Binary black holes radiate linear momentum in gravitational waves as they merge. Recoils imparted to the black-hole remnant can reach thousands of $\mathrm{km}/\mathrm{s}$, thus ejecting black holes from their host galaxies. We exploit recent advances in gravitational waveform modeling to quickly and reliably extract recoils imparted to generic, precessing, black-hole binaries. Our procedure uses a numerical-relativity surrogate model to obtain the gravitational waveform given a set of binary parameters; then, from this waveform we directly integrate the gravitational-wave linear momentum flux. This entirely bypasses the need for fitting formulas which are typically used to model black-hole recoils in astrophysical contexts. We provide a thorough exploration of the black-hole kick phenomenology in the parameter space, summarizing and extending previous numerical results on the topic. Our extraction procedure is made publicly available as a module for the Python programming language named surrkick. Kick evaluations take $\sim 0.1\mathrm{s}$ on a standard off-the-shelf machine, thus making our code ideal to be ported to large-scale astrophysical studies.

We examine the variational problem in Lovelock gravity when the boundary contains timelike and spacelike segments nonsmoothly glued. We show that two kinds of contributions have to be added to the action. The first one is associated with the presence of a boundary in every segment and it depends on intrinsic and extrinsic curvatures. We can think of this contribution as adding a total derivative to the usual surface term of Lovelock gravity. The second one appears in every joint between two segments and it involves the integral along the joint of the Jacobson-Myers entropy density weighted by the Lorentz boost parameter, which relates the orthonormal frames in each segment. We argue that this term can be straightforwardly extended to the case of joints involving null boundaries. As an application, we compute the contribution of these terms to the complexity of global anti–de Sitter space in Lovelock gravity by using the “$\mathrm{complexity}=\mathrm{action}$” proposal and we identify possible universal terms for arbitrary values of the Lovelock couplings. We find that they depend on the charge $a^{*}$ controlling the holographic entanglement entropy and on a new constant that we characterize.

We study the perturbations to general relativistic black holes (i.e., those without scalar hair) in Horndeski scalar-tensor gravity. First, we derive the equations of odd and even parity perturbations of both the metric and scalar field in the case of a Schwarzschild black hole, and show that the gravitational waves emitted from such a system contain a mixture of quasinormal mode frequencies from the usual general relativistic spectrum and those from the new scalar field spectrum, with the new scalar spectrum characterized by just two free parameters. We then specialize to the subfamily of Horndeski theories in which gravitational waves propagate at the speed of light $c$ on cosmological backgrounds; the scalar quasinormal mode spectrum of such theories is characterized by just a single parameter $\mu$ acting as an effective mass of the scalar field. Analytical expressions for the quasinormal mode frequencies of the scalar spectrum in this subfamily of theories are provided for both static and slowly rotating black holes. In both regimes comparisons to quasinormal modes calculated numerically show good agreement with those calculated analytically in this work.

The (first-order) gravitational self-force correction to the spin-orbit precession of a spinning compact body along a slightly eccentric orbit around a Schwarzschild black hole is computed through the ninth post-Newtonian order and to second order in the eccentricity, improving recent results by Kavanagh et al. [Phys. Rev. D 96, 064012 (2017)]. We show that our higher-accurate theoretical estimates of the spin precession exhibits an improved agreement with corresponding numerical self-force data. We convert our new theoretical results into its corresponding effective-one-body counterpart, thereby determining several new post-Newtonian terms in the gyrogravitomagnetic ratio $g_{S*}$.

We study the static equilibrium configurations of uncharged and charged spheres composed by a relativistic polytropic fluid, and we compare with those of spheres composed by a nonrelativistic polytropic fluid, the later case being already studied in a previous work [J. D. Arbañil, P. S. Lemos, and V. T. Zanchin, Phys. Rev. D 88, 084023 (2013)]. An equation of state connecting the pressure $p$ and the energy density $\rho$ is assumed. In the nonrelativistic fluid case, the connection is through a nonrelativistic polytropic equation of state, $p=\omega {\rho }^{\gamma }$, with $\omega$ and $\gamma$ being respectively the polytropic constant and the polytropic exponent. In the relativistic fluid case, the connection is through a relativistic polytropic equation of state, $p=\omega {\delta }^{\gamma }$, with $\delta =\rho -p/(\gamma -1)$, and $\delta$ being the rest-mass density of the fluid. For the electric charge distribution, we assume that the charge density ${\rho }_e$ is proportional to the energy density $\rho$, ${\rho }_e=\alpha \rho$, with $\alpha$ being a constant such that $0\le |\alpha |\le 1$. The study is developed by integrating numerically the hydrostatic equilibrium equation. Some properties of the charged spheres such as the gravitational mass, the total electric charge, the radius, the surface redshift, and the speed of sound are analyzed by varying the central rest-mass density, the charge fraction, and the polytropic exponent. In addition, some limits that arise in general relativity, such as the Chandrasekhar limit, the Oppenheimer-Volkoff limit, the Buchdahl bound, and the Buchdahl-Andréasson bound are studied. It is confirmed that charged relativistic polytropic spheres with $\gamma \to \infty$ and $\alpha \to 1$ saturate the Buchdahl-Andréasson bound, thus indicating that it reaches the quasiblack hole configuration. We show by means of numerical analysis that, as expected, the major differences between the two cases appear in the high energy density region.

Most theories that predict time and/or space variation of fundamental constants also predict violations of the weak equivalence principle (WEP). In 2004 Khoury and Weltman [1] proposed the so called chameleon field arguing that it could help avoiding experimental bounds on the WEP while having a nontrivial cosmological impact. In this paper we revisit the extent to which these expectations continue to hold as we enter the regime of high precision tests. The basis of the study is the development of a new method for computing the force between two massive bodies induced by the chameleon field which takes into account the influence on the field by both, the large and the test bodies. We confirm that in the thin shell regime the force does depend nontrivially on the test body’s composition, even when the chameleon coupling constants ${\beta }^i=\beta$ are universal. We also propose a simple criterion based on energy minimization, that we use to determine which of the approximations used in computing the scalar field in a two body problem is better in each specific regime. As an application of our analysis we then compare the resulting differential acceleration of two test bodies with the corresponding bounds obtained from Eötvös type experiments. We consider two setups: (1) an Earth based experiment where the test bodies are made of Be and Al; (2) the Lunar Laser Ranging experiment. We find that for some choices of the free parameters of the chameleon model the predictions of the Eötvös parameter are larger than some of the previous estimates. As a consequence, we put new constrains on these free parameters. Our conclusions strongly suggest that the properties of immunity from experimental tests of the WEP, usually attributed to the chameleon and related models, should be carefully reconsidered. An important result of our analysis is that our approach leads to new constraints on the parameter space of the chameleon models.

We consider a four-flavor scenario for the neutrinos where an extra sterile neutrino is introduced to the three families of active neutrinos and study the deviation from the three-flavor scenario in the ultrahigh-energy (UHE) regime. We calculate the possible muon and shower yields at a $1{\mathrm{km}}^2$ detector such as IceCube for these neutrinos from distant UHE sources, e.g., gamma-ray bursts, etc. Similar estimations for muon and shower yields are also obtained for the three-flavor case. Comparing the two results, we find considerable differences between the yields for these two cases. This can be useful for probing the existence of a fourth sterile component using UHE neutrino flux.

We study the effect of a strong constant magnetic field, generated in relativistic heavy ion collisions, on the heavy quark complex potential. We work in the strong magnetic field limit with the lowest Landau level approximation. We find that the screening of the real part of the potential increases with the increase in the magnetic field. Therefore, we expect less binding of the $Q\overline{Q}$ pair in the presence of a strong magnetic field. The imaginary part of the potential increases in magnitude with the increase in magnetic field, leading to an increase of the width of the quarkonium state with the magnetic field. All of these effects result in the early dissociation of $Q\overline{Q}$ states in a magnetized hot quark-gluon plasma medium.

We consider the effects of the spin-2 particle in the $b\to s{\mu }^{+}{\mu }^{-}$ transition assuming that the spin-2 particle couples in a flavor-nonuniversal way to $b$ and $s$ quarks and in the leptonic sector couples only to the muons, thereby only contributing to the process $b\to s{\mu }^{+}{\mu }^{-}$. The $B_s-{\overline{B}}_s$ transition gives the strong constraint on the coupling of the spin-2 mediator and $b$ and $s$ quarks, while the observed discrepancy from the standard model prediction for the muon anomalous magnetic moment $(g-2{)}_{\mu }$ serves to constrain the $\mu$ coupling to a spin-2 particle. We find that the spin-2 particle can modify the angular observables in the $B\to K{\mu }^{+}{\mu }^{-}$ and $B\to K^{*}{\mu }^{+}{\mu }^{-}$ decays and produce effects that do not exist in the standard model. The generated forward-backward asymmetries in these processes can reach 15%, while other observables for these decays receive tiny effects.

Many new physics models that explain the intriguing anomalies in the $b$-quark flavor sector are severely constrained by $B_s$ mixing, for which the Standard Model prediction and experiment agreed well until recently. The most recent Flavour Lattice Averaging Group (FLAG) average of lattice results for the nonperturbative matrix elements points, however, in the direction of a small discrepancy in this observable Cabibbo-Kobayashi-Maskawa (CKM). Using up-to-date inputs from standard sources such as PDG, FLAG and one of the two leading CKM fitting groups to determine $\mathrm{\Delta }{M}_s^{\mathrm{SM}}$, we find a severe reduction of the allowed parameter space of $Z^{\prime }$ and leptoquark models explaining the $B$ anomalies. Remarkably, in the former case the upper bound on the $Z^{\prime }$ mass approaches dangerously close to the energy scales already probed by the LHC. We finally identify some model-building directions in order to alleviate the tension with $B_s$ mixing.

In this work we study the effects of new-physics (NP) operators with different Lorentz structures on the inclusive $B\to X_c\tau \overline{\nu }$ decay and make predictions for the ratio of total decay rates $R(X_c)=\frac{\mathrm{\Gamma }(B\to X_c\tau {\overline{\nu }}_{\tau })}{\mathrm{\Gamma }(B\to X_c\ell {\overline{\nu }}_{\ell })}$ with $\ell =e$, $\mu$, the differential decay rates, $\frac{d\mathrm{\Gamma }}{d{q}^2}$ and $\frac{d\mathrm{\Gamma }}{d{E}_{\tau }}$, forward-backward asymmetry $A_{\mathrm{F}\mathrm{B}}$ and the ratio of the differential decay rates $B(q^2)=\frac{d\mathrm{\Gamma }(B\to X_c\tau {\overline{\nu }}_{\tau })/d{q}^2}{d\mathrm{\Gamma }(B\to X_c\ell {\overline{\nu }}_{\ell })/d{q}^2}$. In addition, we introduce some leptoquark models as explicit models of the NP operators and study their effects on the inclusive decay. We consider $\mathcal{O}({\alpha }_s)$ radiative and $1/m_b$ nonperturbative corrections to the Standard Model (SM) decay rate and ignore their small effects in the NP contributions.

We explore strategies for probing hidden valley scenarios exhibiting confinement. Such scenarios lead to a moderate multiplicity of light hidden hadrons for generic showering and hadronization similar to QCD. Their decays are typically soft and displaced, making them challenging to probe with traditional LHC searches. We show that the low trigger requirements and excellent track and vertex reconstruction at LHCb provide a favorable environment to search for such signals. We propose novel search strategies in both muonic and hadronic channels. We also study existing ATLAS and CMS searches and compare them with our proposals at LHCb. We find that the reach at LHCb is generically better in the parameter space we consider here, even with optimistic background estimations for ATLAS and CMS searches. We discuss potential modifications at ATLAS and CMS that might make these experiments competitive with the LHCb reach. Our proposed searches can be applied to general hidden valley models as well as exotic Higgs boson decays, such as in twin Higgs models.

We consider the central exclusive production of the $p\overline{p}$ in the continuum and via resonances in proton-proton collisions at high energies. We discuss the diffractive mechanism calculated within the tensor-Pomeron approach including Pomeron, Odderon, and Reggeon exchanges. The theoretical results are discussed in the context of existing WA102 and Intersecting Storage Rings experimental data, and predictions for planned or current experiments at the Relativistic Heavy Ion Collider and the LHC are presented. The distribution in ${\mathrm{y}}_{\mathrm{diff}}$, the rapidity distance between the proton and antiproton, is particularly interesting. We find a dip at ${\mathrm{y}}_{\mathrm{diff}}=0$ for the $p\overline{p}$ production, in contrast to the ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ production. We predict also the $p\overline{p}$ invariant-mass distribution to be less steep than for the pairs of pseudoscalar mesons. We argue that these specific differences for the $p\overline{p}$ production with respect to the pseudoscalar meson pair production can be attributed to the proper treatment of the spin of produced particles. We discuss asymmetries that are due to the interference of $C=+1$ and $C=-1$ amplitudes of $p\overline{p}$ production. We have also calculated the cross section for the $pp\to pp\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ reaction. Here, the cross section is smaller, but the characteristic feature for $d\sigma /d{\mathrm{y}}_{\mathrm{diff}}$ is predicted to be similar to $p\overline{p}$ production. The presence of resonances in the $p\overline{p}$ channel may destroy the dip at ${\mathrm{y}}_{\mathrm{diff}}=0$. This opens the possibility to study diffractively produced resonances. We discuss the observables suited for this purpose.

After the experimental establishment of doubly heavy baryons, baryons with three quarks are the last missing pieces of the lowest-lying baryon multiplets in the quark model. In this work, we study semileptonic and nonleptonic weak decays of triply heavy baryons, ${\mathrm{\Omega }}_{ccc}^{++}$, ${\mathrm{\Omega }}_{ccb}^{+}$, ${\mathrm{\Omega }}_{cbb}^0$, and ${\mathrm{\Omega }}_{bbb}^{-}$. Decay amplitudes for various channels are parametrized in terms of a few SU(3) irreducible amplitudes. We point out that branching fractions for Cabibbo-allowed processes, ${\mathrm{\Omega }}_{ccc}^{++}\to ({\mathrm{\Xi }}_{cc}^{++}{\overline{K}}^0,{\mathrm{\Xi }}_{cc}^{++}{K}^{-}{\pi }^{+},{\mathrm{\Omega }}_{cc}^{+}{\pi }^{+},{\mathrm{\Xi }}_c^{+}{D}^{+},{\mathrm{\Xi }}_c^{\prime }{D}^{+},{\mathrm{\Lambda }}_c{D}^{+}{\overline{K}}^0,{\mathrm{\Xi }}_c^{+}{D}^0{\pi }^{+},{\mathrm{\Xi }}_c^0{D}^{+}{\pi }^{+})$, may reach a few percent. We suggest our experimental colleagues to perform a search at hadron colliders and the electron and positron collisions in the future, which will presumably lead to discoveries of triply heavy baryons and complete the baryon multiplets. Using the expanded amplitudes, we derive a number of relations for the partial widths that can be examined in the future.

We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of $92\mathrm{V}/\mathrm{cm}$, $154\mathrm{V}/\mathrm{cm}$ and $366\mathrm{V}/\mathrm{cm}$ using the XENON100 detector. A data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of $366\mathrm{V}/\mathrm{cm}$ are presented. The electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. The results provide new measurements in the energy region of interest for dark matter searches using liquid xenon.

It is now well understood that Ward identities associated with the (extended) BMS algebra are equivalent to single soft graviton theorems. In this work, we show that if we consider nested Ward identities constructed out of two BMS charges, a class of double soft factorization theorems can be recovered. By making connections with earlier works in the literature, we argue that at the subleading order, these double soft graviton theorems are the so-called consecutive double soft graviton theorems. We also show how these nested Ward identities can be understood as Ward identities associated with BMS symmetries in scattering states defined around (non-Fock) vacua parametrized by supertranslations or superrotations.

We find a formulation of $\mathcal{N}=2$ supersymmetric Yang-Mills theory in projective superspace. In particular we find an expression for the field strength in terms of an unconstrained prepotential which is desirable when quantizing the theory. We use this to write the action in terms of the prepotential and show that it reduces to the known result in the Abelian limit.

We complement Weinberg’s no-go theorem on the cosmological constant problem in quantum gravity by generalizing it to the case of a scale-invariant theory. Our analysis makes use of the effective action and the BRST symmetry in a manifestly covariant quantum gravity instead of the classical Lagrangian density and the $GL(4)$ symmetry in classical gravity. In this sense, our proof is very general since it does not depend on details of quantum gravity and holds true for general gravitational theories which are invariant under diffeomorphisms. As an application of our theorem, we comment on an idea that in the asymptotic safety scenario the functional renormalization flow drives a cosmological constant to zero, solving the cosmological constant problem without reference to fine tuning of parameters. Finally, we also comment on the possibility of extending the Weinberg theorem in quantum gravity to the case where the translational invariance is spontaneously broken.

The teleparallel formulation of gravity theories reveals close structural analogies to electrodynamics, which are more hidden in their usual formulation in terms of the curvature of spacetime. We show how every locally Lorentz invariant teleparallel theory of gravity with second-order field equations can be understood as built from a gravitational field strength and excitation tensor which are related to each other by a constitutive relation, analogous to the premetric construction of theories of electrodynamics. We demonstrate how the previously studied models of $f(\mathbb{T})$ and $f(T_{\mathrm{ax}},T_{\mathrm{ten}},T_{\mathrm{vec}})$ gravity as well as teleparallel dark energy can be formulated in this language. The advantage of this approach to gravity is that the field equations for different models all take the same compact form and general results can be obtained. An important new such result we find is a constraint which relates the field equations of the tetrad and the spin connection.

We discuss the manner in which the primordial magnetic field (PMF) suppresses the cosmic microwave background (CMB) $B$ mode due to the weak-lensing (WL) effect. The WL effect depends on the lensing potential (LP) caused by matter perturbations, the distribution of which at cosmological scales is given by the matter power spectrum (MPS). Therefore, the WL effect on the CMB $B$ mode is affected by the MPS. Considering the effect of the ensemble average energy density of the PMF, which we call “the background PMF,” on the MPS, the amplitude of MPS is suppressed in the wave number range of $k>0.01h{\mathrm{Mpc}}^{-1}$. The MPS affects the LP and the WL effect in the CMB $B$ mode; however, the PMF can damp this effect. Previous studies of the CMB $B$ mode with the PMF have only considered the vector and tensor modes. These modes boost the CMB $B$ mode in the multipole range of $\ell >1000$, whereas the background PMF damps the CMB $B$ mode owing to the WL effect in the entire multipole range. The matter density in the Universe controls the WL effect. Therefore, when we constrain the PMF and the matter density parameters from cosmological observational data sets, including the CMB $B$ mode, we expect degeneracy between these parameters. The CMB $B$ mode also provides important information on the background gravitational waves, inflation theory, matter density fluctuations, and the structure formations at the cosmological scale through the cosmological parameter search. If we study these topics and correctly constrain the cosmological parameters from cosmological observations, including the CMB $B$ mode, we need to correctly consider the background PMF.