The GW190814 event, involving a black hole of mass $22.2-24.3M_{\odot }$ and a compact object of mass $2.50-2.67M_{\odot }$, challenges our understanding of the mass gap between the heaviest neutron stars and the lightest black holes. If the secondary is a neutron star exceeding $2.5M_{\odot }$, hyperons are likely to appear in its core, softening the equation of state. Rapid rotation can offset some of this softening, enabling higher maximum masses, but it may simultaneously excite the Chandrasekhar-Friedman-Schutz $r$-mode instability. Bulk viscosity arising from nonleptonic weak interactions in hyperonic matter provides an efficient damping mechanism that can stabilize such configurations. In this work, we investigate the combined effects of rotation, thermal evolution, and hyperon-induced bulk viscosity on the stability of massive neutron stars. We demonstrate a direct connection between the suppression of $r$-mode instabilities and the long-term dynamical stability of hyperon-rich stars, offering a plausible interpretation of the GW190814 secondary as a rapidly rotating, hyperon-rich neutron star rather than a low-mass black hole. Our unified framework extends beyond previous studies restricted to static equations of state or extreme viscous damping assumptions, providing new insights into the stability of massive, exotic neutron star configurations.

Motivated by the interpretation of $X(3872)$ as a $D\overline{D}{}^{*}$ molecular state, heavy-quark spin symmetry predicts a spin-2 partner, $X_2(4013)$, which can be regarded as a $D^{*}\overline{D}{}^{*}$ molecule with quantum numbers $J^{PC}=2^{++}$. Its experimental confirmation, however, remains elusive. In this work, we investigate the production mechanisms of $X_2(4013)$ in the reactions $K^{-}p\to D_s^{-}{\mathrm{\Lambda }}_c^{+}{X}_2(4013)$ and $pp\to {\mathrm{\Lambda }}_c^{+}{\mathrm{\Lambda }}_c^{+}{X}_2(4013)$ within an effective Lagrangian framework. The production processes are modeled via $t$-channel $D^{*}/\overline{D}{}^{*}$ meson exchanges, while initial-state interactions (ISIs) mediated by Pomeron and Reggeon exchanges are also taken into account. Our calculations indicate that the total cross sections can reach the pb level, suggesting that $X_2(4013)$ may be accessible at current and future experiments such as AMBER@CERN and LHCb. Inclusion of ISIs enhances the cross sections by nearly 1 order of magnitude. The differential distributions show distinct angular behaviors for the two reactions: the $K^{-}p$ reaction exhibits a forward-peaked distribution, whereas the $pp$ reaction shows a dip near central angles. This study provides a quantitative theoretical benchmark for future experimental searches of $X_2(4013)$ and highlights the importance of ISIs in high-energy particle investigations.

In quantum computing, nonstabilizerness—the magic—refers to the computational advantage of certain quantum states over classical computers and is an essential ingredient for universal quantum computation. Employing the second-order stabilizer Rényi entropy to quantify magic, we study the production of magic states in quantum electrodynamics (QED) via two-to-two scattering processes involving electrons and muons. Considering all 60 stabilizer initial states, which have zero magic, the angular dependence of magic produced in the final states is governed by only a few patterns, in both the nonrelativistic and the ultrarelativistic limits. Some processes, such as the low-energy $e^{-}{\mu }^{-}\to e^{-}{\mu }^{-}$ and Bhabha scattering $e^{-}{e}^{+}\to e^{-}{e}^{+}$, do not generate magic at all. In most cases, the largest magic generated is significantly less than the maximal possible value of $\log (16/7)\approx 0.827$. The only instance where QED is able to generate maximal magic is the low-energy ${\mu }^{-}{\mu }^{+}\to e^{-}{e}^{+}$, in the limit $m_e/m_{\mu }\to 0$, which is well approximated in nature. Our results suggest QED, although capable of producing maximally entangled states easily, may not be an efficient mechanism for generating quantum advantages.

We investigate the emergence of a resonant behavior in axion-trapped misalignment models featuring finite-temperature potential barriers. As the temperature decreases and the field is released from its trapped configuration, inhomogeneities are exponentially amplified through an instability in their equation of motion, leading to the fragmentation of the axion field. We show that this process constitutes a novel source of gravitational waves (GWs), analogous to those generated in zero-temperature axion fragmentation, but with distinct characteristics. We quantify the resulting GW spectrum, identifying the peak frequency and amplitude associated with the inhomogeneous axion dynamics. Our results indicate that the GW signal can be enhanced by up to 2 orders of magnitude compared to the standard fragmentation scenario, while exhibiting a markedly different spectral shape. The parameter space featuring both strong GW signals and reproducing the correct dark matter abundance is, however, limited.

We show that measuring dark matter signal by projecting quantum sensors in the collective excited state can highly suppress the noncollective noise background, hence improving the sensitivity significantly. We trace the evolution of the sensors’ state in the presence of both dark matter effect and sensors’ decoherence effects, optimizing the protocol execution time, and show that the suppression of background by a factor equal to the number of sensors is possible. This method does not require the entanglement of sensors during the signal accumulation time, hence circumventing the difficulty of maintaining the lifetime of the entangled state that is present in other enhancement proposals. This protocol is also general regarding the type of qubit sensors.

The Collins-Soper (CS) kernel governs the rapidity evolution of transverse-momentum-dependent (TMD) parton distributions, a cornerstone for QCD factorization and linking nucleon structure data across scales. Its nonperturbative behavior at large transverse separations ($b_{\perp }$) remains weakly constrained due to phenomenological model dependencies. We present a first-principles determination of the CS kernel at the continuum limit and physical pion mass from lattice QCD in the large-momentum effective theory framework. Using ($2+1$)-flavor configurations (lattice spacings $a\in [0.052,0.105]\mathrm{fm}$, and pion mass $m_{\pi }\approx (136,230,300,320)\mathrm{MeV}$), we simulating the nonlocal equal-time correlation function and extract the quasi-TMD wave functions. Taking into account systematic improvements including hypercubic smearing, nonperturbative renormalization, and a $b_{\perp }$-unexpanded matching kernel, we obtain the CS kernel at the continuum, chiral, and infinite-momentum limits. Our results are determined up to $b_{\perp }\sim 1\mathrm{fm}$, with controllable uncertainties, and agree with perturbative QCD at small $b_{\perp }$ and global TMD phenomenological extractions. We conduct a global analysis integrated with phenomenological fits and demonstrate the impact of our results on such fits. This work yields the most precise nonperturbative constraint on the CS kernel’s long-distance behavior from lattice QCD, which not only bridges lattice QCD, perturbation theory, and nucleon structure experiments for TMD studies, but also boosts the utility of our constraint for future global TMD analyses.

The predictive power of cosmic inflation hinges on the existence of a conserved quantity at very large scales, called the primordial curvature perturbation, which is therefore insensitive to the details of reheating and the physics of the hot big bang. Whether the classical spacetime symmetries responsible for this conservation law can enforce it at the quantum level is an old debate. Although this was never explicitly proven, cosmologists often assume that this freezing holds at all loop orders and that inflationary predictions can always be propagated to the radiation era, with primordial fluctuations playing the role of seeds for the large-scale structures that we observe in our Universe today. In this work, by consistently using the effective field theory of inflationary fluctuations, we explicitly prove for the first time that the renormalized one-loop power spectrum of the primordial curvature perturbation freezes exactly on scales larger than its sound horizon.

We examine the idea that our Universe began as a baby universe and show that this is feasible in a gauged $U(1{)}_{B-L}$ extension of the Standard Model with the classically conformal principle. For the first time, we define a measure to describe the probability that we reside in a baby universe, and find that it can be close to 1 in a considerable portion of the parameter space. The framework is consistent with current cosmological data, and it predicts the existence of a heavy neutral gauge boson, which could be detected at colliders, thereby offering a direct link between early universe dynamics and experimentally testable signatures at the TeV scale.

Arguably, the simplest chiral gauge theories are SO(10) with $N_f$ fermion fields in the spinor representation $\mathbf{16}$. We study their dynamics using their supersymmetric limits perturbed by an infinitesimal anomaly mediated supersymmetry breaking as a guide. We predict the theory is gapped for $N_f=1$, 2, while the $\mathrm{SU}(N_f)$ global symmetry is broken to $\mathrm{SO}({\mathrm{N}}_f)$ for moderately large $N_f\ge 3$.

We propose a novel method to identify the two-pole structure of the $\mathrm{\Lambda }(1405)$. The two poles owe their origin to different quark flavor irreducible representations in the meson-baryon coupled-channel interactions, thus they should be individually manifested in reactions that provide good flavor eigenstate sources. Hadronic decays of charmonia into $\overline{\mathrm{\Lambda }}\mathrm{\Sigma }\pi$ and $\overline{\mathrm{\Lambda }}(1520)\mathrm{\Sigma }\pi$ are such reactions, and the flavor octet and singlet poles can be approximately singled out in these two decay modes. This SU(3) flavor filter works even considering the flavor symmetry breaking. With the huge charmonium data sets collected, it is therefore promising to solve the long-standing $\mathrm{\Lambda }(1405)$ puzzle employing the proposed flavor filter.

We revisit type ${\mathrm{II}}_0$ limits in the vector multiplet moduli space of compactifications of type IIB string theory on Calabi-Yau threefolds. These limits are special because they cannot be described using mirror symmetry. While we showed in previous work that the gravitational duality sector emerging in such limits corresponds to a weakly coupled heterotic string compactified on K3 times a string-sized torus, our focus here is on the additional field theory sectors that decouple from gravity in these asymptotic regimes. Concretely, we argue that, in the dual heterotic description, these field theory sectors correspond to spacetime-filling NS5-branes wrapping the heterotic torus. The existence of such nonperturbative field theory sectors manifests itself in an exponential dependence of the prepotential on the heterotic dilaton at leading order. Applied to $K$-point limits in one-parameter moduli spaces, our results imply that these limits are in perfect agreement with the distance and emergent string conjectures. More precisely, the light tower of states predicted by the distance conjecture arises from excitations of a weakly coupled heterotic string compactified to four dimensions on a background containing spacetime-filling NS5-branes.

We numerically investigate the application of the path-sum-based causal set scalar propagator construction to ($1+1$)-dimensional anti–de Sitter (AdS) spacetime. Building upon a generalization of Johnston’s path sum approach, we simulate Poisson-sprinkled causal sets in ${\mathrm{AdS}}_{1+1}$ and numerically evaluate the retarded scalar propagator, comparing it to the known continuum result. Our results confirm that even in curved spacetimes with constant negative curvature, the discrete causal set path sum reproduces the continuum propagator without modification of the flat-spacetime jump amplitudes, thereby providing further numerical support for former analytical results and the applicability of the path sum formalism to curved Lorentzian manifolds.

Recent years have seen the first production of “postadiabatic” gravitational waveform models based on second-order gravitational self-force theory. These models rely on calculations of an effective source in the perturbative second-order Einstein equation. Here, for the first time, we detail the calculation of the effective source in a Schwarzschild background, which underlies the second-order self-force results in [N. Warburton et al., Gravitational-wave energy flux for compact binaries through second order in the mass ratio, Phys. Rev. Lett. 127, 151102 (2021); S. Isoyama et al., Adiabatic waveforms from extreme-mass-ratio inspirals: An analytical approach, Phys. Rev. Lett. 128, 231101 (2022); B. Wardell et al., Gravitational waveforms for compact binaries from second-order self-force theory, Phys. Rev. Lett. 130, 241402 (2023)]. The source is designed for use in the multiscale form of the Lorenz-gauge Einstein equation, decomposed in tensor spherical harmonics, or in the analogous second-order Teukolsky equation. It involves, among other things, contributions from (i) quadratic coupling of first-order field modes, (ii) the slow evolution of first-order fields, (iii) quadratic products of a first-order puncture field, and (iv) the second-order puncture field. We validate each of these pieces through numerical and analytical tests.

We investigate the relativistic modeling of spacecraft motion in Mercury’s post-Newtonian local coordinates. This investigation is motivated by the fact that Mercury’s post-Newtonian gravitational field (as well as that of any other planet) admits an expansion in terms of multipole moments, which are most appropriately defined in the local reference system. The equations of motion in the Mercury-centric local frame include relativistic local perturbations, given by the Schwarzschild term, Lense-Thirring precession, and the acceleration due to the quadrupole moment, and relativistic third-body perturbations, which are the gravitoelectric and gravitomagnetic accelerations, along with a coupling term between Mercury and other solar system bodies. The relativistic third-body perturbations are usually neglected in all practical applications. In this study, we analyze the magnitude of the post-Newtonian terms of the equations of motion formulated in the Mercury-centric frame, evaluating them along the trajectories of the two BepiColombo spacecrafts. Based on this analysis, we provide a practical approach for constructing a high-accuracy relativistic orbital model suitable for a Mercury orbiter.

We investigate the cosmological implications of Tsallis entropy in two widely discussed frameworks: the Cai-Kim thermodynamic derivation of the Friedman equations and the Tsallis holographic dark energy (HDE) scenario, considering both the Hubble scale and the Granda-Oliveros cutoff as infrared regulators. In both cases, the dynamics introduce a nonextensivity parameter $\delta$, with the standard Bekenstein-Hawking entropy-area relation recovered for $\delta =1$. While previous studies have suggested that only small deviations from extensivity are observationally allowed, typically requiring $|1-\delta |\lesssim {10}^{-3}$, here we go further and perform a systematic consistency analysis across the entire expansion history. We show that even mild departures from $\delta =1$ lead to pathological behavior in the effective dark energy sector: its density can become negative or complex, its equation of state may diverge, or it can contribute an unacceptably large early-time fraction that spoils radiation domination and violates big bang nucleosynthesis and CMB constraints. Our results sharpen and unify earlier hints of tension, providing a clear physical interpretation in terms of corrections that grow uncontrollably with the expansion rate toward the past. We conclude that within both the Cai-Kim and HDE formulations, a viable cosmology emerges only in the extensive limit, effectively reducing the models to $\mathrm{\Lambda }\mathrm{CDM}$. More broadly, our findings emphasize the importance of dynamical consistency and cosmological viability tests, when assessing nonextensive entropy formalisms as potential frameworks for describing the Universe’s dynamics.

In this paper, we investigate the inflationary phenomenology of parity-violating (PV) extensions of symmetric teleparallel gravity by applying this PV gravity theory to axion inflation. The presence of PV terms induces velocity birefringence in the tensor perturbations. During inflation, when the inflaton rapidly traverses the clifflike region in its potential, the tensor modes at specific scales for one of the two circular polarization states undergo significant amplification due to tachyonic instability. Consequently, the resulting primordial gravitational waves (GWs), characterized by a one-handed polarization and a multipeak structure in their energy spectrum, exhibit a significant amplitude potentially detectable by LISA and Taiji, and their chirality could be determined by the LISA-Taiji network. The detection of such a chiral GW signal provides an opportunity to probe inflation and PV gravity theory. Moreover, we perform the Fisher matrix analysis to forecast the constraints on the model parameters with the LISA-Taiji network.

We use the velocity-dependent one scale model for topological defect evolution to explore and classify the possible scaling solutions for string networks with time-varying tension, in cosmological and noncosmological settings and under two different phenomenological assumptions for the behavior of these variations, which rely on different stretching and damping contributions to the string dynamics. We discuss how these assumptions impact the standard scaling solutions, as well as the evolution of the string network density. In addition to simple power-law cosmological epochs solutions, we also discuss the behavior of the network during the radiation-to-matter and matter-to-acceleration transitions. Overall, our results show that for the same amount of tension variation, a change in the stretching length scale tends to have a more significant impact on the network than a change in the damping length.

We show that, for values of the axion decay constant parametrically close to the grand unified theory scale, the Peccei-Quinn phase transition may naturally occur during warm inflation. This results from interactions between the Peccei-Quinn scalar field and the ambient thermal bath, which is sustained by the inflaton field through dissipative effects. It is therefore possible for the axion field to appear as a dynamical degree of freedom only after observable cosmic microwave background scales have become superhorizon, thus avoiding the large-scale axion isocurvature perturbations that typically plague such models. This nevertheless yields a nearly scale-invariant spectrum of axion isocurvature perturbations on small scales, with a density contrast of up to a few percent, which may have a significant impact on the formation of gravitationally bound axion structures such as miniclusters.

We develop a modified interacting dark energy (IDE) model to study the redshift evolution of the Hubble constant ($H_0$), in light of the Hubble tension. In this framework, the energy exchange between dark energy and dark matter induces a redshift dependence of $H_0$. We evaluate the model against a comprehensive suite of observations, including baryon acoustic oscillations (BAO) from DESI DR2 and SDSS, cosmic chronometers, type Ia supernovae from the Pantheon sample, and Planck CMB distance priors. Analysis of late-Universe data yields $\alpha =0.0107_{-0.011}^{+0.0032}$, with the best-fit value on the order of ${10}^{-2}$, revealing a decreasing trend of $H_0$ with redshift. This supports a power-law evolution beyond $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$). Incorporating CMB data further tightens the constraint to the order of ${10}^{-5}$, which we attribute to the suppression of dark-sector interactions at high redshifts, a consequence of the strong baryon–photon coupling. These results indicate that the IDE framework provides a theoretically consistent and observationally viable mechanism for describing the redshift evolution of $H_0$, offering a promising avenue toward alleviating the Hubble tension.

We dig into the semiclassical description of gravity by studying one-loop corrections to primordial power spectra generated during cosmic inflation from gravitational nonlinear interactions. In the realm of the effective field theory (EFT) of inflationary fluctuations, we renormalize the quadratic Lagrangian dictating the linear dynamics of gauge-invariant perturbations. Since gravity is a nonrenormalizable theory, this procedure is performed perturbatively in terms of negative powers of the EFT strong coupling scales. Since the interactions we consider are purely gravitational, they are ubiquitous and independent of the details of the EFT. Our results are thus relevant for a large class of approximately scale-invariant inflationary scenarios, be they driven by a single scalar field with canonical kinetic terms, or with a noncanonical structure à la $P(X,\varphi )$, or for an effective single-field description at the level of fluctuations only and emerging from a covariant multifield theory. Using dimensional regularization, we show that time-dependent ultraviolet divergences appearing at the loop level can be canceled at all times by an appropriate splitting of the bare Lagrangian into renormalized operators and counterterms. Moreover, we explicitly compute all finite contributions to the loops and we prove that, taking into account backreaction, the final one-loop renormalized power spectra of both the primordial curvature perturbation and of gravitational waves are exactly conserved on super-horizon scales. Conclusions of our work imply that the scalar and tensor propagation speeds are immune to radiative corrections from gravitational nonlinearities. We discuss a first application to multifield inflation.