The fermionic $Z$-portal dark matter model suffers from severe constraints from direct detection experiments. However, a narrow parameter space around the $Z$-funnel region is beyond the present reach due to the resonance annihilation. In this paper, we provide an intriguing collider prospect for probing the $Z$-funnel dark matter mass range at the future lepton colliders including the beam polarization feature. We have done a comprehensive analysis for monophoton signal at the colliders for such a dark matter. A realistic estimation for the 90% C.L. constraints with the systematic beam uncertainties has also been provided.

We revisit the ${\mathrm{U}(1)}_A$ anomaly in the holographic model of low-energy QCD by Witten, Sakai, and Sugimoto, presenting a new and direct derivation of the Witten-Veneziano mechanism for generating the mass of the ${\eta }^{\prime }$ through an anomalous mixing of the Ramond-Ramond $C_1$ field with the singlet component of the pseudoscalar mesons. The latter turns out to have a kinetic mixing with the normalizable modes of the $C_1$ field representing pseudoscalar glueballs, yielding additional vertices for their production and their decay that dominate over those of the unmixed case considered previously in the Witten-Sakai-Sugimoto model. The leading channel is predicted to be a decay into two vector mesons, followed in importance by decay into three pseudoscalar mesons. The issue of production of pseudoscalar glueballs in radiative $J/\psi$ decays and in double diffractive processes is also discussed briefly.

We study the $J/\psi \to \gamma {\pi }^{+}{\pi }^{-}$, $\gamma {\pi }^0\eta$ reactions from the perspective that they come from the $J/\psi \to \varphi (\omega ){\pi }^{+}{\pi }^{-},{\rho }^0{\pi }^0\eta$ reactions, where the ${\rho }^0$, $\omega$, and $\varphi$ get converted into a photon via vector meson dominance. Using models successfully used previously to study the $J/\psi \to \omega (\varphi )\pi \pi$ reactions, we make determinations of the invariant mass distributions for ${\pi }^{+}{\pi }^{-}$ in the regions of the $f_0(500)$, $f_0(980)$, and for ${\pi }^0\eta$ in the region of the $a_0(980)$. The integrated differential widths lead to branching ratios below present upper bounds, but they are sufficiently large for future check in updated facilities.

In this article, we reflect on a problem of a black hole entropy. The main point of the article is that the black hole horizon should be treated as a boundary as well as the boundary at infinity. To make things more concrete, we apply the general ideas to the extremal Oliva-Tempo-Troncoso black hole and construct the corresponding Hilbert space using near-horizon hair. After creating the state space by using the proposed construction, we identify the natural candidates for the microstates responsible for the black hole entropy. The correct value of the black hole entropy is reproduced by counting the number of distinct microstates and applying the Boltzmann formula.

In this work, based on the constant for the equation of state $\omega$, we obtain the Schwarzschild-like black hole solutions in some dark matter halos. We also generalize these black hole metrics to Kerr-like black hole solutions with Newman-Janis algorithm. For an example, we derive the specific black hole space-time metrics in the case of the cold dark matter halo and Bose-Einstein condensation dark matter halo. Following the above two black hole metrics, we discuss how a dark matter halo changes the properties of black holes, including the event horizon structure (these results agree with that obtained by Liu and Zhang [Phys. Lett. B 679, 88 (2009).] in the case of gravitational collapse), stationary limit surfaces, ergosphere, and singularity structure. Our results may help us understand the interaction between the dark matter halo and supermassive black holes at the centers of galaxies.

We study the production of gravitational waves from primordial scalar perturbations in double-inflection-point inflation, in which one of the inflection points leads to a primordial power spectrum consistent with CMB observations at large scales and the other generates a large peak in the power spectrum of scalar perturbations at small scales. We calculate the energy spectrum of the reduced gravitational waves and find that the gravitational-wave signal can be detected by future space-based laser interferometers.

In the type II seesaw mechanism, the neutrino mass generation could be tested experimentally if the Higgs triplet is at the TeV scale and has a small cubic coupling to the standard model Higgs doublet. We show such small triplet-doublet coupling and the cosmic baryon asymmetry can be simultaneously induced by an additional seesaw mechanism involving a $U(1{)}_{B-L}$ gauge symmetry. Meanwhile, three right-handed neutrinos for canceling the gauge anomalies can form a stable Dirac fermionic dark matter besides an acceptably massless fermion.

In this paper, I propose a strategy to measure vector-boson scattering (VBS) at the LHCb experiment. The typical VBS topology at hadron colliders features two energetic back-to-back jets with large rapidities and two gauge bosons produced centrally. In this article, I show that such a topology can actually be probed by the LHCb detector. In particular, tagging only one of the two jets in combination with two same-sign leptons allows for a measurement with upcoming luminosities. I present an illustrative event selection where cross sections and differential distributions are computed for VBS and its irreducible background.

We examine the five-region holographic entropy cone inequalities for the special case of the ${\mathrm{AdS}}_3$-Vaidya metric for a variety of boundary configurations. This is done by numerically solving the geodesic equation in the bulk for various boundary configurations. In all the cases we examine, we find that all the inequalities are satisfied when the bulk satisfies the null energy condition, while the inequalities are all violated when the bulk spacetime violates the null energy condition. A proof of the five-region holographic entropy cone inequalities for the dynamical bulk case remains an open problem—our results provide evidence that these inequalities hold for dynamical bulk spacetimes.

The random matrix theory (RMT) can be used to classify both topological phases of matter and quantum chaos. We develop a systematic and transformative RMT to classify the quantum chaos in the colored Sachdev-Ye-Kitaev (SYK) model first introduced by Gross and Rosenhaus. Here we focus on the two-colored case and the four-colored case with a balanced number of Majorana fermions $N$. By identifying the maximal symmetries, the independent parity conservation sectors, the minimum (irreducible) Hilbert space, and especially the relevant antiunitary and unitary operators, we show that the color degrees of freedom lead to novel quantum chaotic behaviors. When $N$ is odd, different symmetry operators need to be constructed to make the classifications complete. The two-colored case only shows the threefold Wigner-Dyson way, and the four-colored case shows the tenfold generalized Wigner-Dyson way which may also have nontrivial edge exponents. We also study two- and four-colored hybrid SYK models, which display many salient quantum chaotic features hidden in the corresponding pure SYK models. These features motivate us to develop a systematic RMT to study the energy level statistics of two or four uncorrelated random matrix ensembles. The exact diagonalizations are performed to study both the bulk energy level statistics and the edge exponents and to find excellent agreement with our exact maximal symmetry classifications. Our complete and systematic methods can be easily extended to study the generic imbalanced cases. They may be transferred to the classifications of colored tensor models, quantum chromodynamics with pairings across different colors, quantum black holes, and interacting symmetry protected (or enriched) topological phases.

The center of mass (c.m.) and spin for isolated sources of gravitational radiation that move at relativistic speeds are defined. As a first step we also present these definitions in flat space. This contradicts some general wisdom given in textbooks claiming that such definitions are not covariant and thus, have no physical meaning. We then generalize the definitions to asymptotically flat spacetimes giving their equations of motion when gravitational radiation is emitted by the isolated sources. The resulting construction has some similarities with the Mathisson-Papapetrou equations which describe the motion of the particle in an external field. We analyze the relationship between the c.m. velocity and the Bondi linear momentum and show they are not proportional to each other. A similar situation happens between the total and intrinsic angular momentum when the Bondi momentum vanishes. We claim that extra terms should be added in other approaches to adequately describe the time evolution of isolated sources of gravitational radiation.

We study static, spherically symmetric vacuum solutions to quadratic gravity, extending considerably our previous rapid communication [Phys. Rev. D 98, 021502(R) (2018)] on this topic. Using a conformal-to-Kundt metric ansatz, we arrive at a much simpler form of the field equations in comparison with their expression in the standard spherically symmetric coordinates. We present details of the derivation of this compact form of two ordinary differential field equations for two metric functions. Next, we apply analytical methods and express their solutions as infinite power series expansions. We systematically derive all possible cases admitted by such an ansatz, arriving at six main classes of solutions, and provide recurrent formulas for all the series coefficients. These results allow us to identify the classes containing the Schwarzschild black hole as a special case. It turns out that one class contains only the Schwarzschild black hole, three classes admit the Schwarzschild solution as a special subcase, and two classes are not compatible with the Schwarzschild solution at all since they have strictly nonzero Bach tensor. In our analysis, we naturally focus on the classes containing the Schwarzschild spacetime, in particular on a new family of the Schwarzschild-Bach black holes which possesses one additional non-Schwarzschild parameter corresponding to the value of the Bach tensor invariant on the horizon. We study its geometrical and physical properties, such as basic thermodynamical quantities and tidal effects on free test particles induced by the presence of the Bach tensor. We also compare our results with previous findings in the literature obtained using the standard spherically symmetric coordinates.

We study relativistic stars in Hordenski theories that evade the gravitational wave constraints and exhibit the Vainshtein mechanism, focusing on a model based on the cubic Galileon Lagrangian. We derive the scalar field profile for static spherically symmetric objects in asymptotically de Sitter space-time with a linear time dependence. The exterior solution matches the black hole solution found in the literature. Due to the Vainshtein mechanism, the stellar structure is indistinguishable from that of General Relativity with the same central density as long as the radius of the star is shorter than the Vainshtein radius. On the other hand, the scalar field is not suppressed beyond the Vainshtein radius. These solutions have an additional integration constant in addition to the mass of the star.

We investigate infrared dynamics of four-dimensional Einstein gravity in de Sitter space. We set up a general framework to investigate dynamical scaling relations in quantum/classical gravitational theories. The conformal mode dependence of Einstein gravity is renormalized to the extent that general covariance is not manifest. We point out that the introduction of an inflaton is necessary as a counterterm. We observe and postulate a duality between quantum effects in Einstein gravity and classical evolutions in an inflation (or quintessence) model. The effective action of Einstein gravity can be constructed as an inflation model with manifest general covariance. We show that $g=G_N{H}^2/\pi$: the only dimensionless coupling of the Hubble parameter $H^2$ and the Newton’s coupling $G_N$ in Einstein gravity is screened by the infrared fluctuations of the conformal mode. We evaluate the one-loop $\beta$ function of $g$ with respect to the cosmic time $\log Ht$ as $\beta (g)=-(1/2)g^2$, i.e., $g$ is asymptotically free toward the future. The exact $\beta$ function with the backreaction of $g$ reveals the existence of the ultraviolet fixed point. It indicates that the de Sitter expansion stared at the Planck scale with a minimal entropy $S=2$. We have identified the de Sitter entropy $1/g$ with the von Neumann entropy of the conformal zero mode. The former evolves according to the screening of $g$ and the Gibbons-Hawking formula. The latter is found to increase by diffusion in the stochastic process at the horizon in a consistent way. Our Universe is located very close to the fixed point $g=0$ with a large entropy. We discuss possible physical implications of our results such as logarithmic decay of dark energy.

WIMPs are promising dark matter candidates. A WIMP occasionally collides with a mirror equipped with interferometric gravitational wave detectors such as LIGO, Virgo, KAGRA and the Einstein Telescope (ET). When WIMPs collide with a mirror of an interferometer, we expect that characteristic motions of the pendulum and mirror are excited, and those signals could be extracted by highly sophisticated sensors developed for gravitational wave detection. We analyze the motions of the pendulum and mirror, and estimate the detectability of these motions. For the “Thin-ET” detector, the signal-to-noise ratio may be $1.7(\frac{m_{\mathrm{DM}}}{100\mathrm{GeV}})$, where $m_{\mathrm{DM}}$ is the mass of a WIMP. We may set a more strict upper limit on the cross section between a WIMP and a nucleon than the limits obtained by other experiments so far when $m_{\mathrm{DM}}$ is approximately lower than 0.2 GeV. We find an order-of-magnitude improvement in the upper limit around $m_{\mathrm{DM}}=0.2\mathrm{GeV}$.

The momentum spectrum and the number density of created electron-positron pairs in a frequency modulated laser field are investigated using the quantum kinetic equation. It is found that the momentum spectrum presents an obvious interference pattern. This is an imprint of the frequency modulated field on the momentum spectrum, because the momentum peaks correspond to the pair production process by absorbing different frequency component photons. Moreover, the interference effect can also be understood qualitatively by analyzing turning-point structures. The study of the pair number density shows that the number density is very sensitive to modulation parameters and can be enhanced by 2 or 3 orders of magnitude for certain modulation parameters, which may provide a new way to increase the number of created electron-positron pairs in future experiments.

Proton decay, and the decay of nucleons in general, constitutes one of the most sensitive probes of high-scale physics beyond the Standard Model. Most of the existing nucleon decay searches have focused primarily on two-body decay channels, motivated by grand unified theories and supersymmetry. However, many higher-dimensional operators violating baryon number by one unit, $\mathrm{\Delta }B=1$, induce multibody nucleon decay channels, which have been only weakly constrained thus far. While direct searches for all such possible channels are desirable, they are highly impractical. In light of this, we argue that inclusive nucleon decay searches, $N\to X+\mathrm{anything}$ (where $X$ is a light Standard Model particle with an unknown energy distribution), are particularly valuable, as are model-independent and invisible nucleon decay searches such as $n\to \mathrm{invisible}$. We comment on complementarity and opportunities for such searches in the current as well as upcoming large-scale experiments Super-Kamiokande, Hyper-Kamiokande, JUNO, and DUNE. Similar arguments apply to $\mathrm{\Delta }B>1$ processes, which kinematically allow for even more involved final states and are essentially unexplored experimentally.

We report on the computation of the connected light-quark vacuum polarization with $2+1+1$ flavors of highly improved staggered quarks [Follana et al., Phys. Rev. D 75, 054502 (2007).] fermions at the physical point and its contribution to the muon anomalous magnetic moment. Three ensembles, generated by the MILC collaboration, are used to take the continuum limit. The finite-volume correction to this result is computed in the (Euclidean) time-momentum representation to next-to-next-to-leading order (NNLO) in chiral perturbation theory. We find $a_{\mu }^{ll}(\mathrm{HVP})=(659\pm 20\pm 5\pm 5\pm 4)\times {10}^{-10}$, where the errors are statistical and estimates of residual uncertainties from taking the continuum limit, scale setting, and truncation of chiral perturbation theory at NNLO. We compare our results with recent ones in the literature.

Recent studies reveal that at high energies, collisions of a small system such as $p+p$ gives signatures similar to that widely observed in heavy ion collisions hinting toward the possibility of forming a medium with collective behavior. With this motivation, we have used the Glauber model, which is traditionally applied to heavy ion collisions, in a small system using the anisotropic and inhomogeneous density profile of a proton and found that the proposed model reproduces the charged particle multiplicity distribution of $p+p$ collisions at LHC energies very well. Collision geometric properties such as the mean impact parameter, the mean number of binary collisions ($⟨N_{\mathrm{coll}}⟩$), and the mean number of participants ($⟨N_{\mathrm{part}}⟩$) at different multiplicities are determined. Having estimated $⟨N_{\mathrm{coll}}⟩$, we have calculated the nuclear modificationlike factor ($R_{\mathrm{HL}}$) in $p+p$ collisions. We also estimated eccentricity and elliptic flow as a function of charged particle multiplicity using the linear response to the initial geometry.

In the present work, we investigate the production of $P$-wave charmed or charmed-strange mesons in the pion or kaon induced reactions on a proton target. The total cross sections as well as the differential cross sections depending on the scattering angle are evaluated in an effective Lagrangian approach. Our estimations indicate that magnitude of the cross sections strongly depends on the model parameter but such dependence can be almost completely canceled for the cross section ratios. These model independent ratios can be taken as a good criterion of the validity of heavy quark limit in the charmed region, which is helpful to understand $P$ wave charmed and charmed-strange mesons.