We consider quantum decoherence and entropy increase in early universe cosmology. We first study decoherence in a discrete bipartite quantum system for which a single qubit gets entangled with an environment and the entropy increase is correlated with the decay of the off-diagonal terms of the reduced density matrix. We compare this system with continuous systems relevant for cosmology for which there is a natural external intervention, corresponding to the time-dependent separation between the sub- and super-horizon infla-tionary fluctuations. We find, in this case, that the off-diagonal terms of the density matrix, in a field basis, do not decay as sometimes assumed in cosmological set-ups. Nevertheless, following a recent treatment in terms of open Effective Field Theories (EFTs), we compute the entanglement entropy for a Gaussian state and show that it actually increases monotonically ( $$\dot{S}&gt;0$$ ) during the accelerated phases ( $$\ddot{a}&gt;0$$ with $\textit{a}$($\textit{t}$) the scale factor). We generalise this result to include non-Gaussian states and briefly discuss the relevance of computing the von Neumann entropy as compared to the thermodynamic entropy.

United Kingdom

Chile

Sebastián Céspedes

United States

Senarath Alwis

not found

Fernando Quevedo

Cosmology, decoherence and the second law

We construct the 𝒩 = 4 supersymmetric completion of the recently proposed single-minus gluon amplitudes in (2$\textit{,}$ 2) signature, which are nonvanishing for all multiplicities on a half-collinear kinematic locus. The superamplitude factorises into a permutation-invariant measure ∆ with uniform little-group weight that imposes the half-collinearity constraint, a piecewise constant stripped amplitude $${\widetilde{A}}_{1\dots n}$$ that is helicity blind and dual conformal invariant, and (super)momentum conservation delta functions. For $\textit{n}$ = 3, our superamplitude reduces to the known $$\overline{\text{M}\text{H}\text{V} }$$ superamplitude. We prove dual superconformal covariance of the $\textit{n}$-point superamplitude, and further analyse the Gr($\textit{k, n}$) Grassmannian integral at $\textit{k}$ = 1. Finally, we present the corresponding single-minus superamplitude in 𝒩 = 8 supergravity.

Andreas Brandhuber

Paolo Pichini

Gabriele Travaglini

Congkao Wen

𝒩 = 4 single-minus superamplitudes and dual superconformal symmetry

We approach a systematic investigation of the one-loop mass corrections to (super-)string massive higher-spin states. While the imaginary part of the relevant amplitudes is finite, being related to the width of the decay of the states into two lower-mass states at tree level, the real part is generally IR-divergent and needs regularization and renormalization. We mostly focus on states of the first Regge trajectory in the NS-NS sector of Type-II string theories. We explicitly derive a closed-form expression for the integral over the insertion point, relying on properties of elliptic functions and lattice sums. We then regularize the IR divergent integral over the modular parameter of the torus, applying the $\textit{iε}$-prescription in string theory. As a result we compute the desired mass corrections up to level $\textit{N}$ = 10 and analyze their behavior at increasing $\textit{N}$. Finally, we speculate on the existence of mixing among lower-spin states and conjecture that the one-loop mass matrix be governed by some random matrix theory.

Italy

Massimo Bianchi

China

Maurizio Firrotta

Lorenzo Grimaldi

One-loop mass corrections and decay widths of Type II heavy string states

Understanding flux string dynamics can provide insight into quark confinement and hadronization. First-principles quantum and numerical simulations have mostly focused on toy-model Abelian lattice gauge theories (LGTs). With the advent of state-of-the-art quantum simulation experiments, it is timely to study string dynamics in non-Abelian LGTs beyond one spatial dimension. Using tensor network methods, we simulate the real-time string dynamics of a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mo>+</mo><mn>1</mn><mi mathvariant="normal">D</mi></mrow></math> SU(2) Yang-Mills LGT with dynamical matter. In the strong-coupling regime and at resonance, string breaking occurs via a sharp Casimir reduction, along with meson and baryon-antibaryon formation, a distinctively non-Abelian feature. At finite baryon density, we discover a baryon blockade mechanism that delays string breaking. Away from resonance, the magnetic term drives purely non-Abelian fluctuations: glueball-like excitations and self-crossed strings that resolve two SU(2) intertwiners with distinct dynamics. For higher-energy strings, we uncover representation-dependent tension-reduction resonances. Our findings serve as a guide for upcoming quantum simulators of non-Abelian LGTs.

Germany

Giovanni Cataldi

Simone Orlando

South Korea

Jad C. Halimeh

Real-Time String Dynamics in a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mo>+</mo><mn>1</mn><mi mathvariant="normal">D</mi></mrow></math> Non-Abelian Lattice Gauge Theory: String Breaking, Glueball Formation, Baryon Blockade, and Tension Reduction

In the present study, we extend our previous analysis of the proton electromagnetic form factors (FFs) extracted from exclusive photon leptoproduction (EP) measurements in kinematic regions where the Bethe-Heitler (BH) process dominates the cross section by including all currently available high-precision EP data from CLAS and Hall A Collaborations. Using the same phenomenological framework, we investigate the consistency among the different datasets, determine the proton electromagnetic FFs within several fitting scenarios, and extract the corresponding charge and magnetic radii. A significant tension is found between the CLAS 2018 measurements and the remaining EP data, with the low-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>t</mi><mo stretchy="false">|</mo></math> region playing a dominant role in this tension. We systematically investigate this behavior through <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>t</mi><mo stretchy="false">|</mo></math>-cut scans and assess its impact on the extracted FFs and radii. For all analyses, the extracted proton charge radius is smaller than the Particle Data Group average and most determinations based on elastic electron-proton scattering. However, the results are consistent, within uncertainties, with the PRad measurement and muonic hydrogen spectroscopy. In contrast, the magnetic radius is found to be compatible with the current world average. These results demonstrate that BH-dominated EP measurements provide an independent and complementary approach to determine the electromagnetic structure of the proton and offer additional support for the small-radius solution of the proton charge-radius puzzle.

Iran

Muhammad Goharipour

Anoushiravan Moradi

Türkiye

K. Azizi

Implications of exclusive photon leptoproduction measurements for the proton charge-radius puzzle

We explore the properties of quark stars by combining the microscopic axion-extended Polyakov–Nambu–Jona-Lasinio model with the macroscopic framework of four-dimensional Einstein–Gauss–Bonnet (4D EGB) gravity. Specifically, axion effects are incorporated through the background phase $$\theta =a/f_a$$ in the thermodynamics of quark matter. Our results show that the inclusion of axion-induced interactions stiffens the quark-matter equation of state, thereby increasing the sound speed and the maximum mass of quark stars. The 4D EGB correction effectively weakens gravitational compression and further modifies the stellar structure, allowing for larger radii and higher maximum masses while reducing the compactness and the surface gravitational redshift. The combined effects can support quark stars above $$2\,M_\odot ,$$ with mass–radius sequences overlapping the observational regions in the indicative phenomenological comparison. These findings reveal that the interplay between axion-induced modifications of dense quark matter and 4D EGB gravity may provide a viable phenomenological framework for describing massive quark stars.

Rui Zhou

Ming-zheng-xuan Wu

Xin-ran Yang

Chong-long Xie

Min Zhou

Zhi-yang Liu

Shi-jun Mao

Guo-yun Shao

Effects of axion interactions on quark stars in 4D Einstein–Gauss–Bonnet gravity

Poland

Trambak Bhattacharyya

Maciej Rybczyński

Grzegorz Wilk

Zbigniew Włodarczyk

Addendum to “A harmonic oscillator in nonadditive statistics and a novel transverse momentum spectrum in high-energy collisions” [Phys. Lett. B 867 (2025) 139588]

We track the chain of dualities relating five-brane webs in Type IIB to M-theory on noncompact Calabi-Yau threefolds, and follow the effect of adding ($\textit{p}$, $\textit{q}$) seven-branes. T-dualizing along the seven-brane, a junction of D5-branes ending on a D7-brane becomes a single smooth D6-brane wrapping a smooth holomorphic curve, which uplifts directly to an M-theory geometry. Treating the branes as coherent sheaves (tachyon condensation), we obtain a spectral-curve dictionary that maps non-Abelian (T-brane) partition data to explicit complex-structure deformations of the threefold. As applications we (i) give a physical derivation of these deformations, (ii) exhibit a simple geometric prototype of an s-rule violation, and (iii) link T-brane data to geometry.

Belgium

Andrés Collinucci

M-theory geometries from five-brane webs, seven-branes, and T-branes

We introduce a family of polytopes—in-in zonotopes—whose boundary structure organizes the contributions to scalar equal-time correlators in flat space computed via the in-in formalism. We provide explicit Minkowski sum and facet descriptions of these polytopes, and show that their boundaries factorize into products of graphical zonotopes and lower-dimensional in-in zonotopes, thereby mimicking the factorization structure of the correlators themselves. Evaluating their canonical forms at the origin—equivalently, calculating the volume of the dual polytope—reproduces the correlator. Finally, in a simple example, we show that the wave function decomposition of the correlator corresponds to a subdivision of the dual polytope.

Ross Glew

Geometry of In-In Correlators

We present the first experimental search for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-naturalness tower of neutrinos using a global analysis of publicly available neutrino data. As a potential solution to the hierarchy problem, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-naturalness model employs a varying Higgs mass parameter among <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> dark sectors and encodes the required fine-tuning of the placement of the sectors in a parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math>. We report exclusion limits on the parameter space (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>), for normal and inverted ordering and in case the neutrino is Majorana or Dirac. In the case of a Majorana neutrino, we can rule out <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo>≤</mo><msup><mn>10</mn><mn>4</mn></msup></math> sectors with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi><mo>≥</mo><mn>0.1</mn></math>. This is particularly exciting as it shows that a gauge and gravitational unification around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>M</mi><mi>GUT</mi></msub></math>, which is a benchmark scenario of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-naturalness framework with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo>=</mo><msup><mn>10</mn><mn>4</mn></msup></math> without fine-tuning, is ruled out by neutrino experiments.

Sofia Lonardi

France

Manuel Ettengruber

Philipp Eller

Searching for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-naturalness tower of neutrinos