In the beam energy scan phase II experiments at the Relativistic Heavy Ion Collider solenoidal tracker, the quark-gluon plasma (QGP) produced with changing collision energies may probe different regions of the QCD phase diagram. Correspondingly, studying the transport coefficients of quark matter in these regions will contribute to extracting the QCD phase structure through hydrodynamic approaches. We investigate the shear viscosity and electric conductivity within the framework of kinetic theory with the relaxation time approximation, in particular their behaviors near the Mott and first-order phase transitions with a spinodal structure as well as along the isentropic trajectories. To derived the scattering cross section under different conditions, the temperature- and chemical-potential-dependent masses of quarks, antiquarks and exchanged mesons are calculated in the Polyakov-loop extended Nambu–Jona-Lasinio model. The numerical results indicate that, at small chemical potential, the shear viscosity to entropy density ratio ($\eta /s$) has a minimum near the Mott phase transition and increases rapidly in the lower-temperature side of the chiral crossover phase transition. At large chemical potential (high baryon density), $\eta /s$ in the QGP phase is dominated by temperature, and the value of $\eta /s$ is greatly enhanced at low temperatures. At intermediate temperature and chemical potential near the QCD phase transition, the behavior of $\eta /s$ is influenced by the competition between temperature, density, and QCD phase transition. The electric conductivity ($\sigma /T$) roughly exhibits similar characteristics to $\eta /s$ in the QCD phase diagram, whereas the dimensionless ratio of $\eta /s$ to $\sigma /T$ decreases monotonically with growing temperature, approaching a constant in the high-temperature limit.

Undecidability, a hallmark of Gödel incompleteness theorems, has recently emerged in quantum many-body physics through the spectral gap problem. We demonstrate how this logical limitation can be holographically transmitted to a class of gravitational theories via the AdS/CFT correspondence. By embedding a translationally invariant spin Hamiltonian with undecidable gap status into a large-N gauge theory, we generate an anti–de Sitter (AdS) dual in which the selection of dominant bulk saddle (Poincaré AdS or AdS soliton) is itself undecidable. Consequently, under standard semiclassical holographic assumptions, even determining which smooth spacetime geometry emerges from quantum gravity can be beyond the limits of computability.

A novel goodness-of-fit strategy is introduced for testing models of angular power spectra with unknown parameters. Using this strategy, it is possible to assess the validity of such models without specifying the distribution of the angular power spectrum estimators. This holds under general conditions, ensuring the method’s applicability in diverse applications. Moreover, the proposed solution overcomes the need for case-by-case simulations when testing different models, leading to notable computational advantages. This paper has been submitted in conjunction with its companion manuscript [Phys. Rev. D 113, 023051 (2025)].

The positive and negative energy modes of a field theory in $\kappa$-Minkowski/$\kappa$-Poincaré noncommutative spacetime have very different symmetry properties. This can be understood geometrically by considering that they span two distinct sectors of a curved momentum space. By performing an explicit direct computation of the relativistic Noether charges and their algebra within the canonical formalism, we identify a striking consequence of this asymmetry in momentum space: charge conjugation and Poincaré invariance are incompatible. We then notice how the structure of momentum space suggests that time reversal could be deformed so that the overall $\mathcal{C}\mathcal{P}\mathcal{T}$-invariance is restored. We prove that this new proposal works by studying the transformation properties under deformed discrete symmetries of the new relativistic charges.

Black holes, as characterized by the Hawking effect and Bekenstein-Hawking entropy, can be treated as a compact object carrying nontrivial quantum information obscured behind the event horizon. This quantum information, while hidden behind the event horizon, can be indirectly probed through the black hole’s interactions with surrounding quantum fields. In this paper, we investigate how the quantum nature of a black-hole influences the correlations harvested by a pair of static Unruh-DeWitt (UDW) detectors. To provide a comprehensive analysis, we employ various correlation measures: concurrence, quantum discord, and the violation of Bell’s inequality, thereby shedding light on the quantum nature of the black hole as perceived by local probes. By treating the black hole as a tidally deformable thermal body under the quantum fluctuation of the mediator fields, as observed by Goldberger and Rothstein [J. High Energy Phys. 04 (2020) 056; Phys. Rev. Lett. 125, 211301 (2020)] and Biggs and Maldacena [arXiv:2405.02227], we employ a post-Newtonian effective field theory (PN-EFT) to derive the final states of the two UDW probes analytically. A key advantage of our approach is the ability to analytically derive all these correlation measures without encountering the complicated Matsubara sum of infinite thermal poles, as in the conventional approach based on quantum fields in curved spacetime. By tuning the relative strengths in the action of PN-EFT, we can extract the effects of the black hole on the entanglement harvesting, quantum correlation, and nonlocality bound of the UDW probe systems. Furthermore, our PN-EFT approach can be extended in future studies to include backreaction on black holes by accounting for higher-order PN corrections.

This work investigates a singularity-free early Universe within the paradigm of quantum cosmology. We develop a bouncing model where the singularity is resolved via the de Broglie–Bohm interpretation of quantum mechanics, which provides a deterministic trajectory for the scale factor through a quantum bounce. The primordial power spectrum for scalar perturbations is derived, incorporating a characteristic modulation (distortion function) imprinted by the nonstandard quantum gravitational dynamics near the bounce. We confront this model with the Planck 2018 cosmic microwave background data, establishing its strong compatibility with observations. Our analysis places a stringent upper bound on the fundamental scale of the bounce $k_{\mathrm{B}}$, constraining the parameter space of such quantum cosmological scenarios. Furthermore, the model’s specific scale-dependent anticorrelation between the spectral index and amplitude of perturbations offers a potential mechanism for mitigating the $H_0\text{−}{\sigma }_8$ tension, presenting a testable signature for future cosmological surveys.

Next-generation gravitational-wave (GW) detectors will produce a high rate of temporally overlapping signals from unrelated compact binary coalescences. Such overlaps can bias parameter estimation (PE) and mimic signatures of other physical effects, such as gravitational lensing. In this work, we investigate how overlapping signals can be degenerate with gravitational lensing by focusing on two scenarios: Type-II strong lensing and microlensing by an isolated point-mass lens. We simulate quasicircular binary black-hole pairs with chirp-mass ratios ${\mathcal{ℳ}}_{\mathrm{B}}/{\mathcal{ℳ}}_{\mathrm{A}}\in \{0.5,1,2\}$, signal-to-noise ratios (SNRs) ${\mathrm{SNR}}_{\mathrm{B}}/{\mathrm{SNR}}_{\mathrm{A}}\in \{0.5,1\}$, and coalescence-time offsets $\mathrm{\Delta }{t}_{\mathrm{c}}\in [-0.1,0.1]\mathrm{s}$, and extend to a population analysis. Bayesian PE and fitting-factor studies show that the Type-II lensing hypothesis is favored over the unlensed quasicircular hypothesis (${\log }_{10}{\mathcal{ℬ}}_{\mathrm{U}}^{\mathrm{L}}>1$) only in a small region of the overlapping parameter space with ${\mathcal{ℳ}}_{\mathrm{B}}/{\mathcal{ℳ}}_{\mathrm{A}}\gtrsim 1$ and $|\mathrm{\Delta }{t}_{\mathrm{c}}|\le 0.03\mathrm{s}$, with the inferred Morse index clustering near $n_j\simeq 0.5$, indicative of Type-II lensing, for the cumulative study. Meanwhile, false evidence for microlensing signatures can arise because, to a reasonable approximation, the model produces two superimposed images whose time delay can closely match $|\mathrm{\Delta }{t}_{\mathrm{c}}|$. The microlensing hypothesis is maximally favored (${\log }_{10}{\mathcal{ℬ}}_{\mathrm{U}}^{\mathrm{L}}\gg 1$) for ${\mathcal{ℳ}}_{\mathrm{B}}/{\mathcal{ℳ}}_{\mathrm{A}}\gtrsim 1$ and equal SNRs, increasing with $|\mathrm{\Delta }{t}_{\mathrm{c}}|$. The inferred redshifted lens masses lie in the range $M_{\mathrm{L}}^z\sim {10}^2–{10}^5{M}_{\odot }$ with impact parameters $y\sim 0.1–3{\mathrm{R}}_{\mathrm{E}}$. Overall, the inferred Bayes factor depends on relative chirp-mass ratios, relative loudness, difference in coalescence times, and also the absolute SNRs of the overlapping signals. Cumulatively, our results indicate that overlapping black-hole binaries with nearly equal chirp masses and comparable loudness are likely to be falsely identified as lensed. Such misidentifications are expected to become more common as detector sensitivities improve. While our study focuses on ground-based detectors using appropriate detectability thresholds, the findings naturally extend to next-generation GW observatories.

Light QCD axions, introduced to solve the strong $CP$ problem, may form condensates inside neutron stars, giving rise to a novel ground state of dense matter. We investigate how such axion condensates modify the equilibrium structure and radial oscillation spectrum of neutron stars. Using a realistic neutron star model with the BSk26 equation of state, and solving the coupled Tolman-Oppenheimer-Volkoff and Klein-Gordon equations together with a linear perturbation analysis, we find two distinct families of quasinormal modes: weakly damped fluid-dominated oscillations and highly damped axion modes. The coupling between the fluid and the axion field introduces axion-induced damping of radial oscillations, with decay timescales of order seconds for kHz axion masses. Modes with frequencies above the axion mass are strongly damped, while those below remain unaffected. Although neutron star radial oscillations are difficult to observe, our results suggest that extensions of this work can turn neutron star seismology into a novel probe of the axion properties.

The discovery of ultrahigh-energy neutrinos by IceCube marked the beginning of neutrino astronomy. Yet, the origin and production mechanisms of these neutrinos remain an open question. With the observation of several neutrino events with energies about PeV, transient sources—astrophysical objects that emit particles in brief, localized bursts—have emerged as promising candidates. In this work, we revisit the identification of such sources in IceCube and future neutrino telescopes, focusing on how both the timing and sky localization of the source affect the detection sensitivity. We present a framework to account for the source’s right ascension in determining the effective area of detectors not located at the poles, such as KM3NeT. As a case study, we investigate evaporating primordial black holes (PBHs) as transient neutrino sources, showing that the detection prospects and localization accuracy are strongly influenced by the PBH’s position in the sky. Our results emphasize the complementarity between neutrino and gamma-ray observatories and showcase the potential of a global network of neutrino detectors to identify and localize transient events that might be missed by traditional photon-based instruments.

It is demonstrated that estimators of the angular power spectrum commonly used for the stochastic gravitational-wave background (SGWB) lack a closed-form analytical expression for the likelihood function and, typically, cannot be accurately approximated by a Gaussian likelihood. Nevertheless, a robust statistical analysis can be performed by extending the framework outlined in Algeri et al. [Phys. Rev. D 113, 021306] to enable the estimation and testing of angular power spectral models for the SGWB without specifying distributional assumptions. Here, the technical aspects of the method are discussed in detail. Moreover, a new, consistent estimator for the covariance of the angular power spectrum is derived. The proposed approach is applied to data from the third observing run (O3) of Advanced LIGO and Advanced Virgo.

Quantum coherence, a cornerstone of quantum mechanics, is of paramount importance for quantum information protocols. However, maintaining coherence in elementary particle systems presents significant challenges. In this work, we investigate quantum coherence and quantum correlations in the $e^{+}{e}^{-}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ processes at BESIII using experimentally feasible parameters, where $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ denote the spin-$1/2$ hyperon and its antihyperon, respectively. We analyze the dependence of quantum coherence and quantum correlations on the scattering angle $\phi$. Notably, these resources reach their maximum at $\phi =\pi /2$. We demonstrate that classical correlations can significantly delay the decay of quantum correlations and coherence. This study underscores the importance of understanding the interplay between classical and quantum correlations in high-energy particle physics, particularly in the context of hyperon-antihyperon interactions explored in the BESIII experiment. Furthermore, we discuss the hierarchy of quantum resources (quantum steering, entanglement of formation, geometric quantum discord, and quantum coherence) in both Markovian and non-Markovian regimes. This result could have potential applications in quantum information processing and high-energy physics.

The dynamics of a light fermion bound to a heavy one is expected to be described by the Dirac equation with an external potential. The potential breaks translation invariance, whereas the bound state momentum is well defined. Boosting the bound state determines the frame dependence of the light fermion dynamics. I study the Dirac limit of ${\mathrm{QCD}}_2$ in the limit of $N_c\to \infty$. The light quark wave function turns out to be independent of the frame of the bound state, up to an irrelevant Lorentz contraction. The discrete bound state spectrum determines corresponding discrete energies of the Dirac equation, which for a linear potential allows a continuous spectrum.

In this manuscript, we study the general scalar leptoquark contributions to the $gg\to Zh$ process at a one-loop level. We find that the contributions only show up for the off diagonal Higgs and $Z$ boson interactions with scalar leptoquarks, which can lead to new tensor structures different from the standard model. In the one-field and two-field models, the contributions vanish exactly; thus, the contributions are possible at least in the three-field models. We exemplify the contributions in the $S_1+{\tilde{R}}_2+S_3$ model, which can appear in the presence of scalar leptoquark mass splittings and $CP$ violation. In view of the heavy scalar leptoquark mass suppression, the leading contributions are typically small and difficult to observe at hadron colliders. However, this work offers a quantitative and systematic investigation of scalar leptoquark contributions, also making it valuable for the new physics studies in other models.

Large-momentum effective theory is a physics-guided systematic expansion to calculate light-cone parton distributions, including collinear (PDFs) and transverse-momentum-dependent ones, at any fixed momentum fraction $x$ within a range of $[x_{\min },x_{\max }]$. It theoretically solves the ill-posed inverse problem that afflicts other theoretical approaches to collinear PDFs, such as short-distance factorizations. Recently, Dutrieux et al. raised practical concerns about whether current or even future lattice data will have sufficient precision in the subasymptotic correlation region to support an error-controlled extrapolation—and if not, whether it becomes an inverse problem where the relevant uncertainties cannot be properly quantified. While we agree that not all current lattice data have the desired precision to qualify for an asymptotic extrapolation, some calculations do, and more are expected in the future. We comment on the analysis and results in Dutrieux et al. and argue that a physics-based systematic extrapolation still provides the most reliable error estimates, even when the data quality is not ideal. In contrast, reframing the long-distance asymptotic extrapolation as a data-driven-only inverse problem with ad hoc mathematical conditioning could lead to unnecessarily conservative errors.

We present a comprehensive study of the screening masses of vector and axial-vector mesons and their corresponding diquark partners within a symmetry-preserving vector-vector contact interaction approach. Our analysis includes mesons and diquarks composed of both light and heavy quarks, providing a unified description of their thermal behavior. The longitudinal and transverse modes of the screening masses are analyzed, and the results are systematically compared with other theoretical approaches. At $T=0\mathrm{MeV}$, our predictions agree with available experimental data, and a comparison with the expected free theory limit at high temperatures is also presented. Notably, the parity partners of the lightest mesons and diquarks converge at high temperatures, signaling chiral symmetry restoration within this framework. These results provide a consistent and detailed picture of meson and diquark properties at finite temperature and lay the groundwork for extending the capabilities of the model to baryon screening masses in the quark-diquark picture.

Isospin violating effects, both due to the nonvanishing quark mass difference $m_d-m_u$ and to virtual photons, are studied by fitting the squared masses of pseudoscalar mesons to the next-to-leading order in the simultaneous expansion in powers of $1/N_c$, momenta, and quark masses. It is shown that electromagnetic corrections significantly affect the values of the ${\pi }^0-\eta$ and ${\pi }^0-{\eta }^{\prime }$ mixing angles and have virtually no effect on the $\eta -{\eta }^{\prime }$ mixing angle. The ${\pi }^0,\eta ,{\eta }^{\prime }\to \gamma \gamma$ decay widths are calculated. In particular, it is found that ${\mathrm{\Gamma }}_{{\pi }^0\to \gamma \gamma }=7.82\pm 0.01\mathrm{eV}$. This result is in full agreement with the latest data of the PrimEx-I and PrimEx-II collaborations ${\mathrm{\Gamma }}_{{\pi }^0\to \gamma \gamma }^{\exp }=7.802\pm 0.052(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}.)\pm 0.105(\mathrm{syst}.)\mathrm{eV}$.

Current template-based gravitational-wave searches for compact binary mergers neglect the general relativistic phenomenon of spin-induced orbital precession. Owing to their asymmetric masses, gravitational waves from neutron star–black hole (NSBH) binaries are prime candidates for displaying strong imprints of spin precession. Current searches may therefore miss a significant fraction of the astrophysical population, and the detected NSBH population may be significantly suppressed or biased. Here we report the most sensitive search for NSBH binaries to date by including spin precession for the first time. We analyze data from the entirety of the third LIGO-Virgo-KAGRA gravitational-wave observing run and show that when accounting for spin precession, our search is up to 100% more sensitive than the search techniques currently adopted by the LIGO-Virgo-KAGRA collaboration (for systems with strong precessional effects). This allows us to more tightly constrain the rate of NSBH mergers in the local Universe. When focusing on a potentially precessing subpopulation of NSBH mergers, the lack of observed candidates allows us to place an upper limit on the merger rate of $R_{90}=79{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ with 90% confidence. We then show that if there is no preferred direction of component spin, the overall rate of NSBH mergers is on average 16% smaller than previously believed. Finally, we report four new subthreshold NSBH candidates, all with strong imprints of spin precession, but note that these are most likely to be of terrestrial origin.

We present the magnetic oscillatory resonator for rare-interaction studies (MORRIS) and propose the first tabletop search for non-Newtonian gravity due to a Yukawa-like fifth force using a magnetically levitated particle. Our experiment comprises a levitated submillimeter magnet in a superconducting trap that is driven by a time-periodic source. Featuring short-, medium-, and long-term stages, MORRIS will admit increasing sensitivities to the force coupling strength $\alpha$, optimally probing screening lengths of $\lambda \sim 1\mathrm{mm}$. Our short-term setup provides a proof-of-principle study, with our medium- and long-term stages respectively constraining $\alpha \lesssim {10}^{-4}$ and $\alpha \lesssim {10}^{-5}$, leading over existing bounds. Our projections are readily recastable to concrete models predicting the existence of fifth forces, and our statistical analysis is generally applicable to well-characterized sinusoidal driving forces. By leveraging ultralow dissipation and heavy test masses, MORRIS opens a new window onto tests of small-scale gravity and searches for physics beyond the Standard Model.

We study the optical properties of black holes endowed with primary Proca hair, focusing on the distinctive double-peak structure generated in the effective potential by the massive vector field. This feature drastically modifies the geodesic motion of both photons and massive particles, leading to qualitatively new dynamical and observational signatures. We derive and analyze the effective potentials, classify timelike and null geodesics, and identify the conditions for multiple circular orbits. Particular attention is devoted to the photon sphere structure, the associated shadows, and lensing phenomena. Our analysis reveals that, for a broad range of parameters, the black-hole shadow can acquire a two-boundary structure and exhibit additional inner rings, unlike the standard Schwarzschild case. These modifications provide potentially observable imprints of Proca hair in electromagnetic spectra, highlighting the relevance of double-barrier optical phenomena for current and future observations of strong-gravity environments.

Solutions to the Einstein equations near the threshold of black hole formation exhibit remarkable behavior known as critical phenomena gravitational collapse. In this work we perform characteristic evolution in compactified Bondi coordinates in order to study the critical collapse of a Yang-Mills field, allowing for the extraction of global quantities such as the Bondi mass and news function. Our numerical approach is fourth-order accurate. First, we demonstrate that the collapsing field exhibits local discretely self-similar (DSS) behavior, characterized by an echoing period of $\mathrm{\Delta }\simeq 0.737$, agreeing with previous works up to the second decimal place. We find that global quantities such as the Bondi mass and news function display the same DSS behavior. We furthermore show that the mass of the black holes formed during near-threshold evolutions scales as a function of the distance to the critical parameter, with a critical exponent of approximately $\gamma =0.1977\pm 0.0009$. Finally, our findings indicate that these results are universal, irrespective of the initial data.