We study the process $pp\to Z({\ell }^{+}{\ell }^{-})h(b\overline{b})$ in the standard model effective field theory (SMEFT) at high energies using subjet techniques to reconstruct the Higgs boson. We show that at high energies this process probes four directions in the dimension-6 EFT space, namely the operators that contribute to the four contact interactions, $h{Z}_{\mu }\overline{f}{\gamma }^{\mu }f$, where $f=u_L,u_R,d_L$ and $d_R$. These four directions are, however, already constrained by the $Z$-pole and diboson measurements at LEP. We show that by utilizing the energy growth of this process in the SMEFT and the accuracy that can be achieved by using subjet techniques at the High Luminosity LHC, one can obtain bounds on these operators that are an order of magnitude better than existing LEP bounds.

We calculate the magnetic moments of spin-$\frac{3}{2}$ singly charmed baryons in the heavy baryon chiral perturbation theory (HBChPT). The analytical expressions are given up to $\mathcal{O}(p^3)$. The heavy quark symmetry is used to reduce the number of low energy constants (LECs). With the lattice QCD simulation data as the magnetic moments of the charmed baryons, the numerical results are given up to $\mathcal{O}(p^3)$ in three scenarios. In the first scenario, we use the results in the quark model as the leading order input. In the second scenario, we use the heavy quark symmetry and neglect the contribution of heavy quark. In the third scenario, the heavy quark contribution is considered on the basis of the scenario II and the magnetic moments of singly bottom baryons are given as a by-product.

Exclusive semileptonic decays based on $b\to s$ transitions have attracted a lot of attention as some angular observables deviate significantly from the standard model (SM) predictions. B meson decays induced by other flavor changing neutral current (FCNC), $b\to d$, can also offer a probe to new physics with an additional sensitivity to the weak phase in the Cabibbo-Kobayashi-Maskawa (CKM) matrix. We provide predictions for angular observables for $b\to d$ semileptonic transitions, namely ${\overline{B}}_s\to K^{*}{\ell }^{+}{\ell }^{-}$, ${\overline{B}}^0\to {\rho }^0{\ell }^{+}{\ell }^{-}$, and their $CP$-conjugated modes including various nonfactorizable corrections. For ${\overline{B}}^0\to {\rho }^0{\ell }^{+}{\ell }^{-}$ mode, $B^0-{\overline{B}}^0$ mixing effects have been included and predictions are made for Belle and LHCb separately. Study of these decay modes will be useful in its own right and to understand the pattern of deviations in $b\to s$ transitions.

It is widely known that the $ZH$ production channel provides a promising probe to the $H\to b\overline{b}$ decay at the LHC, when the Higgs and the $Z$ bosons are highly boosted along the transverse direction. We show how information on the $Z$ boson polarization—that is disregarded in the current LHC analyses—can relevantly improve the signal from background discrimination, helping us to observe and achieve a larger precision for the $H\to b\overline{b}$ measurement in the $Z(\ell \ell )H$ channel.

Direct searches for lepton flavor violation in decays of the $Z$ boson with the ATLAS detector at the LHC are presented. Decays of the $Z$ boson into an electron or muon and a hadronically decaying $\tau$ lepton are considered. The searches are based on a data sample of proton-proton collisions collected by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of $36.1{\mathrm{fb}}^{-1}$ at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$. No statistically significant excess of events above the expected background is observed, and upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95% confidence level: $\mathcal{B}(Z\to e\tau )<5.8\times {10}^{-5}$ and $\mathcal{B}(Z\to \mu \tau )<2.4\times {10}^{-5}$. This is the first limit on $\mathcal{B}(Z\to e\tau )$ with ATLAS data. The upper limit on $\mathcal{B}(Z\to \mu \tau )$ is combined with a previous ATLAS result based on $20.3{\mathrm{fb}}^{-1}$ of proton-proton collision data at a center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$ and the combined upper limit at 95% confidence level is $\mathcal{B}(Z\to \mu \tau )<1.3\times {10}^{-5}$.

By analyzing an $e^{+}{e}^{-}$ data sample corresponding to an integrated luminosity of $2.93{\mathrm{fb}}^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fractions of the Cabibbo-favored hadronic decays $D^0\to K^{-}{\pi }^{+}{\eta }^{\prime }$, $D^0\to K_S^0{\pi }^0{\eta }^{\prime }$, and $D^{+}\to K_S^0{\pi }^{+}{\eta }^{\prime }$, which are determined to be $(6.43\pm 0.15_{\mathrm{stat}}\pm 0.31_{\mathrm{syst}})\times {10}^{-3}$, $(2.52\pm 0.22_{\mathrm{stat}}\pm 0.15_{\mathrm{syst}})\times {10}^{-3}$, and $(1.90\pm 0.17_{\mathrm{stat}}\pm 0.13_{\mathrm{syst}})\times {10}^{-3}$, respectively. The precision of the branching fraction of $D^0\to K^{-}{\pi }^{+}{\eta }^{\prime }$ is significantly improved, and the processes $D^0\to K_S^0{\pi }^0{\eta }^{\prime }$ and $D^{+}\to K_S^0{\pi }^{+}{\eta }^{\prime }$ are observed for the first time.

We study the mixing problem of the determinantlike operators in ABJM theory to two-loop order in the scalar sector. The gravity duals of these operators are open strings attached to the maximal giant graviton, which is a D4-brane wrapping a ${\mathbb{C}\mathbb{P}}^2$ inside ${\mathbb{C}\mathbb{P}}^3$ in our case. The anomalous dimension matrix of these operators can be regarded as an open spin chain Hamiltonian. We provide strong evidence of its integrability based on coordinate Bethe ansatz method and boundary Yang-Baxter equations.

We study the shadow cast by a large gravitating sphere, similar to our Sun. For this, we consider the gravitational field produced by a static mass monopole within the first post-Newtonian approximation of the general theory of relativity. We study the propagation of a monochromatic electromagnetic wave in the vicinity of a large, opaque, gravitating sphere. To treat the opaque nature of the body and its physical size, we implement fully absorbing boundary conditions and develop a wave-optical treatment of the shadow formed by this object. Based on this approach, we demonstrate that the structure of the shadow is determined by the Schwarzschild radius of the body and its physical size. The shadow’s boundary has the shape of a concave rotational hyperboloid bent inward due to the refractive properties of the curved spacetime. We show that there is no light in the shadow. However, even in the presence of gravity and related gravitational bending of photon trajectories there is the bright spot of Arago that is formed behind a perfectly spherical obscuration.

We present improvements to the construction of binary black hole initial data used in the Spectral Einstein Code (SpEC). We introduce new boundary conditions for the extended conformal thin sandwich elliptic equations that enforce the excision surfaces to be slightly inside rather than on the apparent horizons, thus avoiding extrapolation into the black holes at the last stage of initial data construction. We find that this improves initial data constraint violations near and inside the apparent horizons by about 3 orders of magnitude. We construct several initial data sets that are intended to be astrophysically equivalent but use different free data, boundary conditions, and initial gauge conditions. These include free data chosen as a superposition of two black holes in time-independent horizon-penetrating harmonic and damped harmonic coordinates. We also implement initial data for which the initial gauge satisfies the harmonic and damped harmonic gauge conditions; this can be done independently of the free data, since this amounts to a choice of the time derivatives of the lapse and shift. We compare these initial data sets by evolving them. We show that the gravitational waveforms extracted during the evolution of these different initial data sets agree very well after excluding initial transients. However, we do find small differences between these waveforms, which we attribute to small differences in initial orbital eccentricity, and in initial BH masses and spins, resulting from the different choices of free data. Among the cases considered, we find that superposed harmonic initial data lead to significantly smaller transients, smaller variation in BH spins and masses during these transients, smaller constraint violations, and more computationally efficient evolutions. Finally, we study the impact of initial data choices on the construction of zero-eccentricity initial data.

In this paper I will first outline an effective field theory for cosmology (EFTC) that is based on the standard model coupled to general relativity and improved with Weyl symmetry. There are no new physical degrees of freedom in this theory, but what is new is an enlargement of the domain of the existing physical fields and of spacetime via the larger symmetry, thus curing the geodesic incompleteness of the traditional theory. Invoking the softer behavior of an underlying theory of quantum gravity, I further argue that it is reasonable to ban higher curvature terms in the effective action, thus making this EFTC mathematically well behaved at gravitational singularities, as well as geodesically complete, thus able to make new physics predictions. Using this EFTC, I show some predictions of surprising behavior of the universe at singularities including a unique set of big-bang initial conditions that emerge from a dynamical attractor mechanism. I will illustrate this behavior with detailed formulas and plots of the classical solutions and the quantum wavefunction that are continuous across singularities for a cosmology that includes the past and future of the big bang. The solutions are given in the geodesically complete global minisuperspace that is similar to the extended spacetime of a black hole or extended Rindler spacetime. The analytic continuation of the quantum wavefunction across the horizons describes the passage through the singularities. This analytic continuation solves a long-standing problem of the singular $(-1/r^2)$ potential in quantum mechanics that dates back to Von Neumann. The analytic properties of the wavefunction also reveal an infinite stack of universes sewn together at the horizons of the geodesically complete space. Finally a comparison with recent papers using the path integral approach in cosmology is given.

We consider the flavor transformation of neutrinos through oscillatory matter profiles. We show that the neutrino oscillation Hamiltonian in this case describes a Rabi system with an infinite number of Rabi modes. We further show that, in a given physics problem, the majority of the Rabi modes have too small amplitudes to be relevant. We also go beyond the rotating wave approximation and derive the relative detuning of the Rabi resonance when multiple Rabi modes with small amplitudes are present. We provide an explicit criterion of whether an off-resonance Rabi mode can affect the parametric flavor transformation of the neutrino.

Motivated by the idea of comprehensive unification, we study a gauged $SO(3)$ flavor extension of the extended Standard Model, including right-handed neutrinos and a Peccei-Quinn symmetry with simple charge assignments. The model accommodates the observed fermion masses and mixings and yields a characteristic, successful relation among them. The Peccei-Quinn symmetry is an essential ingredient.

A search is performed for a heavy particle decaying into different-flavor, dilepton pairs ($e\mu$, $e\tau$ or $\mu \tau$), using $36.1{\mathrm{fb}}^{-1}$ of proton-proton collision data at $\sqrt{s}=13\mathrm{TeV}$ collected in 2015–2016 by the ATLAS detector at the Large Hadron Collider. No excesses over the Standard Model predictions are observed. Bayesian lower limits at the 95% credibility level are placed on the mass of a $Z^{\prime }$ boson, the mass of a supersymmetric $\tau$-sneutrino, and on the threshold mass for quantum black-hole production. For the $Z^{\prime }$ and sneutrino models, upper cross-section limits are converted to upper limits on couplings, which are compared with similar limits from low-energy experiments and which are more stringent for the $e\tau$ and $\mu \tau$ modes.

We study the effect of the Gauss-Bonnet term on the complexity growth rate of dual field theory using the “complexity-volume” (CV) and CV2.0 conjectures. We investigate the late time value and full time evolution of the complexity growth rate of the Gauss-Bonnet black holes with horizons with zero curvature ($k=0$), positive curvature ($k=1$) and negative curvature ($k=-1$), respectively. For the $k=0$ and $k=1$ cases, we find that the Gauss-Bonnet term suppresses the growth rate as expected, while in the $k=-1$ case the effect of the Gauss-Bonnet term may be opposite to what is expected. The reason for it is briefly discussed, and the comparison of our results to the result obtained by using the “complexity-action” (CA) conjecture is also presented. We also briefly investigate two proposals applying some generalized volume functionals dual to the complexity in higher curvature gravity theories, and find their behaviors are different for $k=0$ at late times.

We present evidence for the connection between the potential of different fields and complexity growth rates both in conformal and confining cases. By studying different models, we also establish a strong connection between phase transitions and the discontinuities in the complexity growth rates. In the first example, for dyonic black holes that are dual to van der Waals fluids, we find a similar first-order phase transition in the behavior of the complexity growth rate. We then compare the Schwinger effect and also the behavior of complexity in the anti–de Sitter (AdS) and AdS soliton backgrounds and comment on the connection between them. Finally, in a general Gubser model of QCD, we present the connections between the potentials, entropies, speeds of sound, and complexity growth rates during crossover and first- and second-order phase transitions, and also the behavior of quasinormal modes.

Baryonic states are sufficiently complex to reveal physics that is hidden in the mesonic bound states. Using gauge/gravity correspondence we study analytically and numerically baryons in theories with space-dependent $\theta$-terms, or theories under strong magnetic fields. Such holographic studies on baryons are accommodated in a generic analytic framework we develop for anisotropic theories, where their qualitative features are common irrespective of the source that triggers the anisotropy. We find that the distribution of the quarks forming the state, depends on the angle between the baryon and the anisotropic direction. Its shape is increasingly elliptic with respect to the strength of the field sourcing the anisotropy, counterbalancing the broken rotational invariance on the gluonic degrees of freedom. Strikingly, the baryons dissociate in stages with a process that depends on the proximity of the quarks to the anisotropic direction, where certain quark pairs abandon the bound state first, followed by the closest pairs to them as the temperature increases. This observation may also serve as a way to identify the nature of certain exotic states. Finally, we investigate holographic baryons with a decreased number of quarks and explain why in theories under consideration the presence of anisotropy does not modify the universal stability condition in contrast to the usual trend.

Euclidean gravity provides an interesting test system for an analysis of cosmological perturbations in an effective Hamiltonian constraint with holonomy modifications from loop quantum gravity. This paper presents a discussion of scalar modes, with a specific form of the holonomy modification function derived from a general expansion in a connection formulation. Compared with some previous models, the constraint brackets are deformed in a different and more restricted way. A general comparison of anomaly-free brackets in various effective and operator versions shows an overall consistency between the different approaches.

We discuss quantum black holes in asymptotically safe quantum gravity with a scale identification based on the Kretschmann scalar. After comparing this scenario with other scale identifications, we investigate in detail the Kerr–(A)dS and Schwarzschild–(A)dS spacetimes. The global structure of these geometries is studied as well as the central curvature singularity and test particle trajectories. The existence of a Planck-sized, extremal, zero-temperature black hole remnant guarantees a stable end point of the evaporation process via Hawking radiation.

We present a higher order generalization of the clockwork mechanism starting from an underlying nonlinear multigravity theory with a single scale and nearest neighbor ghost-free interactions. Without introducing any hierarchies in the underlying potential, this admits a family of Minkowski vacua around which massless graviton fluctuations couple to matter exponentially more weakly than the heavy modes. Although multidiffeomorphisms are broken to the diagonal subgroup in our theory, an asymmetric distribution of conformal factors in the background vacua translates this diagonal symmetry into an asymmetric shift of the graviton gears. In particular we present a TeV scale multigravity model with $\mathcal{O}(10)$ sites that contains a massless mode whose coupling to matter is Planckian, and a tower of massive modes starting at a TeV mass range and with TeV strength couplings. This suggests a possible application to the hierarchy problem as well as a candidate for dark matter.

We study the perturbations of scalar, vector, and tensor fields in a slowly rotating Kerr–(anti–)de Sitter black hole spacetime, presenting new and existing Schrödinger-style master equations for each type of perturbation up to linear order in black hole spin $a$. For each type of field, we calculate analytical expressions for the fundamental quasinormal mode frequencies. These frequencies are compared to existing results for Schwarzschild–de Sitter, slowly rotating Kerr, and slowly rotating Kerr–de Sitter black holes. In all cases, good agreement is found between the analytic expressions and those frequencies calculated numerically. In addition, the axial and polar gravitational frequencies are shown to be isospectral to linear order in $a$ for all cases other than for both nonzero $a$ and $\mathrm{\Lambda }$.