The search for the particle identity of dark matter (DM) continues to be a primary objective in modern physics. In this field, the sub-GeV mass range of DM detection remains a crucial yet challenging window. We investigate synchrotron self-Compton (SSC) emission from electrons and positrons produced by MeV-scale DM annihilation as a novel indirect detection channel. Focusing on the globular cluster Omega Centauri and the sensitivity of the Square Kilometre Array, we derive constraints on the annihilation cross section reaching $⟨\sigma v⟩\sim {10}^{-29}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ in the tens-of-MeV range. Furthermore, constraints can reach below $⟨\sigma v⟩\sim {10}^{-30}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ under favorable parameter choices. Although the derived limits depend on the uncertain propagation parameters, the SSC channel remains competitive with existing indirect constraints over a representative range of astrophysical assumptions, establishing SSC emission as a promising probe of sub-GeV DM.

We study how rotation modifies the constraints on MeV-scale axionlike particles (ALPs) coupled to photons derived from SN 1987A. We constrain the ALP parameter space based on both the energy-loss argument and the gamma-ray limits and examine how these constraints are affected by stellar rotation. Adopting initial angular velocities of ${\mathrm{\Omega }}_0=0.0$ and $1.0\mathrm{rad}{\mathrm{s}}^{-1}$ in the iron core, we carry out two-dimensional core-collapse supernova simulations for three progenitor models—a $14+9M_{\odot }$ binary and $13M_{\odot }$ and $18M_{\odot }$ single stars with solar metallicity—and estimate ALP emission rates through postprocessing. We find that rotation suppresses ALP emission by reducing the core temperature via centrifugal support. Rotation also reduces the neutrino luminosity, but the suppression of ALP emission is more effective, leading to relaxed constraints within a criterion based on the energy-loss argument. This relaxation is particularly pronounced in the rotating $18M_{\odot }$ model, where a substantial decrease in the central temperature occurs at $t_{\mathrm{pb}}=0.8–1\mathrm{s}$. In this criterion, such rapid temporal variations in temperature indicate that the resulting constraints depend sensitively on both the evaluation time and the underlying supernova model. For a gamma-ray limit from the SN 1987A observation, rotation has a negligible impact on the constraint. This is because the ALP-induced gamma-ray fluence observed at Earth is proportional to the fourth power of the ALP-photon coupling constant, making the constraint relatively insensitive to the rotational suppression of ALP emission.

Axions and axionlike particles (ALPs) are compelling candidates for dark matter and new physics beyond the Standard Model. Photon-axion mixing in external magnetic fields not only modifies the photon energy spectrum and linear polarization state but also induces circular polarization signals. Compared to spectral and linear polarization methods, circular polarization benefits from lower astrophysical background contamination and weaker dependence on the intrinsic source spectrum, providing an independent probe for axion searches. In this work, we study the circular polarization induced by photon-axion mixing within the chiral basis framework. By analytically solving the evolution equations under the single-domain approximation, we derive an expression for the circular polarization degree $P_C$, applicable in the resonant, strong coupling, and weak coupling regimes. The opposite-phase coupling of the axion field to left- and right-handed circular polarization components generates phase differences and intensity asymmetries, thereby converting initially linearly polarized light into nonzero circular polarization signals. Within single-domain magnetic field models, we compare the energy-dependent circular polarization in four astrophysical environments (active galactic nucleus jets, the intracluster medium, the intergalactic medium, and the Galactic magnetic fields). We find that the x-ray to MeV band represents the most sensitive observational window for axion-induced circular polarization signals. In multidomain propagation models, using the blazar S4 $0954+65$ as a case study, phase accumulation in random magnetic domains causes the circular polarization degree to fluctuate with redshift and exhibit pronounced energy structures in the x-ray to MeV band. Using the optical circular polarization upper limit $P_C<0.184\%$ (measured in the z-SDSS band) from this source, we statistically constrain $g_{a\gamma \gamma }\lesssim 3\times {10}^{-11}{\mathrm{GeV}}^{-1}$ (95% confidence level) for $m_a\sim {10}^{-16}-{10}^{-10}\mathrm{eV}$, with the strongest constraint reaching $g_{a\gamma \gamma }\sim 6\times {10}^{-12}{\mathrm{GeV}}^{-1}$ near $m_a\sim {10}^{-14}\mathrm{eV}$. These results establish circular polarization as a complementary axion probe, and future high-energy circular polarization observations are expected to further strengthen constraints on the ultralight axion parameter space.

We propose a conjectured formula that systematically maps covariant off-shell amplitudes to light-cone wave functions in scalar field theory. Through an explicit comparison at one-loop accuracy, we establish its equivalence to the light-cone perturbation theory series, thereby validating the conjecture at this order. Applying this formula, we efficiently rederive wave functions from known covariant amplitudes, bypassing both the conceptual complexities of light-cone quantization and the technical challenges of perturbative calculations in this framework. In addition to simplifying computations, this approach opens new avenues for applications in gauge theories and deeper explorations of the fundamental equivalence between covariant and light-cone quantization.

We present a self-consistent framework for heavy-quark transport in the quark-gluon plasma across the QCD crossover region. By synthesizing perturbative and nonperturbative interactions into a unified interaction kernel, we circumvent the traditional reliance on arbitrary soft-hard momentum separation scales. The interaction is governed by an in-medium effective potential, incorporating short-range Yukawa screening and long-range confining string contributions, both rigorously constrained by the latest lattice QCD data. Our results reveal that the nonperturbative string tension is indispensable for capturing the extreme opacity of the medium near the critical temperature $T_c$. Specifically, our model predicts a spatial diffusion coefficient of $2\pi T{D}_s\approx 0.5\sim 1.7$, demonstrating a striking quantitative agreement with the recent lattice QCD extractions. Ultimately, our results provide a robust dynamical interpretation of the strong heavy-quark coupling near the QCD crossover and offer a unified framework for describing heavy-flavor transport in hot and dense QCD matter.

A broad experimental program is targeting the QCD axion band predicted by single-axion solutions to the strong $CP$ problem. Multiaxion theories provide a well-motivated departure from this canonical picture, since additional states generically modify the mass-photon-coupling relation. We investigate the general structure of multiaxion solutions to the strong $CP$ problem and study the different qualitative mass-coupling patterns that arise, including axions to the right of the QCD band, axions in the experimentally accessible region to its left, and scenarios in which the QCD axion band itself is displaced. This general treatment reveals a broad set of phenomenological possibilities that are not captured by more restrictive assumptions. In particular, we identify the structure of Peccei-Quinn (PQ) symmetry breaking and the relative alignment between the QCD and electromagnetic anomalies as key ingredients determining the location of the axions in parameter space. Combining these ingredients, we derive a general sum rule for $N$-axion systems that incorporates both general PQ breaking and nonuniversal anomaly coefficients. We apply the framework to the two-axion system and to general multiaxion setups, identifying UV-complete theories in which the different phenomenological regimes arise naturally. Our results motivate an extended axion search program and have implications for our understanding of fundamental physics and the ultraviolet completion of the Standard Model.

We propose our framework as an effective field theory valid below the cutoff scale $\mathrm{\Lambda }$, in which we explain the tiny scale of neutrino masses by integrating a noninvertible symmetry with the dynamical determination of the cutoff scale. In our model, we introduce three families of ${\mathrm{SU}(2)}_L$ quintet fermions (${\mathrm{\Sigma }}_R$) and a quartet scalar (${\varphi }_4$), both of which are charged under the Fibonacci fusion rule (FFR). A central feature of this construction is that the vacuum expectation value (VEV) $v_4$ of ${\varphi }_4$ is induced at the one-loop level via dynamical symmetry breaking. To resolve the inherent arbitrariness of the cutoff scale $\mathrm{\Lambda }$ in loop-induced VEV models, we identify $\mathrm{\Lambda }$ with the scale at which the $SU(2{)}_L$ gauge coupling $g_2$ encounters the renormalization group evolution (RGE) of $g_2$, naturally fixing the physical cutoff within the range of approximately ${10}^5$ to ${10}^7\mathrm{GeV}$. Quantitatively, this framework yields $v_4\sim 0.07–0.1\mathrm{GeV}$, which in turn leads to neutrino Yukawa couplings on the order of ${10}^{-3}$. This result provides a significantly more natural explanation for the neutrino mass hierarchy compared to standard seesaw models, which typically require couplings as small as ${10}^{-6}$ or less. Notably, our approach maintains a relatively simple particle content and does not necessitate additional (gauge) bosons for symmetry breaking.

We present results for the inclusive semileptonic $D_s\to X_s\ell \overline{\nu }$ decay rate from lattice QCD. Chiral and continuum extrapolations are performed using gauge ensembles generated with $2+1$ flavors of Möbius domain-wall fermions. Systematic errors are fully addressed including those from the integral over all possible final states. Our results are in agreement with currently available experimental data, with an error at the few-percent level.

The quest to understand three-body dynamics from first-principle QCD includes the study of nonresonant and resonant systems. The isospin $I=2$ system is of particular interest having no three-body resonance but featuring a resonance in a subchannel, while also being a coupled-channel problem. In this study, we calculate the finite-volume spectrum from lattice QCD at two different pion masses, map the amplitude to the infinite volume through a generalized Finite-Volume Unitarity three-body quantization condition, investigate the limit of a narrow $\rho$, and compare with an effective Lagrangian prediction at leading order. Chiral extrapolations between different pion masses are performed.

We present the first lattice QCD calculation of single-channel $DD$ scattering with quantum numbers $I(J^P)=1(0^{+})$ and $0(1^{-})$. The calculation is performed on the $2+1$ flavor Wilson-Clover ensembles with a lattice spacing $a\simeq 0.077\mathrm{fm}$ and two different pion masses, $m_{\pi }\simeq 207$ and 305 MeV. The scattering parameters are determined using the Lüscher finite-volume method. Our results indicate a weak repulsive interaction in the $1(0^{+})$ channel and a slightly attractive interaction in the $0(1^{-})$ channel. The $S$-wave isovector $DD$ scattering length and effective range, extrapolated to the physical pion mass, are $(-0.25\pm 0.08\pm 0.12)\mathrm{fm}$ and $(-5.7\pm 4.5\pm 1.7)\mathrm{fm}$, respectively.

Transverse spherocity ($S_0$) is an event-shape observable widely used to classify collision events according to their topology, particularly to distinguish jetlike from isotropic events. Low-spherocity events are generally interpreted as being associated with enhanced jet activity. This event classification has also been applied to heavy-ion collisions to investigate the influence of event topology on several observables, including elliptic flow and constituent-quark-number scaling [N. Mallick et al., J. Phys. G 48, 045104 (2021).; S. Prasad et al., Phys. Rev. D 107, 074011 (2023).; N. Mallick et al., Eur. Phys. J. C 82, 524 (2022).; S. Sarkar et al., Eur. Phys. J. A 58, 139 (2022).; S. Prasad et al., Sci. Rep. 12, 3917 (2022).]. In this work, we demonstrate that such an interpretation requires careful reconsideration. Using toy Monte Carlo simulations, a multiphase transport (AMPT) model calculations, and an analytical formulation of the spherocity observable, we show that transverse spherocity is intrinsically related to the elliptic flow coefficient, $v_2$. This connection arises because the axis that minimizes the spherocity aligns with the event symmetry plane, causing events with larger elliptic anisotropy to naturally exhibit smaller spherocity values even in the absence of genuine jetlike topologies. We further show that this intrinsic relation gives rise to an inherent anticorrelation between transverse spherocity and $v_2$, implying that several characteristics previously attributed to the enhanced jetlike nature of low-spherocity events in heavy-ion collisions can instead be understood as consequences of collective anisotropic flow. Our results indicate that, in heavy-ion collisions, transverse spherocity should be interpreted primarily as a probe of the collective momentum-space anisotropy rather than as a direct measure of jetty event topology. Consequently, physics conclusions drawn from spherocity-selected events should explicitly account for its intrinsic correlation with elliptic flow.

We employ a symmetry-preserving treatment of the contact interaction within the coupled formalism of Schwinger-Dyson and Bethe-Salpeter equations to calculate the elastic form factors of axial-vector mesons. In this study, we present the computation of the charge radii, magnetic moments, and quadrupole moments of axial-vector mesons, including those composed of light quarks, heavy quarks, or a light and a heavy quark. Our findings indicate that the electric form factor for axial-vector mesons, like that of vector mesons, crosses zero. Furthermore, this crossing occurs at a lower value for axial-vector mesons than for vector mesons. The results for vector-axial mesons follow a similar hierarchy in charge radii as observed for scalar, pseudoscalar, and vector mesons, with radii decreasing as the mass of the dressed quarks increases. We also include a term associated with the anomalous magnetic moment in the quark-photon vertex. This term has a noticeable impact on both the axial-vector magnetic moment and quadrupole moment, leading to significant percentage changes in their values. We compare our results with those obtained from other models whenever available.

We investigate the modification of the $J/\psi$ meson mass in asymmetric nuclear matter at zero and finite temperatures employing an effective Lagrangian approach that considers the contributions of $DD$ and $D{D}^{*}$ meson loops. The medium dependence of $D$ meson masses is determined using the hadronic chiral SU(3) model, where scalar condensates are calculated and subsequently utilized in the QCD sum rules approach. Our findings indicate that an increase in baryonic density results in a negative mass shift of the $J/\psi$ meson. This suggests that the $J/\psi$ meson is attracted to nuclear mean fields indicating the possibility of the formation of meson-nucleus bound states. Moreover, we have also determined the binding energy and absorption decay width of the $J/\psi$ meson for both the ground and excited states of ${\mathrm{O}}^{16}$, ${\mathrm{Ca}}^{40}$, ${\mathrm{Zr}}^{90}$, and ${\mathrm{Pb}}^{208}$ nuclei. These results are expected to contribute to the understanding of experimental data from upcoming studies at Jefferson lab and the facility for antiproton and ion research, where low-momentum charmed mesons can be produced and examined within nuclei.

We compare the isospin-one, vector-current hadronic vacuum polarization (HVP) obtained from isospin-symmetric lattice QCD with that obtained from a dispersive representation employing inclusive hadronic $\tau$ decay data corrected for isospin breaking. We consider the subtracted HVP evaluated at squared Euclidean momenta ranging from $0.5{\mathrm{GeV}}^2$ to $12{\mathrm{GeV}}^2$, together with the light-quark-connected HVP contribution to the muon anomalous magnetic moment and the short-, intermediate- and long-distance RBC/UKQCD window components thereof. Dispersive contributions from the region of hadronic invariant masses above the $\tau$ mass are evaluated using perturbative QCD. We also consider dispersive determinations using $\tau$ data only for contributions from two-pion, or two-pion and four-pion, modes, and evaluating the remaining contributions using exclusive-mode $e^{+}{e}^{-}\to \text{hadrons}$ cross sections up to about 2 GeV, lessening the dependence on perturbation theory. We find generally good agreement between lattice and $\tau$-based results. However, a comparison of $\tau$-based window-quantity contributions for the two four-pion modes to expectations for those contributions based on the Pais relations and $e^{+}{e}^{-}$ four-pion cross sections, reveals significant differences for the $2{\pi }^{-}{\pi }^{+}{\pi }^0$ mode.

The multiplicity distribution of charged particles produced in the central rapidity region ($|\eta |<2.5$) is calculated within the multichannel eikonal model using the Abramovsky-Gribov-Kancheli cutting rules and compared with ATLAS data at $\sqrt{s}=7$ and 13 TeV. The effects of color reconnection and/or string percolation are discussed.

We develop a bottom-up formulation of spin-kinetic theory for hot and/or dense plasmas relevant for matter created in a heavy-ion collision. We introduce scalar and axial-vector phase-space functions as dynamical variables that parametrize both spin-averaged and spin-dependent distribution functions. Using spin-dependent Poisson brackets, we derive the corresponding kinetic equations and construct the associated Schwinger-Keldysh action. We further demonstrate how physical observables can be expressed in terms of these dynamical variables through constitutive relations. In the linear response regime, we establish a precise matching between the kinetic-theory and field-theory descriptions of vector and axial Wigner functions under electromagnetic and gravitational perturbations. Our framework provides a complementary approach to describing the dynamics of spin effects in a medium.

We explore the potential for extracting proton structure functions, proton parton density functions (PDFs), and the strong coupling ${\alpha }_s(M_z^2)$, using early science data from the future Electron-Ion Collider (EIC), both stand-alone, and in combination with data from the Hadron-Electron Ring Accelerator (HERA). Different scenarios are considered in which samples with modest luminosity are collected at either two or three EIC beam energy configurations. The Rosenbluth separation method is used to extract the proton structure functions $F_2$ and $F_L$ from simulated data in a model-independent manner, showing that $F_L$ can be extracted significantly more precisely with three center-of-mass energies than with two, whilst also obtaining $F_2$ to higher precision than has been achieved previously. The inclusion of a third beam configuration is also beneficial in the extraction of the strong coupling ${\alpha }_s(M_z^2)$ that is obtainable with unprecedented experimental precision with the early EIC data. Additionally, the precision of the proton PDFs is improved when adding these data, especially for large values of Bjorken-$x$, for both two and three EIC beam energy configurations. These studies show that EIC data will already be a highly competitive probe of perturbative quantum chromodynamics within the first five years of data taking.

The existence of a new spin-zero particle with a mass below the electroweak scale is predicted by several theoretical models. Searches for resonant production of photon pairs at the LHC are able to probe these models. We present a search for a narrow resonance produced through gluon fusion that decays into a pair of photons with an invariant mass between 10 and 70 GeV, using a proton-proton collision dataset from the CMS experiment. This dataset, corresponding to an integrated luminosity of $54.4{\mathrm{fb}}^{-1}$, was recorded in 2018 at a center-of-mass energy of 13 TeV using a newly introduced diphoton trigger that enabled exploration of the low-mass diphoton spectrum. No significant excess above the expected background is observed. Upper limits are set on the product of the gluon fusion production cross section and the branching fraction of the diphoton decay of a narrow resonance. An interpretation of these limits within an effective field theory framework for axionlike particles is also provided.

We investigate operator growth in a Brownian spin Sachdev-Ye-Kitaev (SYK) model with random all-to-all interactions, focusing on the full operator-size distribution. For Hamiltonians containing $q$-body interactions, we derive a closed master equation for the Pauli-string expansion coefficients and recast their dynamics into a generating-function formulation suitable for the large-$N$ limit. This approach allows us to diagonalize the leading-order evolution operator explicitly and obtain exact solutions for arbitrary initial operator distributions, including the effects of decoherence. Going beyond leading order, we develop a systematic $1/N$ expansion that captures higher-order corrections to the operator-size dynamics and the late-time behavior. Our results demonstrate that higher-order effects play a crucial role in operator scrambling and that the full operator-size distribution provides a more refined probe of quantum chaos in Brownian and open quantum systems.

We study Euclidean wineglass wormholes, which mediate the nucleation of inflationary spacetimes from an existing spacetime with asymptotically flat or anti–de Sitter regions. These wormholes are distinguished by the presence of a local maximum of the scale factor, which allows the analytically continued Lorentzian spacetime to expand after materialization. We present explicit numerical wormhole solutions supported either by an axionic field or a magnetic gauge field, in both cases in conjunction with a self-interacting scalar field. More exotic solutions, with multiple extrema of the scale factor, are also described. As we discovered recently, in the limit of small axionic or magnetic charge, wineglass wormhole solutions split into two separate geometries, one being the background spacetime and the other a disconnected no-boundary instanton. We study the associated topology changing transition in detail and provide an extensive discussion of both the properties and puzzles exhibited by this common family of wineglass/no-boundary instantons.