It has long been known that no static, spherically symmetric, asymptotically flat Klein-Gordon scalar field configuration surrounding a nonrotating black hole can exist in general relativity. In a series of previous papers, we proved that, at the effective level, this no-hair theorem can be circumvented by relaxing the staticity assumption: for appropriate model parameters, there are quasibound scalar field configurations living on a fixed Schwarzschild background which, although not being strictly static, have a larger lifetime than the age of the universe. This situation arises when the mass of the scalar field distribution is much smaller than the black hole mass, and following the analogies with the hair in the literature we dubbed these long-lived field configurations wigs. Here we extend our previous work to include the gravitational backreaction produced by the scalar wigs. We derive new approximate solutions of the spherically symmetric Einstein-Klein-Gordon system which represent self-gravitating scalar wigs surrounding black holes. These configurations interpolate between boson star configurations and Schwarzschild black holes dressed with the long-lived scalar test field distributions discussed in previous papers. Nonlinear numerical evolutions of initial data sets extracted from our approximate solutions support the validity of our approach. Arbitrarily large lifetimes are still possible, although for the parameter space that we analyze in this paper they seem to decay faster than the quasibound states. Finally, we speculate about the possibility that these configurations could describe the innermost regions of dark matter halos.

We investigate some important physical aspects of a recently presented interior solution for the Kerr metric. It is shown that, as in the spherically symmetric case, there is a specific limit for the maximal value of the surface potential (degree of compactness), beyond which unacceptable physical anomalies appear. Such a bound is related to the appearance of negative (repulsive) gravitational acceleration that is accompanied by the appearance of negative values of the pressure. A detailed discussion on this effect is presented. We also study the possibility of a fragmentation scenario, assuming that the source leaves the equilibrium, and we bring out the differences with the spherically symmetric case.

In this paper we explain how four-dimensional general relativity and, in particular, the Einstein equation, emerge from the spin-foam amplitude in loop quantum gravity. We propose a new limit that couples both the semiclassical limit and continuum limit of spin-foam amplitudes. The continuum Einstein equation emerges in this limit. Solutions of the Einstein equation can be approached by dominant configurations in spin-foam amplitudes. A running scale is naturally associated to the sequence of refined triangulations. The continuum limit corresponds to the infrared limit of the running scale. An important ingredient in the derivation is a regularization for the sum over spins, which is necessary for the semiclassical continuum limit. We also explain in this paper the role played by the so-called flatness in spin-foam formulation, and how to take advantage of it.

We investigate inflationary correlation functions in single-field inflation models. We adopt a BRST formalism where locality and covariance at the subhorizon scale are manifest. The scalar and tensor perturbations are identified with those in the comoving gauge which become constant outside the cosmological horizon. Our construction reproduces the identical non-Gaussianity with the standard comoving gauge. The accumulation of almost scale-invariant fluctuations could give rise to IR logarithmic corrections at the loop level. We investigate the influence of this effect on the subhorizon dynamics. Since such an effect must respect covariance, our BRST gauge has an advantage over the standard comoving gauge. We estimate IR logarithmic effects to the slow-roll parameters at the one-loop level. We show that $\epsilon$ receives IR logarithmic corrections, while this is not the case for $\eta$. We point out that IR logarithmic effects provide the shift-symmetry-breaking mechanism. This scenario may lead to an inflation model with a linear potential.

We study the ultralight axion dark matter with mass around ${10}^{-22}\mathrm{eV}$ in $f(R)$ gravity which might resolve the dark energy problem. In particular, we focus on the fact that the pressure of the axion field oscillating in time produces oscillations of gravitational potentials. We show that the oscillation of the gravitational potential is sensitive to the model of gravity. Remarkably, we find that the detectability of the oscillation through the gravitational wave detectors can be significantly enhanced due to the nonlinear resonance between the ultralight axion and the scalaron.

There are at least two formation scenarios consistent with the first gravitational-wave observations of binary black hole mergers. In field models, black hole binaries are formed from stellar binaries that may undergo common envelope evolution. In dynamic models, black hole binaries are formed through capture events in globular clusters. Both classes of models are subject to significant theoretical uncertainties. Nonetheless, the conventional wisdom holds that the distribution of spin orientations of dynamically merging black holes is nearly isotropic while field-model black holes prefer to spin in alignment with the orbital angular momentum. We present a framework in which observations of black hole mergers can be used to measure ensemble properties of black hole spin such as the typical black hole spin misalignment. We show how to obtain constraints on population hyperparameters using minimal assumptions so that the results are not strongly dependent on the uncertain physics of formation models. These data-driven constraints will facilitate tests of theoretical models and help determine the formation history of binary black holes using information encoded in their observed spins. We demonstrate that the ensemble properties of binary detections can be used to search for and characterize the properties of two distinct populations of black hole mergers.

Many dark matter interaction types lead to annihilation processes which suffer from $p$-wave suppression or helicity suppression, rendering them subdominant to unsuppressed $s$-wave processes. We demonstrate that the natural inclusion of dark initial state radiation can open an unsuppressed $s$-wave annihilation channel and, thus, provide the dominant dark matter annihilation process for particular interaction types. We illustrate this effect with the bremsstrahlung of a dark spin-0 or dark spin-1 particle from fermionic dark matter, $\overline{\chi }\chi \to \overline{f}f\varphi$ or $\overline{f}f{Z}^{\prime }$. The dark initial state radiation process, despite having a 3-body final state, proceeds at the same order in the new physics scale $\mathrm{\Lambda }$ as the annihilation to the 2-body final state $\overline{\chi }\chi \to \overline{f}f$. This opens an unsuppressed $s$ wave at lower order in $\mathrm{\Lambda }$ than the well-studied lifting of helicity suppression via Standard Model final state radiation or virtual internal bremsstrahlung. This dark bremsstrahlung process should influence LHC and indirect detection searches for dark matter.

We study charmonium and bottomonium as relativistic bound states in a light-front quantized Hamiltonian formalism. The effective Hamiltonian is based on light-front holography. We use a recently proposed longitudinal confinement to complete the soft-wall holographic potential for the heavy flavors. The spin structure is generated from the one-gluon exchange interaction with a running coupling. The adoption of asymptotic freedom improves the spectroscopy compared with previous light-front results. Within this model, we compute the mass spectroscopy, decay constants and the r.m.s. radii. We also present a detailed study of the obtained light-front wave functions and use the wave functions to compute the light-cone distributions, specifically the distribution amplitudes and parton distribution functions. Overall, our model provides a reasonable description of the heavy quarkonia.

We calculate the T-matrices of pseudoscalar meson octet-baryon scattering to one-loop order in SU(3) heavy baryon chiral perturbation theory. The pertinent combinations of low-energy constants are determined by fitting to phase shifts of $\pi N$ and $KN$ scattering and the corresponding data. By using these low-energy constants, we obtain the strong phase shift difference of $\pi \mathrm{\Lambda }$ scattering at the $\mathrm{\Xi }$ mass, ${\delta }_P-{\delta }_S=(8.8\pm 0.2)$ degrees, in agreement with experimental results. We find that the phase shifts in the $S_{01}(\pi \mathrm{\Sigma })$, $S_{01}(K\mathrm{\Xi })$, $S_{01}(\overline{K}N)$, and $S_{11}(\overline{K}\mathrm{\Sigma })$ waves are so strong that resonances may be generated dynamically in all these channels. We also predict the scattering lengths and make comparisons with the results obtained from the threshold T-matrices in heavy baryon chiral perturbation theory and the method of covariant infrared regularization. The issue of convergence is also discussed in detail.

At present, there are several measurements of $B$ decays that exhibit discrepancies with the predictions of the SM, and suggest the presence of new physics (NP) in $b\to s{\mu }^{+}{\mu }^{-}$ transitions. Many NP models have been proposed as explanations. These involve the tree-level exchange of a leptoquark (LQ) or a flavor-changing $Z^{\prime }$ boson. In this paper we examine whether it is possible to distinguish the various models via $CP$-violating effects in $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$. Using fits to the data, we find the following results. Of all possible LQ models, only three can explain the data, and these are all equivalent as far as $b\to s{\mu }^{+}{\mu }^{-}$ processes are concerned. In this single LQ model, the weak phase of the coupling can be large, leading to some sizable $CP$ asymmetries in $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$. There is a spectrum of $Z^{\prime }$ models; the key parameter is $g_L^{\mu \mu }$, which describes the strength of the $Z^{\prime }$ coupling to ${\mu }^{+}{\mu }^{-}$. If $g_L^{\mu \mu }$ is small (large), the constraints from $B_s^0-{\overline{B}}_s^0$ mixing are stringent (weak), leading to a small (large) value of the NP weak phase, and corresponding small (large) $CP$ asymmetries. We therefore find that the measurement of $CP$-violating asymmetries in $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$ can indeed distinguish among NP $b\to s{\mu }^{+}{\mu }^{-}$ models.

If one removes any ad hoc symmetry assumptions, the general two-Higgs-doublet model should have additional Yukawa interactions independent from fermion mass generation, in general involving flavor-changing neutral Higgs couplings. These extra couplings can affect the discovered Higgs boson $h$ through fermion loop contributions. We calculate the renormalized $hZZ$ coupling at the one-loop level and evaluate the dependence on heavy Higgs boson mass and extra Yukawa coupling ${\rho }_{tt}$. Precision measurements at future colliders can explore the parameter space, and can give stronger bounds on ${\rho }_{tt}$ than the current bound from flavor experiments. As a side result, we find that if ${\rho }_{tt}\cos \gamma <0$, where $\cos \gamma$ is the exotic Higgs component of $h$, the ${\rho }_{tt}$-induced top loop contribution cancels against bosonic loop contributions, and one may have alignment without decoupling, namely $\sin (-\gamma )\simeq 1$, but exotic scalar bosons could have masses of several hundred GeV.

In this paper, we consider the Standard Model (SM) with one family of vectorlike (VL) leptons, which couple to all three families of the SM leptons. We study the constraints on this model coming from the heavy-charged lepton mass bound, electroweak precision data, the muon anomalous magnetic moment, lepton flavor violation, Higgs boson decay constraints, and a recently measured lepton nonuniversality observable, $R_{K^{*0}}$, along with $R_K$. We find that the strongest constraints are coming from the muon $g-2$, $R_{\mu \mu }=\mathrm{\Gamma }(h\to \mu \mu )/\mathrm{\Gamma }(h\to \mu \mu {)}_{\mathrm{SM}}$, $R_{\gamma \gamma }$ and $\mathrm{BR}(\mu \to e\gamma )$. Although VL leptons couple to all three families of the SM leptons, the ratio of electron-VL to muon-VL coupling is constrained to be $⟨{\lambda }_e/{\lambda }_{\mu }⟩\lesssim {10}^{-4}$. We also find that this model cannot fit the lepton nonuniversality discrepancies.

We compute in the density-matrix formalism the baryon asymmetry generated by the decay of the Higgs doublet into a right-handed (RH) neutrino and a Standard Model lepton. The emphasis is put on the baryon asymmetry produced by the total lepton-number violating decay. From the derivation of the corresponding evolution equations, and from their integration, we find that this contribution is fully relevant for large parts of the parameter space. This confirms the results found recently in the $CP$-violating decay formalism with thermal corrections and shows in particular that the lepton-number violating processes are important not only for high-scale leptogenesis but also when the RH-neutrino masses are in the GeV range. For large values of the Yukawa couplings, we also find that the strong washout is generically much milder for this total lepton-number violating part than for the usual RH-neutrino oscillation flavor part.

We study two models of scalar dark matter from “large” electroweak multiplets with isospin $5/2$ ($n=6$ members) and $7/2$ ($n=8$), whose scalar potentials preserve a $Z_2$ symmetry. Because of large annihilation cross sections due to electroweak interactions, these scalars can constitute all the dark matter only for masses in the multi-TeV range. For such high masses, Sommerfeld enhancement and coannihilations play important roles in the dark matter relic abundance calculation, reducing the upper bound on the large multiplet’s mass by almost a factor of 2. We determine the allowed parameter ranges including both of these effects and show that these models are as yet unconstrained by dark matter direct detection experiments, but will be probed by currently running and proposed future experiments. We also show that a Landau pole appears in these models at energy scales below $10^9\mathrm{GeV}$, indicating the presence of additional new physics below that scale.

We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polyakov-loop extended quark-meson Lagrangian that includes the coupling of quarks to vector meson and temporal gauge fields. The functional renormalization group is employed to properly account for the $O(4)$ criticality at the phase boundary. We focus on the properties and systematics of ratios of the net-baryon-number cumulants ${\chi }_B^n$, for $1\le n\le 6$, near the phase boundary. The results are presented in the context of the recent experimental data of the STAR Collaboration on fluctuations of the net proton number in heavy-ion collisions at RHIC. We show that the model results for the energy dependence of the cumulant ratios are in good overall agreement with the data, with one exception. At center-of-mass energies below 19.6 GeV, we find that the measured fourth-order cumulant deviates considerably from the model results, which incorporate the expected $O(4)$ and $Z(2)$ criticality. We assess the influence of model assumptions and in particular of repulsive vector-interactions, which are used to modify the location of the critical end point in the model, on the cumulants ratios. Finally, we discuss a possibility to test to what extent the fluctuations are affected by nonequilibrium dynamics by comparing certain ratios of cumulants.

Leading twist light cone distribution amplitudes (LCDAs) are key ingredients in calculating various hadronic amplitudes using light cone QCD sum rules. This work concentrates on calculating the leading twist LCDAs of $p$-wave heavy quarkonia. Quark model wave functions for the ground, first, and second excited states of $p$-wave charmonia and bottomonia have been calculated and are used for calculating the relevant LCDAs and leptonic decay constants.

We evaluate both chirally even and odd generalized parton distributions (GPDs) in the leading twist in a recently proposed quark-diquark model for the proton where the light front wave functions are constructed from the soft-wall AdS/QCD prediction. The GPDs in transverse impact parameter space give the spin densities for different quark and proton polarizations. For longitudinally polarized proton only chiral even GPDs contribute but for transversely polarized proton both chiral even and chiral odd GPDs contribute to the spin densities. We present a detail study of the spin densities in this model.

The ArgoNeuT Collaboration reports the first measurement of neutral current ${\pi }^0$ production in ${\nu }_{\mu }$-argon and ${\overline{\nu }}_{\mu }$-argon scattering. This measurement was performed using the ArgoNeuT liquid argon time projection chamber deployed at Fermilab’s NuMI neutrino beam with an exposure corresponding to $1.2\times 10^{20}$ protons-on-target from the Fermilab main injector and a mean energy for ${\nu }_{\mu }$ of 9.6 GeV and for ${\overline{\nu }}_{\mu }$ of 3.6 GeV. We compare the measured cross section and kinematic distributions to predictions from the GENIE and NuWro neutrino interaction event generators.

Based on a sample of 1.31 billion $J/\psi$ events collected with the BESIII detector, we report the study of the doubly radiative decay ${\eta }^{\prime }\to \gamma \gamma {\pi }^0$ for the first time, where the ${\eta }^{\prime }$ meson is produced via the $J/\psi \to \gamma {\eta }^{\prime }$ decay. The branching fraction of ${\eta }^{\prime }\to \gamma \gamma {\pi }^0$ inclusive decay is measured to be $\mathcal{B}({\eta }^{\prime }\to \gamma \gamma {\pi }^0{)}_{\mathrm{Incl}}=(3.20\pm 0.07(\mathrm{stat})\pm 0.23(\mathrm{sys}))\times {10}^{-3}$, while the branching fractions of the dominant process ${\eta }^{\prime }\to \gamma \omega$ and the nonresonant component are determined to be $\mathcal{B}({\eta }^{\prime }\to \gamma \omega )\times \mathcal{B}(\omega \to \gamma {\pi }^0)=(23.7\pm 1.4(\mathrm{stat})\pm 1.8(\mathrm{sys}))\times {10}^{-4}$ and $\mathcal{B}({\eta }^{\prime }\to \gamma \gamma {\pi }^0{)}_{\mathrm{NR}}=(6.16\pm 0.64(\mathrm{stat})\pm 0.67(\mathrm{sys}))\times {10}^{-4}$, respectively. In addition, the $M_{\gamma \gamma }^2$-dependent partial widths of the inclusive decay are also presented.

We study Kähler moduli stabilizations in semirealistic magnetized D-brane models based on $Z_2\times Z_2^{\prime }$ toroidal orbifolds. In type IIB compactifications, 3-form fluxes can stabilize the dilaton and complex structure moduli fields, but there remain some massless closed string moduli fields, Kähler moduli. The magnetic fluxes generate Fayet-Iliopoulos terms, which can fix ratios of Kähler moduli. On top of that, we consider D-brane instanton effects to stabilize them in concrete D-brane models and investigate the brane configurations to confirm that the moduli fields can be stabilized successfully. In this paper, we treat two types of D-brane models. One is based on D9-brane systems respecting the Pati-Salam model. The other is realized in a D7-brane system breaking the Pati-Salam gauge group. We find suitable configurations where the D-brane instantons can stabilize the moduli fields within both types of D-brane models, explaining an origin of a small constant term of the superpotential, which is a key ingredient for successful moduli stabilizations.