Cross sections for the process $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\psi$ at center-of-mass energies from 4.128 to 4.950 GeV are measured using data samples with a total integrated luminosity of $21.2{\mathrm{fb}}^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring. The $Y(4230)$ state is observed in the energy dependence of the $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\psi$ cross section for the first time with a statistical significance of $26.0\sigma$. In addition, an enhancement around 4.710 GeV, labeled as the $Y(4710)$, is seen with a statistical significance of $4.2\sigma$. There is no clear structure around 4.484 GeV. Using a fit with a coherent sum of three Breit-Wigner functions, we determine the mass and width of the $Y(4230)$ state to be $4226.9\pm 6.6\pm 22.0\mathrm{MeV}/c^2$ and $71.7\pm 16.2\pm 32.8\mathrm{MeV}$, respectively, and the mass and width of the $Y(4710)$ state to be $4704.0\pm 52.3\pm 69.5\mathrm{MeV}/c^2$ and $183.2\pm 114.0\pm 96.1\mathrm{MeV}$, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the average Born cross section ratio $\frac{{\sigma }^{\text{Born}}(e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\psi )}{{\sigma }^{\text{Born}}(e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi )}$ is measured to be ${0.388}_{-0.028}^{+0.035}\pm 0.016$, or ${0.426}_{-0.031}^{+0.038}\pm 0.018$ if three-body phase space is considered.

Using an $e^{+}{e}^{-}$ collision data sample of $(27.08\pm 0.14)\times {10}^8\psi (3686)$ events collected by the BESIII detector, we report the first observation of ${\chi }_{cJ}\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+}$ ($J=0$, 1, 2) decays with significances of $5.6\sigma$, $6.4\sigma$, and $18\sigma$, respectively, where the ${\chi }_{cJ}$ mesons are produced in the radiative $\psi (3686)$ decays. The branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+})=(3.51\pm 0.54\pm 0.29)\times {10}^{-5}$, $\mathcal{B}({\chi }_{c1}\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+})=(1.49\pm 0.23\pm 0.10)\times {10}^{-5}$, and $\mathcal{B}({\chi }_{c2}\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+})=(4.52\pm 0.24\pm 0.18)\times {10}^{-5}$, where the first and second uncertainties are statistical and systematic, respectively.

We report measurements of the ratios of branching fractions for $B\to {\overline{D}}^{(*)}\pi {\ell }^{+}{\nu }_{\ell }$ and $B\to {\overline{D}}^{(*)}{\pi }^{+}{\pi }^{-}{\ell }^{+}{\nu }_{\ell }$ relative to $B\to {\overline{D}}^{*}{\ell }^{+}{\nu }_{\ell }$ decays with $\ell =e$, $\mu$. These results are obtained from a data sample that contains $772\times {10}^{6}B\overline{B}$ pairs collected near the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. Fully reconstructing both $B$ mesons in the event, we obtain $\frac{\mathcal{B}(B^0\to {\overline{D}}^0{\pi }^{-}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell })}=(7.23\pm 0.36\pm 0.14)\%$, $\frac{\mathcal{B}(B^{+}\to D^{-}{\pi }^{+}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\ell }^{+}{\nu }_{\ell })}=(6.78\pm 0.24\pm 0.18)\%$, $\frac{\mathcal{B}(B^0\to {\overline{D}}^{*0}{\pi }^{-}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell })}=(11.10\pm 0.48\pm 0.23)\%$, $\frac{\mathcal{B}(B^{+}\to D^{*-}{\pi }^{+}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\ell }^{+}{\nu }_{\ell })}=(9.50\pm 0.33\pm 0.34)\%$, $\frac{\mathcal{B}(B^0\to D^{-}{\pi }^{+}{\pi }^{-}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell })}=(2.91\pm 0.37\pm 0.26)\%$, $\frac{\mathcal{B}(B^{+}\to {\overline{D}}^0{\pi }^{+}{\pi }^{-}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\ell }^{+}{\nu }_{\ell })}=(3.10\pm 0.26\pm 0.22)\%$, $\frac{\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell })}=(0.99\pm 0.43\pm 0.20)\%$, $\frac{\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\pi }^{+}{\pi }^{-}{\ell }^{+}{\nu }_{\ell })}{\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\ell }^{+}{\nu }_{\ell })}=(1.25\pm 0.27\pm 0.15)\%$, where the uncertainties are statistical and systematic, respectively. These are the most precise measurements of these branching fraction ratios to date. The invariant mass spectra of the $D\pi$, $D^{*}\pi$, and $D\pi \pi$ systems are studied, and the branching fraction products $\mathcal{B}(B^0\to D_2^{*-}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}(D_2^{*-}\to {\overline{D}}^0{\pi }^{-})=(0.157\pm 0.015\pm 0.005)\%$, $\mathcal{B}(B^{+}\to {\overline{D}}_0^{*0}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}({\overline{D}}_0^{*0}\to D^{-}{\pi }^{+})=(0.054\pm 0.022\pm 0.005)\%$, $\mathcal{B}(B^{+}\to {\overline{D}}_2^{*0}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}({\overline{D}}_2^{*0}\to D^{-}{\pi }^{+})=(0.163\pm 0.011\pm 0.008)\%$, $\mathcal{B}(B^0\to D_1^{-}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}(D_1^{-}\to {\overline{D}}^{*0}{\pi }^{-})=(0.306\pm 0.050\pm 0.029)\%$, $\mathcal{B}(B^0\to D_1^{\prime -}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}(D_1^{\prime -}\to {\overline{D}}^{*0}{\pi }^{-})=(0.206\pm 0.068\pm 0.025)\%$, $\mathcal{B}(B^0\to D_2^{*-}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}(D_2^{*-}\to {\overline{D}}^{*0}{\pi }^{-})=(0.051\pm 0.040\pm 0.010)\%$, $\mathcal{B}(B^{+}\to {\overline{D}}_1^0{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}({\overline{D}}_1^0\to D^{*-}{\pi }^{+})=(0.249\pm 0.023\pm 0.015)\%$, $\mathcal{B}(B^{+}\to {\overline{D}}_1^{\prime 0}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}({\overline{D}}_1^{\prime 0}\to D^{*-}{\pi }^{+})=(0.138\pm 0.036\pm 0.009)\%$, $\mathcal{B}(B^{+}\to {\overline{D}}_2^{*0}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}({\overline{D}}_2^{*0}\to D^{*-}{\pi }^{+})=(0.137\pm 0.026\pm 0.009)\%$, $\mathcal{B}(B^0\to D_1^{-}{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}(D_1^{-}\to D^{-}{\pi }^{+}{\pi }^{-})=(0.102\pm 0.013\pm 0.009)\%$, $\mathcal{B}(B^{+}\to {\overline{D}}_1^0{\ell }^{+}{\nu }_{\ell })\times \mathcal{B}({\overline{D}}_1^0\to {\overline{D}}^0{\pi }^{+}{\pi }^{-})=(0.105\pm 0.011\pm 0.009)\%$, are extracted. This is the first observation of the decays $B\to {\overline{D}}_1{\ell }^{+}{\nu }_{\ell }$ with $D_1\to D{\pi }^{+}{\pi }^{-}$.

Bimetric gravity is a theory of gravity that posits the existence of two interacting and dynamical metric tensors. The spectrum of bimetric gravity consists of a massless and a massive spin-2 particle. The form of the interactions between the two metrics $g_{\mu \nu }$ and $f_{\mu \nu }$ is constrained by requiring absence of the so-called Boulware-Deser ghost. In this work we extend the original bimetric theory to its bimetric-affine counterpart, in which the two connections, associated with the Ricci scalars, are treated as independent variables. We examine in detail the case of an additional quadratic in the Ricci scalar curvature term ${\mathcal{R}}^2(g,\mathrm{\Gamma })$ and we find that this theory is free of ghosts for a wide range of the interaction parameters, not excluding the possibility of a dark matter interpretation of the massive spin-2 particle.

The stochastic spectral expansion method offers a simple framework for calculations in de Sitter spacetimes. We show how to extend its reach to metastable vacuum states, both in the case when the potential is bounded from below, and when it is unbounded from below and therefore no stable vacuum state exists. In both cases, the decay rate of the metastable vacuum is given by the lowest nonzero eigenvalue associated to the Fokker–Planck equation. We show how the corresponding eigenfunction determines the field probability distribution which can be used to compute correlation functions and other observables in the metastable vacuum state.

To understand the oscillatory behavior exhibited in the timelike electromagnetic form factors of nucleons, we propose a toy model based on the Jost function of the $N\overline{N}$ pair into the timelike form factors with the help of the distorted-wave Born approximation. By constructing a simple square-well potential reflecting the final-state interaction of $N\overline{N}$, we naturally represent the damped oscillatory phenomenon in the timelike electromagnetic form factors of nucleons. Especially, our study reveals that the “period” of the oscillation is approximately determined by the Yukawa interaction range $1/m_{\pi }$. Other possible potentials are also discussed. The threshold enhancements of the cross sections for $e^{+}{e}^{-}\to n\overline{n}$, $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$, and ${\mathrm{\Lambda }}_c{\overline{\mathrm{\Lambda }}}_c$ can also be understand within this scenario.

In this paper, we compare the saturation timescales for complexity, linear entropy, and entanglement negativity for two open quantum systems. Our first model is a coupled harmonic oscillator, where we treat one of the oscillators as the bath. The second one is a type of Caldeira-Leggett model, where we consider a one-dimensional free scalar field as the bath. Using these open quantum systems, we discovered that both the complexity of purification and the complexity from operator-state mapping is always saturated for a completely mixed state. More explicitly, the saturation timescale for both types of complexity is smaller than the saturation timescale for linear entropy. On top of this, we found that the saturation timescale for linear entropy and entanglement negativity is of the same order for the Caldeira-Leggett model.

In this work we analyze the sound perturbation of Unruh’s acoustic effective geometry in both ($2+1$) and ($3+1$) spacetime dimensions and present an exact analytical expression for the quasibound states of these idealized black-hole configurations by using a new approach recently developed, which uses the polynomial conditions of the hypergeometric functions. Our main goal is to discuss the effects of having an event horizon in such effective metrics. We also discuss the stability of the systems and present the radial eigenfunctions related to these quasibound state frequencies. These metrics assume just the form it has for a Schwarzschild black hole near the event horizon, and therefore may, in principle, shed some light into the underlying classical and quantum physics of astrophysical black holes through analog acoustic probes.

Using a quasispherical approximation of an affine-null metric adapted to an asymptotic Bondi inertial frame, we present high order approximations of the metric functions in terms of the specific angular momentum for a slowly rotating stationary and axisymmetric vacuum spacetime. The metric is obtained by following the procedure of integrating the hierarchy of Einstein equations in a characteristic formulation utilizing master functions for the perturbations. It further verified its equivalence with the Kerr metric in the slowly rotating approximation by carrying out an explicit transformation between the Boyer-Lindquist coordinates to the employed affine-null coordinates. A peculiar feature of the derivation is that in the solution of the perturbation equations for every order a new integration constant appears which cannot be set to zero using asymptotical flatness or regularity arguments. However, these additional integration constants can be absorbed into the overall Komar mass and Komar angular momentum of a slowly rotating black hole.

In general relativity, nonsingular black holes contain (at least) a Cauchy horizon, a null hypersurface beyond which determinism breaks down. Even though the strong cosmic censorship conjecture establishes the impossibility of extending spacetime beyond this region, in this paper we investigate how far we can go, without invoking this conjecture, in the building of a physically reasonable black hole without a Cauchy hypersurface. Following this reasoning, we find a black hole lacking of Cauchy horizon, asymptotically flat and satisfying either the strong or dominant energy condition. The above is possible by demanding integrable singularity for the Ricci scalar, whose direct consequence is the appearance of finite tidal forces. We show that the spacetime inside the event horizon represents a warped anti–de Sitter spacetime, which might be interpreted in terms of a finite superposition of configurations.

We derive an approximate analytical expression of the maximum mass of relativistic self-gravitating Bose-Einstein condensates with repulsive or attractive $|\phi {|}^4$ self-interaction. This expression interpolates between the general relativistic maximum mass of noninteracting bosons stars, the general relativistic maximum mass of bosons stars with a repulsive self-interaction in the Thomas-Fermi limit, and the Newtonian maximum mass of dilute axion stars with an attractive self-interaction [P. H. Chavanis, Phys. Rev. D 84, 043531 (2011)]. We obtain the general structure of our formula from simple considerations and determine the numerical coefficients in order to recover the exact asymptotic expressions of the maximum mass in particular limits. As a result, our formula should provide a relevant approximation of the maximum mass of relativistic boson stars for any value (positive and negative) of the self-interaction parameter. We discuss the evolution of the system above the maximum mass and consider application of our results to dark matter halos and inflaton clusters. We also make a short review of boson stars and Bose-Einstein condensate dark matter halos and point out analogies with models of extended elementary particles.

The anisotropies of the stochastic gravitational wave background, as produced in the early phases of cosmological evolution, can act as a key probe of the primordial universe particle content. We point out a new universal property of gravitational wave anisotropies of cosmological origin: for adiabatic initial conditions, their angular power spectrum is insensitive to the equation of state of the cosmic fluid driving the expansion before big bang nucleosynthesis. Any deviation from this universal behavior points to the presence of nonadiabatic sources of primordial fluctuations. Such scenarios can be tested by gravitational wave detectors operating at a frequency range which is fully complementary to cosmic microwave background (CMB) experiments. In this work, we prove this general result, and we illustrate its consequences for a representative realization of initial conditions based on the curvaton scenario. In the case of the simplest curvaton setup, we also find a significant cross-correlation between gravitational wave anisotropies and the CMB temperature fluctuations. There is a fourfold enhancement vis-à-vis the purely adiabatic scenario. We discuss the implications of our findings for identifying the origin of the (cosmological) gravitational wave background when, as is often the case, this cannot be determined solely on the basis of its spectral shape.

The matter power spectrum has been strongly constrained by astronomical measurements at large scales, but only weakly at small scales. Compared with the standard scenario, the deviation of the matter power spectrum at small scales has influence on the cosmological structure formation, e.g., the comoving number density of dark matter halos. The thermal history of the intergalactic medium (IGM) can be changed if dark matter is made of weakly interacting massive particles and can annihilate into standard model particles. The changes of the evolution of IGM could leave imprints on the relevant astronomical observations. Taking into account the dark matter annihilation, we investigate the impact of the deviation of matter power spectrum at small scales on the global 21-cm signal. In view of the measurements of the global 21-cm signal by the EDGES experiment, we explore the allowed parameter space of $m_s$, which describes the degree of deviation, by requiring the differential brightness temperature of the global 21-cm signal $\delta T_{21}\le -50\mathrm{mK}$ at redshift $z=17$.

We devise a method to constrain self-interacting dark matter (SIDM) from observations of quadruply imaged quasars, and apply it to five self-interaction potentials with a long-range dark force. We consider several SIDM models with an attractive potential that allows for the formation of quasibound states, giving rise to resonant features in the cross section localized at particular velocities below $50\mathrm{km}{\mathrm{s}}^{-1}$. We propose these resonances, which amplify or suppress the cross section amplitude by over an order of magnitude, accelerate or delay the onset of core collapse in low-mass dark matter halos, and derive constraints on the timescale for core collapse for the five interaction potentials we consider. Our data strongly disfavors scenarios in which a majority of halos core collapse, with the strongest constraints obtained for cross section strengths exceeding $100{\mathrm{cm}}^2{\mathrm{g}}^{-1}$ at relative velocities below $30\mathrm{km}{\mathrm{s}}^{-1}$. This work opens a new avenue to explore the vast landscape of possible SIDM theories.

A stochastic gravitational-wave background (SGWB) is expected to be produced by the superposition of individually undetectable, unresolved gravitational-wave (GW) signals from cosmological and astrophysical sources. Such a signal can be searched with dedicated techniques using the data acquired by a network of ground-based GW detectors. In this work, we consider the astrophysical SGWB resulting from pulsar glitches, which are sudden increases in the rotational pulsar frequency, within our Galaxy. More specifically, we assume glitches to be associated with quantized, superfluid, vortex avalanches in the pulsars, and we model the SGWB from the superposition of GW bursts emitted during the glitching phase. We perform a cross-correlation search for this SGWB-like signal employing the data from the first three observation runs of Advanced LIGO and Virgo. Not having found any evidence for a SGWB signal, we set upper limits on the dimensionless energy density parameter ${\mathrm{\Omega }}_{\mathrm{gw}}(f)$ for two different power-law SGWBs, corresponding to two different glitch regimes. We obtain ${\mathrm{\Omega }}_{\mathrm{gw}}(f)\le 7.5\times {10}^{-10}$ at 25 Hz for a spectral index $5/2$, and ${\mathrm{\Omega }}_{\mathrm{gw}}(f)\le 5.7\times {10}^{-17}$ at 25 Hz for a spectral index $17/2$. We then use these results to set constraints on the average glitch duration and the average radial motion of the vortices during the glitches for the population of the glitching Galactic pulsars, as a function of the Galactic glitch rate.

As a follow up of our work on the electromagnetic four-current, we study for the first time the relativistic polarization and magnetization spatial distributions inside a spin-$\frac{1}{2}$ target within the quantum phase-space approach. While the polarization-magnetization tensor is usually defined in terms of the Gordon decomposition of the electromagnetic four-current, a Breit frame analysis reveals that a physically simpler and more natural picture of the system arises when the polarization-magnetization tensor is instead defined in terms of a Sachs decomposition. Relativistic polarization and magnetization distributions for a moving target are compared with their light-front counterparts. In particular, we show that the genuine light-front magnetization distributions are defined in terms of Fourier transforms of the Sachs magnetic form factor, rather than in terms of the Pauli form factor as suggested earlier in the literature. We finally illustrate our results in the case of a nucleon using the electromagnetic form factors extracted from experimental data.

A vector boson $W_1^{\mu }$ with the quantum numbers $(\mathbf{3},1)$ under $SU{(2)}_L\times U(1{)}_Y$ could in principle couple with the Higgs field via the renormalizable term $W_1^{\mu *}H{D}_{\mu }H$. This interaction is known to affect the $T$ parameter and, in so doing, it could potentially explain the recent CDF measurement of the W-boson mass. As it is often the case with vectors, building a viable model with a $W_1$ gauge boson is nontrivial. In this work I will describe two variations of a minimal setup containing this field; they are based on an extended $SO(5)\times SU(2)\times U(1)$ electroweak group. I will nevertheless show that interactions such as $W_1^{\mu *}H{\partial }_{\mu }H$ are not generated in a Yang-Mills theory. A coupling between $W_1$, $H$ and another Higgs doublet $H^{\prime }$ is possible though. Finally, I will provide an explicit recipe for the construction of viable models with gauge bosons in arbitrary representations of the Standard Model group which may couple to a Standard Model fermion and an exotic one.

We consider the issue of vacuum misalignment induced by four-Fermi couplings in a generic strongly coupled four-dimensional gauge theory. After briefly reviewing the general formalism, we focus on the case of partial compositenesslike operators at leading order, which is relevant in applications to phenomenology. We show that the interactions between an elementary fermion and composite spin-$1/2$ operators in various representations contribute to the effective potential with relative sign differences. Thus the correct sign required to misalign the vacuum is guaranteed to occur for some representations but not all of them. The overall sign dictating the specific representations responsible for misalignment can in principle be determined on the lattice. We also comment on the likely sign for some simple cases.

Non-Abelian gauge fields having a line-singularity of the Dirac type lead us to violation of the non-Abelian Bianchi identity. The violation as an operator is equivalent to violation of Abelian-like Bianchi identities corresponding to eight Abelian-like conserved magnetic monopole currents of the Dirac type in $SU(3)$ QCD. It is very interesting to study if these new Abelian-like monopoles are responsible for color confinement in the continuum $SU(3)$ QCD, since any reliable candidate of color magnetic monopoles is not known yet. If these new Abelian-like monopoles exist in the continuum limit, the Abelian dual Meissner effect occurs, so that the linear part of the static potential between a quark-antiquark pair is reproduced fully by those of Abelian and monopole static potentials. These phenomena are called here as perfect Abelian and monopole dominances. It is shown that the perfect Abelian dominance is reproduced fairly well, whereas the perfect monopole dominance seems to be realized for large $\beta$ when use is made of the smooth lattice configurations in the maximally Abelian (MA) gauge. Making use of a block spin transformation with respect to monopoles, the scaling behaviors of the monopole density and the effective monopole action are studied. Both monopole density and the effective monopole action which are usually a two-point function of $\beta$ and the number of times $n$ of the block spin transformation are a function of $b=na(\beta )$ alone for $n=1$, 2, 3, 4, 6, 8, 12. If the scaling behavior is seen for up to larger $n$, it shows the existence of the continuum limit, since $a(\beta )\to 0$ when $n\to \infty$ for fixed $b=na(\beta )$. Along with the previous results without any gauge fixing, these new results obtained in MA gauge suggest that the new Abelian-like monopoles play the role of color confinement in $SU(3)$ QCD.

We study relativistic fermions in three euclidean dimensions with four- and six-fermion interactions of the Gross-Neveu type. In the limit of many fermion flavors, and besides the isolated free fixed point, the theory displays a line of interacting ultraviolet fixed points. At the endpoint of the critical line, we establish that mass is generated through the spontaneous breaking of quantum scale invariance. Curiously, broken parity symmetry is a prerequisite for the spontaneous generation of mass rather than a consequence thereof. We also calculate critical exponents and find that hyperscaling relations are violated. Further similarities with critical scalar theories, and implications for conformal field theories and higher spin theories are discussed.