We discuss the effect of wave function renormalization (WFR) in asymptotically safe gravity. We show that there are two WFR-invariant quantities, and the renormalization (RG) equations may be written entirely in terms of these quantities. The same set of RG equations can be obtained whether we fix the vacuum energy or Newton coupling along the RG trajectory. The flow of the Newton constant and the vacuum energy is also discussed in detail. In particular we discuss how the vacuum energy behaves near the singular barrier in the low energy.

Thus far, the literature regarding holographic complexity almost entirely focuses on the context of ($d+1$)-dimensional anti–de Sitter spacetime rather than the full higher-dimensional gauge/gravity duality in string or M theory. We provide a framework to study holographic complexity in the full duality, explaining the relation of complexity functionals in the higher-dimensional theory to those in anti–de Sitter spacetime and when complexity functionals can apply universally to gauge/gravity dualities rather than a specific dual pair. We also show that gauge invariance constrains boundary terms for complexity functionals, using the 10- and 11-dimensional supergravity actions as key examples. Finally, we propose new universal complexity functionals following these considerations, including a revised gauge-invariant action complexity.

We study thermal states of the strongly coupled Klebanov-Witten $\mathcal{N}=1$ superconformal gauge theory with $R$-symmetry chemical potential. The theory has two distinct dimension $\mathrm{\Delta }=3$ chiral primary operators that develop a condensate at the same critical value of the chemical potential. One instability is associated with the spontaneous fluxification (the appearance of the 3-form flux) of the holographic dual black hole, while the other one is associated with the spontaneous scalarization (the activation of the deformation mode of the conifold). Different phases dominate in grand canonical and microcanonical ensembles.

We propose a scheme for the construction of deformed matrix geometries using Landau models. The Landau models are practically useful tools to extract matrix geometries. The level projection method however cannot be applied straightforwardly to the Landau models on deformed manifolds, as they do not generally exhibit degenerate energy levels. We overcome this problem by exploiting the idea of spectral flow. Taking a symmetric matrix geometry as a reference point of the spectral flow, we evolve the matrix geometry by deforming the Landau model. In this process, unitarity is automatically preserved. The explicit matrix realization of the coordinates is derived mechanically even for a nonperturbative deformation. We clarify basic properties of the deformed matrix geometries through a concrete analysis of the nonrelativistic and relativistic Landau models on expanding two-sphere and elongating ellipsoid. The obtained ellipsoidal matrix geometries show behaviors quantitatively different in each Landau level, but qualitatively similar to their classical counterpart. We also numerically investigate the differences between the ellipsoidal matrix geometry and the fuzzy ellipsoid.

We perform a systematic study of eccentric orbiting nonspinning black hole binaries. We first make a technical study of the optimal full numerical techniques to apply to these studies. We find the grid structure and global resolution that optimize accuracy and speed of current computational resources, while choosing different gauge parameters and Courant factors, $c=dx/dt$, find its optimal value of 0.45. With these choices we perform a study of the merger times $t_m(e)$ as a function of eccentricity, $e$, for configurations with comparable orbital energy content and find that its dependence is well represented by the post-Newtonian factor $F(e)=(1+73e^2/24+37e^4/96)/(1-e^2{)}^{7/2}$, when merger times are normalized to their quasicircular values, i.e., $t_m(e)\approx t_m(0)/F(e)$. We then perform a systematic coverage of five small-medium eccentricities up to $e\sim 0.45$ and six mass ratios up to $8.5:1$ producing a total of 30 simulations covering up to 25 orbits to merger to further model the unequal mass ratio dependence of merger times and as a seed study to a forthcoming new systematic catalog of gravitational waveforms from eccentric binary black holes to allow to perform direct parameter estimations of gravitational waves events.

Virbhadra and Ellis have proposed a very accurate equation (referred to as the VE equation) for the gravitational lens in a static and spherically symmetric spacetime [Phys. Rev. D 62, 084003 (2000)], whereas an improved equation (referred to as the OB equation) has been derived by Bozza [Phys. Rev. D 78, 103005 (2008)] based on a relation found by Ohanian [Am. J. Phys. 55, 428 (1987)]. The OB equation was rediscovered later by Takizawa et al. [Phys. Rev. D 102, 064060 (2020)]. The VE and OB equations seem to be very different from each other. The present paper shows that there exists an unphysical branch in the VE equation. Consequently, the VE equation can be improved by removing the unphysical branch. The improved version of the VE equation is found to be the same as the OB equation when a suitable transformation is made between the deflection angles defined differently in the two formulations. An explicit expression of the transformation is found. We also argue possible numerical differences when the transformation between the deflection angles is ignored.

We implement a simple, main beam correction in the maximum-likelihood, parametric component separation approach, which allows on accounting for different beam widths of input maps at different frequencies without any preprocessing. We validate the approach on full-sky and cut-sky simulations and discuss the importance and impact of the assumptions and simplifications. We find that, in the cases when the underlying sky model is indeed parametric, the method successfully recovers component spectral parameters and component maps at the predefined resolution. The improvement on the precision of the estimated spectral parameters is found to be minor due to the redness of the foreground angular spectra, however the method is potentially more accurate, in particular if the foreground properties display strong, spatial variability, as it does not assume commutation of the beam smoothing and mixing matrix operators. The method permits a reconstruction of the cosmic microwave background map with a resolution significantly superior to that of the lowest resolution map used in the analysis and with the nearly optimal noise level, facilitating exploitation of the cosmological information contained on angular scales, which would be otherwise inaccessible. The method preserves all the advantages of a pixel-domain implementation of the parametric approach, and, as it deals with the beams in the harmonic domain, it can also straightforwardly account for spatially stationary map-domain noise correlations.

We investigate the structural and observable impacts of dark matter (DM) on neutron stars (NSs) using a combined equation of state that integrates the relativistic mean-field (RMF) model for baryonic matter with a variable density profile for DM, incorporating DM-baryon interactions mediated by the Higgs field. Employing three RMF parameter sets (NL3, BigApple, and IOPB-I) for baryonic matter, we analyze mass-radius relations, maximum mass, and tidal deformability, focusing on DM density scaling ($\alpha$) and steepness ($\beta$) parameters. Our findings reveal that increased DM concentration significantly enhances NS compactness, shifting mass-radius profiles and reducing tidal deformability. The DM influence strongly depends on the steepness of the DM density profile, where high $\beta$ values lead to strongly confined DM within the NS core, resulting in more compact and less deformable configurations. Observational constraints from PSR $\mathrm{J}0740+6620$ and GW170817 impose consistent structural limits on DM fractions across different equations of state models, narrowing the allowable parameter space for DM and linking specific combinations of $\alpha M_{\chi }$ ($M_{\chi }$ being the mass of dark matter particle) and $\beta$ values to viable NS structures. This study highlights the interplay among DM concentration, nuclear stiffness, and observational data in shaping NS structure, offering insights into future constraints on DM in high-density astrophysical environments.

The 21-cm signal provides a novel avenue to measure the thermal state of the Universe during cosmic dawn and reionization (redshifts $z\sim 5–30$), and thus to probe energy injection from decaying or annihilating dark matter (DM). These DM processes are inherently inhomogeneous: both decay and annihilation are density-dependent, and furthermore, the fraction of injected energy that is deposited at each point depends on the gas ionization and density, leading to further anisotropies in absorption and propagation. In this work, we develop a new framework for modeling the impact of spatially inhomogeneous energy injection and deposition during cosmic dawn, accounting for ionization and baryon density dependence, as well as the attenuation of propagating photons. We showcase how this first completely inhomogeneous treatment affects the predicted 21-cm power spectrum in the presence of exotic sources of energy injection, and forecast the constraints that upcoming HERA measurements of the 21-cm power spectrum will set on DM decays to photons and to electron/positron pairs. These projected constraints considerably surpass those derived from CMB and Lyman-$\alpha$ measurements, and for decays to electron/positron pairs they exceed all existing constraints in the sub-GeV mass range, reaching lifetimes of $\sim {10}^{28}\mathrm{s}$. Our analysis demonstrates the unprecedented sensitivity of 21-cm cosmology to exotic sources of energy injection during the cosmic dark ages. Our code, dm21cm, includes all these effects and is publicly available in an accompanying release.

The merger of two neutron stars probes dense matter in a hot, neutrino-trapped regime. In this work, we investigate how fully accounting for pions ($\pi$), muons ($\mu$), and muon-type neutrinos (${\nu }_{\mu }$) in the trapped regime may affect the outcome of the merger. By performing fully general-relativistic hydrodynamics simulations of merging neutron stars with equations of state to which we systematically add those different particle species, we aim to provide a detailed assessment of the impact of muons and pions on the merger and postmerger phases. In particular, we investigate the merger thermodynamics, mass ejection, and gravitational wave emission. Our findings are consistent with previous expectations, that the inclusion of such microphysical degrees of freedom and finite temperature corrections leads to frequency shifts on the order of 100–200 Hz in the postmerger gravitational wave signal, relative to a fiducial cold nucleonic equation-of-state model.

Massive black holes (BHs) grow by gas accretion and mergers, observable through electromagnetic and gravitational wave (GW) emission. The James Webb Space Telescope (JWST) has detected faint active galactic nuclei (AGNs) powered by accreting BHs with masses of $M_{•}\sim {10}^{6–8}{M}_{\odot }$, revealing a previously unknown, abundant population of BHs. This mass range overlaps with the detection scopes of space-based GW interferometers and approaches the upper bounds of the predicted mass of seed BHs. We model BH mass assembly in light of the new JWST findings to investigate their formation channels and predict merger events. Two types of seed BHs are considered: heavy seeds ($M_{•}\sim {10}^{2-5}{M}_{\odot }$) formed in rare and overdense cosmic regions, and light seeds ($M_{•}\sim {10}^{1-3}{M}_{\odot }$) formed as stellar remnants in less massive dark-matter halos. The BHs grow through episodic accretion and merger events, which we model by fitting the AGN luminosity function to observational data including JWST-identified AGNs at $z\sim 5$. We find that heavy seeds alone struggle to explain quasars and faint JWST-selected AGNs simultaneously, requiring the more abundant light seeds. The observed merger rate of BHs from heavy seeds alone is limited to $\lesssim {10}^{-1}{\mathrm{yr}}^{-1}$ for major mergers at $z\ge 5$. However, the presence of light seeds increases the major merger rate by several orders of magnitude, which peaks at a total BH mass of $\simeq 2\times {10}^3{M}_{\odot }$ over $5<z<10$ at a rate of $\sim 30{\mathrm{yr}}^{-1}$. These events are detectable by future GW observatories such as the Laser Interferometer Space Antenna (LISA) and the pathfinder to DECi-hertz Interferometer Gravitational-wave Observatory (B-DECIGO). Precise sky localization and distance measurement of those GW events, with solid angle and luminosity distance uncertainties $\mathrm{\Delta }\mathrm{\Omega }\mathrm{\Delta }\log D_L\lesssim {10}^{-4}{\mathrm{deg}}^2$, will enable electromagnetic identification of mergers at $z\ge 5$ and subsequent multimessenger follow-up observations.

Axionlike particles (ALPs) are promising candidates to comprise all the dark matter in the Universe. We investigate the ALP couplings to photons and electrons via astrophysical measurements through the search for very-high-energy gamma rays arising from high-energy cosmic-ray scattering off ALP populating the halo of the Milky Way. We show that gamma-ray signals from ALP couplings to photons and electrons via inverse Primakoff and Compton processes, respectively, can be probed by very-high-energy ($\gtrsim 100\mathrm{GeV}$) gamma-ray ground-based observatories, providing an alternative and complementary avenue to probe ALP couplings in the eV mass range. Sensitivities of current and near-future ground-based gamma-ray observatories improves upon 1 order of magnitude the current constraints from gamma-ray satellite experiments for the ALP-photon couplings in the region of masses below ${10}^{-9}\mathrm{GeV}$. Their sensitivities reached on the ALP-electron couplings allow probing masses below ${10}^{-8}\mathrm{GeV}$, which are lower than the masses probed in gamma-ray satellite experiments.

Tilt-to-length (TTL) coupling is expected to be one of the major noise sources in the interferometric phase readouts in the TianQin mission. Arising from the angular motion of spacecraft (SC) and the onboard movable optical subassemblies (MOSAs), TTL noise needs to be removed in postprocessing after suppressing the laser phase noise with the time-delay interferometry (TDI) technique. In this article, we show that we can estimate the TTL coupling coefficients using the null TDI channel $\zeta$ and remove the TTL noise in the commonly used Michelson variables with the estimated coefficients. We introduce the theoretical model of TTL noise in TDI and consider linear drifts in the linear TTL coefficients for noise estimation and subtraction. The TTL coefficients with drifts are estimated successfully with an accuracy of $10\mathrm{\mu }\mathrm{m}/\mathrm{rad}$ in our numerical simulation. We discuss the impact of point-ahead angle compensation error and wavefront error, and find it necessary to estimate linear drift coefficients and quadratic TTL coefficients to keep TTL noise residuals below the 0.3 pm noise reference curve. However, the estimation accuracy suffers greatly from the correlation between yaw jitter measurements that contain the same SC jitter. Assuming all angular jitters induced by MOSAs are independent, choosing a frequency range with relatively higher MOSA yaw jitter noise levels is beneficial to the TTL coefficient estimation.

We study the Bose-Einstein condensation (BEC) of a free Bose gas under rigid rotation. The aim is to explore the impact of rotation on the thermodynamic quantities associated with BEC, including the Bose-Einstein (BE) transition temperature and condensate fraction. We begin by introducing the rotation in the Lagrangian density of free charged Klein-Gordon fields and determine the corresponding grand canonical partition function at finite temperature, chemical potential, and finite angular velocity. Assuming slow rotation, we derive analytical expressions for the pressure, energy, number, and angular momentum densities of a free Bose gas in nonrelativistic and ultrarelativistic limits in terms of the corresponding fugacities. We then focus on the phenomenon of BEC. We calculate the critical temperature of BEC transition and the condensate fraction in a slowly rotating Bose gas including only particles. Our findings indicate that the critical exponent associated with the BE transition in a rotating gas is lower compared to that in a nonrotating Bose gas. We also determine the fugacity in a rotating Bose gas in the aforementioned limits and examine how rotation affects its temperature dependence, both below and above the critical temperature. By analyzing the behavior of heat capacity at these temperatures, we demonstrate that in a nonrelativistic Bose gas, the rotation transforms the nature of the BE phase transition from a continuous to a discontinuous transition. In general, we find that a nonrelativistic Bose gas under rotation behaves similarly to a nonrotating Bose gas in ultrarelativistic limit.

A nonextensive ($3+1$)-dimensional hydrodynamic model for multiparticle production processes, NEX-CLVisc, is developed in the framework of CLVisc where the viscous corrections are turned off. It assumes that the nonextensive effects consistently exist in the initial conditions set by the optical Glauber model, the equation of state and the hadron kinetic freeze-out procedure. The model is then applied to simulate the pseudorapidity ($\eta$) distribution, the transverse momentum ($p_{\mathrm{T}}$) spectra and the $p_{\mathrm{T}}$-differential elliptic flow ($v_2$) of charged particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ and 5.02 TeV, respectively. It is found that the model can reasonably well reproduce the experimental data of the $\eta$ distribution and the charged-particle spectra in a $p_{\mathrm{T}}$ range up to $6–8\mathrm{GeV}/\mathrm{c}$. When compared with the ideal hydrodynamic model, the $p_{\mathrm{T}}$-differential $v_2$ of charged particles is suppressed in the NEX-CLVisc model, which is similar to that observed in the hydrodynamic model with a shear viscous correction. Moreover, due to the lack of the viscous corrections and the event-by-event fluctuation, the model can only describe the $p_{\mathrm{T}}$-differential $v_2$ up to $3–4\mathrm{GeV}/\mathrm{c}$, which is smaller than its applicable range for the particle $p_{\mathrm{T}}$ spectra.

We study quantum entanglement and test violation of Bell-type inequality at the Circular Electron Positron Collider (CEPC), which is one of the most attractive future collides. It is a promising particle collider designed to search new physics, make Standard Model (SM) precision measurements, and serving as a Higgs factory. Our study is based on a fast simulation of the $Z$ boson pair production from Higgs boson decay at $\sqrt{s}=250\mathrm{GeV}$. The detector effects are also included in the simulation. The spin density matrix of the joint $ZZ$ system is parametrized using irreducible tensor operators and reconstructed from the spherical coordinates of the decay leptons. To test Bell inequalities, we construct observable quantities for the $H\to ZZ*$ process in CEPC by using the Collins-Gisin-Linden-Massar-Popescu (CGLMP) inequality, whose value is determined from the density matrix of the Z boson pairs. The sensitivity of the Bell inequality violation is observed with more than $1\sigma$ and the presence of the quantum entanglement is probed with more than $2\sigma$ confidence level.

Motivated by the null results of current dark matter searches and the small-scale problems, we study a dark sector charged by a spontaneous broken gauge $U(1{)}^{\prime }$. To explore the parameter space of this model, in addition to the consideration of the small-scale data, we also consider the theoretical bounds on the dark Higgs mass, with the upper bound coming from the tree-level perturbative unitarity and the lower bound from the one-loop Linde-Weinberg bound. We deeply examine the dependence of the Linde-Weinberg bound on gauge choice and energy scale, and present a Linde-Weinberg bound that is gauge and scale independent. Combining the theoretical and observational constraints, we obtain the following ranges for the parameter space: the dark matter mass is 10–500 GeV, the mediator (dark photon) mass is 0.5–5 MeV, the dark Higgs mass is 0.05–50 MeV, and the dark fine-structure constant is 0.001–0.4. We conclude that the dark Higgs in this model cannot be ignored in the phenomenological study of the dark sector.