We explore some possibilities for obtaining useful metrics and dilatons for anti–de Sitter (AdS)/QCD models. As a guideline, we consider dilatons and/or metrics that on the one hand reproduce the mesonic spectrum, and that on the other hand allow us a correct implementation of chiral symmetry breaking in AdS/QCD models. We discuss two procedures: one is based on supersymmetric quantum mechanics techniques and the other considers the interpolation between some limits on dilatons and/or metrics.

Fluid-dynamical equations of motion can be derived from the Boltzmann equation in terms of an expansion around a single-particle distribution function which is in local thermodynamical equilibrium, i.e., isotropic in momentum space in the rest frame of a fluid element. However, in situations where the single-particle distribution function is highly anisotropic in momentum space, such as the initial stage of heavy-ion collisions at relativistic energies, such an expansion is bound to break down. Nevertheless, one can still derive a fluid-dynamical theory, called anisotropic dissipative fluid dynamics, in terms of an expansion around a single-particle distribution function, ${\widehat{f}}_{0\mathbf{k}}$, which incorporates (at least parts of) the momentum anisotropy via a suitable parametrization. We construct such an expansion in terms of polynomials in energy and momentum in the direction of the anisotropy and of irreducible tensors in the two-dimensional momentum subspace orthogonal to both the fluid velocity and the direction of the anisotropy. From the Boltzmann equation we then derive the set of equations of motion for the irreducible moments of the deviation of the single-particle distribution function from ${\widehat{f}}_{0\mathbf{k}}$. Truncating this set via the 14-moment approximation, we obtain the equations of motion of anisotropic dissipative fluid dynamics.

The vector boson fusion (VBF) event topology at the Large Hadron Collider (LHC) allows efficient suppression of dijet backgrounds and is therefore a promising target for new physics searches. We consider dark matter models which interact with the standard model through the electroweak sector—either through new scalar and pseudoscalar mediators which can be embedded into the Higgs sector or via effective operators suppressed by some higher scale—and therefore have significant VBF production cross sections. Using realistic simulations of the ATLAS and CMS analysis chain, including estimates of major error sources, we project the discovery and exclusion potential of the LHC for these models over the next decade.

The branching fractions of the $\mathrm{\Upsilon }(1S)$ inclusive decays into final states with a $J/\psi$ or a $\psi (2S)$ are measured with improved precision to be $\mathcal{B}(\mathrm{\Upsilon }(1S)\to J/\psi +\text{anything})=(5.25\pm 0.13(\mathrm{stat})\pm 0.25(\mathrm{syst}))\times {10}^{-4}$ and $\mathcal{B}(\mathrm{\Upsilon }(1S)\to \psi (2S)+\text{anything})=(1.23\pm 0.17(\mathrm{stat})\pm 0.11(\mathrm{syst}))\times {10}^{-4}$. The first search for $\mathrm{\Upsilon }(1S)$ decays into $XYZ$ states that decay into a $J/\psi$ or a $\psi (2S)$ plus one or two charged tracks yields no significant signals for $XYZ$ states in any of the examined decay modes, and upper limits on their production rates in $\mathrm{\Upsilon }(1S)$ inclusive decays are determined.

We discuss the magnetic responses of vector meson masses based on the hidden local symmetry (HLS) model in a constant magnetic field, described by the lightest two-flavor system including the pion, rho and omega mesons in the spectrum. The effective masses influenced under the magnetic field are evaluated according to the derivative or chiral expansion established in the HLS model. At the leading order $\mathcal{O}(p^2)$, the g factor of the charged rho meson is fixed to be 2, implying that the rho meson at this order is treated just like a pointlike spin-1 particle. Beyond the leading order, one finds anomalous magnetic interactions of the charged rho meson, involving the anomalous magnetic moment, which give corrections to the effective mass. It is then suggested that up to $\mathcal{O}(p^4)$ the charged rho meson tends to become massless. Of interest is that nontrivial magnetic dependence of neutral mesons emerges to give rise to the significant mixing among neutral mesons. Consequently, it leads to the dramatic enhancement of the omega meson mass, which is testable in future lattice simulations. Corrections from terms beyond $\mathcal{O}(p^4)$ are also addressed.

We study electrically charged perfect fluid toroidal structures encircling a spherically symmetric gravitating object with Schwarzschild spacetime geometry and endowed with a dipole magnetic field. The work represents a direct continuation of our previous general-relativistic studies of electrically charged fluid in the approximation of zero conductivity, which formed tori around a Reissner-Nordström black hole or a Schwarzschild black hole equipped with a test electric charge and immersed in an asymptotically uniform magnetic field. After a general introduction of the zero-conductivity charged fluid model, we discuss a variety of possible topologies of the toroidal fluid configurations. Along with the charged equatorial tori forming interesting coupled configurations, we demonstrate the existence of the off-equatorial tori, for which the dipole type of magnetic field seems to be necessary. We focus on orbiting structures with constant specific angular momentum and on those in permanent rigid rotation. We stress that the general analytical treatment developed in our previous works is enriched here by the integrated form of the pressure equations. To put our work into an astrophysical context, we identify the central object with an idealization of a nonrotating magnetic neutron star. Constraining ranges of its parameters and also parameters of the circling fluid, we discuss a possible relevance of the studied toroidal structures, presenting along with their topology also pressure, density, temperature and charge profiles.

We derive exact expressions for the scalar and electromagnetic self-forces and self-torques acting on arbitrary static extended bodies in arbitrary static spacetimes with any number of dimensions. Nonperturbatively, our results are identical in all dimensions. Meaningful point particle limits are quite different in different dimensions, however. These limits are defined and evaluated, resulting in simple “regularization algorithms” which can be used in concrete calculations. In these limits, self-interaction is shown to be progressively less important in higher numbers of dimensions; it generically competes in magnitude with increasingly high-order extended-body effects. Conversely, we show that self-interaction effects can be relatively large in $1+1$ and $2+1$ dimensions. Our motivations for this work are twofold: First, no previous derivation of the self-force has been provided in arbitrary dimensions, and heuristic arguments presented by different authors have resulted in conflicting conclusions. Second, the static self-force problem in arbitrary dimensions provides a valuable test bed with which to continue the development of general, nonperturbative methods in the theory of motion. Several new insights are obtained in this direction, including a significantly improved understanding of the renormalization process. We also show that there is considerable freedom to use different “effective fields” in the laws of motion—a freedom which can be exploited to optimally simplify specific problems. Different choices give rise to different inertias, gravitational forces, and electromagnetic or scalar self-forces, but there is a sense in which none of these quantities are individually accessible to experiment. Certain combinations are observable, however, and these remain invariant under all possible field redefinitions.

Following our previous paper, Bergeron et al., Smooth quantum dynamics of the mixmaster universe, Phys. Rev. D 92, 061302(R) (2015), concerning the quantization of the vacuum Bianchi IX model and the Born-Huang-Oppenheimer framework, we present a further analysis of the dynamical properties of the model. Consistently with the deep quantum regime, we implement the harmonic approximation of the anisotropy potential. We thus obtain manageable dynamical equations. We study the quantum anisotropic oscillations during the bouncing phase of the universe. Neglecting the backreaction from transitions between quantum anisotropy states, we obtain analytical results. In particular, we identify a parameter that is associated with dynamical properties of the quantum model and describes a sort of phase transition. Once the parameter exceeds its critical value, the Born-Huang-Oppenheimer approximation breaks down. The application of the present result to a simple model of the universe indicates that the parameter indeed exceeds its critical value and that there takes place a huge production of anisotropy at the bounce. This in turn must lead to a sustained phase of accelerated expansion, an inflationary phase. The quantitative inclusion of backreaction shall be examined in a follow-up paper based on the vibronic approach.

We investigate theories in which gravity arises as a consequence of entropy. We distinguish between two approaches to this idea: holographic gravity, in which Einstein’s equation arises from keeping entropy stationary in equilibrium under variations of the geometry and quantum state of a small region, and thermodynamic gravity, in which Einstein’s equation emerges as a local equation of state from constraints on the area of a dynamical light sheet in a fixed spacetime background. Examining holographic gravity, we argue that its underlying assumptions can be justified in part using recent results on the form of the modular energy in quantum field theory. For thermodynamic gravity, on the other hand, we find that it is difficult to formulate a self-consistent definition of the entropy, which represents an obstacle for this approach. This investigation points the way forward in understanding the connections between gravity and entanglement.

A number of works have shown that important information on the equation of state of matter at nuclear density can be extracted from the gravitational waves emitted by merging neutron-star binaries. We present a comprehensive analysis of the gravitational-wave signal emitted during the inspiral, merger, and postmerger of 56 neutron-star binaries. This sample of binaries, arguably the largest studied to date with realistic equations of state, spans six different nuclear-physics equations of state and ten masses, allowing us to sharpen a number of results recently obtained on the spectral properties of the gravitational-wave signal. Overall we find the following: (i) for binaries with masses differing no more than 20%, the frequency at gravitational-wave amplitude’s maximum is related quasiuniversally with the tidal deformability of the two stars; (ii) the spectral properties vary during the postmerger phase, with a transient phase lasting a few milliseconds after the merger and followed by a quasistationary phase; (iii) when distinguishing the spectral peaks between these two phases, a number of ambiguities in the identification of the peaks disappear, leaving a simple and robust picture; (iv) using properly identified frequencies, quasiuniversal relations are found between the spectral features and the properties of the neutron stars; (v) for the most salient peaks analytic fitting functions can be obtained in terms of the stellar tidal deformability or compactness. Altogether, these results support the idea that the equation of state of nuclear matter can be constrained tightly when a signal in gravitational waves from binary neutron stars is detected.

We investigate the problem of finding a pure spin-connection formulation of general relativity with nonvanishing cosmological constant. We first revisit the problem at the linearized level and find that the pure spin-connection, quadratic Lagrangian, takes a form reminiscent to Weyl gravity, given by the square of a Weyl-like tensor. Upon Hodge dualization, we show that the dual gauge field in $(\mathrm{A}){\mathrm{dS}}_D$ transforms under $GL(D)$ in the same representation as a massive graviton in the flat spacetime of the same dimension. We give a detailed proof that the physical degrees of freedom indeed correspond to a massless graviton propagating around the (anti-) de Sitter background and finally speculate about a possible nonlinear pure-connection theory dual to general relativity with cosmological constant.

We investigate the geodesics of a Schwarzschild spacetime embedded in an isotropic expanding cosmological background (McVittie metric). We focus on bound particle geodesics in a background including matter and phantom dark energy with constant dark energy equation-of-state parameter $w<-1$ involving a future big rip singularity at a time $t_{*}$. Such geodesics have been previously studied in the Newtonian approximation and found to lead to dissociation of bound systems at a time $t_{\text{rip}}<t_{*}$, which for a fixed background $w$ depends on a single dimensionless parameter ${\overline{\omega }}_0$ related to the angular momentum and depending on the mass and the size of the bound system. We extend this analysis to large massive bound systems where the Newtonian approximation is not appropriate and we compare the derived dissociation time with the corresponding time in the context of the Newtonian approximation. By identifying the time when the general-relativistic analog of the effective potential $V_{\text{eff}}$ minimum disappears due to the repulsive force of dark energy, we find that the dissociation time of bound systems occurs earlier than the prediction of the Newtonian approximation. However, the effect is negligible for all existing cosmological bound systems and it would become important only in hypothetical bound extremely massive (${10}^{20}{M}_{\odot }$) and large (100 Mpc) bound systems. We verify this result by explicitly solving the geodesic equations. This result is due to an interplay between the repulsive phantom dark energy effects and the existence of the well-known innermost stable orbits of Schwarzschild spacetimes.

We discuss the quasinormal oscillations of black holes which are sourced by a nonlinear electrodynamic field. While previous studies have focused on the computation of quasinormal frequencies for the wave or higher spin equation on a fixed background geometry described by such black holes, here we compute for the first time the quasinormal frequencies for the coupled electromagnetic-gravitational linear perturbations. To this purpose, we consider a parametrized family of Lagrangians for the electromagnetic field which contains the Maxwell Lagrangian as a special case. In the Maxwell case, the unique spherically symmetric black hole solutions are described by the Reissner-Nordström family and in this case it is well known that the quasinormal spectra in the even- and odd-parity sectors are identical to each other. However, when moving away from the Maxwell case, we obtain deformed Reissner-Nordström black holes, and we show that in this case there is a parity splitting in the quasinormal mode spectra. A partial explanation for this phenomena is provided by considering the eikonal (high-frequency) limit.

When a supernova explosion occurs in neighbors around hundreds pc, current and future neutrino detectors are expected to observe neutrinos from the presupernova star before the explosion. We show a possibility for obtaining the evidence for burning processes in the central region of presupernova stars though the observations of neutrino signals by current and future neutrino detectors such as KamLAND, JUNO, and Hyper-Kamiokande. We also investigate supernova alarms using neutrinos from presupernova stars in neighbors. If a supernova explodes at $\sim 200\mathrm{pc}$, future 20 kton size liquid scintillation detectors are expected to observe hundreds neutrino events. We also propose a possibility of the detection of neutrino events by Gd-loaded Hyper-Kamiokande using delayed $\gamma$-ray signals. These detectors could observe detailed time variation of neutrino events. The neutrino emission rate increases by the core contraction in the final evolution stage. However, the O and Si shell burnings suppress the neutrino emission for a moment. The observed decrease in the neutrino event rate before hours to the explosion is possibly evidence for the shell burnings. The observations of detailed time evolution of presupernova neutrino events could reveal properties of burning processes in the central region of presupernova stars.

We present the results of a search for weakly interacting massive particles (WIMPs) from the commissioning run of the PandaX-II experiment located at the China Jinping Underground Laboratory. A WIMP search data set with an exposure of $306\times 19.1\mathrm{kg}\text{−}\text{day}$ was taken, while its dominant ${}^{85}\mathrm{Kr}$ background was used as the electron recoil calibration. No WIMP candidates are identified, and a 90% upper limit is set on the spin-independent elastic WIMP-nucleon cross section with a lowest excluded cross section of $2.97\times {10}^{-45}{\mathrm{cm}}^2$ at a WIMP mass of $44.7\mathrm{GeV}/{\mathrm{c}}^2$.

We find a geometrical description from a field theoretical setup based on Wilson’s renormalization group in real space. We show that renormalization group equations of coupling parameters encode the metric structure of an emergent curved space, regarded to be an Einstein equation for the emergent gravity. Self-consistent equations of local order-parameter fields with an emergent metric turn out to describe low-energy dynamics of a strongly coupled field theory, analogous to the Maxwell equation of the Einstein-Maxwell theory in the ${\mathrm{AdS}}_{d+2}/{\mathrm{CFT}}_{d+1}$ duality conjecture. We claim that the ${\mathrm{AdS}}_3/{\mathrm{CFT}}_2$ duality may be interpreted as Landau-Ginzburg theory combined with Wilson’s renormalization group, which introduces vertex corrections into the Landau-Ginzburg theory in the large-$N_s$ limit, where $N_s$ is the number of fermion flavors.

The relevant phenomenology and the best search schemes of a subelectroweak-scale gauge boson can be vastly different depending on its coupling. For instance, the rare decay into a light gauge boson and the high precision parity test can be sensitive if it has an axial coupling. The minimal gauge extension of the standard model with the $U(1{)}_{B-L+xY}$ requires only three right-handed neutrinos, well suited to the current neutrino mass and mixing data, and no additional exotic matter fields. We study the light gauge boson of this symmetry in detail, including its axial coupling property from the hypercharge shift.

We investigate the possibility that the dark matter candidate is from a pure non-Abelian gauge theory of the hidden sector, motivated in large part by its elegance and simplicity. The dark matter is the lightest bound state made of the confined gauge fields, the hidden glueball. We point out that this simple setup is capable of providing rich and novel phenomena in the dark sector, especially in the parameter space of large $N$. They include self-interacting and warm dark matter scenarios, Bose-Einstein condensation leading to massive dark stars possibly millions of times heavier than our sun giving rise to gravitational lensing effects, and indirect detections through higher dimensional operators as well as interesting collider signatures.

We present results for the spectrum of a strongly interacting SU(3) gauge theory with $N_f=8$ light fermions in the fundamental representation. Carrying out nonperturbative lattice calculations at the lightest masses and largest volumes considered to date, we confirm the existence of a remarkably light singlet scalar particle. We explore the rich resonance spectrum of the 8-flavor theory in the context of the search for new physics beyond the standard model at the Large Hadron Collider (LHC). Connecting our results to models of dynamical electroweak symmetry breaking, we estimate the vector resonance mass to be about 2 TeV with a width of roughly 450 GeV, and predict additional resonances with masses below $\sim 3\mathrm{TeV}$.

We present a first QCD analysis of next-to-next-leading-order (NNLO) contributions of the spin-dependent parton distribution functions (PPDFs) in the nucleon and their uncertainties using the Jacobi polynomial approach. Having the NNLO contributions of the quark-quark and gluon-quark splitting functions in perturbative QCD [Nucl. Phys. B889, 351 (2014)], one can obtain the evolution of longitudinally polarized parton densities of hadrons up to NNLO accuracy of QCD. Very large sets of recent and up-to-date experimental data of spin structure functions of the proton $g_1^p$, neutron $g_1^n$, and deuteron $g_1^d$ have been used in this analysis. The predictions for the NNLO calculations of the polarized parton distribution functions as well as the proton, neutron and deuteron polarized structure functions are compared with the corresponding results of the NLO approximation. We form a mutually consistent set of polarized PDFs due to the inclusion of the most available experimental data including the recently high-precision measurements from COMPASS16 experiments [Phys. Lett. B 753, 18 (2016)]. We have performed a careful estimation of the uncertainties using the most common and practical method, the Hessian method, for the polarized PDFs originating from the experimental errors. The proton, neutron and deuteron structure functions and also their first moments, ${\mathrm{\Gamma }}^{\mathrm{p},\mathrm{n},\mathrm{d}}$, are in good agreement with the experimental data at small and large momentum fractions of $x$. We will discuss how our knowledge of spin-dependence structure functions can improve at small and large values of $x$ by the recent COMPASS16 measurements at CERN, the PHENIX and STAR measurements at RHIC, and at the future proposed colliders such as the Electron-Ion Collider.