The cosmic reheating is an important epoch in the very early Universe and has significant impacts on the primordial black hole (PBH) abundance and the scalar-induced gravitational wave (SIGW) spectrum. The relevant energy scale and the constituents of cosmic medium are encoded in the reheating frequency $f_{\mathrm{reh}}$ and the equation of state parameter $w$. In this work, we perform a full parameter space Bayesian inference, using the NANOGrav 15-yr dataset to constrain the thermal history of reheating. Treating $f_{\mathrm{reh}}$ and $w$ as free parameters, we systematically investigate the Dirac $\delta$, narrow, and broad log-normal primordial power spectra. Current pulsar timing array data can effectively constrain the peak frequency of the SIGW spectrum as $f_{\mathrm{p}}\sim {10}^{-7.6}-{10}^{-7.0}\mathrm{Hz}$, along with $f_{\mathrm{reh}}\sim {10}^{-9.0}-{10}^{-8.3}\mathrm{Hz}$ and $w\sim 0.19–0.79$ (the 68% confidence level), when the power spectrum has a relatively narrow width $\mathrm{\Delta }\lesssim 1$. A broader power spectrum introduces a smoothing effect that obscures the characteristic frequency knee in the SIGW spectrum, leading to the loss of information about cosmic reheating. Furthermore, for the Dirac $\delta$ and narrow spectra, the PBH masses associated with the SIGWs are anchored at the planetary mass scale around ${10}^{-6}-{10}^{-4}{M}_{\odot }$. This establishes a consistent physical framework that naturally bridges the nanohertz gravitational wave background with the dark matter candidates implied by the Optical Gravitational Lensing Experiment microlensing events.

Astrophysical processes associated with galaxies may contribute to the magnetization of cosmic voids. We investigate the diffusion of galactic magnetic fields in an expanding Universe in the presence of turbulent magnetic diffusivity. To estimate the turbulent magnetic diffusivity, we analyze the TNG50-1 dataset of the IllustrisTNG simulation and derive its redshift dependence from the characteristic turbulent velocity and turbulent scale of the intergalactic medium. Using the resulting diffusivity, we find a present-day magnetic screening length of $\sim 7\mathrm{Mpc}$, roughly 20 times larger than previous estimates based on a constant turbulent diffusivity due to the larger turbulent scale obtained in our analysis. This scale corresponds to a significant fraction of the characteristic size of cosmic voids and suggests that galactic magnetic fields can play a more important role in void magnetization than previously estimated.

The composition and properties of infinite nuclear matter under extreme conditions of temperature and pressure remain incompletely understood. In this work, we constrain the equation of state (EoS) of nuclear matter—constructed within the framework of the relativistic mean field (RMF) model—by combining results from chiral effective field theory and multimessenger observations of neutron stars. Using the saturation properties of nuclear matter, we generate a wide ensemble of EoS, which are subsequently constrained within a Bayesian framework. The resulting posterior distributions provide tight bounds on both the saturation parameters and the coupling constants of the RMF model. The radius of a $1.4M_{\odot }$ neutron star is tightly constrained to ${12.471}_{-0.394}^{+0.427}\mathrm{km}$, while the maximum mass reaches ${2.156}_{-0.120}^{+0.175}{M}_{\odot }$. Furthermore, our analysis reveals that the $\omega –\rho$ coupling, which governs the density dependence of the symmetry energy, becomes increasingly significant under successive astrophysical constraints. Finally, the predicted ${\mathrm{r}}_{\mathrm{skin}}$ of ${}^{48}\mathrm{Ca}$ agrees well with the CREX measurement, whereas that of ${}^{208}\mathrm{Pb}$ remains in tension with PREX-II. In contrast to earlier studies, we do not observe a clear correlation between the ${\mathrm{r}}_{\mathrm{skin}}$ of ${}^{208}\mathrm{Pb}$ and the symmetry energy slope parameter $L$.

Strange quark matter, as one of the most extreme dense states in astrophysics, can be explored through relativistic compact objects. Hypothetical relativistic stars composed of dense strange quark matter are characterized by the equation of state of that matter. The spontaneous scalarization of strange quark stars is influenced by the equation of state of strange quark matter. Here, we investigate how the equation of state of strange quark matter influences the spontaneous scalarization of these stars. Considering normal, color-flavor-locked (CFL), and CFL matter with a free strange quark mass quark matter in the bag models and applying the scalar-tensor gravity, we calculate the structure of scalarized strange quark stars. We investigate how the effective bag constant, perturbative QCD parameter, CFL pairing gap, and strange quark mass control the mass-radius relation, the central scalar field, the scalarization thresholds, and the scalar charge. Our results demonstrate that strange quark stars in scalar-tensor gravity are viable, testable objects, and they establish a complete framework for constraining both the gravitational theory and the properties of cold quark matter with current and future multimessenger observations.

The coalescence of degenerate helium cores during red giant collisions—a process we term “erythrohenosis”—introduces a novel class of transient astrophysical sources of high-energy neutrinos. Using stellar models generated with mesa and smoothed-particle hydrodynamics simulations of the final inspiral phase, we develop a semianalytical model to estimate the amount of hydrogen mixed into the cores, the energy release ($\approx 4.28\times {10}^{49}\mathrm{erg}$) that heats the remnant to $T_f\approx 5.3\times {10}^8\mathrm{K}$, the magnetic field amplification ($B\approx 1.77\times {10}^{10}\mathrm{G}$), and the resulting neutrino flux. The predicted TeV–PeV neutrino signal may contribute to the diffuse IceCube neutrino flux; we estimate that the horizon at which a single neutrino event is expected on average at $\gtrsim 100\mathrm{TeV}$ is $\approx 55\mathrm{kpc}$ for individual merger events. Furthermore, we discuss the probability of a magnetized helium flash and assess the subsequent activation of the CNO cycle in the remnant core due to hydrogen mixing. In particular, neutrinos from the decay of ${}^{18}\mathrm{F}$ offer a direct observational test of the detonation, (as sources within $\sim 4.4\mathrm{pc}$ would produce a neutrino flux exceeding the solar CNO neutrino background). The simultaneous emission of high-energy hadronic neutrinos, gravitational waves, and—if the optical depth permits (${\tau }_{\mathrm{T}}\sim {10}^{14}$ in the core of the remnant)—an electromagnetic signal would constitute a unique multimessenger signature of red giant core collisions, positioning erythrohenosis events as exotic yet potentially observable phenomena in dense stellar systems.

We present a quantum-enhanced protocol for detecting wavelike dark matter using an array of $N$ entangled superconducting cavities initialized in an $m$-photon Fock state. By distributing and recollecting the quantum state with an entanglement-distribution operation, the scan rate scales as $N^2(m+1)$ while thermal excitation is the dominant background, significantly outperforming classical single-cavity methods under matched conditions. We evaluate the robustness of our scheme against additional noise sources, including decoherence and beam splitter infidelity, through theoretical analysis and numerical simulations. In practice, the key requirements, namely high-Q superconducting radio-frequency cavities that support long integration times, high-fidelity microwave beam splitters, and universal cavity control, are already available on current experimental platforms, making the protocol experimentally feasible.

The “knee” of cosmic ray spectra may reflect the maximum energy accelerated by galactic cosmic ray sources or the limit of the galaxy’s ability to bind cosmic rays. Measurements of individual energy spectra are a crucial tool to understand the origin of the knee. Energy reconstruction and composition identification are foundations of the individual energy spectra measurements. One of the main scientific goals of Large High Altitude Air Shower Observatory (LHAASO) is measuring the cosmic ray energy spectra and composition from $\sim 10\mathrm{TeV}$ to $\sim \mathrm{EeV}$. In this work, a novel method for reconstructing energy and logarithm mass (lnA) based on a superposition model is introduced. Energy and lnA are reconstructed using two universal, composition- and energy-independent calibration lines. For zenith angle below 40 degree, the energy and lnA biases are within $\pm 5\%$ and $\pm 0.3$, respectively, across all compositions. The method uses particle densities—measured by LHAASO’s electromagnetic and muon detectors at a fixed distance from the shower axis—rather than integrated particle counts in annular bands. The density-based approach improves resolution for both energy and lnA, especially for heavy nuclei. The resulting energy resolution ranges from below 5% to $\sim 15\%$ above 1 PeV, the best mass resolution for iron achieved is below 25% above 10 PeV. The hadronic model dependencies of energy and lnA are also reported. These dependencies scale with lg($E/A$) and are nearly independent of primary composition.

The geometry of the Einstein Telescope, the proposed next-generation European gravitational-wave observatory, is yet to be finalized. Two competing designs are under consideration: a nested triangular configuration (ET-$\mathrm{\Delta }$) and two separated $\mathsf{L}$-shaped detectors (ET-2L). Extensive prior comparisons of ET designs established the scientific landscape using the Fisher-information-matrix formalism and identified that duty-cycle-induced single-detector operation is precisely the regime where this approximation becomes less reliable, underscoring the need for a refined, principled treatment of the duty cycle. In this manuscript, we build on that foundation by revisiting the comparison with full Bayesian parameter estimation of gravitational-wave signals from binary black hole mergers, projected onto a simulated Einstein Telescope that incorporates a refined duty cycle modeled via continuous-time Markov chains and testing different detector maintenance strategies. We find that the redundancy inherent in the ET-$\mathrm{\Delta }$ design enables it to maintain at least two operational detectors for the majority of the observing time, whereas the ET-2L configuration is often limited to a single detector. Crucially, we show that, during partial network operation, ET-$\mathrm{\Delta }$ often outperforms ET-2L, and that the increased multidetector uptime translates into tighter constraints on the luminosity distance and source-frame component masses. Notably, this remains true even when gravitational-wave events have a lower signal-to-noise ratio in ET-$\mathrm{\Delta }$ than in ET-2L.

Neutrino momentum reconstruction at hadron colliders is intrinsically ambiguous because the longitudinal momentum is not directly observed. We study this problem in semileptonic $t\overline{t}$ events using mixture of neutrino solutions with transformer event representation (monster), a mixture density network that predicts a multivariate normal mixture for the conditional distribution of neutrino momentum from reconstructed event objects. The model uses a transformer-based event encoder and yields a sampling-free point estimate of the neutrino momentum from the closed-form density. On the public benchmark introduced with $\nu$-flows, monster reduces the 68th percentile of the three-momentum residual by 5% and the 95th percentile by 6% relative to the empirical-mode $\nu$-flows baseline, with per-variable root-mean-square errors smaller by 2 to 9% at comparable bias, while running 2 to 8.5 times faster at inference, depending on the device and batch size. These results indicate that mixture density networks are a competitive alternative to normalizing flows for neutrino reconstruction.

The efficient preparation of correlated thermal states, such as the thermofield double state, is a fundamental prerequisite for simulating quantum gravity models and many-body thermodynamics on quantum processors. In this work, we investigate the ground-state preparation of the two coupled Sachdev-Ye-Kitaev model, known as the Maldacena-Qi model, which is dual to a traversable wormhole in anti–de Sitter space in two dimensions, utilizing feedback-based quantum algorithms. We demonstrate that the standard feedback-based quantum algorithm (FALQON) and its time-rescaled variant (TR-FALQON) face severe kinetic limitations in this system, failing to converge to the highly entangled ground state when initialized in trivial product states. To overcome these barriers, we propose the hybrid ITE-TR-FALQON protocol, which integrates the imaginary-time evolution present in imaginary-time-enhanced FALQON with the time-rescaling mechanism. Our ideal state-vector simulations show that imaginary-time filtering overcomes the stagnation observed for the unitary protocols with the chosen driver and initial state, while time rescaling reduces the number of algorithmic layers. The hybrid protocol achieves fidelities close to unity with the exact-diagonalization ground state and reproduces its von Neumann and Rényi entropies with high precision. These results constitute a numerical proof of principle: implementing the nonunitary updates, repeated feedback measurements, and the resulting compiled circuits remains a substantial obstacle, and the protocol in its present form is not a practical state-preparation method for current noisy intermediate-scale quantum devices.

In this paper, we calculate the pion one-loop corrections to the electromagnetic form factors of the nucleon up to $\mathcal{O}(p^4)$ order in the nonlocal framework. To systematically investigate the role of vector-meson dominance in the model, we also include the leading-order nucleon–vector-meson coupling. Owing to the renormalization-scheme dependence of chiral low-energy coupling constants, we refit these constants to the nucleon magnetic moments, electromagnetic radii, and the $Q^2$-dependence of the electromagnetic form factors. Compared with the previous local analysis, the model results show that, in the nonlocal framework, the $Q^2$-dependence of the electromagnetic form factors in the large-$Q^2$ region is significantly improved and is consistent with experimental data.

We compute hard-region contributions to the fermion self-energy and the off-shell fermion-photon vertex in massless thermal QED in a covariant $R_{\xi }$ gauge. The calculation includes the one-loop next-to-leading-power and two-loop leading-power terms in the expansion in soft external momenta, together with the zero-temperature counterterms required to remove ultraviolet subdivergences. In the real-time formalism, we first derive symmetry constraints on the two-fermion-$N$-photon amplitudes, which lead to distinct selection rules in the soft-momentum expansion. The fermion-photon vertex is decomposed into Dirac-vector and axial-vector coefficients. The former satisfies the Ward-Takahashi identity, while the latter is transverse to the photon momentum. These relations are verified at the integrand level. The hard self-energy corrections computed here produce no finite contribution to the fermion damping rate. Our results provide previously unavailable two- and three-point hard-region data for higher-order analyses of fermion mass shifts and inclusive rates, as well as for the construction of a next-to-leading-order fermionic effective action.

The topological susceptibility of the QCD vacuum provides an understanding of $\theta$ vacua as vacua of a Chern-Simons gauge theory. In this way, it gives an immediate proof of the physicality of the boundary $\theta$-term. This makes the essence of the strong-$CP$ puzzle very transparent and offers a solution in form of the gauge axion, which has exact quality. This axion represents an intrinsic part of the QCD gauge redundancy without any reference to an anomalous global symmetry. It is a two-form transforming under the QCD gauge symmetry. Because of its pure-gauge nature, the gauge axion represents a powerful tool to monitor physics of $\theta$ vacua in various regimes. Unlike the ordinary Peccei-Quinn axion, which is UV completed into a Goldstone phase of a complex scalar and thereby suffers from the quality problem, the gauge axion is UV completed directly into a fundamental theory of gravity. We study the domain wall and string structure of the gauge axion and show that the strings sourcing it must be a part of this fundamental theory. We thus observe that the absence of the axion quality problem motivates the presence of fundamental strings. This provides a new argument for a connection between the axion and gravity.

We provide the conditions for complete asymptotic freedom for chiral gauge theories including scalars, as motivated by grand unified models. These are generalized Georgi-Glashow and Bars-Yankielowicz theories that feature a scalar field transforming either in the fundamental or in the adjoint of the gauge group. In both scenarios, we consider the addition of multiple chiral fermion families. We systematically analyse the interplay between gauge, Yukawa, and quartic couplings required for all interactions to remain asymptotically free at short distances. We find that, for both scalar representations, complete asymptotic free models can be obtained for a specific number of colors and multiplicity of vectorlike and chiral families.

We derive an exact relation among the normalized branching fractions of ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }\nu \overline{\nu }$ and $B\to K^{(*)}\nu \overline{\nu }$, within the lepton-number-conserving effective Hamiltonian in which only active neutrinos contribute to the invisible final state. Although the effective Hamiltonian contains 18 independent Wilson coefficients, the three normalized rates depend on only two independent combinations of them, leading to an exact algebraic relation. Remarkably, the central values of the coefficients of this baryon-meson relation are close to $1/4$ and $3/4$, which appear in the heavy-to-heavy $b\to c$ semileptonic sum rule among the branching fractions of ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau \overline{\nu }$ and $B\to D^{(*)}\tau \overline{\nu }$. Once the decay rate of $B\to K^{*}\nu \overline{\nu }$ is measured, the decay rate of ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }\nu \overline{\nu }$ can be determined in a model-independent manner for new-physics scenarios involving only active neutrino interactions, thereby providing a clean target prediction for future experiments. This clearly demonstrates that observables in baryonic and mesonic $b\to s\nu \overline{\nu }$ transitions will serve as a compact consistency test and a powerful probe for discriminating among new-physics scenarios.

We present an extension of the Standard Model based upon the gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ symmetry, featuring an ultralight vector boson that couples to the difference of muon and tau lepton numbers. This anomaly-free construction, whilst historically motivated by the muon’s anomalous magnetic moment, is here employed as an independent phenomenological framework for solar neutrino physics. Through kinetic mixing with the photon, the $Z^{\prime }$ boson generates an effective matter potential within the solar interior, thereby modifying neutrino flavor oscillations via the Mikheyev-Smirnov-Wolfenstein mechanism. Utilizing recent solar neutrino measurements from Borexino, SNO, and Super-Kamiokande, together with an up-to-date solar standard model, we constrain the boson mass to be below $5.7\times {10}^{-17}\mathrm{eV}$, positioning it as a potential ultralight dark matter candidate. The optimal model, corresponding to a coupling parameter ${\eta }_o\approx -2$, yields ${\chi }_{\nu }^2=2.7$, which compares favorably with the standard three-flavor scenario (${\chi }_{\nu }^2=3.1$). This best-fit configuration corresponds to an effective four-fermion coupling $g_{Z^{\prime }}^2ϵ/m_{Z^{\prime }}^2\approx 6.6\times {10}^{-23}{\mathrm{eV}}^{-2}$, approximately 5.7 times the Fermi constant, which for $ϵ\approx 1$ and a reference mediator mass of 1 eV is equivalent to a gauge coupling $g_{Z^{\prime }}\approx 8\times {10}^{-12}$. We furthermore present projections for forthcoming experiments. The Jiangmen Underground Neutrino Observatory (JUNO), which commenced operations in August 2025 and has already achieved world-leading precision in oscillation parameter measurements, together with the XLZD consortium, should substantially refine these constraints. Such ultralight particles may address long-standing discrepancies in galaxy simulations within the cold dark matter paradigm, and recent theoretical developments demonstrate their compatibility with nonthermal dark matter production mechanisms. Additionally, terrestrial long-baseline neutrino experiments provide complementary probes of this parameter space.

The vast majority of extensions of the Standard Model affecting the number of effective relativistic neutrino species ($N_{\mathrm{eff}}$) do so additively, namely, they enhance this quantity with some light state contributing to dark radiation. In this work, we consider precisely the opposite case: new physics scenarios that can lead to $N_{\mathrm{eff}}<3$ that are consistent with all known cosmological, astrophysical, and laboratory data. We are motivated by three main reasons: (1) a recent measurement from Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) in combination with Planck that leads to $N_{\mathrm{eff}}=2.81\pm 0.12$, (2) by a new and powerful measurement of the primordial helium abundance, which anchors $N_{\mathrm{eff}}$ to be very close to the Standard Model value one second after the big bang, (3) by the deployment of the Simons Observatory which will provide precise tests of the radiation content in the Universe and which may detect with a high significance cosmologies with $N_{\mathrm{eff}}<3$. We survey the main theoretical possibilities and find that only a few simple scenarios can consistently give $N_{\mathrm{eff}}=2.81\pm 0.12$. One class consists of thermal electrophilic relics with masses $m\sim 8–13\mathrm{MeV}$. Another consists of out-of-equilibrium particles decaying to $e^{+}{e}^{-}$ or $\gamma \gamma$, with a rather particular lifetime $0.05\mathrm{s}\lesssim \tau \lesssim 3\min$, mass $250\mathrm{MeV}\lesssim m\lesssim 600\mathrm{MeV}$, and abundance $\rho /{\rho }_{\gamma }\sim 0.1$ at decay. Thermal electrophilic particles are especially interesting because they can account for the dark matter in the Universe and can be tested in experiments such as SENSEI, DAMIC-M, and Oscura, and their portals to the visible sector at experiments such as NA64 and LDMX. We conclude that if the Simons Observatory confirms that $N_{\mathrm{eff}}\simeq 2.8$, it will point to very specific extensions of the Standard Model.

The work was motivated by the numerical result that, in a pure SU(2) gauge theory, the ratio $R$ of the effective noncompact and compact lattice spacing is larger than 1 and increases with decreasing gauge coupling, with the expectation that it should further increase extending the parameter space. This means that with a noncompact regularization, at a given number of lattice sites and comparable scaling, one can obtain a larger physical volume whose importance for the control of size effects has long been known. We confirm qualitatively results and expectation by a perturbative evaluation of the effective lattice spacing in an expansion in the Plank constant of noncompact pure SU(2) and Abelian gauge theories, but we find in addition that $R$ reaches the maximum value of $\sqrt{2}$. Including matter fields, we find that R increases (still up to $\sqrt{2}$) or decreases depending on the difference between the number of scalar and spinor degrees of freedom, and there are bounds on such a difference.

We study the origin of the nonmonotonic magnetic field dependence of the lowest charged pion excitation observed in lattice QCD. In a magnetic field, the charged pion mixes with the longitudinally polarized charged rho meson, which shares the same quantum numbers. Within the ${\mathrm{SU}(2)}_f$ Nambu–Jona-Lasinio model supplemented by a gauge invariant tree-level $\pi \text{−}\rho$ mixing operator constrained by the experimental ${\rho }^{\pm }\to {\pi }^{\pm }\gamma$ decay width, we compare four mass extraction schemes: rest mass reconstruction, local bosonization, direct determinant solving with Landau projection, and near-pole expansion. The rest mass scheme cannot reproduce the lattice type turnover, while in the local derivative expansion scheme the turnover presence but is weak which occurs at large magnetic field. By contrast, the direct determinant and near-pole schemes both retain a robust nonmonotonic lowest mode. The former is most faithful to the Landau level kinematics of the charged excitation, while the latter most clearly shows that residue suppression enhances the effective mixing after canonical normalization. Our results indicate that the lattice behavior is a genuine quasiparticle mixing effect, but one whose robustness depends crucially on how the charged meson pole structure is extracted in a magnetic field.

We show that fixed-$j$ holographic double deeply virtual Compton scattering (DDVCS) and its DVCS limit give a fixed-scale structural match to the singlet conformal-operator product expansion Wilson-kernel family of QCD in the leading-twist unpolarized singlet vector channel. The open-string $C_1(\delta ,\vartheta )$ hypergeometric kernel was derived by Nishio-Watari; the new closed-string result is that the Brower-Polchinski-Strassler-Tan (BPST) upper Witten vertex gives the same family with a different near-boundary power count, because ${\mathrm{\Delta }}_c(j)$ is fixed by the BPST trajectory rather than by open-Regge data. The Mellin exponent is therefore derived as ${\delta }_c(j)=j+{\mathrm{\Delta }}_c(j)-2=2j+{\gamma }_c(j)$ rather than inserted by hand. The even open branch gives the parallel unprotected counterpart in the projected singlet vector amplitude. At $Q=\mu ={\mu }_0={\mu }_{*}$, the point is not merely that equal-endpoint evolution is trivial; it is that the ultraviolet Witten vertex has already produced the fixed-$j$ conformal kernel before the lower conformal moment is matched. In the conformal partial-wave/conformal subtraction representation, beta-proportional conformal-anomaly terms and scheme transformations are coefficient/evolution bookkeeping away from the matching point, not replacements for the projected fixed-scale hypergeometric $\eta /\xi$ Wilson-kernel family. The protected/unprotected $j=2$ split identifies the protected closed branch with the ($-$) conformal partial wave and the even open branch with the unprotected ($+$) counterpart; these are mixed singlet eigenchannels, not literal unmixed quark/gluon operators at finite $N_c$. The comparison therefore gives a direct conformal-basis interpretation of the fixed-$j$ holographic $t$-channel Witten diagram: the ultraviolet vertex generates the universal Wilson-kernel family, while the lower vertex supplies the channel-dependent nonperturbative conformal moment.