A compact object moving on a quasicircular orbit about a Schwarzschild black hole gradually spirals inward due to the dissipative action of its gravitational self-force. But in addition to driving the inspiral, the self-force has a conservative piece. Within a second-order self-force formalism, I derive a second-order generalization of Detweiler’s redshift variable, which provides a gauge-invariant measure of conservative effects on quasicircular orbits. I sketch a frequency-domain numerical scheme for calculating this quantity. Once this scheme has been implemented, its results may be used to determine high-order terms in post-Newtonian theory and parameters in effective-one-body theory.

We study the quantum conformal gravity whose dynamics is governed by a single dimensionless gravitational coupling with negative beta function. Since the Euler term is not dynamical classically, the constant in front of it is not an independent coupling. Quantum mechanically, however, it induces the Riegert conformal-factor dynamics with Becchi-Rouet-Stora-Tyutin conformal symmetry representing background free nature. In this paper, we propose how to handle the Euler term systematically, incorporating such dynamics on the basis of renormalization group analysis using dimensional regularization. As a nontrivial test of renormalization, we explicitly calculate the three-loop anomalous dimension of the cosmological constant operator and show that it agrees with the exact expression derived using the Becchi-Rouet-Stora-Tyutin conformal symmetry. The physical significance to inflation and the cosmic microwave background is also discussed.

The possibility of sending the LISA Pathfinder spacecraft through the Sun-Earth saddle point following its nominal mission around L1 has now been studied for a few years. The principal motivation for doing so is to search for anomalous gravity gradients predicted by several alternative theories of gravity. In turn, these have originally been motivated by the dark matter problem, and predict deviations from General Relativity in regions of low acceleration. All signal estimates to date have ignored the presence of the spacecraft mass distribution and its self-gravity, on the basis that the gravitational field due to Sun and Earth is larger than that due to the spacecraft itself, for any realistic saddle point fly-by distances. In this paper, we show that at least for one of the theoretical frameworks, Quasilinear MOdified Newtonian Dynamics (QMOND), the presence of the local mass distribution cannot be ignored. Using simplified representations of the spacecraft mass distribution, we demonstrate that internal self-gravity, in particular internal gravitational gradients, can enhance the QMOND signals by more than 3 orders of magnitude. These preliminary results indicate that the parameter space accessible to LISA Pathfinder may be significantly larger than previously thought. We find further that the details of the matter distribution as well as of the trajectory can affect the expected signal shape, due to the coupling between internal and external gravitational fields and field gradients. We hope that this work will motivate a more comprehensive investigation of the effect, not just in QMOND, but also in the context of other theoretical frameworks.

We investigate the phase space dynamics of a bulk viscosity model in the Eckart approach for a spatially flat Friedmann-Robertson-Walker universe. We have included two barotropic fluids and a dark energy component. One of the barotropic fluids is treated as an imperfect fluid having bulk viscosity, whereas the other components are assumed to behave as perfect fluids. Both barotropic fluids are identified as either radiation or dark matter. Considering that the bulk viscosity acts on either radiation or dark matter, we find that viscous phantom solutions with stable behavior are not allowed in the framework of complete cosmological dynamics. Only an almost zero value of the bulk viscosity allows a transition from a radiation-dominated to a matter-dominated epoch, which then evolves to an accelerated late time expansion, dominated by dark energy.

We consider a simple extension of the type-II two-Higgs-doublet model by introducing a real scalar as a candidate for dark matter in the present Universe. The main annihilation mode of the dark matter particle with a mass of around 31–40 GeV is into a $b\overline{b}$ pair, and this annihilation mode suitably explains the observed excess of the gamma-ray flux from the Galactic Center. We identify the parameter region of the model that can fit the gamma-ray excess and satisfy phenomenological constraints, such as the observed dark matter relic density and the null results of direct dark matter search experiments. Most of the parameter region is found to be within the search reach of future direct dark matter detection experiments.

Recent B-mode polarization observation seems to imply the tensor tilt $n_T\gtrsim 1$ at large angular scale if the primordial signal is dominated. We show that for a primordial universe, which is in a slowly expanding genesis phase before the slow-roll inflation, the primordial tensor spectrum will get a large-scale cutoff, i.e., $n_T\gtrsim 1$ at large scales while $n_T\simeq 0$ at small scale. We find that this inflationary scenario not only may be consistent with the observation, but also predicts a large-scale anomaly in BB power spectrum, i.e., due to the large suppression of tensor perturbation amplitude we will hardly see the reionization bump at low-$l$, which may be falsified by the Planck polarization data.

We study the effect of spins on searches for gravitational waves from compact binary coalescences in realistic simulated early advanced LIGO data. We construct a detection pipeline including matched filtering, signal-based vetoes, a coincidence test between different detectors, and an estimate of the rate of background events. We restrict attention to neutron star-black hole (NS-BH) binary systems, and we compare a search using nonspinning templates to one using templates that include spins aligned with the orbital angular momentum. To run the searches we implement the binary inspiral matched-filter computation in PyCBC, a new software toolkit for gravitational-wave data analysis. We find that the inclusion of aligned-spin effects significantly increases the astrophysical reach of the search. Considering astrophysical NS-BH systems with nonprecessing black hole spins, for dimensionless spin components along the orbital angular momentum uniformly distributed in $(-1,1)$, the sensitive volume of the search with aligned-spin templates is increased by $\sim 50\%$ compared to the nonspinning search; for signals with aligned spins uniformly distributed in the range (0.7,1), the increase in sensitive volume is a factor of $\sim 10$.

The prospects are explored for testing Lorentz and $CPT$ symmetry in the muon sector via the spectroscopy of muonium and various muonic atoms, and via measurements of the anomalous magnetic moments of the muon and antimuon. The effects of Lorentz-violating operators of both renormalizable and nonrenormalizable dimensions are included. We derive observable signals, extract first constraints from existing data on a variety of coefficients for Lorentz and $CPT$ violation, and estimate sensitivities attainable in forthcoming experiments. The potential of Lorentz violation to resolve the proton radius puzzle and the muon anomaly discrepancy is discussed.

Double logarithms of $Q^2/m_c^2$ that appear in the cross section for $e^{+}{e}^{-}\to J/\psi +{\eta }_c$ at next-to-leading order (NLO) in the strong coupling ${\alpha }_s$ account for the bulk of the NLO correction at $B$-factory energies. (Here, $Q^2$ is the square of the center-of-momentum energy, and $m_c$ is the charm-quark mass.) We analyze the double logarithms that appear in the contribution of each NLO Feynman diagram, and we find that the double logarithms arise from both the Sudakov and the end-point regions of the loop integration. The Sudakov double logarithms cancel in the sum over all diagrams. We show that the end-point region of integration can be interpreted as a pinch-singular region in which a spectator fermion line becomes soft or soft and collinear to a produced meson. This interpretation may be important in establishing factorization theorems for helicity-flip processes, such as $e^{+}{e}^{-}\to J/\psi +{\eta }_c$, and in resumming logarithms of $Q^2/m_c^2$ to all orders in ${\alpha }_s$.

Based on a viscous hydrodynamic model with anisotropically perturbed Gubser flow and isothermal Cooper-Frye freeze-out at early times, we analytically compute the flow harmonics $v_n(p_T)$ and study how they scale with the harmonic number $n$ and transverse momentum, as well as the system size, shear, and bulk viscosity coefficients, and collision energy. In particular, we find that the magnitude of shear viscous corrections grows linearly with $n$. The mixing between different harmonics is also discussed. While this model is rather simple as compared to realistic heavy-ion collisions, we argue that the scaling results presented here may be meaningfully compared to experimental data collected over many energies, system sizes, and geometries.

We investigate the constraints that the LHC can set on a 126 GeV Higgs boson that is an admixture of $CP$ eigenstates. Traditional analyses rely on Higgs couplings to massive vector bosons, which are suppressed for $CP$-odd couplings, so that these analyses have limited sensitivity. Instead we focus on Higgs production in gluon fusion, which occurs at the same order in ${\alpha }_S$ for both $CP$-even and -odd Higgs couplings to top quarks. We study the Higgs plus two jet final state followed by Higgs decay into a pair of tau leptons. We show that using the 8 TeV data set it is possible to rule out the pure $CP$-odd hypothesis in this channel alone at nearly 95% C.L, assuming that the Higgs is $CP$-even. We also provide projected limits for the 14 TeV LHC run.

We report a search for charmless hadronic decays of neutral $B$ mesons to ${\eta }^{\prime }{K}^{*}(892{)}^0$. The results are based on a $711{\mathrm{fb}}^{-1}$ data sample that contains $772\times {10}^{6}B\overline{B}$ pairs, collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction $\mathcal{B}[B^0\to {\eta }^{\prime }{K}^{*}(892{)}^0]=[2.6\pm 0.7(\text{stat})\pm 0.2(\text{syst})]\times {10}^{-6}$. We also measure the $CP$-violating asymmetry as ${\mathcal{A}}_{CP}[B^0\to {\eta }^{\prime }{K}^{*}(892{)}^0]=-0.22\pm 0.29(\text{stat})\pm 0.07(\text{syst})$.

We use the holographic approach to compare the Hall viscosity ${\eta }_H$ and the angular momentum density $\mathcal{J}$ in gapless systems in $2+1$ dimensions at finite temperature. We start with a conformal fixed point and turn on a perturbation which breaks the parity and time-reversal symmetries via gauge and gravitational Chern-Simons couplings in the bulk. While the ratio of ${\eta }_H$ and $\mathcal{J}$ shows some universal properties when the perturbation is slightly relevant, we find that the two quantities behave differently in general. In particular, ${\eta }_H$ depends only on infrared physics, while $\mathcal{J}$ receives contributions from degrees of freedom at all scales.

During big bang nucleosynthesis, any injection of extra neutrons around the time of the ${}^7\mathrm{Be}$ formation, i.e. at a temperature of order $T\simeq 50\mathrm{keV}$, can reduce the predicted freeze-out amount of ${}^7\mathrm{Be}+{}^7\mathrm{Li}$ that otherwise remains in sharp contradiction with the Spite plateau value inferred from the observations of Pop II stars. However, the growing confidence in the primordial $\mathrm{D}/\mathrm{H}$ determinations puts a strong constraint on any such scenario. We address this issue in detail, analyzing different temporal patterns of neutron injection, such as decay, annihilation, resonant annihilation, and oscillation between mirror and standard model world neutrons. For this latter case, we derive the realistic injection pattern taking into account thermal effects (damping and refraction) in the primordial plasma. If the extra-neutron supply is the sole nonstandard mechanism operating during the big bang nucleosynthesis, the suppression of lithium abundance below $\mathrm{Li}/\mathrm{H}\le 1.9\times 10^{-10}$ always leads to the overproduction of deuterium, $\mathrm{D}/\mathrm{H}\ge 3.6\times 10^{-5}$, well outside the error bars suggested by recent observations.

Theoretical predictions for the cosmic antiproton spectrum currently fall short of the corresponding experimental level of accuracy. Among the main sources of uncertainty are the antiproton production cross sections in cosmic ray inelastic interactions. We analyze existing data on antiproton production in $pp$ scattering, including for the first time the measurements performed by the NA49 Collaboration. We compute the antiproton spectrum finding that in the energy range where data are available (antiproton energies of about 4–550 GeV) different approaches lead to almost equivalent results, with an uncertainty of 10%–20%. Extrapolations outside this region lead to different estimates, with the uncertainties reaching the 50% level around 1 TeV, degrading the diagnostic power of the antiproton channel at those energies. We also comment on the uncertainties in the antiproton production source term coming from nuclei heavier than protons and from neutrons produced in $pp$ scatterings, and point out the need for dedicated experimental campaigns for all processes involving antiproton production in collisions of light nuclei.

Cachazo and Strominger recently proposed an extension of the soft-graviton theorem found by Weinberg. In addition, they proved the validity of their extension at tree level. This was motivated by a Virasoro symmetry of the gravity $S$-matrix related to Bondi, van der Burg, Metzner, and Sachs symmetry. As shown long ago by Weinberg, the leading behavior is not corrected by loops. In contrast, we show that with the standard definition of soft limits in dimensional regularization, the subleading behavior is anomalous and modified by loop effects. We argue that there are no new types of corrections to the first subleading behavior beyond one loop and to the second subleading behavior beyond two loops. To facilitate our investigation, we introduce a new momentum-conservation prescription for defining the subleading terms of the soft limit. We discuss the loop-level subleading soft behavior of gauge-theory amplitudes before turning to gravity amplitudes.

We study flat space cosmologies in two dimensions by taking the flat space limit of the Achúcarro-Ortiz model. We unravel a phase transition between hot flat space and flat space cosmologies, and derive a new dilaton-dependent counterterm required for the consistency of the Euclidean partition function. Our results generalize to asymptotically mass-dominated two-dimensional dilaton gravity models, whose thermodynamical properties we discuss. The novel case of asymptotic mass domination is covered neither by the comprehensive discussion of Grumiller and McNees [J. High Energy Phys. 04 (2007) 074] nor by the more recent generalization to dilaton gravity with confining $U(1)$ charges in Grumiller et al. [Phys. Rev. D 90, 044032 (2014)].

We employ the recently proposed formalism of the “horizon wave function” to investigate the emergence of a horizon in models of black holes as Bose-Einstein condensates of gravitons. We start from the Klein-Gordon equation for a massless scalar (toy graviton) field coupled to a static matter current. The (spherically symmetric) classical field reproduces the Newtonian potential generated by the matter source, and the corresponding quantum state is given by a coherent superposition of scalar modes with continuous occupation number. Assuming an attractive self-interaction that allows for bound states, one finds that (approximately) only one mode is allowed, and the system can be confined in a region the size of the Schwarzschild radius. This radius is then shown to correspond to a proper horizon, by means of the horizon wave function of the quantum system, with an uncertainty in size naturally related to the expected typical energy of Hawking modes. In particular, this uncertainty decreases for larger black hole mass (with a larger number of light scalar quanta), in agreement with semiclassical expectations, a result which does not hold for a single very massive particle. We finally speculate that a phase transition should occur during the gravitational collapse of a star (ideally represented by a static matter current and Newtonian potential) that leads to a black hole (again ideally represented by the condensate of toy gravitons), and suggest an effective order parameter that could be used to investigate this transition.

We consider the dynamics of the Sorkin-Johnston state for a massless scalar field in two dimensions. We conduct a study of the renormalized stress-tensor by a subtraction procedure, and compare the results with those of the conformal vacuum, with an important contribution from correction term. We find a large trace anomaly and compute backreaction effects to two dimensional (Liouville) gravity. We also find a natural interpretation for the mirror behavior of the Sorkin-Johnston state described in previous works.