Publications

2021

• Probability distribution for the quantum universe
  
  • Kehagias Alex
  • Partouche Hervé
  • Toumbas Nicolaos
  Journal of High Energy Physics, Springer, 2021, 12, pp.165. We determine the inner product on the Hilbert space of wavefunctions of the universe by imposing the Hermiticity of the quantum Hamiltonian in the context of the minisuperspace model. The corresponding quantum probability density reproduces successfully the classical probability distribution in the ħ → 0 limit, for closed universes filled with a perfect fluid of index w. When −1/3 < w ≤ 1, the wavefunction is normalizable and the quantum probability density becomes vanishingly small at the big bang/big crunch singularities, at least at the semiclassical level. Quantum expectation values of physical geometrical quantities, which diverge classically at the singularities, are shown to be finite. (10.1007/JHEP12(2021)165)
  DOI : 10.1007/JHEP12(2021)165
• Relativistic spin sum rules and the role of the pivot
  
  • Lorcé Cédric
  European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2021, 81 (5), pp.413. Spin sum rules depend on the choice of a pivot, i.e. the point about which the angular momentum is defined, usually identified with the center of the nucleon. The latter is however not unique in a relativistic theory and has led to apparently contradictory results in the literature. Using the recently developed phase-space approach, we compute for the first time the contribution associated with the motion of the center of the nucleon, and we derive a general spin sum rule which reduces to established results after appropriate choices for the pivot and the spin component. (10.1140/epjc/s10052-021-09207-4)
  DOI : 10.1140/epjc/s10052-021-09207-4
• Hydrodynamic Diffusion and Its Breakdown near AdS2 Quantum Critical Points
  
  • Arean Daniel
  • Davison Richard A.
  • Goutéraux Blaise
  • Suzuki Kenta
  Physical Review X, American Physical Society, 2021, 11 (3), pp.031024. Hydrodynamics provides a universal description of interacting quantum field theories at sufficiently long times and wavelengths, but breaks down at scales dependent on microscopic details of the theory. In the vicinity of a quantum critical point, it is expected that some aspects of the dynamics are universal and dictated by properties of the critical point. We use gauge-gravity duality to investigate the breakdown of diffusive hydrodynamics in two low-temperature states dual to black holes with <math display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math> horizons, which exhibit quantum critical dynamics with an emergent scaling symmetry in time. We find that the breakdown is characterized by a collision between the diffusive pole of the retarded Green’s function with a pole associated to the <math display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math> region of the geometry, such that the local equilibration time is set by infrared properties of the theory. The absolute values of the frequency and wave vector at the collision (<math display="inline"><msub><mi>ω</mi><mrow><mi>eq</mi></mrow></msub></math> and <math display="inline"><msub><mi>k</mi><mrow><mi>eq</mi></mrow></msub></math>) provide a natural characterization of all the low-temperature diffusivities <math display="inline"><mi>D</mi></math> of the states via <math display="inline"><mi>D</mi><mo>=</mo><msub><mi>ω</mi><mrow><mi>eq</mi></mrow></msub><mo stretchy="false">/</mo><msubsup><mi>k</mi><mrow><mi>eq</mi></mrow><mn>2</mn></msubsup></math>, where <math display="inline"><msub><mi>ω</mi><mrow><mi>eq</mi></mrow></msub><mo>=</mo><mn>2</mn><mi>π</mi><mi mathvariant="normal">Δ</mi><mi>T</mi></math> is set by the temperature <math display="inline"><mi>T</mi></math> and the scaling dimension <math display="inline"><mi mathvariant="normal">Δ</mi></math> of an operator of the infrared quantum critical theory. We confirm that these relations are also satisfied in a Sachdev-Ye-Kitaev chain model in the limit of strong interactions. Our work paves the way toward a deeper understanding of transport in quantum critical phases. (10.1103/PhysRevX.11.031024)
  DOI : 10.1103/PhysRevX.11.031024
• 3d large $N$ vector models at the boundary
  
  • Di Pietro Lorenzo
  • Lauria Edoardo
  • Niro Pierluigi
  SciPost Physics, SciPost Foundation, 2021, 11 (3), pp.050. We consider a 4d scalar field coupled to large $N$ free or critical $O(N)$ vector models, either bosonic or fermionic, on a 3d boundary. We compute the $\beta$ function of the classically marginal bulk/boundary interaction at the first non-trivial order in the large $N$ expansion and exactly in the coupling. Starting with the free (critical) vector model at weak coupling, we find a fixed point at infinite coupling in which the boundary theory is the critical (free) vector model and the bulk decouples. We show that a strong/weak duality relates one description of the renormalization group flow to another one in which the free and the critical vector models are exchanged. We then consider the theory with an additional Maxwell field in the bulk, which also gives decoupling limits with gauged vector models on the boundary. (10.21468/SciPostPhys.11.3.050)
  DOI : 10.21468/SciPostPhys.11.3.050
• Two-loop corrections to the QCD propagators within the Curci-Ferrari model
  
  • Barrios Nahuel
  • Gracey John A.
  • Peláez Marcela
  • Reinosa Urko
  Physical Review D, American Physical Society, 2021, 104 (9), pp.094019. We evaluate all two-point correlation functions of the Curci-Ferrari (CF) model in four dimensions and in the presence of mass-degenerate fundamental quark flavors, as a natural extension of an earlier investigation in the quenched approximation. In principle, the proper account of chiral symmetry breaking (<math display="inline"><mrow><mi>χ</mi><mi>SB</mi></mrow></math>) and the corresponding dynamical generation of a quark-mass function within the CF model requires one to go beyond perturbation theory [M. Peláez, U. Reinosa, J. Serreau, M. Tissier, and N. Wschebor, Phys. Rev. D 103, 094035 (2021)]. However, it is interesting to assess whether a perturbative description applies to correlation functions that are not directly sensitive to <math display="inline"><mrow><mi>χ</mi><mi>SB</mi></mrow></math>, such as the gluon, ghost and quark dressing functions. We compare our two-loop results for these form factors to QCD lattice data in the two-flavor case for two different values of the pion mass, one that is relatively far from the chiral limit, and one that is closer to the physical value. Our results confirm that the QCD gluon and ghost dressing functions are well described by a perturbative approach within the CF model, as already observed at one-loop order [M. Peláez, M. Tissier, and N. Wschebor, Phys. Rev. D 90, 065031 (2014)]. Our new main result is that the quark dressing function is also well captured by the perturbative approach, but only starting at two-loop order, as also anticipated [M. Peláez, M. Tissier, and N. Wschebor, Phys. Rev. D 90, 065031 (2014)]. The quark-mass function predicted by the CF model at two-loop order is in good agreement with the data if the quarks are not too light but it shows some clear tension with respect to the two-loop CF dressing functions in the close to physical case, as expected. Interestingly, however, we find that there is much less tension between the nonperturbative quark-mass function, as it can be obtained from lattice simulations or from M. Peláez, U. Reinosa, J. Serreau, M. Tissier, and N. Wschebor, Phys. Rev. D 103, 094035 (2021), and the two-loop CF dressing functions, which confirms the perturbative nature of the latter. (10.1103/PhysRevD.104.094019)
  DOI : 10.1103/PhysRevD.104.094019
• Towards bootstrapping RG flows: sine-Gordon in AdS
  
  • Antunes António
  • Costa Miguel S.
  • Penedones João
  • Salgarkar Aaditya
  • van Rees Balt C.
  Journal of High Energy Physics, Springer, 2021, 12, pp.094. The boundary correlation functions for a Quantum Field Theory (QFT) in an Anti-de Sitter (AdS) background can stay conformally covariant even if the bulk theory undergoes a renormalization group (RG) flow. Studying such correlation functions with the numerical conformal bootstrap leads to non-perturbative constraints that must hold along the entire flow. In this paper we carry out this analysis for the sine-Gordon RG flows in AdS$_{2}$, which start with a free (compact) scalar in the UV and end with well-known massive integrable theories that saturate many S-matrix bootstrap bounds. We numerically analyze the correlation functions of both breathers and kinks and provide a detailed comparison with perturbation theory near the UV fixed point. Our bounds are often saturated to one or two orders in perturbation theory, as well as in the flat-space limit, but not necessarily in between. (10.1007/JHEP12(2021)094)
  DOI : 10.1007/JHEP12(2021)094
• The importance of kinematic twists and genuine saturation effects in dijet production at the Electron-Ion Collider
  
  • Boussarie Renaud
  • Mäntysaari Heikki
  • Salazar Farid
  • Schenke Björn
  Journal of High Energy Physics, Springer, 2021, 09, pp.178. We compute the differential yield for quark anti-quark dijet production in high-energy electron-proton and electron-nucleus collisions at small x as a function of the relative momentum P$_{⊥}$ and momentum imbalance k$_{⊥}$ of the dijet system for different photon virtualities Q$^{2}$, and study the elliptic and quadrangular anisotropies in the relative angle between P$_{⊥}$ and k$_{⊥}$. We review and extend the analysis in [1], which compared the results of the Color Glass Condensate (CGC) with those obtained using the transverse momentum dependent (TMD) framework. In particular, we include in our comparison the improved TMD (ITMD) framework, which resums kinematic power corrections of the ratio k$_{⊥}$ over the hard scale Q$_{⊥}$. By comparing ITMD and CGC results we are able to isolate genuine higher saturation contributions in the ratio Q$_{s}$/Q$_{⊥}$ which are resummed only in the CGC. These saturation contributions are in addition to those in the Weizsäcker-Williams gluon TMD that appear in powers of Q$_{s}$/k$_{⊥}$. We provide numerical estimates of these contributions for inclusive dijet production at the future Electron-Ion Collider, and identify kinematic windows where they can become relevant in the measurement of dijet and dihadron azimuthal correlations. We argue that such measurements will allow the detailed experimental study of both kinematic power corrections and genuine gluon saturation effects. (10.1007/JHEP09(2021)178)
  DOI : 10.1007/JHEP09(2021)178
• Étude de l'impact du handicap sur le recrutement et le déroulé de carrière des chercheurs au CNRS
  
  • Jacques Vincent
  • Löfberg Axel
  • Loty Laurent
  • Loubière Karine
  • Lütjens Hinrich
  • Marie Emmanuelle
  • Saracco Ginette
  • Souchay Céline
  • Tricard Simon
  • Weil Dominique
  , 2021.
• Remarks on a melonic field theory with cubic interaction
  
  • Benedetti Dario
  • Delporte Nicolas
  Journal of High Energy Physics, Springer, 2021, 04, pp.197. We revisit the Amit-Roginsky (AR) model in the light of recent studies on Sachdev-Ye-Kitaev (SYK) and tensor models, with which it shares some important features. It is a model of N scalar fields transforming in an N-dimensional irreducible representation of SO(3). The most relevant (in renormalization group sense) invariant interaction is cubic in the fields and mediated by a Wigner 3jm symbol. The latter can be viewed as a particular rank-3 tensor coupling, thus highlighting the similarity to the SYK model, in which the tensor coupling is however random and of even rank. As in the SYK and tensor models, in the large-N limit the perturbative expansion is dominated by melonic diagrams. The lack of randomness, and the rapidly growing number of invariants that can be built with n fields, makes the AR model somewhat closer to tensor models. We review the results from the old work of Amit and Roginsky with the hindsight of recent developments, correcting and completing some of their statements, in particular concerning the spectrum of the operator product expansion of two fundamental fields. For 5.74 < d < 6 the fixed-point theory defines a real CFT, while for smaller d complex dimensions appear, after a merging of the lowest dimension with its shadow. We also introduce and study a long-range version of the model, for which the cubic interaction is exactly marginal at large N , and we find a real and unitary CFT for any d < 6, both for real and imaginary coupling constant, up to some critical coupling. (10.1007/JHEP04(2021)197)
  DOI : 10.1007/JHEP04(2021)197
• Localization dynamics from static and mobile impurities
  
  • Bernhardt Ephraim
  • Yang Fan
  • Le Hur Karyn
  Physical Review B, American Physical Society, 2021, 104 (11), pp.115113. We study the superfluid response and localization dynamics from static and mobile impurities. The superfluidity is formed in the rung-Mott phase of a bosonic ladder model producing spin-Meissner currents induced by a <math><mrow><mi mathvariant="double-struck">U</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow></math> gauge field or a uniform magnetic field. Impurities are described through two-state systems, which act as a two-peak random potential. An impurity sits either at the top or at the bottom of the ladder on each rung equally, producing a telegraph signal. The impurities-matter coupling gives rise to a classical Ising symmetry for static and mobile impurities associated to the inversion symmetry of the two legs of the ladder. From the decoupled rungs limit, we also identify a local <math><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> gauge theory for mobile impurities. The properties of the system are studied from an effective quantum spin model including the possibility of four-body coupling in the limit of a strong interaction between bosons and impurities. Through analytical approaches and numerical exact diagonalization, we study the superfluid currents both in the weakly-coupled and strongly-coupled rungs limits for the bosons. In the weakly-coupled rungs situation, we find a smooth power-law localization whereas the strongly-coupled rungs limit produces a steep localization or insulating phase for various configurations of the two-peak random potential. In the strongly disordered situation, through entanglement and bipartite fluctuation measures, we also identify a many-body localization regime in time after a quench of the system when prepared in a Néel state. (10.1103/PhysRevB.104.115113)
  DOI : 10.1103/PhysRevB.104.115113
• Symmetry restoration and the gluon mass in the Landau gauge
  
  • Reinosa Urko
  • Serreau Julien
  • Terin Rodrigo Carmo
  • Tissier Matthieu
  SciPost Physics, SciPost Foundation, 2021, 10 (2), pp.035. We investigate the generation of a gluon screening mass in Yang-Mills theory in the Landau gauge. We propose a gauge-fixing procedure where the Gribov ambiguity is overcome by summing over all Gribov copies with some weight function. This can be formulated in terms of a local field theory involving constrained, nonlinear sigma model fields. We show that a phenomenon of radiative symmetry restoration occurs in this theory, similar to what happens in the standard nonlinear sigma model in two dimensions. This results in a nonzero gluon screening mass, as seen in lattice simulations. (10.21468/SciPostPhys.10.2.035)
  DOI : 10.21468/SciPostPhys.10.2.035
• One-loop masses of Neumann-Dirichlet open strings and boundary-changing vertex operators
  
  • Coudarchet Thibaut
  • Partouche Hervé
  Journal of High Energy Physics, Springer, 2021, 12, pp.022. We derive the masses acquired at one loop by massless scalars in the Neumann-Dirichlet sector of open strings, when supersymmetry is spontaneously broken. It is done by computing two-point functions of “boundary-changing vertex operators” inserted on the boundaries of the annulus and Möbius strip. This requires the evaluation of correlators of “excited boundary-changing fields,” which are analogous to excited twist fields for closed strings. We work in the type IIB orientifold theory compactified on T$^{2}$× T$^{4}$/ℤ$_{2}$, where $ \mathcal{N} $ = 2 supersymmetry is broken to $ \mathcal{N} $ = 0 by the Scherk-Schwarz mechanism implemented along T$^{2}$. Even though the full expression of the squared masses is complicated, it reduces to a very simple form when the lowest scale of the background is the supersymmetry breaking scale M$_{3/2}$. We use our results to analyze in this regime the stability at the quantum level of the moduli fields arising in the Neumann-Dirichlet sector. This completes the study of ref. [32], where the quantum masses of all other types of moduli arising in the open- or closed-string sectors are derived. Ultimately, we identify all brane configurations that produce backgrounds without tachyons at one loop and yield an effective potential exponentially suppressed, or strictly positive with runaway behavior of M$_{3/2}$. (10.1007/JHEP12(2021)022)
  DOI : 10.1007/JHEP12(2021)022
• Nuclear scattering configurations of onia in different frames
  
  • Le Anh Dung
  • Mueller Alfred H.
  • Munier Stéphane
  Physical Review D, American Physical Society, 2021, 103 (5), pp.054031. In the scattering of a small onium off a large nucleus at high center-of-mass energies, when the parameters are set in such a way that the cross section at a fixed impact parameter is small, events are triggered by rare partonic fluctuations of the onium, which are very deformed with respect to typical configurations. Using the color dipole picture of high-energy interactions in quantum chromodynamics, in which the quantum states of the onium are represented by sets of dipoles generated by a branching process, we describe the typical scattering configurations as seen from different reference frames, from the rest frame of the nucleus to frames in which the rapidity is shared between the projectile onium and the nucleus. We show that taking advantage of the freedom to select a frame in the latter class makes it possible to derive complete asymptotic expressions for some boost-invariant quantities, beyond the total cross section, from a procedure which leverages the limited available knowledge on the properties of the solutions to the Balitsky-Kovchegov equation that governs the rapidity dependence of total cross sections. We obtain, in this way, an analytic expression for the rapidity distribution of the first branching of the slowest parent dipole of the set of those which scatter. This distribution provides an estimator of the correlations of the interacting dipoles and is also known to be related to the rapidity-gap distribution in diffractive dissociation, an observable measurable at a future electron-ion collider. Furthermore, our result may be formulated as a more general conjecture that we expect to hold true for any one-dimensional branching random walk model, on the branching time of the most recent common ancestor of all the particles that end up to the right of a given position. (10.1103/PhysRevD.103.054031)
  DOI : 10.1103/PhysRevD.103.054031
• Phenomenological assessment of proton mechanical properties from deeply virtual Compton scattering
  
  • Dutrieux H.
  • Lorcé C.
  • Moutarde H.
  • Sznajder P.
  • Trawiński A.
  • Wagner J.
  European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2021, 81 (4), pp.300. A unique feature of generalised parton distributions is their relation to the QCD energy–momentum tensor. In particular, they provide access to the mechanical properties of the proton i.e. the distributions of pressure and shear stress induced by its quark and gluon structure. In principle the pressure distribution can be experimentally determined in a model-independent way from a dispersive analysis of deeply virtual Compton scattering data through the measurement of the subtraction constant. In practice the kinematic coverage and accuracy of existing experimental data make this endeavour a challenge. Elaborating on recent global fits of deeply virtual Compton scattering measurements using artificial neural networks, our analysis presents the current knowledge on this subtraction constant and assesses the impact of the most frequent systematic assumptions made in this field of research. This study will pave the way for future works when more precise data will become available, e.g. obtained in the foreseen electron-ion colliders EIC and EIcC. (10.1140/epjc/s10052-021-09069-w)
  DOI : 10.1140/epjc/s10052-021-09069-w
• Interacting Stochastic Topology and Mott Transition from Light Response
  
  • Klein Philipp W.
  • Grushin Adolfo G.
  • Le Hur Karyn
  Physical Review B, American Physical Society, 2021, 103 (3), pp.035114. We develop a stochastic description of the topological properties in an interacting Chern insulator. We confirm the Mott transition's first-order nature in the interacting Haldane model on the honeycomb geometry from a mean-field variational approach supported by density matrix renormalization group results and Ginzburg-Landau arguments. From the Bloch sphere, we make predictions for circular dichroism of light related to the quantum Hall conductivity on the lattice and in the presence of interactions. This analysis shows that the topological number can be measured from the light response at the Dirac points. Electron-electron interactions can also produce a substantial number of particle-hole pairs above the band gap, which leads us to propose a stochastic Chern number as an interacting measure of the topology. The stochastic Chern number can describe disordered situations with a fluctuating staggered potential, and we build an analogy between interaction-induced particle-hole pairs and temperature effects. Our stochastic approach is physically intuitive, easy to implement, and leads the way to further studies of interaction effects. (10.1103/PhysRevB.103.035114)
  DOI : 10.1103/PhysRevB.103.035114
• Instability of complex CFTs with operators in the principal series
  
  • Benedetti Dario
  Journal of High Energy Physics, Springer, 2021, 05, pp.004. We prove the instability of d-dimensional conformal field theories (CFTs) having in the operator-product expansion of two fundamental fields a primary operator of scaling dimension h = $ \frac{d}{2} $ + i r, with non-vanishing r ∈ ℝ. From an AdS/CFT point of view, this corresponds to a well-known tachyonic instability, associated to a violation of the Breitenlohner-Freedman bound in AdS$_{d+1}$; we derive it here directly for generic d-dimensional CFTs that can be obtained as limits of multiscalar quantum field theories, by applying the harmonic analysis for the Euclidean conformal group to perturbations of the conformal solution in the two-particle irreducible (2PI) effective action. Some explicit examples are discussed, such as melonic tensor models and the biscalar fishnet model. (10.1007/JHEP05(2021)004)
  DOI : 10.1007/JHEP05(2021)004
• Energy-momentum tensor in QCD: nucleon mass decomposition and mechanical equilibrium
  
  • Lorcé Cédric
  • Metz Andreas
  • Pasquini Barbara
  • Rodini Simone
  Journal of High Energy Physics, Springer, 2021, 11, pp.121. We review and examine in detail recent developments regarding the question of the nucleon mass decomposition. We discuss in particular the virial theorem in quantum field theory and its implications for the nucleon mass decomposition and mechanical equilibrium. We reconsider the renormalization of the QCD energy-momentum tensor in minimal-subtraction-type schemes and the physical interpretation of its components, as well as the role played by the trace anomaly and Poincaré symmetry. We also study the concept of “quantum anomalous energy” proposed in some works as a new contribution to the nucleon mass. Examining the various arguments, we conclude that the quantum anomalous energy is not a genuine contribution to the mass sum rule, as a consequence of translation symmetry. (10.1007/JHEP11(2021)121)
  DOI : 10.1007/JHEP11(2021)121
• Line and surface defects for the free scalar field
  
  • Lauria Edoardo
  • Liendo Pedro
  • van Rees Balt C.
  • Zhao Xiang
  Journal of High Energy Physics, Springer, 2021, 01, pp.060. For a single free scalar field in d ≥ 2 dimensions, almost all the unitary conformal defects must be ‘trivial’ in the sense that they cannot hold interesting dynamics. The only possible exceptions are monodromy defects in d ≥ 4 and co-dimension three defects in d ≥ 5. As an intermediate result we show that the n-point correlation functions of a conformal theory with a generalized free spectrum must be those of the generalized free theory. (10.1007/JHEP01(2021)060)
  DOI : 10.1007/JHEP01(2021)060
• Tracing Evolution of Angle-Wavelength Spectrum along the 40-m Postfilament in Corridor Air
  
  • Mokrouso Daria V
  • Pushkarev Dmitrii V
  • Panov Nikolay A
  • Nikolaeva Irina A
  • Shipilo Daniil E
  • Zhidovtsev Nikita A
  • Rizaev Georgy E
  • Uryupina Daria S
  • Couairon Arnaud
  • Houard Aurélien
  • Skryabin Dmitry V
  • Savel'Ev Andrey B
  • Kosareva Olga G
  • Seleznev Leonid V
  • Ionin Andrey A
  Photonics, MDPI, 2021, 8 (10), pp.446. Postfilamentation channel resulting from filamentation of freely propagating 744-nm, 5-mJ, 110-fs pulse in the corridor air is examined experimentally and in simulations. The longitudinal extension of postfilament was determined to be 55–95 m from the compressor output. Using single-shot angle-wavelength spectra measurements, we observed a series of red-shifted maxima in the spectrum, localized on the beam axis with the divergence below 0.5 mrad. In the range 55–70 m, the number of maxima and their red-shift increase with the distance reaching 1 μm, while the pulse duration measured by the autocorrelation technique is approximately constant. Further on, for distances larger than 70 m and up to 95 m, the propagation is characterized by the suppressed beam divergence and unchanged pulse spectrum. The pulse duration increases due to the normal air dispersion. (10.3390/photonics8100446)
  DOI : 10.3390/photonics8100446
• Shifting spin on the celestial sphere
  
  • Pasterski Sabrina
  • Puhm Andrea
  Physical Review D, American Physical Society, 2021, 104 (8), pp.086020. We explore conformal primary wave functions for all half integer spins up to the graviton. Half steps are related by supersymmetry, integer steps by the classical double copy. The main results are as follows: we 1) introduce a convenient spin frame and null tetrad to organize all radiative modes of varying spin; 2) identify the massless spin-<math display="inline"><mfrac><mn>3</mn><mn>2</mn></mfrac></math> conformal primary wave function as well as the conformally soft Goldstone mode corresponding to large supersymmetry transformations; 3) indicate how to express a conformal primary of arbitrary spin in terms of differential operators acting on a scalar primary; 4) demonstrate that conformal primary metrics satisfy the double copy in a variety of forms—operator, Weyl, and Kerr-Schild—and are exact, albeit complex, solutions to the fully nonlinear Einstein equations of Petrov type <math display="inline"><mrow><mi mathvariant="bold">N</mi></mrow></math>; 5) propose a novel generalization of conformal primary wave functions; and 6) show that this generalization includes a large class of physically interesting metrics corresponding to ultra-boosted black holes, shockwaves and more. (10.1103/PhysRevD.104.086020)
  DOI : 10.1103/PhysRevD.104.086020
• Skewed non-Fermi liquids and the Seebeck effect
  
  • Georges Antoine
  • Mravlje Jernej
  Physical Review Research, American Physical Society, 2021, 3 (4), pp.043132. We consider non-Fermi liquids in which the inelastic scattering rate has an intrinsic particle-hole asymmetry and obeys <math><mrow><mi>ω</mi><mo>/</mo><mi>T</mi></mrow></math> scaling. We show that, in contrast to Fermi liquids, this asymmetry influences the low-temperature behavior of the thermopower even when the impurity scattering dominates. Implications for the unconventional sign and temperature dependence of the thermopower in cuprates in the strange metal (Planckian) regime are emphasized. (10.1103/PhysRevResearch.3.043132)
  DOI : 10.1103/PhysRevResearch.3.043132
• Analytical approach for the Mott transition in the Kane-Mele-Hubbard model
  
  • Hutchinson Joel
  • Klein Philipp W.
  • Le Hur Karyn
  Physical Review B, American Physical Society, 2021, 104 (7), pp.075120. The description of interactions in strongly correlated topological phases of matter remains a challenge. Here, we develop a stochastic functional approach for interacting topological insulators including both charge and spin channels. We find that the Mott transition of the Kane-Mele-Hubbard model may be described by the variational principle with one equation. We present different views of this equation from the electron Green's function, the free-energy, and the Hellmann-Feynman theorem. In particular, we show the stability of the transition line towards fluctuations, in good agreement with numerical results. The band gap remains finite at the transition and the Mott phase is characterized by antiferromagnetism in the <math><mrow><mi>x</mi><mtext>-</mtext><mi>y</mi></mrow></math> plane. The interacting topological phase is described through a <math><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> number related to helical edge modes. Our results then show that improving stochastic approaches can give further insight on the understanding of interacting phases of matter. (10.1103/PhysRevB.104.075120)
  DOI : 10.1103/PhysRevB.104.075120
• Light-control of materials via nonlinear phononics
  
  • Subedi Alaska
  Comptes Rendus. Physique, Académie des sciences (Paris), 2021, 22 (S2), pp.1-24. (10.5802/crphys.44)
  DOI : 10.5802/crphys.44
• Schrodinger's original quantum-mechanical solution for hydrogen
  
  • Galler Anna
  • Canfield Jeremy
  • Freericks James K.
  Eur.J.Phys., 2021, 42 (3), pp.035405. In 1926, Erwin Schrodinger wrote a series of papers that invented wave mechanics and set the foundation for much of the single-particle quantum mechanics that we teach today. In his first paper, he solved the Schrodinger equation using the Laplace method, which is a technique that is quite powerful, but rarely taught. This is unfortunate, because it opens the door to examining quantum mechanics from a complex-analysis perspective. Gaining this experience with complex analysis is a useful notion to consider when teaching quantum mechanics, as these techniques can be widely used outside of quantum mechanics, unlike the standard Frobenius summation method, which is normally taught, but rarely used elsewhere. The Laplace method strategy is subtle and no one has carefully gone through the arguments that Schrodinger did in this first paper, instead it is often just stated that the solution was adopted from Schlesinger's famous differential equation textbook. In this work, we show how the Laplace method can be used to solve for the quantum-mechanical energy eigenfunctions of the hydrogen atom, following Schrodinger's original solution, with all the necessary details, and illustrate how it can be taught in advanced instruction; it does require familiarity with intermediate-level complex analysis, which we also briefly review. (10.1088/1361-6404/abb9ff)
  DOI : 10.1088/1361-6404/abb9ff
• Coulomb gluons will generally destroy coherence
  
  • Forshaw Jeffrey R.
  • Holguin Jack
  Journal of High Energy Physics, Springer, 2021, 12, pp.084. Coherence violation is an interesting and counter-intuitive phenomenon in QCD. We discuss the circumstances under which violation occurs in observables sensitive to soft radiation and arrive at the conclusion that almost all such observables at hadron colliders will violate coherence to some degree. We illustrate our discussion by considering the gaps-between-jets observable, where coherence violation is super-leading, then we generalise to other observables, including precise statements on the logarithmic order of coherence violation. (10.1007/JHEP12(2021)084)
  DOI : 10.1007/JHEP12(2021)084