New physics in the lepton sector may account for neutrino masses, affect electroweak precision observables, induce charged-lepton flavor violation, and shift dipole moments. The low-energy predictions of different models are most conveniently compared within the formalism of effective field theory. To illustrate the benefits of this approach, we derive the Wilson coefficients for a set of representative models: the fermionic seesaw mechanisms (types I and III), the Zee model, and a minimal leptoquark model. In each case, the Weinberg and the dipole operators have qualitatively different origins. In parallel, we present the model-independent constraints on the Wilson coefficients coming from various lepton observables. We then show that it becomes straightforward to understand the allowed parameter space for each model, and to discriminate between them. The Zee and leptoquark models are suitable to address the muon $g-2$ anomaly.

We study the scenarios where a strongly first-order electroweak phase transition (EWPT) is triggered by a light singlet scalar, which has feeble interactions to the Higgs. Since the singlet scalar is light and has weak couplings, it can decay at a macroscopic distance away from the collision point. Therefore, it can be regarded as a long-lived particle (LLP) in such scenarios. We perform the searches of the LLPs from the exotic Higgs decays, at the FASER, MAPP and CMS-timing detectors of the 14 TeV HL-LHC, to probe the strongly first-order EWPT. In certain scenarios, we show that the LLP searches can help to reach the parameter space of the strongly first-order EWPT remarkably, where the searches for promptly exotic Higgs decays are not valid.

The inert Higgs-doublet model provides a simple framework to accommodate a viable Higgs portal scalar dark matter candidate, together with other heavier scalars of mass 100 GeV or more. We study the effect of next-to-leading order (NLO) QCD corrections in this scenario in the context of the Large Hadron Collider. $\mathcal{O}({\alpha }_s)$ corrections to the gluon-gluon-Higgs effective coupling have been taken into account in this study wherever appropriate. We find such corrections have a significant impact on various kinematic distributions and reduce scale uncertainties substantially. Fixed order NLO results are matched to the pythia8 parton shower (PS) and the di-fatjet signal associated with the missing transverse momentum is analyzed, as this channel has the ability to explore its entire parameter space during the next phase of the LHC run. A closer look at the $\mathrm{NLO}+\mathrm{PS}$ computation indicates a sizable NLO effect together with a subdued contribution from associated production of the heavy scalar compared to the pair production, thereby leading to a refined analysis strategy during the multivariate analysis of this signal.

We extract pion parton distribution functions (PDFs) in a Monte Carlo global QCD analysis of experimental data together with reduced Ioffe time pseudo-distributions and matrix elements of current-current correlators generated from lattice QCD. By including both experimental and lattice QCD data, our analysis rigorously quantifies both the uncertainties of the pion PDFs and systematic effects intrinsic to the lattice QCD observables. The reduced Ioffe time pseudo-distributions significantly decrease the uncertainties on the PDFs, while the current-current correlators are limited by the systematic effects associated with the lattice. Consistent with recent phenomenological determinations, the behavior of the valence quark distribution of the pion at large momentum fraction is found to be $\sim (1-x{)}^{{\beta }_{\mathrm{eff}}}$ with ${\beta }_{\mathrm{eff}}\approx 1.0–1.2$.

We have derived the analytic solutions of dissipative relativistic spin hydrodynamics with Gubser expansion. Following the standard strategy of deriving the solutions in a Gubser flow, we take the Weyl rescaling and obtain the energy-momentum and angular momentum conservation equations in the $d{S}_3\times \mathbb{R}$ space-time. We then derive the analytic solutions of spin density, spin potential and other thermodynamic in $d{S}_3\times \mathbb{R}$ space-time and transform them back into Minkowski space-time ${\mathbb{R}}^{3,1}$. In the Minkowski space-time, the spin density and spin potential including the information of radial expansion decay as $\sim L^{-2}{\tau }^{-1}$ and $\sim L^{-2}{\tau }^{-1/3}$ in large $L$ limit, with $\tau$ being proper time and $L$ being the characteristic length of the system, respectively. Moreover, we observe the nonvanishing spin corrections to the energy density and other dissipative terms in the Belinfante form of dissipative spin hydrodynamics. Our results can also be used as test beds for future simulations of relativistic dissipative spin hydrodynamics.

We explore the ability of a recently proposed jet substructure technique, dynamical grooming, to pin down the properties of the quark-gluon plasma formed in ultrarelativistic heavy-ion collisions. In particular, we compute, both analytically and via Monte Carlo simulations, the opening angle ${\theta }_g$ of the hardest splitting in the jet as defined by dynamical grooming. Our calculation, grounded in perturbative QCD (pQCD), accounts for the factorization in time between vacuum-like and medium-induced processes in the double logarithmic approximation. We observe that the dominant scale in the ${\theta }_g$ distribution is the decoherence angle ${\theta }_c$ which characterizes the resolution power of the medium to propagating color probes. This feature also persists in strong coupling models for jet quenching. We further propose for potential experimental measurements a suitable combination of the dynamical grooming condition and the jet radius that leads to a pQCD-dominated observable with a very small sensitivity ($\le 10\%$) to medium response.

Using $980{\mathrm{fb}}^{-1}$ of data at and around the $\mathrm{\Upsilon }(nS)$ ($n=1$, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, the two-photon process $\gamma \gamma \to \gamma \psi (2S)$ is studied from the threshold to 4.2 GeV for the first time. Two structures are seen in the invariant mass distribution of $\gamma \psi (2S)$: one at $M_{R_1}=3922.4\pm 6.5\pm 2.0\mathrm{MeV}/c^2$ with a width of ${\mathrm{\Gamma }}_{R_1}=22\pm 17\pm 4\mathrm{MeV}$, and another at $M_{R_2}=4014.3\pm 4.0\pm 1.5\mathrm{MeV}/c^2$ with a width of ${\mathrm{\Gamma }}_{R_2}=4\pm 11\pm 6\mathrm{MeV}$; the signals are parametrized with the incoherent sum of two Breit-Wigner functions. The first structure is consistent with the $X(3915)$ or the ${\chi }_{c2}(3930)$, and the local statistical significance is determined to be $3.1\sigma$ with the systematic uncertainties included. The second matches none of the known charmonium or charmoniumlike states, and its global significance is determined to be $2.8\sigma$ including the look-elsewhere effect. The production rates are ${\mathrm{\Gamma }}_{\gamma \gamma }\mathcal{B}(R_1\to \gamma \psi (2S))=9.8\pm 3.6\pm 1.3\mathrm{eV}$ assuming $(J^{PC},|\lambda |)=(0^{++},0)$ or $2.0\pm 0.7\pm 0.2\mathrm{eV}$ with $(2^{++},2)$ for the first structure and ${\mathrm{\Gamma }}_{\gamma \gamma }\mathcal{B}(R_2\to \gamma \psi (2S))=6.2\pm 2.2\pm 0.8\mathrm{eV}$ with $(0^{++},0)$ or $1.2\pm 0.4\pm 0.2\mathrm{eV}$ with $(2^{++},2)$ for the second. Here, the first errors are statistical and the second systematic, and $\lambda$ is the helicity.

We introduce a new paradigm for constructing accurate analytic waveforms (and fluxes) for eccentric compact binaries. Our recipe builds on the standard post-Newtonian (PN) approach but (i) retains implicit time-derivatives of the phase space variables in the instantaneous part of the noncircular waveform, and then (ii) suitably factorizes and resums this partly PN-implicit waveform using effective-one-body (EOB) procedures. We test our prescription against the exact results obtained by solving the Teukolsky equation with a test-mass source orbiting a Kerr black hole, and compare the use of the exact vs PN equations of motion for the time derivatives computation. Focusing only on the quadrupole contribution, we find that the use of the exact equations of motion yields an analytical/numerical agreement of the (averaged) angular momentum fluxes that is improved by 40% with respect to previous work, with 4.5% fractional difference for eccentricity $e=0.9$ and black hole dimensionless spin $-0.9\le \widehat{a}\le +0.9$. We also find a remarkable convergence trend between Newtonian, 1PN and 2PN results. Our approach carries over to the comparable mass case using the resummed EOB equations of motion and paves the way to faithful EOB-based waveform model for long-inspiral eccentric binaries for current and future gravitational wave detectors.

The black hole singularity plays a crucial role in formulating Hawking’s information paradox. The global spacetime analysis may be reconciled with unitarity by imposing a final state boundary condition on the spacelike singularity. Motivated by the final state proposal, we explore the effect of final state projection in two dimensional conformal field theories. We calculate the time evolution under postselection by employing the real part of pseudoentropy to estimate the amount of quantum entanglement averaged over histories between the initial and final states. We find that this quantity possesses a Page-curve-like behavior.

The renormalization group in effective quantum gravity can be consistently formulated using the Vilkovisky and DeWitt version of effective action and assuming a nonzero cosmological constant. Taking into account that the vacuum counterpart of the cosmological constant is dramatically different from the observed energy density of the vacuum, the running of the last quantity in the late cosmology indicates strong constraints on the physics beyond the minimal Standard Model of particle physics.

Finsler geometry is a natural and fundamental generalization of Riemann geometry. The Finsler structure depends on both coordinates and velocities. We present the arrival time delay of astroparticles subject to Lorentz violation in the framework of Finsler geometry, and the result corresponds to that derived by Jacob and Piran in the standard model of cosmology.

We wish to carry forward to higher dimensions the insightful and novel method of obtaining the Kerr metric proposed by one of us [Gen. Relativ. Gravit. 45, 2383 (2013)] for deriving the Myers-Perry rotating black hole metric. We begin with a flat spacetime metric written in oblate spheroidal coordinates (ellipsoidal geometry) appropriate for the inclusion of rotation, and then introduce arbitrary functions to introduce a gravitational potential due to mass, which are then determined by requiring that a massless particle experiences no acceleration, while a massive particle feels Newtonian acceleration at large $r$. We further generalize the method to include the cosmological constant $\mathrm{\Lambda }$ to obtain the Myers–Perry–de Sitter/anti–de Sitter black hole metric.

We obtain the classical holographic relation for the general Lovelock gravity and decompose the full Lagrangian into the bulk term and the surface term, expressed as a total derivative ${\partial }_{\mu }{J}^{\mu }$. By classical holographic relation, we mean that $J^{\mu }$ is determined completely by the bulk term. We find that the bulk term is not degenerate, or first order in this foliation-independent approach. We then consider the Arnowitt-Deser-Misner formalism where the foliation coordinate $w$ is treated as special. We obtain the classical holographic-degenerate relation with the first-order bulk term that does not involve higher than one derivative of $w$. For Einstein gravity, the two approaches lead to the same bulk term, but different ones for higher-order Lovelock gravities. The classical holographic-degenerate formulation in the Arnowitt-Deser-Misner approach allows us to consider alternative boundary conditions in the variation principle with different Myers terms. We show in the semiclassical approximation that the black hole entropy in all cases is the same as the one obtained under the standard Dirichlet boundary condition. We also generalize the formalism to general $f(L_{\text{Lovelock}}^{(k)})$ gravity.

We theoretically propose a finite-size quasi-one-dimensional Bose-Einstein condensate with coherent source and drain placed at its two ends, which can in principle sustain a stationary sonic black hole with a single event horizon. Our analysis is focused on the condensate persistence against quantum fluctuations. We show that similar to black hole-white hole pairs, dynamical instabilities occur. Investigating in detail the instabilities’ dependence on the system parameters, we also identify windows of formally infinite black hole lifetimes. By using quantum depletion of the condensate as a diagnostic tool, we validate the usage of Bogoliubov theory to describe the analog Hawking process, and establish novel signatures of Hawking radiation in the depleted cloud, both inside and outside the event horizon.

We consider the ultrarelativistic limit of the spin-2 and spin-3 conformal gravity theories in three dimensions, which leads to conformal Carrollian spin-2 gravity and its spin-3 analog. We also comment on the generalization of the result to arbitrary spin. The holographic examples show generalization in comparison with nonconformal Carrollian gravity.

We study gravitational lensing of light by hairy black holes, which, in a certain parameter regime, can possess two photon spheres of different size outside the event horizon. In particular, we focus on higher-order images of a pointlike light source and a luminous celestial sphere produced by strong gravitational lensing near photon spheres. Two photon spheres usually triple the number of high-order images of a pointlike light source. When a hairy black hole is illuminated by a celestial sphere, two photon spheres would give rise to two critical curves in the black hole image, and the smaller critical curve coincides with the shadow edge. In addition to a set of higher-order images of the celestial sphere outside the shadow edge, two more sets of higher-order images are observed inside and outside the larger critical curve, respectively.

The well-posedness of the gravitational equations of $f(R)$ gravity is studied in this paper. Three formulations of the $f(R)$ gravity with dynamical shifts [which are all based on the Arnowitt-Deser-Misner (ADM) formalism of the equations] are investigated. These three formulations are all proved to be strongly hyperbolic by pseudodifferential reduction. The first one is the Baumagarte-Shapiro-Shibata-Nakamura formulation with the so-called “hyperbolic $K$-driver” condition and the “hyperbolic Gamma driver” condition. The second one is the ADM formulation with modified harmonic gauge conditions. We find that the equations are not strong hyperbolic in traditional Z4 formulation for $f(R)$ gravity. So, in the third formulation, we improve the Z4 formulation, and show these equations are strong hyperbolic with modified harmonic gauge conditions.

One of the open problems in developing binary black hole (BBH) waveforms for gravitational wave astronomy is to model the intermediate-mass-ratio regime and connect it to the extreme-mass-ratio regime. A natural approach is to employ the effective-one-body (EOB) approach to the two-body dynamics that, by design, can cover the entire mass ratio range and naturally incorporates the extreme-mass-ratio limit. Here we use recently obtained numerical relativity (NR) data with mass ratios $m_1/m_2=(7,15,32,64,128)$ to test the accuracy of the state-of-the-art EOB model teobresums in the intermediate-mass-ratio regime. We generally find an excellent EOB/NR consistency around merger and ringdown for all mass ratios and for all available subdominant multipoles, except for the $\ell =m=5$ one. This mode can be crucially improved using the new large mass ratio NR data of this paper. The EOB/NR inspirals are also consistent with the estimated NR uncertainties. We also use several NR datasets taken by different public catalogs to probe the universal behavior of the multipolar hierarchy of waveform amplitudes at merger, that smoothly connects the equal-mass BBH to the test-mass result. Interestingly, the universal behavior is strengthened if the nonoscillatory memory contribution is included in the NR waveform. Future NR simulations with improved accuracy will be necessary to further probe, and possibly quantitatively refine, the teobresums transition from late inspiral to plunge in the intermediate-mass-ratio regime.

In this work, we explore the construction of the most general vector-tensor theory with an SU(2) global symmetry in the vector sector as a proposal for a modified theory of gravity. We start with a general Lagrangian containing terms involving symmetric and/or antisymmetric combinations of the covariant derivative of the vector field plus an arbitrary function of the vector field times the Ricci scalar. Then, we study the degeneracy of the full theory to determine whether it can be healthy or not. We find relations among some of the free functions in the Lagrangian that are necessary for the healthiness of the theory in correspondence with the several ways in which the kinetic matrix can be turned degenerate. Finally, we take the decoupling limit of the theory and find additional conditions on the free functions that are necessary for the healthiness of the longitudinal modes.