Publications

2021

Potential linear and angular momentum in the scalar diquark model
- Amor-Quiroz David Arturo
- Burkardt Matthias
- Focillon William
- Lorcé Cédric
European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2021, 81 (7), pp.589. We present an analytic two-loop calculation within the scalar diquark model of the potential linear and angular momenta, defined as the difference between the Jaffe-Manohar and Ji notions of linear and angular momenta. As expected by parity and time-reversal symmetries, a direct calculation confirms that the potential transverse momentum coincides with the Jaffe-Manohar (or canonical) definition of average quark transverse momentum, also known as the quark Sivers shift. We examine whether initial/final-state interactions at the origin of the Sivers asymmetry can also generate a potential angular momentum in the scalar diquark model. (10.1140/epjc/s10052-021-09345-9)
DOI : 10.1140/epjc/s10052-021-09345-9
Analytical asymptotics for hard diffraction
- Le Anh Dung
- Mueller Alfred H.
- Munier Stéphane
Physical Review D, American Physical Society, 2021, 104, pp.034026. We show that the cross section for diffractive dissociation of a small onium off a large nucleus at total rapidity $Y$ and requiring a minimum rapidity gap $Y_{\text{gap}}$ can be identified, in a well-defined parametric limit, with a simple classical observable on the stochastic process representing the evolution of the state of the onium, as its rapidity increases, in the form of color dipole branchings: It formally coincides with twice the probability that an even number of these dipoles effectively participate in the scattering, when viewed in a frame in which the onium is evolved to the rapidity $Y-Y_{\text{gap}}$. Consequently, finding asymptotic solutions to the Kovchegov-Levin equation, which rules the $Y$-dependence of the diffractive cross section, boils down to solving a probabilistic problem. Such a formulation authorizes the derivation of a parameter-free analytical expression for the gap distribution. Interestingly enough, events in which many dipoles interact simultaneously play an important role, since the distribution of the number $k$ of dipoles participating in the interaction turns out to be proportional to $1/[k(k-1)]$. (10.1103/PhysRevD.104.034026)
DOI : 10.1103/PhysRevD.104.034026
Quantum Phase Transition at Nonzero Doping in a Random $t-J$ Model
- Shackleton Henry
- Wietek Alexander
- Georges Antoine
- Sachdev Subir
Physical Review Letters, American Physical Society, 2021, 126 (13), pp.136602. We present exact diagonalization results on finite clusters of a t-J model of spin-1/2 electrons with random all-to-all hopping and exchange interactions. We argue that such random models capture qualitatively the strong local correlations needed to describe the cuprates and related compounds, while avoiding lattice space group symmetry breaking orders. The previously known spin glass ordered phase in the insulator at doping p=0 extends to a metallic spin glass phase up to a transition p=pc≈1/3. The dynamic spin susceptibility shows signatures of the spectrum of the Sachdev-Ye-Kitaev models near pc. We also find signs of the phase transition in the entropy, entanglement entropy, and compressibility, all of which exhibit a maximum near pc. The electron energy distribution function in the metallic phase is consistent with a disordered extension of the Luttinger-volume Fermi surface for p>pc, while this breaks down for p<pc. (10.1103/PhysRevLett.126.136602)
DOI : 10.1103/PhysRevLett.126.136602
Navigator Function for the Conformal Bootstrap
- Reehorst Marten
- Rychkov Slava
- Simmons-Duffin David
- Sirois Benoit
- Su Ning
- van Rees Balt
SciPost Physics, SciPost Foundation, 2021, 11 (3), pp.072. Current numerical conformal bootstrap techniques carve out islands in theory space by repeatedly checking whether points are allowed or excluded. We propose a new method for searching theory space that replaces the binary information "allowed"/"excluded" with a continuous "navigator" function that is negative in the allowed region and positive in the excluded region. Such a navigator function allows one to efficiently explore high-dimensional parameter spaces and smoothly sail towards any islands they may contain. The specific functions we introduce have several attractive features: they are everywhere well-defined, can be computed with standard methods, and evaluation of their gradient is immediate due to an SDP gradient formula that we provide. The latter property allows for the use of efficient quasi-Newton optimization methods, which we illustrate by navigating towards the 3d Ising island. (10.21468/SciPostPhys.11.3.072)
DOI : 10.21468/SciPostPhys.11.3.072
A modified in-medium evolution equation with color coherence
- Barata João
- Domínguez Fabio
- Salgado Carlos A.
- Vila Víctor
Journal of High Energy Physics, Springer, 2021, 05, pp.148. QCD jets produced in heavy-ion collisions at LHC or RHIC energies partially evolve inside the produced hot and dense quark gluon plasma, offering unique opportunities to study QCD splitting processes in different backgrounds. Induced (modified) splittings are expected to be the most relevant mechanism driving the modifications of in-medium jets compared to vacuum jets for a wide sets of observables. Although color coherence among different emitters has been identified as an essential mechanism in studies of the QCD antenna radiation, it is usually neglected in the multi-gluon medium-induced cascade. This independent gluon emission approximation can be analytically proved to be valid in the limit of very large media, but corrections or modifications to it have not been computed before in the context of the evolution (or rate) equation describing the gluon cascade. We propose a modified evolution equation that includes corrections due to the interference of subsequent emitters. In order to do so, we first compute a modified splitting kernel following the usual procedure of factorizing it from the subsequent Brownian motion. The calculation is performed in the two-gluon configuration with no overlapping formation times, that is expected to provide the first correction to the completely independent picture. (10.1007/JHEP05(2021)148)
DOI : 10.1007/JHEP05(2021)148
Phase transition at high supersymmetry breaking scale in heterotic string theory
- Partouche Hervé
- de Vaulchier Balthazar
International Journal of Modern Physics A, World Scientific Publishing, 2021, 36 (25), pp.2141001. When supersymmetry is spontaneously broken at the tree level, the spectrum of the heterotic string compactified on orbifolds of tori contains an infinite number of potentially tachyonic modes. We show that this implies instabilities of Minkowski space–time, when the scale of supersymmetry breaking is of the order of the string scale. We derive the phase space structure of vacua in the case where the tachyonic spectrum contains a mode with trivial momenta and winding numbers along the internal directions not involved in the supersymmetry breaking. (10.1142/S0217751X21410013)
DOI : 10.1142/S0217751X21410013
Jackiw-Teitelboim quantum gravity with defects and the Aharonov-Bohm effect
- Mefford Eric
- Suzuki Kenta
Journal of High Energy Physics, Springer, 2021, 05, pp.026. We study the theory of Jackiw-Teitelboim gravity with generalized dilaton potential on Euclidean two-dimensional negatively curved backgrounds. The effect of the generalized dilaton potential is to induce a conical defect on the two-dimensional manifold. We show that this theory can be written as the ordinary quantum mechanics of a charged particle on a hyperbolic disk in the presence of a constant background magnetic field plus a pure gauge Aharonov-Bohm field. This picture allows us to exactly calculate the wavefunctions and propagators of the corresponding gravitational dynamics. With this method we are able to reproduce the gravitational density of states as well as compute the Réyni and entanglement entropies for the Hartle-Hawking state. While we reproduce the classical entropy at high temperature, we also find an extra topological contribution that becomes dominant at low temperatures. We then show how the presence of defects modify correlation functions, including the out-of-time-ordered correlation, and decrease the Lyapunov exponent. This is achieved two ways: by directly quantizing the boundary Schwarzian theory and by dimensionally reducing SL(2, ℤ) black holes. (10.1007/JHEP05(2021)026)
DOI : 10.1007/JHEP05(2021)026
Induced Einstein gravity from infinite towers of states
- Kehagias Alex
- Partouche Hervé
- de Vaulchier Balthazar
Nuclear Physics B, North-Holland ; Elsevier [1967-....], 2021, 964, pp.115312. We consider four-dimensional quadratic gravity coupled to infinite towers of free massive scalar fields, Weyl fermions and vector bosons. We find that for specific numbers of towers, finite cosmological and Newton constants are induced in the 1-loop effective action. This is derived both in Adler's approach and by using the heat kernel method, which yield identical results. If the infinite number of massive states may be regarded as Kaluza–Klein modes arising from fields in higher dimensions, there are no Kaluza–Klein states associated with the four-dimensional graviton. Hence gravity is intrinsically four-dimensional. (10.1016/j.nuclphysb.2021.115312)
DOI : 10.1016/j.nuclphysb.2021.115312
Conformally soft fermions
- Pano Yorgo
- Pasterski Sabrina
- Puhm Andrea
Journal of High Energy Physics, Springer, 2021, 12, pp.166. Celestial diamonds encode the global conformal multiplets of the conformally soft sector, elucidating the role of soft theorems, symmetry generators and Goldstone modes. Upon adding supersymmetry they stack into a pyramid. Here we treat the soft charges associated to the fermionic layers that tie this structure together. This extends the analysis of conformally soft currents for photons and gravitons which have been shown to generate asymptotic symmetries in gauge theory and gravity to infinite-dimensional fermionic symmetries. We construct fermionic charge operators in 2D celestial CFT from a suitable inner product between 4D bulk field operators and spin s = $ \frac{1}{2} $ and $ \frac{3}{2} $ conformal primary wavefunctions with definite SL(2, ℂ) conformal dimension ∆ and spin J where |J| ≤ s. The generator for large supersymmetry transformations is identified as the conformally soft gravitino primary operator with ∆ = $ \frac{1}{2} $ and its shadow with ∆ = $ \frac{3}{2} $ which form the left and right corners of the celestial gravitino diamond. We continue this analysis to the subleading soft gravitino and soft photino which are captured by degenerate celestial diamonds. Despite the absence of a gauge symmetry in these cases, they give rise to conformally soft factorization theorems in celestial amplitudes and complete the celestial pyramid. (10.1007/JHEP12(2021)166)
DOI : 10.1007/JHEP12(2021)166
A fixed-target programme at the LHC: Physics case and projected performances for heavy-ion, hadron, spin and astroparticle studies
- Hadjidakis C.
- Kikoła D.
- Lansberg J.P.
- Massacrier L.
- Echevarria M.G.
- Kusina A.
- Schienbein I.
- Seixas J.
- Shao H.S.
- Signori A.
- Trzeciak B.
- Brodsky S.J.
- Cavoto G.
- da Silva C.
- Donato F.
- Ferreiro E.G.
- Hřivnáčová I.
- Klein A.
- Kurepin A.
- Lorcé C.
- Lyonnet F.
- Makdisi Y.
- Porteboeuf Houssais S.
- Quintans C.
- Rakotozafindrabe A.
- Robbe P.
- Scandale W.
- Topilskaya N.
- Uras A.
- Wagner J.
- Yamanaka N.
- Yang Z.
- Zelenski A.
Phys.Rept., 2021, 911, pp.1-83. We review the context, the motivations and the expected performances of a comprehensive and ambitious fixed-target programme using the multi-TeV proton and ion LHC beams. We also provide a detailed account of the different possible technical implementations ranging from an internal wire target to a full dedicated beam line extracted with a bent crystal. The possibilities offered by the use of the ALICE and LHCb detectors in the fixed-target mode are also reviewed. (10.1016/j.physrep.2021.01.002)
DOI : 10.1016/j.physrep.2021.01.002
A window on infrared QCD with small expansion parameters
- Peláez Marcela
- Reinosa Urko
- Serreau Julien
- Tissier Matthieu
- Wschebor Nicolás
Reports on Progress in Physics, IOP Publishing, 2021, 84 (12), pp.124202. Lattice simulations of the QCD correlation functions in the Landau gauge have established two remarkable facts. First, the coupling constant in the gauge sector—defined, e.g., in the Taylor scheme—remains finite and moderate at all scales, suggesting that some kind of perturbative description should be valid down to infrared momenta. Second, the gluon propagator reaches a finite nonzero value at vanishing momentum, corresponding to a gluon screening mass. We review recent studies which aim at describing the long-distance properties of Landau gauge QCD by means of the perturbative Curci–Ferrari model. The latter is the simplest deformation of the Faddeev–Popov Lagrangian in the Landau gauge that includes a gluon screening mass at tree-level. There are, by now, strong evidences that this approach successfully describes many aspects of the infrared QCD dynamics. In particular, several correlation functions were computed at one- and two-loop orders and compared with ab-initio lattice simulations. The typical error is of the order of ten percent for a one-loop calculation and drops to few percents at two loops. We review such calculations in the quenched approximation as well as in the presence of dynamical quarks. In the latter case, the spontaneous breaking of the chiral symmetry requires to go beyond a coupling expansion but can still be described in a controlled approximation scheme in terms of small parameters. We also review applications of the approach to nonzero temperature and chemical potential. (10.1088/1361-6633/ac36b8)
DOI : 10.1088/1361-6633/ac36b8
A master exceptional field theory
- Bossard Guillaume
- Kleinschmidt Axel
- Sezgin Ergin
Journal of High Energy Physics, Springer, 2021, 06, pp.185. We construct a pseudo-Lagrangian that is invariant under rigid E$_{11}$ and transforms as a density under E$_{11}$ generalised diffeomorphisms. The gauge-invariance requires the use of a section condition studied in previous work on E$_{11}$ exceptional field theory and the inclusion of constrained fields that transform in an indecomposable E$_{11}$-representation together with the E$_{11}$ coset fields. We show that, in combination with gauge-invariant and E$_{11}$-invariant duality equations, this pseudo-Lagrangian reduces to the bosonic sector of non-linear eleven-dimensional supergravity for one choice of solution to the section condi- tion. For another choice, we reobtain the E$_{8}$ exceptional field theory and conjecture that our pseudo-Lagrangian and duality equations produce all exceptional field theories with maximal supersymmetry in any dimension. We also describe how the theory entails non-linear equations for higher dual fields, including the dual graviton in eleven dimensions. Furthermore, we speculate on the relation to the E$_{10}$ sigma model. (10.1007/JHEP06(2021)185)
DOI : 10.1007/JHEP06(2021)185
Low-x improved TMD approach to the lepto- and hadroproduction of a heavy-quark pair
- Altinoluk Tolga
- Marquet Cyrille
- Taels Pieter
Journal of High Energy Physics, Springer, 2021, 06, pp.085. We study the lepto- and hadroproduction of a heavy-quark pair in the ITMD factorization framework for dilute-dense collisions. Due to the presence of a nonzero quark mass and/or nonzero photon virtuality, new contributions appear compared to the cases of photo- and hadroproduction of dijets, for which the ITMD framework was originally derived. These extra terms are sensitive to gluons that are not fully linearly polarized. At small x, those gluons emerge only when all saturation effects are carefully taken into account. Therefore, the resulting contributions are absent in linear small-x frameworks, where gluons are fully linearly polarized. We show, however, that even for large gluon transverse momentum, these contributions are not always negligible, due to the behavior of the off-shell hard factors. (10.1007/JHEP06(2021)085)
DOI : 10.1007/JHEP06(2021)085
Flow equations for disordered Floquet systems
- Thomson Steven
- Magano Duarte
- Schiro' Marco
SciPost Physics, SciPost Foundation, 2021, 11 (2), pp.028. In this work, we present a new approach to disordered, periodically driven (Floquet) quantum many-body systems based on flow equations. Specifically, we introduce a continuous unitary flow of Floquet operators in an extended Hilbert space, whose fixed point is both diagonal and time-independent, allowing us to directly obtain the Floquet modes. We first apply this method to a periodically driven Anderson insulator, for which it is exact, and then extend it to driven many-body localized systems within a truncated flow equation ansatz. In particular we compute the emergent Floquet local integrals of motion that characterise a periodically driven many-body localized phase. We demonstrate that the method remains well-controlled in the weakly-interacting regime, and allows us to access larger system sizes than accessible by numerically exact methods, paving the way for studies of two-dimensional driven many-body systems. (10.21468/SciPostPhys.11.2.028)
DOI : 10.21468/SciPostPhys.11.2.028
The Status and Future of Color Transparency and Nuclear Filtering
- Jain P
- Pire B
- Ralston J
, 2022, 2022 (4), pp.578–589.. 40 years after its introduction, the phenomenon of color transparency remains a domain of controversial interpretations of experimental data. We review present evidence for or against its manifestation in various exclusive hard scattering reactions. The nuclear transparency experiments reveal whether short distance processes dominate a scattering amplitude at some given kinematical point. We plead for a new round of nuclear transparency measurements in a variety of experimental setups , including near-forward exclusive reactions related to generalized parton distribution (GPD) physics and near-backward exclusive reactions related to transition distribution amplitudes (TDA) physics.
Universal record statistics for random walks and Lévy flights with a nonzero staying probability
- Majumdar Satya
- Mounaix Philippe
- Schehr Gregory
Journal of Physics A: Mathematical and Theoretical, IOP Publishing, 2021, 54 (31), pp.315002. We compute exactly the statistics of the number of records in a discrete-time random walk model on a line where the walker stays at a given position with a nonzero probability 0  p  1, while with the complementary probability 1 p, it jumps to a new position with a jump length drawn from a continuous and symmetric distribution f 0 (⌘). We have shown that, for arbitrary p, the statistics of records up to step N is completely universal, i.e., independent of f 0 (⌘) for any N. We also compute the connected two-time correlation function C p (m 1 , m 2) of the record-breaking events at times m 1 and m 2 and show it is also universal for all p. Moreover, we demonstrate that C p (m 1 , m 2) < C 0 (m 1 , m 2) for all p > 0, indicating that a nonzero p induces additional anticorrelations between record events. We further show that these anti-correlations lead to a drastic reduction in the fluctuations of the record numbers with increasing p. This is manifest in the Fano factor, i.e. the ratio of the variance and the mean of the record number, which we compute explicitly. We also show that an interesting scaling limit emerges when p ! 1, N ! 1 with the product t = (1 p) N fixed. We compute exactly the associated universal scaling functions for the mean, variance and the Fano factor of the number of records in this scaling limit. (10.1088/1751-8121/ac0a2f)
DOI : 10.1088/1751-8121/ac0a2f
Efficient second-harmonic generation of a high-energy, femtosecond laser pulse in a lithium triborate crystal
- Aparajit C.
- Jana Kamalesh
- Lad Amit
- Ved Yash
- Couairon Arnaud
- Kumar G. Ravindra
Optics Letters, Optical Society of America - OSA Publishing, 2021, 46 (15), pp.3540. (10.1364/OL.423725)
DOI : 10.1364/OL.423725
The tadpole problem
- Bena Iosif
- Blåbäck Johan
- Graña Mariana
- Lüst Severin
Journal of High Energy Physics, Springer, 2021, 11, pp.223. We examine the mechanism of moduli stabilization by fluxes in the limit of a large number of moduli. We conjecture that one cannot stabilize all complex-structure moduli in F-theory at a generic point in moduli space (away from singularities) by fluxes that satisfy the bound imposed by the tadpole cancellation condition. More precisely, while the tadpole bound in the limit of a large number of complex-structure moduli goes like 1/4 of the number of moduli, we conjecture that the amount of charge induced by fluxes stabilizing all moduli grows faster than this, and is therefore larger than the allowed amount. Our conjecture is supported by two examples: K3 × K3 compactifications, where by using evolutionary algorithms we find that moduli stabilization needs fluxes whose induced charge is 44% of the number of moduli, and Type IIB compactifications on $ \mathbbm{CP} ^{3}$, where the induced charge of the fluxes needed to stabilize the D7-brane moduli is also 44% of the number of these moduli. Proving our conjecture would rule out de Sitter vacua obtained via antibrane uplift in long warped throats with a hierarchically small supersymmetry breaking scale, which require a large tadpole. (10.1007/JHEP11(2021)223)
DOI : 10.1007/JHEP11(2021)223
E$_{9}$ exceptional field theory. Part II. The complete dynamics
- Bossard Guillaume
- Ciceri Franz
- Inverso Gianluca
- Kleinschmidt Axel
- Samtleben Henning
Journal of High Energy Physics, Springer, 2021, 05, pp.107. We construct the first complete exceptional field theory that is based on an infinite-dimensional symmetry group. E$_{9}$ exceptional field theory provides a unified description of eleven-dimensional and type IIB supergravity covariant under the affine Kac-Moody symmetry of two-dimensional maximal supergravity. We present two equivalent formulations of the dynamics, which both rely on a pseudo-Lagrangian supplemented by a twisted self-duality equation. One formulation involves a minimal set of fields and gauge symmetries, which uniquely determine the entire dynamics. The other formulation extends $ {\mathfrak{e}}_9 $ by half of the Virasoro algebra and makes direct contact with the integrable structure of two-dimensional supergravity. Our results apply directly to other affine Kac-Moody groups, such as the Geroch group of general relativity. (10.1007/JHEP05(2021)107)
DOI : 10.1007/JHEP05(2021)107
The Large Hadron–Electron Collider at the HL-LHC
- Agostini P.
- Aksakal H.
- Alekhin S.
- Allport P.P.
- Andari N.
- Andre K.D.J.
- Angal-Kalinin D.
- Antusch S.
- Aperio Bella L.
- Apolinario L.
- Apsimon R.
- Apyan A.
- Arduini G.
- Ari V.
- Armbruster A.
- Armesto N.
- Auchmann B.
- Aulenbacher K.
- Azuelos G.
- Backovic S.
- Bailey I.
- Bailey S.
- Balli F.
- Behera S.
- Behnke O.
- Ben-Zvi I.
- Benedikt M.
- Bernauer J.
- Bertolucci S.
- Biswal S.S.
- Blümlein J.
- Bogacz A.
- Bonvini M.
- Boonekamp M.
- Bordry F.
- Boroun G.R.
- Bottura L.
- Bousson S.
- Bouzas A.O.
- Bracco C.
- Bracinik J.
- Britzger D.
- Brodsky S.J.
- Bruni C.
- Brüning O.
- Burkhardt H.
- Cakir O.
- Calaga R.
- Caldwell A.
- Calıskan A.
- Camarda S.
- Catalan-Lasheras N.C.
- Cassou K.
- Cepila J.
- Cetinkaya V.
- Chetvertkova V.
- Cole B.
- Coleppa B.
- Cooper-Sarkar A.
- Cormier E.
- Cornell A.S.
- Corsini R.
- Cruz-Alaniz E.
- Currie J.
- Curtin D.
- d'Onofrio M.
- Dainton J.
- Daly E.
- Das A.
- Das S.P.
- Dassa L.
- de Blas J.
- Delle Rose L.
- Denizli H.
- Deshpande K.S.
- Douglas D.
- Duarte L.
- Dupraz K.
- Dutta S.
- Efremov A.V.
- Eichhorn R.
- Eskola K.J.
- Ferreiro E.G.
- Fischer O.
- Flores-Sánchez O.
- Forte S.
- Gaddi A.
- Gao J.
- Gehrmann T.
- Gehrmann-de Ridder A.
- Gerigk F.
- Gilbert A.
- Giuli F.
- Glazov A.
- Glover N.
- Godbole R.M.
- Goddard B.
- Gonçalves V.
- Gonzalez-Sprinberg G.A.
- Goyal A.
- Grames J.
- Granados E.
- Grassellino A.
- Gunaydin Y.O.
- Guo Y.C.
- Guzey V.
- Gwenlan C.
- Hammad A.
- Han C.C.
- Harland-Lang L.
- Haug F.
- Hautmann F.
- Hayden D.
- Hessler J.
- Helenius I.
- Henry J.
- Hernandez-Sanchez J.
- Hesari H.
- Hobbs T.J.
- Hod N.
- Hoffstaetter G.H.
- Holzer B.
- Honorato C.G.
- Hounsell B.
- Hu N.
- Hug F.
- Huss A.
- Hutton A.
- Islam R.
- Iwamoto S.
- Jana S.
- Jansova M.
- Jensen E.
- Jones T.
- Jowett J.M.
- Kaabi W.
- Kado M.
- Kalinin D.A.
- Karadeniz H.
- Kawaguchi S.
- Kaya U.
- Khalek R.A.
- Khanpour H.
- Kilic A.
- Klein M.
- Klein U.
- Kluth S.
- Köksal M.
- Kocak F.
- Korostelev M.
- Kostka P.
- Krelina M.
- Kretzschmar J.
- Kuday S.
- Kulipanov G.
- Kumar M.
- Kuze M.
- Lappi T.
- Larios F.
- Latina A.
- Laycock P.
- Lei G.
- Levitchev E.
- Levonian S.
- Levy A.
- Li R.
- Li X.
- Liang H.
- Litvinenko V.
- Liu M.
- Liu T.
- Liu W.
- Liu Y.
- Liuti S.
- Lobodzinska E.
- Longuevergne D.
- Luo X.
- Ma W.
- Machado M.
- Mandal S.
- Mäntysaari H.
- Marhauser F.
- Marquet C.
- Martens A.
- Martin R.
- Marzani S.
- Mcfayden J.
- Mcintosh P.
- Mellado B.
- Meot F.
- Milanese A.
- Milhano J.G.
- Militsyn B.
- Mitra M.
- Moch S.
- Mohammadi Najafabadi M.
- Mondal S.
- Moretti S.
- Morgan T.
- Morreale A.
- Nadolsky P.
- Navarra F.
- Nergiz Z.
- Newman P.
- Niehues J.
- Nissen E.A.
- Nowakowski M.
- Okada N.
- Olivier G.
- Olness F.
- Olry G.
- Osborne J.A.
- Ozansoy A.
- Pan R.
- Parker B.
- Patra M.
- Paukkunen H.
- Peinaud Y.
- Pellegrini D.
- Perez-Segurana G.
- Perini D.
- Perrot L.
- Pietralla N.
- Pilicer E.
- Pire B.
- Pires J.
- Placakyte R.
- Poelker M.
- Polifka R.
- Polini A.
- Poulose P.
- Pownall G.
- Pupkov Y.A.
- Queiroz F.S.
- Rabbertz K.
- Radescu V.
- Rahaman R.
- Rai S.K.
- Raicevic N.
- Ratoff P.
- Rashed A.
- Raut D.
- Raychaudhuri S.
- Repond J.
- Rezaeian A.H.
- Rimmer R.
- Rinolfi L.
- Rojo J.
- Rosado A.
- Ruan X.
- Russenschuck S.
- Sahin M.
- Salgado C.A.
- Sampayo O.A.
- Satendra K.
- Satyanarayan N.
- Schenke B.
- Schirm K.
- Schopper H.
- Schott M.
- Schulte D.
- Schwanenberger C.
- Sekine T.
- Senol A.
- Seryi A.
- Setiniyaz S.
- Shang L.
- Shen X.
- Shipman N.
- Sinha N.
- Slominski W.
- Smith S.
- Solans C.
- Song M.
- Spiesberger H.
- Stanyard J.
- Starostenko A.
- Stasto A.
- Stocchi A.
- Strikman M.
- Stuart M.J.
- Sultansoy S.
- Sun H.
- Sutton M.
- Szymanowski L.
- Tapan I.
- Tapia-Takaki D.
- Tanaka M.
- Tang Y.
- Tasci A.T.
- Ten-Kate A.T.
- Thonet P.
- Tomas-Garcia R.
- Tommasini D.
- Trbojevic D.
- Trott M.
- Tsurin I.
- Tudora A.
- Turk Cakir I.
- Tywoniuk K.
- Vallerand C.
- Valloni A.
- Verney D.
- Vilella E.
- Walker D.
- Wallon S.
- Wang B.
- Wang K.
- Wang K.
- Wang X.
- Wang Z.S.
- Wei H.
- Welsch C.
- Willering G.
- Williams P.H.
- Wollmann D.
- Xiaohao C.
- Xu T.
- Yaguna C.E.
- Yamaguchi Y.
- Yamazaki Y.
- Yang H.
- Yilmaz A.
- Yock P.
- Yue C.X.
- Zadeh S.G.
- Zenaiev O.
- Zhang C.
- Zhang J.
- Zhang R.
- Zhang Z.
- Zhu G.
- Zhu S.
- Zimmermann F.
- Zomer F.
- Zurita J.
- Zurita P.
J.Phys.G, 2021, 48 (11), pp.110501. The Large Hadron–Electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy-recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High-Luminosity Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron–proton and proton–proton operations. This report represents an update to the LHeC’s conceptual design report (CDR), published in 2012. It comprises new results on the parton structure of the proton and heavier nuclei, QCD dynamics, and electroweak and top-quark physics. It is shown how the LHeC will open a new chapter of nuclear particle physics by extending the accessible kinematic range of lepton–nucleus scattering by several orders of magnitude. Due to its enhanced luminosity and large energy and the cleanliness of the final hadronic states, the LHeC has a strong Higgs physics programme and its own discovery potential for new physics. Building on the 2012 CDR, this report contains a detailed updated design for the energy-recovery electron linac (ERL), including a new lattice, magnet and superconducting radio-frequency technology, and further components. Challenges of energy recovery are described, and the lower-energy, high-current, three-turn ERL facility, PERLE at Orsay, is presented, which uses the LHeC characteristics serving as a development facility for the design and operation of the LHeC. An updated detector design is presented corresponding to the acceptance, resolution, and calibration goals that arise from the Higgs and parton-density-function physics programmes. This paper also presents novel results for the Future Circular Collider in electron–hadron (FCC-eh) mode, which utilises the same ERL technology to further extend the reach of DIS to even higher centre-of-mass energies. (10.1088/1361-6471/abf3ba)
DOI : 10.1088/1361-6471/abf3ba
Probability distribution for the quantum universe
- Kehagias Alex
- Partouche Hervé
- Toumbas Nicolaos
Journal of High Energy Physics, Springer, 2021, 12, pp.165. We determine the inner product on the Hilbert space of wavefunctions of the universe by imposing the Hermiticity of the quantum Hamiltonian in the context of the minisuperspace model. The corresponding quantum probability density reproduces successfully the classical probability distribution in the ħ → 0 limit, for closed universes filled with a perfect fluid of index w. When −1/3 < w ≤ 1, the wavefunction is normalizable and the quantum probability density becomes vanishingly small at the big bang/big crunch singularities, at least at the semiclassical level. Quantum expectation values of physical geometrical quantities, which diverge classically at the singularities, are shown to be finite. (10.1007/JHEP12(2021)165)
DOI : 10.1007/JHEP12(2021)165
Relativistic spin sum rules and the role of the pivot
- Lorcé Cédric
European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2021, 81 (5), pp.413. Spin sum rules depend on the choice of a pivot, i.e. the point about which the angular momentum is defined, usually identified with the center of the nucleon. The latter is however not unique in a relativistic theory and has led to apparently contradictory results in the literature. Using the recently developed phase-space approach, we compute for the first time the contribution associated with the motion of the center of the nucleon, and we derive a general spin sum rule which reduces to established results after appropriate choices for the pivot and the spin component. (10.1140/epjc/s10052-021-09207-4)
DOI : 10.1140/epjc/s10052-021-09207-4
Hydrodynamic Diffusion and Its Breakdown near AdS2 Quantum Critical Points
- Arean Daniel
- Davison Richard A.
- Goutéraux Blaise
- Suzuki Kenta
Physical Review X, American Physical Society, 2021, 11 (3), pp.031024. Hydrodynamics provides a universal description of interacting quantum field theories at sufficiently long times and wavelengths, but breaks down at scales dependent on microscopic details of the theory. In the vicinity of a quantum critical point, it is expected that some aspects of the dynamics are universal and dictated by properties of the critical point. We use gauge-gravity duality to investigate the breakdown of diffusive hydrodynamics in two low-temperature states dual to black holes with <math display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math> horizons, which exhibit quantum critical dynamics with an emergent scaling symmetry in time. We find that the breakdown is characterized by a collision between the diffusive pole of the retarded Green’s function with a pole associated to the <math display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math> region of the geometry, such that the local equilibration time is set by infrared properties of the theory. The absolute values of the frequency and wave vector at the collision (<math display="inline"><msub><mi>ω</mi><mrow><mi>eq</mi></mrow></msub></math> and <math display="inline"><msub><mi>k</mi><mrow><mi>eq</mi></mrow></msub></math>) provide a natural characterization of all the low-temperature diffusivities <math display="inline"><mi>D</mi></math> of the states via <math display="inline"><mi>D</mi><mo>=</mo><msub><mi>ω</mi><mrow><mi>eq</mi></mrow></msub><mo stretchy="false">/</mo><msubsup><mi>k</mi><mrow><mi>eq</mi></mrow><mn>2</mn></msubsup></math>, where <math display="inline"><msub><mi>ω</mi><mrow><mi>eq</mi></mrow></msub><mo>=</mo><mn>2</mn><mi>π</mi><mi mathvariant="normal">Δ</mi><mi>T</mi></math> is set by the temperature <math display="inline"><mi>T</mi></math> and the scaling dimension <math display="inline"><mi mathvariant="normal">Δ</mi></math> of an operator of the infrared quantum critical theory. We confirm that these relations are also satisfied in a Sachdev-Ye-Kitaev chain model in the limit of strong interactions. Our work paves the way toward a deeper understanding of transport in quantum critical phases. (10.1103/PhysRevX.11.031024)
DOI : 10.1103/PhysRevX.11.031024
3d large $N$ vector models at the boundary
- Di Pietro Lorenzo
- Lauria Edoardo
- Niro Pierluigi
SciPost Physics, SciPost Foundation, 2021, 11 (3), pp.050. We consider a 4d scalar field coupled to large $N$ free or critical $O(N)$ vector models, either bosonic or fermionic, on a 3d boundary. We compute the $\beta$ function of the classically marginal bulk/boundary interaction at the first non-trivial order in the large $N$ expansion and exactly in the coupling. Starting with the free (critical) vector model at weak coupling, we find a fixed point at infinite coupling in which the boundary theory is the critical (free) vector model and the bulk decouples. We show that a strong/weak duality relates one description of the renormalization group flow to another one in which the free and the critical vector models are exchanged. We then consider the theory with an additional Maxwell field in the bulk, which also gives decoupling limits with gauged vector models on the boundary. (10.21468/SciPostPhys.11.3.050)
DOI : 10.21468/SciPostPhys.11.3.050
Two-loop corrections to the QCD propagators within the Curci-Ferrari model
- Barrios Nahuel
- Gracey John A.
- Peláez Marcela
- Reinosa Urko
Physical Review D, American Physical Society, 2021, 104 (9), pp.094019. We evaluate all two-point correlation functions of the Curci-Ferrari (CF) model in four dimensions and in the presence of mass-degenerate fundamental quark flavors, as a natural extension of an earlier investigation in the quenched approximation. In principle, the proper account of chiral symmetry breaking (<math display="inline"><mrow><mi>χ</mi><mi>SB</mi></mrow></math>) and the corresponding dynamical generation of a quark-mass function within the CF model requires one to go beyond perturbation theory [M. Peláez, U. Reinosa, J. Serreau, M. Tissier, and N. Wschebor, Phys. Rev. D 103, 094035 (2021)]. However, it is interesting to assess whether a perturbative description applies to correlation functions that are not directly sensitive to <math display="inline"><mrow><mi>χ</mi><mi>SB</mi></mrow></math>, such as the gluon, ghost and quark dressing functions. We compare our two-loop results for these form factors to QCD lattice data in the two-flavor case for two different values of the pion mass, one that is relatively far from the chiral limit, and one that is closer to the physical value. Our results confirm that the QCD gluon and ghost dressing functions are well described by a perturbative approach within the CF model, as already observed at one-loop order [M. Peláez, M. Tissier, and N. Wschebor, Phys. Rev. D 90, 065031 (2014)]. Our new main result is that the quark dressing function is also well captured by the perturbative approach, but only starting at two-loop order, as also anticipated [M. Peláez, M. Tissier, and N. Wschebor, Phys. Rev. D 90, 065031 (2014)]. The quark-mass function predicted by the CF model at two-loop order is in good agreement with the data if the quarks are not too light but it shows some clear tension with respect to the two-loop CF dressing functions in the close to physical case, as expected. Interestingly, however, we find that there is much less tension between the nonperturbative quark-mass function, as it can be obtained from lattice simulations or from M. Peláez, U. Reinosa, J. Serreau, M. Tissier, and N. Wschebor, Phys. Rev. D 103, 094035 (2021), and the two-loop CF dressing functions, which confirms the perturbative nature of the latter. (10.1103/PhysRevD.104.094019)
DOI : 10.1103/PhysRevD.104.094019

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