Searches for continuous gravitational waves from isolated compact objects and those in binary systems aim to detect nonaxisymmetric, deformed neutron stars at particular locations in the Galaxy or all sky. However, a large fraction of known pulsars have rotational frequencies that lie outside the audio frequency band, rendering current detectors insensitive to these pulsars. In this work, we show that DECIGO, a future space-based decihertz gravitational-wave interferometer, will be sensitive to severely deformed compact objects, e.g., hybrid stars, neutron stars, or magnetars. We estimate the number of possible compact objects that could be detected with such high deformations, both via their individual continuous gravitational-wave emission and the stochastic gravitational-wave background created by a superposition of gravitational waves from the $\sim {10}^8$ compact objects in the Galaxy. Furthermore, we show that the existence of such compact objects could be probed across a wide parameter space at a fraction of the computational cost of current searches for isolated compact objects and those in binary systems. For known pulsars, we will be able to both beat the spin-down limit and probe the Brans-Dicke modified theory of gravity parameter $\zeta <1$ for approximately 85% of known pulsars with $f_{\mathrm{gw}}<10\mathrm{Hz}$, the latter of which is currently only possible for $\mathcal{O}(10)$ pulsars. DECIGO will thus open a new window to probe highly deformed compact objects and over half of the known pulsars.

We show that nickel oxide, which is already a very promising target to look for sub-MeV dark matter scattering, can be employed to hunt axion dark matter, with masses in the meV range and couplings to electrons allowing them to potentially be QCD axions. We describe the interactions between axions and the collective excitations of nickel oxide in terms of an effective field theory, built solely out of symmetry arguments. The processes of conversion into one or two excitations provide, respectively, a narrow band and a broadband channel for the axion search, and the possibility of varying an external magnetic field up to a phase transition point allows one to cover a large portion of a yet unexplored parameter space, reaching axion masses down to few fractions of an meV. Our results underline nickel oxide as an ideal candidate for a multipurpose target for light dark matter searches.

We classify radiative corrections to spin polarization into three types: (i) spectral function, (ii) modified distribution function, and (iii) modified Kubo-Martin-Schwinger relation. The last two contributions modify the well-known free theory results. The first contribution is present with radiative correction only. We perform a detailed analysis on the first type for an energetic quark in a medium with hydrodynamic gradients, finding the radiative correction to spectral function leads to a polarized quasiparticle. The degeneracy of spin polarization induced by different hydrodynamic sources in free theory is lifted by radiative correction. We argue that the corrections of the last two types are parametrically suppressed with respect to the first type for the energetic quark we consider.

We present a systematic study of twist-3 generalized parton distributions (GPDs) for $\overline{u}$ and $\overline{d}$ sea quarks in the proton at zero skewness ($\xi =0$) using the light-cone formalism with overlap representation. The proton wave functions are derived from a meson-baryon fluctuation model that incorporates $|q\overline{q}B⟩$ Fock states, providing a natural framework for investigating sea quark contributions. Within this approach, we compute the complete set of twist-3 GPDs and present the numerical results, including both chiral-odd ($H_2$, $E_2$, ${\tilde{E}}_2$, and ${\tilde{H}}_2^{\prime }$) and chiral-even (${\tilde{E}}_{2T}$, $H_{2T}^{\prime }$, $E_{2T}^{\prime }$, and ${\tilde{H}}_{2T}^{\prime }$) distributions for $\overline{u}$ and $\overline{d}$ quarks at zero skewness. By taking the forward limit, we also calculate the corresponding twist-3 parton distribution functions $e(x)$ of $\overline{u}$ and $\overline{d}$ quarks. The kinetic orbital angular momenta of sea quarks deduced from the twist-3 GPDs are studied and compared to those from the twist-2 GPDs.

We search, for the first time, for an exotic molecular state with quantum numbers $J^{PC}=1^{-+}$, called $X$, via the process $e^{+}{e}^{-}\to \gamma D_s^{+}{D}_{s1}^{-}(2536)+\mathrm{c}.\mathrm{c}.$ using data samples corresponding to a luminosity of $5.8{\mathrm{fb}}^{-1}$ across center-of-mass energies from 4.612 to $4.951\mathrm{GeV}$, collected with the BESIII detector operating at the BEPCII Collider. No statistically significant signal is observed. The upper limits on the product of cross section and branching fraction $\sigma (e^{+}{e}^{-}\to \gamma X)·\mathcal{B}(X\to D_s^{+}{D}_{s1}^{-}(2536)+\mathrm{c}.\mathrm{c}.)$ at 90% confidence level are reported for each energy point, assuming the $X$ mass to be $4.503\mathrm{GeV}/c^2$ and the width 25, 50, 75, and $100\mathrm{MeV}$, respectively.

We show that when two toric Calabi-Yau 3-folds and their corresponding toric varieties are related by a birational transformation, they are associated with a pair of dimer models on the 2-torus that define dimer integrable systems, which themselves become birationally equivalent. Under this birational equivalence, the Casimirs and the Hamiltonias as well as the spectral curve and the Poisson structure formed by the cluster variables of the dimer integrable systems are identified to each other. These integrable systems defined by dimer models were first introduced by Goncharov and Kenyon. We illustrate this equivalence explicitly using a pair of dimer integrable systems corresponding to the Abelian orbifolds of the form ${\mathbb{C}}^3/{\mathbb{Z}}_4\times {\mathbb{Z}}_2$ with orbifold action (1, 0, 3)(0, 1, 1) and $\mathcal{C}/{\mathbb{Z}}_2\times {\mathbb{Z}}_2$ with action (1, 0, 0, 1)(0, 1, 1, 0), whose spectral curves and Hamiltonians are shown to be related by a birational transformation.

Field theories exhibit dramatic changes in the structure of their operator algebras in the limit where the number of local degrees of freedom ($N$) becomes infinite. An important example of this is that the algebras associated to local subregions may not be additively generated in the limit. We investigate examples and explore the consequences of this “superadditivity” phenomenon in large $N$ field theories and holographic systems. In holographic examples we find cases in which superadditive algebras can probe the black hole interior, while the additive algebra cannot. We also discuss how superaddivity explains the success of quantum error correction models of holography. Finally we demonstrate how superadditivity is intimately related to the ability of holographic field theories to perform quantum tasks that would naively be impossible. We argue that the connected wedge theorems (CWTs) of May, Penington, Sorce, and Yoshida, which characterize holographic protocols for quantum tasks, can be rephrased in terms of superadditive algebras and use this rephrasing to conjecture a generalization of the CWTs that is an equivalence statement.

We present exact nonperturbative vacuum solutions to chiral gauge theories based on the $E_6$ gauge group and several matter fermions in the fundamental $\mathbf{27}$-dimensional representation. They are obtained when supersymmetric versions are perturbed by small supersymmetry breaking by anomaly mediation. The universality classes obtained are very different from what can be conjectured by the tumbling hypothesis. In particular, the case with three $\mathbf{27}\mathrm{s}$ may have an unbroken SU(3) symmetry with massless composite fermions in $\mathbf{10}$ of SU(3). For this case, we employed numerical techniques to obtain the exact ground state.

We study the conservative dynamics of spinless compact objects in a general effective theory of gravity, which includes a metric and an arbitrary number of scalar fields, through $\mathcal{O}(G^3)$. Departures from Einstein gravity, which preserve general coordinate and local Lorentz invariance, are characterized by higher-derivative terms in a Lagrangian whose coupling constants scale as powers of a “new-physics” length scale, $\ell$. For a purely metric theory we compute the contributions from the leading and subleading higher-curvature curvature corrections. In four dimensions these are cubic and quartic curvature terms, i.e. orders ${\ell }^4$ and ${\ell }^6$. We also study a general multi-scalar-tensor theory of gravity to order ${\ell }^4$, which includes both Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons higher-order couplings. Specifically, we compute the radial action in a post-Minkowskian approximation for scattering orbits to the two-loop order. The result encodes the fully relativistic dynamics of the compact objects and serves as a generating function for gauge-invariant orbital observables for both bound and unbound binary systems. Where overlapping post-Newtonian results are available, we have verified agreement.

In this paper we study gravitationally bound compact objects sourced by a string theory inspired Born-Infeld scalar field. Unlike many of their canonical scalar field counterparts, these “boson stars” do not have to extend out to infinity and may generate compact bodies. We analyze in detail both the junction conditions at the surface as well as the boundary conditions at the center which are required in order to have a smooth structure throughout the object and into the exterior vacuum region. These junction conditions, although involved, turn out to be relatively easy to satisfy. Analysis reveals that these compact objects have a richer structure than the canonical boson stars and some of these properties turn out to be physically peculiar: There are several branches of solutions depending on how the junction conditions are realized. Further analysis illustrates that in practice the junction conditions tend to require interior geometries reminiscent of “bag of gold” spacetimes, and also hide the star behind an event horizon in its exterior. The surface compactness of such objects, defined here as the ratio $2M/r$, can be made arbitrarily close to unity indicating the absence of a Buchdahl bound. Some comments on the stability of these objects are provided to find possible stable and unstable regimes. However, we argue that even in the possibly stable regime the event horizon in the vacuum region shielding the object is potentially unstable, and would cut off the star from the rest of the universe.

We investigate the role of the Higgs field as a fundamental scalar in the Standard Model within the framework of modular inflation models, where a modulus field acts as the inflaton and its interactions are governed by an underlying modular symmetry. In general, the Higgs field can participate in the dynamics of modular inflation, leading to a two-field inflationary system—termed Higgs-Modular inflation—which exhibits nontrivial dynamics and interesting phenomenological implications. We analyze Higgs-Modular inflation both analytically and numerically, highlighting its attractor behavior and the resulting observational constraints. In particular, we find that Higgs-Modular inflation is favored by the latest data release from the Atacama Cosmology Telescope in certain regions of parameter space. This is in contrast to both pure Higgs inflation and pure modular inflation with a Starobinsky-type potential, which tend to predict a relatively low spectral index. Additionally, we discuss the cutoff scale of this inflationary model and the reheating processes induced by the decays of the modulus and the Higgs field.

Observations favor cosmological models with a time-varying dark energy component. But how does dynamical dark energy (DDE) influence the growth of structure in an expanding Universe? We investigate this question using high-resolution $N$-body simulations based on a DDE cosmology constrained by first-year DESI data ($\mathrm{DESIY}1+\mathrm{DDE}$), characterized by a 4% lower Hubble constant ($H_0$) and 10% higher matter density (${\mathrm{\Omega }}_0$) than the Planck-2018 $\mathrm{\Lambda }$ cold dark matter model. We examine the impact on the matter power spectrum, halo abundances, clustering, and baryonic acoustic oscillations (BAOs). We find that $\mathrm{DESIY}1+\mathrm{DDE}$ exhibits a 10% excess in power at small scales and a 15% suppression at large scales, driven primarily by its higher ${\mathrm{\Omega }}_0$. This trend is reflected in the halo mass function: $\mathrm{DESIY}1+\mathrm{DDE}$ predicts up to 70% more massive halos at $z=2$ and a 40% excess at $z=0.3$. Clustering analysis reveals a 3.71% shift of the BAO peak toward smaller scales in $\mathrm{DESIY}1+\mathrm{DDE}$, consistent with its reduced sound horizon compared to Planck18. Measurements of the BAO dilation parameter $\alpha$, using halo samples with DESI-like tracer number densities across $0<z<1.5$, agree with the expected $\mathrm{DESIY}1+\mathrm{DDE}\text{−}\mathrm{to}\text{−}\mathrm{Planck}18$ sound horizon ratio. After accounting for cosmology-dependent distances, the simulation-based observational dilation parameter closely matches DESI Y1 data. We find that the impact of DDE is severely limited by current observational constraints, which strongly favor cosmological models—whether including DDE or not—with a tightly constrained parameter ${\mathrm{\Omega }}_0{h}^2\approx 0.143$, within 1%–2% uncertainty. Indeed, our results demonstrate that variations in cosmological parameters, particularly ${\mathrm{\Omega }}_0$, have a greater influence on structure formation than the DDE component alone.

In the present work, we study the reactions $D^0\to K^{+}{K}^{-}\eta$ and $D^0\to {\pi }^{+}{\pi }^{-}\eta$, and find that the $a_0(980)$ state plays a dominant role. At the quark level, the external and internal $W$-emission mechanisms are taken into account, which can hadronize into the final states, and then the $a_0(980)$ state is generated from the final state interaction. In addition, the contributions of other intermediate resonances, such as $\rho (770)$ and $\varphi (1020)$, are also considered. We make a combined fit of the invariant mass spectra measured by the Belle and BESIII Collaborations, where the results are in good agreement with the experiments, and the signal of $a_0(980)$ shows great significance. Furthermore, the antisymmetry data for the production of $a_0(980{)}^{+}$ and $a_0(980{)}^{-}$ are described well in the combined fit.

We explore a Kim-Shifman-Vainshtein-Zakharov-like extension of the Standard Model with a Dirac fermion and three right-handed neutrinos. Peccei-Quinn (PQ) symmetry allows the Dirac mass for neutrinos and prevents the Majorana mass. A ${\mathcal{Z}}_2$ symmetry guarantees the stability of Dirac fermion dark matter. The breakdown of PQ symmetry generates the QCD axion at a high scale. The fermion dark matter relic abundance arises from the UV-freeze-in mechanism through the axion portal. We determine the fermion dark matter (DM) relic by solving the coupled Boltzmann equations and finding the allowed parameter space using the relic density constraints. Having determined the allowed parameter space for fermion DM, we also look for nonthermal axion production schemes to seek the two DM possibility. We find that feebly interacting massive particles alone is a suitable dark matter that is not excluded while considering several current bounds and future sensitivities on axions and dark matter. Our study highlights the interlinking of dark matter, axions, and neutrinos while addressing the strong $CP$ problem and small neutrino masses.

Effective field theory is an effective approach to parametrizing effects of high energy scale physics in low-energy measurements. The two popular frameworks for physics beyond the standard model are the so-called standard model effective field theory (SMEFT) and the Higgs effective field theory (HEFT). While the description by the SMEFT deteriorates when the scale of new physics is not so high or it participates in spontaneous electroweak symmetry breaking, the HEFT makes use of nonlinear realization of spontaneously broken symmetry in which there are practically no restrictions on the Higgs field as a singlet. In this work we present another framework, called broken phase effective field theory (bEFT), in which we deal directly with mass eigenstate fields after spontaneous symmetry breaking without employing nonlinear realization. We take the type-II seesaw model as an example to demonstrate our approach. By matching the model to both the bEFT and the SMEFT at tree level, we compare the results for two processes, the Higgs pair production via vector boson fusion which appears as a subprocess at the LHC and the Higgs-strahlung process at a future electron-positron collider. We find that the bEFT reproduces the type-II seesaw model more accurately than the SMEFT in the regions where the bare mass of the Higgs triplet becomes close to the electroweak scale. Therefore, the bEFT serves as a useful framework that can compensate for the shortcomings in both the SMEFT and the HEFT when dealing with UV models that involve Higgs mixing or new particles with a mass close to the electroweak scale.

The nondetection of dark matter may be attributed to the dark matter residing in a darker hidden sector. We explore the possibility that a hidden sector produced through the freeze-in mechanism, can further generate an even more hidden sector via an additional freeze-in process. Such a two-step freeze-in process produces dark matter coupled weaker-than-ultraweakly to the standard model particles, and is thus referred to as the “darker matter.” To illustrate the two-step freeze-in process, we study a model featuring two $U(1)$ hidden sectors. The first $U(1)$ sector is directly coupled to the standard model with feeble interactions, while the second $U(1)$ sector is directly coupled to the first $U(1)$ sector and thus only indirectly to the standard model, rendering it darker. Remarkably, darker matter candidates residing in the second darker $U(1)$ sector, generated from the two-step freeze-in process, can account for almost the entire observed dark matter relic density. The darker matter, interacted with standard model particles through ultraweak couplings, can exhibit velocity-dependent self-interacting cross sections, which potentially provides an explanation for addressing problems associated with cosmic small-scale structures. Additionally, the dark photon darker matter residing in the darker hidden sector can be responsible for the galactic 511 keV photon signal, consistent with various dark matter density profiles.

Firmly established in astrophysical observations, dark matter evades direct detection in experiments. Axions and axionlike particles are among the leading dark-matter candidates, and numerous attempts to detect them in laboratories have been performed. Here, we propose to advance these efforts substantially, extending the sensitivity for dark-matter axions in the mass range $(38–54)\mathrm{\mu }\mathrm{eV}$ down to the axion-photon couplings $g_{a\gamma \gamma }\lesssim ({10}^{-14}-{10}^{-15}){\mathrm{GeV}}^{-1}$, motivated by generic models of quantum chromodynamics axion. Single-photon detectors operating at ultralow temperatures are key elements of the experiment. The projected sensitivity will be reached in one year of data taking with magnetic field of (1–10) T, making Cosmological Axion Sarov Haloscope (CASH) the most sensitive haloscope in this mass range.

Simulations of collisions of fundamental particles on a quantum computer are expected to have an exponential advantage over classical methods and promise to enhance searches for new physics. Furthermore, scattering in scalar field theory has been shown to be bounded-error quantum polynomial time (BQP) complete, making it a representative problem for which quantum computation is efficient. As a step toward large-scale quantum simulations of collision processes, scattering of wave packets in one-dimensional scalar field theory is simulated using 120 qubits of IBM’s Heron superconducting quantum computer ibm_fez. Variational circuits compressing vacuum preparation, wave packet initialization, and time evolution are determined using classical resources. By leveraging physical properties of states in the theory, such as symmetries and locality, the variational quantum algorithm constructs scalable circuits that can be used to simulate arbitrarily large system sizes. A new strategy is introduced to mitigate errors in quantum simulations, which enables the extraction of meaningful results from circuits with up to 4924 two-qubit gates and two-qubit gate depths of 103. The effect of interactions is clearly seen, and is found to be in agreement with classical matrix product state simulations. The developments that will be necessary to simulate high-energy inelastic collisions on a quantum computer are discussed.

We present the first lattice quantum chromodynamics (QCD) calculation of the pion valence-quark transverse-momentum-dependent parton distribution function (TMDPDF) within the framework of large-momentum effective theory (LaMET). Using correlators fixed in the Coulomb gauge (CG), we computed the quasi-TMD beam function for a pion with a mass of 300 MeV, a fine lattice spacing of $a=0.06\mathrm{fm}$, and multiple large momenta up to 3 GeV. The intrinsic soft functions in the CG approach are extracted from form factors with large momentum transfer, and as a byproduct, we also obtain the corresponding Collins-Soper (CS) kernel. Our determinations of both the soft function and the CS kernel agree with perturbation theory at small transverse separations ($b_{\perp }$) between the quarks. At larger $b_{\perp }$, the CS kernel remains consistent with recent results obtained using both CG and gauge-invariant TMD correlators in the literature. By combining next-to-leading logarithmic factorization of the quasi-TMD beam function and the soft function, we obtain an $x$-dependent pion valence-quark TMDPDF for transverse separations $b_{\perp }\gtrsim 1\mathrm{fm}$. Interestingly, we find that the $b_{\perp }$ dependence of the phenomenological parametrizations of TMDPDF for moderate values of $x$ are in reasonable agreement with our QCD determinations. In addition, we present results for the transverse-momentum-dependent wave function for a heavier pion with 670 MeV mass.