We investigate the question whether Lipatov’s high energy effective action is capable of reproducing quark and gluon propagators that resum the interaction with a strong background field within high energy factorization. Such propagators are frequently employed in calculations within the color glass condensate formalism, in particular when considering scattering of a dilute projectile on a dense target nucleus or nucleon. We find that such propagators can be obtained from the high energy effective action, if a special parametrization of the gluonic field is used, first proposed by Lipatov in the original publication on the high energy effective action. The obtained propagators are used to rederive from the high energy effective action the leading order Balitsky, Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov, Kovner evolution equation in covariant gauge. As an aside, our result confirms the definition of the Reggeized gluon as the logarithm of an adjoint Wilson line, proposed in the literature.

This work presents a complete reevaluation of the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{had},\mathrm{VP}}$, and the hadronic contributions to the effective QED coupling at the mass of the $Z$ boson, $\mathrm{\Delta }{\alpha }_{\mathrm{had}}(M_Z^2)$, from the combination of $e^{+}{e}^{-}\to \text{hadrons}$ cross section data. Focus has been placed on the development of a new data combination method, which fully incorporates all correlated statistical and systematic uncertainties in a bias free approach. All available $e^{+}{e}^{-}\to \text{hadrons}$ cross section data have been analyzed and included, where the new data compilation has yielded the full hadronic $R$-ratio and its covariance matrix in the energy range $m_{\pi }\le \sqrt{s}\le 11.2\mathrm{GeV}$. Using these combined data and perturbative QCD above that range results in estimates of the hadronic vacuum polarization contributions to $g-2$ of the muon of $a_{\mu }^{\mathrm{had},\mathrm{LO}\mathrm{VP}}=(693.26\pm 2.46)\times {10}^{-10}$ and $a_{\mu }^{\mathrm{had},\mathrm{NLO}\mathrm{VP}}=(-9.82\pm 0.04)\times {10}^{-10}$. The new estimate for the Standard Model prediction is found to be $a_{\mu }^{\mathrm{SM}}=(11659182.04\pm 3.56)\times {10}^{-10}$, which is $3.7\sigma$ below the current experimental measurement. The prediction for the five-flavor hadronic contribution to the QED coupling at the $Z$ boson mass is $\mathrm{\Delta }{\alpha }_{\mathrm{had}}^{(5)}(M_Z^2)=(276.11\pm 1.11)\times {10}^{-4}$, resulting in ${\alpha }^{-1}(M_Z^2)=128.946\pm 0.015$. Detailed comparisons with results from similar related works are given.

The self-force problem—which asks how self-interaction affects a body’s motion—has been poorly studied for spacetime dimensions $d\ne 4$. We remedy this for all $d\ge 3$ by nonperturbatively constructing momenta such that forces and torques acting on extended, self-interacting electromagnetic charges have the same functional forms as their test body counterparts. The electromagnetic field which appears in the resulting laws of motion is not however the physical one, but a certain effective surrogate which we derive. For even $d\ge 4$, explicit momenta are identified such that this surrogate field satisfies the source-free Maxwell equations; laws of motion in these cases can be obtained similarly to those in the well-known four-dimensional Detweiler-Whiting prescription. For odd $d$, no analog of the Detweiler-Whiting prescription exists. Nevertheless, we derive its replacement. These general results are used to obtain explicit point-particle self-forces and self-torques in Minkowski spacetimes with various dimensions. Among various characteristics of the resulting equations, perhaps the most arresting is that an initially stationary charge which is briefly kicked in $2+1$ dimensions asymptotically returns to rest.

We perform a general-relativistic magnetohydrodynamics simulation for $\approx 30\mathrm{ms}$ from the merger of a binary neutron star throughout the formation of a remnant massive neutron star (RMNS) with a high spatial resolution of the finest grid resolution 12.5 m. First, we show that the Kelvin-Helmholtz instability at the merger could amplify the magnetic-field energy at least up to $\sim 1\%$ of the thermal energy. Then, we show that the magnetorotational instability in the RMNS envelope and torus with $\rho <{10}^{13}\mathrm{g}{\mathrm{cm}}^{-3}$ sustains the magnetoturbulent state, and the effective viscous parameter in these regions is likely to converge to $\approx 0.01–0.02$ with respect to the grid resolution. We also point out that the current grid resolution is not still fine enough to sustain a magnetoturbulent state in the RMNS with $\rho \ge {10}^{13}\mathrm{g}{\mathrm{cm}}^{-3}$.

We explore the possibility that dark matter (DM) is the lightest hadron made of two stable color octet Dirac fermions $\mathcal{Q}$. The cosmological DM abundance is reproduced for $M_{\mathcal{Q}}\approx 12.5\mathrm{TeV}$, compatibly with direct searches (the Rayleigh cross section, suppressed by $1/M_{\mathcal{Q}}^6$, is close to present bounds), indirect searches (enhanced by $\mathcal{Q}\mathcal{Q}+\overline{\mathcal{Q}}\overline{\mathcal{Q}}\to \mathcal{Q}\overline{\mathcal{Q}}+\mathcal{Q}\overline{\mathcal{Q}}$ recombination), and with collider searches (where $\mathcal{Q}$ manifests as tracks, pair produced via QCD). Hybrid hadrons, made of $\mathcal{Q}$ and of standard model quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is $10^5$ times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles.

We study the effects of cold dark matter on the propagation of gravitational waves of astrophysical and primordial origin. We show that the dominant effect of cold dark matter on gravitational waves from astrophysical sources is a small frequency dependent modification of the propagation speed of gravitational waves. However, the magnitude of the effect is too small to be detected in the near future. We furthermore show that the spectrum of primordial gravitational waves in principle contains detailed information about the properties of dark matter. However, depending on the wavelength, the effects are either suppressed because the dark matter is highly nonrelativistic or because it contributes a small fraction of the energy density of the universe. As a consequence, the effects of cold dark matter on primordial gravitational waves in practice also appear too small to be detectable.

We model the expansion history of the Universe as a Gaussian process and find constraints on the dark energy density and its low-redshift evolution using distances inferred from the Luminous Red Galaxy and Lyman-alpha data sets of the Baryon Oscillation Spectroscopic Survey, supernova data from the Joint Light-Curve Analysis sample, cosmic microwave background data from the Planck satellite, and local measurement of the Hubble parameter from the Hubble Space Telescope ($\mathsf{H}0$). Our analysis shows that the cosmic microwave background, Luminous Red Galaxy, Lyman-alpha, and Joint Light-Curve Analysis data are consistent with each other and with a $\mathrm{\Lambda }\mathrm{CDM}$ cosmology, but the $\mathsf{H}0$ data are inconsistent at moderate significance. Including the presence of dark radiation does not alleviate the $\mathsf{H}0$ tension in our analysis. While some of these results have been noted previously, the strength here lies in that we do not assume a particular cosmological model. We calculate the growth of the gravitational potential in General Relativity corresponding to these general expansion histories and show that they are well approximated by ${\mathrm{\Omega }}_{\mathrm{m}}^{0.55}$ given the current precision. We assess the prospects for upcoming surveys to measure deviations from $\mathrm{\Lambda }\mathrm{CDM}$ using this model-independent approach.

In this work we present the first calculation of the gravitational self-force on generic bound geodesics in Kerr spacetime to first order in the mass ratio. That is, the local correction to equations of motion for a compact object orbiting a larger rotating black hole due to its own impact on the gravitational field. This includes both dissipative and conservative effects. Our method builds on and extends earlier methods for calculating the gravitational self-force on equatorial orbits. In particular we reconstruct the local metric perturbation in the outgoing radiation gauge from the Weyl scalar ${\psi }_4$, which in turn is obtained by solving the Teukolsky equation using semianalytical frequency domain methods. The gravitational self-force is subsequently obtained using (spherical) $l$-mode regularization. We test our implementation by comparing the large $l$-behavior against the analytically known regularization parameters. In addition we validate our results by comparing the long-term average changes to the energy, angular momentum, and Carter constant to changes to these constants of motion inferred from the gravitational wave flux to infinity and down the horizon.

We show that, in the saturation/color glass condensate framework, odd azimuthal harmonics of the two-gluon correlation function with a long-range separation in rapidity are generated by the higher-order saturation corrections in the interactions with the projectile and the target. At the very least, the odd harmonics require three scatterings in the projectile and three scatterings in the target. We derive the leading-order expression for the two-gluon production cross section which generates odd harmonics: the expression includes all-order interactions with the target and three interactions with the projectile. We evaluate the obtained expression both analytically and numerically, confirming that the odd-harmonics contribution to the two-gluon production in the saturation framework is nonzero.

Upcoming cosmic microwave background (CMB) surveys will soon make the first detection of the polarized Sunyaev-Zel’dovich effect, the linear polarization generated by the scattering of CMB photons on the free electrons present in collapsed objects. Measurement of this polarization along with knowledge of the electron density of the objects allows a determination of the quadrupolar temperature anisotropy of the CMB as viewed from the space-time location of the objects. Maps of these remote temperature quadrupoles have several cosmological applications. Here we propose a new application: the reconstruction of the cosmological reionization history. We show that with quadrupole measurements out to redshift 3, constraints on the mean optical depth can be improved by an order of magnitude beyond the CMB cosmic variance limit.

Recent measurements of reactor-produced antineutrino fluxes and energy spectra are inconsistent with models based on measured thermal fission beta spectra. In this paper, we examine the dependence of antineutrino production on fission neutron energy. In particular, the variation of fission product yields with neutron energy has been considered as a possible source of the discrepancies between antineutrino observations and models. In simulations of low-enriched and highly-enriched reactor core designs, we find a substantial fraction of fissions (from 5% to more than 40%) are caused by nonthermal neutrons. Using tabulated evaluations of nuclear fission and decay, we estimate the variation in antineutrino emission by the prominent fission parents ${}^{235}\mathrm{U}$, ${}^{239}\mathrm{Pu}$, and ${}^{241}\mathrm{Pu}$ versus neutron energy. The differences in fission neutron energy are found to produce less than 1% variation in detected antineutrino rate per fission of ${}^{235}\mathrm{U}$, ${}^{239}\mathrm{Pu}$, and ${}^{241}\mathrm{Pu}$. Corresponding variations in the antineutrino spectrum are found to be less than 10% below 7 MeV antineutrino energy, smaller than current model uncertainties. We conclude that insufficient modeling of fission neutron energy is unlikely to be the cause of the various reactor anomalies. Our results also suggest that comparisons of antineutrino measurements at low-enriched and highly-enriched reactors can safely neglect the differences in the distributions of their fission neutron energies.

The ratio of branching fractions $\mathcal{R}(D^{*-})\equiv \mathcal{B}(B^0\to D^{*-}{\tau }^{+}{\nu }_{\tau })/\mathcal{B}(B^0\to D^{*-}{\mu }^{+}{\nu }_{\mu })$ is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$. The $\tau$ lepton is reconstructed with three charged pions in the final state. A novel method is used that exploits the different vertex topologies of signal and backgrounds to isolate samples of semitauonic decays of $b$ hadrons with high purity. Using the $B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+}$ decay as the normalization channel, the ratio $\mathcal{B}(B^0\to D^{*-}{\tau }^{+}{\nu }_{\tau })/\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+})$ is measured to be $1.97\pm 0.13\pm 0.18$, where the first uncertainty is statistical and the second systematic. An average of branching fraction measurements for the normalization channel is used to derive $\mathcal{B}(B^0\to D^{*-}{\tau }^{+}{\nu }_{\tau })=(1.42\pm 0.094\pm 0.129\pm 0.054)\%$, where the third uncertainty is due to the limited knowledge of $\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+})$. A test of lepton flavor universality is performed using the well-measured branching fraction $\mathcal{B}(B^0\to D^{*-}{\mu }^{+}{\nu }_{\mu })$ to compute $\mathcal{R}(D^{*-})=0.291\pm 0.019\pm 0.026\pm 0.013$, where the third uncertainty originates from the uncertainties on $\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+})$ and $\mathcal{B}(B^0\to D^{*-}{\mu }^{+}{\nu }_{\mu })$. This measurement is in agreement with the Standard Model prediction and with previous measurements.

The behavior of quasilocal black hole horizons in a binary black hole merger is studied numerically. We compute the horizon multipole moments, fluxes, and other quantities on black hole horizons throughout the merger. These lead to a better qualitative and quantitative understanding of the coalescence of two black holes: how the final black hole is formed, initially grows, and then settles down to a Kerr black hole. We calculate the rate at which the final black hole approaches equilibrium in a fully nonperturbative situation and identify a time at which the linear ringdown phase begins. Finally, we provide additional support for the conjecture that fields at the horizon are correlated with fields in the wave zone by comparing the in-falling gravitational wave flux at the horizon to the outgoing flux as estimated from the gravitational waveform.

A search for massive neutrinos has been made in the decay ${\pi }^{+}\to {\mathrm{e}}^{+}\nu$. No evidence was found for extra peaks in the positron energy spectrum indicative of pion decays involving massive neutrinos ($\pi \to e^{+}{\nu }_h$). Upper limits (90% C.L.) on the neutrino mixing matrix element $|U_{ei}{|}^2$ in the neutrino mass region $60–135\mathrm{MeV}/c^2$ were set and are an order of magnitude improvement over previous results.

We derive soft theorems for single-clock cosmologies that enjoy a shift symmetry. These so-called consistency conditions arise from a combination of a large diffeomorphism and the internal shift symmetry and fix the squeezed limit of all correlators with a soft scalar mode. As an application, we show that our results reproduce the squeezed bispectrum for ultra-slow-roll inflation, a particular shift-symmetric, nonattractor model which is known to violate Maldacena’s consistency relation. Similar results have been previously obtained by Mooij and Palma using background-wave methods. Our results shed new light on the infrared structure of single-clock cosmological spacetimes.

We present the first lattice QCD study of coupled isoscalar $\pi \pi ,K\overline{K},\eta \eta S$- and $D$-wave scattering extracted from discrete finite-volume spectra computed on lattices which have a value of the light quark mass corresponding to $m_{\pi }\sim 391\mathrm{MeV}$. In the $J^P=0^{+}$ sector we find analogues of the experimental $\sigma$ and $f_0(980)$ states, where the $\sigma$ appears as a stable bound-state below $\pi \pi$ threshold, and, similar to what is seen in experiment, the $f_0(980)$ manifests itself as a dip in the $\pi \pi$ cross section in the vicinity of the $K\overline{K}$ threshold. For $J^P=2^{+}$ we find two states resembling the $f_2(1270)$ and $f_2^{\prime }(1525)$, observed as narrow peaks, with the lighter state dominantly decaying to $\pi \pi$ and the heavier state to $K\overline{K}$. The presence of all these states is determined rigorously by finding the pole singularity content of scattering amplitudes, and their couplings to decay channels are established using the residues of the poles.

We describe an experimental search for deviations from the inverse-square law of gravity at the nanometer length scale using neutron scattering from noble gases on a pulsed slow neutron beam line. By measuring the neutron momentum transfer ($q$) dependence of the differential cross section for xenon and helium and comparing to their well-known analytical forms, we place an upper bound on the strength of a new interaction as a function of interaction length $\lambda$ which improves upon previous results in the region $\lambda <0.1\mathrm{nm}$, and remains competitive in the larger-$\lambda$ region. A pseudoexperimental simulation is developed for this experiment and its role in the data analysis is described. We conclude with plans for improving sensitivity in the larger-$\lambda$ region.

In this study, we revisit and complete the full next-to-leading order corrections to pseudoscalar double-Dalitz decays within the soft-photon approximation. Comparing to the previous study, we find small differences, which are nevertheless relevant for extracting information about the pseudoscalar transition form factors. Concerning the latter, these processes could offer the opportunity to test them—for the first time—in their double-virtual regime.

We stack maps of the thermal Sunyaev-Zel’dovich effect produced by the Planck Collaboration around the centers of cosmic voids defined by the distribution of galaxies in the CMASS sample of the Baryon Oscillation Spectroscopic Survey, scaled by the void effective radii. We report a first detection of the associated cross-correlation at the $3.4\sigma$ level: voids are under-pressured relative to the cosmic mean. We compare the measured Compton-$y$ profile around voids with a model based solely on the spatial modulation of halo abundance with environmental density. The amplitude of the detected signal is marginally lower than predicted by an overall amplitude ${\alpha }_v=0.67\pm 0.2$. We discuss the possible interpretations of this measurement in terms of modeling uncertainties, excess pressure in low-mass halos, or nonlocal heating mechanisms.

In a classically scale-invariant quantum field theory, tunneling rates are infrared divergent due to the existence of instantons of any size. While one expects such divergences to be resolved by quantum effects, it has been unclear how higher-loop corrections can resolve a problem appearing already at one loop. With a careful power counting, we uncover a series of loop contributions that dominate over the one-loop result and sum all the necessary terms. We also clarify previously incomplete treatments of related issues pertaining to global symmetries, gauge fixing, and finite mass effects. In addition, we produce exact closed-form solutions for the functional determinants over scalars, fermions, and vector bosons around the scale-invariant bounce, demonstrating manifest gauge invariance in the vector case. With these problems solved, we produce the first complete calculation of the lifetime of our Universe: $10^{139}\mathrm{years}$. With 95% confidence, we expect our Universe to last more than $10^{58}\mathrm{years}$. The uncertainty is part experimental uncertainty on the top quark mass and on ${\alpha }_s$ and part theory uncertainty from electroweak threshold corrections. Using our complete result, we provide phase diagrams in the $m_t/m_h$ and the $m_t/{\alpha }_s$ planes, with uncertainty bands. To rule out absolute stability to $3\sigma$ confidence, the uncertainty on the top quark pole mass would have to be pushed below 250 MeV or the uncertainty on ${\alpha }_s(m_Z)$ pushed below 0.00025.