\begin{longtable}{p{0.15\textwidth}|b{0.425\textwidth}|b{0.425\textwidth}}
\caption{Research areas, their top-words, and their correlation with a standard classification (PACS).}
\label{table:research_areas}\\
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                          Research area &                                                                                                                                                                                                                                           Top words &                                                                                                                                                                                                               Most correlated PACS categories \\
\midrule
\endfirsthead
\caption[]{Research areas, their top-words, and their correlation with a standard classification (PACS).} \\
\toprule
                          Research area &                                                                                                                                                                                                                                           Top words &                                                                                                                                                                                                               Most correlated PACS categories \\
\midrule
\endhead
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\multicolumn{3}{r}{{Continued on next page}} \\
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\endfoot

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\endlastfoot
                 Actions and Invariance &         action, transformation, lorentz, invariant, dirac, formulation, generalized, hamiltonian, invariance, covariant, invariant\_action, bv, canonical, covariance, quantization, principle, version, translation, lorentz\_violating, formalism &                                             \shortstack[l]{Noncommutative field theory (0.27)\\ Lagrangian and Hamiltonian approach (0.24)\\ Lorentz and Poincaré invariance (0.22)\\ Gauge field theories (0.22)\\ Quantum mechanics (0.16)}\\ \hline
  Black Holes and Gravitational Physics &                                     hole, black\_hole, black, gravity, horizon, geometry, spacetime, spacetimes, gravitational, einstein, hair, thermodynamics, curvature, relativity, microstates, bh, metric, schwarzschild, entropy, space\_time &                                           \shortstack[l]{Quantum aspects of black holes, [...] (0.53)\\ Classical black holes (0.42)\\ Physics of black holes (0.33)\\ Exact solutions (0.23)\\ Higher-dimensional black holes, [...] (0.22)}\\ \hline
 Chiral Symmetry and Fermion Structures &                                                     chiral, su, fermion, structure, lattice, topological, finite, anomalous, abelian, condensate, global, dynamical, vortex, color, breaking, anomaly, flavor, compact, chiral\_symmetry, composite &                                           \shortstack[l]{Chiral symmetries (0.24)\\ Lattice gauge theory (0.23)\\ General properties of QCD [...] (0.20)\\ Lattice QCD calculations (0.15)\\ Spontaneous and radiative symmetry [...] (0.14)}\\ \hline
                Cosmology and Inflation &                         cosmological, inflation, cosmic, universe, inflationary, cosmology, gravitational, planck, tension, hubble, era, primordial, cmb, inflationary\_universe, bicep2, epoch, inhomogeneity, cosmic\_string, today, quintessence &                                                        \shortstack[l]{Particle-theory and field-theory [...] (0.58)\\ Cosmology (0.36)\\ Observational cosmology (including [...] (0.30)\\ Dark energy (0.29)\\ Background radiations (0.23)}\\ \hline
    Critical Points and Renormalization &                                                point, massive, physical, critical, renormalization, fermionic, fixed\_point, existence, massless, fixed, dynamical, complex, specific, free, zero, various, unphysical, ultraviolet, view, possible &                                                \shortstack[l]{Renormalization group evolution of [...] (0.24)\\ Renormalization (0.20)\\ Renormalization group methods (0.17)\\ Renormalization-group theory (0.12)\\ Quantum gravity (0.09)}\\ \hline
              Dark Matter and Neutrinos &                                                neutrino, matter, dark, dark\_matter, dm, candidate, sun, majorana, observed, earth, detection, leptogenesis, mu\_tau, neutron, sub\_gev, asymmetric, observation, neutrino\_mass, sterile, prospect &                                                                  \shortstack[l]{Neutrino mass and mixing (0.55)\\ Dark matter (0.53)\\ Non-standard-model neutrinos, [...] (0.33)\\ Ordinary neutrinos (0.24)\\ Neutrino interactions (0.23)}\\ \hline
  Decay Processes and Experimental Data &                                                      decay, data, channel, measurement, asymmetry, process, gamma, experimental, experimental\_data, leptonic, tau, ratio, collaboration, tau\_, width, observables, bound, mixing, kaon, available &                               \shortstack[l]{Decays of bottom mesons (0.40)\\ Decays of bottom mesons (0.27)\\ Bottom mesons (|B|>0) (0.22)\\ Determination of Cabibbo-Kobayashi [...] (0.19)\\ Decays of J/ψ, Υ, and other quarkonia (0.19)}\\ \hline
  Hadronic Processes and Cross Sections &                  distribution, collision, cross\_sections, section, production, cross, parton, hadron, cross\_section, hadronic\_collision, partonic, proton, event, transverse, prediction, inclusive, tomography, process, scattering, kinematics & \shortstack[l]{Perturbative calculations (0.31)\\ Total and inclusive cross sections [...] (0.28)\\ Inclusive production with [...] (0.27)\\ Polarization in interactions and [...] (0.26)\\ Quarks, gluons, and QCD in nuclear [...] (0.24)}\\ \hline
       Higgs and Standard Model Physics &                                             higgs, boson, standard, lhc, sm, standard\_model, tev, collider, top, physic, electroweak, mssm, search, phenomenology, deviation, higgs\_boson, cern\_lhc, discovery, extension, supersymmetric\_model &                                                \shortstack[l]{Extensions of electroweak Higgs sector (0.37)\\ Non-standard-model Higgs bosons (0.31)\\ Supersymmetric models (0.31)\\ Standard-model Higgs bosons (0.28)\\ Top quarks (0.27)}\\ \hline
  Holography and Conformal Field Theory & boundary, conformal, holographic, higher, holography, bulk, logarithmic, cfts, dimensional, cft, ad, entropy, boundary\_condition, asymptotic, entanglement\_entropy, stress, conformal\_field\_theory, boundary\_field, higher\_spin, entanglement &               \shortstack[l]{Conformal field theory, algebraic [...] (0.31)\\ Gauge/string duality (0.28)\\ Theory of quantized fields (0.16)\\ Entanglement and quantum nonlocality (0.15)\\ Entanglement measures, witnesses, [...] (0.14)}\\ \hline
        Magnetic and Electric Phenomena &                     magnetic, current, experiment, light, electron, photon, moment, electric, future, mechanism, production, electromagnetic, radiative, magnetic\_field, polarization, radiation, flux, direction, bremsstrahlung, electric\_field &                                                     \shortstack[l]{Specific calculations (0.28)\\ Electric and magnetic moments (0.26)\\ Quantum electrodynamics (0.14)\\ Experimental tests (0.14)\\ Optical tests of quantum theory (0.13)}\\ \hline
   Phase Transitions and Thermodynamics &                          phase, temperature, transition, system, relativistic, plasma, chemical, dynamic, density, viscosity, gas, correlation, non\_equilibrium, hadronic\_phase, response, fluctuation, transport, droplet, property, equilibrium &                                    \shortstack[l]{Quark-gluon plasma (0.41)\\ Finite-temperature field theory (0.30)\\ Quark deconfinement, quark-gluon [...] (0.30)\\ Relativistic heavy-ion collisions (0.25)\\ Hydrodynamic models (0.20)}\\ \hline
QCD Amplitudes and Perturbative Methods &                                        amplitude, qcd, integral, perturbative, gluon, approximation, evaluation, diagram, rule, feynman, one\_loop, sum, vertex, approach, loop, diagrammatic, nonperturbative, propagator, formalism, prescription &                              \shortstack[l]{General properties of perturbation [...] (0.29)\\ Perturbative calculations (0.21)\\ Other nonperturbative calculations (0.16)\\ General properties of QCD [...] (0.16)\\ Renormalization (0.15)}\\ \hline
         Quantum Operators and Algebras &                               quantum, operator, matrix, group, representation, algebra, element, product, quantum\_field, character, finite\_dimensional, basis, family, invariant, spin, commutator, eigenvectors, structure, arbitrary, discrete &                                                                         \shortstack[l]{Algebraic methods (0.27)\\ Quantum groups (0.19)\\ Integrable systems (0.18)\\ Lie algebras of Lie groups (0.15)\\ Noncommutative field theory (0.13)}\\ \hline
            Quarks and Hadronic Physics &                                                                 quark, qcd, meson, baryon, light\_quark, diquarks, pion, nucleon, \_meson, mev, form\_factors, strange, chiral, hadronic, width, rho, constituent, heavy\_baryon, framework, bottom &                           \shortstack[l]{Chiral Lagrangians (0.27)\\ Glueball and nonstandard multi- [...] (0.25)\\ Other nonperturbative calculations (0.23)\\ Hadron mass models and calculations (0.22)\\ Relativistic quark model (0.22)}\\ \hline
                Solutions and Equations &                                    solution, equation, vacuum, condition, background, problem, wave, evolution, constant, flow, singularity, negative, configuration, domain, stability, initial, instability, bubble, initial\_condition, unstable &                \shortstack[l]{Extended classical solutions; [...] (0.21)\\ Exact solutions (0.17)\\ Nonlinear or nonlocal theories and [...] (0.12)\\ Particle-theory and field-theory [...] (0.10)\\ Gravity in more than four [...] (0.10)}\\ \hline
         String Theory and Supergravity &                          string, superstring, subsector, supergravity, deformation, modulus, superpotentials, super, instantons, duality, six\_dimensional, sigma\_models, compactifications, heterotic, mathcaln, twistor, n1, duals, dual, circle &                                                                                            \shortstack[l]{Strings and branes (0.30)\\ Supergravity (0.30)\\ Compactification and four- [...] (0.27)\\ Supersymmetry (0.24)\\ D branes (0.21)}\\ \hline
           Supersymmetry and Dimensions &                                                        dimension, scale, supersymmetric, sector, number, supersymmetry, flavor, loop, physic, violation, minimal, level, extra, extra\_dimension, extension, susy, flavour, wilson, group, breaking &                                \shortstack[l]{Supersymmetric models (0.33)\\ Unified theories and models of [...] (0.22)\\ Supersymmetry (0.18)\\ Unification of couplings; mass relations (0.18)\\ Unified field theories and models (0.13)}\\ \hline
                        Uninterpretable &                                                         form, spectrum, mode, relation, factor, perturbation, example, formula, class, feature, power, property, index, spectral, behavior, application, behaviour, universal, dispersion, quantity &                                                 \shortstack[l]{Electromagnetic form factors (0.15)\\ Dispersion relations (0.09)\\ Particle-theory and field-theory [...] (0.09)\\ Gravitational waves (0.07)\\ Background radiations (0.06)}\\ \hline
                        Uninterpretable &                          scalar, potential, effective, tensor, vector, scalar\_field, part, effective\_field, sigma, perturbation, linear, lagrangian, phi, effective\_potential, expectation, kinetic, free, value, effective\_field\_theory, real &                                                \shortstack[l]{Particle-theory and field-theory [...] (0.10)\\ Modified theories of gravity (0.08)\\ Chiral Lagrangians (0.08)\\ Quantum fields in curved spacetime (0.08)\\ Cosmology (0.07)}\\ \hline
                        Uninterpretable &                                                           general, first, small, special, exact, classical, explicit, particular, symmetric, second, relevant, non\_linear, linear, flat, asymptotic, complete, full, certain, double, non\_trivial &                                    \shortstack[l]{Exact solutions (0.13)\\ Modified theories of gravity (0.11)\\ Nonlinear or nonlocal theories and [...] (0.10)\\ Extended classical solutions; [...] (0.10)\\ Classical black holes (0.09)}\\ \hline
                        Uninterpretable &                                      approach, analysis, method, work, recent, study, paper, previous, numerical, theoretical, prediction, consistent, formalism, comparison, calculation, technique, systematic, full, progress, systematic\_study &                                         \shortstack[l]{Perturbative calculations (0.05)\\ Alternative approaches (0.05)\\ Excited states: methodology (0.05)\\ Data analysis: algorithms and [...] (0.05)\\ Finite-difference methods (0.05)}\\ \hline
                        Uninterpretable &                                                                different, heavy, various, low, high, high\_energy, low\_energy, several, present, simple, phenomenological, soft, important, single, interesting, main, typical, ref, many, inverse &                                               \shortstack[l]{Regge formalism (0.08)\\ Regge theory, duality, [...] (0.07)\\ S-matrix theory; analytic [...] (0.05)\\ Unified theories and models of [...] (0.05)\\ Elastic scattering (0.04)}\\ \hline
                        Uninterpretable &                                                     interaction, coupling, limit, value, correction, contribution, strong, constant, expansion, weak, bound, uncertainty, lower, force, range, strong\_coupling, distance, alpha, magnitude, lambda &                                            \shortstack[l]{Nuclear forces (0.07)\\ Determination of fundamental constants (0.06)\\ Pion-baryon interactions (0.06)\\ Experimental tests of [...] (0.06)\\ Hyperon-nucleon interactions (0.06)}\\ \hline
                        Uninterpretable &                                                           space, particle, time, charge, constraint, momentum, spin, region, angular, distribution, freedom, dynamic, set, way, degree, description, density, limit, information, angular\_momentum &                                                          \shortstack[l]{Quantum mechanics (0.08)\\ Special relativity (0.07)\\ Relativistic wave equations (0.07)\\ Lagrangian and Hamiltonian approach (0.06)\\ Protons and neutrons (0.06)}\\ \hline
\end{longtable}
