“Mountains” or nonaxisymmetric deformations of rotating neutron stars (NS) efficiently radiate gravitational waves (GW). We consider analogies between NS mountains and surface features of solar system bodies. Both NS and moons such as Europa or Enceladus have thin crusts over deep oceans while Mercury has a thin crust over a large metallic core. Thin sheets may wrinkle in universal ways. Europa has linear features, Enceladus has “tiger” stripes, and Mercury has lobate scarps. NS may have analogous features. The innermost inner core of the Earth is anisotropic with a shear modulus that depends on direction. If NS crust material is also anisotropic this will produce an ellipticity, when the crust is stressed, that grows with spin frequency. This yields a braking index (log derivative of spin down rate assuming only GW spin down) very different from $n=5$ and could explain the maximum spin observed for neutron stars and a possible minimum ellipticity of millisecond pulsars.

Scalarized black holes (BH) have been shown to form dynamically in extended-scalar-tensor theories, either through spontaneous scalarization—when the BH is unstable against linear perturbations—or through a nonlinear scalarization. In the latter, linearly stable BHs can ignite scalarization when sufficiently perturbed. These phenomena are, however, not incompatible and mixed scalarization is also possible. We explore two aspects of the Einstein-Maxwell-scalar model: solutions containing, simultaneously, linear (also known as standard) and nonlinear scalarization; and the effects of having one of the coupling constants with an “opposite sign” to the one leading to scalarization. Both points are addressed by constructing and examining the mixed scalarization’s domain of existence. An overall dominance of the spontaneous scalarization over the nonlinear scalarization is observed. Thermodynamically, an entropical preference for mixed over the standard scalarization (spontaneous or nonlinear) exists. In the presence of counter scalarization, a quench of the scalarization occurs, mimicking the effect of a scalar particle’s mass/positive self-interaction term.

Detecting binary black hole (BBH) mergers with quantifiable orbital eccentricity would confirm the existence of a dynamical formation channel for these binaries. The current state-of-the-art gravitational wave searches of LIGO-Virgo-KAGRA strain data focus more on quasicircular mergers due to increased dimensionality and lack of efficient eccentric waveform models. In this work, we compare the sensitivities of two search pipelines, the matched filter-based PyCBC and the unmodeled coherent wave burst (cWB) algorithms toward the spinning eccentric BBH mergers, using a multipolar nonprecessing-spin eccentric signal model, SEOBNRv4EHM. Our findings show that neglecting eccentricity leads to missed opportunities for detecting eccentric BBH mergers, with PyCBC exhibiting a 10%–20% sensitivity loss for eccentricities exceeding 0.2 defined at 10 Hz. In contrast, cWB is resilient, with a 10% sensitivity increase for heavier ($\mathcal{M}\ge 30M_{\odot }$) eccentric BBH mergers, but is significantly less sensitive than PyCBC for lighter BBH mergers. Our fitting factor study confirmed that neglecting eccentricity biases the estimation of chirp mass, mass ratio, and effective spin parameter, skewing our understanding of astrophysical BBH populations, fundamental physics, and precision cosmology. Our results demonstrate that the current search pipelines are not sufficiently sensitive to eccentric BBH mergers, necessitating the development of a dedicated matched-filter search for these binaries. Whereas, burst searches should be optimized to detect lower chirp mass BBH mergers, as eccentricity does not affect their search sensitivity significantly.

The thermodynamic interpretation of the Stephani Universes is studied in detail. The general expression of the speed of sound and of the thermodynamic schemes associated with a thermodynamic solution is obtained. The constraints imposed on the solutions by considering some significant physical properties are analyzed. We focus on the models where the cosmological observer measures isotropic radiation. We consider some examples, and a solution that models an ultrarelativistic gas is analyzed in detail.

We investigate scalarized black holes in the Einstein minimally coupled scalar theory with a negative potential $V(\varphi )=-{\alpha }^2{\varphi }^6$. The tachyonic instability is absent from analyzing the linearized scalar equation, which could not allow for spontaneous scalarization. However, we obtain the black hole solutions with scalar hair by solving three full equations because this scalar potential violates the weak energy condition. This shows clearly that a single branch of scalarized black holes can be obtained without introducing a nonminimal scalar coupling term. We perform the stability analysis for scalarized black holes by adopting radial perturbations, implying that all scalarized black holes belonging to a single branch are unstable.

We perform in this work an analysis of the background dynamics for $\alpha$-attractor models in the context of loop quantum cosmology. Particular attention is given to the determination of the duration of the inflationary phase that is preceded by the quantum bounce in these models. From an analysis of the general predictions for these models, it is shown that we can be able to put constraints in the parameter $\alpha$ of the potentials and also on the quantum model itself, especially the Barbero-Immirzi parameter. In particular, the constraints on the tensor-to-scalar ratio and spectral tilt of the cosmological perturbations limit the $\alpha$ parameter of the potentials to values such that ${\alpha }_{n=0}\lesssim 10$, ${\alpha }_{n=1}\lesssim 17$ and ${\alpha }_{n=2}\lesssim 67$, for the $\alpha$ attractors T, E, and $n=2$ models, respectively. Using the constraints on the minimal amount of $e$-folds of expansion from the quantum bounce up to the end of inflation leads to the upper bounds for the Barbero-Immirzi parameter for the $\alpha$-attractor models studied in this work: ${\gamma }_{n=0}\lesssim 51.2$, ${\gamma }_{n=1}\lesssim 63.4$ and ${\gamma }_{n=2}\lesssim 64.2$, which are obtained when fixing the parameter $\alpha$ in the potential at the values saturating the upper bounds given above for each model.

In this work we analyze the evolution of the quantum mixmaster cosmological model within an effective approach. In particular, we study the behavior of the scale factor and anisotropies of the theory, and determine how it deviates from its classical counterpart due to quantum backreaction. Remarkably, we determine that the effective evolution avoids the initial singularity. The semiclassical dynamic of the system is obtained from a Hamiltonian in an extended phase space, whose classical position and momentum variables are the expectation values of the corresponding quantum operators, as well as of quantum dispersions and correlations of the system, and it is in this framework that we obtain semiclassical one-particle trajectories.

We perform a detailed dynamical system analysis for the behavior of a Dirac-Born-Infeld (DBI) field in a spatially closed Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology. The DBI field is characterized by a potential and brane tension. We study power-law or exponential functions for the potential and tension. We find that in a spatially closed FLRW cosmology, a DBI field in the ultrarelativistic limit allows for a broader range of initial conditions resulting in a bouncing universe than in the nonrelativistic limit. We further note that the range of initial conditions allowing for a bounce is larger if we consider power-law functions for the potential and tension, compared to the exponential case. Our dynamical analysis shows that a DBI field does not exhibit stable cyclical behavior, including the case in which a negative cosmological constant is present.

Recently, it was found that a $Q$-ball can amplify waves incident upon it, due to rotation in the internal space and the interaction of the two modes in the complex scalar field. While the spherically symmetric 3D case has been investigated previously, here we explore the 3D axisymmetric case, which is numerically much more challenging. The difficulty comes because a partial wave expansion is needed, and the different partial waves can not be separated, for either the background spinning $Q$-ball solution or the perturbative scattering on top of it. A relaxation method and a high dimensional shooting method are applied to compute the $Q$-ball solutions and the amplification factors respectively. We also classify the behavior of the amplification factors and we discuss their bounds and the superradiance criteria.

We propose a novel means of directly measuring cosmological distances using scintillated microlensing of fast radio bursts (FRBs). In standard strong lensing measurements of cosmic expansion, the main source of systematic uncertainty lies in modeling the mass profile of galactic halos. Using extra-galactic stellar microlensing to measure the Hubble constant avoids this systematic uncertainty as the lens potential of microlenses depends only on a single parameter: the mass of the lens. FRBs, which may achieve nanosecond precision on lensing time delays, are well suited to precision measurements of stellar microlensing, for which the time delays are on the order of milliseconds. However, typical angular separations between the microlensed images on the order of microarcseconds make the individual images impossible to spatially resolve with ground-based telescopes. We propose leveraging scintillation in the interstellar medium (ISM) to resolve the microlensed images, effectively turning the ISM into an astrophysical-scale interferometer. Using this technique, we estimate a 6% uncertainty on $H_0$ from a single observed scintillated microlensing event, with a subpercent uncertainty on $H_0$ achievable with only 30 such events. With an optical depth for stellar microlensing of ${10}^{-3}$, this may be achievable in the near future with upcoming FRB telescopes.

We study penetration of interstellar cosmic rays (CRs) into molecular clouds surrounded by nonuniform diffuse envelopes. The present work generalizes our earlier model of CR self-modulation [Ivlev et al. Astrophys. J. 855, 23 (2018); Dogiel et al. Astrophys. J. 868, 114 (2018)], in which the value for the envelope’s gas density where CRs excite MHD waves was treated as a free parameter. Now, we investigate the case where the density monotonically increases toward the center. Assuming that CRs are relativistic, we obtain a universal analytical solution which does not depend on the particular shape of gas distribution in the envelope, and self-consistently derive boundaries of the diffusion zone formed within the envelope, where CRs are scattered at the self-excited waves. The values of the gas density at the boundaries are found to be substantially smaller than those assumed in the earlier model, which leads to a significantly stronger modulation of penetrating CRs. We compute the impact of CR self-modulation on the gamma-ray emission and show that the results of our theoretical model are in excellent agreement with recent observations of nearby giant molecular clouds by Yang et al. [Nat. Astron. 7, 351 (2023)].

Understanding the physics of the deep solar interior, and the more exotic environs of core-collapse supernovae (CCSN) and binary neutron-star (NS) mergers, is of keen interest in many avenues of research. To date, this physics is based largely on simulations via forward integration. While these simulations provide valuable constraints, it could be insightful to adopt the “inverse approach” as a point of comparison. Within this paradigm, parameters of the solar interior are not output based on an assumed model, but rather are inferred based on real data. We take the specific case of solar electron number density, which historically is taken as output from the standard solar model. We show how one may arrive at an independent constraint on that density profile based on available neutrino flavor data from the Earth-based Borexino experiment. The inference technique’s ability to offer a unique lens on physics can be extended to other datasets, and to analogous questions for CCSN and NS mergers, albeit with simulated data.

Sodium iodide (NaI)-based cryogenic scintillating calorimeters using quantum sensors for signal readout have shown promising first results toward a model-independent test of the annually modulating signal detected by the DAMA/LIBRA dark matter experiment. The COSINUS Collaboration has previously reported on the first above-ground measurements using a dual-channel readout of phonons and light based on transition edge sensors (TESs) that allows for particle discrimination on an event-by-event basis. In this article, we outline the first underground measurement of a NaI cryogenic calorimeter readout via the novel remoTES scheme. A 3.67 g NaI absorber with an improved silicon light detector design was operated at the Laboratori Nazionali del Gran Sasso, Italy. A significant improvement in the discrimination power of $e^{-}/\gamma$ events to nuclear recoils was observed with a fivefold improvement in the nuclear recoil baseline resolution, achieving $\sigma =441\mathrm{eV}$. Furthermore, we present a limit on the spin-independent dark matter nucleon elastic scattering cross section, achieving a sensitivity of $\mathcal{O}(\mathrm{pb})$ with an exposure of only 11.6 g d.

Motivated by the old idea of using the Moon as a resonant gravitational wave (GW) detector, as well as the recent updates in modeling the lunar response to GWs, we reevaluate the feasibility of using a network of lunar seismometers to constrain the stochastic GW background (SGWB). In particular, using the updated model of the lunar response, we derive the pattern functions for the two polarizations of GW. With these pattern functions, we further calculate the overlap reduction functions for a network of lunar seismometers, where we have relaxed the conventional assumption that lunar seismometers are perfectly leveled to measure only the vertical acceleration. We apply our calculation to two future lunar projects, namely, Chang’e and the Lunar Gravitational Wave Antenna (LGWA). We find that the two projects could constrain the SGWB to a level of ${\mathrm{\Omega }}_{\mathrm{GW}}^{\text{Chang}’\mathrm{e}}<2.4\times {10}^2$ and ${\mathrm{\Omega }}_{\mathrm{GW}}^{\mathrm{LGWA}}<2.0\times {10}^{-10}$, respectively, which corresponds to a signal-to-noise ratio of $\mathrm{SNR}=3$. These results are better than the constraints placed previously on the SGWB in the mid-frequency band (around ${10}^{-3}–10\mathrm{Hz}$) by various types of experiments.

We present a theoretical investigation of the expected experimental signals produced by freely falling atoms with time oscillating mass and transition frequency. These oscillations could be produced in a variety of models, in particular, models of scalar dark matter nonuniversally coupled to the standard matter such as axionlike particles and dilatons. Performing complete and rigorous calculations, we show that, on one hand, two different atomic species would accelerate at a different rate, and, on the other hand, they would produce a nonzero differential phase shift in atom interferometers (AI). The former would produce observable signals in equivalence principle tests like the recent MICROSCOPE mission, and we provide a corresponding sensitivity estimate, showing that MICROSCOPE can reach beyond the best existing searches in the axionlike particle case. We also compare the expected sensitivity of two future AI experiments, namely the AION-10 gradiometer and an isotope differential AI considered for MAGIS-100, that we will refer to as SPID. We show that the SPID setup would be more sensitive to these dark matter fields compared to the gradiometer one, assuming equivalent experimental parameters.

We argue that the higher weak isospin $SU(3{)}_L$ manifestly unifies dark matter and normal matter in its isomultiplets for which dark matter carries a conserved dark charge while normal matter does not. The resultant gauge symmetry is given by $SU(3{)}_C\otimes SU(3{)}_L\otimes U(1{)}_X\otimes U(1{)}_G$, where the first factor is the color group, while the rest defines a scotoelectroweak theory in which $X$ and $G$ determine electric charge $Q=T_3-1/\sqrt{3}{T}_8+X$ and dark charge $D=-2/\sqrt{3}{T}_8+G$. This setup provides both appropriate scotogenic neutrino masses and dark matter stability as preserved by a residual dark parity $P_D=(-1{)}^D$. Interpretation of the dark charge is further discussed, given that $SU(3{)}_L$ is broken at very high energy scale.

A novel collider, called $\mu \mathrm{TRISTAN}$, was recently proposed, offering the capability to achieve high-energy collisions of antimuons. This high-energy collider presents an exceptional opportunity for the discovery of electroweak-interacting massive particles (EWIMPs), which are predicted by various new physics models. In a lepton collider like $\mu \mathrm{TRISTAN}$, the potential for discovering EWIMPs extends beyond their direct production. Quantum corrections arising from EWIMP loops can significantly enhance our prospects for discovery by precise measurement of Standard Model processes. This study focuses on the indirect detection method within the $\mu \mathrm{TRISTAN}$ experiment, with a specific emphasis on TeV-scale EWIMP dark matter scenarios that yield the correct thermal relic density. At collision energies for $\sqrt{s}=O(1–10)\mathrm{TeV}$, these EWIMPs introduce noticeable effects, typically in the range of $O(0.1–1)\%$. Our findings indicate that at $\sqrt{s}=2(10)\mathrm{TeV}$, with an integrated luminosity of $10{\mathrm{ab}}^{-1}$, $\mu \mathrm{TRISTAN}$ can detect Higgsinos at a mass of 1.3 (3.0) TeV and winos at a mass of 1.9 (4.4) TeV, assuming an optimistic level of systematic uncertainty in the observation of the Standard Model processes.

We work the lattice fermions and non-Hermitian formulation in the 2D Gross-Neveu-Yukawa (GNY) model and demonstrate the numerical implementation for two flavors by the hybrid Monte Carlo. Our approach has a notable advantage in dealing with chiral symmetry on a lattice by avoiding the Nielsen-Ninomiya theorem, due to the nonsymmetrized finite-difference operator. We restore the hypercubic symmetry by averaging over all possible orientations with the proper continuum limit. Our study is the first simulation for the interacting fermion formulated in a non-Hermitian way. We compare the numerical solution with the one-loop resummation. The resummation results matches with the numerical solution in $⟨\varphi ⟩$, $⟨{\varphi }^2⟩$, $⟨\mathrm{Tr}({\overline{\psi }}_1{\psi }_1+{\overline{\psi }}_2{\psi }_2)/2⟩$, and $⟨\mathrm{Tr}({\overline{\psi }}_1{\psi }_1+{\overline{\psi }}_2{\psi }_2)\varphi /2⟩$. We also used the one-loop resummation to provide the renormalization group flow and asymptotic safety in the 2D GNY model.

We investigate the multiplicity dependence of the transverse momentum $p_T$ spectra of hadrons produced in high-energy collisions. We propose that the partonic distribution be parametrized by its nonextensive entropy and the parton saturation scale $Q_s(x)$. These two variables can be identified from the produced charged hadron distributions and provide important information on the gluon dynamics at the moment of interaction. From this perspective, we interpret data from different ALICE multiplicity classes at $\sqrt{s}=13\mathrm{TeV}$ and $\sqrt{s}=5.02\mathrm{TeV}$. A multiplicity-dependent scaling function is presented and the dependence of the interaction area on multiplicity is also investigated.

Previously, it was found that pion superfluidity could be realized in the quantum chromodynamics (QCD) epoch of the early Universe, when lepton flavor asymmetry $|l_{\mathrm{e}}+l_{\mu }|$ is large enough to generate a charge chemical potential $|{\mu }_{\mathrm{Q}}|$ larger than vacuum pion mass. By following the same logic, kaon superfluidity might also be possible when $|l_{\mathrm{e}}+l_{\mu }|$ is so large that $|{\mu }_{\mathrm{Q}}|$ becomes larger than vacuum kaon mass. Such a possibility is checked by adopting Ginzburg-Landau approximation within the three-flavor Polyakov–Nambu–Jona-Lasinio model. Consider the case with full chemical balance, though kaon superfluidity could be stable compared to the chiral phases with only $\sigma$ condensations, it would get killed by the more favored homogeneous pion superfluidity. If we introduce mismatch between $s$ and $d$ quarks, kaon superfluidity would require so large $s$ quark density that such a state is impossible in the early Universe.