Pairs of misalignment-produced axions with nearby masses can experience a nonlinear resonance that leads to enhanced direct and astrophysical signatures of axion dark matter. In much of the relevant parameter space, self-interactions cause axion fluctuations to become nonperturbative and to collapse in the early Universe. We investigate the observational consequences of such nonperturbative structure in this “friendly axion” scenario with $3+1$ dimensional simulations. Critically, in a substantial fraction of parameter space we find that nonlinear dynamics work to equilibrate the abundance of the two axions, making it easier than previously expected to experimentally confirm the existence of a resonant pair. We also compute the gravitational wave emission from friendly axion dark matter; while the resulting stochastic background is likely undetectable for axion masses above ${10}^{-22}\mathrm{eV}$, the polarization of the cosmic microwave background does constrain possible hyperlight, friendly subcomponents. Finally, we demonstrate that dense, self-interaction–bound oscillons formed during the period of strong nonlinearity are driven by the homogeneous axion background, enhancing their lifetime beyond the in-vacuum expectation.

The low-threshold experiment SENSEI, which uses the ultralow-noise silicon Skipper-CCD to explore light dark matter from the halo, has achieved the most stringent limitations on the light dark matter-electron scattering cross section. In this work, we investigate the inelastic dark matter (IDM)-electron scattering process via the SENSEI data and derive the constraints on the inelastic dark matter model with a $U(1)$ gauge boson as the mediator. Comparing with the elastic scattering process, we find that the down-scattering process with the mass splitting $\delta \equiv m_{{\chi }_2}-m_{{\chi }_1}<0$ is more strongly constrained while the up-scattering process $\delta >0$ gets the weaker limits. For the down-scattering process with mass splitting $\delta \sim -5\mathrm{eV}$, the DM mass $m_{\chi }$ can be excluded down to as low as 0.1 MeV.

We study the properties of the Lindbladian quantum mechanical evolution of quarkonia with non-Abelian charges (color-singlet and octet) in the quark-gluon plasma. We confirm that heavy quark recoils in the Lindblad equation correctly thermalize quarkonium colorful states within statistical errors from the simulation method. We also demonstrate that the Lindblad equation in the dipole limit can provide an efficient alternative method, which is applicable to a finite time evolution before thermalization and dramatically reduces the numerical cost. Our findings will serve as a foundation for large-scale simulation of quarkonium dynamics in the relativistic heavy-ion collisions.

In a recent paper [Artymowski et al., Phys. Rev. D 103, L121303 (2021)] we suggested the possibility that the present acceleration of the Universe is due to thermodynamical behavior of unparticles. The model is free of scalar fields, modified gravity, a cosmological constant, the coincidence problem, initial conditions problem and possesses interesting distinct predictions regarding the equation of state of dark energy, the growth rate and the number of relativistic degrees of freedom at big bang nucleosynthesis and cosmic microwave background decoupling. In this work we relate to a recent paper [Abchouyeh and van Putten, Phys. Rev. D 104, 083511 (2021)], which discusses a similar setup of unparticles with and without a cosmological constant as an external source of late-time acceleration. The authors have shown how such a model is inconsistent with the data. We show that these claims are viable only in a particular part of the parameter space and that the model of Artymowski, Ben-Dayan, and Kumar stands tall. We further suggest a consistency condition in terms of observables. We then fit publicly available supernovae data to derive the expected Hubble parameter and constrain the parameters of the model.

We discuss a $\sim 3\sigma$ signal (local) in the light Higgs-boson search in the diphoton decay mode at $\sim 96\mathrm{GeV}$ as reported by CMS, together with a $\sim 2\sigma$ excess (local) in the $b\overline{b}$ final state at the Large Electron Positron Collider (LEP) in the same mass range. We interpret this possible signal as a Higgs boson in the 2 Higgs doublet model type II with an additional Higgs singlet, which can be either complex (2HDMS) or real (N2HDM), where the 2HDMS so far has never been analyzed as an explanation of these excesses. An emphasis of our work is the differences between and the possible distinction of the two models in this context. We find that the lightest $\mathcal{C}\mathcal{P}$-even Higgs boson of the two models can equally yield a perfect fit to both excesses simultaneously, while the second lightest state is in full agreement with the Higgs-boson measurements at 125 GeV, and the full Higgs-boson sector is in agreement with all Higgs exclusion bounds from LEP, the Tevatron and the LHC as well as other theoretical and experimental constraints. We derive bounds on the 2HDMS and N2HDM Higgs sectors from a fit to both excesses and describe how this signal can be further analyzed at future $e^{+}{e}^{-}$ colliders, such as the International Linear Collider (ILC). We analyze in detail the anticipated precision of the coupling measurements of the 96 GeV Higgs boson at the ILC. We find that these Higgs-boson measurements at the LHC and the ILC cannot distinguish between the two Higgs-sector realizations.

Very recently, it was suggested that combining the swampland program with the smallness of the dark energy and confronting these ideas to experiment lead to the prediction of the existence of a single extra dimension (dubbed the dark dimension) with characteristic length scale in the micron range. We show that the rate of Hawking radiation slows down for black holes perceiving the dark dimension and discuss the impact of our findings in assessing the dark matter fraction that could be composed of primordial black holes. We demonstrate that for a species scale of $\mathcal{O}({10}^{10}\mathrm{GeV})$, an all-dark-matter interpretation in terms of primordial black holes should be feasible for masses in the range ${10}^{14}\lesssim M_{\mathrm{BH}}/\mathrm{g}\lesssim {10}^{21}$. This range is extended compared to that in the 4D theory by 3 orders of magnitude in the low mass region. We also show that primordial black holes with $M_{\mathrm{BH}}\sim {10}^{12}\mathrm{g}$ could potentially explain the well-known Galactic 511 keV gamma-ray line if they make up a tiny fraction of the total dark matter density.

We consider a pseudoscalar axionlike field coupled to a Chern-Simons gravitational anomaly term. The axion field backreacts on a rotating Kerr black hole background, resulting in modifications in the spacetime. In an attempt to determine potentially observable signatures, we study the angular momentum of the system of the modified Kerr-like black hole and the axionic matter outside the horizon of the black hole. As the strength of the coupling of the axion field to the Chern-Simons term is increasing, the requirement that the total angular momentum of the system remains constant forces the black hole angular momentum to decrease. There exists a critical value of this coupling beyond which the black hole starts to rotate in the opposite direction, with an increasing magnitude of its angular momentum. We interpret this effect as a consequence of the exchange of energy between the axionic matter and the gravitational anomaly, which is sourced by the rotating black hole.

Loosely inspired by the somewhat fanciful notion of detecting an arbitrarily advanced alien civilization, we consider a general-relativistic thin-shell Dyson megasphere completely enclosing a central starlike object, and perform a full general-relativistic analysis using the Israel-Lanczos-Sen junction conditions. We focus attention on the surface mass density, the surface stress, the classical energy conditions, and the quasilocal forces between hemispheres. We find that in the physically acceptable region the null, weak, and strong energy conditions (NEC, WEC, and SEC) are always satisfied, while the dominant energy condition (DEC) can be violated if the Dyson megasphere is sufficiently close to forming a black hole. We also demonstrate that the original quasilocal version of the maximum force conjecture, $F\le \frac{1}{4}{F}_{\mathrm{Stoney}}=\frac{1}{4}{F}_{\text{Planck}}$, can easily be violated if the Dyson megasphere is sufficiently compact, that is, sufficiently close to forming a black hole. Interestingly there is a finite region of parameter space where one can violate the original quasilocal version of the maximum force conjecture without violating the DEC. Finally, we very briefly discuss the possibility of nested thin-shell megaspheres (Matrioshka configurations) and thick-shell Dyson megaspheres.

The polarized Sunyaev-Zel’dovich (pSZ) effect is sourced by the Thomson scattering of cosmic microwave background (CMB) photons from distant free electrons and yields a novel view of the CMB quadrupole throughout the observable Universe. Galaxy shear measures the shape distortions of galaxies, probing both their local environment and the intervening matter distribution. Both observables have been shown to give interesting constraints on the cosmological model; in this work we ask: what can be learnt from their combination? The pSZ-shear cross-spectrum measures the shear-galaxy-polarization bispectrum [i.e., $⟨\gamma {\delta }_g(Q\pm iU)⟩$] and contains contributions from three main phenomena: (1) the Sachs-Wolfe (SW) effect, (2) the integrated Sachs-Wolfe (ISW) effect, and (3) inflationary gravitational waves. Since the modes contributing to the pSZ signal are not restricted to the Earth’s past light cone, the low-redshift cross-spectra could provide a novel constraint on dark energy properties via the ISW effect, whilst the SW signal is sourced by a coupling of scalar modes at very different times (recombination and the lensing redshift), but at similar positions; this provides a unique probe of the Universe’s homogeneous time evolution. We give expressions for all major contributions to the galaxy shear, galaxy density, and pSZ auto- and cross-spectra, and evaluate their detectability via Fisher forecasts. Despite significant theoretical utility, the shear cross-spectra will be challenging to detect: combining CMB-S4 with the Rubin observatory yields a $1.6\sigma$ detection of the ISW contribution, though this increases to $5.2\sigma$ for a futuristic experiment involving CMB-HD and a higher galaxy sample density. For parity-even (parity-odd) tensors, we predict a $1\sigma$ limit of $\sigma (r)=0.9$ (0.2) for CMB-S4 and Rubin, or 0.3 (0.06) for the more futuristic setup. Whilst this is significantly better than the constraints from galaxy shear alone (and contains fewer systematics than most auto-spectra), it is unlikely to be competitive, but may serve as a useful cross-check.

We simulate the first minutes of the evolution of a binary-driven hypernova event, with a special focus on the associated accretion processes of supernova ejecta onto the newborn neutron star ($\nu \mathrm{NS}$) and the NS companion. We calculate the rotational evolution of the $\nu \mathrm{NS}$ and the NS under the torques exerted by the accreted matter and the magnetic field. We take into account general relativistic effects through effective models for the NSs binding energy and the specific angular momentum transferred by the accreted matter. We use realistic hypercritical accretion rates obtained from three-dimensional smoothed-particle-hydrodynamics numerical simulations of the binary-driven hypernova event for a variety of orbital periods. We show that the rotation power of the $\nu \mathrm{NS}$ has a unique double-peak structure while that of the NS has a single peak. These peaks are of comparable intensity and can occur very close in time or even simultaneously depending on the orbital period and the initial angular momentum of the stars. We outline the consequences of the above features in the early emission and their consequent observation in long gamma-ray bursts.

We compute the internal modes of a nonspinning neutron star and its tidal metric perturbation in general relativity, and determine the effect of relativistic corrections to the modes on mode coupling. Claims have been made that a new hydrodynamic instability can occur in a neutron star in a binary neutron star system triggered by the nonlinear coupling of the companion’s tidal field to pairs of p-modes and g-modes in it as the binary inspirals toward merger. This “PG” instability may be significant since it can influence the binary’s inspiral phase by extracting orbital energy, thereby potentially causing large deviations in their gravitational waveforms from those predicted by theoretical models that do not account for it. This can result in incorrect parameter estimation, at best, or mergers going undetected, at worst, owing to the use of deficient waveform models. On the other hand, better modeling of this instability and its effect on binary orbits can unravel a new phenomenon and shed light on stellar instabilities, via gravitational wave observations. So far, all mode-tide coupling instability studies have been formulated in Newtonian perturbation theory. Neutron stars are compact objects, so relativistic corrections might be important. We present and test a new code to calculate the relativistic eigenmodes of nonrotating relativistic stars. We use these relativistic tide and neutron star eigenmodes to compute the mode-tide coupling strength (MTCS) for a few selected equations of state. The MTCS thus calculated can be at most tens of percent different from its purely Newtonian value, but we confirm the dependencies on orbital separation and equation of state found by Newtonian calculations. For some equations of state, the MTCS is very sensitive to the neutron star crust region, demonstrating the importance of treating this region accurately.

In a previous article [1], we have reported on the first subpicometer interferometer flown in space as part of ESA’s LISA Pathfinder mission, and have shown the residual sensor noise to be on the level of ${32.0}_{-1.7}^{+2.4}\mathrm{fm}/\sqrt{\mathrm{Hz}}$. This review provides a deeper and more complete overview of the full system and its interferometric mission performance under varying operational conditions, allowing a much more detailed view on the noise model. We also include the optical measurements of rotations through differential wave front sensing (DWS), which reached a sensitivity of as good as $100\mathrm{prad}/\sqrt{\mathrm{Hz}}$. We present more evidence for the long-term stability of the interferometric performance and components. This proves a solid foundation for future interferometry in space such as the LISA mission.

In this work we study the interactions of the multiquark state $Z_{cs}^{-}(3985)$ with light mesons in a hot hadron gas. Using an effective Lagrangian framework, we estimate the vacuum cross sections as well as the thermal cross sections of the production processes ${\overline{D}}_s^{(*)}{D}_s^{(*)}\to Z_{cs}^{-}X(X=\pi ,K,\eta )$ and the corresponding inverse reactions. The results indicate that the considered processes have sizeable cross sections. Most importantly, the thermal cross sections for $Z_{cs}$ annihilation are much larger than those for production. This feature might produce relevant effects on some observables, such as the final $Z_{cs}$ multiplicity measured in heavy ion collisions.

In spite of the success of the Standard Model of particle physics, there are some theoretical predictions which are not yet fully established experimentally, as well as some experimental observations which cannot be fitted within its theoretical framework, thus requiring physics beyond the Standard Model. One of these is a hypothetical nonluminous form of matter–dark matter. Models with an extended scalar electroweak sector yield plausible dark matter candidates. In this paper we study a specific model, C-III-a, from a family of $S_3$-symmetric three-Higgs-doublet models. The model consists of two active SU(2) doublets and an inert one. The latter is inert due to a ${\mathbb{Z}}_2$ symmetry that survives the breaking of $S_3$, and would accommodate a dark matter particle. We explore the model numerically, based on theoretical and experimental constraints. After applying a number of successive checks over the parameter space we found a viable dark matter mass region in the range $[6.5;44.5]\mathrm{GeV}$. This region is drastically different from the Higgs-like dark matter states that have been proposed: the well-known inert doublet model and models with three scalar doublets, with one or two inert doublets. Furthermore, the C-III-a model allows for spontaneous $CP$ violation. This means that the scalar potential explicitly conserves $CP$. However, in order to generate a realistic Cabibbo-Kobayashi-Maskawa matrix we need to introduce complex Yukawa couplings.

We point out the necessity to consider $\beta$-decay observables in resolutions of the $W$-boson anomaly in the Standard Model Effective Field Theory that go beyond pure oblique corrections. We demonstrate that present global analyses that explain the $W$-boson mass anomaly predict a large, percent-level, violation of first-row Cabibbo Kobayashi Maskawa unitarity. We investigate what solutions to the $W$-boson mass anomaly survive after including $\beta$-decay constraints.

We propose the boost asymmetry of the diboson productions $q_i{\overline{q}}_j\to V{V}^{\prime }$ in $pp$ collisions ($V{V}^{\prime }=W\gamma$, $W^{+}{W}^{-}$, and $WZ$) as a new experimental observable, which can provide unique information on the proton structure. The boost asymmetry rises as the difference in the kinematics of the two bosons, that are coupled to the two different quark and antiquark initial states, respectively, and thus reflects different features of the $q_i$ and ${\overline{q}}_j$ parton densities. By comparing the kinematics of the two bosons, such as the boson energy or rapidity, the diboson events with ${\overline{q}}_j$ having higher energy than $q_i$ can be distinguished from those with $q_i$ having higher energy than ${\overline{q}}_j$. This would provide unique information in some special parton momentum fraction regions, which cannot be directly proved by current $W$ and $Z$ measurements at the Large Hadron Collider or other deep inelastic scattering experiments.

The entanglement between momentum modes of a quantum field theory at different scales is not as well studied as its counterpart in real space, despite the natural connection with the Wilsonian idea of integrating out the high-momentum degrees of freedom. Here, we push such a connection further by developing a novel method to calculate the Rényi and entanglement entropies between slow and fast modes, which is based on the Wilsonian effective action at a given scale. This procedure is applied to the perturbative regime of some scalar theories, comparing the lowest-order results with those from the literature and interpreting them in terms of Feynman diagrams. This method is easily generalized to higher-order or nonperturbative calculations. It has the advantage of avoiding matrix diagonalizations of other techniques.

In this paper, we describe an extremely efficient method for computing the renormalized stress-energy tensor of a quantum scalar field in spherically symmetric black hole spacetimes. The method applies to a scalar field with arbitrary field parameters. We demonstrate the utility of the method by computing the renormalized stress-energy tensor for a scalar field in the Schwarzschild black hole spacetime, applying our results to discuss the null energy condition and the semiclassical backreaction.

A deformation of the Abelian Higgs Kibble model induced by a dimension-six derivative operator is studied. A novel differential equation is established fixing the dependence of the vertex functional on the coupling $z$ of the dimension-six operator in terms of amplitudes at $z=0$ (those of the power-counting renormalizable Higgs-Kibble model). The latter equation holds in a formalism where the physical mode is described by a gauge-invariant field. The functional identities of the theory in this formalism are studied. In particular, we show that the Slavnov-Taylor identities separately hold true at each order in the number of internal propagators of the gauge-invariant scalar. Despite being nonpower-counting renormalizable, the model at $z\ne 0$ depends on a finite number of physical parameters.

One of the major obstacles to testing alternative theories of gravity with gravitational-wave data from merging binaries of compact objects is the formulation of their field equations, which is often mathematically ill-suited for time evolutions. A possible way to address these delicate shortcomings is the fixing-the-equations approach, which was developed to control the behavior of the high-frequency modes of the solutions and the potentially significant flow toward ultraviolet modes. This is particularly worrisome in gravitational collapse, where even black hole formation might be insufficient to shield regions of the spacetime where these pathologies might arise. Here, we focus (as a representative example) on scalar-Gauss-Bonnet gravity, a theory that can lead to ill-posed dynamical evolutions, but with intriguing stationary black hole physics. We study the spherical collapse of a scalar pulse to a black hole in the fixing-the-equations approach, comparing the early stages of the evolution with the unfixed theory and the later stages with its stationary limit. With this approach, we are able to evolve past problematic regions in the original theory, resolve black hole collapse, and connect with the static black hole solutions. Our method can thus be regarded as providing a weak completion of the original theory, and the observed behavior lends support for considering previously found black hole solutions as a natural outcome of collapse scenarios.