Fully-heavy tetraquark states, i.e., $cc\overline{c}\overline{c}$, $bb\overline{b}\overline{b}$, $bb\overline{c}\overline{c}$ ($cc\overline{b}\overline{b}$), $cb\overline{c}\overline{c}$, $cb\overline{b}\overline{b}$, and $cb\overline{c}\overline{b}$, are systematically investigated by means of a nonrelativistic quark model based on lattice-QCD studies of the two-body $Q\overline{Q}$ interaction, which exhibits a spin-independent Cornell potential along with a spin-spin term. The four-body problem is solved using the Gaussian expansion method; additionally, the so-called complex scaling technique is employed so that bound, resonance, and scattering states can be treated on the same footing. Moreover, a complete set of four-body configurations, including meson-meson, diquark-antidiquark, and K-type configurations, as well as their couplings, are considered for spin-parity quantum numbers $J^{P(C)}=0^{+(+)}$, $1^{+(\pm )}$, and $2^{+(+)}$ in the $S$-wave channel. Several narrow resonances, with two-meson strong decay widths less than 30 MeV, are found in all of the tetraquark systems studied. Particularly, the fully-charm resonances recently reported by the LHCb Collaboration, at the energy range between 6.2 and 7.2 GeV in the di-$J/\psi$ invariant spectrum, can be well identified in our calculation. Focusing on the fully-bottom tetraquark spectrum, resonances with masses between 18.9 and 19.6 GeV are found. For the remaining charm-bottom cases, the masses are obtained within a energy region from 9.8 GeV to 16.4 GeV. All these predicted resonances can be further examined in future experiments.

We implement the Dyson-Schwinger equation approach to study the mass dependence of pseudocritical temperature of QCD crossover at zero chemical potential. For the quark-gluon vertex, we take simply the rainbow approximation, while for the gluon propagator, we make use of various dressing functions. We analyze the scaling behavior with these different gluon models and obtain the critical exponent consistent with the mean field value for 3D O(4) universality class, which means the rainbow truncation will lead to the mean field result, regardless of the gluon dressing model. The size of critical region is up to $m_0\le 1–2\mathrm{MeV}$ in this mean field approximation, which sets naturally an upper bound of the critical region since the fluctuations beyond mean field usually diminish the critical region. The pseudocritical temperature corresponds to the maximum value of the chiral susceptibility, and for the chiral susceptibility of a certain percentage of its maximum value, the corresponding temperature might be mass independent. We analyze this percentage and studied the pion mass range in which the corresponding temperature remain constant. The results show that this percentage and the pion mass range depend on the details of interaction kernel, which differs in gluon models.

We study the stability against infinitesimal radial oscillations of neutron stars generated by a set of equations of state obtained from first-principle calculations in cold and dense QCD and constrained by observational data. We consider mild and large violations of the conformal bound, $c_s=1/\sqrt{3}$, in stars that can possibly contain a quark matter core. Some neutron star families in the mass-radius diagram become dynamically unstable due to large oscillation amplitudes near the core.

Millicharged particles (mCPs) are hypothesized particles possessing an electric charge that is a fraction of the charge of the electron. We report a search for mCPs with charges $\gtrsim {10}^{-4}e$ that improves sensitivity to their abundance in matter by roughly two orders of magnitude relative to previous searches. This search is sensitive to such particles over a wide range of masses and charges for which they can form stable bound states with matter, corresponding to a gap in parameter space that is beyond the reach of previous searches from accelerators, colliders, cosmic-ray experiments, and cosmological constraints.

It has been shown that non-Abelian solitonic vortex strings supported in four-dimensional (4D) $\mathcal{N}=2$ supersymmetric QCD (SQCD) with the $\mathrm{U}(N=2)$ gauge group and $N_f=4$ quark flavors behave as critical superstrings. In addition to four translational moduli, the non-Abelian strings under consideration carry six orientational and size moduli. Together they form a ten-dimensional space required for a superstring to be critical. The target space of the string sigma model is a product of the flat four-dimensional space ${\mathbb{R}}^4$ and a Calabi-Yau noncompact threefold $Y_6$, namely, the conifold. The spectrum of low lying closed string states in the associated type IIA string theory was found and interpreted as a spectrum of hadrons in 4D $\mathcal{N}=2$ SQCD. In particular, the lowest string state appears to be a massless Bogomolny-Prasad-Sommerfeld baryon associated with the deformation of the complex structure modulus $b$ of the conifold. Here we address a problem of switching on quark masses in 4D SQCD, which classically breaks the world sheet conformal invariance in the string sigma model. To avoid this problem we follow a standard string theory approach and use a flux “compactification” to lift the complex structure modulus of the conifold. Namely, we find a solution of supergravity equations of motion with nonzero Neveu-Schwarz 3-form flux. It produces a potential for the baryon $b$, which leads to the runaway vacuum. Using field theory arguments, we interpret 3-form flux in terms of a particular choice of quark masses in 4D SQCD. At the runaway vacuum the conifold degenerates to lower dimensions. We interpret this as a flow from a non-Abelian string to an Abelian one.

We present the manifestly covariant Lagrangian of a massless polarized particle that implies all dynamic and algebraic equations as the conditions of extreme of this variational problem. The model allows for minimal interaction with a gravitational field, leading to the equations, coinciding with Maxwell equations in the geometrical optics approximation. The model allows also a wide class of nonminimal interactions, which suggests an alternative way to study the electromagnetic radiation beyond the leading order of geometrical optics. As a specific example, we construct a curvature-dependent interaction in Schwarzschild spacetime, predicting the Faraday rotation of polarization plane, linearly dependent on the wave frequency. As a result, the Schwarzschild spacetime generates a kind of angular rainbow of light: waves of different frequencies, initially linearly polarized in one direction, acquire different orientations of their polarization planes when propagated along the same ray.

We discuss the far-from-equilibrium evolution of ${\varphi }^3$ theory in $1+1$ dimensions with the temporal functional renormalization group. In particular, we show that this manifestly causal approach leads to novel one-loop exact equations for fully dressed correlation functions. Within this setup, we numerically compute the dynamical propagator. Its behavior suggests self-similarity far from equilibrium in a restricted momentum regime. We discuss the scaling exponents for our solution, as well as the numerical satisfaction of energy and particle number conservation. We also derive a simple exact representation of the expectation value of the energy-momentum tensor solely in terms of the propagator.

In this paper, we present our study on the $T\overline{T}$ deformation of nonrelativistic complex scalar field theory. We find the closed form of the deformed Lagrangian by using the perturbation and the method of characteristics. Furthermore we compute the exact energy spectrum of the deformed free theory by using the Brillouin-Wigner perturbation theory in an appropriate regularization scheme.

There is a vast literature showing the connection between a deformed relativistic kinematics and a curved momentum space and, in particular, how the former can be obtained from the geometrical properties of the latter. However, there is not any mention about the geometry of a multiparticle system making manifest a possible modification in the metric of one particle due to the presence of others. In this work, we explore how a curved momentum metric depending on the particles involved in an interaction arises when considering a process. We also show that the principle of relative locality obtained in doubly special relativity from an action is achieved in this geometrical framework in a direct fashion. Moreover, this formalism allows us to generalize this principle when a curvature of spacetime is present in a natural way. Furthermore this geometrical setup allows us to define a new momentum dependent space-time coordinates for a multiparticle system in which locality of interactions is recovered.

We show that rotating black holes do not experience any tidal deformation when they are perturbed by a weak and adiabatic gravitational field. The tidal deformability of an object is quantified by the so-called “Love numbers,” which describe the object’s linear response to its external tidal field. In this work, we compute the Love numbers of Kerr black holes and find that they vanish identically. We also compute the dissipative part of the black hole’s tidal response, which is nonvanishing due to the absorptive nature of the event horizon. Our results hold for arbitrary values of black hole spin, for both the electric-type and magnetic-type perturbations, and to all orders in the multipole expansion of the tidal field. The boundary conditions at the event horizon and at asymptotic infinity are incorporated in our study, as they are crucial for understanding the way in which these tidal effects are mapped onto gravitational-wave observables. In closing, we address the ambiguity issue of Love numbers in general relativity, which we argue is resolved when those boundary conditions are taken into account. Our findings provide essential inputs for current efforts to probe the nature of compact objects through the gravitational waves emitted by binary systems.

The spaceborne gravitational wave (GW) detectors LISA and TAIJI are planned to be launched in the 2030s. The dual detectors with comparable sensitivities will form a network observing GWs with significant advantages. In this work, we investigate the three possible LISA-TAIJI networks for the different location and orientation compositions of the LISA orbit ($+60°$ inclination and trailing the Earth by 20°) and alternative TAIJI orbit configurations, including TAIJIp ($+60°$ inclination and leading the Earth by 20°), TAIJIc ($+60°$ inclination and colocated with LISA), and TAIJIm ($-60°$ inclination and leading the Earth by 20°). Of the three LISA-TAIJI configurations, the LISA-TAIJIm network shows the best performance in the sky localization and polarization determination for massive binary systems due to its better complementary antenna pattern, and LISA-TAIJIc could achieve the best cross-correlation and observe the stochastic GW background with optimal sensitivity.

In the path integral formulation of the reduced phase space loop quantum gravity (LQG), we propose a new approach to allow the spatial cubic lattice (graph) to change dynamically in the physical time evolution. The equations of motion of the path integral derive the effective dynamics of cosmology from the full LQG, when we focus on solutions with homogeneous and isotropic symmetry. The resulting cosmological effective dynamics with the dynamical lattice improves the effective dynamics obtained earlier from the path integral with a fixed spatial lattice: The improved effective dynamics recovers the Friedmann-Lemaître-Robertson-Walker cosmology at low energy density and resolves the big-bang singularity with a bounce. The critical density ${\rho }_c$ at the bounce is Planckian ${\rho }_c\sim {\mathrm{\Delta }}^{-1}$, where $\mathrm{\Delta }$ is a Planckian area serving as a certain UV cutoff of the effective theory. The effective dynamics gives the unsymmetric bounce and has the de Sitter (dS) spacetime in the past of the bounce. The cosmological constant ${\mathrm{\Lambda }}_{\mathrm{eff}}$ of the dS spacetime is emergent from the quantum effect ${\mathrm{\Lambda }}_{\mathrm{eff}}\sim {\mathrm{\Delta }}^{-1}$. These results are qualitatively similar to the properties of $\overline{\mu }$-scheme loop quantum cosmology. Moreover, we generalize the earlier path integral formulation of the full LQG by taking into account the coupling with an additional real scalar field, which drives the slow-roll inflation of the effective cosmological dynamics. In addition, we discuss the cosmological perturbation theory on the dynamical lattice and the relation to the Mukhanov-Sasaki equation.

Starting from the original Einstein action, sometimes called the Gamma squared action, we propose a new setup to formulate modified theories of gravity. This can yield a theory with second order field equations similar to those found in other popular modified gravity models. Using a more general setting the theory gives fourth order equations. This model is based on the metric alone and does not require more general geometries. It is possible to show that our new theory and the recently proposed $f(Q)$ gravity models are equivalent at the level of the action and at the level of the field equations, provided that appropriate boundary terms are taken into account. Our theory can also reproduce $f(R)$ gravity, which is an expected result. Perhaps more surprisingly, we show that this equivalence extends to $f(T)$ gravity at the level of the action and its field equations, provided that appropriate boundary terms are taken in account. While these three theories are conceptually different and are based on different geometrical settings, we can establish the necessary conditions under which their field equations are the same. The final part requires matter to couple minimally to gravity. Through this work we emphasize the importance played by boundary terms which are at the heart of our approach.

While independent observations have been made regarding the behavior of effective quasinormal mode (QNM) potentials within the large angular momentum limit, we demonstrate analytically here that a uniform expression emerges for nonrotating, higher-dimensional, and spherically symmetric black holes (BHs) in this regime for fields of integer and half-integer spin in asymptotically flat and de Sitter BH contexts; a second uniform expression arises for these QNM potentials in anti–de Sitter BH spacetimes. We then proceed with a numerical analysis based on the multipolar expansion method recently proposed by Dolan and Ottewill to determine the behavior of quasinormal frequencies (QNFs) for varying BH parameters in the eikonal limit. We perform a complete study of Dolan and Ottewill’s method for perturbations of spin $s\in \{0,1/2,1,3/2,2\}$ in four-dimensional Schwarzschild, Reissner-Nordström, and Schwarzschild–de Sitter spacetimes, clarifying expressions and presenting expansions and results to higher orders [$\mathcal{O}(L^{-6})$] than many of those presented in the literature [$\sim \mathcal{O}(L^{-2})$]. We find good agreement with known results of QNFs for low-lying modes; in the large-$\ell$ regime, our results are highly consistent with those of Konoplya’s sixth-order WKB method. We confirm a universality in the trends of physical features recorded in the literature for the low-lying QNFs (that the real part grows indefinitely, the imaginary tends to a constant as $\ell \to \infty$, etc.) as we approach large values of $\ell$ within these spacetimes, and explore the consequent interplay between BH parameters and QNFs in the eikonal limit.

We discuss features of the inflaton potential that can lead to a strong enhancement of the power spectrum of curvature perturbations. We show that a steep steplike feature induces an enhancement of the spectrum by several orders of magnitude within a certain range of scales. It also produces a distinctive oscillatory pattern. We study the origin of the oscillations and the additive effect of several steps. We analyze a simplified potential, with an ad hoc introduction of steps at certain field values, but also discuss the possible application to supergravity models.

In this work, we first discuss the possibility that dark energy models with negative energy density values in the past can alleviate the $H_0$ tension, as well as the discrepancy with the baryon acoustic oscillation (BAO) Lyman-$\alpha$ data, both which prevail within the $\mathrm{\Lambda }\mathrm{CDM}$ model. We then investigate whether two minimal extensions of the $\mathrm{\Lambda }\mathrm{CDM}$ model, together or separately, can successfully realize such a scenario: (i) the spatial curvature, which, in the case of spatially closed universe, mimics a negative density source and (ii) simple-graduated dark energy (gDE), which promotes the null inertial mass density of the usual vacuum energy to an arbitrary constant—if negative, the corresponding energy density decreases with redshift similar to the phantom models, but unlike them crosses below zero at a certain redshift. We find that, when the Planck data are not included in the observational analysis, the models with simple-gDE predict interesting and some significant deviations from the $\mathrm{\Lambda }\mathrm{CDM}$ model. In particular, a spatially closed universe along with a simple-gDE of positive inertial mass density, which work in contrast to each other, results in minor improvement to the $H_0$ tension. The joint dataset, including the Planck data, presents no evidence for a deviation from spatial flatness but almost the same evidence for a cosmological constant and the simple-gDE with an inertial mass density of order $\mathcal{O}({10}^{-12}){\mathrm{eV}}^4$. The latter case predicts almost no deviation from the $\mathrm{\Lambda }\mathrm{CDM}$ model up until today—so that it results in no improvement regarding the BAO Ly-$\alpha$ data—except that it slightly aggravates the $H_0$ tension. We also study via dynamical analysis the history of the Universe in the models, as the simple-gDE results in futures different than the de Sitter future of the $\mathrm{\Lambda }\mathrm{CDM}$ model.

Light bosonic (axionlike) dark matter may form Bose stars—clumps of nonrelativistic Bose-Einstein condensate supported by self-gravity. We study rotating Bose stars composed of condensed particles with nonzero angular momentum $l$. We analytically prove that these objects are unstable at arbitrary $l\ne 0$ if particle self-interactions are attractive or negligibly small. They decay by shedding off the particles and transporting the angular momentum to the periphery of the system until a Saturn-like configuration appears: One (or several) spin-zero Bose stars and clouds of diffuse particles orbit around the mutual center. In the case of no self-interactions, we calculate the profiles and dominant instability modes of the rotating stars: numerically at $1\le l\le 15$ and analytically at $l\gg 1$. Notably, their lifetimes are always comparable to the inverse binding energies; hence, these objects cannot be considered long-living. Finally, we numerically show that in models with sufficiently strong repulsive self-interactions the Bose star with $l=1$ is stable.

Many astrophysical bursts can recur, and their time series structure or pattern could be closely tied to the emission and system physics. While analysis of periodic events is well established, some sources, e.g., some fast radio bursts and soft gamma-ray emitters, are suspected of more subtle and less explored periodic windowed behavior: the bursts themselves are not periodic, but the activity only occurs during periodic windows. We focus here on distinguishing periodic windowed behavior from merely clustered events through time clustering analysis, using techniques analogous to spatial clustering, demonstrating methods for identifying and characterizing the behavior. An important aspect is accounting for the “curious incident of the dog in the night time”—lack of bursts carries information. As a worked example, we analyze six years of data from the soft gamma repeater $\mathrm{SGR}1935+2154$, deriving a window period of 231 days and 55% duty cycle.

The LIGO and Virgo observatories have reported 39 new gravitational-wave detections during the first part of the third observation run, bringing the total to 50. Most of these new detections are consistent with binary black-hole coalescences, making them suitable targets to search for gravitational-wave memory, a nonlinear effect of general relativity. We extend a method developed in previous publications to analyze these events to determine a Bayes factor comparing the memory hypothesis to the no-memory hypothesis. Specifically, we calculate Bayes factors using two waveform models with higher-order modes that allow us to analyze events with extreme mass ratios and precessing spins, both of which have not been possible before. Depending on the waveform model, we find a combined $\ln {\mathrm{BF}}_{\mathrm{mem}}=0.024$ or $\ln {\mathrm{BF}}_{\mathrm{mem}}=0.049$ in favor of memory. This result is consistent with recent predictions that indicate $\mathcal{O}(2000)$ binary black-hole detections will be required to confidently establish the presence or absence of memory.

The Milky Way magnetic field can trigger conversions between photons and axionlike particles (ALPs), leading to peculiar features on the observable photon spectra. Previous studies considered only the regular component of the magnetic field. However, observations consistently show the existence of an additional turbulent component, with a similar strength and correlated on a scale of a few 10 pc. We investigate the impact of the turbulent magnetic field on the ALP-photon conversions, characterizing the effects numerically and analytically. We show that the turbulent magnetic field can change the conversion probability by up to a factor of two and may lead to observable irregularities in the observable photon spectra from different astrophysical sources.