Gravitational waves from neutron star binary inspirals contain information about the as yet unknown equation of state of supranuclear matter. In the absence of definitive experimental evidence that determines the correct equation of state, a number of diverse models that give the pressure inside a neutron star as function of its density have been constructed by nuclear physicists. These models differ not only in the approximations and techniques they employ to solve the many-body Schrödinger equation, but also in the internal neutron star composition they assume. We study whether gravitational wave observations of neutron star binaries in quasicircular inspirals up to contact will allow us to distinguish between equations of state of differing internal composition, thereby providing important information about the properties and behavior of extremely high density matter. We carry out a Bayesian model selection analysis, and find that second generation gravitational wave detectors can heavily constrain equations of state that contain only quark matter, but hybrid stars containing both normal and quark matter are typically harder to distinguish from normal matter stars. A gravitational wave detection with a signal-to-noise ratio of 20 and masses around $1.4M_{\odot }$ would provide indications of the existence or absence of strange quark stars, while a signal-to-noise ratio 30 detection could either detect or rule out strange quark stars with a 20 to 1 confidence. The presence of kaon condensates or hyperons in neutron star inner cores cannot be easily confirmed. For example, for the equations of state studied in this paper, even a gravitational wave signal with a signal-to-noise ratio as high as 60 would not allow us to claim a detection of kaon condensates or hyperons with confidence greater than 5 to 1. On the other hand, if kaon condensates and hyperons do not form in neutron stars, a gravitational wave signal with similar signal-to-noise ratio would be able to constrain their existence with an 11 to 1 confidence for high-mass systems. We, finally, find that combining multiple lower signal-to-noise ratio detections (stacking) must be handled with caution since it could fail in cases where the prior information dominates over new information from the data.

After a brief summary of the basic properties of stationary spacetimes representing rotating, charged black holes in strong axisymmetric magnetic fields, we concentrate on extremal cases, for which the horizon surface gravity vanishes. We investigate their properties by constructing simpler spacetimes that exhibit their geometries near degenerate horizons. Starting from the symmetry arguments we find that the near-horizon geometries of extremal magnetized Kerr-Newman black holes can be characterized by just one dimensionless parameter: “effective Kerr-Newman mixing angle.” Employing the near-horizon geometries we demonstrate the Meissner effect of magnetic field expulsion from extremal black holes.

We propose a new efficient strategy to construct exact solutions of Einstein-scalar gravities. We find that with some given metric Ansatz the equations of motion (EOMs) are invariant under a rescaling operation along the radial direction, which makes the function of the scalar field scale invariant. Our strategy is to use the symmetry of the EOMs to give a scale-invariant Ansatz for the scalar field first, then derive the metric and corresponding scalar potential later. We construct large classes of exact solutions with two kinds of spherical metric, which include many new scalar hairy black holes in different dimensions and some three dimensional solitons and conical defects. We also discuss the thermodynamics of these solutions in general with Wald’s formula.

We propose that dark matter is not yet another new particle in nature, but that it is a remnant of quantum gravitational effects on known fields. We arrive at this possibility in an indirect and surprising manner: by considering retarded, nonlocal, and Lorentzian evolution for quantum fields. This is inspired by recent developments in causal set theory, where such an evolution shows up as the continuum limit of scalar field propagation on a background causal set. Concretely, we study the quantum theory of a massless scalar field whose evolution is given not by the the d’Alembertian $\square$, but by an operator $\tilde{\square }$ which is Lorentz invariant, reduces to $\square$ at low energies, and defines an explicitly retarded evolution: $(\tilde{\square }\varphi )(x)$ only depends on $\varphi (y)$, where $y$ is in the causal past of $x$. This modification results in the existence of a continuum of massive particles, in addition to the usual massless ones, in the free theory. When interactions are introduced, these massive or off-shell quanta can be produced by the scattering of massless particles, but once produced, they no longer interact, which makes them a natural candidate for dark matter.

We address the question of how one can modify the inflationary tensor spectrum without changing at all the successful predictions on the curvature perturbation. We show that this is indeed possible, and determine the two quadratic curvature corrections that are free from instabilities and affect only the tensor sector at the level of linear cosmological perturbations. Both of the two corrections can reduce the tensor amplitude, though one of them generates large non-Gaussianity of the curvature perturbation. It turns out that the other one corresponds to so-called Lorentz-violating Weyl gravity. In this latter case one can obtain as small as 65% of the standard tensor amplitude. Utilizing this effect we demonstrate that even power-law inflation can be within the $2\sigma$ contour of the Planck results.

We show that maximally helical hypermagnetic fields produced during pseudoscalar inflation can generate the observed baryon asymmetry of the Universe via the $B+L$ anomaly in the Standard Model. We find that most of the parameter space of pseudoscalar inflation that explains the cosmological data leads to baryon overproduction; hence, the models of natural inflation are severely constrained. We also point out a connection between the baryon number and topology of the relic magnetic fields. Both the magnitude and sign of magnetic helicity can be detected in future diffuse gamma ray data. This could hint to a link between inflation and the baryon asymmetry of the Universe.

We investigate the properties of octet and decuplet baryons in a light-front holographic model. By taking into account the effect of nonvanishing quark mass, we obtain the modified light-front wave functions which are applicable at both low and high energy scales. We calculate the spectra, form factors, magnetic moments and electromagnetic radii of octet and decuplet baryons with the results all matching the experiments well. The axial charge, which describes the contribution of quark helicity to the proton spin in the quark-parton model at the high energy scale, is also consistent with the experimental value. Therefore, the light-front holographic method is successful in studying hadronic physics at all energy scales, and the nonzero quark mass is essential to understand the spin structures together with other low energy properties.

We show, via a careful analytical and numerical analysis, that a pseudo-Goldstone nature of the Higgs is naturally embodied by an elementary realization that also serves as ultraviolet completion. Renormalizability married to perturbation theory allows us to precisely determine the quantum corrections of the theory while permitting us to explore the underlying parameter space. By characterizing the available parameter space of the extended Higgs sector we discover that the preferred electroweak alignment angle is centered around $\theta \simeq 0.02$, corresponding to the Higgs chiral symmetry breaking scale $f\simeq 14\mathrm{TeV}$. The latter is almost 60 times higher than the Standard Model electroweak scale. However, due to the perturbative nature of the theory, the spectrum of the enlarged Higgs sector remains in the few TeV energy range. We also analyze precision constraints and the relevant phenomenological aspects of the theory.

We show that Ma’s scotogenic model, which is arguably one of the simplest settings containing a dark matter candidate and generating a naturally suppressed active neutrino mass at one-loop level, suffers from a potentially severe hierarchy-type problem. In case the right-handed neutrinos involved have sufficiently large masses, they can via loop effects drive the mass parameter of the inert scalar contained in the model toward negative values. This behavior leads to a breaking of the ${\mathbb{Z}}_2$ parity symmetry built into the model which is paramount to keeping the setting consistent at low energies—without it the model would lose its dark matter candidate, and the neutrino mass would not be naturally suppressed. Thus, if the breaking occurs at a sufficiently low scale, it could potentially spoil the success of the whole model. Trying to avoid this consistency problem leads to a new constraint on the model parameter space which has not yet been described in the literature.

We present a calculation of the hindered M1 $\mathrm{\Upsilon }(2S)\to {\eta }_b(1S)\gamma$ decay rate using lattice nonrelativistic quantum chromodynamics. The calculation includes spin-dependent relativistic corrections to the NRQCD action through $\mathcal{O}(v^6)$ in the quark’s relative velocity, relativistic corrections to the leading order current which mediates the transition through the quark’s magnetic moment, radiative corrections to the leading spin-magnetic coupling and for the first time a full error budget. We also use gluon field ensembles at multiple lattice spacing values, all of which include $u$, $d$, $s$ and $c$ quark vacuum polarization. Our result for the branching fraction is $\mathcal{B}(\mathrm{\Upsilon }(2S)\to {\eta }_b(1S)\gamma )=5.4(1.8)\times {10}^{-4}$, which agrees with the current experimental value.

It is commonly believed that the lowest-lying scalar glueball lies somewhere in the isosinglet scalar mesons $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$ denoted generically by $f_0$. In this work we consider lattice calculations and experimental data to infer the glue and $q\overline{q}$ components of $f_0$. These include the calculations of the scalar glueball masses in quenched and unquenched lattice QCD, measurements of the radiative decays $J/\psi \to \gamma f_0$, the ratio of $f_0$ decays to $\pi \pi$, $K\overline{K}$ and $\eta \eta$, the ratio of $J/\psi$ decays to $f_0(1710)\omega$ and $f_0(1710)\varphi$, the $f_0$ contributions to $B_s\to J/\psi {\pi }^{+}{\pi }^{-}$, and the near mass degeneracy of $a_0(1450)$ and $K_0^{*}(1430)$. All analyses suggest the prominent glueball nature of $f_0(1710)$ and the flavor octet structure of $f_0(1500)$.

Studies of D and B meson decays into hadrons have been used to test the standard model in the last 15 years. A heavy meson decay involves the combined effects of a primary weak vertex and subsequent hadronic final-state interactions, which determine the shapes of Dalitz plots. The fact that final products involve light mesons indicates that the QCD vacuum is an active part of the problem. This makes the description of these processes rather involved and, in spite of its importance, phenomenological analyses tend to rely on crude models. Our group produced, some time ago, a schematic calculation of the decay $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$, which provided a reasonable description of data. Its main assumption was the dominance of the weak vector current, which yields a nonfactorizable interaction. Here we refine that calculation by including the correct momentum dependence of the weak vertex and extending the energy ranges of $\pi \pi$ and $K\pi$ subamplitudes present into the problem. These new features make the present treatment more realistic and bring theory closer to data.

We investigate correlations of the Polyakov loop fluctuations with eigenmodes of the lattice Dirac operator. Their analytic relations are derived on the temporally odd-number size lattice with the normal nontwisted periodic boundary condition for the link variables. We find that the low-lying Dirac modes yield negligible contributions to the Polyakov loop fluctuations. This property is confirmed to be valid in confined and deconfined phases by numerical simulations in SU(3) quenched QCD. These results indicate that there is no direct, one-to-one correspondence between confinement and chiral symmetry breaking in QCD in the context of different properties of the Polyakov loop fluctuation ratios.

Nuclear matrix elements (NME) for exchange of arbitrary mass neutrinos are calculated in the interacting boson model (IBM-2). By combining the NME with the phase space factors (PSF), expected half-lives for neutrinos of mass $m_N$ and coupling $U_{eN}$ are estimated. Limits on sterile neutrinos with masses in the eV, keV, MeV-GeV, and TeV range are given.

This paper presents a search for Higgs bosons decaying to four leptons, either electrons or muons, via one or two light exotic gauge bosons $Z_d$, $H\to Z{Z}_d\to 4\ell$ or $H\to Z_d{Z}_d\to 4\ell$. The search was performed using $pp$ collision data corresponding to an integrated luminosity of about $20{\mathrm{fb}}^{-1}$ at the center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$ recorded with the ATLAS detector at the Large Hadron Collider. The observed data are well described by the Standard Model prediction. Upper bounds on the branching ratio of $H\to Z{Z}_d\to 4\ell$ and on the kinetic mixing parameter between the $Z_d$ and the Standard Model hypercharge gauge boson are set in the range $(1–9)\times 10^{-5}$ and $(4–17)\times 10^{-2}$ respectively, at 95% confidence level assuming the Standard Model branching ratio of $H\to Z{Z}^{*}\to 4\ell$, for $Z_d$ masses between 15 and 55 GeV. Upper bounds on the effective mass mixing parameter between the $Z$ and the $Z_d$ are also set using the branching ratio limits in the $H\to Z{Z}_d\to 4\ell$ search, and are in the range $(1.5–8.7)\times 10^{-4}$ for $15<m_{Z_d}<35\mathrm{GeV}$. Upper bounds on the branching ratio of $H\to Z_d{Z}_d\to 4\ell$ and on the Higgs portal coupling parameter, controlling the strength of the coupling of the Higgs boson to dark vector bosons are set in the range $(2–3)\times 10^{-5}$ and $(1–10)\times 10^{-4}$ respectively, at 95% confidence level assuming the Standard Model Higgs boson production cross sections, for $Z_d$ masses between 15 and 60 GeV.

In this paper, we study the holographic Rényi entropy of a large interval on a circle at high temperature for the two-dimensional conformal field theory (CFT) dual to pure ${\mathrm{AdS}}_3$ gravity. In the field theory, the Rényi entropy is encoded in the CFT partition function on $n$-sheeted torus connected with each other by a large branch cut. As proposed by Chen and Wu [Large interval limit of Rényi entropy at high temperature, arXiv:1412.0763], the effective way to read the entropy in the large interval limit is to insert a complete set of state bases of the twist sector at the branch cut. Then the calculation transforms into an expansion of four-point functions in the twist sector with respect to $e^{-\frac{2\pi TR}{n}}$. By using the operator product expansion of the twist operators at the branch points, we read the first few terms of the Rényi entropy, including the leading and next-to-leading contributions in the large central charge limit. Moreover, we show that the leading contribution is actually captured by the twist vacuum module. In this case by the Ward identity the four-point functions can be derived from the correlation function of four twist operators, which is related to double interval entanglement entropy. Holographically, we apply the recipe in [T. Faulkner, The entanglement Rényi entropies of disjoint intervals in AdS/CFT, arXiv:1303.7221] and [T. Barrella et al., Holographic entanglement beyond classical gravity, J. High Energy Phys. 09 (2013) 109] to compute the classical Rényi entropy and its one-loop quantum correction, after imposing a new set of monodromy conditions. The holographic classical result matches exactly with the leading contribution in the field theory up to $e^{-4\pi TR}$ and $l^6$, while the holographical one-loop contribution is in exact agreement with next-to-leading results in field theory up to $e^{-\frac{6\pi TR}{n}}$ and $l^4$ as well.

We consider Yang-Mills theories in a recently proposed family of nonlinear covariant gauges that consistently deals with the issue of Gribov ambiguities. Such gauges provide a generalization of the Curci-Ferrari-Delbourgo-Jarvis gauges which can be formulated as an extremization procedure and might be implemented in numerical calculations. This would allow for nonperturbative studies of Yang-Mills correlators in a broad class of covariant gauges continuously connected to the well-studied Landau gauge. We compute the ghost and gluon propagators in the continuum formulation at one-loop order in perturbation theory and we study their momentum dependence down to the deep infrared regime, with and without renormalization-group improvement. In particular, we show that the theory admits infrared-safe renormalization-group trajectories with no Landau pole. Both the gluon and the ghost behave as massive fields at low energy, and the gluon propagator is transverse even away from the Landau gauge limit. We compare our results to those obtained in the usual Curci-Ferrari model, which allows us to pinpoint the specific effects arising from our treatment of Gribov copies.