18 August 2026

We investigate 7-branes in type 0B string theory, motivated by the recent proposal of Baykara, Dudas, and Vafa, which connects type 0B string theory with M-theory. On the $Q$-symmetric branch, the self-duality group of type 0B string theory is $Γ_0(2)$, whose Abelianization is $\mathbb{Z}\times\mathbb{Z}_4$. This implies the existence of two independent 7-brane charges. We construct explicit charge operators in terms of modular forms and identify the corresponding charged objects in gravity solutions. One is the ordinary D7-brane, while the other is a 7-brane carrying a nontrivial $\mathbb{Z}_4$ charge. We further construct a compact background consisting of eight such $\mathbb{Z}_4$ 7-branes using a restricted Weierstrass model. Remarkably, in this background the axio-dilaton is fixed to the constant value $τ=(1+\mathsf{i})/2$, which coincides with the unstable de Sitter critical point proposed in the M-theory description of type 0B string theory. We also analyze fluctuations in the $Q$-odd sector and find that, although the corresponding equations of motion are globally well-defined in this background, the closed string tachyon remains unstable. Our results provide a concrete realization of new 7-branes in type 0B string theory and clarify their relation to its strong-coupling structure.

The angular structure and temporal variability of neutrino emission from binary neutron star mergers are characterized using fully general-relativistic simulations with energy-integrated M1 neutrino transport across a representative set of equations of state, total masses, and mass ratios. The angle-dependent neutrino energy flux is extracted on a spherical surface outside the remnant and decomposed into spherical harmonics to quantify its multipolar content and evolution. Following the initial post-merger transient, the neutrino radiation flux approaches an axisymmetric configuration dominated by a strong quadrupolar component, producing persistent polar flux enhancement and equatorial suppression due to torus shadowing. The dipolar contribution remains subdominant, indicating the absence of sustained one-sided emission. The degree of anisotropy increases with mass asymmetry and for softer equations of state, reflecting the compactness and morphology of the remnant--disk system. Superimposed on this time-averaged geometry, coherent azimuthal modulations associated with the $m=1$ mode are identified. Fourier analysis reveals a characteristic frequency of $\sim 0.6$--$0.7$ kHz, consistent with differential rotation in the remnant and inner disk layers, indicating a dynamical coupling between rotational structure and neutrino emission variability. Finally, we quantify how the same quadrupole-dominated radiation geometry induces a latitude-dependent equilibrium electron fraction. The polar material is driven close to the neutrino-equilibrium target, whereas equatorial material remains systematically more neutron-rich and below equilibrium.

Let $\mathcal{L}_n \subset \mathcal{M}_2$ be the locus of genus-two curves admitting a maximal degree-$n$ elliptic subcover, cut out in $\mathbb{P}(2,4,6,10)$ by an irreducible weighted-homogeneous polynomial $F_n \in \mathbb{Z}[J_2,J_4,J_6,J_{10}]$. Let $ν(n)$ be the degree of $X_1(n) \to X(1)$, let $G_{n^2}$ be the Siegel modular form of level one with divisor the Humbert surface $H_{n^2}$, and let $k(H_{n^2})$ be its weight. We prove that the meromorphic Siegel modular form $F_n(τ)$ obtained from $F_n$ has a pole of order exactly $ν(n)$ along the product locus, that $χ_{10}^{ν(n)} F_n(τ)$ is a constant multiple of $G_{n^2}$, and that $°_w F_n = k(H_{n^2}) - 10ν(n)$ for every $n \geq 2$, even or odd. We determine the restriction of $G_{n^2}$ to the product locus as an explicit product of modular polynomials and, for $n \geq 3$, its leading Fourier-Jacobi coefficient as a product of theta functions over the torsion points of exact order $n$, and we characterize $G_{n^2}$, up to scalar, as the unique form of its weight vanishing on a single torsion divisor. These data convert the computation of $F_n$ from elimination into a linear problem of the size the formula prescribes, which we carry out for $n=5$.

This is the first paper in a series on the Gromov-Witten theory of the universal abelian variety over the moduli space of principally polarized abelian varieties of dimension $h$. We conjecture that the generating series of Gromov-Witten classes, when summed over the degree against the principal polarization, is a cycle-valued quasimodular form for $\mathrm{SL}_2(\mathbb{Z})$ and satisfy a holomorphic anomaly equation. These conjectures generalize the quasimodularity of the Gromov-Witten theory of elliptic curves to higher dimension and raise interesting questions regarding enumerative mirror symmetry for abelian varieties. In genus $1$ it specializes to a conjecture of Greer and Lian which was proven by Iribar Lopez after tautological projection. We also discuss a special family of abelian varieties with a conjectural relation to Siegel quasimodular forms of higher genus. The main result of the paper is a proof of the conjectures in genus $2$ after tautological projection. For that we introduce quotient Gromov-Witten invariants which are indexed by the characteristic polynomial of the curve class and are shown to determine all descendent Gromov-Witten invariants satisfying a degree conditions. We then give an explicit formula for all genus $2$ quotient invariants after tautological projection as the Shimura lift of the product of two Eisenstein series. The formula is based on a curious modular identity derived in a joint appendix with Brandon Williams.

We study the sensitivity of the DUNE and T2HK long-baseline experiments to time reversal (T) violation in neutrino oscillations. Rather than the conventional approach of exchanging initial and final neutrino flavors, we search for T violation through the $L$-dependence of the $ν_μ\to ν_e$ transition probability at fixed neutrino energy using neutrino data only. Within the standard three-flavour framework, we show that the DUNE and T2HK together can establish the presence of an $L$-odd component in the oscillation probability at up to $\sim 4σ$ significance, with the optimal sensitivity in the energy range $E_ν\in [0.68, 0.92]$ GeV. The second oscillation maximum of DUNE plays a crucial role in this analysis. We further show that DUNE is more sensitive to T violation that is running in neutrino-only mode, whereas T2HK provides better sensitivity in the conventional neutrino versus anti-neutrino comparison, making the two experiments complementary to each other in search of the CP phase $δ_{\rm CP}$.

We present a study of charged-particle multiplicities and the kinematic distributions of muons, protons, and charged pions in a flux-integrated sample of charged-current inclusive $ν_μ$ interactions on water recorded with the NINJA nuclear emulsion detector exposed to the J-PARC $ν_μ$-focused beam. The data correspond to an exposure of $4.63\times10^{20}$ protons on target, with a neutrino energy spectrum peaked at 0.7 GeV. In this analysis, 82 events are selected from a fiducial water volume with a mass of 3.9 kg, corresponding to 5% of the total water target mass exposed during the run. The reconstructed distributions are compared with Monte Carlo predictions based on the interaction model used in the T2K experiment. The observed distributions are generally consistent with the predictions within the estimated uncertainties, although the proton angular distribution exhibits some tension with the prediction. The results are currently limited by statistical uncertainties. This analysis provides the first study of proton kinematics with sensitivity to proton momenta as low as 200 MeV/$c$ with a $ν_μ$-focused beam on a water target using nuclear emulsion data and establishes the analysis framework for future measurements with substantially larger NINJA data samples.

We present a novel method to analyze coherent elastic neutrino--nucleus scattering (CE$ν$NS) data to extract the reactor antineutrino spectrum below the inverse beta decay threshold of 1.8 MeV, where it remains unmeasured. Adapting halo-independent analysis techniques developed for direct dark matter detection, we show how to obtain a best-fit and a pointwise confidence band for the integrated neutrino flux, without assuming a parametric form or smoothness prior for the spectrum. In our approach, which follows from convex geometry arguments, the differential neutrino rate is written as a linear combination of Dirac delta functions -- a finite Dirac sum (FDS) -- with a maximum number of terms determined by the number of data points. We apply our ``FDS method'' to mock CE$ν$NS data for a low-threshold Ge detector and compare it with Tikhonov-regularized unfolding.

Aim : We investigate whether the ultra-high-energy neutrino KM3-230213A can be interpreted as a cosmogenic neutrino produced by ultra-high-energy cosmic rays (UHECRs) accelerated in the lobes of FRII radio galaxies. Method : We model the UHECR, cosmogenic neutrino and photon fluxes expected at Earth using a recent luminosity-dependent density evolution of radio galaxies, empirical relations between radio luminosity and jet kinetic power, and standard assumptions for the UHECR output of FRII lobes. The FRII contribution to the UHECR population is derived self-consistently from the observed luminosity function, rather than imposed as a fixed normalization. The propagation of UHECRs and the production of secondary particles are computed with well-established numerical tools. Results : The predicted cosmogenic neutrino flux is compatible with that inferred from the detection of KM3-230213A, while remaining consistent with current UHECR and gamma-ray constraints. According to our models, the full GRAND observatory ($200\,000~\rm km^2$) should detect between $\sim50$ and $\sim135$ neutrinos above $10^{17}$~eV in ten years, allowing the diffuse UHE neutrino spectrum to be characterized. In contrast, the detection of individual FRII sources or statistically significant correlations with FRII catalogs is likely to remain challenging. At the highest energies, UHECR composition and anisotropy measurements, in particular those related to the nearby radio galaxy Cygnus~A, should provide complementary tests of this scenario. More generally, progress will likely rely on the combination of multimessenger observations with improved astrophysical constraints on particle acceleration and jet composition in FRII radio galaxies.

A warped extra dimension in a five-dimensional (5D) anti de Sitter (AdS) background was introduced in 1999 by Lisa Randall and Raman Sundrum to solve the gauge hierarchy problem in particle physics. As a bonus, a holographic interpretation in terms of four dimensional (4D) conformal field theories (CFT) was found. Interestingly enough, another 5D background, the linear dilaton (LD), was found to have a holographic interpretation in terms of Little String Theory. In this review we will show how a set of 5D backgrounds, parametrized in terms of a real parameter $ν$, generalizes both theories and gives rise, in particular, to AdS for $ν=0$ and to LD for $ν=1$. Furthermore, working in the 5D theory, we will consider applications of the LD background to: i) Particle Physics, so that the 5D Planck scale can be lowered to sub-Planckian values, ii) Brane World Cosmology (BWC), based on the appearance of an extra vacuum characterized by a 5D black hole. In all cases we find a gapped continuum for bulk propagating fields, which makes connection with unparticles. In the case of BWC we also point out on the existence of a pressureless holographic fluid which could play the role of dark matter (DM), with feeble (gravitational) interactions to the Standard Model (SM), decoupled from the thermal SM bath, and generated by a freeze-in mechanism after inflation. We also point out the additional possibility of identifying DM with a long-lived feebly interacting massive graviton, as an isolated resonance generated by radiative corrections to the continuum graviton propagator self-energy.