Coalescing binary black holes are among the primary science targets for second generation ground-based gravitational wave detectors. Reliable gravitational waveform models are central to detection of such systems and subsequent parameter estimation. This paper performs a comprehensive analysis of the accuracy of recent waveform models for binary black holes with aligned spins, utilizing a new set of 84 high-accuracy numerical relativity simulations. Our analysis covers comparable mass binaries (mass-ratio $1\le q\le 3$), and samples independently both black hole spins up to a dimensionless spin magnitude of 0.9 for equal-mass binaries and 0.85 for unequal mass binaries. Furthermore, we focus on the high-mass regime (total mass $\gtrsim 50M_{\odot }$). The two most recent waveform models considered (PhenomD and SEOBNRv2) both perform very well for signal detection, losing less than 0.5% of the recoverable signal-to-noise ratio $\rho$, except that SEOBNRv2’s efficiency drops slightly for both black hole spins aligned at large magnitude. For parameter estimation, modeling inaccuracies of the SEOBNRv2 model are found to be smaller than systematic uncertainties for moderately strong GW events up to roughly $\rho \lesssim 15$. PhenomD’s modeling errors are found to be smaller than SEOBNRv2’s, and are generally irrelevant for $\rho \lesssim 20$. Both models’ accuracy deteriorates with increased mass ratio, and when at least one black hole spin is large and aligned. The SEOBNRv2 model shows a pronounced disagreement with the numerical relativity simulation in the merger phase, for unequal masses and simultaneously both black hole spins very large and aligned. Two older waveform models (PhenomC and SEOBNRv1) are found to be distinctly less accurate than the more recent PhenomD and SEOBNRv2 models. Finally, we quantify the bias expected from all four waveform models during parameter estimation for several recovered binary parameters: chirp mass, mass ratio, and effective spin.

We investigate the monogamy of holographic $n$-partite information for a system consisting of $n$ disjoint parallel strips with the same width and separation in AdS and AdS black brane geometries. More precisely, we study the sign of this quantity, e.g., for $n=4$, 5, in various dimensions and for different parameters. Our results show that for quantum field theories with holographic duals, the holographic 4-partite information is always positive, and the sign of holographic 5-partite information is found to be negative in the dual strongly coupled $1+1$ dimensional conformal field theory. This latter result indicates that the holographic 4-partite information is monogamous. We also find the critical points corresponding to the possible phase transitions of these quantities.

We develop a gravitational analogue of spin magnetic resonance, called spin gravitational resonance, whereby a gravitational wave interacts with a magnetic field to produce a spin transition. In particular, an external magnetic field separates the energy spin states of a spin-$1/2$ particle, and the presence of the gravitational wave produces a perturbation in the components of the magnetic field orthogonal to the gravitational-wave propagation. In this framework we test Dyson’s conjecture that individual gravitons cannot be detected. Although we find no fundamental laws preventing single gravitons being detected with spin gravitational resonance, we show that it cannot be used in practice, in support of Dyson’s conjecture.

Precision timing of highly stable millisecond pulsars is a promising technique for the detection of very low frequency sources of gravitational waves. In any single pulsar, a stochastic gravitational wave signal appears as an additional source of timing noise that can be absorbed by the noise model, and so it is only by considering the coherent response across a network of pulsars that the signal can be distinguished from other sources of noise. In the limit where there are many gravitational wave sources in the sky, or many pulsars in the array, the signals produce a unique tensor correlation pattern that depends only on the angular separation between each pulsar pair. It is this distinct fingerprint that is used to search for gravitational waves using pulsar timing arrays. Here we consider how the prospects for detection are diminished when the statistical isotropy of the timing array or the gravitational wave signal is broken by having a finite number of pulsars and a finite number of sources. We find the standard tensor-correlation analysis to be remarkably robust, with a mild impact on detectability compared to the isotropic limit. Only when there are very few sources and very few pulsars does the standard analysis begin to fail. Having established that the tensor correlations are a robust signature for detection, we study the use of “sky scrambles” to break the correlations as a way to increase confidence in a detection. This approach is analogous to the use of “time slides” in the analysis of data from ground-based interferometric detectors.

An ungravity-inspired model is employed to examine the astrophysical parameters of white dwarf stars (WDs) using polytropic and degenerate gas approaches. Based on the observed properties such as mass, radius, and luminosity of selected WDs, namely, Sirius B and $\epsilon$ Reticulum, bounds on the characteristic length and scaling dimension of the ungravity (UG) model are estimated. The UG effect on the Chandrasekhar limit for WDs is shown. The UG model is examined in the study of ultramassive WDs, e.g., EUVE J1746-706. The UG-inspired model implies that a new location for some WDs on the Hertzsprung-Russell diagram is found.

We show that the decay of the inflaton field may be incomplete, while nevertheless successfully reheating the Universe and leaving a stable remnant that accounts for the present dark matter abundance. We note, in particular, that since the mass of the inflaton decay products is field dependent, one can construct models, endowed with an appropriate discrete symmetry, where inflaton decay is kinematically forbidden at late times and only occurs during the initial stages of field oscillations after inflation. We show that this is sufficient to ensure the transition to a radiation-dominated era and that inflaton particles typically thermalize in the process. They eventually decouple and freeze out, yielding a thermal dark matter relic. We discuss possible implementations of this generic mechanism within consistent cosmological and particle physics scenarios, for both single-field and hybrid inflation.

Conformal higher spin (CHS) field theory, which is a solid part of recent advanced checks of AdS/CFT correspondence, finds applications in cosmology. The hidden sector of weakly interacting CHS fields suggests a resolution of the hierarchy problem in the model of initial conditions for inflationary cosmology driven by a conformal field theory. These initial conditions are set by thermal garland-type cosmological instantons in the sub-Planckian energy range for the model of CHS fields with a large positive coefficient $\beta$ of the Gauss-Bonnet term in their total conformal anomaly and a large number of their polarizations $\mathbb{N}$. The upper bound of this range $M_P/\sqrt{\beta }$ is shown to be much lower than the gravitational cutoff $M_P/\sqrt{\mathbb{N}}$ which is defined by the requirement of smallness of the perturbatively nonrenormalizable graviton loop contributions. In this way we justify the approximation scheme in which the nonrenormalizable graviton sector is subject to effective field theory under this cutoff, whereas the renormalizable sector of multiple CHS fields is treated beyond perturbation theory and dynamically generates the bound on the inflation scale of the CFT cosmology $M_P/\sqrt{\beta }\ll M_P/\sqrt{\mathbb{N}}$. This confirms recent predictions for the origin of the Starobinsky $R^2$ and Higgs inflation models from the CHS cosmology, which occurs at the energy scale 3 or 4 orders of magnitude below the gravitational cutoff, $\sqrt{\mathbb{N}/\beta }\sim {10}^{-3}–{10}^{-4}$. We also consider cosmological models dominated by fermionic CHS fields with a negative $\beta$ and anomaly free models of infinite towers of CHS fields with $\beta =0$ and briefly discuss the status of unitarity in CHS models.

Dwarf spheroidal galaxies (dSphs) are promising targets for the indirect detection of dark matter through gamma-ray emission due to their proximity, lack of astrophysical backgrounds and high dark matter density. They are often used to place restrictive bounds on the dark matter annihilation cross section. In this paper, we analyze six years of Fermi-LAT gamma-ray data from 19 dSphs that are satellites of the Milky Way, and derive from a stacked analysis of 15 dSphs, robust 95% confidence level lower limits on the dark matter lifetime for several decay channels and dark matter masses between $\sim 1\mathrm{GeV}$ and 10 TeV. Our findings are based on a bin-by-bin maximum likelihood analysis treating the $J$-factor as a nuisance parameter using the Pass 8 event class. Our constraints from this ensemble are among the most stringent and solid in the literature, and competitive with existing ones coming from the extragalactic gamma-ray background, galaxy clusters, AMS-02 cosmic ray data, Super-K and ICECUBE neutrino data, while rather insensitive to systematic uncertainties. In particular, among gamma-ray searches, we improve existing limits for dark matter decaying into $\overline{b}b$ (${\mu }^{+}{\mu }^{-}$) for dark matter masses below $\sim 30(200)\mathrm{GeV}$, demonstrating that dSphs are compelling targets for constraining dark matter decay lifetimes.

We analyze the gravitational dynamics of a classical scalar field coupled to gravity in asymptotically AdS spacetime, which leads to black hole formation on the shortest nonlinear time scale for some initial conditions. We show that the observed collapse cannot be described by the well-known process of a random-phase cascade in the theory of weak turbulence. This implies that the dynamics on this time scale is highly sensitive to the phases of modes. We explore the alternative possibility of a coherent phase cascade and analytically find stationary solutions with completely coherent phases and power-law energy spectra. We show that these power-law spectra lead to diverging geometric backreaction, which is the likely precursor to black hole formation. In $4+1$ dimensions, our stationary solution has the same power-law energy spectrum as the final state right before collapse observed in numerical simulations. We conjecture that our stationary solutions describe the system shortly before collapse in other dimensions, and predict the energy spectrum.

Cosmic inflation is commonly assumed to be driven by quantum fields. Quantum mechanics predicts phenomena such as quantum fluctuations and tunneling of the field. Here, we show an example of a quantum interference effect which goes beyond the semiclassical treatment and which may be of relevance in the early Universe. We study the quantum coherent dynamics for a tilted, periodic potential, which results in genuine quantum oscillations of the inflaton field, analogous to Bloch oscillations in condensed matter and atomic systems. The underlying quantum superpositions are typically very fragile but may persist in the early Universe giving rise to quantum interference phenomena in cosmology.

The production mechanism of a 750 GeV diphoton resonance, either via gluon or photon fusion, can be probed by studying kinematic observables in the diphoton events. We perform a detector study of the two production modes of a hypothetical scalar or tensor diphoton resonance in order to characterize the features of the two scenarios. The nature of the resonance production can be determined from the jet multiplicity, the jet and diphoton rapidities, the rate of central pseudorapidity gaps, or the possible detection of forward protons from elastic photoproduction for events in the signal region. Kinematic distributions for both signals and expected irreducible diphoton background events are provided for comparison along with a study of observables useful for distinguishing the two scenarios at an integrated luminosity of $20{\mathrm{fb}}^{-1}$. We find that decay photons from a 750 GeV scalar resonance have a preference for acceptance in the central detector barrel, while background events are more likely to give accepted photons in the detector end caps. This disfavors the interpretation of the large number of excess events found by the Run-2 CMS diphoton search with one photon detected in the end cap as a wide spin-0 resonance signal. However, one expects more end cap photons in the case of spin-2 resonance.

We propose left-right models based on $SU(3{)}_C\otimes SU(M{)}_L\otimes SU(N{)}_R\otimes U(1{)}_X$ gauge symmetry for $(M,N)=(3,3),(2,3)$, and (3,2) that address the 750 GeV diphoton excess recently reported by the LHC. The fermion contents are minimally introduced, and the generation number must match the fundamental color number in order to cancel anomalies and ensure QCD asymptotic freedom. The diphoton excess arises from the field that breaks the left-right symmetry spontaneously in the first model, while for the other models it emerges as an explicit violation of the left-right symmetry. The neutrino masses, flavor-changing neutral currents, and new boson searches are also discussed.

We present an analytic description of numerical results for the ghost propagator $G(p^2)$ in the minimal Landau gauge on the lattice. The data were produced in the SU(2) case using the largest lattice volumes to date, for $d=2$, 3 and 4 spacetime dimensions. Our proposed form for $G(p^2)$ is derived from the one-loop relation between ghost and gluon propagators, considering a tree-level ghost-gluon vertex and our previously obtained gluon-propagator results [A. Cucchieri et al., Phys. Rev. D 85, 094513 (2012). Although this one-loop expression is not a good description of the data, it leads to a one-parameter fit of our ghost-propagator data with a generally good value of ${\chi }^2/\mathrm{d}.\mathrm{o}.\mathrm{f}.$, comparable to other fitting forms used in the literature. At the same time, we present a simple parametrization of the difference between the lattice data and the one-loop predictions.

We apply the complex Langevin (CL) method to a chiral random matrix theory (ChRMT) at nonzero chemical potential and study the nearest neighbor spacing (NNS) distribution of the Dirac eigenvalues. The NNS distribution is extracted using an unfolding procedure for the Dirac eigenvalues obtained in the CL method. For large quark mass, we find that the NNS distribution obeys the Ginibre ensemble as expected. For small quark mass, the NNS distribution follows the Wigner surmise for the correct convergence case, while it follows the Ginibre ensemble for the wrong convergence case. The Wigner surmise is physically reasonable from the chemical potential independence of the ChRMT. The Ginibre ensemble is known to be favored in a phase-quenched QCD at finite chemical potential. Our result suggests a possibility that the originally universal behavior of the NNS distribution is preserved even in the CL method for the correct convergence case.

We report on a scale determination with gradient-flow techniques on the $N_f=2+1+1$ highly improved staggered quark ensembles generated by the MILC Collaboration. The ensembles include four lattice spacings, ranging from approximately 0.15 to 0.06 fm, and both physical and unphysical values of the quark masses. The scales $\sqrt{t_0}/a$ and $w_0/a$ and their tree-level improvements, $\sqrt{t_{0,\text{imp}}}$ and $w_{0,\text{imp}}$, are computed on each ensemble using Symanzik flow and the cloverleaf definition of the energy density $E$. Using a combination of continuum chiral-perturbation theory and a Taylor-series ansatz for the lattice-spacing and strong-coupling dependence, the results are simultaneously extrapolated to the continuum and interpolated to physical quark masses. We determine the scales $\sqrt{t_0}=0.1416(\genfrac{}{}{0ex}{}{+8}{-5})\mathrm{fm}$ and $w_0=0.1714(\genfrac{}{}{0ex}{}{+15}{-12})\mathrm{fm}$, where the errors are sums, in quadrature, of statistical and all systematic errors. The precision of $w_0$ and $\sqrt{t_0}$ is comparable to or more precise than the best previous estimates, respectively. We then find the continuum mass dependence of $\sqrt{t_0}$ and $w_0$, which will be useful for estimating the scales of new ensembles. We also estimate the integrated autocorrelation length of $⟨E(t)⟩$. For long flow times, the autocorrelation length of $⟨E⟩$ appears to be comparable to that of the topological charge.

We study SU(2) gauge theory with two Dirac fermions in the adjoint representation of the gauge group on the lattice. Using clover improved Wilson fermion action with hypercubic truncated stout smearing we perform simulations at larger coupling than before. We measure the evolution of the coupling constant using the step scaling method with the Schrödinger functional and study the remaining discretization effects. At weak coupling we observe significant discretization effects, which make it difficult to obtain a fully controlled continuum limit. Nevertheless, the data remains consistent with the existence of a fixed point in the interval $2.2\lesssim g^{*2}\lesssim 3$. We also measure the anomalous dimension and find that its value at the fixed point is ${\gamma }^{*}\simeq 0.2\pm 0.03$.

In the framework of the relativistic independent quark model, the mass spectra and decay properties of $B$ and $B_s$ mesons are obtained using a Martin-like potential for the quark confinement. The predicted excited states are in good agreement with the experimental results as well as with the lattice QCD and other theoretical predictions. For instance, the $B_2(5747)$ as $1{{}^{3}P}_2$, $B_1(5721)$ as $1{{}^{3}P}_1$, and $B_0(5732)$ as $1{{}^{3}P}_0$ are identified. The spectroscopic parameters are used to calculate the electromagnetic transitions, pseudoscalar decay constants, hadronic decay widths, and leptonic decay widths. The present result for the decay constant, $f_B(1S)=188.56\mathrm{MeV}$, is in good agreement with recent lattice results (UKQCD Collaboration, Fermilab) and comparable with the experimental value of $(206.7\pm 8.9)$. The pseudoscalar decay constant for the $B_s$ meson obtained here, $f_{B_s}(1S)=240.21\mathrm{MeV}$, is in very good agreement with recent lattice QCD and QCD sum rule predictions. The predicted branching ratio for $B^{+}\to {\tau }^{+}{\nu }_{\tau }$ ($1.354\times {10}^{-4}$) is in accordance with the value, $(1.65\pm 0.34)\times {10}^{-4}$ reported by the Particle Data Group (PDG). The branching ratios of the rare decays $B_s^0\to {\mu }^{+}{\mu }^{-}$ ($(3.1\pm 0.7)\times {10}^{-9}$) and $B^0\to {\mu }^{+}{\mu }^{-}$ ($<6.3\times {10}^{-10}$) as observed by the CMS and LHCb Collaborations very recently are in accordance with our predictions of $3.602\times {10}^{-9}$ and $1.018\times {10}^{-10}$, respectively. The Cabibbo-favored hadronic branching ratios of $B^0\to D^{-}{\pi }^{+}$ ($3.724\times {10}^{-3}$), $B^0\to D^{*-}{\pi }^{+}$ ($3.475\times {10}^{-3}$), and $B_s\to D_s^{-}{\rho }^{+}$ ($3.800\times {10}^{-3}$) are in good agreement with the respective PDG values. The mixing parameters $x_q$, ${\chi }_q$ for $B^0-{\overline{B}}^0$ ($x_d=0.769$, ${\chi }_d=0.1859$) and $B_s-{\overline{B}}_s$ ($x_s=26.41$, ${\chi }_s=0.49929$) are also found to be in excellent agreement with the PDG values of ($0.770\pm 0.008$, $0.1862\pm 0.0023$) and ($26.49\pm 0.29$, $0.499292\pm 0.000016$), respectively.

We investigate how the dimensionless ratio given by the Chern-Simons diffusion rate ${\mathrm{\Gamma }}_{\mathrm{CS}}$ divided by the product of the entropy density $s$ and temperature $T$ behaves across different kinds of phase transitions in the class of bottom-up nonconformal Einstein-dilaton holographic models originally proposed by Gubser and Nellore. By tuning the dilaton potential, one is able to holographically mimic a first order, a second order, or a crossover transition. In a first order phase transition, ${\mathrm{\Gamma }}_{\mathrm{CS}}/sT$ jumps at the critical temperature (as previously found in the holographic literature), while in a second order phase transition it develops an infinite slope. On the other hand, in a crossover, ${\mathrm{\Gamma }}_{\mathrm{CS}}/sT$ behaves smoothly, although displaying a fast variation around the pseudo-critical temperature. In all the cases, ${\mathrm{\Gamma }}_{\mathrm{CS}}/sT$ increases with decreasing $T$. The behavior of the Chern-Simons diffusion rate across different phase transitions is expected to play a relevant role for the chiral magnetic effect around the QCD critical end point, which is a second order phase transition point connecting a crossover band to a line of first order phase transition. Our findings in the present work add to the literature the first predictions for the Chern-Simons diffusion rate across second order and crossover transitions in strongly coupled nonconformal, non-Abelian gauge theories.

We develop a new semiclassical approach, which starts with the density matrix given by the Euclidean time path integral with fixed coinciding end points, and proceed by identifying classical (minimal Euclidean action) path, to be referred to as a flucton, which passes through this end point. Fluctuations around a flucton path are included, by standard Feynman diagrams, previously developed for instantons. We calculate the Green function and evaluate the one loop determinant both by direct diagonalization of the fluctuation equation and also via the trick with the Green functions. The two-loop corrections are evaluated by explicit Feynman diagrams, and some curious cancellation of logarithmic and polylog terms is observed. The results are fully consistent with large-distance asymptotics obtained in quantum mechanics. Two classic examples—quartic double-well and sine-Gordon potentials—are discussed in detail, while powerlike potential and quartic anharmonic oscillator are discussed in brief. Unlike other semiclassical methods, like WKB, we do not use the Schrödinger equation, and all the steps generalize to multidimensional or quantum fields cases straightforwardly.