AMS-02 provided the unprecedented statistics in the measurement of the positron fraction from cosmic rays. That may offer a unique opportunity to distinguish the positron spectrum coming from various dark matter (DM) annihilation channels, if DM is the source of this positron excess. Therefore, we consider the scenario that the DM can annihilate into leptonic, quark, and massive gauge-boson channels simultaneously with floating branching ratios to test this hypothesis. We also study the impacts from MAX, MED, MIN, and DC diffusion models as well as from isothermal, NFW, and Einasto DM density profiles on our results. We found two parameter regions that can satisfy both AMS-02 $\frac{e^{+}}{e^{+}+e^{-}}$ and $\overline{p}/p$ data sets at 95% C.L.: (i) under the NFW-MIN combination with $M_{\chi }\subset [10,30]\mathrm{TeV}$, and (ii) under the Einasto-DC combination with $M_{\chi }\subset [500,1500]\mathrm{GeV}$.

Dark matter may be charged under dark electromagnetism with a dark photon that kinetically mixes with the Standard Model photon. In this framework, dark matter will collect at the center of the Earth and annihilate into dark photons, which may reach the surface of the Earth and decay into observable particles. We determine the resulting signal rates, including Sommerfeld enhancements, which play an important role in bringing the Earth’s dark matter population to their maximal, equilibrium value. For dark matter masses $m_X\sim 100\mathrm{GeV}–10\mathrm{TeV}$, dark photon masses $m_{A^{\prime }}\sim \mathrm{MeV}–\mathrm{GeV}$, and kinetic mixing parameters $ϵ\sim 10^{-9}–10^{-7}$, the resulting electrons, muons, photons, and hadrons that point back to the center of the Earth are a smoking-gun signal of dark matter that may be detected by a variety of experiments, including neutrino telescopes, such as IceCube, and space-based cosmic ray detectors, such as Fermi-LAT and AMS. We determine the signal rates and characteristics and show that large and striking signals—such as parallel muon tracks—are possible in regions of the $(m_{A^{\prime }},ϵ)$ plane that are not probed by direct detection, accelerator experiments, or astrophysical observations.

We report on a calculation of the $B^{*}B\pi$ coupling in three-flavor lattice QCD. This coupling, defined from the strong-interaction matrix element $⟨B\pi |B^{*}⟩$, is related to the leading order low-energy constant in heavy meson chiral perturbation theory. We carry out our calculation directly at the $b$-quark mass using a nonperturbatively tuned clover action that controls discretization effects of order $|\overrightarrow{p}a|$ and $(ma{)}^n$ for all $n$. Our analysis is performed on RBC/UKQCD gauge configurations using domain-wall fermions and the Iwasaki gauge action at two lattice spacings of $a^{-1}=1.729(25)\mathrm{GeV}$, $a^{-1}=2.281(28)\mathrm{GeV}$, and unitary pion masses down to 290 MeV. We achieve good statistical precision and control all systematic uncertainties, giving a final result for the coupling $g_b=0.56(3{)}_{\text{stat}}(7{)}_{\text{sys}}$ in the continuum and at the physical light-quark masses. This is the first calculation performed directly at the physical $b$-quark mass and lies in the region one would expect from carrying out an interpolation between previous results at the charm mass and at the static point.

We demonstrate that the recent measurement of azimuthally collimated, long-range rapidity (“ridge”) correlations in $\sqrt{s}=13\mathrm{TeV}$ proton-proton ($p+p$) collisions by the ATLAS Collaboration at the LHC are in agreement with expectations from the color glass condensate effective theory of high-energy QCD. The observation that the integrated near-side yield as a function of multiplicity is independent of collision energy is a natural consequence of the fact that multiparticle production is driven by a single semihard saturation scale in the color glass condensate framework. We argue further that the azimuthal structure of these recent ATLAS ridge measurements strongly constrains hydrodynamic interpretations of such correlations in high-multiplicity $p+p$ collisions.

Nambu–Jona-Lasinio-type models have been used extensively to study the dynamics of the theory of the strong interaction at finite temperature and quark chemical potential on a phenomenological level. In addition to these studies, which are often performed under the assumption that the ground state of the theory is homogeneous, searches for the existence of crystalline phases associated with inhomogeneous ground states have attracted a lot of interest in recent years. In this work, we study the Polyakov-loop extended Nambu–Jona-Lasinio model using two prominent parametrizations and find that the existence of a crystalline phase is stable against a variation of the parametrization of the underlying Polyakov loop potential.

We critically examine the potential to disentangle the Standard Model (SM) and new physics (NP) in $B\to K^{*}{\mu }^{+}{\mu }^{-}$ and $B\to K^{*}{e}^{+}{e}^{-}$ decays, focusing on (i) the LHCb anomaly, (ii) the search for right-handed currents, and (iii) lepton-universality violation. Restricting ourselves to the large-recoil region, we advocate a parametrization of the hadronic matrix elements that separates model-independent information about nonperturbative QCD from the results of model calculations. We clarify how to estimate corrections to the heavy-quark limit that would generate a right-handed (virtual) photon in the $b\to s\gamma$ contribution to the decay. We then apply this approach to the discussion of various sets of observables of increasing theoretical cleanness. First, we show that angular observables in the optimized $P_i^{(\prime )}$ basis are, in general, still not robust against the long-distance QCD effects, both numerically and by examining analytically the dependence on corrections to the (model-independent) heavy-quark limit. As a result, while a fit to data favors a NP contribution to the semileptonic operators of the type $\delta C_9\simeq -1.5$, this comes at a relatively small statistical significance of $\lesssim 2\sigma$ once such power corrections are properly accounted for. Second, two of these observables, $P_1$ and $P_3^{CP}$, are particularly clean at very low $q^2$ and sensitive probes of right-handed quark currents. We discuss their potential to set stringent bounds on the Wilson coefficient $C_7^{\prime }$, especially using data of the electronic mode, and we update the bounds with current angular data in the muonic channel. Finally, in light of the recent hint of lepton-universality violation in $B^{+}\to K^{+}\ell \ell$, we introduce and investigate new lepton-universality observables involving angular observables of the muonic and electronic modes and their zero crossings and show that, if the effect is of the size suggested by experiment, these can clearly distinguish between different NP explanations in terms of underlying semileptonic operators.

The radiative neutrino mass model with inert doublet dark matter is a promising model for the present experimental issues which cannot be explained within the standard model. We study an extension of this model focusing on cosmological features brought about from the scalar sector. Inflation due to singlet scalars with hierarchical nonminimal couplings with the Ricci scalar may give a favorable solution for both neutrino masses and baryon number asymmetry in the Universe.

We consider a model of neutrino mass with a scalar triplet $({\xi }^{++},{\xi }^{+},{\xi }^0)$ assigned lepton number $L=0$, so that the tree-level Yukawa coupling ${\xi }^0{\nu }_i{\nu }_j$ is not allowed. It is generated instead through the interaction of $\xi$ and $\nu$ with dark matter and the soft breaking of $L$ to $(-1{)}^L$. We discuss the phenomenological implications of this model, including ${\xi }^{++}$ decay and the prognosis of discovering the dark sector at the Large Hadron Collider.

We present the results of mechanical characterizations of many different high-quality optical coatings made of ion-beam-sputtered titania-doped tantala and silica, developed originally for interferometric gravitational-wave detectors. Our data show that in multilayer stacks (like high-reflection Bragg mirrors, for example) the measured coating dissipation is systematically higher than the expectation and is correlated with the stress condition in the sample. This has a particular relevance for the noise budget of current advanced gravitational-wave interferometers, and, more generally, for any experiment involving thermal-noise-limited optical cavities.

The Tokai to Kamioka (T2K) long-baseline neutrino experiment consists of a muon neutrino beam, produced at the J-PARC accelerator, a near detector complex and a large 295-km-distant far detector. The present work utilizes the T2K event timing measurements at the near and far detectors to study neutrino time of flight as a function of derived neutrino energy. Under the assumption of a relativistic relation between energy and time of flight, constraints on the neutrino rest mass can be derived. The sub-GeV neutrino beam in conjunction with timing precision of order tens of ns provide sensitivity to neutrino mass in the few $\mathrm{MeV}/c^2$ range. We study the distribution of relative arrival times of muon and electron neutrino candidate events at the T2K far detector as a function of neutrino energy. The 90% C.L. upper limit on the mixture of neutrino mass eigenstates represented in the data sample is found to be $m_{\nu }^2<5.6{\mathrm{MeV}}^2/c^4$.

In the context of results presented in [S. A. Hojman and F. A. Asenjo, Classical Quantum Gravity 30, 025008 (2013)], we discuss different formulations of equations which are used to describe motions of a spinning test body (particle) in general relativity. The specific features of the spin-gravity interaction for highly relativistic spinning particles in Schwarzschild’s background according to the Mathisson-Papapetrou equations are stressed.

We exhibit difficulties of different sorts which appear when using the Mathisson-Papapetrou equations, in particular in the description of highly relativistic particles presented in R. Plyatsko and M. Fenyk [Phys. Rev. D 91, 064033 (2015)]. We compare some results of this theory and of the aforementioned work with the ones obtained using a Lagrangian formulation for massive spinning particles and show that the issues mentioned in the preceding sentence do not appear in the Lagrangian treatment.

As originally described by Rubakov, particles are produced during the tunneling of a metastable quantum field. We propose to extend his formalism to compute the backreaction of these particles on the semiclassical decay probability of the field. The idea is to integrate out the external bath of particles by computing the reduced density matrix of the system. Following this approach, we derive an explicit correction factor in the specific case of scalar particle production in flat spacetime. In this given framework, we conclude that the backreaction is ultraviolet finite and enhances the decay rate. Moreover, in the weak production limit, the backreaction factor is directly given by one half of the total number of created particles. In order to estimate the importance of this correction, we apply our formalism to a toy model potential which allows us to consider both the decay of a homogeneous bounce and the nucleation of a thin-wall bubble. In the former case, the impact of the created particles is parameter dependent and we exhibit a reasonable choice of variables for which ones the backreaction is significant. In the latter case, we conclude that the backreaction is always negligible.

We show that supercritically charged black holes with a Newman–Unti–Tamburino (NUT) parameter provide a new setting for traversable wormholes. This does not require exotic matter, but there is a price—the Misner string singularities. Without assuming time periodicity to make Misner strings unobservable, we show that, contrary to expectations, geodesics do not stop there. Moreover, since there is no central singularity, the spacetime turns out to be geodesically complete. Another unpleasant feature of spacetimes with NUTs is the presence of regions where the azimuthal angle $\phi$ becomes timelike, signalling the appearance of closed timelike curves (CTCs). We show that among them there are no closed timelike or null geodesics, so the freely falling observers should not encounter causality violations. Considering worldlines of charged particles, we find that, although these can become closed in the vicinity of the wormhole throat for large enough charge-to-mass ratio, the noncausal orbits are still disconnected from the distant zones. Integrating the geodesic equations completely, we demonstrate the existence of timelike and null geodesics connecting two asymptotic regions of the wormhole, such that the tidal forces in the throat are reasonably small. We also discuss bounds on the NUT charge which follow from the Schwinger pair creation and ionization thresholds.

Scattering data can be generically described in terms of monodromies. Here we obtain scattering amplitudes for conformally coupled scalar fields in Kerr–de Sitter black holes using this monodromy technique. The only nontrivial parameter, the composite monodromy parameter ${\sigma }_{ij}$ between two regular singular points, can be solved implicitly in terms of the Painlevé VI $\tau$ function. The application of the Virasoro conformal blocks to solve the latter can now be interpreted as a verification of the striking relationship between conformal symmetry and black holes.

In this work, we analyze the necessary conditions for a nonlinear anti–de Sitter (AdS)-type instability in the gravity-scalar field system. In particular, we discuss the necessary conditions for a cascade of energy to higher modes by applying results in Kolmogorov-Arnold-Moser theory. Our analytical framework explains numerical observations of instability of spacetimes even when the spectrum is only asymptotically resonant, and the fact that a minimum field amplitude is needed to trigger it. Our framework can be applied for similar stability analyses of fields in (locally) asymptotically AdS spacetimes. We illustrate this with the example of the AdS soliton. Further, we conjecture on the possible reasons for quasiperiodic behavior observed in perturbations of AdS spacetime. Certain properties of the eigenfunctions of the linear system dictate whether there will be localization in space leading to black hole formation. These properties are examined using the asymptotics of Jacobi polynomials. Finally we discuss recent results on the AdS instability in Einstein-Gauss-Bonnet gravity in light of our work.

We investigate the stability of a free scalar field nonminimally coupled to gravity under linear perturbations in the spacetime of a charged spherical shell. Our analysis is performed in the context of quantum field theory in curved spacetimes. This paper completes previous analyses which considered the exponential enhancement of vacuum fluctuations in the spacetime of massive shells.

Within a cosmological context, we study the behavior of collisionless particles in the weak-field approximation to general relativity, allowing for large gradients of the fields and relativistic velocities for the particles. We consider a spherically symmetric setup such that high resolution simulations are possible with minimal computational resources. We test our formalism by comparing it to two exact solutions: the Schwarzschild solution and the Lemaître-Tolman-Bondi model. In order to make the comparison we consider redshifts and lensing angles of photons passing through the simulation. These are both observable quantities and hence are gauge independent. We demonstrate that our scheme is more accurate than a Newtonian scheme, correctly reproducing the leading-order post-Newtonian correction. In addition, our setup is able to handle shell crossings, which is not possible within a fluid model. Furthermore, by introducing angular momentum, we find configurations corresponding to bound objects which may prove useful for numerical studies of the effects of modified gravity, dynamical dark energy models or even compact bound objects within general relativity.

We derive a general expression for the probability of observing deviations from statistical isotropy in the cosmic microwave background (CMB) if the primordial fluctuations are non-Gaussian and extend to superhorizon scales. The primary motivation is to properly characterize the monopole and dipole modulations of the primordial power spectrum that are generated by the coupling between superhorizon and subhorizon perturbations. Unlike previous proposals for generating the hemispherical power asymmetry, we do not assume that the power asymmetry results from a single large superhorizon mode. Instead, we extrapolate the observed power spectrum to superhorizon scales and compute the power asymmetry that would result from a specific realization of non-Gaussian perturbations on scales larger than the observable universe. Our study encompasses many of the scenarios that have been put forward as possible explanations for the CMB hemispherical power asymmetry. We confirm our analytic predictions for the probability of a given power asymmetry by comparing them to numerical realizations of CMB maps. We find that nonlocal models of non-Gaussianity and scale-dependent local non-Gaussianity produce scale-dependent modulations of the power spectrum, thereby potentially producing both a monopolar and a dipolar power modulation on large scales. We then provide simple examples of finding the posterior distributions for the parameters of the bispectrum from the observed monopole and dipole modulations.

The analyticity of response functions and scattering amplitudes implies powerful relations between low-energy observables and the underlying short-distance dynamics. These “IR/UV” relations are rooted in basic physical principles, such as causality and unitarity. In this paper, we seek similar connections in inflation, relating cosmological observations to the physics responsible for the accelerated expansion. We assume that the inflationary theory is Lorentz invariant at short distances, but allow for nonrelativistic interactions and a nontrivial speed of propagation at low energies. Focusing on forward scattering, we derive a “sum rule” which equates a combination of low-energy parameters to an integral which is sensitive to the high-energy behavior of the theory. While for relativistic amplitudes unitarity is sufficient to prove positivity of the sum rule, this is not guaranteed in the nonrelativistic case. We discuss the conditions under which positivity still applies, and show that they are satisfied by all known UV completions of single-field inflation. In that case, we obtain a consistency condition for primordial non-Gaussianity, which constrains the size and the sign of the equilateral four-point function in terms of the amplitude of the three-point function. The resulting bound rules out about half of the parameter space that is still allowed by current observations. Finding a violation of our consistency condition would point toward less conventional theories of inflation, or violations of basic physical principles.