Publications

2022

• Deuteron relativistic charge distributions
  
  • Lorcé Cédric
  • Wang Pierre
  Physical Review D, American Physical Society, 2022, 105 (9), pp.096032. We study the relativistic 2D charge distributions in the case of a spin-1 target. These charge distributions are based on a phase-space approach allowing one to study their frame dependence, and hence to relate the familiar rest-frame picture with the light-front picture developed in the last two decades. Like in the spin-<math display="inline"><mn>1</mn><mo>/</mo><mn>2</mn></math> case, we show that relativistic kinematical effects associated with spin are responsible for the distortions of the charge distributions seen in a moving frame. Applying our results to the deuteron, we observe a mild frame dependence compared to the nucleon case. (10.1103/PhysRevD.105.096032)
  DOI : 10.1103/PhysRevD.105.096032
• Massless Scalars and Higher-Spin BMS in Any Dimension
  
  • Bekaert Xavier
  • Oblak Blagoje
  Journal of High Energy Physics, Springer, 2022, 11, pp.022. Starting from the asymptotic kinematics of massless scalar fields near null infinity in any spacetime dimension, we build two higher-spin extensions of the Carrollian definition of the BMS group and its generalisations. The first extension exhibits conformal properties reminiscent of the singleton in Anti-de Sitter space. The second acts on the space of radiative solutions of the d'Alembert equation, i.e. on Sachs's representation of BMS, which we relate to the scalar massless Poincare representation and extend to any Carrollian manifold. The corresponding enveloping algebra is a higher-spin extension of BMS that can be interpreted as the asymptotic symmetry of a putative exotic higher-spin gravity theory around Minkowski spacetime. Along the way, we provide a pedagogical introduction to Carrollian geometry and its relation to BMS. (10.1007/JHEP11(2022)022)
  DOI : 10.1007/JHEP11(2022)022
• Random field ϕ$^{3}$ model and Parisi-Sourlas supersymmetry
  
  • Kaviraj Apratim
  • Trevisani Emilio
  Journal of High Energy Physics, Springer, 2022, 2022 (08), pp.290. We use the RG framework set up in [1] to explore the ϕ$^{3}$ theory with a random field interaction. According to the Parisi-Sourlas conjecture this theory admits a fixed point with emergent supersymmetry which is related to the pure Lee-Yang CFT in two less dimensions. We study the model using replica trick and Cardy variables in d = 8 − ϵ where the RG flow is perturbative. Allowed perturbations are singlets under the S$_{n}$ symmetry that permutes the n replicas. These are decomposed into operators with different scaling dimensions: the lowest dimensional part, ‘leader’, controls the RG flow in the IR; the other operators, ‘followers’, can be neglected. The leaders are classified into: susy-writable, susy-null and non-susy-writable according to their mixing properties. We construct low lying leaders and compute the anomalous dimensions of a number of them. We argue that there is no operator that can destabilize the SUSY RG flow in d ≤ 8. This agrees with the well known numerical result for critical exponents of Branched Polymers (which are in the same universality class as the random field ϕ$^{3}$ model) that match the ones of the pure Lee-Yang fixed point according to dimensional reduction in all 2 ≤ d ≤ 8. Hence this is a second strong check of the RG framework that was previously shown to correctly predict loss of dimensional reduction in random field Ising model. (10.1007/JHEP08(2022)290)
  DOI : 10.1007/JHEP08(2022)290
• Parisi-Sourlas Supersymmetry in Random Field Models
  
  • Kaviraj Apratim
  • Rychkov Slava
  • Trevisani Emilio
  Physical Review Letters, American Physical Society, 2022, 129 (4), pp.045701. By the Parisi-Sourlas conjecture, the critical point of a theory with random field (RF) disorder is described by a supersymmeric (SUSY) conformal field theory (CFT), related to a <math display="inline"><mi>d</mi><mo>-</mo><mn>2</mn></math> dimensional CFT without SUSY. Numerical studies indicate that this is true for the RF <math display="inline"><msup><mi>ϕ</mi><mn>3</mn></msup></math> model but not for the RF <math display="inline"><msup><mi>ϕ</mi><mn>4</mn></msup></math> model in <math display="inline"><mi>d</mi><mo>&lt;</mo><mn>5</mn></math> dimensions. Here we argue that the SUSY fixed point is not reached because of new relevant SUSY-breaking interactions. We use a perturbative renormalization group in a judiciously chosen field basis, allowing systematic exploration of the space of interactions. Our computations agree with the numerical results for both cubic and quartic potential. (10.1103/PhysRevLett.129.045701)
  DOI : 10.1103/PhysRevLett.129.045701
• Flat JT Gravity and the BMS-Schwarzian
  
  • Afshar Hamid
  • Oblak Blagoje
  Journal of High Energy Physics, Springer, 2022, 11, pp.172. We consider Minkowskian Jackiw-Teitelboim (JT) gravity in Bondi gauge at finite temperature, with non-zero vacuum energy. Its asymptotic symmetries span an extension of the warped Virasoro group, dubbed "BMS$_2$", which we investigate in detail. In particular, we show that this extension has a single coadjoint orbit when central charges are real and non-zero. The ensuing BMS-Schwarzian action has no saddle points, and only coincides with the boundary action functional of flat JT gravity up to a crucial dilatonic zero-mode that ensures the existence of a well-defined bulk variational principle. We evaluate the corresponding gravitational partition function, which turns out to be one-loop exact precisely thanks to the presence of such a zero-mode. (10.1007/JHEP11(2022)172)
  DOI : 10.1007/JHEP11(2022)172
• On the hydrodynamics of (2 + 1)-dimensional strongly coupled relativistic theories in an external magnetic field
  
  • Amoretti Andrea
  • Brattan Daniel K.
  Mod.Phys.Lett.A, 2022, 37 (21), pp.2230010. In this paper, we review recent progress on relativistic hydrodynamics in (2 + 1) dimensions with an external magnetic field. We discuss the formalism allowing for momentum loss due to the explicit and spontaneous breaking of translation invariance by scalar operators. We also compare to some results from the gauge/gravity correspondence. (10.1142/S0217732322300105)
  DOI : 10.1142/S0217732322300105
• Return-time Lq -spectrum for equilibrium states with potentials of summable variation
  
  • Abadi M
  • Amorim V
  • Chazottes J.-R
  • Gallo S
  Ergodic Theory and Dynamical Systems, Cambridge University Press (CUP), 2022, 43 (8), pp.2489-2515. Let $(X_k)_{k\geq 0}$ be a stationary and ergodic process with joint distribution $\mu$ where the random variables $X_k$ take values in a finite set $\mathcal{A}$. Let $R_n$ be the first time this process repeats its first $n$ symbols of output. It is well-known that $\frac{1}{n}\log R_n$ converges almost surely to the entropy of the process. Refined properties of $R_n$ (large deviations, multifractality, etc) are encoded in the return-time $L^q$-spectrum defined as \[ \EuScript{R}(q)=\lim_n\frac{1}{n}\log\int R_n^q \dd\mu\quad (q\in\R) \] provided the limit exists. We consider the case where $(X_k)_{k\geq 0}$ is distributed according to the equilibrium state of a potential $\varphi:\mathcal{A}^{\N}\to\R$ with summable variation, and we prove that \[ \EuScript{R}(q) = \begin{cases} P((1-q)\varphi) & \text{for}\;\; q\geq q_\varphi^*\\ \sup_\eta \int \varphi \dd\eta & \text{for}\;\; q<q_\varphi^{*} \end{cases} \] where $P((1-q)\varphi)$ is the topological pressure of $(1-q)\varphi$, the supremum is taken over all shift-invariant measures, and $q_\varphi^*$ is the unique solution of $P((1-q)\varphi) =\sup_\eta \int \varphi \dd\eta$. Unexpectedly, this spectrum does not coincide with the $L^q$-spectrum of $\mu_\varphi$, which is $P((1-q)\varphi)$, and does not coincide with the waiting-time $L^q$-spectrum in general. In fact, the return-time $L^q$-spectrum coincides with the waiting-time $L^q$-spectrum if and only if the equilibrium state of $\varphi$ is the measure of maximal entropy. As a by-product, we also improve the large deviation asymptotics of $\frac{1}{n}\log R_n$. (10.1017/etds.2022.40)
  DOI : 10.1017/etds.2022.40
• Global and local topological quantized responses from geometry, light, and time
  
  • Le Hur Karyn
  Physical Review B, American Physical Society, 2022, 105 (12), pp.125106. To describe a spin-<math><mfrac><mn>1</mn><mn>2</mn></mfrac></math> particle on the Bloch sphere with a radial magnetic field and topological states of matter from the reciprocal space, we introduce <math><mi>C</mi></math> square (<math><msup><mi>C</mi><mn>2</mn></msup></math>) as a local formulation of the global topological invariant. For the Haldane model on the honeycomb lattice, this <math><msup><mi>C</mi><mn>2</mn></msup></math> can be measured from the Dirac points through circularly polarized light related to the high-symmetry <math><mi>M</mi></math> point(s). For the quantum spin Hall effect and the Kane-Mele model, the <math><msub><mi mathvariant="double-struck">Z</mi><mn>2</mn></msub></math> topological number robust to interactions can be measured locally from a correspondence between the Pfaffian and light. We address a relation with a spin pump and the quantum spin Hall conductance. The analogy between light and magnetic nuclear resonance may be applied for imaging, among other applications. (10.1103/PhysRevB.105.125106)
  DOI : 10.1103/PhysRevB.105.125106
• Dijet photoproduction at low $x$ at next-to-leading order and its back-to-back limit
  
  • Taels Pieter
  • Altinoluk Tolga
  • Beuf Guillaume
  • Marquet Cyrille
  Journal of High Energy Physics, Springer, 2022, 10, pp.184. We compute the cross section for the inclusive photoproduction of a pair of jets at next-to-leading order accuracy in the Color Glass Condensate (CGC) effective theory. The aim is to study the back-to-back limit, to investigate whether transverse momentum dependent (TMD) factorization can be recovered at this order. In particular, we focus on the large Sudakov double logarithms, which are major ingredients of the TMD evolution. Interestingly, the kinematical improvement of the low-$x$ resummation scheme turns out to be a key ingredient in the analysis. (10.1007/JHEP10(2022)184)
  DOI : 10.1007/JHEP10(2022)184
• Gluon-mediated inclusive Deep Inelastic Scattering from Regge to Bjorken kinematics
  
  • Boussarie Renaud
  • Mehtar-Tani Yacine
  Journal of High Energy Physics, Springer, 2022, 07, pp.080. We revisit high energy factorization for gluon mediated inclusive Deep Inelastic Scattering (DIS) for which we propose a new semi-classical approach that accounts systematically for the longitudinal extent of the target in contrast with the shockwave limit. In this framework, based on a partial twist expansion, we derive a factorization formula that involves a new gauge invariant unintegrated gluon distribution which depends explicitly on the Feynman x variable. It is shown that both the Regge and Bjorken limits are recovered in this approach. We reproduce in particular the full one loop inclusive DIS cross-section in the leading twist approximation and the all-twist dipole factorization formula in the strict x = 0 limit. Although quantum evolution is not discussed explicitly in this work, we argue that the proper treatment of the x dependence of the gluon distribution encompasses the kinematic constraint that must be imposed on the phase-space of gluon fluctuations in the target to ensure stability of small-x evolution. (10.1007/JHEP07(2022)080)
  DOI : 10.1007/JHEP07(2022)080
• Rigorous bounds on irrelevant operators in the 3d Ising model CFT
  
  • Reehorst Marten
  Journal of High Energy Physics, Springer, 2022, 09, pp.177. We use the recently developed navigator method to obtain rigorous upper and lower bounds on new OPE data in the 3d Ising CFT. For example, assuming that there are only two ℤ$_{2}$-even scalar operators ϵ and ϵ′ with a dimension below 6 we find a narrow allowed interval for ∆$_{ϵ′}$, λ$_{σσϵ′}$ and λ$_{ϵϵϵ′}$. With similar assumptions in the ℤ$_{2}$-even spin-2 and the ℤ$_{2}$-odd scalar sectors we are also able to constrain: the central charge c$_{T}$; the OPE data ∆$_{T′}$, λ$_{ϵϵT′}$ and λ$_{σσT′}$ of the second spin-2 operator; and the OPE data ∆$_{σ′}$ and λ$_{σϵσ′}$ of the second ℤ$_{2}$-odd scalar. We compare the rigorous bounds we find with estimates that have been previously obtained using the extremal functional method (EFM) and find a good match. This both validates the EFM and shows the navigator-search method to be a feasible and more rigorous alternative for estimating a large part of the low-dimensional operator spectrum. We also investigate the effect of imposing sparseness conditions on all sectors at once. We find that the island does not greatly reduce in size under these assumptions. We efficiently find islands and determine their size in high-dimensional parameter spaces (up to 13 parameters). This shows that using the navigator method the numerical conformal bootstrap is no longer constrained to the exploration of small parameter spaces. (10.1007/JHEP09(2022)177)
  DOI : 10.1007/JHEP09(2022)177
• Gauge invariant operators in the SU(2) Higgs model: Ward identities and renormalization
  
  • Dudal David
  • van Egmond Duifje Maria
  • Justo Igor Figueiredo
  • Peruzzo Giovani
  • Sorella Silvio Paolo
  Physical Review D, American Physical Society, 2022, 105 (6), pp.065018. The renormalization properties of two local gauge invariant composite operators <math display="inline"><mo stretchy="false">(</mo><mi>O</mi><mo>,</mo><msubsup><mi>R</mi><mi>μ</mi><mi>a</mi></msubsup><mo stretchy="false">)</mo></math> corresponding, respectively, to the gauge invariant description of the Higgs particle and of the massive gauge vector boson, are analyzed to all orders in perturbation theory by means of the algebraic renormalization in the <math display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math> Higgs model, with a single scalar in the fundamental representation, when quantized in the Landau gauge in Euclidean space-time. The present analysis generalizes earlier results presented in the case of the <math display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math> Higgs model. A powerful global Ward identity, related to an exact custodial symmetry, is derived for the first time, with deep consequences at the quantum level. In particular, the gauge invariant vector operators <math display="inline"><msubsup><mi>R</mi><mi>μ</mi><mi>a</mi></msubsup></math> turn out to be the conserved Noether currents of the above-mentioned custodial symmetry. As such, these composite operators do not renormalize, as expressed by the fact that the renormalization <math display="inline"><mi>Z</mi></math>-factors of the corresponding external sources, needed to define the operators <math display="inline"><msubsup><mi>R</mi><mi>μ</mi><mi>a</mi></msubsup></math> at the quantum level, do not receive any quantum corrections. Using this Ward identity, one can also prove that the longitudinal component of the two-point correlation function <math display="inline"><mo stretchy="false">⟨</mo><msubsup><mi>R</mi><mi>μ</mi><mi>a</mi></msubsup><mo stretchy="false">(</mo><mi>p</mi><mo stretchy="false">)</mo><msubsup><mi>R</mi><mi>ν</mi><mi>b</mi></msubsup><mo stretchy="false">(</mo><mo>-</mo><mi>p</mi><mo stretchy="false">)</mo><mo stretchy="false">⟩</mo></math> exhibits only a tree level nonvanishing contribution which, moreover, is momentum independent, thus it is not associated to any physical propagating mode. Finally, we point out that the renowned nonrenormalization theorem for the ghost-antighost-vector boson vertex in Landau gauge remains true to all orders, also in the presence of the Higgs field. (10.1103/PhysRevD.105.065018)
  DOI : 10.1103/PhysRevD.105.065018
• Dynamics of the $O(4)$ critical point in QCD
  
  • Florio Adrien
  • Grossi Eduardo
  • Soloviev Alexander
  • Teaney Derek
  Physical Review D, American Physical Society, 2022, 105 (5), pp.054512. We perform a Langevin simulation of the <math display="inline"><mi>O</mi><mo stretchy="false">(</mo><mn>4</mn><mo stretchy="false">)</mo></math> critical point, which lies in the dynamic universality class of “model G.” This is the dynamic universality class of the chiral phase transition in QCD with two massless flavors. The axial charge and the order parameter <math display="inline"><msub><mi>ϕ</mi><mi>a</mi></msub><mo>=</mo><mo stretchy="false">(</mo><mi>σ</mi><mo>,</mo><mover accent="true"><mi>π</mi><mo stretchy="false">→</mo></mover><mo stretchy="false">)</mo></math> exhibit a rich dynamical interplay, which reflects the qualitative differences in the hydrodynamic effective theories above and below <math display="inline"><msub><mi>T</mi><mi>c</mi></msub></math>. From the axial charge correlators on the critical line we extract a dynamical critical exponent of <math display="inline"><mrow><mi>ζ</mi><mo>=</mo><mn>1.47</mn><mo>±</mo><mn>0.01</mn><mo stretchy="false">(</mo><mtext>stat.</mtext><mo stretchy="false">)</mo></mrow></math>, which is compatible with the theoretical expectation of <math display="inline"><mi>ζ</mi><mo>=</mo><mi>d</mi><mo>/</mo><mn>2</mn></math> (with <math display="inline"><mi>d</mi><mo>=</mo><mn>3</mn></math>) when systematic errors are taken into account. At low temperatures, we quantitatively match the <math display="inline"><mi>O</mi><mo stretchy="false">(</mo><mn>4</mn><mo stretchy="false">)</mo></math> simulations to the superfluid effective theory of soft pions. (10.1103/PhysRevD.105.054512)
  DOI : 10.1103/PhysRevD.105.054512
• Multiple scaling limits of $\operatorname{U}(N)^2 \times \operatorname{O}(D)$ multi-matrix models
  
  • Benedetti Dario
  • Carrozza Sylvain
  • Toriumi Reiko
  • Valette Guillaume
  Ann.Inst.H.Poincare D Comb.Phys.Interact., 2022, 9 (2), pp.367-433. We study the double- and triple-scaling limits of a complex multi-matrix model, with U(N)2×O(D)\mathrm{U}(N)^2\times \mathrm{O}(D)U(N)2×O(D) symmetry. The double-scaling limit amounts to taking simultaneously the large-NNN (matrix size) and large-DDD (number of matrices) limits while keeping the ratio N/D=MN/\sqrt{D}=MN/D​=M fixed. The triple-scaling limit consists in taking the large-MMM limit while tuning the coupling constant λ\lambdaλ to its critical value λc\lambda_cλc​ and keeping fixed the product M(λc−λ)αM(\lambda_c-\lambda)^\alphaM(λc​−λ)α, for some value of α\alphaα that depends on the particular combinatorial restrictions imposed on the model. Our first main result is the complete recursive characterization of the Feynman graphs of arbitrary genus which survive in the double-scaling limit. Next, we classify all the dominant graphs in the triple-scaling limit, which we find to have a plane binary tree structure with decorations. Their critical behavior belongs to the universality class of branched polymers. Lastly, we classify all the dominant graphs in the triple-scaling limit under the restriction to three-edge connected (or two-particle irreducible) graphs. Their critical behavior falls in the universality class of Liouville quantum gravity (or, in other words, the Brownian sphere). (10.4171/aihpd/121)
  DOI : 10.4171/aihpd/121
• Prospects for quarkonium studies at the high-luminosity LHC
  
  • Chapon Emilien
  • d'Enterria David
  • Ducloue Bertrand
  • Echevarria Miguel G.
  • Gossiaux Pol-Bernard
  • Kartvelishvili Vato
  • Kasemets Tomas
  • Lansberg Jean-Philippe
  • Mcnulty Ronan
  • Price Darren D.
  • Shao Hua-Sheng
  • van Hulse Charlotte
  • Winn Michael
  • Adam Jaroslav
  • An Liupan
  • Villar Denys Yen Arrebato
  • Bhattacharya Shohini
  • Celiberto Francesco G.
  • Cheshkov Cvetan
  • d'Alesio Umberto
  • da Silva Cesar
  • Ferreiro Elena G.
  • Flett Chris A.
  • Flore Carlo
  • Garzelli Maria Vittoria
  • Gaunt Jonathan
  • He Jibo
  • Makris Yiannis
  • Marquet Cyrille
  • Massacrier Laure
  • Mehen Thomas
  • Mezrag Cedric
  • Micheletti Luca
  • Nagar Riccardo
  • Nefedov Maxim A.
  • Ozcelik Melih A.
  • Paul Biswarup
  • Pisano Cristian
  • Qiu Jian-Wei
  • Rajesh Sangem
  • Rinaldi Matteo
  • Scarpa Florent
  • Smith Maddie
  • Taels Pieter
  • Tee Amy
  • Teryaev Oleg
  • Vitev Ivan
  • Watanabe Kazuhiro
  • Yamanaka Nodoka
  • Yao Xiaojun
  • Zhang Yanxi
  Prog.Part.Nucl.Phys., 2022, 122, pp.103906. Prospects for quarkonium-production studies accessible during the upcoming high-luminosity phases of the CERN Large Hadron Collider operation after 2021 are reviewed. Current experimental and theoretical open issues in the field are assessed together with the potential for future studies in quarkonium-related physics. This will be possible through the exploitation of the huge data samples to be collected in proton–proton, proton–nucleus and nucleus–nucleus collisions, both in the collider and fixed-target modes. Such investigations include, among others, those of: (i) <math display="inline" id="d1e8603" altimg="si149.svg"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> and <math display="inline" id="d1e8613" altimg="si276.svg"><mi>Υ</mi></math> produced in association with other hard particles; (ii) <math display="inline" id="d1e8618" altimg="si3.svg"><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi><mo>,</mo><mi>b</mi></mrow></msub></math> and <math display="inline" id="d1e8633" altimg="si4.svg"><msub><mrow><mi>η</mi></mrow><mrow><mi>c</mi><mo>,</mo><mi>b</mi></mrow></msub></math> down to small transverse momenta; (iii) the constraints brought in by quarkonia on gluon PDFs, nuclear PDFs, TMDs, GPDs and GTMDs, as well as on the low-<math display="inline" id="d1e8647" altimg="si5.svg"><mi>x</mi></math> parton dynamics; (iv) the gluon Sivers effect in polarised-nucleon collisions; (v) the properties of the quark–gluon plasma produced in ultra-relativistic heavy-ion collisions and of collective partonic effects in general; and (vi) double and triple parton scatterings. (10.1016/j.ppnp.2021.103906)
  DOI : 10.1016/j.ppnp.2021.103906
• Rings and strings: a basis for understanding subleading colour and QCD coherence beyond the two-jet limit
  
  • Forshaw Jeffrey R.
  • Holguin Jack
  • Plätzer Simon
  Journal of High Energy Physics, Springer, 2022, 05, pp.190. Guided by the colour-diagonal structure of collinear singularities, we identify a set of kinematic basis functions that are well suited to the simplification of soft gluon emission amplitudes. In particular, these basis functions, which emerge naturally in the colour flow basis, isolate the subleading colour contributions and improve the statistical convergence of the CVolver amplitude-evolution code. They also allow us to extend current angular-ordered parton showers beyond the azimuthally-averaged, two-jet limit. (10.1007/JHEP05(2022)190)
  DOI : 10.1007/JHEP05(2022)190
• The SAGEX Review on Scattering Amplitudes
  
  • Travaglini Gabriele
  • Brandhuber Andreas
  • Dorey Patrick
  • Mcloughlin Tristan
  • Abreu Samuel
  • Bern Zvi
  • Bjerrum-Bohr N. Emil J.
  • Blümlein Johannes
  • Britto Ruth
  • Carrasco John Joseph M.
  • Chicherin Dmitry
  • Chiodaroli Marco
  • Damgaard Poul H.
  • del Duca Vittorio
  • Dixon Lance J.
  • Dorigoni Daniele
  • Duhr Claude
  • Geyer Yvonne
  • Green Michael B.
  • Herrmann Enrico
  • Heslop Paul
  • Johansson Henrik
  • Korchemsky Gregory P.
  • Kosower David A.
  • Mason Lionel
  • Monteiro Ricardo
  • O'Connell Donal
  • Papathanasiou Georgios
  • Plante Ludovic
  • Plefka Jan
  • Puhm Andrea
  • Raclariu Ana-Maria
  • Roiban Radu
  • Schneider Carsten
  • Trnka Jaroslav
  • Vanhove Pierre
  • Wen Congkao
  • White Chris D.
  Journal of Physics A: Mathematical and Theoretical, IOP Publishing, 2022, 55 (44), pp.443001. This is an introduction to, and invitation to read, a series of review articles on scattering amplitudes in gauge theory, gravity, and superstring theory. Our aim is to provide an overview of the field, from basic aspects to a selection of current (2022) research and developments. (10.1088/1751-8121/ac8380)
  DOI : 10.1088/1751-8121/ac8380
• Frequency chirp effects on stimulated Raman scattering in inhomogeneous plasmas
  
  • Luo Mufei
  • Hüller Stefan
  • Chen Min
  • Sheng Zhengming
  Physics of Plasmas, American Institute of Physics, 2022, 29, pp.072709. Previous studies have shown that the use of laser bandwidth may mitigate the growth of stimulated Raman scattering (SRS) in laser plasma interaction experiments, in particular when the spectrum of the driving (or pump) laser is composed of uniformly distributed frequency components with a well-chosen bandwidth [for example, M. Luo et al, Phys. Plasmas 29, 032102 (2022); H. Wen et al, Phys. Plasmas 28, 042109 (2021); R. K. Follett et al, Phys. Plasmas 26, 062111 (2019)]. Here, we investigate the effects of frequency chirp in the pump laser on backward SRS in inhomogeneous plasmas, taking into account kinetic effects associated with the nonlinear detuning of the parametric resonance due to high-amplitude electron plasma waves (EPW). Via theoretical considerations and numerical simulations, using a multi-dimensional particle-in-cell (PIC) code, it is shown that positive frequency chirp rates lead to a displacement of the resonance in the plasma profile. For a sufficiently strong positive chirp rate, such that the resonance displacement is faster than the EPW group velocity, the EPWs prove to remain limited in amplitude such that SRS is suppressed. The required frequency chirp rate corresponds to a laser bandwidth of about 1-2%. (10.1063/5.0096771)
  DOI : 10.1063/5.0096771
• Event Generators for High-Energy Physics Experiments
  
  • Campbell J. M.
  • Diefenthaler M.
  • Hobbs T. J.
  • Höche S.
  • Isaacson J.
  • Kling F.
  • Mrenna S.
  • Reuter J.
  • Alioli S.
  • Andersen J. R.
  • Andreopoulos C.
  • Ankowski A. M.
  • Aschenauer E. C.
  • Ashkenazi A.
  • Baker M. D.
  • Barrow J. L.
  • van Beekveld M.
  • Bewick G.
  • Bhattacharya S.
  • Bierlich C.
  • Bothmann E.
  • Bredt P.
  • Broggio A.
  • Buckley A.
  • Butter A.
  • Butterworth J. M.
  • Byrne E. P.
  • Calame C. M. Carloni
  • Chakraborty S.
  • Chen X.
  • Chiesa M.
  • Childers J. T.
  • Cruz-Martinez J.
  • Currie J.
  • Darvishi N.
  • Dasgupta M.
  • Denner A.
  • Dreyer F. A.
  • Dytman S.
  • El-Menoufi B. K.
  • Engel T.
  • Ravasio S. Ferrario
  • Figueroa D.
  • Flower L.
  • Forshaw J. R.
  • Frederix R.
  • Friedland A.
  • Frixione S.
  • Gallagher H.
  • Gallmeister K.
  • Gardiner S.
  • Gauld R.
  • Gaunt J.
  • Gavardi A.
  • Gehrmann T.
  • Ridder A. Gehrmann-De
  • Gellersen L.
  • Giele W.
  • Gieseke S.
  • Giuli F.
  • Glover E. W. N.
  • Grazzini M.
  • Grohsjean A.
  • Gütschow C.
  • Hamilton K.
  • Han T.
  • Hatcher R.
  • Heinrich G.
  • Helenius I.
  • Hen O.
  • Hirschi V.
  • Höfer M.
  • Holguin J.
  • Huss A.
  • Ilten P.
  • Jadach S.
  • Jentsch A.
  • Jones S. P.
  • Ju W.
  • Kallweit S.
  • Karlberg A.
  • Katori T.
  • Kerner M.
  • Kilian W.
  • Kirchgaeßer M. M.
  • Klein S.
  • Knobbe M.
  • Krause C.
  • Krauss F.
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  , 2022. We provide an overview of the status of Monte-Carlo event generators for high-energy particle physics. Guided by the experimental needs and requirements, we highlight areas of active development, and opportunities for future improvements. Particular emphasis is given to physics models and algorithms that are employed across a variety of experiments. These common themes in event generator development lead to a more comprehensive understanding of physics at the highest energies and intensities, and allow models to be tested against a wealth of data that have been accumulated over the past decades. A cohesive approach to event generator development will allow these models to be further improved and systematic uncertainties to be reduced, directly contributing to future experimental success. Event generators are part of a much larger ecosystem of computational tools. They typically involve a number of unknown model parameters that must be tuned to experimental data, while maintaining the integrity of the underlying physics models. Making both these data, and the analyses with which they have been obtained accessible to future users is an essential aspect of open science and data preservation. It ensures the consistency of physics models across a variety of experiments.
• Damping of Pseudo-Goldstone Fields
  
  • Delacrétaz Luca V.
  • Goutéraux Blaise
  • Ziogas Vaios
  Physical Review Letters, American Physical Society, 2022, 128 (14), pp.141601. Approximate symmetries abound in nature. If these symmetries are also spontaneously broken, the would-be Goldstone modes acquire a small mass, or inverse correlation length, and are referred to as pseudo-Goldstones. At nonzero temperature, the effects of dissipation can be captured by hydrodynamics at sufficiently long scales compared to the local equilibrium. Here, we show that, in the limit of weak explicit breaking, locality of hydrodynamics implies that the damping of pseudo-Goldstones is completely determined by their mass and diffusive transport coefficients. We present many applications: superfluids, QCD in the chiral limit, Wigner crystal and density wave phases in the presence of an external magnetic field or not, nematic phases, and (anti)ferromagnets. For electronic density wave phases, pseudo-Goldstone damping generates a contribution to the resistivity independent of the strength of disorder, which can have a linear temperature dependence provided the associated diffusivity saturates a bound. This is reminiscent of the phenomenology of strange metal high-<math display="inline"><msub><mi>T</mi><mi>c</mi></msub></math> superconductors, where charge density waves are observed across the phase diagram. (10.1103/PhysRevLett.128.141601)
  DOI : 10.1103/PhysRevLett.128.141601
• Gaussian concentration bounds for stochastic chains of unbounded memory
  
  • Chazottes Jean-Rene
  • Gallo Sandro
  • Takahashi Daniel
  The Annals of Applied Probability, Institute of Mathematical Statistics (IMS), 2022. We obtain optimal Gaussian concentration bounds (GCBs) for stochastic chains of unbounded memory (SCUMs) on countable alphabets. These stochastic processes are also known as ``chains with complete connections'' or ``$g$-measures''. We consider two different conditions on the kernel: (1) when the sum of its oscillations is less than one, or (2) when the sum of its variations is finite, {\em i.e.}, belongs to $\ell^1(\mathbb{N})$. We also obtain explicit constants as functions of the parameters of the model. The proof is based on maximal coupling. Our conditions are optimal in the sense that we exhibit examples of SCUMs that do not have GCB and for which the sum of oscillations is strictly larger than one, or the variation belongs to $\ell^{1+\epsilon}(\mathbb{N})$ for any $\epsilon > 0$. These examples are based on the existence of phase transitions. We also extend the validity of GCB to a class of functions which can depend on infinitely many coordinates. We illustrate our results by three applications. First, we derive a Dvoretzky-Kiefer-Wolfowitz type inequality which gives a uniform control on the fluctuations of the empirical measure. Second, in the finite-alphabet case, we obtain an upper bound on the $\bar{d}$-distance between two stationary SCUMs and, as a by-product, we obtain new (explicit) bounds on the speed of Markovian approximation in $\bar{d}$. Third, we obtain exponential rate of convergence for Birkhoff sums of a certain class of observables.
• Bootstrapping boundary-localized interactions II. Minimal models at the boundary
  
  • Behan Connor
  • Di Pietro Lorenzo
  • Lauria Edoardo
  • van Rees Balt C.
  Journal of High Energy Physics, Springer, 2022, 2022 (03), pp.146. We provide evidence for the existence of non-trivial unitary conformal boundary conditions for a three-dimensional free scalar field, which can be obtained via a coupling to the m’th unitary diagonal minimal model. For large m we can demonstrate the existence of the fixed point perturbatively, and for smaller values we use the numerical conformal bootstrap to obtain a sharp kink that smoothly matches onto the perturbative predictions. The wider numerical analysis also yields universal bounds for the spectrum of any other boundary condition for the free scalar field. A second kink in these bounds hints at a second class of non-standard boundary conditions, as yet unidentified. (10.1007/JHEP03(2022)146)
  DOI : 10.1007/JHEP03(2022)146
• Hubbard model on the kagome lattice with time-reversal invariant flux and spin-orbit coupling
  
  • Titvinidze Irakli
  • Legendre Julian
  • Le Hur Karyn
  • Hofstetter Walter
  Physical Review B, American Physical Society, 2022, 105 (23), pp.235102. We study the Hubbard model with time-reversal-invariant flux and spin-orbit coupling and position-dependent onsite energies on the kagome lattice, using numerical and analytical methods. In particular, we perform calculations using real-space dynamical mean-field theory (R-DMFT). To study the topological properties of the system, we use the topological Hamiltonian approach. We obtain a rich phase diagram: For weak and intermediate interactions, depending on the model parameters, the system is in the band insulator, topological insulator, or metallic phase, while for strong interactions the system is in the Mott insulator phase. We also investigate the magnetic phases that occur in this system. For this purpose, in addition to R-DMFT, we also use two analytical methods: perturbation theory for large interactions and onsite energies and stochastic mean-field theory. (10.1103/PhysRevB.105.235102)
  DOI : 10.1103/PhysRevB.105.235102
• Symmetry-Resolved Study of Lattice Vibration and Libration Modes in [Fe(phen)2(NCS)2] Crystal
  
  • Privault Gaël
  • Mevellec Jean-Yves
  • Lorenc Maciej
  • Humbert Bernard
  • Janod Etienne
  • Daro Nathalie
  • Chastanet Guillaume
  • Subedi Alaska
  • Collet Eric
  Crystal Growth & Design, American Chemical Society, 2022, 22 (8), pp.5100-5109. In the family of spin-crossover materials, which undergo thermal conversion between low-spin (LS) and high-spin (HS) phases, it is of great interest to study vibrational modes. On the one hand, vibration modes are characteristic of the spin state, and vibrational spectroscopies are often used for monitoring spin-state switching driven by temperature, pressure, or light. On the other hand, spin-state thermal conversion is an entropy-driven process, and the vibrational entropy change represents the main contribution to the total entropy difference between LS and HS phases at solid state. However, the discussion of vibrations in spin-crossover materials is often limited at the molecular scale. Here we study vibration modes in the [Fe(phen)(2)(NCS)(2)] crystal, and we compare symmetry-resolved vibrational spectroscopy data performed on single crystal to density functional theory calculations performed in a periodic three-dimensional crystal. We discuss the complex nature of vibrational modes in crystals, including the vibration of molecules within the crystalline lattice, with different symmetries and frequencies. We also highlight the presence of many low-frequency libration modes of different symmetries. The contribution of vibrational entropy, added to the electronic entropy, provides a total entropy difference in the solid state, which is in very good agreement with calorimetric measurements. (10.1021/acs.cgd.2c00659)
  DOI : 10.1021/acs.cgd.2c00659
• Entanglement spectrum and quantum phase diagram of the long-range XXZ chain
  
  • Schneider J.T.
  • Thomson S.J.
  • Sanchez-Palencia L.
  Physical Review B, American Physical Society, 2022, 106 (1), pp.014306. Entanglement is a central feature of many-body quantum systems and plays a unique role in quantum phase transitions. In many cases, the entanglement spectrum, which represents the spectrum of the density matrix of a bipartite system, contains valuable information beyond the sole entanglement entropy. Here we investigate the entanglement spectrum of the long-range XXZ model. We show that within the critical phase it exhibits a remarkable self-similarity. The breakdown of self-similarity and the transition away from a Luttinger liquid is consistent with renormalization group theory. Combining the two, we are able to determine the quantum phase diagram of the model and locate the corresponding phase transitions. Our results are confirmed by numerically-exact calculations using tensor-network techniques. Moreover, we show that the self-similar rescaling extends to the geometrical entanglement as well as the Luttinger parameter in the critical phase. Our results pave the way to further studies of entanglement properties in long-range quantum models. (10.1103/PhysRevB.106.014306)
  DOI : 10.1103/PhysRevB.106.014306