We investigate dilepton production in a thermalized quark-gluon plasma subject to global rotation, in the rigid rotating approximation. We consider a generic process involving quark-antiquark annihilation followed by the emission of a highly energetic virtual photon decaying into a dilepton pair. For this process, we compute the dilepton emission rate from the imaginary part of the photon polarization tensor, at finite temperature and vorticity. Our results show that vorticity induces characteristic modifications in the light dilepton channel, namely, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><msup><mi>e</mi><mo>+</mo></msup></math> production, where the emission spectrum exhibits a suppression at low transverse mass together with a mild shift of the production threshold. This behavior originates from the role of vorticity as an effective spin-dependent chemical potential that alters the available phase-space distribution for the emission process. In contrast, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>μ</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup></math> channel is more weakly affected by the rotational background, thus remaining dominated by its intrinsic mass threshold. The resulting channel dependence highlights a potential phenomenological handle for disentangling rotational effects in heavy-ion collisions: while light dilepton spectra encode the imprints of vorticity in the infrared sector, the muon channel provides a comparatively robust baseline.

Colombia

Jorge David Castaño-Yepes

Chile

Enrique Muñoz

Dilepton production in a rotating thermal medium: The rigid rotation approximation

We investigate the axial electromagnetic quasinormal modes of a static, asymptotically Anti–de Sitter (AdS) black hole sourced by a nonlinear electrodynamics model of Plebański type. Starting from the master equation governing axial perturbations, we impose ingoing boundary conditions at the event horizon and normalizable (Dirichlet) behavior at the AdS boundary. Following the approach of Jansen, we recast the radial equation into a linear generalized eigenvalue problem by using an ingoing Eddington–Finkelstein formulation, compactifying the radial domain, and regularizing the asymptotic coefficients. The resulting problem is solved using a Chebyshev–Lobatto pseudospectral discretization. We compute the fundamental quasinormal mode frequencies for both the purely electric ( $$Q_m=0$$ ) and purely magnetic ( $$Q_e=0$$ ) sectors, emphasizing the role of the nonlinearity parameter $$\beta $$ and the effective charge magnitude $\textit{Q}$. Our results show that increasing the nonlinear coupling $$\beta $$ and, more generally, increasing the charge magnitude $\textit{Q}$, tends to raise the oscillation frequency $$\omega _R$$ and typically enhances the damping rate $$-\omega _I$$ , leading to faster but more rapidly decaying ringdown profiles. Nonlinear electrodynamics breaks the electric–magnetic spectral degeneracy: magnetic modes are systematically less oscillatory and more weakly damped than their electric counterparts. For sufficiently large $$\beta $$ and small $$Q_m$$ , the fundamental mode becomes purely imaginary ( $$\omega _R \approx 0$$ ), consistent with the disappearance of the trapping barrier in this regime. These findings reveal qualitative signatures of nonlinear electromagnetic effects on black hole perturbations and may provide useful theoretical insight into strong-field or high-charge astrophysical environments.

Mohsen Fathi

Ariel Guzmán

J. Villanueva

Quasinormal modes of a static black hole in nonlinear electrodynamics

Recent findings from the Dark Energy Spectroscopic Instrument (DESI), when combined with supernova observations and CMB measurements, provide indications of a time-evolving dark energy component, with possible hints of phantom-like behavior in the recent past. Motivated by these developments, we investigate late-time cosmic acceleration within a cosmography-inspired framework based on the jerk parameter. Instead of adopting a phenomenological parametrization of the dark energy equation of state, we reformulate the differential equation defining the jerk into a class of integrable anharmonic oscillator equations through a specific closure ansatz. This procedure selects a restricted but analytically solvable subclass of cosmographic evolutions, leading to a closed-form expression for the dark energy equation of state governed effectively by a single parameter. Using DESI-DR2 BAO data, supernova data, and a compressed Planck likelihood, we constrain the cosmological parameters and find deviations from a cosmological constant at late times. Within this integrable model class, we do not find evidence of phantom barrier crossing. Further we show, using a dynamical systems approach, that $$w_{DE} = -1$$ corresponds to a generic bifurcation point, which prevents crossing within cosmographic framework.

Thailand

Nandan Roy

India

Soumya Chakrabarti

Is phantom barrier crossing inevitable? A cosmographic analysis

We investigate the connection between entanglement entropy and the notion of irreversibility in the renormalization-group flow in the context of a simple theory for which an explicit calculation from first principles is feasible. The change of the entanglement entropy for a spherical entangling surface as its radius grows from zero to infinity corresponds to the flow from the UV to the IR. Through analytical and numerical means, we compute the entanglement entropy for a free massive scalar theory, making use of the method of correlation functions. We deduce a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi></math>-function in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mo>+</mo><mn>1</mn></math> dimensions and an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi></math>-function in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mo>+</mo><mn>1</mn></math> dimensions. Both functions are monotonic and vary continuously between one and zero, which are the expected values for this theory.

Greece

Konstantinos Boutivas

Dimitrios Katsinis

Georgios Pastras

Nikolaos Tetradis

Computing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi></math>- and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi></math>-functions from entanglement

We propose a cogenesis scenario in which both the baryon asymmetry and dark matter abundance originate from the kinetic misalignment of the QCD axion. The framework unifies the Peccei-Quinn (PQ) mechanism with a type I seesaw sector, where Hubble-induced masses and higher-dimensional PQ-violating operators drive early time axion rotation. Working within the Dine-Fischler-Srednicki-Zhitnitsky axion model augmented by heavy neutrinos, we identify the parametric window of right-handed neutrino masses, determined by its decay rate, and the range of Hubble scales compatible with successful cogenesis, while maintaining the axion solution to the strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> problem and satisfying current limits on axion isocurvature perturbations. Our results establish kinetic misalignment as a robust and predictive mechanism for the QCD-axion cogenesis, leading to correlated constraints on the right-handed neutrino mass and the inflation scale for an axion decay constant within the viable range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>f</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mn>12</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>.

South Korea

Eung Jin Chun

Spontaneous cogenesis by the QCD axion in a type I seesaw mechanism

We analyze the effective couplings of a light, spinless, gauge-singlet particle $\textit{ϕ}$ to on-shell photons. Starting from the most general theory at the electroweak scale, which allows for CP-violating interactions suppressed by inverse powers of an ultraviolet scale Λ, we derive the corresponding low-energy effective theory valid below the GeV scale. Within this framework, we systematically expand the effective couplings of $\textit{ϕ}$ to on-shell photons in powers of small parameters. Working at the one-loop level, we retain terms at first order in 1$\textit{/}$Λ. We incorporate both isospin-breaking effects and $\textit{η}$–$\textit{η′}$ mixing, and provide explicit expressions for the couplings up to first order in $$ {m}_{\phi}^2/{m}_{\eta}^2 $$ and $$ {m}_{\pi}^2/{m}_{\eta}^2 $$ . As applications, we compute the decay rate of $\textit{ϕ}$ into two photons and illustrate our results in several physically motivated scenarios.

Italy

Ferruccio Feruglio

Switzerland

Gabriele Levati

Germany

Robert Ziegler

On the decay of a light spinless particle into two photons

A covariant implementation of diffeomorphisms in the presence of local symmetries is a nontrivial aspect of gravitational theories. In Double Field Theory, this is achieved through the so-called generalized Kosmann derivative. In this work, we show that the generalized Kosmann derivative admits a natural formulation entirely in terms of generalized fluxes through the inclusion of a compensating term that plays the role of a generalized momentum map, yielding a fully determined and covariant operator that provides a covariant realization of generalized diffeomorphisms. When parameterized in terms of the field content of heterotic supergravity, the resulting symmetry transformations give rise to momentum maps at the supergravity level, offering a duality-covariant interpretation of these objects. This framework provides a natural setting for the construction of conserved currents and Noether charges in doubled geometry with internal symmetries, with direct implications for black hole thermodynamics and its higher-derivative corrections in a duality-covariant setting.

Romina Ballesteros

Poland

Eric Lescano

Argentina

Jesús Rodríguez

Kosmann derivative and momentum maps from a duality covariant framework

We provide a detailed derivation of the Schwarzian modes in the full geometry of the Bañados-Teitelboim-Zanelli (BTZ) black hole at finite temperature, establishing the precise conditions under which they emerge from the general solution, thereby clarifying the absence of rotational modes in the full geometry. In addition, we demonstrate that the same modes can be recovered through a purely geometric Kerr-Schild construction. This equivalent approach offers a new geometric understanding of the Schwarzian sector and highlights the correspondence between perturbative and pure geometric approaches, additionally it provides a connection with double copy.

Lucas Acito

Matías Sempé

From BTZ perturbations to Schwarzian modes: a geometrical and perturbative analysis

We consider Loryons, particles beyond the Standard Model that receive a significant fraction of their masses from electroweak symmetry breaking, in the context of a two Higgs doublet model. Using scalar Loryons in the [1, 1], [1, 3] (as well as the equivalent [3, 1]) and the [2, 2] representations of the custodial SU(2) × SU(2) global symmetry as benchmarks, we study the constraints on the Loryon parameter space, focusing on unitarity, Higgs decay observables, and the absence of Loryon vacuum expectation values. We find that while neutral singlet Loryons remain viable for masses up to 700 GeV, representations containing charged scalars are severely constrained by LHC data, particularly as the fraction of mass generated by symmetry breaking increases.

United States

Can Kilic

Sanjay Mathai

Taewook Youn

Constraints on Loryons in a two Higgs doublet model

The rapid cooling of the neutron star in Cassiopeia A is speculated to arise from an enhanced neutrino emission caused by the onset of 3 <italic>P</italic> <inf>2</inf>-wave neutron superfluidity in the core. However, the neutrino emissivity due to Cooper-pair breaking and formation is in tension with the requirements for explaining the observed cooling rate. Here, we show that such a rapid cooling can be explained once the non-Fermi liquid behavior of the non-superfluid neutron liquid induced by superfluid quantum criticality is included into the theoretical description of neutron star cooling, without assuming the existence of additional energy loss processes. Our results indicate that the neutron star in Cassiopeia A remains in the thermal relaxation stage, which is greatly prolonged by the non-Fermi liquid behavior. The good agreement between our theoretical results and recent observational cooling data points to the pivotal role played by superfluid quantum criticality in neutron stars.

China

Hao-Fu Zhu

Guo-Zhu Liu

Xufen Wu

Rapid cooling of the Cassiopeia A neutron star due to superfluid quantum criticality