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.

A surprising connection between the weak gravity conjecture and cosmic censorship has recently been proposed. In particular, it was argued that a promising class of counterexamples to cosmic censorship in four-dimensional Einstein-Maxwell-$\mathrm{\Lambda }$ theory would be removed if charged particles (with sufficient charge) were present. We test this idea and find that indeed if the weak gravity conjecture is true, one cannot violate cosmic censorship this way. Remarkably, the minimum value of charge required to preserve cosmic censorship appears to agree precisely with that proposed by the weak gravity conjecture.

We derive updated constraints on the integrated Sachs-Wolfe (ISW) effect through cross-correlation of the cosmic microwave background with galaxy surveys. We improve with respect to similar previous analyses in several ways. First, we use the most recent versions of extragalactic object catalogs, SDSS DR12 photometric redshift (photo-$z$) and 2MASS Photo-$z$ data sets, as well as those employed earlier for ISW, SDSS QSO photo-$z$ and NVSS samples. Second, we use for the first time the WISE $\times$ SuperCOSMOS catalog, which allows us to perform an all-sky analysis of the ISW up to $z\sim 0.4$. Third, thanks to the use of photo-$z\mathrm{s}$, we separate each data set into different redshift bins, deriving the cross-correlation in each bin. This last step leads to a significant improvement in sensitivity. We remove cross-correlation between catalogs using masks which mutually exclude common regions of the sky. We use two methods to quantify the significance of the ISW effect. In the first one, we fix the cosmological model, derive linear galaxy biases of the catalogs, and then evaluate the significance of the ISW using a single parameter. In the second approach we perform a global fit of the ISW and of the galaxy biases varying the cosmological model. We find significances of the ISW in the range $4.7–5.0\sigma$ thus reaching, for the first time in such an analysis, the threshold of $5\sigma$. Without the redshift tomography we find a significance of $\sim 4.0\sigma$, which shows the importance of the binning method. Finally we use the ISW data to infer constraints on the dark energy redshift evolution and equation of state. We find that the redshift range covered by the catalogs is still not optimal to derive strong constraints, although this goal will be likely reached using future datasets such as from Euclid, LSST, and SKA.

We investigate whether the classical equivalence of $f(R)$ gravity and its formulation as scalar-tensor theory still holds at the quantum level. We explicitly compare the corresponding one-loop divergences and find that the equivalence is broken by off-shell quantum corrections, but recovered on shell.

We calculate the divergent part of the one-loop effective action for $f(R)$ gravity on an arbitrary background manifold. Our result generalizes previous results for quantum corrections in $f(R)$ gravity, which have been limited to spaces of constant curvature. We discuss a new technical aspect connected to operators with degenerate principal symbol. Our result has important applications in cosmology and allows us to study the quantum equivalence between $f(R)$ theories and scalar-tensor theories.

Using a 10D lift of nonperturbative volume stabilization in type IIB string theory, we study the limitations for obtaining de Sitter vacua. Based on this we find that the simplest Kachru, Kallosh, Linde, and Trivedi vacua with a single Kähler modulus stabilized by a gaugino condensate cannot be uplifted to de Sitter. Rather, the uplift flattens out due to stronger backreaction on the volume modulus than has previously been anticipated, resulting in vacua which are metastable and supersymmetry breaking, but that are always anti-de Sitter (AdS). However, we also show that setups such as racetrack stabilization can avoid this issue. In these models it is possible to obtain supersymmetric AdS vacua with a cosmological constant that can be tuned to zero while retaining finite moduli stabilization. In this regime, it seems that de Sitter uplifts are possible with negligible backreaction on the internal volume. We exhibit this behavior also from the 10D perspective.