Publications

2026

• Uniqueness of D=8 minimal supergravity with two vector multiplets
  
  • Bossard Guillaume
  • Lao Bingxin
  • Minasian Ruben
  JHEP, 2026, 09, pp.192. There exist only four known string theories with minimal supersymmetry in eight dimensions, whose low energy effective descriptions are given by minimal supergravity coupled to $l=18$, $10$, or $2$ vector multiplets. It has been argued that these numbers are uniquely fixed by consistency conditions of the effective theory. In this work, we investigate the protected couplings of minimal supergravity coupled to two vector multiplets under the assumption that the theory admits a duality symmetry of the form $Γ_0(N)\times Γ_0(N)\subset {\rm SL}(2,\mathbb{Z}) \times {\rm SL}(2,\mathbb{Z})$ for some positive integer $N$. We show that consistency with anomaly cancellation, higher-dimensional uplifts, and gauge enhancement loci strongly constrains the allowed couplings and isolates a unique consistent theory in the BPS sector. In particular, we find that the Bianchi identity for the three-form flux cannot have gravitational contributions. (10.1007/JHEP09(2026)192)
  DOI : 10.1007/JHEP09(2026)192
• A Menagerie of Wormholes and Cosmologies in the Gravitational Path Integral
  
  • Betzios Panos
  • Ghiringhelli Paul
  • Gialamas Ioannis D
  • Papadoulaki Olga
  Journal of High Energy Physics, Springer, 2026, 06, pp.171. We analyse a variety of Euclidean saddles in the gravitational path integral, with asymptotic AdS boundary conditions, in a class of Einstein-Scalar-Maxwell models. These include single boundary solutions, usual and wineglass wormholes, as well as more exotic (quasi)-oscillatory saddles. Our construction shows how an unbound number of oscillations gets tamed, when flat directions of the potential get lifted. We find several interesting phase transitions between these solutions. The Euclidean wormhole backgrounds can be analytically continued to Lorentzian FLRW universes. Some of them contain an early period of inflation. We delineate the conditions under which they can be the dominant saddles in the gravitational path integral and use them to estimate ratios of probabilities for different cosmological outcomes. (10.1007/JHEP06(2026)171)
  DOI : 10.1007/JHEP06(2026)171
• Before the Bang: Wormholes at the Dawn of the Universe
  
  • Betzios Panos
  • Ghiringhelli Paul
  • Gialamas Ioannis D
  • Papadoulaki Olga
  Int.J.Mod.Phys.D, 2026. This essay discusses recent progress on Euclidean wormholes as candidate contributions to the Universe's initial quantum state. The comparison with the Hartle-Hawking no-boundary proposal highlights both a conceptual affinity and genuine advance: wormholes retain the relevance of Euclidean-saddles as encoders of properties of cosmological wavefunctions, while they broaden the class of regular saddles that are physically relevant for inflating universes and are capable of resolving issues that plague the no-boundary proposal. The principal achievement of the wormhole program is to enlarge the semiclassical initial-condition land-scape in a way that is physically rich, conforms with Holographic expectations and as such becomes increasingly relevant for early-universe model building, within UV complete theories of quantum gravity. (10.1142/S0218271826410166)
  DOI : 10.1142/S0218271826410166
• Extracting light-cone wave functions from covariant amplitudes: a detailed study in scalar field theory
  
  • Munier Stéphane
  Physical Review D, American Physical Society, 2026, 114 (3), pp.036015. We propose a conjectured formula that systematically maps covariant off-shell amplitudes to light-cone wave functions in scalar field theory. Through an explicit comparison at one-loop accuracy, we establish its equivalence to the light-cone perturbation theory series, thereby validating the conjecture at this order. Applying this formula, we efficiently re-derive wave functions from known covariant amplitudes, bypassing both the conceptual complexities of light-cone quantization and the technical challenges of perturbative calculations in this framework. In addition to simplifying computations, this approach opens new avenues for applications in gauge theories and deeper explorations of the fundamental equivalence between covariant and light-cone quantization. (10.1103/63qq-rx6g)
  DOI : 10.1103/63qq-rx6g
• Physique de la matière condensée
  
  • Georges Antoine
  L'Annuaire du Collège de France. Résumés des cours et travaux, Collège de France, 2026 (122), pp.97-102. (10.4000/15e0h)
  DOI : 10.4000/15e0h
• Quark orbital angular momentum from chiral symmetry breaking in QCD
  
  • Kim June-Young
  • Won Ho-Yeon
  • Weiss Christian
  Physics Letters B, Elsevier, 2026, 882, pp.140980. The flavor-nonsinglet (<math altimg="si13.svg"><mrow><mi>u</mi><mo linebreak="goodbreak">−</mo><mi>d</mi></mrow></math>) quark angular momentum (AM) in the proton is computed based on the effective spin-flavor dynamics emerging from chiral symmetry breaking by QCD instantons. The QCD AM operators are converted to effective spin-flavor operators expressing instanton-induced chiral interactions. A large negative orbital AM <math altimg="si5.svg"><msub><mi>L</mi><mrow><mi>u</mi><mo>−</mo><mi>d</mi></mrow></msub></math> arises from the interactions of the quarks with the chiral mean field in the proton in the large-Nc limit. It cancels part of the large positive spin AM <math altimg="si4.svg"><msub><mi>S</mi><mrow><mi>u</mi><mo>−</mo><mi>d</mi></mrow></msub></math> and reduces the total AM <math altimg="si14.svg"><mrow><msub><mi>J</mi><mrow><mi>u</mi><mo>−</mo><mi>d</mi></mrow></msub><mo linebreak="goodbreak">=</mo><msub><mi>S</mi><mrow><mi>u</mi><mo>−</mo><mi>d</mi></mrow></msub><mo linebreak="goodbreak">+</mo><msub><mi>L</mi><mrow><mi>u</mi><mo>−</mo><mi>d</mi></mrow></msub></mrow></math>, in agreement with lattice QCD calculations. (10.1016/j.physletb.2026.140980)
  DOI : 10.1016/j.physletb.2026.140980
• Walsh series and Pauli decompositions: representing functions on a quantum system
  
  • Ayral Thomas
  • Boudin Laurent
  • Maday Yvon
  • Serret Michel Fabrice
  , 2026. The Pauli decomposition of quantum operators is of prime importance to many quantum algorithms, but computing it numerically often incurs an exponential cost in the number of qubits. In this work, we extend the connection between Pauli decompositions of operators on qubit-based quantum systems and the Walsh L2-basis defined from dyadic rationals. We prove that diagonal operators can be decomposed using the Walsh interpolant of the associated function, and introduce a new estimation method based on truncated Walsh series with exponential convergence in the number of qubits. We also derive explicit Walsh expansions for Fourier basis functions, which, combined with known results for polynomials, enable analytical Pauli decompositions for functions expressed as linear combinations of both. Finally, we apply these techniques to Gross-Pitaevskii energy operators, obtaining explicit Pauli decompositions including the nonlinear interaction term.
• Heavy-Heavy-Light Asymptotics from Thermal Correlators
  
  • Burić Ilija
  • Mangialardi Francesco
  • Russo Francesco
  • Schomerus Volker
  • Vichi Alessandro
  Journal of High Energy Physics, Springer, 2026, 04, pp.027. We revisit the calculation of spectral densities and heavy-heavy-light (HHL) operator product expansion (OPE) coefficients in three-dimensional conformal field theories using thermal one-point functions on $S^1 \times S^2$. A central element of our analysis is a new inversion formula for one-point functions which is derived via Casimir differential equations. We develop systematic expansions of the spectral density and HHL OPE coefficients in the regime of large $Δ_H$. We validate our analytic tools by comparing the results with the partial wave expansions of thermal one-point functions in free field theories. The algorithms developed for these expansions make full use of Casimir recursion relations, thereby extending their applicability into the heavy exchange regime. In the end, we observe excellent agreement with our analytic predictions and an improvement of up to three orders of magnitude compared to all previous leading order estimates of the CFT data even for moderate values of $Δ_H$. (10.1007/JHEP04(2026)027)
  DOI : 10.1007/JHEP04(2026)027
• Fermion parity switching in a short Kitaev chain coupled to a photonic cavity
  
  • Fernandez Becerra Victor
  • Dmytruk Olesia
  Physical Review B, American Physical Society, 2026, 113 (16), pp.165410. We study a finite-length Kitaev chain coupled to a single mode photonic cavity. The topological phase of the finite-length Kitaev chain is characterized by the presence of fermion parity switching points that correspond to the degeneracy between even and odd parity ground states. Using exact diagonalization, we compute the many-body energy spectrum of the electron-photon Hamiltonian and we find that the ground state in the topological phase of the Kitaev chain is only weakly affected by the cavity coupling. This is in contrast with the excited states showing strong dependence on the cavity frequency. We find that the photon number and the photonic field quadratures peak at values of the chemical potential corresponding to parity switching points revealing a property of the finite-length Kitaev chain in the topological phase. This later finding suggests that quantum optics experiments could be used to detect topological features of the Kitaev chain embedded into a photonic cavity. Moreover, calculations of photonic quadratures reveal squeezed states that are both captured by the exact diagonalization technique and mean-field decoupling. However, the mean-field approach fails to correctly capture the photonic probability in the odd photonic states. (10.1103/hszk-ymf3)
  DOI : 10.1103/hszk-ymf3
• The Lee-Yang model and its generalizations through the lens of long-range deformations
  
  • Eustachon Fanny
  EPL, 2026, 156 (4), pp.40004. In two dimensions, the non-unitary class of conformal minimal models, $\mathcal{M}(2,2m+1)$, has been recently conjectured to arise as renormalization-group fixed points of scalar field theories with complex $iφ^{2m-1}$ interaction, $m\in \mathbb{N}$, $m\ge2$. We test a variation of this conjecture through the perturbative study of two separate long-range constructions based on respectively the minimal model and its potential Landau-Ginzburg formalism. For $m>2$, inconsistencies are found when subsequently relating both constructions. In contrast, the long-range Lee-Yang model, the $m=2$ case, is shown to be analogue to the long-range Ising model. (10.1209/0295-5075/ae9daf)
  DOI : 10.1209/0295-5075/ae9daf
• Ab initio spin Hamiltonians and magnetism of Ce and Yb triangular-lattice compounds
  
  • Pourovskii Leonid
  • Soares Rafael
  • Wietek Alexander
  Physical Review B, American Physical Society, 2026, 113 (6), pp.L060401. We calculate the crystal-field splitting, ground-state Kramers doublet and intersite exchange interactions within the ground-state doublet manifold using an ab initio Hubbard-I based approach for a representative set of Ce and Yb triangular-lattice compounds. These include the putative quantum spin liquids (QSL) RbCeO₂ and YbZn₂GaO₅ and the antiferromagnets KCeO₂ and KCeS₂. The calculated nearest-neighbor (NN) couplings are antiferromagnetic and exhibit noticeable anisotropy. The next-nearest-neighbor (NNN) couplings are ferromagnetic in the Ce systems and dominated by classical dipole-dipole interactions in the Yb case. Solving the resulting effective spin-1/2 models by exact diagonalization up to N = 36 sites, we predict ordered magnetic ground states for all systems, including the two QSL candidates. We explore the phase space of an anisotropic NN + isotropic NNN triangular-lattice model finding that a significant antiferromagnetic NNN coupling is required to stabilize QSL phases, while the NN exchange anisotropy is detrimental to them. Our findings highlight a possibly important role of deviations from the perfect triangular model -like atomic disorder -in real triangular-lattice materials. (10.1103/95x5-3fnn)
  DOI : 10.1103/95x5-3fnn
• Hydrodynamics in the Carrollian regime
  
  • Kolekar Kedar S
  • Mandal Taniya
  • Shukla Ashish
  • Soni Pushkar
  Int.J.Mod.Phys.A, 2026, 41 (02), pp.2650016. Carroll hydrodynamics arises in the $c\to 0$ limit of relativistic hydrodynamics. Instances of its relevance include the Bjorken and Gubser flow models of heavy-ion collisions, where the ultrarelativistic nature of the flow makes the physics effectively Carrollian. In this paper, we explore the structure of hydrodynamics in what can be termed as the Carrollian regime, where instead of keeping only the leading terms in the $c\to 0$ limit of relativistic hydrodynamics, we perform a small-$c$ expansion and retain the subleading terms as well. We do so both for perfect fluids as well as viscous fluids incorporating first order derivative corrections. As apposite applications of the formalism, we utilize the subleading terms to compute modifications to the Bjorken and Gubser flow equations which bring in, in particular, dependence on rapidity. (10.1142/S0217751X26500168)
  DOI : 10.1142/S0217751X26500168
• Holographic shear correlators at low temperatures, and quantum $η/s$
  
  • Kanargias Alexandros
  • Kiritsis Elias
  • Murthy Sameer
  • Papadoulaki Olga
  • Porfyriadis Achilleas P
  Journal of High Energy Physics, Springer, 2026, 07, pp.149. The strongly-coupled 3-dimensional theory, holographically dual to black branes at fixed chemical potential $\muext$ and temperature $T \ll μ$ is considered in AdS$_4$ Einstein-Maxwell theory. The retarded Green's functions at frequency $ω$ is calculated using holography in the regime $ω, T \ll \muext$ but otherwise arbitrary. When the transverse space has finite volume, there is a non-zero energy scale $E_\text{gap}$, scaling as $1/μ$ for large $μ$, below which quantum-gravitational corrections due to the fluctuations of the nearly-gapless Schwarzian modes become important. Such corrections to the retarded Green's function are calculated at different relative values of $ω$, $T$, and $E_\text{gap}$. The $ω\to 0$ limit is used to define the shear viscosity $η$. As the temperature is lowered below $μ$, quantum corrections are found to increase the value of $η$ with respect to its semiclassical value. The quantum-corrected result for $η$ diverges as $\sqrt{E_\text{gap}/T}$ at $T \ll E_\text{gap}$, in accord with corresponding results for the absorption cross section. The quantum result for the ratio $η/s$, where $s$ is the entropy density, dips below the semiclassical limit of $1/4π$ when $E_\text{gap} \ll T \ll μ$, then turns back to increase towards lower temperatures, and finally diverges at temperatures much below $E_\text{gap}$. (10.1007/JHEP07(2026)149)
  DOI : 10.1007/JHEP07(2026)149
• Simple Scaling Laws for Energy Correlators in Nuclear Matter
  
  • Andres Carlota
  • Dominguez Fabio
  • Holguin Jack
  • Marquet Cyrille
  • Moult Ian
  Physical Review Letters, American Physical Society, 2026, 136 (12), pp.122301. Collider experiments involving nuclei provide a direct means of studying exotic states of nuclear matter. Recent measurements of energy correlators in both proton-nucleus (p-A) and nucleus-nucleus (A-A) collisions reveal sizable modifications, attributable to nuclear effects, compared to proton-proton (p-p) collisions. Energy correlators, and their associated light-ray operator product expansion (OPE), allow scaling behaviors of the measured spectrum to be directly mapped to properties of the underlying quantum field theory. Here, we demonstrate for the first time how this mapping occurs in nuclear collisions, and highlight how the light-ray OPE characterizes leading nuclear effects. We show that the leading modification to the energy correlator distribution is characterized by an enhancement of the expectation value of twist-4 light-ray operators, resulting in a scaling for the ratio of the two-point correlator in nuclear matter to that in vacuum of $\sim 1+a\theta^2$ up to quantum corrections. We verify that this leading twist-4 correction accurately describes recent A-A and p-A data, and is thus sufficient to capture the scaling behavior within the angular range measured for jet radii used in nuclear experiments. Our light-ray OPE based approach lays the groundwork for a rigorous characterization of nuclear modification to energy correlator observables. (10.1103/sw7p-7jbp)
  DOI : 10.1103/sw7p-7jbp
• Complex logistic equation for universal energy evolution in hadronic elastic scattering
  
  • Kohara Anderson Kendi
  Physical Review D, American Physical Society, 2026, 113 (11), pp.116041. We introduce a universal evolution equation for elastic scattering of hadrons, derived from Reggeon field theory and solved in closed analytical form. The equation has a complex logistic structure and evolves initial amplitude profiles from existing models at a fixed energy, reproducing both differential cross sections and integrated quantities over a broad energy range. It admits a unique solution for each initial condition and rigorously satisfies unitarity, the Froissart–Martin bound, and dispersion relations. The dynamics are governed by two physically meaningful parameters: the effective Pomeron mass <math display="inline"><msub><mi>ε</mi><mi mathvariant="script">P</mi></msub></math> and the nonlinear coupling <math display="inline"><mrow><mi>λ</mi></mrow></math>, both fitted at a single energy. By decoupling the nonperturbative input from the universal energy evolution, the framework enables model-independent extrapolations and provides a minimal predictive alternative to eikonal resummation. Moreover, the structure of the equation—featuring rapidity evolution, saturation, and impact-parameter dependence—shares qualitative features with nonlinear QCD equations at small-<math display="inline"><mi>x</mi></math>, such as Balitsky-Kovchegov and Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov, and Kovner, suggesting a possible bridge between Regge-based and QCD-based approaches to high-energy scattering. (10.1103/xz23-bqg9)
  DOI : 10.1103/xz23-bqg9
• Unitary perturbation theory on the light cone
  
  • Munier Stéphane
  European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2026, 86 (3), pp.238. Light-cone perturbation theory is a powerful tool for calculating high-energy scattering amplitudes, particularly for quantum particles such as electrons, photons, or protons scattering off heavy nuclei, a process analogous to potential scattering. Central to these computations are the light-cone wave functions of incoming and outgoing particles, representing the projection of dressed initial and final states onto partonic Fock states. The dressed states are obtained by applying an evolution operator in the Dirac picture to bare partonic states, which may be interpreted physically as a time evolution from preparation to interaction. In standard approaches, a non-unitary operator is used, and proper normalization is imposed a posteriori. Here, we systematically develop perturbation theory from a perturbatively unitary evolution operator, using adiabatic switching to regularize the infinite-time limits. This provides a theoretically coherent framework for organizing calculations, reproducing known results entirely diagrammatically without enforcing unitarity by hand. We illustrate the method with a simple quantum mechanical model, enabling calculations to arbitrary perturbative orders, and then evaluate wave functions in field theories quantized on the light cone, focusing on a massive scalar theory with cubic interaction at one-loop accuracy. (10.1140/epjc/s10052-025-15194-7)
  DOI : 10.1140/epjc/s10052-025-15194-7
• Critical and multicritical Lee-Yang fixed points in the local potential approximation
  
  • Benedetti Dario
  • Eustachon Fanny
  • Zanusso Omar
  Journal of High Energy Physics, Springer, 2026, 05, pp.281. The multicritical generalizations of the Lee-Yang universality class arise as renormalization-group fixed points of scalar field theories with complex $iφ^{2n+1}$ interaction, $n\in\mathbb{N}$, just below their upper critical dimension. It has been recently conjectured that their continuation to two dimensions corresponds to the non-unitary conformal minimal models $\mathcal{M}(2,2n+3)$. Motivated by that, we revisit the functional renormalization group approach to complex $\mathcal{P}\mathcal{T}$-symmetric scalar field theories in the Local Potential Approximation, without or with wavefunction renormalization (LPA and LPA' respectively), aiming to explore the fate of the $iφ^{2n+1}$ theories from their upper critical dimension to two dimensions. The $iφ^{2n+1}$ fixed points are identified using a perturbative expansion of the functional fixed-point equation near their upper critical dimensions, and they are followed to lower dimensions by numerical integration of the full equation. A peculiar feature of the complex $\mathcal{P}\mathcal{T}$-symmetric potentials is that the fixed points are characterized by real but negative anomalous dimensions $η$, and in low dimension $d$, this can lead to a change of sign of the scaling dimensions $Δ=(d-2+η)/2$, thus requiring a novel analysis of the analytical properties of the functional fixed-point equations. We are able to follow the Lee-Yang universality class ($n=1$) down to two dimensions, and numerically determine the scaling dimension of the fundamental field as a function of $d$. On the other hand, within the LPA', multicritical Lee-Yang fixed points with $n>1$ cannot be continued to $d=2$ due to the existence of unexpected non-perturbative fixed points that annihilate with the $iφ^{2n+1}$ fixed points. (10.1007/JHEP05(2026)281)
  DOI : 10.1007/JHEP05(2026)281
• Ordering-Independent Wheeler-DeWitt Equation for Flat Minisuperspace Models
  
  • Franken Victor
  • Kaimakkamis Eftychios
  • Partouche Hervé
  • Toumbas Nicolaos
  Classical and Quantum Gravity, IOP Publishing, 2026, 43 (10), pp.105023. We consider minisuperspace models with quadratic kinetic terms, assuming a flat target space and a closed Universe. We show that, upon canonical quantization of the Hamiltonian, only a restricted subset of operator orderings is consistent with the path-integral viewpoint. Remarkably, all consistent orderings are physically equivalent to all orders in $\hbar$. Specifically, each choice of path-integral measure in the definition of the wavefunction path integral uniquely determines an operator ordering and hence a corresponding Wheeler-DeWitt equation. The consistent orderings are in one-to-one correspondence with the Jacobians associated with all field redefinitions of a set of canonical degrees of freedom. For each admissible operator ordering--or equivalently, each path-integral measure--we identify a definite, positive Hilbert-space inner product. All such prescriptions define the same quantum theory, in the sense that they lead to identical physical observables. We illustrate our formalism by applying it to de Sitter Jackiw-Teitelboim gravity and to the Starobinsky model. (10.1088/1361-6382/ae6c8e)
  DOI : 10.1088/1361-6382/ae6c8e
• Mega-Hertz Gravitational Waves from Neutron Star Mergers
  
  • Casalderrey-Solana Jorge
  • Mateos David
  • Sanchez-Garitaonandia Mikel
  Physical Review Letters, American Physical Society, 2026, 136 (10), pp.101401. Neutron star mergers provide a unique laboratory for the study of strong-field gravity coupled to Quantum Chromodynamics in extreme conditions. The frequencies and amplitudes of the resulting gravitational waves encode invaluable information about the merger. Simulations to date have shown that these frequencies lie in the kilo-Hertz range. They have also shown that, if Quantum Chromodynamics possesses a first-order phase transition at high baryon density, then this is likely to be accessed during the merger dynamics. Here we show that this would result in the nucleation of superheated and/or supercompressed bubbles whose subsequent dynamics would produce gravitational waves in the Mega-Hertz range. We estimate the amplitude of this signal and show that it may fall within the expected sensitivity of future superconducting radio-frequency cavity detectors for mergers at distances up to tens of Mega-parsecs. (10.1103/6yz9-94ql)
  DOI : 10.1103/6yz9-94ql
• Near-extremal holographic charge correlators
  
  • Goutéraux Blaise
  • Ramirez David M
  • Sanchez-Garitaonandia Mikel
  • Supiot Clément
  Phys.Rev.D, 2026, 114 (8), pp.086006. We analytically compute the low-temperature charge correlators in near-extremal black holes with a planar horizon and an infrared $\mathrm{AdS}_2\times \Bbb{R}^2$ extremal geometry, finding excellent agreement with numerical calculations. The analytical result consistently describes the crossover between the hydrodynamic diffusive regime at low frequencies and wavenumbers, and the quantum, zero-temperature regime at high frequencies and wavenumbers. We analytically resolve the successive collisions between the diffusive pole and the non-hydrodynamic poles sourced by the infrared $\mathrm{AdS}_2\times \Bbb{R}^2$ geometry. We demonstrate that in the $T=0$ limit, a pair of gapless poles survive with a dispersion relation $ω_\pm=-i d_2 k^2-i d_4 k^4-i\tilde d_4 k^4(\pm iπ+\log k^2) $. The nonanalytic contributions arise from the interplay with the branch cut formed by the condensation of the non-hydrodynamic poles. The real part is caused by the `snatching' of one of the non-hydrodynamic poles by the hydrodynamic diffusive pole. (10.1103/hbf8-wc92)
  DOI : 10.1103/hbf8-wc92