The anisotropies induced by Lorentz-violating fields pose significant challenges for the search for compact objects in nonvacuum environments. In this work, nevertheless, we demonstrate that introducing couplings between Lorentz-violating fields and matter allows a remarkable class of spacetimes: traversable wormholes. Specifically, we consider additional couplings in the Lagrangian of a phantom scalar field and derive Ellis-Bronnikov spacetime analogs in a Lorentz-violating scenario where both a vector field and an antisymmetric rank-2 tensor field spontaneously acquire nonzero vacuum expectation values. Despite the distinct nature of these fields, their nonzero vacuum expectation values contribute additively to the overall effect on the phantom distribution and on the resulting line element. Moreover, to probe the effects of the Lorentz violation in these spacetimes, we consider scalar perturbations lying in these spacetimes either coupled to the Lorentz-violating fields or minimally coupled to the metric. Notably, the additional Lorentz-violating couplings can alter scalar field dynamics so that perturbations propagate as if in a general relativity background, thereby allowing for some traits of Lorentz violation to remain hidden. We compute the quasinormal mode spectra of these perturbations using three methods: direct integration, the 6th-order Wentzel-Kramers-Brillouin approximation, and the Prony method, finding strong agreement among the results.

We compute the gravity model testing parameter $E_G$ (gravity estimator) on realistic simulated modified gravity galaxy mocks adopting the more accurate estimator described in [Z. Wang et al., J. Cosmol. Astropart. Phys. (2023) 038.]. The analysis is conducted using two twin simulations presented in [C. Arnold, M. Leo, and B. Li, Nat. Astron. 3, 917 (2019).]; one based on general relativity (GR) and the other on the $f(R)$ Hu and Sawicki model with $f={10}^{-5}$ (F5). This study aims to measure the $E_G$ estimator in GR and $f(R)$ models using high-fidelity simulated galaxy catalogs, with the goal of assessing how future galaxy surveys can detect deviations from standard gravity. Deriving this estimator requires precise, unbiased measurements of the growth rate of structure and the linear galaxy bias. We achieve this by implementing an end-to-end cosmological analysis pipeline in configuration space, using the multipoles of the two-point correlation function. In our analysis we estimate the scale-dependent growth rate predicted by nonstandard gravity models using COMET-VDG (cosmological observables modelled by emulated perturbation theory-velocity difference generator) fits. We split the estimation of the redshift space distortions (RSD) $\beta$ parameter over distinct scale ranges, separating large (quasilinear) and small (nonlinear) scales. We show that this estimator can be accurately measured using mock galaxies in low redshift bins ($z<1$), although its discriminating power between competing theories is limited. We find that, for an all-sky galaxy survey and neglecting observational systematics, accurate and largely unbiased estimations of $E_G$ can be obtained across all redshifts. However, the error bars are too large to clearly distinguish between the theories. When measuring the scale dependence of the $E_G$ estimator, we note that state-of-the-art theory modeling limitations and intrinsic “prior volume effects” prevent high-accuracy constraints. Alternatively, we propose a null test of gravity using RSD clustering, which, if small scales are modeled accurately in future surveys, could detect departures from GR.

The characteristic decomposition for general relativistic magnetohydrodynamics in the comoving frame of the fluid has been known for a long time. However, it has not been known in the coordinate frame of the simulation and in terms of the conserved variables evolved in typical numerical simulations. This paper applies the method of quasi-invertible transformations developed in Paper I to derive this decomposition. Among other benefits, this will allow us to use the most accurate known computational methods, such as full-wave Riemann solvers. The results turn out to be simpler than expected based on earlier attempts.

The characteristic decomposition for general relativistic magnetohydrodynamics (GRMHD) is not known in a form useful for current numerical simulations. This prevents us from using the most accurate known computational methods, such as full-wave Riemann solvers. In this paper, we present a new method of finding decompositions. The method is based on transformations from the comoving frame, where the fluid flow is simplest and the decomposition has been known for a long time. The key innovation we introduce is that of quasi-invertible transformations. In this first paper, we introduce these transformations using the simpler example of relativistic hydrodynamics. We recover the known decomposition for relativistic hydrodynamics in somewhat simpler form than previously derived, and without the need for computer algebra. A new result in this paper is the characteristic decomposition when the evolution tracks the composition of a fluid in nuclear statistical equilibrium. In Paper II of this series, we apply a quasi-invertible transformation to derive the complete characteristic decomposition for GRMHD in the conserved variables used in simulations.

Ending the inflation by vacuum decay is considered infeasible due to the graceful-exit problem. Even if considering an alternative field other than the inflaton to realize a first-order phase transition (FoPT) during inflation, it is usually challenging in concrete model building, as bubble nucleations might not be fast and dense enough to successfully end inflation. In this work, we propose a FoPT at the grand-unification-theory (GUT) scale within the Starobinsky inflation. The key construction is an exponentially evolving potential barrier dynamically controlled by the rolling inflaton, so that almost no bubbles nucleate during the early inflationary era, but with a large number of bubbles nucleating near the end of inflation. With lattice numerical simulations, we have successfully tested this GUT-FoPT during Starobinsky inflation, and the resulting gravitational-wave energy density spectrum reproduces previous analytical estimation with a distinctive oscillation feature at high frequencies.

We propose a boomerang mechanism for the explanation of the excess radio background detected by ARCADE 2. In an early stage of the Universe, at a temperature $T$ in the range $\sim 0.1\mathrm{keV}-1\mathrm{MeV}$, a fraction of relic neutrinos is resonantly converted into dark neutrinos by mixing induced by a preexisting lepton asymmetry. Dark neutrinos decay much later into a dark-standard photon state and a dark fermion, with a lifetime longer than the age of the Universe, as required by a solution to the excess radio background. This scenario circumvents the upper bound on the neutrino magnetic moment but still implies a testable lower bound.

Topological analyses of galaxy distributions have gathered increasing attention in cosmology, as they are able to capture non-Gaussian features of large-scale structures (LSSs) that are overlooked by conventional two-point clustering statistics. We utilize Betti curves, a summary statistic derived from persistent homology, to characterize the multiscale topological features of the LSS, including connected components, loops, and voids, as a complementary cosmological probe. Using halo catalogs from the quijote suite, we develop a coherent and extendable analysis framework that combines Betti-curve measurements, automated machine-learning-based emulators, and Bayesian inference for cosmological parameter estimation. Within this framework, we assess the sensitivity of Betti curves to cosmological parameters and train emulators to model their dependence on cosmology. Our Bayesian inference recovers unbiased estimation of cosmological parameters, notably, $n_{\mathrm{s}}$, ${\sigma }_8$, and ${\mathrm{\Omega }}_{\mathrm{m}}$, while validation on sub-box simulations confirms robustness against cosmic variance. We further investigate the impact of redshift-space distortions (RSDs) on Betti curves and demonstrate that including RSDs enhances sensitivity to growth-related parameters. When combined with the power spectrum, Betti curves break parameter degeneracies and lead to significantly tighter joint constraints than the power spectrum alone on parameters such as $n_{\mathrm{s}}$, ${\sigma }_8$, and $w$. These results establish Betti curves as a viable and complementary topological observable for cosmological parameter inference and motivate further theoretical and observational developments toward their application in future galaxy surveys.

Low-mass stars ($M\lesssim 2M_{\odot }$) ignite helium under degenerate conditions, eventually causing a nuclear run-away; the helium flash. The alpha-capture process on ${}^{14}\mathrm{N}$ produces a large amount of ${}^{18}\mathrm{F}$, whose subsequent decay spawns an intense ${\nu }_e$ burst (with average energy of 0.38 MeV) lasting about a day. We show that, in addition, a strong 1.7 MeV neutrino line is generated by electron capture on ${}^{18}\mathrm{F}$. Detection is hindered by large backgrounds in state-of-the-art neutrino observatories, such as JUNO. In next-generation facilities, such as the Jinping neutrino experiment, the horizon for a detection with a local significance of $3\sigma$ would be extended to almost 3 pc. Although helium flashes occur a few times per year in our Galaxy, there are no stellar candidates approaching the tip of the red giant branch within 10 pc. Hence, to date, asteroseismology remains the most promising tool for probing the most energetic thermonuclear event in the life of a low-mass star.

The cold dark matter model successfully describes the Universe on large scales, yet faces challenges at subgalactic scales. Ultralight dark matter (ULDM), with particle masses around ${10}^{-22}\mathrm{eV}$, offers a promising solution to these small-scale issues. Pulsar timing arrays (PTAs), designed to detect nanohertz gravitational waves, can also provide a sensitive probe for ULDM signals. In this work, we perform a Bayesian search for ULDM using PTA datasets, focusing on two types of signals: the oscillatory gravitational potential from scalar ULDM and the fifth-force interaction mediated by dark photon dark matter (DPDM). We incorporate pulsar distances in the analysis to better model the ULDM density. No statistically significant evidence for ULDM has been found; therefore, we place 95% confidence level upper limits on the relevant parameters. For scalar ULDM, our analysis does not exclude the scenario in which ULDM constitutes all of dark matter. The constraints from PPTA-DR3 show significant improvements over the earlier PPTA-DR2 (2018 Preview) across most of the mass range, and are consistent with the recent uncorrelated limits from other PTAs. We also present for the first time the DPDM constraints using EPTA data. The obtained bounds on the DPDM from the EPTA-DR2 and PPTA-DR3 are comparable to existing constraints.

We derive updated cosmic microwave background (CMB) constraints on annihilating dark matter and present forecasts for upcoming CMB surveys. We show that the addition of recent temperature, polarization, and lensing data from ground-based experiments yields only minor improvements ($\approx 10\%$) compared to Planck bounds, confirming that the sensitivity remains dominated by the large-scale $E$-mode polarization. Forecasts, using a LiteBIRD-like setup, indicate that pairing a low-noise, wide-sky satellite at $\ell <200$ with high-resolution ground observations nearly saturates the cosmic-variance limit, improving bounds by $\approx 60\%$, where our derived 95th percentile limit is $p_{\mathrm{ann}}<1.27\times {10}^{-28}{\mathrm{cm}}^2{\mathrm{s}}^{-1}{\mathrm{GeV}}^{-1}$. We also consider the inclusion of $B$-mode polarization for a realistic future experiment.

Gravitational-wave (GW) astronomy has advanced our understanding of compact mergers through instruments like the Laser Interferometer Gravitational-Wave Observatory. However, the extreme sensitivity required for these detections makes the instruments susceptible to short-duration transient noise, or glitches, which obscure GW data. Current tools such as Omega Scan and GravitySpy assist in identifying and classifying such noise, but are limited by manual inspection or dependence on large training sets. To address these challenges, we present OmegaNeuron, a machine-learning tool that integrates GravitySpy’s image similarity methods with Omega Scan’s transient analysis to automate the identification of auxiliary channels that witness glitches. Applied to multiple glitch examples, OmegaNeuron consistently highlighted plausible witness channels and showed strong agreement with existing correlation tools, while providing clearer ranking through a quantitative similarity metric. Integrated into the gwdetchar package, OmegaNeuron enables faster analysis that improves glitch witness identification, enhancing both detector sensitivity and the reliability of gravitational-wave observations.

This paper investigates the production of nonprompt photons originating from rotating synchrotron radiation (RoSyRa), specifically the emission of photons by a rigidly rotating quark-gluon plasma in thermal equilibrium, in the presence of an external magnetic field. We compute the nonprompt photon spectrum and its elliptic flow ($v_2$) at midrapidity. In particular, we investigate the finite-volume effects. We find that at low transverse momentum, the magnetic field induces a significant $v_2$, while the plasma rotation boosts the synchrotron radiation of negatively charged quarks. These findings make RoSyRa a viable candidate mechanism to resolve the “direct photon puzzle.”

We investigate a modified affine Toda model coupled to matter (ATM), which includes a scalar self-interacting potential and demonstrate that its first-order integrodifferential structure, preserving a deformed Noether-topological current correspondence, provides a consistent framework for fermion-soliton interactions. In this formulation, the fermion-soliton energy is proportional to the soliton’s topological charge. We evaluate the renormalized energy functional, incorporating one-loop quantum corrections, and perform a variational minimization to determine the configuration that extremizes the functional. The fermionic backreaction and the self-interacting scalar critically shape the fermion-kink energy, the in-gap bound-state spectrum, and the fermionic vacuum-polarization energy, yielding well-defined stability minima of the total energy as functions of the fermion and scalar masses and coupling parameters, in the semiclassical approximation. A key result is that the Heun-equation formalism is necessary to construct nonzero-energy bound and scattering states: unlike the tau-function method, which captures only the zero mode, the Heun approach encodes the full scattering data through local solution matching conditions. These results refine the spectral analysis of deformed integrable models. The stability of soliton-fermion configurations has direct implications for topologically protected states in quantum information and condensed-matter systems.

In this work, we first investigate the chiral transformation properties of the nonlocal pion field operator and construct a generalized nonlocal chiral Lagrangian that is invariant under $\mathrm{SU}(2)$ chiral symmetry transformations. As a simple application, we then calculate the leading order and next-to-leading order pion one loop corrections to the nucleon axial form factors within nonlocal chiral perturbation theory. Then, we fit the next-to-leading order and next-to-next-to-leading order low energy coupling constants (LECs) to lattice QCD data. The fitted results show that the nonlocal LECs are comparatively smaller than their local counterparts. Finally, using these LECs, we compute the $Q^2$ dependence of the nucleon axial form factors. The numerical results indicate that the nonlocal nucleon axial form factors are consistent with lattice QCD data in a wide ${\mathrm{Q}}^2$ range, up to ${\mathrm{Q}}^2=1{\mathrm{GeV}}^2$.

We discuss relaxation solutions to the dark matter-baryon coincidence problem in the context of QCD axion dark matter. In relaxation solutions, a moduli dynamically adjusts the mass of dark matter and baryons until their energy densities are $\mathcal{O}(1)$ the same. Because the QCD axion is heavily connected to QCD, scanning the QCD axion mass inherently also scans the proton mass. In the context of relaxation solutions, this implies that the ratio of dark matter to baryon abundances (${\mathrm{\Omega }}_{\mathrm{DM}}/{\mathrm{\Omega }}_{\mathrm{B}}$) is a ratio of beta functions showing that these models can only accommodate discrete values of ${\mathrm{\Omega }}_{\mathrm{DM}}/{\mathrm{\Omega }}_{\mathrm{B}}$ thereby “predicting” the ratio of the dark matter to baryon abundances. The original composite axion model has only a single integer degree of freedom $N$, the size of the gauge group, and we show that when $N=8$ the observed value of ${\mathrm{\Omega }}_{\mathrm{DM}}/{\mathrm{\Omega }}_{\mathrm{B}}=5.36$ is reproduced to within its percent level error bars. Novel tests of this model include more precise measurements of ${\mathrm{\Omega }}_{\mathrm{DM}}/{\mathrm{\Omega }}_{\mathrm{B}}$, a better lattice determination of the dependence of the proton mass on the high energy QCD gauge coupling, as well as more traditional tests such as fifth force experiments.

In many new physics models with extended gauge symmetry, the new gauge boson $Z^{\prime }$ could mediate the interactions between the dark matter and standard model particles. For the conventional $Z^{\prime }$ portal dark matter, the collider and the direct detection constraints typically pose a significant challenge. To address this pressing issue, we present in this paper a new benchmark model based on the gauged $U(1{)}_{B-L}$ symmetry, which introduces a Dirac dark fermion ${\tilde{\chi }}_1$ and a heavier partner ${\tilde{\chi }}_2$ with zero and nonzero $U(1{)}_{B-L}$ charge, respectively. Including the mass term $\delta m{\overline{\tilde{\chi }}}_1{\tilde{\chi }}_2$ results in the dark fermions ${\chi }_1$ and ${\chi }_2$ in the mass eigenstate, where the lighter one ${\chi }_1$ is regarded as the dark matter candidate. Various intriguing processes for the relic density arise with the compressed mass spectrum $m_{{\chi }_1}\simeq m_{{\chi }_2}$, such as the coscattering ${\chi }_{2}f\to {\chi }_{1}f$, the conversion ${\chi }_2{\chi }_i\to {\chi }_1{\chi }_j$, and the coannihilation ${\chi }_1{\chi }_2\to f\overline{f}$ processes. Suppressed by the small mixing angle $\theta$ between the dark fermions, the small effective gauge coupling of dark matter ${\chi }_1$ to the gauge boson $Z^{\prime }$ is one distinct feature of this model, rendering phenomenology in many aspects more promising. In this paper, we investigate the production of dark matter through new mechanisms within the frameworks of resonance and secluded scenarios. The impacts of phenomenological constraints from colliders, dark matter, and cosmology are also taken into account. We report that the conversion mechanism is both favored by the resonance and secluded scenarios under current constraints.

Axionlike particles (ALPs) are promising candidates for mediating interactions between a dark sector and the Standard Model (SM). In this work, considering the effective interactions of ALPs with the SM gauge bosons and a fermion dark matter (DM), we explore the DM relic satisfied parameter space and assess its testability through indirect searches. The effect of early kinetic decoupling is also discussed in the resonant regime. The potential of probing such ALP-portal fermionic DM at the electron-positron colliders is investigated with the monophoton plus missing energy final states. We show that a spectacular distinction between the signal and SM background is possible via the missing energy variable, the seed of which lies in the ALP-photon interaction, which also governs the relic density of DM. We further discuss the sensitivity of ALP-photon coupling using the ${\chi }^2$ analysis at the future electron-positron collider specifications.

We present a model of the dark sector involving Dirac fermion dark matter, with axial coupling to a dark photon which provides a portal to Standard Model particles. In the nonrelativistic limit, this implies that the dominant effective operator relevant to direct detection is ${\mathcal{O}}_8$. The resulting event rate for direct detection is suppressed by either the dark matter velocity or the momentum transfer. In this scenario there are much wider regions of the dark parameter space that are consistent with all of the existing constraints associated with thermal relic density, direct detection, and collider searches.

The recent observation of a family of fully charm tetraquark states by the LHCb, ATLAS, and CMS Collaborations suggests the possible existence of fully heavy dibaryons. In this work, we investigate the ${\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}$ dibaryons in both the ${}^1{S}_0$ and ${}^5{S}_2$ channels using the method of QCD sum rules. We employ the iterative dispersion relation (IDR) method to efficiently compute the massive five-loop banana diagrams that appear in these systems, and properly address the tricky small-circle divergence problem in the nonperturbative terms. Our analyses reveal that for both charm and bottom systems, the scalar dibaryon lies lower than its tensor counterpart. In the $\overline{\mathrm{MS}}$ scheme, the mass of the scalar ${\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}$ dibaryon is found to be slightly above the $2{\mathrm{\Omega }}_{ccc}$ mass threshold, while the ${\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}$ systems may form bound states. However, they are predicted to be much heavier in the on-shell scheme.