Publications

2023

• 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
• Dynamical mean-field theory for the Hubbard-Holstein model on a quantum device
  
  • Backes Steffen
  • Murakami Yuta
  • Sakai Shiro
  • Arita Ryotaro
  Physical Review B, American Physical Society, 2023, 107 (16), pp.165155. Recent developments in quantum hardware and quantum algorithms have made it possible to utilize the capabilities of current noisy intermediate-scale quantum devices for addressing problems in quantum chemistry and condensed matter physics. Here we report a demonstration of solving the dynamical mean-field theory (DMFT) impurity problem for the Hubbard-Holstein model on the IBM 27-qubit Quantum Falcon Processor Kawasaki, including self-consistency of the DMFT equations. This opens up the possibility to investigate strongly correlated electron systems coupled to bosonic degrees of freedom and impurity problems with frequency-dependent interactions. The problem involves both fermionic and bosonic degrees of freedom to be encoded on the quantum device, which we solve using a recently proposed Krylov variational quantum algorithm to obtain the impurity Green's function. We find the resulting spectral function to be in good agreement with the exact result, exhibiting both correlation and plasmonic satellites and significantly surpassing the accuracy of standard Trotter-expansion approaches. Our results provide an essential building block to study electronic correlations and plasmonic excitations on future quantum computers with modern ab initio techniques. (10.1103/PhysRevB.107.165155)
  DOI : 10.1103/PhysRevB.107.165155
• Femtosecond laser-induced sub-wavelength plasma inside dielectrics. III. Terahertz radiation emission
  
  • Ardaneh Kazem
  • Nishikawa Ken-Ichi
  • Giust Remo
  • Morel Benoit
  • Charpin Pierre-Jean
  • Couairon Arnaud
  • Bonnaud Guy
  • Courvoisier Francois
  Physics of Plasmas, American Institute of Physics, 2023, 30 (1), pp.013301. Electromagnetic radiation within the terahertz (THz) frequency range is of great interest for applications in remote sensing and time-domain spectroscopy. The laser-induced plasmas are promising mediums for generating THz radiation. It has been recently reported that focusing femtosecond Bessel pulses inside dielectrics induces a high aspect ratio over-critical plasmas. Here, we show that the intense resonantly driven electrostatic fields at the so-called critical surface lead to THz radiation emission. Through three-dimensional particle-in-cell simulation and analytical derivation, we have investigated the emission of THz radiation. We show that the THz radiation is associated with a hot population of electrons trapped in ambipolar electric fields of the double layers. (10.1063/5.0126427)
  DOI : 10.1063/5.0126427
• BMS Field Theories with $\mathfrak{u}(1)$ Symmetry
  
  • Bagchi Arjun
  • Chatterjee Ritankar
  • Kaushik Rishabh
  • Pal Sanchari
  • Riegler Max
  • Sarkar.A Debmalya
  Physical Review D, American Physical Society, 2023, 107 (10), pp.106019. We investigate quantum field theories in two dimensions (2d) with an underlying Bondi-van der Burgh-Metzner-Sachs (BMS) symmetry augmented by $\mathfrak{u}(1)$ currents. These field theories are expected to holographically capture features of charged versions of cosmological solutions in asymptotically flat 3d spacetimes called Flat Space Cosmologies (FSCs). We conduct a study of the modular properties of these field theories. The characters for the highest weight representations of the symmetry algebra are constructed, and the partition function of the theory is obtained from them. We derive the density of (primary) states and find the entropy and asymptotic values of the structure constants exploiting the modular properties of the partition function and the torus one-point function. The expression for the asymptotic structure constants shows shifts in the weights and one of the central terms and an extra phase compared to the earlier results in the literature for BMS invariant theories without $\mathfrak{u}(1)$ currents present. We reproduce our field results for the structure constants by a bulk computation involving a scalar probe in the background of a charged FSC. (10.1103/PhysRevD.107.106019)
  DOI : 10.1103/PhysRevD.107.106019
• Holographic duals of evaporating black holes
  
  • Emparan Roberto
  • Luna Raimon
  • Suzuki Ryotaku
  • Tomašević Marija
  • Way Benson
  Journal of High Energy Physics, Springer, 2023, 05, pp.182. We describe the dynamical evaporation of a black hole as the classical evolution in time of a black hole in an Anti-de Sitter braneworld. A bulk black hole whose horizon intersects the brane yields the classical bulk dual of a black hole coupled to quantum conformal fields. The evaporation of this black hole happens when the bulk horizon slides off the brane, making the horizon on the brane shrink. We use a large-D effective theory of the bulk Einstein equations to solve the time evolution of these systems. With this method, we study the dual evaporation of a variety of black holes interacting with colder radiation baths. We also obtain the dual of the collapse of holographic radiation to form a black hole on the brane. Finally, we discuss the evolution of the Page curve of the radiation in our evaporation setups, with entanglement islands appearing and then shrinking during the decreasing part of the curve. (10.1007/JHEP05(2023)182)
  DOI : 10.1007/JHEP05(2023)182
• Horizon Strings as 3d Black Hole Microstates
  
  • Bagchi Arjun
  • Grumiller Daniel
  • Sheikh-Jabbari M.M.
  SciPost Physics, SciPost Foundation, 2023, 15 (5), pp.210. We construct microstates of 3d black holes in the Hilbert space of tensionless null strings with non-zero winding along the direction transversal to the horizon. Their combinatorics is compatible with the Bekenstein-Hawking entropy and its semiclassical logarithmic corrections. (10.21468/SciPostPhys.15.5.210)
  DOI : 10.21468/SciPostPhys.15.5.210
• Universal device for two-qubit entangled measurements via photonic quantum walks
  
  • Yan Wen-Zhe
  • Hou Zhibo
  • Tang Jun-Feng
  • Xiang Guo-Yong
  • Li Chuan-Feng
  • Guo Guang-Can
  • Renou Marc-Olivier
  Physical Review Applied, American Physical Society, 2023, 20 (4), pp.044032. Sophisticated positive-operator-valued measures (POVMs) are fundamental to obtain a quantum advantage in many informational problems but are difficult to implement. We design a universal measurement device composed of cascaded quantum-walk modules able to realize arbitrary entangled POVMs on two qubits. Only parameters in the modules need reprogramming for different POVMs. We apply our device to the task of direction guessing, realizing nine different five-outcome entangled measurements (fidelities above 0.9850) via nine-step photonic quantum walks, recovering optimal direction guessing from nonideal input states. Our work marks an important step toward building a universal versatile quantum measurement device able to implement optimal measurements for various quantum information tasks. (10.1103/PhysRevApplied.20.044032)
  DOI : 10.1103/PhysRevApplied.20.044032
• Temperature Dependence of Spin and Charge Orders in the Doped Two-Dimensional Hubbard Model
  
  • Xiao Bo
  • He Yuan-Yao
  • Georges Antoine
  • Zhang Shiwei
  Physical Review X, American Physical Society, 2023, 13 (1), pp.011007. Competing and intertwined orders including inhomogeneous patterns of spin and charge are observed in many correlated electron materials, such as high-temperature superconductors. Introducing a new development of the constrained-path auxiliary-field quantum Monte Carlo method, we study the interplay between thermal and quantum fluctuations in the two-dimensional Hubbard model. We obtain an accurate and systematic characterization of the evolution of the spin and charge correlations as a function of temperature T and how it connects to the ground state, at three representative hole doping levels δ=1/5, 1/8, and 1/10. We find increasing short-range commensurate antiferromagnetic correlations as T is lowered. As the correlation length grows sufficiently large, a modulated spin-density wave (SDW) appears. At δ=1/5 and U/t=6, the SDW saturates and remains short-ranged as T→0. In contrast, at δ=1/8, 1/10 and U/t=8, this evolves into a ground-state stripe phase. We study the relation between spin and charge orders and find that formation of charge order appears to be driven by that of the spin order. We identify a finite-temperature phase transition below which charge ordering sets in and discuss the implications of our results for the nature of this transition. (10.1103/PhysRevX.13.011007)
  DOI : 10.1103/PhysRevX.13.011007
• Human-environment feedback and the consistency of proenvironmental behavior
  
  • Ecotière Claire
  • Billiard Sylvain
  • André Jean-Baptiste
  • Collet Pierre
  • Ferrière Régis
  • Méléard Sylvie
  PLoS Computational Biology, PLOS, 2023, 19 (9), pp.e1011429. Addressing global environmental crises such as anthropogenic climate change requires the consistent adoption of proenvironmental behavior by a large part of a population. Here, we develop a mathematical model of a simple behavior-environment feedback loop to ask how the individual assessment of the environmental state combines with social interactions to influence the consistent adoption of proenvironmental behavior, and how this feeds back to the perceived environmental state. In this stochastic individual-based model, individuals can switch between two behaviors, ‘active’ (or actively proenvironmental) and ‘baseline’, differing in their perceived cost (higher for the active behavior) and environmental impact (lower for the active behavior). We show that the deterministic dynamics and the stochastic fluctuations of the system can be approximated by ordinary differential equations and a Ornstein-Uhlenbeck type process. By definition, the proenvironmental behavior is adopted consistently when, at population stationary state, its frequency is high and random fluctuations in frequency are small. We find that the combination of social and environmental feedbacks can promote the spread of costly proenvironmental behavior when neither, operating in isolation, would. To be adopted consistently, strong social pressure for proenvironmental action is necessary but not sufficient—social interactions must occur on a faster timescale compared to individual assessment, and the difference in environmental impact must be small. This simple model suggests a scenario to achieve large reductions in environmental impact, which involves incrementally more active and potentially more costly behavior being consistently adopted under increasing social pressure for proenvironmentalism. (10.1371/journal.pcbi.1011429)
  DOI : 10.1371/journal.pcbi.1011429
• Multiplicity fluctuations and correlations in 5.02 TeV p+Pb collisions at zero impact parameter
  
  • Pepin Mathis
  • Christiansen Peter
  • Munier Stéphane
  • Ollitrault Jean-Yves
  Physical Review C, American Physical Society, 2023, 107 (2), pp.024902. We present a Bayesian method to reconstruct event-by-event multiplicity fluctuations and rapidity correlations in p+Pb collisions at zero impact parameter from minimum-bias data, without assuming any model of the collision dynamics. We test it on Monte Carlo simulations with the Angantyr model, then apply it to ATLAS data on the distribution of charged multiplicity and transverse energy in p+Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Fluctuations in $b=0$ collisions are quantum fluctuations which originate mostly from the proton wave function, and therefore have the potential to constrain the subnucleonic structure of the proton. The Angantyr model is found to overestimate fluctuations. In addition, we find that as the rapidity increases (towards the Pb-going side), not only the multiplicity density increases, but also its relative event-by-event fluctuation. This counter-intuitive phenomenon is also observed in simulations with Angantyr, and with the QCD dipole model, where its origin can be traced back to the branching process through which gluons are produced. (10.1103/PhysRevC.107.024902)
  DOI : 10.1103/PhysRevC.107.024902
• Thermodynamic Phase Diagram of Two-Dimensional Bosons in a Quasicrystal Potential
  
  • Zhu Zhaoxuan
  • Yao Hepeng
  • Sanchez-Palencia Laurent
  Physical Review Letters, American Physical Society, 2023, 130 (22), pp.220402. Quantum simulation of quasicrystals in synthetic bosonic matter now paves the way to the exploration of these intriguing systems in wide parameter ranges. Yet thermal fluctuations in such systems compete with quantum coherence, and significantly affect the zero-temperature quantum phases. Here we determine the thermodynamic phase diagram of interacting bosons in a two-dimensional, homogeneous quasicrystal potential. Our results are found using quantum Monte Carlo simulations. Finite-size scaling is carefully considered and the quantum phases are systematically distinguished from thermal phases. In particular, we demonstrate stabilization of a genuine Bose glass phase against the normal fluid in sizable parameter ranges. Our results for strong interactions are interpreted using a fermionization picture and experimental relevance is discussed. (10.1103/PhysRevLett.130.220402)
  DOI : 10.1103/PhysRevLett.130.220402