Publications

2023

• Colloquium: Hydrodynamics and holography of charge density wave phases
  
  • Baggioli Matteo
  • Goutéraux Blaise
  Rev.Mod.Phys., 2023, 95 (1), pp.011001. In this Colloquium, we review recent progress in the effective description of strongly-correlated phases of matter with spontaneously broken translations, such as charge density waves or Wigner crystals. In real materials, disorder is inevitable and pins the Goldstones of broken translations. We describe how pinning can be incorporated in the effective field theory at low energies, without making any assumption on the presence of boost symmetry. We review the essential role played by gauge-gravity duality models in establishing these effective field theories with only approximate symmetries. We close with a discussion on the relevance of these models for the phenomenology of dc and ac transport in strongly-correlated strange and bad metals, such as high temperature superconductors. (10.1103/RevModPhys.95.011001)
  DOI : 10.1103/RevModPhys.95.011001
• Singularities in 2D and 3D quantum black holes
  
  • Kolanowski Maciej
  • Tomašević Marija
  Journal of High Energy Physics, Springer, 2023, 12, pp.102. We study black holes in two and three dimensions that have spacelike curvature singularities behind horizons. The 2D solutions are obtained by dimensionally reducing certain 3D black holes, known as quantum BTZ solutions. Furthermore, we identify the corresponding dilaton potential and show how it can arise from a higher-dimensional theory. Finally, we show that the rotating BTZ black hole develops a singular inner horizon once quantum effects are properly accounted for, thereby solidifying strong cosmic censorship for all known cases. (10.1007/JHEP12(2023)102)
  DOI : 10.1007/JHEP12(2023)102
• Accessing GPDs through the exclusive photoproduction of a photon-meson pair with a large invariant mass
  
  • Duplančić Goran
  • Nabeebaccus Saad
  • Passek-Kumerički Kornelija
  • Pire Bernard
  • Szymanowski Lech
  • Wallon Samuel
  Acta Physica Polonica B Proceedings Supplement, Jagiellonian University, 2023, 16 (5), pp.16. We study the exclusive photoproduction of a photon-meson pair with a large invariant mass, working in the QCD factorisation framework. Explicitly, we consider a $ \rho $-meson or a charged $ \pi $ in the final state. This process gives access to chiral-even GPDs as well as chiral-odd GPDs. We focus here on the chiral-even sector. The computation is performed at leading order and leading twist. We discuss the prospects of measuring them in various experiments such as JLab 12-GeV, COMPASS, future EIC and LHC (in ultraperipheral collisions). In particular, the high centre of mass energies available at collider experiments can be used to probe GPDs at small skewness $ \xi $. We also compute the polarisation asymmetries with respect to the incoming photon. The results for an alternative distribution amplitude (`holographic' form) are also compared with the predictions obtained with an asymptotic distribution amplitude. (10.5506/APhysPolBSupp.16.5-A16)
  DOI : 10.5506/APhysPolBSupp.16.5-A16
• $\overline{\textrm{D}3}$-branes and gaugino condensation
  
  • Bena Iosif
  • Dudas Emilian
  • Graña Mariana
  • Lo Monaco Gabriele
  • Toulikas Dimitrios
  Journal of High Energy Physics, Springer, 2023, 2023 (12), pp.19. Anti-D3 branes at the bottom of warped throats, commonly used to uplift the cosmological constant in String-Theory de Sitter proposals, source a plethora of supersymmetry-breaking fluxes, that can interact nontrivially with other ingredients of the flux compactification. In this paper we perform a complex-structure decomposition of these fluxes, and compute the effect of the (0,3) flux component on the stabilization of Kähler moduli via D7-branes gaugino condensation. This allows us to obtain a new constraint on the validity of this stabilization mechanism. This effect does not appear hard to satisfy in de Sitter construction proposals that use long warped throats, but may be problematic in proposals where the warping is small. (10.1007/JHEP12(2023)019)
  DOI : 10.1007/JHEP12(2023)019
• Equilibrium Quantum Impurity Problems via Matrix Product State Encoding of the Retarded Action
  
  • Kloss Benedikt
  • Thoenniss Julian
  • Sonner Michael
  • Lerose Alessio
  • Fishman Matthew T
  • Stoudenmire E.M
  • Parcollet Olivier
  • Georges Antoine
  • Abanin Dmitry A
  Physical Review B, American Physical Society, 2023, 108 (20), pp.205110. In the $0+1$ dimensional imaginary-time path integral formulation of quantum impurity problems, the retarded action encodes the hybridization of the impurity with the bath. In this Article, we explore the computational power of representing the retarded action as matrix product state (RAMPS). We focus on the challenging Kondo regime of the single-impurity Anderson model, where non-perturbative strong-correlation effects arise at very low energy scales. We demonstrate that the RAMPS approach reliably reaches the Kondo regime for a range of interaction strengths $U$, with a numerical error scaling as a weak power law with inverse temperature. We investigate the convergence behavior of the method with respect to bond dimension and time discretization by analyzing the error of local observables in the full interacting problem and find polynomial scaling in both parameters. Our results show that the RAMPS approach offers promise as an alternative tool for studying quantum impurity problems in regimes that challenge established methods, such as multi-orbital systems. Overall, our study contributes to the development of efficient and accurate non-wavefunction-based tensor-network methods for quantum impurity problems. (10.1103/PhysRevB.108.205110)
  DOI : 10.1103/PhysRevB.108.205110
• A Coherent View of the Quark-Gluon Plasma from Energy Correlators
  
  • Andres Carlota
  • Dominguez Fabio
  • Holguin Jack
  • Marquet Cyrille
  • Moult Ian
  Journal of High Energy Physics, Springer, 2023, 09, pp.088. The ability to measure detailed aspects of the substructure of high-energy jets traversing the quark-gluon plasma (QGP) has provided a new window into its internal dynamics. However, drawing robust conclusions from traditional jet substructure observables has been difficult. In this manuscript we expand on a new approach to jet substructure in heavy-ion collisions based on the study of correlation functions of energy flow operators (energy correlators). We compute the two-point energy correlator of an in-medium massless quark jet and perform a detailed numerical analysis of the produced spectra. Our calculation incorporates vacuum radiation resummed at next-to-leading log accuracy together with the leading order contribution in medium-induced splittings evaluated through the BDMPS-Z multiple scattering and GLV single scattering formalisms. Our analysis demonstrates how particular features of the modifications of in-medium splittings are imprinted in the correlator spectra, particularly showing how energy correlators may be used to extract the onset of colour coherence. We further present a comprehensive discussion on the accuracy and limitations of our study emphasizing how it can be systematically improved. This work sets the foundations for a rich program studying energy correlators in heavy-ion collisions. (10.1007/JHEP09(2023)088)
  DOI : 10.1007/JHEP09(2023)088
• Non-dissipative electrically driven fluids
  
  • Amoretti Andrea
  • Brattan Daniel K.
  • Martinoia Luca
  • Matthaiakakis Ioannis
  Journal of High Energy Physics, Springer, 2023, 05, pp.218. Existing hydrodynamic models of charged fluids consider any external electric field acting on the fluid as either first order in the hydrodynamic derivative expansion and completely arbitrary or zeroth order but constrained by the fluid's chemical potential. This is in tension with experiments on charged fluids, where the electric field is both zeroth order and completely arbitrary. In this work, we take the first step at resolving this conundrum by introducing a new class of hydrodynamic stationary states, including an arbitrary zeroth order electric field, upon which hydrodynamics can be built. We achieve this by first writing down the hydrostatic constitutive relations for a boost-agnostic charged fluid up to first order in derivatives. Then we introduce suitable energy and momentum relaxation terms to balance the influence of the electric field on the fluid. This analysis leads to a new hydrostatic constraint on the spatial fluid velocity, which can be used to define our class of states. This constraint generalizes to the realm of hydrodynamics a similar constraint on the velocity found in the Drude model of electronic transport. Our class of states exhibits non-trivial thermo-electric transport even at ideal order, since it hosts non-zero DC electric and heat currents. We derive the explicit form of the corresponding conductivities and show they depend non-linearly on the electric field. (10.1007/JHEP05(2023)218)
  DOI : 10.1007/JHEP05(2023)218
• Supergravity Scattering Amplitudes
  
  • Dudas Emilian
  • Gherghetta Tony
  • Olive Keith A.
  • Verner Sarunas
  Physical Review D, American Physical Society, 2023, 108 (7), pp.076024. Supergravity theories with non-minimal Kähler potentials are characterized by a non-trivial field space manifold with corresponding non-trivial kinetic terms. The scattering amplitudes in these theories can be calculated at fixed background field values by making a field redefinition to Riemann normal coordinates. Because of the Kähler structure of supergravity, a more compact method for calculating amplitudes is obtained by a redefinition to Kähler normal coordinates. We compare both methods and calculate the explicit transformations and amplitudes for several examples in the context of no-scale supergravity with one and two chiral superfields. We show that in all cases the equivalence of the scattering amplitudes using either Riemann normal or Kähler normal coordinates is possible only at extremal points of the scalar potential. (10.1103/PhysRevD.108.076024)
  DOI : 10.1103/PhysRevD.108.076024
• Flat from anti-de Sitter
  
  • Campoleoni Andrea
  • Delfante Arnaud
  • Pekar Simon
  • Petropoulos P. Marios
  • Rivera-Betancour David
  • Vilatte Matthieu
  Journal of High Energy Physics, Springer, 2023, 12, pp.078. Ricci-flat solutions to Einstein's equations in four dimensions are obtained as the flat limit of Einstein spacetimes with negative cosmological constant. In the limiting process, the anti-de Sitter energy--momentum tensor is expanded in Laurent series in powers of the cosmological constant, endowing the system with the infinite number of boundary data, characteristic of the asymptotically flat solution space. The governing flat Einstein dynamics is recovered as the limit of the original energy--momentum conservation law and from the additional requirement of the line-element finiteness, providing at each order the necessary set of flux-balance equations for the boundary data. This analysis is conducted using a covariant version of the Newman--Unti gauge designed for taking advantage of the boundary Carrollian structure emerging at vanishing cosmological constant and its Carrollian attributes such as the Cotton tensor. (10.1007/JHEP12(2023)078)
  DOI : 10.1007/JHEP12(2023)078
• AdS$_2$ Holography and Effective QFT
  
  • Choi Sangmin
  • Larsen Finn
  Journal of High Energy Physics, Springer, 2023, 11, pp.151. We discuss AdS$_2$ quantum gravity from an unconventional perspective that emphasizes bulk geometry. In our approach, AdS$_2$ has no boundary, there are no divergences that require renormalization, and the dilaton of JT-gravity can be omitted altogether. The result is the standard Schwarzian theory. However, it may be advantageous that our derivation just relies on conventional AdS/CFT correspondence and effective quantum field theory. For example, it clarifies the symmetry breaking pattern. It also puts the non-compact AdS$_2$ topology on the same footing as compact Riemann surfaces. (10.1007/JHEP11(2023)151)
  DOI : 10.1007/JHEP11(2023)151
• Restoring time-reversal covariance in relaxed hydrodynamics
  
  • Amoretti Andrea
  • Brattan Daniel K
  • Martinoia Luca
  • Matthaiakakis Ioannis
  Physical Review D, American Physical Society, 2023, 108 (5), pp.056003. In hydrodynamics, for generic relaxations, the stress tensor and $U(1)$ charge current two-point functions are not time-reversal covariant. This remains true even if the Martin-Kadanoff procedure happens to yield Onsager reciprocal correlators. We consider linearised relativistic hydrodynamics on Minkowski space in the presence of energy, $U(1)$ charge and momentum relaxation. We then show how one can find the minimal relaxed hydrodynamic framework that does yield two-point functions consistent with time-reversal covariance. We claim the same approach naturally applies to boost agnostic hydrodynamics and its limits (e.g. Carrollian, Galilean and Lifshitz fluids). (10.1103/PhysRevD.108.056003)
  DOI : 10.1103/PhysRevD.108.056003
• Ehlers, Carroll, Charges and Dual Charges
  
  • Mittal Nehal
  • Petropoulos P. Marios
  • Rivera-Betancour David
  • Vilatte Matthieu
  Journal of High Energy Physics, Springer, 2023, 07, pp.065. We unravel the boundary manifestation of Ehlers' hidden Möbius symmetry present in four-dimensional Ricci-flat spacetimes that enjoy a time-like isometry and are Petrov-algebraic. This is achieved in a designated gauge, shaped in the spirit of flat holography, where the Carrollian three-dimensional nature of the null conformal boundary is manifest and covariantly implemented. The action of the Möbius group is local on the space of Carrollian boundary data, among which the Carrollian Cotton tensor plays a predominent role. The Carrollian and Weyl geometric tools introduced for shaping an appropriate gauge, as well as the boundary conformal group, which is $\text{BMS}_4$, allow to define electric/magnetic, leading/subleading towers of charges directly from the boundary Carrollian dynamics and explore their behaviour under the action of the Möbius duality group. (10.1007/JHEP07(2023)065)
  DOI : 10.1007/JHEP07(2023)065
• Bridging the static patches: de Sitter holography and entanglement
  
  • Franken Victor
  • Partouche Hervé
  • Rondeau François
  • Toumbas Nicolaos
  Journal of High Energy Physics, Springer, 2023, 08, pp.074. In the context of de Sitter static-patch holography, two prescriptions have been put forward for holographic entanglement entropy computations, the monolayer and bilayer proposals. In this paper, we reformulate both prescriptions in a covariant way and extend them to include quantum corrections. We argue that the bilayer proposal is self-consistent, while the monolayer proposal exhibits contradictory behavior. In fact, the bilayer proposal leads to a stronger holographic description, in which the full spacetime is encoded on two screens at the cosmological horizons. At the classical level, we find large degeneracies of minimal extremal homologous surfaces, localized at the horizons, which can be lifted by quantum corrections. The entanglement wedges of subregions of the screens exhibit non-trivial behaviors, hinting at the existence of interesting phase transitions and non-locality in the holographic theory. In particular, while each screen encodes its corresponding static patch, we show that the entanglement wedge of the screen with the larger quantum area extends and covers the causal diamond between the screens, with a phase transition occurring when the quantum areas of the screens become equal. We argue that the capacity of the screens to encode the region between them is lost, when these are pushed further in the static patches of the observers and placed on stretched horizons. (10.1007/JHEP08(2023)074)
  DOI : 10.1007/JHEP08(2023)074
• Metal–insulator transition in composition-tuned nickel oxide films
  
  • Fowlie Jennifer
  • Georgescu Alexandru
  • Suter Andreas
  • Mundet Bernat
  • Toulouse Constance
  • Jaouen Nicolas
  • Viret Michel
  • Domínguez Claribel
  • Gibert Marta
  • Salman Zaher
  • Prokscha Thomas
  • Alexander Duncan
  • Kreisel Jens
  • Georges Antoine
  • Millis Andrew
  • Triscone Jean-Marc
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2023, 35 (30), pp.304001. Thin films of the solid solution Nd_1-xLa_xNiO₃ are grown in order to study the expected 0 K phase transitions at a specific composition. We experimentally map out the structural, electronic and magnetic properties as a function of x and a discontinuous, possibly first order, insulator–metal transition is observed at low temperature when x = 0.2. Raman spectroscopy and scanning transmission electron microscopy show that this is not associated with a correspondingly discontinuous global structural change. On the other hand, results from density functional theory (DFT) and combined DFT and dynamical mean field theory calculations produce a 0 K first order transition at around this composition. We further estimate the temperature-dependence of the transition from thermodynamic considerations and find that a discontinuous insulator–metal transition can be reproduced theoretically and implies a narrow insulator–metal phase coexistence with x . Finally, muon spin rotation (µSR) measurements suggest that there are non-static magnetic moments in the system that may be understood in the context of the first order nature of the 0 K transition and its associated phase coexistence regime. (10.1088/1361-648X/accd38)
  DOI : 10.1088/1361-648X/accd38
• Gravitational transverse-momentum distributions
  
  • Lorcé Cédric
  • Song Qin-Tao
  Physics Letters B, Elsevier, 2023, 843, pp.138016. We study the energy-momentum tensor of spin-$0$ and spin-$\frac{1}{2}$ hadrons in momentum space. We parametrize this object in terms of so-called gravitational transverse-momentum distributions, and we identify in the quark sector the relations between the latter and the usual transverse-momentum distributions. Focusing on particular components of the energy-momentum tensor, we study momentum densities, flux of inertia and stress distribution in momentum space, revealing part of the wealth of physical information that can be gained from higher-twist transverse-momentum distributions. (10.1016/j.physletb.2023.138016)
  DOI : 10.1016/j.physletb.2023.138016
• Fractional Topology in interacting 1D Superconductors
  
  • del Pozo Frederick
  • Herviou Loïc
  • Le Hur Karyn
  Physical Review B, American Physical Society, 2023, 107 (15), pp.155134. We investigate the topological phases of two one-dimensional (1D) interacting superconducting wires, and propose topological invariants directly measurable from ground state correlation functions. These numbers remain powerful tools in the presence of couplings and interactions. We show with the density matrix renormalization group that the double critical Ising (DCI) phase discovered in [1] is a fractional topological phase with gapless Majorana modes in the bulk and a one-half topological invariant per wire. Using both numerics and quantum field theoretical methods we show that the phase diagram remains stable in the presence of an inter-wire hopping amplitude $t_{\bot}$ at length scales below $\sim 1/t_{\bot}$. A large inter-wire hopping amplitude results in the emergence of two integer topological phases hosting one edge mode per boundary, shared between both wires. At large interactions the two wires are described by Mott physics, with the $t_{\bot}$ hopping amplitude resulting in a paramagnetic order. (10.1103/PhysRevB.107.155134)
  DOI : 10.1103/PhysRevB.107.155134
• AdS Witten Diagrams to Carrollian Correlators
  
  • Bagchi Arjun
  • Dhivakar Prateksh
  • Dutta Sudipta
  Journal of High Energy Physics, Springer, 2023, 04, pp.135. Carrollian Conformal Field Theories (CFTs) have been proposed as co-dimension one holographic duals to asymptotically flat spacetimes as opposed to Celestial CFTs which are co-dimension two. In this paper, drawing inspiration from Celestial holography, we show by a suitable generalisation of the flat space limit of AdS that keeps track of the previously disregarded null direction, one can reproduce Carrollian CFT correlation functions from AdS Witten diagrams. In particular, considering Witten diagrams in AdS4, we reproduce two and three-point correlation functions for three dimensional Carrollian CFTs in the so-called delta-function branch. Along the way, we construct non-trivial Carrollian three-point functions in the delta-branch by considering a collinear limit. We also obtain a generalised anti-podal matching condition that now depends on the retarded time direction. (10.1007/JHEP04(2023)135)
  DOI : 10.1007/JHEP04(2023)135
• Accessing GPDs through the exclusive photoproduction of a gamma-meson pair
  
  • Duplančić Goran
  • Nabeebaccus Saad
  • Passek-Kumerički Kornelija
  • Pire Bernard
  • Szymanowski Lech
  • Wallon Samuel
  , 2023. We consider the exclusive photo-production of a photon-meson pair with a large invariant mass, working in the QCD factorisation framework. Explicitly, we consider a $ \rho $-meson or a charged $ \pi $ in the final state. This process gives access both to chiral-even GPDs and chiral-odd GPDs, which are not well-known experimentally, especially the latter ones. The computation is performed at leading order and leading twist. We discuss the prospects of measuring them in experiments, focusing on the kinematics at the JLab 12-GeV experiment, and pPb ultra-peripheral collisions at LHC. In particular, the latter gives access to the small $ \xi $ regime of GPDs.
• Resolving the Scales of the Quark-Gluon Plasma with Energy Correlators
  
  • Andres Carlota
  • Dominguez Fabio
  • Kunnawalkam Elayavalli Raghav
  • Holguin Jack
  • Marquet Cyrille
  • Moult Ian
  Physical Review Letters, American Physical Society, 2023, 130 (26), pp.262301. Jets provide us with ideal probes of the quark-gluon plasma (QGP) produced in heavy-ion collisions, since its dynamics at its different scales is imprinted into the multi-scale substructure of the final state jets. We present a new approach to jet substructure in heavy-ion collisions based on the study of correlation functions of energy flow operators. By analysing the two-point correlator of an in-medium quark jet, we demonstrate that the spectra of correlation functions robustly identify the scales defined by the properties of the QGP, particularly those associated with the onset of colour coherence. (10.1103/PhysRevLett.130.262301)
  DOI : 10.1103/PhysRevLett.130.262301
• A New Paradigm for Precision Top Physics: Weighing the Top with Energy Correlators
  
  • Holguin Jack
  • Moult Ian
  • Pathak Aditya
  • Procura Massimiliano
  Physical Review D, American Physical Society, 2023, 107 (11), pp.114002. Final states in collider experiments are characterized by correlation functions, $\langle \mathcal{E}(\vec n_1) \cdots \mathcal{E}(\vec n_k) \rangle$, of the energy flow operator $ \mathcal{E}(\vec n_i)$. These correlation functions typically exhibit a power-law scaling characteristic of asymptotically free Quantum Chromodynamics. In this Letter, we show that the top quark imprints itself as a peak in the three-point correlation function at an angle $\zeta \sim m_t^2/p_T^2$, with $m_t$ the top quark mass and $p_T$ its transverse momentum. This provides direct access to one of the most important parameters of the Standard Model in one of the field theoretically simplest observables. We show that the three-point correlator allows us to simultaneously achieve high sensitivity to the top mass and high insensitivity to soft physics and underlying event contamination. We find it an amusing turn of fate that correlation functions which have received the most interest in the context of conformal field theories, in fact hold the key to understanding the heaviest known particle. (10.1103/PhysRevD.107.114002)
  DOI : 10.1103/PhysRevD.107.114002
• Singular Supertranslations and Chern-Simons Theory on the Black Hole Horizon
  
  • Akhoury Ratindranath
  • Choi Sangmin
  • Perry Malcolm J.
  Physical Review D, American Physical Society, 2023, 107 (8), pp.085019. We construct the standard and dual supertranslation charges on the future horizon of the Schwarzschild black hole, using the first-order formulation of gravity with the Holst action. The Dirac bracket algebra of standard and dual supertranslation charges is shown to exhibit a central term in the presence of singularities in the two-sphere function associated with supertranslation. We show that one can cancel this anomalous term and restore the asymptotic symmetry algebra by introducing a gravitational Chern-Simons theory on the horizon. This demonstrates that consistency of the asymptotic symmetry algebra requires a new structure on the horizon. (10.1103/PhysRevD.107.085019)
  DOI : 10.1103/PhysRevD.107.085019
• Formation of CuO$_2$ sublattices by suppression of interlattice correlations in tetragonal CuO
  
  • Bramberger Max
  • Bacq-Labreuil Benjamin
  • Grundner Martin
  • Biermann Silke
  • Schollwöck Ulrich
  • Paeckel Sebastian
  • Lenz Benjamin
  SciPost Physics, SciPost Foundation, 2023, 14 (1), pp.010. We investigate the tetragonal phase of the binary transition metal oxide CuO (t-CuO) within the context of cellular dynamical mean-field theory. Due to its strong antiferromagnetic correlations and simple structure, analysing the physics of t-CuO is of high interest as it may pave the way towards a more complete understanding of high temperature superconductivity in hole-doped antiferromagnets. In this work we give a formal justification for the weak coupling assumption that has previously been made for the interconnected sublattices within a single layer of t-CuO by studying the non-local self-energies of the system. We compute momentum-resolved spectral functions using a Matrix Product State (MPS)-based impurity solver directly on the real axis, which does not require any numerically ill-conditioned analytic continuation. The agreement with photoemission spectroscopy indicates that a single band Hubbard model is sufficient to capture the material's low energy physics. We perform calculations on a range of different temperatures, finding two magnetic regimes, for which we identify the driving mechanism behind their respective insulating state. Finally, we show that in the hole-doped regime the sublattice structure of t-CuO has interesting consequences on the symmetry of the superconducting state. (10.21468/SciPostPhys.14.1.010)
  DOI : 10.21468/SciPostPhys.14.1.010
• Reconciling scaling of the optical conductivity of cuprate superconductors with Planckian resistivity and specific heat
  
  • Michon Bastien
  • Berthod Christophe
  • Rischau Carl Willem
  • Ataei Amirreza
  • Chen Lu
  • Komiya Seiki
  • Ono Shimpei
  • Taillefer Louis
  • van der Marel Dirk
  • Georges Antoine
  Nature Communications, Nature Publishing Group, 2023, 14 (1), pp.3033. Materials tuned to a quantum critical point display universal scaling properties as a function of temperature T and frequency ω. A long-standing puzzle regarding cuprate superconductors has been the observed power-law dependence of optical conductivity with an exponent smaller than one, in contrast to T-linear dependence of the resistivity and ω-linear dependence of the optical scattering rate. Here, we present and analyze resistivity and optical conductivity of La$_{2−x}$Sr$_{x}$CuO$_{4}$ with x = 0.24. We demonstrate ℏω/k$_{B}$T scaling of the optical data over a wide range of frequency and temperature, T-linear resistivity, and optical effective mass proportional to $\sim \ln T$ corroborating previous specific heat experiments. We show that a T, ω-linear scaling Ansatz for the inelastic scattering rate leads to a unified theoretical description of the experimental data, including the power-law of the optical conductivity. This theoretical framework provides new opportunities for describing the unique properties of quantum critical matter. (10.1038/s41467-023-38762-5)
  DOI : 10.1038/s41467-023-38762-5
• Quantum computing with and for many-body physics
  
  • Ayral Thomas
  • Besserve Pauline
  • Lacroix Denis
  • Ruiz Guzman Edgar Andres
  The European physical journal. A, Hadrons and Nuclei, EDP Sciences ; Springer [1998-....], 2023, 59 (10), pp.227. Quantum computing technologies are making steady progress. This has opened new opportunities for tackling problems whose complexity prevents their description on classical computers. A prototypical example of these complex problems are interacting quantum many-body systems: on the one hand, these systems are known to become rapidly prohibitive to describe using classical computers when their size increases. On the other hand, these systems are precisely those which are used in the laboratory to build quantum computing platforms. This arguably makes them one of the most promising early use cases of quantum computing. In this review, we explain how quantum many-body systems are used to build quantum processors, and how, in turn, current and future quantum processors can be used to describe large many-body systems of fermions such as electrons and nucleons. The review includes an introduction to analog and digital quantum devices, the mapping of Fermi systems and their Hamiltonians onto qubit registers, as well as an overview of methods to access their static and dynamical properties. We also highlight some aspects related to entanglement, and touch on the description, influence and processing of decoherence in quantum devices. (10.1140/epja/s10050-023-01141-1)
  DOI : 10.1140/epja/s10050-023-01141-1
• Quantum Field Theory in AdS Space instead of Lehmann-Symanzik-Zimmerman Axioms
  
  • van Rees Balt C
  • Zhao Xiang
  Physical Review Letters, American Physical Society, 2023, 130 (19), pp.191601. The boundary correlation functions for a quantum field theory (QFT) in a fixed anti–de Sitter (AdS) background should reduce to <math display="inline"><mrow><mi>S</mi></mrow></math>-matrix elements in the flat-space limit. We consider this procedure in detail for four-point functions. With minimal assumptions we rigorously show that the resulting <math display="inline"><mrow><mi>S</mi></mrow></math>-matrix element obeys a dispersion relation, the nonlinear unitarity conditions, and the Froissart-Martin bound. QFT in AdS thus provides an alternative route to fundamental QFT results that normally rely on the LSZ axioms. (10.1103/PhysRevLett.130.191601)
  DOI : 10.1103/PhysRevLett.130.191601