The role of Lorentz symmetry in ghost-free massive gravity is studied, emphasizing features emerging in approximately Minkowski spacetime. The static extrema and saddle points of the potential are determined and their Lorentz properties identified. Solutions preserving Lorentz invariance and ones breaking four of the six Lorentz generators are constructed. Locally, globally, and absolutely stable Lorentz-invariant extrema are found to exist for certain parameter ranges of the potential. Gravitational waves in the linearized theory are investigated. Deviations of the fiducial metric from the Minkowski metric are shown to lead to pentarefringence of the five wave polarizations, which can include superluminal modes and subluminal modes with negative energies in certain observer frames. The Newton limit of ghost-free massive gravity is explored. The propagator is constructed and used to obtain the gravitational potential energy between two point masses. The result extends the Fierz-Pauli limit to include corrections generically breaking both rotation and boost invariance.

The use of effective-one-body (EOB) waveforms for black hole binaries analysis in gravitational-wave astronomy requires faithful models and fast generation times. A key aspect to achieve faithfulness is the inclusion of numerical-relativity (NR) informed next-to-quasicircular corrections (NQC), dependent on the radial momentum, to the waveform and radiation reaction. A robust method to speed up the waveform generation is the postadiabatic iteration to approximate the solution of the EOB Hamiltonian equations. In this work, we assess the performances of a fast NQC prescription in combination to the postadiabatic method for generating multipolar gravitational waves. The outlined approach allows a consistent treatment of NQC in both the waveform and the radiation-reaction, does not require iterative procedures to achieve high faithfulness, and can be efficiently employed for parameter estimation. Comparing to 611 NR simulations, for total mass $10M_{\odot }\le M\le 200M_{\odot }$ and using the Advanced LIGO noise, the model has EOB/NR unfaithfulness well below 0.01, with 78.5% of the cases below 0.001. We apply the model to the parameter estimation of GW150914 exploring the impact of the new NQC and of the higher modes up to $\ell =m=8$.

In this paper, an exact solution of the Kerr black hole surrounded by a cloud of strings in Rastall gravity is obtained by the Newman-Janis algorithm without complexification, and the influence of the string parameter $a_0$ on black hole thermodynamics is studied. Furthermore, according to this black hole solution, we investigate the effect of a cloud of strings on the gravitational deflection of massive particles. For a receiver and a source at infinite distance from the lens object, we use an osculating Riemannian manifold method. While the distance is finite, we apply the generalized Jacobi metric method. For both of the two situations, the Jacobi-Maupertuis-Randers-Finsler metric and Gauss-Bonnet theorem are employed. It is found that the string parameter $a_0$ has obvious modification on the gravitational deflection of massive particles. Our result is reduced to the deflection angle of light by the Kerr black hole surrounded by a cloud of strings in general relativity.

The weak cosmic censorship (WCC) conjecture ensures the deterministic nature of an underlying gravitational theory by prohibiting formations of naked singularities and can be used as a consistency criterion for any viable modification over general relativity (GR). We employ this idea via a general strategy to show that in contrast to the analogous result in GR, it is indeed possible to overcharge such modified extremal black holes. Demanding the validity of WCC, we put some stringent constraints on various parameters of the theory. In particular, for a specific class of charged Einstein-aether black hole, our method is strong enough to reproduce the same bound on the parameter present in the solution obtained previously from entirely different considerations.

Recently, we obtained the simple metrics of a spherically symmetric black hole in a dark matter halo, and extended to the case of rotation. As the characteristic sound of black holes, quasinormal modes (QNMs) are one of the important means to understand black holes currently. Based on these two metrics of a spherically symmetric black hole, we study the QNMs of cold dark matter (CDM) and scalar field dark matter (SFDM) models using the methods of the material field perturbations and the gravitational perturbation, and make comparisons with the Schwarzschild black hole. Our results show that black hole QNMs of CDM and SFDM in a dark matter halo are different from the Schwarzschild black hole, unlike a Schwarzschild black hole with a prominent power-law tail. The different kinds of models of dark matter can be distinguished by their QNMs. The time of QNMs ringing and frequencies increase with increasing parameter $l$. The overall QNMs of CDM are stronger than that of SFDM in the same condition, which is easier to be detected. In addition, QNM frequencies using the sixth-order WKB method and the Prony method are in good agreement.

It has recently been revealed that spinning black holes of the photon-fluid model can support acoustic ‘clouds’—stationary density fluctuations whose spatially regular radial eigenfunctions are determined by the ($2+1$)-dimensional Klein-Gordon equation of an effective massive scalar field. Motivated by this intriguing observation, we use analytical techniques in order to prove a no-short hair theorem for the composed acoustic black hole scalar-clouds configurations. In particular, it is proved that the effective lengths of the stationary bound-state corotating acoustic scalar clouds are bounded from below by the series of inequalities $r_{\mathrm{hair}}>\frac{1+\sqrt{5}}{2}·r_{\mathrm{H}}>r_{\mathrm{null}}$, where $r_{\mathrm{H}}$ and $r_{\mathrm{null}}$ are respectively the horizon radius of the supporting black hole and the radius of the corotating null circular geodesic that characterizes the acoustic spinning black hole spacetime.

Despite the success of the standard $\mathrm{\Lambda }\mathrm{CDM}$ model of cosmology, recent data improvements have made tensions emerge between low- and high-redshift observables, most importantly in determinations of the Hubble constant $H_0$ and the (rescaled) clustering amplitude $S_8$. The high-redshift data, from the cosmic microwave background (CMB), crucially relies on recombination physics for its interpretation. Here we study how small-scale baryon inhomogeneities (i.e., clumping) can affect recombination and consider whether they can relieve both the $H_0$ and $S_8$ tensions. Such small-scale clumping, which may be caused by primordial magnetic fields or baryon isocurvature below kpc scales, enhances the recombination rate even when averaged over larger scales, shifting recombination to earlier times. We introduce a flexible clumping model, parametrized via three spatial zones with free densities and volume fractions, and use it to study the impact of clumping on CMB observables. We find that increasing $H_0$ decreases both ${\mathrm{\Omega }}_m$ and $S_8$, which alleviates the $S_8$ tension. On the other hand, the shift in ${\mathrm{\Omega }}_m$ is disfavored by the low-$z$ baryon-acoustic-oscillations measurements. We find that the clumping parameters that can change the CMB sound horizon enough to explain the $H_0$ tension also alter the damping tail, so they are disfavored by current Planck 2018 data. We test how the CMB damping-tail information rules out changes to recombination by first removing $\ell >1000$ multipoles in Planck data, where we find that clumping could resolve the $H_0$ tension. Furthermore, we make predictions for future CMB experiments, as their improved damping-tail precision can better constrain departures from standard recombination. Both the Simons Observatory and CMB-S4 will provide decisive evidence for or against clumping as a resolution to the $H_0$ tension.

Lorentz invariance violation in quantum gravity (QG) models or a nonzero photon mass, $m_{\gamma }$, would lead to an energy-dependent propagation speed for photons, such that photons of different energies from a distant source would arrive at different times, even if they were emitted simultaneously. By developing source-by-source, Monte Carlo-based forward models for such time delays from gamma ray bursts, and marginalizing over empirical noise models describing other contributions to the time delay, we derive constraints on $m_{\gamma }$ and the QG length scale, ${\ell }_{\mathrm{QG}}$, using spectral lag data from the BATSE satellite. We find $m_{\gamma }<4.0\times {10}^{-5}h\mathrm{eV}/c^2$ and ${\ell }_{\mathrm{QG}}<5.3\times {10}^{-18}h{\mathrm{GeV}}^{-1}$ at 95% confidence, and demonstrate that these constraints are robust to the choice of noise model. The QG constraint is among the tightest from studies which consider multiple gamma ray bursts and the constraint on $m_{\gamma }$, although weaker than from using radio data, provides an independent constraint which is less sensitive to the effects of dispersion by electrons.

If primordial black holes (PBHs) seeded the supermassive black holes (SMBHs) at the centers of high-redshift quasars, then the gas surrounding these black holes may reveal nucleosynthetic clues to their primordial origins. We present predictions of altered primordial abundances around PBHs massive enough to seed SMBHs at $z\approx 6–7.5$. We find that if PBHs with initial masses of $\sim {10}^5{\mathrm{M}}_{\odot }$ are responsible for such SMBHs, they may produce primordial deuterium and Helium fractions enhanced by $\ge 10\%$, and lithium abundance depleted by $\ge 10\%$, at distances of up to $\approx$ a comoving kiloparsec away from the black hole after decoupling. We estimate that $\sim {10}^8{\mathrm{M}}_{\odot }$ of gas is enhanced (or depleted) by at least one percent. Evidence of these modified primordial deuterium, helium, and lithium abundances could still be present if this circum-PBH gas remains unaccreted by the SMBH and in or near the host galaxies of high-redshift quasars. Measuring the abundance anomalies will be challenging, but could offer a novel way to reveal the primordial origin of such SMBH seeds.

We investigate the renormalization group optimized perturbation theory (RGOPT) at the next-to-next-to-leading order (NNLO) for the thermal scalar field theory. From comparing three thus available successive RGOPT orders, we illustrate the efficient resummation and very good apparent convergence properties of the method. In particular, the remnant renormalization scale dependence of thermodynamical quantities is drastically improved as compared to both standard perturbative expansions and other related resummation methods, such as the screened perturbation theory. Our present results thus constitute a useful first NNLO illustration in view of NNLO applications of this approach to the more involved thermal QCD.

A model of two coupled complex scalar fields is studied at finite temperature and under an external magnetic field. The results are obtained in the context of the nonperturbative method of the optimized perturbation theory and contrasted with those obtained in perturbation theory and in the one-loop approximation. The emergence of phenomena related to inverse symmetry breaking and symmetry nonrestoration are analyzed.

Axionlike particles (ALPs) are predicted by many extensions of the Standard Model. When ALP mass lies in the range of MeV–GeV, the cosmology and astrophysics will be largely irrelevant. In this work, we investigate such light ALPs through the ALP-strahlung process $pp\to Va(\to \gamma \gamma )$ at the 14 TeV LHC with an integrated luminosity of $3000{\mathrm{fb}}^{-1}$ (high-luminosity LHC). With the photon-jet algorithm, we demonstrate that our approach can probe the mass range of ALPs, which has been inaccessible in previous LHC experiments. The obtained result can surpass the existing limits on ALP-photon coupling in the ALP mass range from 0.3 to 10 GeV.

The quark mass function is computed both by solving the quark propagator Dyson-Schwinger equation and from lattice simulations implementing overlap and domain-wall fermion actions for valence and sea quarks, respectively. The results are examined and are seen to produce a very congruent picture, showing a remarkable agreement for the explored range of current-quark masses. The effective running interaction is based on a process-independent charge rooted on a particular truncation of the Dyson-Schwinger equations in the gauge sector, establishing a link from there to the quark sector and inspiring a correlation between the emergence of gluon and hadron masses.

The hadron resonance gas (HRG) model is often believed to correctly describe the confined phase of QCD. This assumption is the basis of many phenomenological works on QCD thermodynamics and of the analysis of hadron yields in relativistic heavy ion collisions. We use first principle lattice simulations to calculate corrections to the ideal HRG model. Namely, we determine the subleading fugacity expansion coefficients of the grand canonical free energy, receiving contributions from processes like kaon-kaon or baryon-baryon scattering. We achieve this goal by performing a two dimensional scan on the imaginary baryon number chemical potential (${\mu }_B$)—strangeness chemical potential (${\mu }_S$) plane, where the fugacity expansion coefficients become Fourier coefficients. We carry out a continuum limit estimation of these coefficients by performing lattice simulations with temporal extents of $N_{\tau }=8$, 10, 12 using the 4stout-improved staggered action. We then use the truncated fugacity expansion to extrapolate ratios of baryon number and strangeness fluctuations and correlations to finite chemical potentials. Evaluating the fugacity expansion along the crossover line, we reproduce the trend seen in the experimental data on net-proton fluctuations by the STAR collaboration.

We calculate the production and polarization of direct $J/\psi$ in the improved color evaporation model at $\mathcal{O}({\alpha }_s^3)$ in the collinear factorization approach. We present the first calculation of polarization parameters ${\lambda }_{\vartheta }$, ${\lambda }_{\phi }$, and ${\lambda }_{\vartheta \phi }$ in the helicity and the Collins-Soper frames as well as the frame-invariant polarization parameter $\tilde{\lambda }$ as a function of transverse momentum. We find agreement with both $J/\psi$ cross sections and the invariant polarization parameters at small and moderate $p_T$.

A resonance has been observed by the ANDY Collaboration at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory in $\mathrm{Cu}+\mathrm{Au}$ collisions at center-of-mass energy $\sqrt{s}=200\mathrm{GeV}$ and at forward rapidity with an average mass of 18.15 GeV. The Collaboration suggests that it is a $b\overline{b}b\overline{b}$ tetraquark state decaying to two $\mathrm{\Upsilon }(1\mathrm{S})$ states, each measured through the $\mathrm{\Upsilon }\to ggg$ channel. Here, their suggestion is investigated assuming that the two $\mathrm{\Upsilon }$ states are produced through the materialization of a $|uudb\overline{b}b\overline{b}⟩$ Fock state in the projectile. The $\mathrm{\Upsilon }$ pair mass and rapidity distributions arising from such a state are calculated. The production of an $X_b(b\overline{b}b\overline{b})$ tetraquark state from the same Fock configuration is also investigated. The dependence on bottom quark mass and their transverse momentum range is also studied. It is found that double $\mathrm{\Upsilon }$ production from these $|uudb\overline{b}b\overline{b}⟩$ states peak in the rapidity range of the ANDY detector. The $\mathrm{\Upsilon }$ pair and $X_b$ masses are, however, higher than the mass reported by the ANDY Collaboration. Thus the results obtained from these calculations are incompatible with the ANDY result. They are, however, compatible with previous predictions of $b\overline{b}b\overline{b}$ tetraquark masses.

A sizable $\cos 4\varphi$ azimuthal asymmetry in exclusive dipion production near ${\rho }^0$ resonance peak in ultraperipheral heavy-ion collisions recently has been reported by STAR collaboration. We show that both elliptic gluon Wigner distribution and final-state soft photon radiation can give rise to this azimuthal asymmetry. The fact that the QED effect alone severely underestimates the observed asymmetry might signal the existence of the nontrivial correlation in quantum phase distribution of gluons.

We evaluate all two-point correlation functions of the Curci-Ferrari (CF) model in four dimensions and in the presence of mass-degenerate fundamental quark flavors, as a natural extension of an earlier investigation in the quenched approximation. In principle, the proper account of chiral symmetry breaking ($\chi \mathrm{SB}$) and the corresponding dynamical generation of a quark-mass function within the CF model requires one to go beyond perturbation theory [M. Peláez, U. Reinosa, J. Serreau, M. Tissier, and N. Wschebor, Phys. Rev. D 103, 094035 (2021)]. However, it is interesting to assess whether a perturbative description applies to correlation functions that are not directly sensitive to $\chi \mathrm{SB}$, such as the gluon, ghost and quark dressing functions. We compare our two-loop results for these form factors to QCD lattice data in the two-flavor case for two different values of the pion mass, one that is relatively far from the chiral limit, and one that is closer to the physical value. Our results confirm that the QCD gluon and ghost dressing functions are well described by a perturbative approach within the CF model, as already observed at one-loop order [M. Peláez, M. Tissier, and N. Wschebor, Phys. Rev. D 90, 065031 (2014)]. Our new main result is that the quark dressing function is also well captured by the perturbative approach, but only starting at two-loop order, as also anticipated [M. Peláez, M. Tissier, and N. Wschebor, Phys. Rev. D 90, 065031 (2014)]. The quark-mass function predicted by the CF model at two-loop order is in good agreement with the data if the quarks are not too light but it shows some clear tension with respect to the two-loop CF dressing functions in the close to physical case, as expected. Interestingly, however, we find that there is much less tension between the nonperturbative quark-mass function, as it can be obtained from lattice simulations or from M. Peláez, U. Reinosa, J. Serreau, M. Tissier, and N. Wschebor, Phys. Rev. D 103, 094035 (2021), and the two-loop CF dressing functions, which confirms the perturbative nature of the latter.

The GRAVITY Collaboration achieved a remarkable detection of the orbital precession of the S2 star around the Galactic Center supermassive black hole, providing yet another proof of the validity of general relativity. The departure from the Schwarzschild precession is encoded in the parameter $f_{\mathrm{SP}}$, which multiplies the predicted general relativistic precession. This parameter results in $f_{\mathrm{SP}}=1.10\pm 0.19$, which is consistent with general relativity ($f_{\mathrm{SP}}=1$) at $1\sigma$ level. Nevertheless, this parameter may also hide an effect of the modified theories of gravity. Thus, we consider the orbital precession due to the Yukawa-like gravitational potential arising in the weak field limit of $f(R)$-gravity, and we use the current bound on the $f_{\mathrm{SP}}$ to constrain the strength and the scale length of the Yukawa-like potential. No deviations from general relativity are revealed at the scale of $\lambda <6300\mathrm{AU}$ with the strength of the Yukawa potential restricted to $\delta =-{0.01}_{-0.14}^{+0.61}$.