Publications

2023

• Adiabatic Deformations of Quantum Hall Droplets
  
  • Oblak Blagoje
  • Estienne Benoit
  SciPost Physics, SciPost Foundation, 2023, 15 (4), pp.159. We consider area-preserving deformations of the plane, acting on electronic wavefunctions through "quantomorphisms" that change both the underlying metric and the confining potential. We show that adiabatic sequences of such transformations produce Berry phases that can be written in closed form in terms of the many-body current and density, even in the presence of interactions. For a large class of deformations that generalize squeezing and shearing, the leading piece of the phase is a super-extensive Aharonov-Bohm term (proportional to N$^2$ for N electrons) in the thermodynamic limit. Its gauge-invariant subleading partner only measures the current, whose dominant contribution to the phase stems from a jump at the edge in the limit of strong magnetic fields. This results in a finite Berry curvature per unit area, reminiscent of the Hall viscosity. We show that the latter is in fact included in our formalism, bypassing its standard derivation on a torus and suggesting realistic experimental setups for its observation in quantum simulators. (10.21468/SciPostPhys.15.4.159)
  DOI : 10.21468/SciPostPhys.15.4.159
• On the Inaccessibility of Time Machines
  
  • Tomašević Marija
  Universe, MDPI, 2023, 9 (4), pp.159. We will explain why time machines, although allowed in General Relativity, cannot be accessed by observers once we include quantum effects. Moreover, we will show that traversable wormholes cannot be turned into time machines without invoking the effects of quantum gravity. (10.3390/universe9040159)
  DOI : 10.3390/universe9040159
• Large $D$ Holographic Collisions
  
  • Luna Raimon
  • Sanchez-Garitaonandia Mikel
  Journal of High Energy Physics, Springer, 2023, 02, pp.147. We study collisions of Gaussian mass blobs in the large $D$ limit as a model for holographic shockwave collisions. The simplicity of the formalism allows us to perform the first 4+1 collisions in Einstein-Maxwell theory. We explore several collision scenarios with different blob shapes, impact parameters and charge values and find that collisions with impact parameter below the transverse width of the blobs are equivalent under rescaling. We also observe that charge weakly affects the rest of quantities. Finally, we study the entropy generated during collisions, both by charge diffusion and viscous dissipation. Multiple stages of linear entropy growth are identified, whose rates are not independent of the initial conditions. (10.1007/JHEP02(2023)147)
  DOI : 10.1007/JHEP02(2023)147
• Unbiasing time-dependent Variational Monte Carlo by projected quantum evolution
  
  • Sinibaldi Alessandro
  • Giuliani Clemens
  • Carleo Giuseppe
  • Vicentini Filippo
  Quantum, Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften, 2023, 7, pp.1131. We analyze the accuracy and sample complexity of variational Monte Carlo approaches to simulate the dynamics of many-body quantum systems classically. By systematically studying the relevant stochastic estimators, we are able to: (i) prove that the most used scheme, the time-dependent Variational Monte Carlo (tVMC), is affected by a systematic statistical bias or exponential sample complexity when the wave function contains some (possibly approximate) zeros, an important case for fermionic systems and quantum information protocols; (ii) show that a different scheme based on the solution of an optimization problem at each time step is free from such problems; (iii) improve the sample complexity of this latter approach by several orders of magnitude with respect to previous proofs of concept. Finally, we apply our advancements to study the high-entanglement phase in a protocol of non-Clifford unitary dynamics with local random measurements in 2D, first benchmarking on small spin lattices and then extending to large systems. (10.22331/q-2023-10-10-1131)
  DOI : 10.22331/q-2023-10-10-1131
• 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 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
• Magic Fermions: Carroll and Flat Bands
  
  • Bagchi Arjun
  • Banerjee Aritra
  • Basu Rudranil
  • Islam Minhajul
  • Mondal Saikat
  Journal of High Energy Physics, Springer, 2023, 03, pp.227. The Carroll algebra is constructed as the $c\to0$ limit of the Poincare algebra and is associated to symmetries on generic null surfaces. In this paper, we begin investigations of Carrollian fermions or fermions defined on generic null surfaces. Due to the availability of two different (degenerate) metrics on Carroll spacetimes, there is the possibility of two different versions of Carroll Clifford algebras. We consider both possibilities and construct explicit representations of Carrollian gamma matrices and show how to build higher spacetime dimensional representations out of lower ones. Actions for Carroll fermions are constructed with these gamma matrices and the properties of these actions are investigated. We show that in condensed matter systems where the dispersion relation becomes trivial i.e. the energy is not dependent on momentum and bands flatten out, Carroll symmetry generically appears. We give explicit examples of this including that of twisted bi-layer graphene, where superconductivity appears at so called magic angles and connect this to Carroll fermions. (10.1007/JHEP03(2023)227)
  DOI : 10.1007/JHEP03(2023)227
• The gravitational form factors of the electron in quantum electrodynamics
  
  • Freese Adam
  • Metz Andreas
  • Pasquini Barbara
  • Rodini Simone
  Physics Letters B, Elsevier, 2023, 839, pp.137768. We calculate the gravitational form factors of the electron at one loop in quantum electrodynamics, decomposing these into contributions from the electron and photon parts of the energy-momentum tensor. Ultraviolet divergences are removed through renormalization in the $\overline{\text{MS}}$ scheme. Infrared divergences are isolated and results are given in both dimensional regularization and photon-mass regularization. The form factors contain information about the electron's energy and angular momentum structure in QED, as well as its mass radius. Whenever possible, we compare our results with the existing literature. (10.1016/j.physletb.2023.137768)
  DOI : 10.1016/j.physletb.2023.137768
• Carrollian Origins of Bjorken Flow
  
  • Bagchi Arjun
  • Kolekar Kedar S.
  • Shukla Ashish
  Physical Review Letters, American Physical Society, 2023, 130 (24), pp.241601. Bjorken flow is among the simplest phenomenological models of fluids moving near the velocity of light. Carroll symmetry, on the other hand, arises as a contraction of Poincare group when the speed of light is dialled to zero. In this work, we show that Bjorken flow and the phenomenological approximations that go into it are completely captured by Carrollian fluids. This is based on the surprising and yet surprisingly simple observation that Carrollian symmetries arise on generic null surfaces and a fluid moving with the velocity of light is restricted to move on a null surface, thereby naturally inheriting Carrollian symmetries. Thus, contrary to expectations, Carrollian hydrodynamics is not exotic, but rather ubiquitous, and provides a concrete framework for fluids moving at velocities near the velocity of light. (10.1103/PhysRevLett.130.241601)
  DOI : 10.1103/PhysRevLett.130.241601
• Protected Topological Nodal Ring Semimetal in Graphene
  
  • Le Hur Karyn
  • Al Saati Sariah
  Physical Review B, American Physical Society, 2023, 107 (16), pp.165407. Graphene is a two-dimensional Dirac semimetal showing interesting properties as a result of its dispersion relation with both quasiparticles and quasiholes or matter and anti-matter. We introduce a topological nodal ring semimetal in graphene with a quantized quantum Hall response, a robust one-dimensional chiral edge mode and a quadratic Fermi-liquid spectrum for the quasiparticles and quasiholes in the bulk. The bulk band degeneracy at the Fermi energy is protected through a Z2 symmetry related to the two spin polarizations of an electron and a double-orthogonality structure in the sublattice and spin quantum numbers of the two crossing eigenstates. The system may have applications in nano-electronics and in quantum mechanical entanglement applied to band theory. (10.1103/PhysRevB.107.165407)
  DOI : 10.1103/PhysRevB.107.165407
• Nucleon relativistic polarization and magnetization distributions
  
  • Chen Yi
  • Lorcé Cédric
  Physical Review D, American Physical Society, 2023, 107 (9), pp.096003. As a follow up of our work on the electromagnetic four-current, we study for the first time the relativistic polarization and magnetization spatial distributions inside a spin-$\frac{1}{2}$ target within the quantum phase-space approach. While the polarization-magnetization tensor is usually defined in terms of the Gordon decomposition of the electromagnetic four-current, a Breit frame analysis reveals that a physically simpler and more natural picture of the system arises when the polarization-magnetization tensor is instead defined in terms of a Sachs decomposition. Relativistic polarization and magnetization distributions for a moving target are compared with their light-front counterparts. In particular, we show that the genuine light-front magnetization distributions are defined in terms of Fourier transforms of the Sachs magnetic form factor, rather than the Pauli form factor as suggested earlier in the literature. We finally illustrate our results in the case of a nucleon using the electromagnetic form factors extracted from experimental data. (10.1103/PhysRevD.107.096003)
  DOI : 10.1103/PhysRevD.107.096003
• 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
• Gyroscopic Gravitational Memory
  
  • Seraj Ali
  • Oblak Blagoje
  Journal of High Energy Physics, Springer, 2023, 11, pp.057. We study the motion of a gyroscope located far away from an isolated gravitational source in an asymptotically flat space-time. As seen from a local frame `tied to distant stars', the gyroscope precesses when gravitational waves cross its path, resulting in a net `orientation memory' that carries information on the wave profile. The effect is related to asymptotic symmetries: at leading order in the inverse distance to the source, the precession rate coincides with the (covariant) dual mass aspect, providing a celestially local measurement protocol for dual supertranslation charges. Furthermore, the net gyroscopic memory is derived from flux-balance equations for superrotations and contains an extra flux generating electric-magnetic duality. The spin memory effect is reproduced as a special case. (10.1007/JHEP11(2023)057)
  DOI : 10.1007/JHEP11(2023)057
• Zero sound and higher-form symmetries in compressible holographic phases
  
  • Davison Richard A.
  • Goutéraux Blaise
  • Mefford Eric
  Journal of High Energy Physics, Springer, 2023, 2023, pp.40. Certain holographic states of matter with a global U(1) symmetry support a sound mode at zero temperature, caused neither by spontaneous symmetry breaking of the global U(1) nor by the emergence of a Fermi surface in the infrared. In this work, we show that such a mode is also found in zero density holographic quantum critical states. We demonstrate that in these states, the appearance of a zero temperature sound mode is the consequence of a mixed `t Hooft anomaly between the global U(1) symmetry and an emergent higher-form symmetry. At non-zero temperatures, the presence of a black hole horizon weakly breaks the emergent symmetry and gaps the collective mode, giving rise to a sharp Drude-like peak in the electric conductivity. A similar gapped mode arises at low temperatures for non-zero densities when the state has an emergent Lorentz symmetry, also originating from an approximate anomalous higher-form symmetry. However, in this case the collective excitation does not survive at zero temperature where, instead, it dissolves into a branch cut. We comment on the relation between our results and the application of the Luttinger theorem to compressible holographic states of matter. (10.1007/JHEP12(2023)040)
  DOI : 10.1007/JHEP12(2023)040
• Collinear matching for next-to-leading power transverse-momentum distributions
  
  • Rodini Simone
  • Alvaro Alessio Carmelo
  • Pasquini Barbara
  Physics Letters B, Elsevier, 2023, 845, pp.138163. Phenomenological studies of transverse momentum dependent (TMD) parton distributions rely on the expansion in small values of the transverse separation of fields, where TMD parton distributions match onto collinear parton distribution functions. In this work, we derive this expansion at tree-level for the genuine next-to-leading power quark-gluon-quark TMDs, taking into account all the target mass corrections. We find that only a limited number of TMD parton distributions exhibit matching to twist-three collinear distributions, leading to a significant simplification in the analysis of the structure functions of semi-inclusive deep inelastic scattering. (10.1016/j.physletb.2023.138163)
  DOI : 10.1016/j.physletb.2023.138163
• Non-Lorentzian Kač-Moody Algebras
  
  • Bagchi Arjun
  • Chatterjee Ritankar
  • Kaushik Rishabh
  • Saha Amartya
  • Sarkar Debmalya
  Journal of High Energy Physics, Springer, 2023, 03, pp.041. We investigate two dimensional (2d) quantum field theories which exhibit Non- Lorentzian Kač-Moody (NLKM) algebras as their underlying symmetry. Our investigations encompass both 2d Galilean (speed of light $c \rightarrow \infty$) and Carrollian ($c \rightarrow 0$) CFTs with additional number of infinite non-Abelian currents, stemming from an isomorphism between the two algebras. We alternate between an intrinsic and a limiting analysis. Our NLKM algebra is constructed first through a contraction and then derived from an intrinsically Carrollian perspective. We then go on to use the symmetries to derive a Non-Lorentzian (NL) Sugawara construction and ultimately write down the NL equivalent of the Knizhnik Zamolodchikov equations. All of these are also derived from contractions, thus providing a robust cross-check of our analyses. (10.1007/JHEP03(2023)041)
  DOI : 10.1007/JHEP03(2023)041
• Duality of Orthogonal and Symplectic Random Tensor Models
  
  • Gurau Razvan
  • Keppler Hannes
  Ann.Inst.H.Poincare D Comb.Phys.Interact., 2023, 12 (2), pp.319-362. The groups $O(N)$ and $Sp(N)$ are related by an analytic continuation to negative values of $N$, $O(-N)\simeq Sp(N)$. This duality has been studied for vector models, $SO(N)$ and $Sp(N)$ gauge theories, as well as some random matrix ensembles. We extend this duality to real random tensor models of arbitrary order $D$ with no symmetry under permutation of the indices and with quartic interactions. The $N$ to $-N$ duality is shown to hold graph by graph to all orders in perturbation theory for the partition function, the free energy and the connected two point function. (10.4171/aihpd/177)
  DOI : 10.4171/aihpd/177
• Paramagnon dispersion and damping in doped Na$_x$Ca$_{2-x}$CuO$_2$Cl$_2$
  
  • Lebert Blair W.
  • Bacq-Labreuil Benjamin
  • Dean Mark P. M.
  • Ruotsalainen Kari
  • Nicolaou Alessandro
  • Huotari Simo
  • Yamada Ikuya
  • Yamamoto Hajime
  • Azuma Masaki
  • Brookes Nicholas B.
  • Yakhou Flora
  • Miao Hu
  • Santos-Cottin David
  • Lenz Benjamin
  • Biermann Silke
  • d'Astuto Matteo
  Physical Review B, American Physical Society, 2023, 108 (2), pp.024506. Using Resonant Inelastic X-ray Scattering, we measure the paramagnon dispersion and damping of undoped, antiferromagnetic Ca$_2$CuO$_2$Cl$_2$ as well as doped, superconducting Na$_x$Ca$_{2-x}$CuO$_2$Cl$_2$. Our estimation of the spin-exchange parameter and width of the paramagnon peak at the zone boundary $X=(0.5,0)$ confirms that no simple relation can be drawn between these parameters and the critical temperature $T_\mathrm{c}$. Consistently with other cuprate compounds, we show that upon doping there is a slight softening at $(0.25,0)$, but not at the zone boundary $X$. In combination with these measurements we perform calculations of the dynamical spin structure factor of the one-band Hubbard model using cluster dynamical mean-field theory. The calculations are in excellent agreement with the experiment in the undoped case, both in terms of energy position and width. While the increase in width is also captured upon doping, the dynamical spin structure factor shows a sizable softening at $X$, which provides insightful information on the length-scale of the spin fluctuations in doped cuprates. (10.1103/PhysRevB.108.024506)
  DOI : 10.1103/PhysRevB.108.024506
• Symmetries in Celestial CFT$_d$
  
  • Pano Yorgo
  • Puhm Andrea
  • Trevisani Emilio
  Journal of High Energy Physics, Springer, 2023, 07, pp.076. We use tools from conformal representation theory to classify the symmetries associated to conformally soft operators in celestial CFT (CCFT) in general dimensions $d$. The conformal multiplets in $d>2$ take the form of celestial necklaces whose structure is much richer than the celestial diamonds in $d=2$, it depends on whether $d$ is even or odd and involves mixed-symmetric tensor representations of $SO(d)$. The existence of primary descendants in CCFT multiplets corresponds to (higher derivative) conservation equations for conformally soft operators. We lay out a unified method for constructing the conserved charges associated to operators with primary descendants. In contrast to the infinite local symmetry enhancement in CCFT${}_2$, we find the soft symmetries in CCFT${}_{d>2}$ to be finite-dimensional. The conserved charges that follow directly from soft theorems are trivial in $d>2$, while non-trivial charges associated to (generalized) currents and stress tensor are obtained from the shadow transform of soft operators which we relate to (an analytic continuation of) a specific type of primary descendants. We aim at a pedagogical discussion synthesizing various results in the literature. (10.1007/JHEP07(2023)076)
  DOI : 10.1007/JHEP07(2023)076
• U(1) quasi-hydrodynamics: Schwinger-Keldysh effective field theory and holography
  
  • Baggioli Matteo
  • Bu Yanyan
  • Ziogas Vaios
  Journal of High Energy Physics, Springer, 2023, 09, pp.019. We study the quasi-hydrodynamics of a system with a softly broken $U(1)$ global symmetry using effective field theory (EFT) and holographic methods. In the gravity side, we consider a holographic Proca model in the limit of small bulk mass, which is responsible for a controllable explicit breaking of the $U(1)$ global symmetry in the boundary field theory. We perform a holographic Schwinger-Keldysh analysis, which allows us to derive the form of the boundary effective action in presence of dissipation. We compare our results with the previously proposed EFT and hydrodynamic theories, and we confirm their validity by computing the low-energy quasi-normal modes spectrum analytically and numerically. Additionally, we derive the broken holographic Ward identity for the $U(1)$ current, and discuss the recently proposed novel transport coefficients for systems with explicitly broken symmetries. The setup considered is expected to serve as a toy model for more realistic situations where quasi-hydrodynamics is at work, such as axial charge relaxation in QCD, spin relaxation in relativistic systems, electric field relaxation in magneto-hydrodynamics, or momentum relaxation in condensed matter systems. (10.1007/JHEP09(2023)019)
  DOI : 10.1007/JHEP09(2023)019
• Small parameters in infrared QCD: The pion decay constant
  
  • Peláez Marcela
  • Reinosa Urko
  • Serreau Julien
  • Wschebor Nicolás
  Physical Review D, American Physical Society, 2023, 107 (5), pp.054025. We continue our investigation of the QCD dynamics in terms of the Curci-Ferrari effective Lagrangian, a deformation of the Faddeev-Popov one in the Landau gauge with a tree-level gluon mass term. In a previous work we have studied the dynamics of chiral symmetry breaking at the level of the quark propagator and, in particular, the dynamical generation of a constituent quark mass. In the present article, we study the associated Goldstone mode, the pion, and we compute the pion decay constant in the chiral limit. Our approach exploits the fact that the coupling (defined in the Taylor scheme) in the pure gauge sector is perturbative, as observed in lattice simulations which, together with a $1/N_c$-expansion, allows for a systematic, controllable approximation scheme in the low energy regime of QCD. At leading order, this leads to the well-known rainbow-ladder resummation. We study the region of parameter space of the model that gives physical values of the pion decay constant. This allows one to constrain the gluon mass parameter as a function of the coupling using a physically measured quantity. (10.1103/PhysRevD.107.054025)
  DOI : 10.1103/PhysRevD.107.054025
• Low projectile density contributions in the dilute-dense CGC framework for two-particle correlations
  
  • Kohara Anderson Kendi
  • Marquet Cyrille
  • Vila Víctor
  Journal of High Energy Physics, Springer, 2023, 10, pp.159. At leading-order, the standard dilute-dense Color Glass Condensate formula used for two-particle correlations in proton-nucleus collisions, whose symmetries prevent the generation of odd azimuthal anisotropy harmonics, is the dilute projectile limit of the dense-dense formalism. However, when the projectile is genuinely dilute, the complete formulation contains additional contributions at the same leading order in the strong coupling constant. In this work we investigate those low projectile density contributions that are relevant when the particles are produced at forward rapidities. We find that they are responsible for non-zero odd harmonics which are negative, in qualitative agreement with recent experimental measurements at the Relativistic Heavy-Ion Collider. (10.1007/JHEP10(2023)159)
  DOI : 10.1007/JHEP10(2023)159