|  Discrete Spacetime Models and Phenomenology | 
In General
  > s.a. 3D quantum gravity; canonical quantum gravity;
  causal sets; Discrete Models [matter];
  physics [ultimate theory proposals].
  * Models: One possible way to group them into different types is:
    - Combinatorial, non-topological versions, such as posets or graphs;
    - Topological versions, such as simplicial or cell complexes;
    - Piecewise-flat versions, such
    as Regge calculus, dynamical triangulations or twisted geometries;
    To establish a connection with continuum geometry, each proposal of one of
    the above types seems to need the ones below as an intermediate step.
  @ Spin networks and lqg: in Penrose 66,
    pr(66), in(70),
    in(71), in(72),
    in(79);
    Hasslacher & Perry PLB(81);
    Moussouris PhD(83);
    Kauffman IJMPA(90);
    LaFave gq/93;
    Zapata GRG(98)gq/97;
    Dupuis et al Sigma(12)-a1204 [rev];
    Haggard et al PRD(13)-a1211 [twisted geometry, spin connection];
    > s.a. spin-foam models.
  @ Graphs / network models:
    Dadic & Pisk IJTP(79);
    Antonsen PhD(92),
    IJTP(94);
    Requardt ht/96,
    ht/96,
    ht/96-in [random graphs],
    JPA(98)ht,
    gq/99,
    CQG(00)gq/99,
    Requardt & Roy CQG(01)gq/00 [and random metric space];
    Requardt gq/03;
    Markopoulou & Smolin PRD(04)gq/03;
    Konopka et al ht/06 [complete lattice, phase transition];
    Efremov et al a0706 [BF theory on graph cobordisms];
    Kan PTPS-a0712 [and cosmology];
    Wall CQG(13)-a1201 [discrete causal dynamics];
    Baird JGP(13);
    Hossenfelder CQG(15)-a1504 [no-go theorem for Poincaré-invariant networks];
    Trugenberger PRE(15)-a1507 [and phase transition];
    Bianconi & Rahmede SciRep(15)-a1506 [Complex Quantum Network Manifolds],
    PRE(16)-a1511 [network geometry with flavor, NGF];
    Lombard PRD(17)-a1602 [Metropolis network evolution simulations and emergent properties];
    Trugenberger JHEP(17)-a1610;
    Vanchurin FP(18)-a1706 [information flow graph];
    Kelly & Trugenberger JPCS(19)-a1811 [random graphs];
    Tee a1901 [quantum mesh];
    Shoshany PRD(19)-a1904 [3D, discrete phase space].
  @ Quantum graphity:
    Konopka et al ht/06 [proposal];
    Konopka et al PRD(08)-a0801 [locality];
    Konopka PRD(08)-a0805 [statistical mechanics, role of matter];
    Hamma et al PRD(10) [entanglement of matter and geometry];
    Caravelli & Markopoulou PRD(11)-a1008 [low-temperature properties];
    Hamma & Markopoulou NJP(11)-a1011 [rev];
    Caravelli a1110-proc;
    Caravelli & Markopoulou PRD(12)-a1201 [model of quantum foam];
    Markopoulou LNCS(12)-a1201 [and quantum computation];
    Quach et al PRD(12)-a1203 [formation of metastable defects at domain boundaries];
    Wilkinson & Greentree PRD(14)-a1409 [energetics],
    PRD(15)-a1506 [hypervalence term in the Hamiltonian];
    Requardt & Rastgoo JCA-a1501 [compared to dynamic cellular network approach];
    Tee a1903 [quantum mesh dynamics];
    > s.a. graphs in physics [graph evolution models].
  @ Cellular automaton: Feynman;
    Finkelstein PR(69);
    't Hooft NPB(90),
    et al NPB(92),
    gq/93;
    Requardt ht/95 [varying connections];
    Zizzi gq/01-conf,
    gq/01,
    in(04)gq/03 [computational network];
    Eakins & Jaroszkiewicz gq/03.
  @ Fuzzy: Francis phy/99-wd,
    phy/99 [and particles];
    Zizzi MPLA(05)gq/04-in [N-qubits on quantum space].
Wolfram model: Wolfram a2004;
    Gorard a2004;
    Rodríguez a2006;
    > s.a. causal set dynamics.
  @ Other models: Noyes 01;
    Galiautdinov PhD-IJTP(02)ht [and spin-1/2 particles];
    Abramsky in(05)-a1111 [topological universe of finitary sets];
    Buniy et al PLB(05)ht [and discrete Hilbert space];
    Tanaka FPL(06)ht/05 [Buniy-Hsu-Zee model and Yang's quantized spacetime algebra];
    Zachos IJMPA(80)-a0710 [umbral deformation];
    Deveaux & Fernández JSP(10)-a1002 [partially ordered chains];
    Finster & Grotz ATMP(12)-a1107,
    Farrelly & Short PRA(14)-a1303 [causal fermion system],
    PRA(14)-a1312 [relativistic dynamics from particle in a discrete spacetime];
    Cirilo-Lombardo & Prudencio IJGMP(14)-a1309 [supergeometry];
    Ariwahjoedi et al a1607 [simplices];
    De et al IJMPD(19)-a1903 [space-time-matter atoms];
    Chirco et al PRD(19)-a1811 [tetrahedra, and maximum entropy principle];
    Chirco & Kotecha LNCS(19)-a1906 [statistical framework];
    > s.a. bose-einstein condensates; non-commutative geometry
      [including Snyder's proposal]; quantum spacetime models [categorical].
  > Related concepts: see approaches to
    quantum gravity; discretized gravity; gravitational
    thermodynamics ["atoms of spacetime"]; renormalization.
Particles and Fields
  > s.a. diffusion; Discretization;
  graphs in physics; green functions;
  laplace operator.
  @ General references: Dimakis et al JMP(95)ht/94 [fields];
    Bojowald & Date CQG(04)gq/03 [consistency conditions on differential equations];
    Bastin & Kilmister 09;
    Elze JPCS(09)-a0906;
    Weinstein a1101
      [fixed number of degrees of freedom per co-moving volume, cosmology and variation of constants];
    Sochichiu TMP(15)-a1403 [networks of fermionic states];
    Canarutto a1404-FQXi;
    Dündar & Arık a1808 [?];
    Rogers a1902-conf
      [discrete vs continuum theories, history].
  @ Quantum field theory: Yamamoto PRD(85) [bosons and fermions];
    Finster ATMP(07)mp/06,
    JPCS(07)ht/06,
    in(09)-a0712 [fermions];
    Sverdlov a1108;
    Farrelly & Short PRA(14)-a1303 [fermions];
    Berger & Yamatsu PRD(13);
    Kar et al MPLA(13)-a1305.
  > Theories in discrete settings:
    see dirac fields; electromagnetism in curved spacetime;
    higher-dimensional gravity [discrete extra dimensions];
    modified quantum field theories; path-integral
    quantum theory; quantum particles; wave equations.
Consequences / Phenomenology
  > s.a. quantum-gravity phenomenology; singularities;
  entropy bounds; ultra-high-energy cosmic rays.
  @ Observability: Amelino-Camelia CzJP(98)gq-proc [discrete lengths and areas];
    Rivero gq/06 [consequences];
    Dreyer a0805 [cosmological perturbation spectrum];
    Dreyer a1307 [cmb spectrum];
    Brun & Mlodinow a1802 [matter interferometry];
    Hossenfelder CQG+(18) [violation of energy-momentum conservation];
    Das et al a2006
      [quantized lengths from GUP-modified quantum theory].
  @ Compatible with Lorentz symmetry: 
    Rovelli & Speziale PRD(03)gq/02;
    Dowker et al MPLA(04)gq/03 [massive-particle diffusion on causal set background];
    Livine & Oriti JHEP(04)gq [toy model + DSR quantum geometry];
    Bombelli et al MPLA(09)gq/06,
    comment Kent CQG(18)-a1803 [no breaking in random sprinklings];
    Bonder a0801-conf [model, and Newtonian limit];
    Burton a0912;
    Bonder & Sudarsky AIP(10)-a1003 [model and experimental setup];
    Aguilar et al PRD(13)-a1210 [phenomenological signatures];
    Jizba & Scardigli EPJC(13)-a1301,
    FP(14)
      [emergence of various symmetries at larger scales];
    Dowker & Sorkin CQG(20)-a1909.
  @ Lorentz symmetry, other:
    Sidharth IJTP(04);
    Vergeles NPB(06)ht/05;
    Henson gq/06;
    Hossenfelder CQG(15)-a1504 [no-go theorem];
    > s.a. lorentz symmetry [emergence]
      and modifications.
  @ Continuum limit: Ling MPLA(05)gq/03 [and singularities];
    Requardt IJGMP(06)mp/05 [and distance between metric spaces];
    > s.a. canonical quantum gravity [discreteness corrections].
  @ Related topics: Badiali JPA(05) [and statistical thermodynamics];
    Bachmat gq/07 [applications];
    Gao IJTP(10)-a1001 [and superposition of spacetimes];
    Kauffman a1109
      [discrete measurements and derivatives, non-commutativity and the imaginary unit];
    Chamseddine MPLA(16)-a1606-proc [non-commutative space and grand unified models];
    > s.a. kinematics of special relativity [length contraction].
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