We report stronger evidence for the $X(7200)$ state and markedly improved measurements of the $X(6900)$ resonance parameters based on a combined analysis of the di- $J/\psi$ mass spectrum using published data from LHCb, ATLAS, and CMS. Through simultaneous fits to the datasets from all three experiments, we observe the $X(6900)$ with overwhelming significance ( $ \gt 12\sigma$ ) and determine its mass and width with improved precision. For the $X(7200)$ , we find consistent signals across multiple interference models, with significances ranging from $3.7\sigma$ to $6.6\sigma$ ; in the best-fit model (the CMS three-resonance scheme), the significance reaches $6.6\sigma$ , providing substantially stronger evidence for this state. Our results underscore the essential role of interference effects in fully charmed tetraquark spectroscopy and offer new constraints on their production mechanisms at the LHC.

China

Yuan Wang

Ran Li

Bin Zhong

Ya-Qian Wang

Enhanced evidence of $\textit{X}$(7200) and improved measurements of $\textit{X}$(6900) parameters from a combined LHCb-ATLAS-CMS analysis * Supported by the National Natural Science Foundation of China (NSFC) (12475077)

We give an explicit closed form description of the late-time near-horizon approach to dynamical extreme Reissner–Nordström (DERN) black holes. These are spherically symmetric dynamical solutions of Einstein-Maxwell theory coupled to a neutral scalar that feature: (i) a spacetime metric which tends to that of a static extreme Reissner–Nordström (RN), and (ii) a scalar field which exhibits the linear Aretakis instability ad infinitum in the non-linear theory. We employ the two-dimensional Jackiw-Teitelboim (JT) gravity to solve explicitly for the non-linear s-wave dynamics of the four-dimensional theory near an AdS × S throat. For a teleologically defined black hole horizon, we impose boundary conditions on JT’s dilaton field (which encodes the gravitational dynamics) and the scalar matter as follows: (i) the JT dilaton decays at late times on the AdS boundary to a value that corresponds to a static extreme RN in the exterior, and (ii) the scalar obeys boundary conditions characteristic of linear Aretakis behavior on AdS . We ensure our DERN solutions are singularity-free and we note that our approach to DERN is accompanied by a final burst of outgoing scalar matter flux leaking out of the AdS throat. The boundary conditions we impose on the JT dilaton place its late-time boundary profile on the threshold of black hole formation with sub-extreme and super-extreme RN on either side of our DERNs.

Greece

Achilleas Porfyriadis

Christopher Rosen

Georgios Tsaraktsidis

Approaching a dynamical extreme black hole horizon

In the operator product expansion (OPE) of hard scattering amplitudes, the twist-3 operators describe local colored Lorentz forces acting on a quark, thereby providing a measure of the strength of the gluon fields. Its value is directly accessible from the nucleon twist-3 polarized <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mn>2</mn></msub></math>-parton distribution function. In the semiclassical (instanton-based) QCD vacuum models, the leading nonperturbative contribution stems from correlated instanton-antiinstanton pairs, or molecules. We analyze the magnitude of the color force on a struck quark in light hadrons (pion and nucleon), in the context of the instanton liquid model (ILM). We derive explicitly the pertinent form factors associated with the color Lorentz force and show that they are intimately related to the pertinent hadronic gravitational and transversity form factors. Using the ILM enhanced by molecules, we detail the ensuing colored force distribution in the transverse plane for the luminal pions and nucleons. The results for the nucleons are in good agreement with those recently reported from a lattice collaboration.

United States

Wei-Yang Liu

Edward Shuryak

Ismail Zahed

Color force acting on a quark in the pion and nucleon

The Quantum Mpemba Effect (QME) — the counter-intuitive phenomenon where states further from equilibrium can relax faster than those closer to it — challenges standard expectations of quantum thermalization. In this work, we introduce Krylov complexity as a sensitive diagnostic for the QME. We show that Krylov spread complexity encodes the asymmetry essential to the effect, and we define a new class of projective (a)symmetric complexities that sharpen this connection. Strikingly, the structure of these projective complexities at the initial moment (t=0) already carries predictive power for the onset of Mpemba-like inversions, obviating the need for explicit time evolution. Our results suggest that the geometry of states in Krylov space captures deep information about non-monotonic relaxation and provides a powerful framework for diagnosing and anticipating anomalous thermalization phenomena in quantum systems.

South Africa

Cameron Beetar

Jeff Murugan

Hendrik Zyl

(A)Symmetric complexity and the Quantum Mpemba Effect

We show that the leading nonanalytic terms in the small-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>t</mi></mrow></math> expansion of the energy-momentum tensor form factors of an electrically charged particle in QED can be correctly derived in a classical model of the electron by Białynicki-Birula. Based on the lucidity of the employed exactly solvable model, we comment also on the recently proposed concept of a regularized proton <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi></math>-term.

Grace Gardella

Mira Varma

Peter Schweitzer

Energy-momentum tensor in a classical model of the electron

We study the evolution of neutrinos electroweakly interacting with a rotating matter. The description of neutrinos is based on the Dirac equation in the corotating noninertial frame where matter is at rest. We find the solution of this Dirac equation, where the matter angular velocity is accounted for exactly, for massless neutrinos. In case of massive particles, this solution is obtained for a slowly rotating matter. Our findings are compared with previous research. We consider two applications of our results. First, we compute the electroweak contribution to the vector current of neutrinos along the rotation axis, which is analogous to the chiral vortical effect. This current is shown to be nonzero for both massless and massive particles. Then, we take into account the nonzero mixing between different mass eigenstates. It allows us to study neutrino flavor oscillations in rotating matter and account for noninertial effects. We derive the transition probability which reveals the resonance. These findings generalize the description of neutrino oscillations in a nonmoving matter. Some astrophysical applications are briefly discussed.

Russia

Alexander Breev

Maxim Dvornikov

Relativistic quantum mechanics of massive neutrinos in a rotating frame

We study a massless Dirac field subjected to two alternative boundary conditions on two parallel thin walls, in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>d</mi><mo>+</mo><mn>1</mn></mrow></math> dimensions. The two configurations correspond to the system being even or odd under reflection about the midplane between the two walls, and lead to qualitatively different behaviors. The even (symmetric) configuration produces an attractive Casimir force, whereas the odd (antisymmetric) one yields repulsion, in agreement with a general theorem linking parity to the sign of the fermionic Casimir effect. We complement this result by studying two phenomena associated with the vacuum fluctuations responsible for the Casimir interaction, both of which are also sensitive to parity: the correlation between currents concentrated on the walls, and the induced bulk current under the influence of an external electric field. For the latter we show that, in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mo>+</mo><mn>1</mn></math> dimensions, an induced transverse (Hall-like) current arises, whose spatial profile inherits the symmetry of the confining potential.

Argentina

Aitor Fernández

César D. Fosco

Parity-dependent Casimir forces and Hall currents for a confined Dirac field

We study the natural scheme-independent quantity obtained from the three-sphere partition function of a (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mo>+</mo><mn>1</mn></mrow></math>)-dimensional quantum field theory by removing all local counterterm ambiguities. At conformal fixed points this quantity equals the standard <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>F</mi></math>-theorem invariant. Conformal perturbation theory shows that it locally decreases at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><msup><mi>g</mi><mn>2</mn></msup><mo stretchy="false">)</mo></math> under any relevant scalar deformation of a three-dimensional Conformal Field Theory. However, an exact analysis of the free massive scalar on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>S</mi><mn>3</mn></msup></math> shows that this sphere-free-energy interpolant is not monotone along the full renormalization-group flow: it dips below its infrared value and then returns to it. Thus the natural counterterm-subtracted quantity built from sphere thermodynamics is not, by itself, a monotone <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>F</mi></math>-function. We trace the obstruction to the second-order differential operator required to eliminate the local ambiguities.

Italy

Giacomo Santoni

Francesco Scardino

Scheme independent 3-sphere free energy is not a monotone <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>F</mi></math>-function

Testing Lorentz symmetry in strong gravitational fields provides a unique probe of extensions to standard model. The orbital motions of the S-stars around the supermassive black hole Sgr A* provide a natural laboratory for such tests. In this paper, we analyze the S2 orbital data focusing on a static and spherically symmetric black hole within Kalb–Ramond gravity, where the deviations from general relativity are encoded in a single Lorentz-violating parameter ℓ introduced by the Kalb–Ramond tensor field. Using a full 14-dimensional Markov Chain Monte Carlo analysis under uniform and Gaussian priors, we obtain <math altimg='si41.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><msubsup><mrow><mn>1.60</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></mrow><mrow><mo>&#8722;</mo><mn>1.76</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow><mrow><mo>+</mo><mn>1.38</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow></msubsup></mrow></math> and <math altimg='si42.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><msubsup><mrow><mo>&#8722;</mo><mn>1.02</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></mrow><mrow><mo>&#8722;</mo><mn>1.19</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow><mrow><mo>+</mo><mn>1.26</mn><mo>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow></msubsup></mrow></math> at 1 <italic>&#963;</italic> confidence level, respectively. These constraints are about three orders of magnitude tighter than those from Event Horizon Telescope imaging of Sgr A*. We also perform MCMC simulation by fitting data of S38 and S55 stars, as well as their joint analysis. Our results show that the best fit values of &#8467; in all simulations are always of <math altimg='si43.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></math> order, but S2 star provides the most stringent constraints on the parameters because S2 star has higher precision observational data comparing to the fewer public data for other two stars.

Qi Qi

Yu Sang

Xiao-Mei Kuang

Detecting Lorentz-violation induced by a tensor field with S-star’s motion around Sgr A*

Scalar field theories in (A)dS with integer scaling dimensions ∆ = $\textit{k}$ + 1 are characterised by the existence of a pair of (anti-)holomorphic higher-spin currents. We explore the consequences of this to describe their quantisation and subsets of their linear and non-linear symmetries, taking care to treat AdS and dS separately. In particular, we point out that the theories admit mode expansions reminiscent of standard two-dimensional conformal field theories in complex coordinates, with which we are able to construct a large set of symmetry transformations which includes Virasoro symmetry. We further leverage holomorphicity of the currents to show that the significant subset of the full symmetries of theories with $\textit{k >}$ 0 is captured by a chiral algebra, which is a subalgebra of the one in the $\textit{k}$ = 0 (massless) theory. This allows us to identify integrable deformations for $\textit{k}$ ∈ {0$\textit{,}$ 1$\textit{,}$ 2}. We finally observe that a lack of integrable deformations for $\textit{k >}$ 2 is a consequence of a known conjecture.