26 August 2026

We study the interaction between light and non-relativistic cosmic neutrino background (CNB). We propose single arm laser interferometry with coherent laser source and two distinct squeezing operators to probe such interaction. We analyze the induced phase shift in four distinct quantum regimes of the interferometer operation: the standard quantum limit (SQL), the Heisenberg limit, super-Heisenberg limit with $N^{3/2}$ enhancement, and super-Heisenberg limit with $N^{2}$ enhancement where $N$ is the number of photons in the interferometer. We demonstrate that the $N^{2}$ super-Heisenberg enhancement has the potential to probe the magnetic moment down to $10^{-25}\, μ_{B}$ where $ μ_{B}$ is the Bohr magneton. If the CNB and photons interact via its magnetic moment, this interaction could be revealed in single arm interferometer operating at super-Heisenberg limit with $N^{2}$ enhancement.

We study a six-dimensional SU(9) grand unified model with rank-reducing discrete boundary conditions and continuous Wilson line phases on the orbifold $T^2/\mathbb Z_4$. We show that the model can realize grand unification of the Standard Model gauge interactions and electroweak symmetry breaking via the Hosotani mechanism. The model has several attractive features. Two Higgs doublets arise as zero modes of the extra-dimensional components of the gauge field, and the leptons and quarks in each generation are separately embedded into two bulk multiplets, in the ${\bf 36}$ and ${\bf 84}$ representations of SU(9), respectively, without exotic matter. Furthermore, proton decay processes mediated by the gauge bosons in the bulk are absent, because the leptons and quarks belong to different bulk multiplets.

We study modulus stabilization by background fluxes. The supersymmetric minima satisfy a holomorphic quadratic equation. As concrete examples, we consider $T^6/(\mathbb{Z}_2\times\mathbb{Z}_2')$ orientifold model and a simple Calabi-Yau compactification. The modulus values show specific patterns. For example, they show the Farey sequence. The void structure appears around modulus vacua with high degeneracies. We find a correlation between the degeneracy and the void area. The modulus vacua are related by discrete Abelian symmetries generated by the Gauss composition law, which includes the CP symmetry. Spontaneous CP violation is also discussed.

A cosmological network of axion strings may exist in the Universe today. If axion-like particles couple to electromagnetism, such a network induces spatially varying birefringence in the polarization of the cosmic microwave background (CMB), which can be probed by current and next-generation CMB experiments. We calibrate a loop-crossing model against a large-scale adaptive-mesh-refinement (AMR) simulation of axion-string network dynamics in the early Universe and use the calibrated model to predict CMB birefringence from recombination to today. We find that the non-detection of anisotropic birefringence in CMB observations places a strong upper bound on the electromagnetic anomaly coefficient $\mathcal{A}$ that enters the axion-photon coupling $g_{aγγ} = - \mathcal{A} α_\mathrm{em} / πf_a$. A joint analysis of available anisotropic birefringence measurements constrains $|\mathcal{A}| < 0.24$ at 95% C.L., which is independent of the Peccei-Quinn scale $f_a$, assuming that the axions are hyperlight so that the network survives until today. This limit strongly restricts the high-energy embedding of hyperlight axions, excluding the minimal Grand Unified Theory prediction for the electromagnetic anomaly coefficient at high significance. In addition, we discuss the implications of an axion-string origin for the recently reported evidence of isotropic birefringence.

We study modular transformation formulas from the viewpoint of Mellin space. The basic observation is that the functional relation between the Hurwitz zeta function and the polylogarithm can be used to organize modular transformations as reflection identities of Mellin kernels, while the accompanying polynomial anomalies arise from contour deformations. We first illustrate this mechanism for the $q$-$θ$ function and then extend it to the elliptic Gamma function. In the latter case, independently Mellin transforming the two elliptic directions leads to a trilinear reflection identity relating the three elliptic Gamma functions appearing in the SL$(3,\mathbb{Z})$ modular formula, while the associated contour deformation reproduces the cubic Bernoulli polynomial. Further reflection formulas lead to a weighted $q$-Pochhammer type function with a modular transformation analogous to that of the $q$-$θ$ function, as well as a transposed trilinear reflection identity analogous to the Mellin space structure underlying the SL$(3,\mathbb{Z})$ transformation. Our results suggest that Mellin space reflection identities provide a useful organizing principle for constructing and studying modular special functions beyond the standard multiple elliptic Gamma hierarchy.

A decade ago, locally harmonic Maaß forms were first established by Bringmann, Kane, and Kohnen in negative weights and independently by Hövel in weight $0$. Since then, they have seen important applications related to twisted central $L$-values of newforms. However, there are just a few examples of these forms known so far, and in particular there is no unifying theory behind these examples. Towards this direction, we show that the representations of Zagier's $f_{k,D}$ and Mono's $g_{k+1,D}$ functions as traces of cycle integrals are not unique.

The ESS$ν$SB experiment aims to measure CP violation in the leptonic sector with high precision, necessitating robust reconstruction of neutrino events in the water Cherenkov (WC) detectors. In this work, we investigate the flavour identification potential of the proposed near WC detector using graph neural network (GNN)-based classification, with a focus on variations of key detector design parameters. In particular, we study whether a smaller and/or less instrumented detector can achieve the required classification performance. Using detailed Monte Carlo simulations of charged-current (CC) neutrino interactions, we train GNN classifiers to distinguish electron and muon neutrino CC events. We find that GNN-based classification remains accurate even for detector configurations with volumes up to a factor of eight smaller than the nominal design, with only moderate degradation in classification efficiency at fixed background rejection. The resulting loss in efficiency can largely be compensated by increased exposure time. Furthermore, we demonstrate that reduced photomultiplier tube (PMT) coverage in the nominal detector has a limited impact on classification performance, provided that coverage is maintained in regions of highest signal yield, in particular near the forward end-cap.

We evaluate the expected performance of a 170-ton water Cherenkov detector for reactor antineutrino--electron elastic scattering at the RENO near-detector site. The reactor-spectrum normalization is extracted from the reconstructed recoil-electron directional distribution using a constrained profile-likelihood fit for an exposure of 365.25 days. For the minimum prompt-hit multiplicity $N_{\mathrm{prompt}}\geq8$ scenario, which neglects PMT radioactivity, the total uncertainty on the reactor-spectrum normalization is ${}^{+1.08\%}_{-1.07\%}$. For the more restrictive $N_{\mathrm{prompt}}\geq20$ scenario, which includes the simulated PMT-radioactivity components, the total uncertainty is ${}^{+1.49\%}_{-1.47\%}$. These results demonstrate that directional information from a water Cherenkov detector can provide percent-level sensitivity to the reactor elastic-scattering normalization.

The starting point of the present work is the observation that the tangent group of a curved manifold need not have the same dimension as the manifold itself. We use this fact to construct Conformal Gravity and its noncommutative (Fuzzy) counterpart as gauge theories, and then to unify both with internal gauge interactions. Specifically, we present a scheme in which conformal gravity, based on gauging the SO(2,4) group, and fuzzy gravity, based on gauging the SO(1,5)$\times$U(1), are unified with SO(10) internal interactions through the parent group SO(2,16), and we work through the resulting spontaneous symmetry breakings and fermion content in detail. We also discuss the low-energy phenomenology of the scheme, including cosmic-string gravitational-wave signals, and close with a brief outlook: a candidate minimal unification group, a dark-matter candidate suggested by the construction, and the ghost problem common to higher-derivative gravity theories of this type.

We present the first direct lattice QCD determination of the $θ$-induced CP-violating pion-nucleon-nucleon coupling $\tilde g_{πNN}$. Using overlap valence fermions on three $2+1$-flavor domain-wall ensembles at a single lattice spacing, we calculate the forward proton matrix element of the isovector pseudoscalar density in the $θ$-vacuum to first order in $\barθ$. The parity-mixing effect in the external nucleon states is included in the extraction. The cluster-decomposition error-reduction method is used to improve the statistical precision. A simultaneous extrapolation in the valence- and sea-pion masses, with model averaging over 7 forms based on the Akaike information criterion, gives $\tilde g_{πNN}=0.0306(56)(124)\,\barθ$ at the physical point. The first uncertainty includes the statistical and matrix-element-fit systematic uncertainties, whereas the second reflects the spread among the extrapolation forms. Within these uncertainties, the result is consistent with the indirect determination based on the strong neutron-proton mass splitting. The present precision is limited primarily by the extrapolation from the relatively heavy sea-pion masses.