Near-threshold structures have been observed in the cross sections for $$e^+e^-\rightarrow p\bar{p}$$ , $$e^+e^-\rightarrow n\bar{n}$$ , and several non-baryonic final states in the vicinity of the $$N\bar{N}$$ thresholds. We investigate whether these structures can be understood as manifestations of a common $$N\bar{N}$$ final-state interaction. The strong $$N\bar{N}$$ interaction is taken from the chiral EFT description of the coupled $${}^3S_1$$ - $${}^3D_1$$ system constrained by low-energy $$N\bar{N}$$ scattering data. With this interaction fixed, the $$p\bar{p}$$ and $$n\bar{n}$$ cross sections are described by fitting only short-distance electromagnetic production sources, which are assumed to vary slowly over the near-threshold region. The resulting $$N\bar{N}$$ production amplitudes are then used as input for five inelastic hadronic channels. A simultaneous description of the near-threshold cross sections is obtained, indicating that the observed structures can be consistently interpreted as consequences of the same underlying $$N\bar{N}$$ dynamics, without introducing separate narrow resonances in individual channels.

Germany

Teng Ji

China

Ulf-G. Meißner

Understanding the near-threshold structures in $$e^+e^-$$ annihilation from a unified $$N\bar{N}$$ -interaction perspective

We investigate cosmological diffusion models in unimodular gravity within a dynamical systems reconstruction framework. By treating the logarithmic slope of the diffusion sector as an invertible dynamical variable, the diffusion function can be systematically reconstructed from the phase-space structure of the cosmological evolution. Under these conditions, we determine the physically admissible fixed points of the system, identifying novel matter–diffusion scaling solutions associated with power-law diffusion sectors, as well as purely diffusion-dominated configurations capable of driving late-time accelerated expansion without requiring an explicit cosmological constant term. The local behavior around the fixed points is then extended to the full cosmological evolution, providing a framework to explore the global implications of diffusion cosmologies. Beyond the asymptotic fixed-point structure, we further develop a reconstruction formalism based on the dynamical evolution of the diffusion slope, allowing for trajectories interpolating between different diffusion regimes during the cosmic history. Our results establish a systematic framework for constructing and classifying viable diffusion cosmologies in unimodular gravity directly from the phase-space dynamics.

Chile

Gabriel Gómez

Guillermo Palma

Norman Cruz

Unimodular gravity with arbitrary diffusion function: a dynamical system reconstruction approach

<p>We study flavor-violating decays of the SM-like Higgs boson and rare top decays in the type 1B realization of the flavorful two-Higgs-doublet model with a twist, focusing on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>s</mi><mi>b</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>d</mi><mi>b</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>u</mi><mi>c</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>μ</mi><mi>τ</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>e</mi><mi>τ</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>e</mi><mi>μ</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mo stretchy="false">→</mo><mi>c</mi><mi>h</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mo stretchy="false">→</mo><mi>u</mi><mi>h</mi></math>. We present the relevant amplitude and branching-ratio formulae, include one-loop vertex corrections, and impose constraints from Higgs signal-strength measurements, electroweak precision tests, meson mixing, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">→</mo><msub><mi>X</mi><mi>s</mi></msub><mi>γ</mi></math>, direct HFV searches, and CLFV constraints, including <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo>−</mo><mi>e</mi></math> conversion. The surviving parameter space favors <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>BR</mi><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>s</mi><mi>b</mi><mo stretchy="false">)</mo><mo>≫</mo><mspace linebreak="goodbreak"></mspace><mi>BR</mi><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>d</mi><mi>b</mi><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>BR</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">→</mo><mi>c</mi><mi>h</mi><mo stretchy="false">)</mo><mo>≫</mo><mi>BR</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">→</mo><mi>u</mi><mi>h</mi><mo stretchy="false">)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>BR</mi><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>μ</mi><mi>τ</mi><mo stretchy="false">)</mo><mo>≫</mo><mi>BR</mi><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>e</mi><mi>τ</mi><mo stretchy="false">)</mo><mo>∼</mo><mi>BR</mi><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>e</mi><mi>μ</mi><mo stretchy="false">)</mo></math> in the lepton sector. One-loop effects usually preserve these hierarchies, but can modify individual channels through different mechanisms: sizable destructive tree-loop interference can reduce <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi>s</mi><mi>b</mi></math> enough to yield rare <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>BR</mi><mrow><mn>1</mn><mi mathvariant="normal">L</mi></mrow></msub><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>d</mi><mi>b</mi><mo stretchy="false">)</mo><mo>&gt;</mo><msub><mi>BR</mi><mrow><mn>1</mn><mi mathvariant="normal">L</mi></mrow></msub><mo stretchy="false">(</mo><mi>h</mi><mo stretchy="false">→</mo><mi>s</mi><mi>b</mi><mo stretchy="false">)</mo></math> points, whereas the large relative corrections found in rare top decays mainly reflect strong SM-like alignment suppressing the tree-level amplitudes.</p>

Ti-Bin Hou

Zheng Li

Yu-Ju Peng

Jin-Lei Yang

Hao-Ran Ma

Tai-Fu Feng

Flavor-violating Higgs and top decays in the type 1B flavorful two-Higgs-doublet model with a twist

We study a dark photon dark matter scenario associated with a gauged <italic>U</italic>(1) <inf><italic>X</italic></inf> symmetry, stabilized by a dark parity that forbids kinetic mixing with the Standard Model. The leading interactions between the dark photon dark matter and the Standard Model arise from dimension-six Higgs-portal operators. In previous work, we found that for the parity-violating operator, the dark matter annihilation process is <italic>p</italic>-wave suppressed, naturally evading stringent direct-detection constraints while reproducing the observed relic abundance through thermal freeze-out. For a cutoff scale of 1&#8201;TeV, a dark matter mass of around 400&#8201;GeV is favored to realize the observed relic abundance. This scenario predicts cosmic-ray signals, in particular in the <math altimg='si15.svg'><mrow><msup><mi>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>&#8722;</mo></msup></mrow></math> channel, which can be targeted by indirect-detection experiments. Recently, a halo-like gamma-ray excess has been reported by Totani. Assuming a Navarro&#8211;Frenk&#8211;White <math altimg='si16.svg'><mrow><mo>&#8722;</mo><msup><mi>&#961;</mi><mn>2</mn></msup></mrow></math> morphology for the dark matter distribution, a dark matter mass of 420&#8201;GeV is favored for the <math altimg='si15.svg'><mrow><msup><mi>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>&#8722;</mo></msup></mrow></math> final state. Motivated by this excess, we consider the present dark photon dark matter framework augmented by a CP-even sub-GeV scalar mediator, which couples to the dark photon mass operator in order to enhance the present-day annihilation rate in the Galactic halo while inducing only an <math altimg='si17.svg'><mrow><mi mathvariant='script'>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow></math> correction at freeze-out. The exchange of this scalar induces a long-range attractive force, leading to Sommerfeld enhancement of the annihilation rate. The enhancement is saturating in dwarf spheroidal galaxies and the annihilation rate is dropping as <italic>p</italic>-wave remaining consistent with constraints from dwarf galaxies and cosmology.

Japan

Kimiko Yamashita

Higgs-portal spin-1 dark matter with parity-violating interaction for a galactic halo gamma ray excess

The Schwinger model is perhaps the simplest non-trivial exactly-solvable QFT. In this note we examine the perturbative structure of the theory on the sphere and provide evidence that its quantum corrections match those predicted by the expansion of the exact solution.

United Kingdom

Joseph Smith

A note on the perturbative expansion of the Schwinger model on $\textit{S}$ 2

In this paper we propose 4d and 3d dualities among special unitary gauge theories with fundamentals and antisymmetric flavors and symplectic or orthogonal gauge theories with fundamentals and two index tensor matter. The various dualities originate from a conjectured 4d self-duality for $\textit{SU}$($\textit{N}$) with an antisymmetric and four fundamental flavors. While we provide strong consinstency checks of such self duality for $\textit{SU}$(4), we focus on baryonic deformations for the cases at higher ranks. The deformations give rise to RG flows, deforming the self duality into new types of dualities, involving $\textit{SU}$($\textit{N}$) and $\textit{USp}$(2$\textit{M}$) gauge theories, where the precise value of $\textit{M}$ depends on the baryonic deformation. We provide strong evidence on the validity of these dualities, by proving the integral identities among their superconformal index. By dimensional reduction on a circle, real mass flows and other deformations we then find a rich set of new dualities in 3d. These dualities are first conjectured from localization, by the application of the duplication formula for the one loop determinants of the matter fields, and then they are checked by using the tensor deconfinement technique.

Italy

Antonio Amariti

Fabio Mantegazza

Simone Rota

Andrea Zanetti

A – BCD dualities

We analyze a one parameter static spherical deformation of Schwarzschild containing an <math altimg='si18.svg'><msup><mi>r</mi><mrow><mo>&#8722;</mo><mn>3</mn></mrow></msup></math> term. This term is treated as a quantum motivated effective template rather than a unique microscopic prediction, while the factor 256 <italic>&#960;</italic> in the alternative parameter <italic>&#951;</italic> is identified as a normalization convention. From the same geometry we derive the horizon, photon sphere, critical impact parameter, timelike circular orbit, ISCO, radiative efficiency, and epicyclic frequency diagnostics. Mapping the fiducial 68 percent EHT Sgr A* shadow size intervals yields <math altimg='si35.svg'><mrow><mo>&#8722;</mo><mn>1</mn><mo>&#8804;</mo><mi>&#967;</mi><mo>&#8804;</mo><mn>0.863</mn></mrow></math> for the Keck calibration and <math altimg='si36.svg'><mrow><mo>&#8722;</mo><mn>1</mn><mo>&#8804;</mo><mi>&#967;</mi><mo>&#8804;</mo><mn>0.156</mn></mrow></math> for the VLTI calibration. The screen polarimetric construction is used only as a fiducial tangential reference on the critical curve. At small deformation, comparison with the leading conservative Schwarzschild self force gives equal ISCO frequency shifts at | <italic>&#967;</italic>|&#8239;&#8771;&#8239;3.70 <italic>q</italic>; under genuinely Planck suppressed matching, however, the geometric shift is negligible relative to self force for astrophysical extreme mass ratio systems. The correlated null and timelike observables define a falsifiable metric level diagnostic.

Iran

K. Ghaderi

India

Anirudh Pradhan

Saudi Arabia

M. Zeyauddin

Testing a quantum motivated effective black hole geometry with photon ring and orbital diagnostics

We investigate the interface between quantum mechanics and gravity employing techniques from quantum information theory. The focus is primarily on investigating the gravitationally mediated entanglement (measured here by the concurrence) between two probe qubits created by two-level atoms with a reservoir consisting of thermally equilibrated homogeneous three-dimensional Bose-Einstein condensates. Our results demonstrate that below a certain temperature, the gravitational contribution to the qubit-reservoir interaction may strongly modify their coherence and entanglement dynamics even at large interqubit distance. By analyzing multi-parameter estimation techniques such as the quantum Fisher information, and quantum signal-to-noise ratio as a metric for certifying quantum effects and sensing performance, we show that the spatial separation between qubits and gravitational interaction may enhance estimation efficiency, providing a high-precision quantum gravity sensor.

Algeria

Abdelâali Boudjemâa

Asma Tahar Taiba

Testing quantum gravity with cold atoms: A quantum-information method

We consider Bianchi IX dynamics of a Universe filled with a massless phantom field. Such an exotic matter source enables regimes impossible in vacuum or with a standard scalar field. In particular, two Kasner indices of BKL oscillations can be simultaneously negative, and the absolute value of a negative index can be large. We describe the consequences of these features and explain the nature of volume oscillations recently discovered in such a system by numerical methods.

Egypt

Adel Awad

Russia

Dmitry Chirkov

Alexey Golovnev

Alexey Toporensky

Bianchi IX dynamics with a phantom field

<p>We propose a simple yet testable framework for light fermion dark matter (DM) with mass in the MeV–GeV range, charged under a dark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>D</mi></msub></math> gauge symmetry. Before symmetry-breaking, DM annihilates excessively into massless dark gauge bosons, resulting in an underabundant relic and hence creating severe tension with cosmic microwave background (CMB) and indirect detection constraints. This is naturally remedied by a strong first-order phase transition (FOPT) in the dark sector, triggered by a scalar field <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Φ</mi></math>, which gives rise to masses for the dark gauge boson (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>X</mi><mi>D</mi></msub></math>) and the physical scalar (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math>). To achieve the correct relic abundance while evading indirect detection constraints, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>s</mi></math>-wave annihilation channel <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mover accent="true"><mi>χ</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">→</mo><msub><mi>X</mi><mi>D</mi></msub><mi>ϕ</mi></math> is strictly maintained in the kinematically forbidden regime. Crucially, due to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>D</mi></msub></math> gauge structure, the usual <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>χ</mi><mover accent="true"><mrow><mi>χ</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover><mo stretchy="false">→</mo><mi>ϕ</mi><mi>ϕ</mi></mrow></math> annihilation is strictly absent at tree level and only arises at the one-loop level. Within this framework, we explore two distinct possibilities. When the loop-induced <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mover accent="true"><mi>χ</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">→</mo><mi>ϕ</mi><mi>ϕ</mi></math> channel is also kinematically forbidden, it predominantly determines the relic density. Conversely, when the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mover accent="true"><mi>χ</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">→</mo><mi>ϕ</mi><mi>ϕ</mi></math> channel is kinematically allowed, a rich interplay emerges between the tree-level forbidden <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mover accent="true"><mi>χ</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">→</mo><msub><mi>X</mi><mi>D</mi></msub><mi>ϕ</mi></math> process and the loop-level allowed <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mover accent="true"><mi>χ</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">→</mo><mi>ϕ</mi><mi>ϕ</mi></math> process, with the dominant contribution being dictated sensitively by the DM mass and gauge coupling. The late-time annihilations are highly suppressed in both of these channels, either by the energetic threshold of the forbidden channel or the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math>-wave velocity suppression of the loop-induced <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mover accent="true"><mi>χ</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">→</mo><mi>ϕ</mi><mi>ϕ</mi></math> final-state process, rendering the scenario entirely safe from CMB and indirect search bounds. Moreover, the same symmetry-breaking phase transition is strongly first-order, producing a stochastic gravitational-wave background that could be probed by upcoming space-based interferometers and pulsar timing arrays. We demonstrate that achieving the observed DM abundance tightly correlates the DM mass with the nucleation temperature of the phase transition. Thus, this setup links the DM relic abundance, dark-sector dynamics, and gravitational-wave signals, offering complementary paths to discovery in both terrestrial and cosmological observations.</p>

Satyabrata Mahapatra

Partha Kumar Paul

Narendra Sahu

Forbidden dark matter assisted by a first-order phase transition and the associated gravitational waves