We explore the possibility of embedding regular compact objects with an (anti-)de Sitter [(A)dS] core as solutions of Einstein’s gravity minimally coupled to a real scalar field. We consider, among others, solutions interpolating between an inner, potential-dominated core and an outer, kinetic-term-dominated region. Owing to their analogy with slow-roll inflation, we term them gravitational vacuum inflative stars, or gravistars for short. We systematically discuss approximate solutions of the theory describing either the core or the asymptotically flat region at spatial infinity. We extend nonexistence theorems for smooth interpolating solutions, previously proved for black holes, to compact objects without event horizons. This allows us to construct different classes of exact (either smooth or nonsmooth) singularity-free solutions of the theory. We first find a smooth solution interpolating between an AdS spacetime in the core and an asymptotically flat spacetime (a Schwarzschild solution with a subleading $1/r^2$ deformation). We proceed by constructing nonsmooth solutions describing gravistars. Finally, we derive a smooth scalar lump solution interpolating between ${\mathrm{AdS}}_4$ in the core and a Nariai spacetime at spatial infinity.

The theory of nongravitational interaction between a pressureless dark matter (DM) and dark energy (DE) is a phenomenologically rich cosmological domain which has received magnificent attention in the community. In the present article we have considered some interacting scenarios with some novel features: the interaction functions do not depend on the external parameters of the Universe, rather, they depend on the intrinsic nature of the dark components; the assumption of unidirectional flow of energy between DM and DE has been extended by allowing the possibility of bidirectional energy flow characterized by some sign shifting interaction functions; and the DE equation of state has been considered to be either constant or dynamical in nature. These altogether add new ingredients in this context, and we performed the phase space analysis of each interacting scenario in order to understand their global behavior. According to the existing records in the literature, this combined picture has not been reported elsewhere. From the analyses, we observed that the DE equation of state as well as the coupling parameter(s) of the interaction models can significantly affect the nature of the critical points. It has been found that within these proposed sign shifting interacting scenarios it is possible to obtain stable late time attractors, which may act as global attractors corresponding to an accelerating expansion of the Universe. The overall outcomes of this study clearly highlight that the sign shifting interaction functions are quite appealing in the context of cosmological dynamics, and they deserve further attention.

Gravitational waves (GWs) can provide crucial information about the central engines of core-collapse supernovae (CCSNe). In order to unveil the nature of GW emission in CCSNe, we apply perturbative analyses with the same underlying equations as simulations to diagnose oscillations of the proto-neutron star (PNS) during $\sim 1\mathrm{s}$ postbounce. In the pseudo-Newtonian case, we find that radial profiles of GW emission match well between the perturbative analysis with $l=2$ and simulations inside the PNS at any frequency and time. This confirms that the GW emission of CCSNe arises from the global PNS oscillations in the perturbative regime. Based on this, we solve for the discrete eigenmodes with a free PNS surface and tentatively identify a set of $g$ modes and the $f$ mode contributing to the peak GW emission. We also offer a possible explanation for the power gap in the GW spectrum found in simulations that lies at the frequency with vanishing cumulative emission of the PNS. Our results enhance the predictive power of perturbative analyses in the GW signals of CCSNe.

The residual gas damping of the test mass (TM) in the free molecular flow regime is studied in the finite open systems for high-precision gravity-related experiments. Through strict derivation, we separate the damping coefficients for two finite open systems, i.e., the biplate system and the sensor core system, into base damping and diffusion damping. This elucidates the relationship between the free damping in the infinite gas volume and the proximity damping in the constrained volume, unifies them into one microscopic picture, and allows us to point out three pathways of energy dissipation in the biplate gap. We also provide the conditions that need to be met to achieve this separation. In applications, for space gravitational wave detection, our results for the residual gas damping coefficient for the 4TM torsion balance experiment are the closest to the experimental and simulation data compared to previous models. For the LISA mission, our estimation for residual gas acceleration noise at the sensitive axis is consistent with the simulation result, within about 5% difference. In addition, in the test of the gravitational inverse-square law, our results suggest that the constraint on the distance between TM and the conducting membrane can be reduced by about 28%.

Neutrinos can undergo fast flavor conversions (FFCs) within extremely dense astrophysical environments, such as core-collapse supernovae (CCSNe) and neutron star mergers (NSMs). In this study, we explore FFCs in a multienergy neutrino gas, revealing that when the FFC growth rate significantly exceeds that of the vacuum Hamiltonian, all neutrinos (regardless of energy) share a common survival probability dictated by the energy-integrated neutrino spectrum. We then employ physics-informed neural networks (PINNs) to predict the asymptotic outcomes of FFCs within such a multienergy neutrino gas. These predictions are based on the first two moments of neutrino angular distributions for each energy bin, typically available in state-of-the-art CCSN and NSM simulations. Our PINNs achieve errors as low as $\lesssim 6\%$ and $\lesssim 18\%$ for predicting the number of neutrinos in the electron channel and the relative absolute error in the neutrino moments, respectively.

Stimulated by the exciting progress on the observations of the fully charmed tetraquarks at LHC, we carry out a combined analysis of the mass spectra and fall-apart decays of the $1S$-, $2S$-, and $1P$-wave $cc\overline{c}\overline{c}$ states in a nonrelativistic quark model. It is found that the $X(6600)$ structure observed in the di-$J/\psi$ invariant mass spectrum can be explained by the $1S$-wave state $T_{(4c)0^{++}}(6550)$. This structure may also bear some feed-down effects from the higher $2S$ and/or $1P$ tetraquark states. The $X(6900)$ structure observed in both the di-$J/\psi$ and $J/\psi \psi (2S)$ channels can be naturally explained by the $2S$-wave state $T_{(4c)0^{++}}(6957)$. The small shoulder structure around 6.2–6.4 GeV observed at CMS and ATLAS may be due to the feed-down effects from some $1P$-wave states with $C=-1$ and/or some $2S$-wave states with $J^{PC}=0^{++}$. Other decay channels are implied in such a scenario and they can be investigated by future experimental analyses. Considering the large discovery potential at LHC, we also present predictions for the $bb\overline{b}\overline{b}$ states which can be searched for in the future.

Motivated by the first observation of the double-charm tetraquark $T_{cc}^{+}(3875)$ by the LHCb Collaboration, we investigate the nature of $T_{cc}^{+}$ as an isoscalar $D{D}^{*}$ hadronic molecule in a meson-exchange potential model incorporated by the coupled-channel effects and three-body unitarity. The $D^0{D}^0{\pi }^{+}$ invariant mass spectrum can be well-described and the $T_{cc}^{+}$ pole structure can be precisely extracted. Under the hypothesis that the interactions between the heavy flavor hadrons can be saturated by the light meson-exchange potentials, the near-threshold dynamics of $T_{cc}^{+}$ can shed light on the binding of its heavy-quark spin symmetry (HQSS) partner $D^{*}{D}^{*}$ ($I=0$) and on the nature of other heavy hadronic molecule candidates such as $X(3872)$ and $Z_c(3900)$ in the charmed-anticharmed systems. The latter states can be related to $T_{cc}^{+}$ in the meson-exchange potential model with limited assumptions based on the SU(3) flavor symmetry relations. The combined analysis, on the one hand, indicates the HQSS breaking effects among those HQSS partners, and on the other hand, highlights the role played by the short and long-distance dynamics for the near threshold $D^{(*)}{D}^{(*)}$ and $D^{(*)}{\overline{D}}^{(*)}+\mathrm{c}.\mathrm{c}.$ systems.

The stability of the electroweak scale, challenged by the absence of deviations in flavor physics, prompts the consideration of SMEFT scenarios governed by approximate SM flavor symmetries. This study examines microscopic theories that match onto a set of $U(3{)}^5$-symmetric dimension-6 operators. Renormalization group (RG) mixing from the ultraviolet to the electroweak scale yields significant phenomenological constraints, particularly pronounced for UV-motivated directions. To demonstrate this, we explore a complete suite of tree-level models featuring new spin-0, spin-$1/2$, and spin-1 fields, categorized by their irreducible representations under the flavor group. We find that for the leading directions, corresponding to a single-mediator dominance, RG mixing effects occasionally serve as the primary indirect probe.

With some explicitly $Z_3$ breaking terms in the NMSSM (next-to-minimal supersymmetric standard model) effective superpotential and scalar potential, domain walls (DWs) from spontaneously breaking of the discrete symmetry in approximate $Z_3$-invariant NMSSM can collapse and lead to observable stochastic gravitational wave (GW) background signals. In the presence of a hidden sector, such terms may originate from the geometric superconformal breaking with holomorphic quadratic correction to frame function when the global scale-invariant superpotential is naturally embedded into the canonical superconformal supergravity models. The smallness of such mass parameters in the NMSSM may be traced back to the original superconformal invariance. Naive estimations indicate that a SUSY explanation to muon $g-2$ anomaly can have tension with the constraints on SUSY by pulsar timing arrays data, because large SUSY contributions to $\mathrm{\Delta }{a}_{\mu }$ in general needs relatively light superpartners while present ${\mathrm{\Omega }}_{gw}^0$ can set the lower bounds for $m_{\mathrm{soft}}$. We calculate numerically the signatures of GWs produced from the collapse of DWs and find that the observed nHZ stochastic GW background by NANOGrav, etc., can indeed be explained with proper tiny values of $\chi m_{3/2}\sim {10}^{-14}\mathrm{eV}$ for $\chi S^2$ case (and $\chi m_{3/2}\sim {10}^{-10}\mathrm{eV}$ for $\chi H_u{H}_d$ case), respectively. Besides, there are still some parameter points, whose GW spectra intersect with the NANOGrav signal region, that can explain the muon $g-2$ anomaly to $1\sigma$ range.

We investigate neutrino magnetic moment, triplet scalar dark matter in a type II radiative seesaw scenario. With three vectorlike fermion doublets and two scalar triplets, we provide a loop level setup for the electromagnetic vertex of neutrinos. All the scalar multiplet components constitute the total dark matter abundance of the Universe and also their scattering cross section with detector lie below the experimental upper limit. Using the consistent parameter space in dark matter domain, we obtain light neutrino mass in sub-eV scale and also magnetic moment in the desired range. We further derive the constraints on neutrino transition magnetic moments, consistent with the XENONnT limit.

Axion-pion scattering amplitudes at finite temperatures are calculated within chiral perturbation theory up to the one loop level. Unitarization procedure is implemented to these amplitudes in order to extend the applicable range of energy and temperature. The influence of the thermal axion-pion scattering amplitudes on the $a\pi \to \pi \pi$ cross sections and the axion thermalization rate is investigated, with the emphasis on the comparison with the zero-temperature-amplitude case. A brief discussion on the cosmological implication of the axion thermalization rate, which is calculated by using the $a\pi \to \pi \pi$ amplitudes at finite temperatures, is also given. The thermal corrections to the axion-pion scattering amplitudes can cause around a 10% shift of the determination of the axion decay constant $f_a$ and its mass $m_a$, comparing with the results by using the $a\pi \to \pi \pi$ amplitudes at zero temperature.

Since many of the dark-sector particles interact with Standard Model (SM) particles in multiple ways, they can appear in experimental facilities where SM particles appear in abundance. In this study, we explore a particular class of longer-lived mediators that are dominantly produced from photons and charged mesons that arise in proton-beam fixed-target-type neutrino experiments. This class of mediators encompasses light scalars that appear in theories like extended Higgs sectors, muon(electro)philic scalars, etc. We evaluate the sensitivities of these mediators at beam-based neutrino experiments such as the finished ArgoNeuT, ongoing MicroBooNE, SBND, ICARUS, and the upcoming DUNE experiment. We find that muonphilic scalars are more enhanced while produced from three-body decay of charged mesons. The above-mentioned experiments can probe unexplored regions of parameter space that can explain the current discrepancy in the anomalous magnetic moment of muons. We further find that Compton-like scattering of photons is the largest source of electrophilic scalars. By utilizing this, the DUNE Near Detector can explore new regions in the sensitivity space of electrophilic scalars. We also show that Bethe-Heitler scattering processes can be used to probe flavor-specific lepton final states even for the mediator masses below twice the lepton mass.

Charged lepton flavor violation (cLFV) processes, potentially important for various beyond the Standard Model physics scenarios are analyzed in the Standard Model effective field theory framework. We consider the most relevant two-quark–two-lepton $(2q2\ell )$ operators for the leptonic and semileptonic LFV $B$-decay (LFVBD) processes $B_s\to {\mu }^{+}{e}^{-},B^{+}\to K^{+}{\mu }^{+}{e}^{-},B^0\to K^{*0}{\mu }^{+}{e}^{-}$, and $B_s\to \varphi {\mu }^{-}{e}^{+}$. We analyze the interplay among the Wilson coefficients responsible for these LFVBDs and other cLFV processes, like $\mathrm{CR}(\mu \to e)$, ${\ell }_i\to {\ell }_j\gamma$, ${\ell }_i\to {\ell }_j{\ell }_k{\ell }_m$, and $Z\to {\ell }_i{\ell }_j$, to find the maximal possible LFV effects in $B$-meson decays. We probe the scale of new physics in relation to the constraints imposed by both classes of the LFV decays while considering both the present bounds and future expectations. In view of proposed experiments at LHCb-II and Belle II to study charged LFV processes, we have also provided the upper limits on the indirect constraints on such LFVBDs. For the processes where the $B$ meson is decaying to ${\mu }^{\pm }$ and $e^{\mp }$, we show that new physics can be constrained by an enhancement of 2–4 orders of magnitude on the current sensitivities of the branching ratios of $B^{+}\to K^{+}{\mu }^{+}{e}^{-},B^0\to K^{*0}{\mu }^{+}{e}^{-}$, and $B_s\to \varphi {\mu }^{\pm }{e}^{\mp }$.

It was found that isoscalar-scalar and isovector-scalar mesons play significant roles in nuclear matter physics. However, the underlying structures of these resonances are not yet well understood. We construct a three-flavor baryonic extended linear sigma model including both the two- and four-quark constitutes of scalar mesons with respect to the axial transformation and study the nuclear matter properties with the relativistic mean field method. The nuclear matter properties at saturation density and hadron spectra are well reproduced with this model simultaneously, and only the two-quark component of the scalar mesons couples to baryon fields and dominates the nuclear force. A plateaulike structure is found in the symmetry energy of nuclear matter due to the multimeson couplings, and it is crucial for understanding the neutron skin thickness of ${}^{208}\mathrm{Pb}$ and the tidal deformation of neutron star from GW170817. At high-density regions, vector mesons are found to be rather crucial, especially the ones coupling with four-quark configurations. This model can be easily extended to study neutron stars, even with hyperons in their interior.

The ${\gamma }^{*}N\to N(1520)$ transition has a property that differs from the other low-lying nucleon resonance amplitudes: the magnitude of the transverse helicity amplitudes. The transition helicity amplitudes are defined in terms of square-transfer momentum $q^2$, or $Q^2=-q^2$. Near the photon point ($Q^2=0$) there is a significant difference in the magnitude of the transverse amplitudes: $A_{3/2}$ is very large and $A_{1/2}$ is very small. This atypical behavior contrasts with the relation between the amplitudes at the pseudothreshold [the limit where the nucleon and the $N(1520)$ are both at rest and $Q^2<0$], where $A_{3/2}=A_{1/2}/\sqrt{3}$, and also in the large-$Q^2$ region, where theory and data suggest that $A_{3/2}$ is suppressed relative to $A_{1/2}$. In the present work, we look for the source of the suppression of the $A_{1/2}$ amplitude at $Q^2=0$. The result is easy to understand in first approximation, when we look into the relation between the transverse amplitudes and the elementary form factors, defined by a gauge-invariant parametrization of the ${\gamma }^{*}N\to N(1520)$ transition current, near $Q^2=0$. There is a partial cancellation between contributions of two elementary form factors near $Q^2=0$. We conclude, however, that the correlation between the two elementary form factors at $Q^2=0$ is not sufficient to explain the transverse amplitude data below $Q^2=1{\mathrm{GeV}}^2$. The description of the dependence of the transverse amplitudes on $Q^2$ requires the determination of the scale of variation of the elementary form factors in the range $Q^2=0\dots 0.5{\mathrm{GeV}}^2$, a region with almost nonexistent data. We conclude at the end that the low-$Q^2$ data for the transverse amplitudes can be well described when we relate the scale of variation of the elementary form factors with the nucleon dipole form factor.

Built on the seminal works by Jackson-Treiman-Wyld and Ebel-Feldman, we derive the most general free neutron differential decay rate where all massive particles (neutron, proton, and electron) are polarized. This introduces 33 new correlations in addition to the 18 existing ones, which overconstrain the coupling constants in the low-energy effective field theory of charged weak interactions, and thus provides stringent tests of the validity of the theory framework itself. We classify the correlation coefficients in terms of their Standard Model limit and discrete symmetries, and study their expansion with respect to the new physics coupling strengths, supplemented by the experiment-independent $\mathcal{O}(\alpha )$ virtual electromagnetic radiative corrections.

Based on a sample of $(448.1\pm 2.9)\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector at BEPCII, the decays of $\psi (3686)\to K^{-}\mathrm{\Lambda }{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$ with ${\overline{\mathrm{\Xi }}}^{+}\to \overline{\mathrm{\Lambda }}{\pi }^{+}$, $\overline{\mathrm{\Lambda }}\to \overline{p}{\pi }^{+}$ are studied. We investigate the two excited resonances, $\mathrm{\Xi }(1690{)}^{-}$ and $\mathrm{\Xi }(1820{)}^{-}$, which are each observed with large significance ($\gg 10\sigma$) in the $K^{-}\mathrm{\Lambda }$ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of $\mathrm{\Xi }(1690{)}^{-}$ and $\mathrm{\Xi }(1820{)}^{-}$ are measured to be ${\frac{1}{2}}^{-}$ and ${\frac{3}{2}}^{-}$, respectively. The masses, widths, and product branching fractions of $\mathrm{\Xi }(1690{)}^{-}$ and $\mathrm{\Xi }(1820{)}^{-}$ are also measured.

It has been long conjectured that a signature of quantum gravity will be Lorentz invariance violation (LIV) that could be observed at energies much lower than the Planck scale. One possible signature of LIV is an energy-dependent speed of photons. This can be tested with a distant transient source of very high-energy photons. We explore time-of-flight limits on LIV derived from LHAASO’s observations of tens of thousands of TeV photons from GRB 221009A, the brightest gamma-ray burst of all time. For a linear ($n=1$) dependence of the photon velocity on energy, we find a lower limit on the subluminal (superluminal) LIV scale of $5.9(6.2)E_{\mathrm{pl}}$. These are comparable to the stringent limits obtained so far and as an independent bound obtained from a different redshift confirm their robustness. For a quadratic model ($n=2$, corresponding to $d=6$ SME operators), the limits, which are currently the best available with the time-of-flight method, are $5.8(4.6)\times {10}^{-8}{E}_{\mathrm{pl}}$. Our analysis uses the LHAASO data in the 0.2–7 TeV range. Higher energy data would enable to improve our limits.

We calculate exclusive $\mathrm{J}/\psi$ photoproduction at high energies in the color glass condensate approach. The results are compared to the center-of-mass energy dependent $\gamma +A\to \mathrm{J}/\psi +A$ cross sections extracted from measurements in ultraperipheral heavy ion collisions at RHIC and LHC. We predict strong saturation-driven nuclear suppression at high energies, while LHC data prefer even stronger suppression. We explore effects of nucleon shaped fluctuations and show that the most recent measurement of the $|t|$-differential incoherent $\mathrm{J}/\psi$ cross section prefers large event-by-event fluctuations of the nucleon substructure in heavy nuclei, comparable to that found for a free proton.