree of classicality: Malbouisson & Baseia PS(03).
@ And phase transitions: Lombardo et al IJTP(02)hp, IJTP(02)hp; Kim & Lee PRD(02); Rivers & Lombardo BJP(05)ht/04-conf, IJTP(05)ht/04-proc; Lombardo et al PLB(07)hp.
@ Coarse-graining: Lombardo & Mazzitelli PRD(96) [and decoherence]; Anastopoulos PRD(97)ht/96, gq/98.
@ Perturbative approach: Shvedov ht/04, ht/05 [axiomatic].
@ Field in semiclassical background: Naudts et al ht/02 [model for electromagnetism in quantum spacetime].
@ Pseudoclassical paths: Oaknin PRD(03)ht [for fermions].
> Special states: see coherent states; field theory [localized states]; Squeezed States.
> Related topics: see game theory [matter-field interaction]; phenomenology; renormalization; scattering.

Other Types of States > s.a. fock space [number states]; vacuum.
* Non-equilibrium states: The best-known applications are to electronic transport in normal metals and superconductors.
* Non-linear generalized geometric states: State that interpolate between number states and non-linear pure thermal states.
@ Bound states: Shebeko & Shirokov PPN(01)nt; Camblong & Ordóñez IJMPA(04)ht/01 [path integral]; Liu a1811 [new formalism].
@ Thermal states: Khanna et al 09; Küskü PhD(08)-a0901 [almost-equilibrium states in FLRW spacetimes]; Solveen CQG(10)-a1005 [local thermal equilibrium in flat and curved spacetimes]; Ortíz a1102 [on cylindrically compactified 2D Minkowski space]; Sanders IJMPA(13)-a1209 [linear scalar field in stationary spacetimes]; Solveen CQG(12)-a1211 [in curved spacetimes]; Gransee et al a1508, ch(16)-a1602 [local thermal equilibrium states]; > s.a. thermodynamic systems.
@ Non-equilibrium states: Niemi PLB(88); Niégawa ht/98 [perturbation theory]; Buchholz et al AP(02)hp/01; Berges NPA(02), NPA(02)hp [and classical field theory]; Berges AIP(04)hp [intro]; Berges & Borsányi EPJA(06)ht/05-in [from first principles]; Zanella & Calzetta ht/06 [renormalization and damping]; Gasenzer & Pawlowski PLB(08) [functional renormalization-group approach]; Rammer 07; Calzetta & Hu 08; Kamenev 11 [functional approach]; Hack & Verch a1806 [interacting Klein-Gordon field, steady-state].
@ Other states: Nieto PLA(97)qp/96 [displaced / squeezed number states]; Sebawe Abdalla et al PS(08) [non-linear generalized geometric states]; Banisch et al CQG(13)-a1205 [states on timelike hypersurfaces].

Specific Theories > s.a. dirac theory; modified electromagnetism; QED; modified QED.
@ Scalar field: Shvedov ht/04 [covariant approach].
> Semiclassical theories: see qed phenomenology; semiclassical general relativity; semiclassical quantum gravity.

Related Topics and Properties > s.a. quantum fields in curved spacetime [Hadamard and other states] and effects in curved spacetime [vacuum].
@ Degree of polarization: Klimov et al PRA(05)qp [as distance from set of unpolarized states].
> Other topics: see effective quantum field theories; klein-gordon fields [symmetry reduction].

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