Submitted:
09 November 2025
Posted:
10 November 2025
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Abstract
Keywords:
1. Introduction
1.1. Motivation
1.2. Core Idea
1.3. Spin, Statistics, and Unified Origin
1.4. From Pre-Geometric Foam to Quantum Order
Dynamical Phases of the Chronon Ensemble
| Phase | Length scale | Order parameter | Dominant dynamics | Physical character |
|---|---|---|---|---|
| Pre-geometric | None (disordered) | Random causal noise | No metric, no excitations | |
| Planck | Local alignment | Soliton formation | Action quantization () | |
| Quantum | Stable phase field | Canonical and gauge oscillations | ; unified spin–statistics | |
| Macroscopic | Domain coherence | Mean-field alignment | Classical limit; decoherence |
1.5. Order Formation and Scale Invariance
1.6. Structure of the Paper

2. Chronon Field Theory: Pre-Geometric Dynamics
2.1. Fundamental Degrees of Freedom
2.2. Emergent Spacetime and Correlation Length
- Pre-geometric (): Strong fluctuations; no stable topology or excitations.
- Geometric (): Causal orientations align to form coherent solitonic structures stabilized by J and , constituting the first geometric degrees of freedom.
- Continuum emergence. Although defined on a discrete causal complex, the chronon field acts as a pre-geometric regulator. When , the continuum limit exhibits emergent Lorentz invariance and diffeomorphism symmetry [45,61]. The macroscopic smoothness of spacetime therefore reflects collective coherence of discrete causal elements, analogous to the emergence of hydrodynamic behavior from molecular discreteness.
3. Hierarchy of Dynamical Phases
3.1. Phase I: Pre-Geometric Regime ()
3.2. Phase II: Planck Regime ()
3.3. Phase III: Quantum Regime ()
3.4. Phase IV: Macroscopic Regime ()
- Hierarchical summary.with ℏ fixed at the Planck transition.
3.5. Control Parameter, Order Parameter, and the Role of
| Constant | Domain | Interpretation in Chronon Dynamics |
|---|---|---|
| Statistical | Converts information (entropy) into energy; quantifies microscopic disorder. | |
| ℏ | Geometric | Converts phase into action; fixed symplectic modulus of coherent causal order. |
4. Mathematical Structure of Quantization
4.1. Canonical Structure on Stabilized Domains
- Remark on statistics. The antisymmetry of defines phase-space orientation for both bosonic and fermionic sectors. Bose–Fermi differentiation arises from the topology of the configuration space: if its fundamental group admits a non-trivial double cover , the corresponding wavefunctional changes sign under rotation, producing half-integer spin and Fermi statistics [26,46].
4.2. Uncertainty and Minimal Action
4.3. Geometric Interpretation of
- Physical meaning. Geometrically, is the curvature modulus of the chronon bundle—the minimal flux of threading a closed loop of causal orientation. It originates from the first stable chronon soliton whose phase winding encloses one flux unit. All subsequent excitations propagate within this pre-established symplectic background, inheriting the same action quantum.
- Consequences. Because is quantized over closed surfaces, canonical commutation and spin–statistics relations arise from the topology of itself:Planck’s constant is therefore the minimal symplectic flux quantum of spacetime, a geometric invariant fixed by the topology of the chronon condensate.
4.4. Effective Inertia, Propagation Speed, and Quartic Stiffness
- Continuum limit. In coarse-grained form the Lagrangian density iswhere is the causal vorticity two-form. Here and J are temporal and spatial stiffnesses, enforces , and introduces a quartic vorticity stiffness that stabilizes finite-radius solitons. For -dimensional reductions one may consistently set ; in it is essential for regular solutions.
- Discrete realization. On the lattice,with forward differences . The continuum parameters relate asThe effective causal velocity defines the emergent light-cone structure, while sets the intrinsic soliton radius .
| Parameter | Role | Interpretation |
| J | Spatial stiffness | Aligns neighboring chronons; sets correlation length. |
| Temporal stiffness | Governs causal rotation; defines temporal coherence. | |
| Norm-pinning potential | Maintains ; stabilizes orientation. | |
| Quartic vorticity stiffness | Prevents soliton collapse; fixes finite soliton radius. | |
| Propagation speed | Determines causal cone and metric signature. |
5. Numerical Realization
5.1. Lattice Dynamics and Setup
5.2. Causal Soliton Formation and Diagnostics

5.3. Twist Stabilization and Core Growth

5.4. Emergence of the Soliton Core

5.5. Radial Contraction and Steady-State Structure

5.6. Quantitative Metrics and Scaling Consistency
- Core–strength stationarity. A linear fit to the late–time core–strength series yields a slope , i.e., numerically indistinguishable from zero at machine precision. We therefore treat the core as stationary on average (no secular drift).
- Core fraction of total twist. The stability index, defined as the core fraction , fluctuates but remains bounded, with a median and an interquartile range . This indicates a persistent, localized twist condensate embedded in a background of weaker vorticity.
- Alignment loss. The alignment proxy decreases modestly over the run; the net change is , reflecting episodic domain mergers rather than loss of global coherence.
- Lorentz–norm constraint. The constraint error is typically , with brief spikes temporally coincident with energy bursts; the error rapidly returns to the level after each event.
- Energy plateau (late time). The mean total energy over the late–time window is (code units).
| Quantity | Symbol / Definition | Measured Value |
|---|---|---|
| Integrated action | ||
| Emergent lattice Planck modulus | ||
| Effective per–site Planck constant | ||
| Plateau slope (core) | ||
| Mean energy (plateau) | ||
| Stability index (median core fraction) | ||
| Alignment loss | ||
| Lorentz–norm violation (typical) |
5.7. Summary of Numerical Findings
- Rapid boundary-induced alignment of chronon orientations.
- Emergence of a localized twist condensate obeying Derrick stabilization.
- Saturation of the effective action variance, defining a fixed quantum of causal coherence .
6. Physical Interpretation
6.1. as the Invariant Link Between Planck and Quantum Phases
6.2. Solitons as Geometric Carriers of Quantized Action
6.3. Quantum–Classical Continuum of Soliton Ensembles
6.4. Conceptual Synthesis
- The chronon field defines a discrete, pre-geometric substrate without intrinsic spacetime or metric.
- At the Planck correlation length , stable solitons form, each carrying one quantum of action ℏ.
- Ensembles of solitons generate quantum mechanics as a collective, coarse-grained theory.
- Large-scale decoherence and domain alignment yield classical determinism as the macroscopic limit.
7. Unified Origin of ℏ, Spin Quantization, and Fermi Statistics
7.1. Universal Curvature and the Chronon Symplectic Form
7.2. Emergent Spin from Internal Symplectic Curvature
7.3. Photon Spin as an Integer Curvature Quantum
- Goldstone excitation and symplectic flux. In the ordered quantum phase, global phase rotations of correspond to a spontaneously broken internal symmetry. Its massless collective excitation—the photon—is therefore a transverse oscillation of the phase field . Each photon mode carries a single quantum of the symplectic flux established by soliton condensation,representing one curvature quantum of the chronon bundle. The photon does not generate new topological winding; rather, it propagates existing symplectic curvature through the ordered medium, analogous to a phase wave transmitting quantized circulation in a superfluid.
- Spin and representation structure. Under rotation about the propagation axis by an angle , the circularly polarized photon modes transform aswith angular momentum operatorThe photon’s integer spin follows directly from the single-valued representation of supported by the simply connected fiber: each spatial rotation corresponds to one full curvature cycle carrying flux . This contrasts with fermionic solitons, whose half-integer spin arises from the double-cover topology , reversing orientation under a rotation.
- Unified curvature origin of quantization. Both fermions and photons thus derive their quantized angular momenta from the same geometric invariant: the minimal symplectic flux fixed at the Planck boundary. For solitons, this flux appears as a localized winding of causal orientation; for photons, as a propagating phase wave transporting one curvature quantum per polarization cycle. In either case, serves as the universal geometric modulus linking topological charge, spin quantization, and gauge propagation within a single chronon framework.
7.4. Two Distinct Antisymmetries
- Canonical antisymmetry — encoded in the symplectic form (30) and expressed algebraically byrepresenting the antisymmetry of conjugate variables under phase-space exchange. This property is geometric and applies universally to all dynamical fields.
- Exchange antisymmetry — a global topological property of the N-soliton configuration space , where denotes the coincidence set. The fundamental group determines the phase acquired upon soliton exchange. In three spatial dimensions,which admits two one-dimensional unitary representations: the trivial (bosonic) and the sign (fermionic) representation. In the latter case the many-soliton wavefunction obeysyielding Pauli exclusion and Fermi statistics [26,41].
7.5. Synthesis: One Curvature, Three Manifestations
In Chronon Field Theory, ℏ is not an imposed constant but the curvature modulus of the temporal symplectic manifold, manifesting identically in the quantization of action, spin, and statistics.

8. Discussion and Future Directions
8.1. Matter as the Source of Quantization
- Photon as an inherited quantum. Although photons are not solitons, their quantized polarization modes depend on the preexisting ordered phase of the chronon condensate. Once is fixed by soliton formation, phase fluctuations of the order parameter propagate as Goldstone-like waves of the chronon phase [46,78]. Each photon mode carries one quantum of the established curvature flux but does not create new quanta—the photon is the messenger, not the origin, of quantization.
- Unified symplectic order. Matter and quantization thus represent dual aspects of a single symplectic order. Solitonic curvature makes nonzero; this same curvature in turn governs quantum behavior for both matter and radiation. Quantization becomes the emergent geometric consequence of matter formation—the moment when curvature, causality, and discrete action become inseparable features of the same underlying spacetime order.
8.2. Reinterpreting the Quantum Vacuum
8.3. Finite Core Structure of Black Holes
8.4. Reinterpretation of Blackbody Radiation
8.5. Extension to Curved and Dynamical Geometries
8.6. Connection to Holography and Information
8.7. Universality of ℏ and Entropic Relations
8.8. Toward a Unified Vision of Matter and Geometry
- ℏ is a curvature invariant of the Planck transition, not a postulate.
- Quantum mechanics is the hydrodynamic limit of coherent chronon excitations.
- Gravity and curvature arise from variations in chronon connectivity.
- Fermi–Bose statistics reflect topological coverings of the same symplectic manifold.
- Classical determinism corresponds to full causal-phase alignment.
Appendix A. Existence and Stability of Solitonic Excitations
Appendix A.1. Energy Functional and Field Equations
Appendix A.2. Derrick Scaling and Stability
Appendix A.3. Topological and Energetic Interpretation
- Alignment stiffnessJ: sets the causal gradient energy scale and determines propagation speed .
- Norm pinning: enforces the Lorentzian unit constraint , ensuring causal coherence.
- Topological stiffness: breaks scale invariance, generates finite radius , and prevents collapse.
Appendix A.4. Minimal Action and Identification with ℏ geom

Appendix B. Rigorous Statement and Proof of the Symplectic Gap
Setup
Stability Hypotheses
- (S1)
- C is positive, self-adjoint, trace-class on H.
- (S2)
- J is bounded, invertible, and skew-adjoint.
- (S3)
- Coercivity: there exists with for all .
- (S4)
- RG stability: under admissible coarse-graining , the constants and subspace can be chosen so that , .
Main Result
Operational Corollary
- Relation to Appendix A. Appendix A demonstrates how quantized action arises dynamically from stable solitons of the chronon field, while the present appendix proves that, once such a phase exists, the corresponding symplectic unit ℏ remains invariant under coarse-graining. Together they establish both the physical origin and the mathematical stability of the Planck constant within Chronon Field Theory.
Appendix C. Variational Analysis of the Minimal Soliton Action
Appendix C.1. Analytic Derivation: Bogomolny Bound in 1+1 D
Appendix C.2. Numerical Verification

Appendix C.3. Embedding into the 3+1 D Chronon Lattice
Appendix C.4. Physical Interpretation
References
- Araki, H.; Woods, E.J. Representations of the Canonical Commutation Relations Describing a Nonrelativistic Infinite Free Bose Gas. J. Math. Phys. 1970, 4, 637–662. [Google Scholar] [CrossRef]
- Ashtekar, A. New variables for classical and quantum gravity. Phys. Rev. Lett. 1986, 57, 2244. [Google Scholar] [CrossRef]
- Barceló, C.; Liberati, S.; Visser, M. Analog gravity from Bose–Einstein condensates. Class. Quantum Grav. 2001, 18, 1137. [Google Scholar] [CrossRef]
- Bekenstein, J.D. Black Holes and Entropy. Phys. Rev. D 1973, 7, 2333–2346. [Google Scholar] [CrossRef]
- Berry, M.V. Quantal phase factors accompanying adiabatic changes. Proc. R. Soc. Lond. A 1984, 392, 45. [Google Scholar]
- Binder, K.; Landau, D.P. Phase diagrams and critical behavior in Monte Carlo simulations. Phys. Rev. B 1984, 30, 1477, see also A Guide to Monte Carlo Simulations in Statistical Physics, 2nd ed. (Cambridge University Press, 2000).. [Google Scholar] [CrossRef]
- Bogomolny, E.B. Stability of Classical Solutions. Sov. J. Nucl. Phys. 1976, 24, 449–454. [Google Scholar]
- Bohr, N. On the Constitution of Atoms and Molecules. Philos. Mag. 1913, 26, 1. [Google Scholar] [CrossRef]
- Bombelli, L.; Lee, J.; Meyer, D.; Sorkin, R. Space-time as a causal set. Phys. Rev. Lett. 1987, 59, 521. [Google Scholar] [CrossRef] [PubMed]
- Bombelli, L.; Lee, J.; Meyer, D.; Sorkin, R. Space-Time as a Causal Set. Phys. Rev. Lett. 1987, 59, 521–524. [Google Scholar] [CrossRef]
- Bratteli, O.; Robinson, D.W. , Operator Algebras and Quantum Statistical Mechanics, Vol. 1–2, Springer, 1987.
- Calogero, F. Quantum mechanics as a statistical theory. Phys. Lett. A 1997, 228, 335. [Google Scholar] [CrossRef]
- Campbell, D.K.; Schonfeld, J.F.; Wingate, C.A. Resonance Structure in Kink–Antikink Interactions in ϕ4 Theory. Physica D 1983, 9, 1–32. [Google Scholar] [CrossRef]
- Caticha, A. Entropic dynamics, time, and quantum theory. J. Phys. A: Math. Theor. 2011, 44, 225303. [Google Scholar] [CrossRef]
- Creutz, M. , Quarks, Gluons and Lattices (Cambridge University Press, 1983).
- Creutz, M. Overrelaxation and Monte Carlo simulation. Phys. Rev. D 1987, 36, 515. [Google Scholar] [CrossRef]
- Dashen, R.F.; Hasslacher, B.; Neveu, A. Nonperturbative Methods and Extended-Hadron Models in Field Theory. II. Two-Dimensional Models and Extended Hadrons. Phys. Rev. D 1974, 10, 4130–4138. [Google Scholar] [CrossRef]
- Derrick, G.H. Comments on nonlinear wave equations as models for elementary particles. J. Math. Phys. 1964, 5, 1252. [Google Scholar] [CrossRef]
- Dirac, P.A.M. The Principles of Quantum Mechanics (Oxford University Press, 1930).
- Dirac, P.A.M. The Lagrangian in Quantum Mechanics. Physikalische Zeitschrift der Sowjetunion 1933, 3, 64. [Google Scholar]
- Dirac, P.A.M. , The Principles of Quantum Mechanics, 4th ed. (Oxford University Press, 1958).
- Dowker, F. Causal Sets and the Deep Structure of Spacetime. Gen. Rel. Grav. 2005, 45, 1651–1667. [Google Scholar] [CrossRef]
- Elze, H.-T. Quantum features emerging in a classical spacetime structure. Phys. Rev. A 2014, 89, 012111. [Google Scholar] [CrossRef]
- Faddeev, L.; Niemi, A.J. Stable Knot-like Structures in Classical Field Theory. Nature 1997, 387, 58–61. [Google Scholar] [CrossRef]
- Feynman, R.P. Space-Time Approach to Non-Relativistic Quantum Mechanics. Rev. Mod. Phys. 1948, 20, 367. [Google Scholar] [CrossRef]
- Finkelstein, D.; Rubinstein, J. Connection between Spin, Statistics, and Kinks. J. Math. Phys. 1968, 9, 1762. [Google Scholar] [CrossRef]
- Folland, G.B. , Harmonic Analysis in Phase Space (Princeton University Press, 1989).
- Haken, H. , Synergetics: An Introduction. Nonequilibrium Phase Transitions and Self-Organization in Physics, Chemistry and Biology, Springer, 3rd ed., 1983.
- Hall, M.J.W.; Reginatto, M. Quantum mechanics from a Heisenberg-type inequality. J. Phys. A: Math. Gen. 2002, 35, 3289. [Google Scholar] [CrossRef]
- Hestenes, D. The zitterbewegung interpretation of quantum mechanics. Found. Phys. 2010, 40, 1. [Google Scholar] [CrossRef]
- Hollands, S.; Wald, R.M. , “Quantum Field Theory is Ultimately Local and Covariant: Renormalization in Curved Spacetime,” Commun. Math. Phys. 2005, 257, 589–620. [Google Scholar]
- Hossenfelder, S. Experimental Search for Quantum Gravity. Class. Quantum Grav. 2010, 27, 114001. [Google Scholar]
- Hossenfelder, S. Emergent Spacetime. Foundations of Physics 2013, 43, 1295–1308. [Google Scholar]
- Jackiw, R.; Rebbi, C. Solitons with Fermion Number 1/2. Phys. Rev. D 1976, 13, 3398. [Google Scholar] [CrossRef]
- Jacobson, T. Thermodynamics of Spacetime: The Einstein Equation of State. Phys. Rev. Lett. 1995, 75, 1260–1263. [Google Scholar] [CrossRef]
- Jaynes, E.T. “Information Theory and Statistical Mechanics. Physical Review 1957, 106, 620–630. [Google Scholar] [CrossRef]
- Joos, E. , Decoherence and the Appearance of a Classical World in Quantum Theory (Springer, 2003).
- Kadanoff, L.P. More is the same; phase transitions and mean field theories. J. Stat. Phys. 2009, 137, 777. [Google Scholar] [CrossRef]
- Kogut, J.B.; Susskind, L. Hamiltonian formulation of Wilson’s lattice gauge theories. Phys. Rev. D 1975, 11, 395. [Google Scholar] [CrossRef]
- Konopka, T.; Markopoulou, F.; Smolin, L. Quantum Graphity. Phys. Rev. D 2008, 77, 104029. [Google Scholar] [CrossRef]
- Laidlaw, M.G.G.; DeWitt, C.M. Feynman functional integrals for systems of indistinguishable particles. Phys. Rev. D 1971, 3, 1375. [Google Scholar] [CrossRef]
- Landau, L.D.; Lifshitz, E.M. , Statistical Physics, Part 1, Pergamon Press, 3rd ed., 1980.
- Landauer, R. Irreversibility and Heat Generation in the Computing Process. IBM J. Res. Dev. 1961, 5, 183–191. [Google Scholar] [CrossRef]
- Laughlin, R.B. , A Different Universe: Reinventing Physics from the Bottom Down (Basic Books, 2005).
- Li, B. , “Emergence and Exclusivity of Lorentzian Signature and Unit–Norm Time from Random Chronon Dynamics,” Rep. Adv. Phys. Sci., 2025, 2025. [CrossRef]
- Li, B. , “Emergent Gravity and Gauge Interactions from a Dynamical Temporal Field,” Rep. Adv. Phys. Sci. 2025, 9, 2550017. [Google Scholar] [CrossRef]
- Lloyd, S. Ultimate Physical Limits to Computation. Nature 2000, 406, 1047–1054. [Google Scholar] [CrossRef]
- Loll, R. Quantum Gravity from Causal Dynamical Triangulations: A Review. Class. Quantum Grav. 2019, 37, 013002. [Google Scholar] [CrossRef]
- Manton, N.; Sutcliffe, P. , Topological Solitons, Cambridge University Press, 2004.
- Markopoulou, F. Quantum causal histories. Class. Quantum Grav. 2009, 24, 3699. [Google Scholar] [CrossRef]
- Nelson, E. Derivation of the Schrödinger equation from Newtonian mechanics. Phys. Rev. 1966, 150, 1079. [Google Scholar] [CrossRef]
- Oriti, D. The Universe as a Quantum Gravity Condensate. Comptes Rendus Physique 2018, 18, 235. [Google Scholar] [CrossRef]
- Padmanabhan, T. Thermodynamical Aspects of Gravity: New Insights. Rep. Prog. Phys. 2010, 73, 046901. [Google Scholar] [CrossRef]
- Parisi, G.; Wu, Y.-S. Perturbation theory without gauge fixing. Sci. Sin. 1981, 24, 483. [Google Scholar]
- Planck, M. Ueber das Gesetz der Energieverteilung im Normalspectrum. Ann. Phys. 1901, 4, 553. [Google Scholar] [CrossRef]
- Prasad, M.K.; Sommerfield, C.M. Exact Classical Solution for the ’t Hooft–Polyakov Monopole and the Julia–Zee Dyon,” Phys. Rev. Lett. 1975, 35, 760–762. [Google Scholar] [CrossRef]
- Press, W.H.; Teukolsky, S.A.; Vetterling, W.T.; Flannery, B.P. , Numerical Recipes in C: The Art of Scientific Computing, Cambridge Univ. Press, 1992.
- Prigogine, I.; Nicolis, G. , Self-Organization in Nonequilibrium Systems: From Dissipative Structures to Order Through Fluctuations, Wiley, 1978.
- Reed, M.; Simon, B. , Methods of Modern Mathematical Physics, Vol. II: Fourier Analysis, Self-Adjointness, Academic Press, 1975.
- Regge, T. General Relativity Without Coordinates. Nuovo Cimento 1961, 19, 558–571. [Google Scholar] [CrossRef]
- Rovelli, C. , Quantum Gravity (Cambridge University Press, 2011).
- Simon, B. , Functional Integration and Quantum Physics, Academic Press, 1979.
- Simon, R. Peres–Horodecki Separability Criterion for Continuous Variable Systems. Phys. Rev. Lett. 2000, 84, 2726–2729. [Google Scholar] [CrossRef]
- Skyrme, T.H.R. , “A Nonlinear Field Theory,” Proceedings of the Royal Society A 1961, 260, 127–138. 260.
- Skyrme, T.H.R. A Nonlinear Field Theory. Proc. Roy. Soc. A 1961, 260, 127–138. [Google Scholar]
- Skyrme, T.H.R. A Unified Field Theory of Mesons and Baryons. Nucl. Phys. 1962, 31, 556–569. [Google Scholar] [CrossRef]
- Smolin, L. The case for background independence. hep-th/0507235.
- Smolin, L. The Case for Background Independence. in The Structural Foundations of Quantum Gravity, edited by D. Rickles et al., Oxford University Press, 2006.
- Susskind, L. The World as a Hologram. J. Math. Phys. 1995, 36, 6377–6396. [Google Scholar] [CrossRef]
- ’t Hooft, G. Dimensional Reduction in Quantum Gravity. in Salamfestschrift, World Scientific, 1993.
- Tinkham, M. , Introduction to Superconductivity, 2nd ed. (McGraw–Hill, 1996).
- Verlinde, E. On the Origin of Gravity and the Laws of Newton. JHEP 2011, 2011, 29. [Google Scholar] [CrossRef]
- Volovik, G.E. , The Universe in a Helium Droplet (Oxford Univ. Press, 2003).
- Wallace, D. , The Emergent Multiverse: Quantum Theory According to the Everett Interpretation (Oxford Univ. Press, 2012).
- Weinberg, S. “The Cosmological Constant Problem,” Rev. Mod. Phys. 1989, 61, 1–23. [Google Scholar] [CrossRef]
- Weinberg, S. Quantum mechanics without state vectors. Phys. Rev. A 2014, 90, 042102. [Google Scholar] [CrossRef]
- Wheeler, J.A. Geometrodynamics and the Issue of the Final State. in Relativity, Groups and Topology, eds. B. DeWitt and C. DeWitt (Gordon and Breach, 1964).
- Wilczek, F. Quantum Time Crystals. Phys. Rev. Lett. 2012, 109, 160401. [Google Scholar] [CrossRef] [PubMed]
- Williamson, J. On the Algebraic Problem Concerning the Normal Forms of Linear Dynamical Systems. Amer. J. Math. 1936, 58, 141–163. [Google Scholar] [CrossRef]
- Witten, E. Dyons of Charge e/2. Phys. Lett. B 1979, 86, 283–287. [Google Scholar] [CrossRef]
- Woodhouse, N.M.J. , Geometric Quantization, 2nd ed. (Oxford University Press, 1992).
- Zurek, W.H. Decoherence, einselection, and the quantum origins of the classical. Rev. Mod. Phys. 2003, 75, 715. [Google Scholar] [CrossRef]
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