\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}\\
\toprule
                         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
\midrule
\multicolumn{3}{r}{{Continued on next page}} \\
\midrule
\endfoot

\bottomrule
\endlastfoot
             Black Holes and Cosmology &              hole, black\_hole, black, gravity, cosmology, gravitational, horizon, cosmological, curvature, background, universe, primordial, era, hair, brane\_world, einstein, planck, inflationary\_universe, censorship, entropy &                             \shortstack[l]{Quantum aspects of black holes, [...] (0.40)\\ Particle-theory and field-theory [...] (0.34)\\ Classical black holes (0.31)\\ Modified theories of gravity (0.27)\\ Physics of black holes (0.25)}\\ \hline
    Equations of Motion and Invariance &              equation, action, invariant, transformation, massive, motion, invariance, generalized, exact, lagrangians, paper, formulation, effective\_action, derivative, second, massless, covariant, symmetric, linearized, first &                       \shortstack[l]{Lagrangian and Hamiltonian approach (0.23)\\ Gauge field theories (0.21)\\ Lorentz and Poincaré invariance (0.18)\\ Relativistic wave equations (0.14)\\ Canonical formalism, Lagrangians, [...] (0.13)}\\ \hline
Hadronic Collisions and Cross Sections & distribution, cross\_sections, production, collision, process, section, scattering, hadronic\_collision, cross\_section, parton, cross, proton, kinematics, hadron, prediction, correction, tomography, impact, partons, observables & \shortstack[l]{Perturbative calculations (0.33)\\ Total and inclusive cross sections [...] (0.28)\\ Polarization in interactions and [...] (0.27)\\ Inclusive production with [...] (0.27)\\ Quarks, gluons, and QCD in nuclear [...] (0.21)}\\ \hline
      Higgs and Standard Model Physics &                          higgs, standard, boson, standard\_model, sm, physic, lhc, particle, mssm, tev, top, phenomenology, collider, deviation, electroweak, search, extension, prediction, supersymmetric\_model, sensitive\_probe &               \shortstack[l]{Supersymmetric models (0.35)\\ Extensions of electroweak Higgs sector (0.35)\\ Non-standard-model Higgs bosons (0.30)\\ Supersymmetric partners of known [...] (0.28)\\ Models beyond the standard model (0.26)}\\ \hline
      Holography and Boundary Theories &           boundary, holographic, casimir, defect, conformal, dynamical, bulk, boundary\_theory, finite, holography, topological, two\_dimensional, asymptotic, replica, cfts, renormalized, boundary\_field, spatial, charge, global &           \shortstack[l]{Conformal field theory, algebraic [...] (0.22)\\ Gauge/string duality (0.21)\\ Theory of quantized fields (0.16)\\ Field theories in dimensions other [...] (0.16)\\ Entanglement measures, witnesses, [...] (0.12)}\\ \hline
               Interactions and Decays &                                       solution, decay, interaction, limit, value, coupling, magnetic, constant, vacuum, bound, presence, condition, strong, charge, background, weak, problem, electric, configuration, contribution &                                            \shortstack[l]{Specific calculations (0.13)\\ Magnetic monopoles (0.13)\\ Extended classical solutions; [...] (0.12)\\ Electric and magnetic moments (0.11)\\ Electric and magnetic fields (0.08)}\\ \hline
             Neutrinos and Dark Matter &                            neutrino, dark, matter, dark\_matter, experiment, candidate, observation, detection, dm, density, leptogenesis, prospect, relic, observed, terrestrial, sun, constraint, neutron, implication, asymmetric &                                                                  \shortstack[l]{Dark matter (0.53)\\ Neutrino mass and mixing (0.51)\\ Non-standard-model neutrinos, [...] (0.31)\\ Ordinary neutrinos (0.24)\\ Neutrino interactions (0.24)}\\ \hline
                Operators and Symmetry &                                              operator, dimension, scale, matrix, group, structure, fermion, flavor, sector, su, representation, loop, coupling, breaking, violation, unification, mixing, minimal, length, anomalous &                        \shortstack[l]{Quark and lepton masses and mixing (0.28)\\ Unified theories and models of [...] (0.24)\\ Flavor symmetries (0.23)\\ Neutrino mass and mixing (0.21)\\ Unification of couplings; mass relations (0.18)}\\ \hline
            QCD Methods and Techniques &                                       qcd, amplitude, approach, form, correction, factor, method, expansion, calculation, approximation, sum, perturbative, vertex, rule, evaluation, technique, integral, diagram, computation, qed &                                                    \shortstack[l]{General properties of perturbation [...] (0.25)\\ Other nonperturbative calculations (0.19)\\ Perturbative calculations (0.19)\\ Sum rules (0.18)\\ Renormalization (0.16)}\\ \hline
     Quantum Mechanics and Observables &                        quantum, time, number, spin, system, dynamic, space, momentum, information, degree, arbitrary, mechanic, freedom, wigner, variable, coordinate, characterization, physical\_observables, bounded, observables &                                       \shortstack[l]{Quantum mechanics (0.19)\\ Foundations of quantum mechanics; [...] (0.19)\\ Formalism (0.14)\\ Entanglement and quantum nonlocality (0.13)\\ Loop quantum gravity, quantum [...] (0.12)}\\ \hline
                   Quark-Meson Physics &                                            quark, chiral, meson, baryon, width, form\_factors, current, \_meson, data, heavy, light, mev, light\_quark, resonance, eta\_prime, rho, channel, pion, experimental\_data, extrapolation &                                                 \shortstack[l]{Chiral Lagrangians (0.28)\\ Glueball and nonstandard multi- [...] (0.22)\\ Meson-meson interactions (0.21)\\ Relativistic quark model (0.20)\\ Decays of bottom mesons (0.20)}\\ \hline
          Scalar Fields and Potentials &                                                  scalar, potential, effective, spectrum, perturbation, tensor, mode, low\_energy, linear, low, real, spectral, vector, scalar\_field, effective\_field, phi, part, high, power, free &                                \shortstack[l]{Particle-theory and field-theory [...] (0.19)\\ Finite-temperature field theory (0.10)\\ Quantum fields in curved spacetime (0.09)\\ Cosmology (0.07)\\ Gravity in more than four [...] (0.06)}\\ \hline
            String Theory and Geometry &  space, deformation, super, superstring, string, supersymmetric, twistor, non\_compact, deformed, modulus, subsector, superpotentials, map, sigma\_models, stringy, three\_sphere, geometry, generalisation, yangmills, construction &                                                                                            \shortstack[l]{Supersymmetry (0.30)\\ Strings and branes (0.26)\\ Supergravity (0.26)\\ Compactification and four- [...] (0.22)\\ M theory (0.18)}\\ \hline
        Thermal and Critical Phenomena &                               phase, temperature, transition, property, density, critical\_point, plasma, correlation, chemical, behavior, point, dynamic, viscosity, fluctuation, relativistic, flow, thermal, hot, droplet, system &                                    \shortstack[l]{Quark-gluon plasma (0.42)\\ Quark deconfinement, quark-gluon [...] (0.32)\\ Finite-temperature field theory (0.29)\\ Relativistic heavy-ion collisions (0.27)\\ Hydrodynamic models (0.21)}\\ \hline
                       Uninterpretable &                                                  general, various, present, different, first, previous, several, higher, single, small, relevant, numerical, obtained, similar, double, ref, dependent, alternative, main, realistic &                     \shortstack[l]{Atomic and molecular beam sources [...] (0.05)\\ Quark and lepton masses and mixing (0.04)\\ Modified theories of gravity (0.04)\\ History of science (0.03)\\ Numerical differentiation and [...] (0.03)}\\ \hline
\end{longtable}
