We derive a unified expansion law for our Universe from the first law of thermodynamics on the apparent horizon, where entropic evolution depicts the emergence of cosmic space. The derivation advances a general form for degrees of freedom on the surface and bulk, which provides a natural generalization for the expansion law proposed by Padmanabhan. The general expression for the surface degrees of freedom differs from the natural expectation, $N_{\mathrm{sur}}=4S$ in the emergent gravity paradigm for general theories of gravity. The derivation also provides justification for the selection of Gibbons-Hawking temperature in the original expansion law and for the use of areal volume in the nonflat Friedmann-Robertson-Walker universe. Since the unified expansion law exclusively depends on the form of entropy, the method is applicable to obtain the expansion law in any gravity theory without any additional ad hoc assumptions. From the general expansion law, we have obtained the expansion law corresponding to different theories of gravity like ($n+1$) Einstein, Gauss-Bonnet, Lovelock, and Hořava-Lifshitz. We also obtained the expansion law for nonextensive entropy like Tsallis entropy from the unified expansion law.

We investigate the second order gravitational waves induced by the primordial scalar and tensor perturbations during a radiation-dominated era. The explicit expressions of the power spectra of the second order GWs are presented. We calculate the energy density spectra of the second order GWs for the monochromatic primordial power spectra ${\mathcal{P}}_{\zeta }=A_{\zeta }{k}_{*}\delta (k-k_{*})$ and ${\mathcal{P}}_h=A_h{k}_{*}\delta (k-k_{*})$. For large $k$ $(k>k_{*})$, the primordial tensor perturbation will affect the total power spectrum of second order GWs significantly. For $f_{*}=1.3\times {10}^{-3}$ and $A_{\zeta }=0.02$, the effects of the primordial tensor perturbation will lead to an around 100% increase of the signal-to-noise ratio (SNR) for LISA observations if the tensor-to-scalar ratio $r=A_h/A_{\zeta }>0.4$.

Star clusters (SCs) and active galactic nuclei (AGNs) are promising sites for the occurrence of hierarchical black hole (BH) mergers. We use simple models to compare hierarchical BH mergers in two of the dynamical formation channels. We find that the primary mass distribution of hierarchical mergers in AGNs is higher than that in SCs, with the peaks of $\sim 50{\mathrm{M}}_{\odot }$ and $\sim 13{\mathrm{M}}_{\odot }$, respectively. The effective spin (${\chi }_{\mathrm{eff}}$) distribution of hierarchical mergers in SCs is symmetrical around zero as expected and $\sim 50\%$ of the mergers have $|{\chi }_{\mathrm{eff}}|>0.2$. The distribution of ${\chi }_{\mathrm{eff}}$ in AGNs is narrow and prefers positive values with the peak of ${\chi }_{\mathrm{eff}}\ge 0.3$ due to the assistance of AGN disks. BH hierarchical growth efficiency in AGNs, with at least $\sim 30\%$ of mergers being hierarchies, is much higher than the efficiency in SCs. Furthermore, there are obvious differences in the mass ratios and effective precession parameters of hierarchical mergers in SCs and AGNs. We argue that the majority of the hierarchical merger candidates detected by LIGO-Virgo may originate from the AGN channel as long as AGNs get half of the hierarchical merger rate.

We present a fit to observational data in an asymmetric self-interacting dark matter model using our recently calculated cross sections that incorporate both $t$-channel and $u$-channel exchanges in the scattering of identical particles. We find good fits to the data ranging from dwarf galaxies to galaxy clusters and equivalent relative velocities from $\sim 20\mathrm{km}/\mathrm{s}$ to $\gtrsim 10^3\mathrm{km}/\mathrm{s}$. We compare our results with previous fits that used only $t$-channel exchange contributions to the scattering.

A novel instrumented baffle surrounding the suspended end mirror in the input mode cleaner cavity of the Virgo interferometer was installed in Spring 2021. Since then, the device has been regularly operated in the experiment, and the data collected show good stability. The baffle will operate in the upcoming O4 observation run, serving as a demonstrator of the technology designed to instrument the baffles in front of the main mirrors in time for O5. In this paper, we present a detailed description of the baffle design, including mechanics, front-end electronics, and data acquisition as well as optical and vacuum compatibility tests, calibration and installation procedures, and performance results.

We present a phenomenological description of the LHCb data for the magnitudes and phases of the ${\pi }^{-}{\pi }^{+}$ $S$-wave amplitudes in the $D^{+}\to {\pi }^{-}{\pi }^{+}{\pi }^{+}$ and $D_s^{+}\to {\pi }^{-}{\pi }^{+}{\pi }^{+}$ decays. We operate within a simple model that takes into account the known pair interactions of particles in coupled channels. The seed complex amplitudes for various intermediate state production are assumed to be independent of the energy; their values are determined by fitting. This model gives a satisfactory description of virtually all features of the energy dependence of the experimentally measured $S$-wave amplitudes in the $D^{+}\to {\pi }^{-}{\pi }^{+}{\pi }^{+}$ and $D_s^{+}\to {\pi }^{-}{\pi }^{+}{\pi }^{+}$ decays in the regions $2m_{\pi }<m_{{\pi }^{-}{\pi }^{+}}<1.39\mathrm{GeV}$ and $2m_{\pi }<m_{{\pi }^{-}{\pi }^{+}}<1.29\mathrm{GeV}$, respectively.

We study the non-Abelian $SU(2{)}_D$ extension of the $U(1{)}_D$ Stueckelberg portal, which plays the role of mediator between the Standard Model (SM) and dark sector. This portal is specified by the Stueckelberg mechanism for generation of dark gauge boson masses. The proposed $U(1{)}_D\otimes SU(2{)}_D$ Stueckelberg portal has a connection with SM matter fields, in analogy with the familon model. We derive bounds on the couplings of dark portal bosons and SM particles, which govern diagonal and nondiagonal flavor transitions of quarks and leptons.

Measurements of the branching ratios of $B\to D^{(*)}\tau \overline{\nu }/B\to D^{(*)}\ell \overline{\nu }$ and $B_c\to J/\psi \tau \overline{\nu }/B_c\to J/\psi \ell \overline{\nu }$ by the BABAR, Belle and LHCb collaborations consistently point towards an abundance of taus compared to channels with light leptons. However, the ratio ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau \overline{\nu }/{\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\ell \overline{\nu }$ shows a relative deficit in taus. In this paper, we critically address whether data still points towards a coherent pattern of deviations, in particular in light of the sum rule relating these decays in a model-independent way. We find that no common new physics explanation of all ratios is possible (within $2\sigma$ or $1.5\sigma$, depending on the $\mathcal{R}({\mathrm{\Lambda }}_c)$ normalization to light lepton channels). While this inconsistency could be a statistical fluctuation, further measurements are required in order to converge to a coherent pattern of experimental results.

In this paper, we develop the self-learning Monte-Carlo (SLMC) algorithm for non-Abelian gauge theory with dynamical fermions in four dimensions to resolve the autocorrelation problem in lattice QCD. We perform simulations with the dynamical staggered fermions and plaquette gauge action by both in the hybrid Monte-Carlo (HMC) and SLMC for zero and finite temperature to examine the validity of SLMC. We confirm that SLMC can reduce autocorrelation time in non-Abelian gauge theory and reproduce results from HMC. For finite temperature runs, we confirm that SLMC reproduces correct results with HMC, including higher-order moments of the Polyakov loop and the chiral condensate. Besides, our finite temperature calculations indicate that four flavor ${\mathrm{QC}}_2\mathrm{D}$ with $\widehat{m}=0.5$ is likely in the crossover regime in the Colombia plot.

Using data samples of $e^{+}{e}^{-}$ collisions collected with the BESIII detector at eight center-of-mass energy points between 3.49 and 3.67 GeV, corresponding to an integrated luminosity of $670{\mathrm{pb}}^{-1}$, we present the upper limits of Born cross sections and the effective form factor for the process $e^{+}{e}^{-}\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+}$. A fit to the cross sections using a perturbative QCD-derived energy-dependent function shows no significant threshold effect. The upper limit on the measured effective form factor is consistent with a theoretical prediction within the uncertainty of $1\sigma$. These results provide new experimental information on the production mechanism of $\mathrm{\Omega }$.

The Cabibbo-allowed weak radiative decay ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}\gamma$ has been searched for in a sample of ${\mathrm{\Lambda }}_c^{+}{\overline{\mathrm{\Lambda }}}_c^{-}$ pairs produced in $e^{+}{e}^{-}$ annihilations, corresponding to an integrated luminosity of $4.5{\mathrm{fb}}^{-1}$ collected with the BESIII detector at center-of-mass energies between 4.60 and 4.70 GeV. No excess of signal above background is observed, and we set an upper limit on the branching fraction of this decay to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}\gamma )<4.4\times {10}^{-4}$ at a confidence level of 90%, which is in agreement with Standard Model expectations.

Implementing the Wilsonian renormalization group (RG) transformation in a nonperturbative way, we construct an effective holographic dual description with an emergent extradimension identified with an RG scale. Taking the large-$N$ limit, we obtain an equation of motion of an order-parameter field, here the chiral condensate for our explicit demonstration. In particular, an intertwined structure manifests between the first-order RG flow equations of renormalized coupling functions and the second-order differential equation of the order-parameter field, thus referred to as a nonperturbative RG-improved mean-field theory. Assuming translational symmetry as a vacuum state, we solve these nonlinear coupled mean-field equations based on a matching method between UV- and IR-regional solutions. As a result, we find an RG flow from a weakly coupled chiral-symmetric UV fixed point to a strongly correlated chiral-symmetry broken IR fixed point, where the renormalized velocity of Dirac fermions vanishes most rapidly and effective quantum mechanics appears at IR. Furthermore, we translate these RG flows of coupling functions into those of emergent metric tensors and extract out geometrical properties of the emergent holographic spacetime constructed from the UV- and IR-regional solutions. Surprisingly, we obtain the volume law of entanglement entropy in the Ryu-Takayanagi formula, which implies appearance of a black hole type solution in the limit of infinite cutoff even at zero temperature. We critically discuss our field theoretic interpretation for this solution in terms of potentially gapless multiparticle excitation spectra.

We study the consequences of the running Newton’s constant on several key aspects of spherically symmetric charged black holes by performing a renormalization group improvement of the classical Reissner-Nordström metric within the framework of the Einstein-Hilbert truncation in quantum Einstein gravity. In particular, we determine that the event horizon surfaces are stable except for the extremal case and we corroborate the appearance of a new extremality condition at the Planck scale that contributes to hints about the possible existence of a final stage after the black hole evaporation process. We find explicit expressions for the area and surface gravity of the event horizon and we show the existence of an exact form $dS$ with the surface gravity as integrating factor, in contrast to a previous no-go result for axially symmetric spacetimes with null charge. As a consequence, we are able to derive a formula for the state function $S$ as the sum of the area of the classical event horizon plus a quantum correction linear in $\hslash$ and logarithmic in the classical area, in accordance with other approaches. We finally calculate an explicit formula for the Komar mass at the event horizon, and we compare it with the total mass at infinity for a wide domain of values of the black hole parameters $M$, $Q$ and $\overline{w}$, showing a loss of mass which can be interpreted as a consequence of the antiscreening effect of the gravitational field between the event horizon and infinity.

We demonstrate a physical motivation for extending color-dual or Bern-Carrasco-Johansson (BCJ) double-copy construction to include theories with kinematic numerators that obey the same algebraic relations as symmetric structure constants, $d^{abc}=\mathrm{Tr}[\{T^a,T^b\}{T}^c]$. We verify that $U(N_c)$ nonlinear sigma model (NLSM) pions, long known to be color-dual in terms of antisymmetric adjoint factors, $f^{abc}$, are also color-dual in the sense of symmetric color structures, $d^{abc}$, explicitly through six-point scattering. This reframing of NLSM pion amplitudes complements our compositional construction of $d^{abc}$ color-dual higher derivative gauge operators. With adjoint and symmetric color-dual kinematics, we can span all four-point effective photon operators via a double-copy construction using amplitudes from physical theories. We further comment on a tension between locality and adjoint effective numerators, and the implications for spanning gravitational effective operators with nonadjoint kinematics.

We give full details regarding the new Cauchy-characteristic evolution (CCE) system in spectre. The implementation is built to provide streamlined flexibility for either extracting waveforms during the process of a spectre binary compact object simulation or as a stand-alone module for extracting waveforms from worldtube data provided by another code base. Using our recently presented improved analytic formulation, the CCE system is free of pure-gauge logarithms that would spoil the spectral convergence of the scheme. It gracefully extracts all five Weyl scalars, in addition to the news and the strain. The spectre CCE system makes significant improvements on previous implementations in modularity, ease of use, and speed of computation.

Recent investigations of the pseudospectrum in black hole spacetimes have shown that quasinormal mode frequencies suffer from spectral instabilities. This phenomenon may severely affect gravitational-wave spectroscopy and limit precision tests of general relativity. We extend the pseudospectrum analysis to horizonless exotic compact objects that possess a reflective surface arbitrarily close to the Schwarzschild radius and find that their quasinormal modes also suffer from an overall spectral instability. Even though all the modes themselves decay monotonically, the pseudospectrum contours of equal resonance magnitude around the fundamental mode and the lowest overtones can cross the real axis into the unstable regime of the complex plane, unveiling the existence of nonmodal pseudoresonances. A pseudospectrum analysis further predicts that fluctuations to the system may destabilize the object when next to leading-order effects are considered, as the triggering of pseudoresonant growth can break the order expansion of black hole perturbation theory.

We write explicitly the complete Lorentzian metric of a singularity-free spacetime where a black hole transitions into a white hole located in its same asymptotic region. In particular, the metric interpolates between the black and white horizons. The metric satisfies the Einstein field equations up to the tunneling region. The matter giving rise to the black hole is described by the Oppenheimer-Snyder model, corrected with loop-quantum-cosmology techniques in the quantum region. The interior quantum geometry is fixed by a local Killing symmetry, broken at the horizon transition. At large scale, the geometry is determined by two parameters: the mass of the hole and the duration of the transition process. The latter is a global geometrical parameter. We give the full metric outside the star in a single coordinate patch.

We present a detailed analysis of a general relativistic static spherical symmetric distribution in which both the radial and tangential pressures follow a master polytropic equation of state that generalizes the standard treatment and avoids the appearance of singularities in the system. In particular, we find the corresponding Lane-Emden equation and integrate it for a wide range of values of the parameters involved. We explore the parameter space with the aim to find the set of parameters leading to reasonable physical solutions. Also, we considered the effect of spherically symmetric perturbations of the matter variables in order to analyze the possible apparition of cracking within the compact distribution.

We revisit the motion of massless particles with anyonic spin in the horizon of Kerr-Newman geometry. As recently shown, such particles can move within the horizon of the black hole due to the coupling of charges associated with a two-parametric central extension of the two-dimensional Carroll group to the magnetic field generated by the black hole—the so-called “anyonic spin-Hall effect.” We show that the previously computed magnetic field is not invariant under Carroll diffeomorphisms and find another result which respects these symmetries of the horizon. We also consider a more astrophysically relevant case of a (weakly charged) rotating back hole placed in a uniform magnetic field, which could, for instance, be induced by the surrounding plasma. We show that a qualitatively similar magnetic field assisted anyonic spin-Hall effect takes place, even in the absence of black hole rotation. The theoretical possibility of a motion induced by a magnetic monopole is also studied.

We investigate the possibility that the observed behavior of test particles outside galaxies, which is usually explained by assuming the existence of dark matter, is the result of the dynamical evolution of particles in a Weyl type geometry, and its associated conformally invariant Weyl geometric quadratic gravity. As a first step in our investigations we write down the simplest possible conformally invariant gravitational action, constructed in Weyl geometry, and containing the Weyl scalar, and the strength of the Weyl vector only. By introducing an auxiliary scalar field, the theoretical model can be reformulated in the Riemann geometry as scalar-vector-tensor theory, containing a scalar field, and the Weyl vector, respectively. The field equations of the theory are derived in the metric formalism, in the absence of matter. A specific static, spherically symmetric model, in which the Weyl vector has only a radial component, is considered. In this case, an exact analytic solution of the gravitational field equations can be obtained. The behavior of the galactic rotation curves is also considered in detail, and it is shown that an effective geometric mass term, with an associated density profile, can also be introduced. Three particular cases, corresponding to some specific functional forms of the Weyl vector, are also investigated. A comparison of the model with a selected sample of galactic rotation curves is also performed when an explicit breaking of conformal invariance is introduced, which allows the fix of the numerical values of the free parameters of the model. Our results show that Weyl geometric models can be considered as a viable theoretical alternative to the dark matter paradigm.