17 September 2026

The recent LUX-ZEPLIN (LZ) search at high nuclear-recoil energies reported an intriguing candidate event near 250 keV, motivating interpretations in terms of inelastic dark matter. A simple realization with Higgsino dark matter, however, is strongly constrained by capture and subsequent annihilation in the Sun, which would produce a high-energy neutrino flux excluded by IceCube. We propose an asymmetric inelastic dark-matter scenario that naturally avoids this tension. The dark matter is a predominantly Standard-Model-singlet Dirac fermion that mixes weakly with a nearly degenerate electroweak doublet. Its primordial asymmetry is generated by CP-violating out-of-equilibrium decays of heavy Majorana fermions produced nonthermally from inflaton decays, while the symmetric component is efficiently depleted through dark-sector interactions. The absence of an appreciable antiparticle abundance then suppresses dark-matter annihilation in the Sun and eliminates the associated IceCube constraint. The singlet-doublet structure simultaneously yields an off-diagonal Z-boson coupling proportional to the mixing angle, whereas the diagonal coupling is suppressed by its square. Consequently, an observable inelastic scattering rate can coexist with stringent limits on elastic scattering. We find that the LZ event can be accommodated for dark-matter masses of a few hundred GeV to 1 TeV, with mass splittings of a few hundred keV and mixing angles below O$(10^{-2})$. Since the relic abundance is set by the primordial asymmetry rather than thermal freeze-out, lighter dark matter is also viable and can alleviate the potential tension with the absence of events in the LZ high-energy sideband. This framework predicts correlated elastic and inelastic direct-detection signals, together with complementary signatures at collider and precision experiments.

In Seesaw Cosmology, a scalar field reheats the Standard Model (SM) through right-handed neutrinos (RHNs), which generate tiny neutrino masses through the seesaw mechanism. When RHNs rapidly fill a restricted momentum-space region, expansion continually opens new fermionic states that are refilled by subsequent scalar decays, maintaining an approximately constant physical RHN density. This gives rise to a novel heating regime in which the SM temperature increases with the scale factor as $T \propto a^{+3/8}$, in sharp contrast to the conventional $T \propto a^{-3/8}$ scaling during matter-dominated reheating.

We propose a new source of neutrino decoherence arising from stochastic gravitational lensing by unresolved mass substructure. Unlike traditional models that treat the lensing potential as smooth and deterministic, we decompose the lensing potential into a smooth component and a stochastic population of compact clumps. The substructure induced fluctuations of the lensing potential generate stochastic corrections to the neutrino time delay, thereby producing random relative phases between different neutrino mass eigenstates. Averaging over the clump ensemble converts these phase fluctuations into an effective dampening of flavour coherence. This framework connects stochastic gravitational lensing with neutrino phenomenology and offers a novel route to probe dark matter substructure through astrophysical neutrino flavour transitions.

Magnetic monopoles are a generic prediction of Grand Unified Theories (GUTs) that are in tension with modern cosmological and observational bounds. In this paper, we calculate the present-day abundance of GUT monopoles produced thermally in the early Universe. We improve on previous calculations by accounting for full relativistic corrections to the thermal abundance and enhanced monopole annihilation due to the emission of radiation and scattering off massive gauge bosons, the Standard Model fermions and their superpartners. To obtain a present-day energy density less than that of dark matter, we show that the reheating temperature of the Universe, $T_{\rm RH}$, must be less than $0.55$ times the GUT symmetry breaking scale $T_{\rm GUT}$ for the canonical 't Hooft-Polyakov monopole mass. Accounting for Parker bounds on the present-day magnetic monopole abundance, the bound is tightened to $T_{\text{RH}}/T_{\text{GUT}} \lesssim 0.45$. Furthermore, experimental bounds from Super-Kamiokande require $T_{\text{RH}}/T_{\text{GUT}} \lesssim 0.35$ in our scenario.

We investigate the geometry of the Fermion mixing matrix in the Standard Model. The principal structure studied is the CKM matrix, $V$, viewed as an element of the double coset space $M$, where $M=T\backslash SU(3)/T$, and $T=U(1)\times U(1)$. The space $M$ is given a Riemannian metric, and has both point singularities, which it is shown correspond to the known renormalization group fixed points, and line singularities connecting the fixed points. A key discrete object inducing many of these properties is the Weyl group, $W$, of $SU(3)$, $W$ being the symmetric group $S_3$, which appears in the guise of the vertices of a hexagon in $V$.

In this paper, for $N=8,12,16,20,32$, we determine the explicit structure of the graded algebra of modular forms for $\varGamma_0(N)$ of both integral and half-integral weights, with all quadratic Dirichlet characters modulo $N$. We give explicit eta quotient generators and determine the relations among them. Using these structures, for a given weight, a level among those considered above, and a quadratic character, we obtain a basis for the corresponding space of modular forms consisting of eta quotients. Using these eta quotient bases, we obtain necessary and sufficient conditions for the periodicity of the signs of the Fourier coefficients of modular forms in three specific spaces. Finally, we determine all eta quotients in these spaces whose Fourier coefficient signs are periodic.

For sixty years, the Sun served neutrino physics more than the reverse: its neutrinos established oscillations rather than probing the star itself. That is now changing. Reactor antineutrinos have pinned down the oscillation parameters governing solar-neutrino flavour conversion so precisely that the propagation-related uncertainty is becoming negligible -- closing the first of two abysses. Solar neutrinos can, at last, be turned on the Sun. Yet a second abyss remains: today's solar-neutrino detection falls an order of magnitude short of the precision the Standard Solar Model already predicts for the dominant pp flux ($>\,$90$\%$) -- a gap no reactor experiment can close. The intrinsic $^{14}\mathrm{C}$ background walls off the pp region; only new detection techniques can breach it. Bridging this second abyss demands a revolution, not an increment. Combined with helioseismology's complementary reading of the Sun's mechanical structure, precision neutrino measurements of the nuclear source terms would enable a multi-messenger heliotomography of the solar interior -- reading our star from both sides at once. A new age of solar discoveries may follow, on one condition: that the field builds the instruments equal to the task.

The detection of the Diffuse Supernova Neutrino Background (DSNB) is one of the main goals of the current and the next generation of neutrino experiments. Based on results published by the Super-Kamiokande (SK) collaboration, we study the sensitivity of current and future water Cherenkov detectors to the DSNB. We reproduce current constraints and estimate the sensitivity to the DSNB of ten years of SK data and of a next-generation water-Cherenkov detector like Hyper-Kamiokande (HK). We find that, even with increased exposure, SK's sensitivity is relatively modest, while HK has the potential to deliver a statistically significant discovery of the DSNB in ten years. Along the way, we perform a detailed study of the relevant atmospheric neutrino backgrounds and argue that an accurate treatment of neutrino oscillations and propagation is essential when it comes to properly inferring the sensitivity to the DSNB and measuring its flux.

Effective infrared two-sheeted descriptions of fermion mixing between braneworlds have emerged in several distinct realizations and lead to testable matter-swapping effects, motivating low-energy searches and cosmological applications. The recurrence of the same low-energy fermion operator motivates asking whether this structure can also arise from a D-brane mechanism. We construct a local Type IIB D3$_+$-D7-D3$_-$/E3 realization in which direct interbrane mixing is perturbatively forbidden but generated non-perturbatively by a suitable E3 instanton sector. The resulting low-energy interaction reproduces the characteristic pseudoscalar structure of the two-sheeted fermion operator, together with its scalar companion, while D7 Wilson transport provides the required gauge-invariant relative connection. The construction therefore provides a local string realization of the same operator structure, subject to the stated instanton and zero-mode conditions. The analysis further provides a concrete model-building roadmap toward a compact phenomenological realization: the compactification must achieve electromagnetic sequestering of the two fermion sectors and support a sufficiently light non-uniform D7 gauge mode capable of mediating a long-range relative interaction. In such a complete compactification, the mixing parameter $g$ would in principle become computable from microscopic string data and directly testable against low-energy constraints.

The void probability function (VPF) is the likelihood of finding no tracers (galaxies or dark-matter haloes) within a given volume and is sensitive to the large-scale matter distribution. We investigate the VPF of dark matter haloes and galaxies using the \textsc{Quijote} N-body simulations across a range of cosmological models, including $Λ$CDM and several extensions. We examine its dependence on cosmology, redshift, halo mass, morphology, and sample dilution, and compare the results with theoretical predictions from the geometric hierarchical (GH) and negative binomial (NB) models. We find that the halo VPF is sensitive to cosmology and halo mass and follows the GH model at $z=0$, with $Λ$CDM showing the smallest deviation and the massive-neutrino cosmology the largest. At higher redshift and stronger sample dilution, the VPF departs from the GH model and approaches the NB model. The dependence on halo mass varies with cosmology, with low-mass haloes showing the largest deviations in $Λ$CDM, while intermediate- and high-mass haloes show stronger deviations in the modified-gravity scenario. In redshift space, the VPF shifts toward the NB model, with primordial non-Gaussianity producing the largest deviations. For galaxies, the VPF depends on morphology and cosmology, with ellipticals following the GH model and spirals following the NB model. We also find that cosmic variance introduces non-negligible scatter in the VPF measurements. Overall, these results suggest that the VPF could be useful as a computationally efficient probe to distinguish extensions of the standard $Λ$CDM model in upcoming large-volume galaxy surveys.