We study the phase diagram of two-flavor massless QCD at finite baryon density by applying the functional renormalization group (FRG) for a quark-meson model with $\sigma$, $\pi$, and $\omega$ mesons. The dynamical fluctuations of quarks, $\sigma$, and $\pi$ are included in the flow equations, while the amplitudes of $\omega$ fields are also allowed to fluctuate. At high temperature the effects of the $\omega$ field on the phase boundary are qualitatively similar to the mean-field calculations; the phase boundary is shifted to the higher chemical potential region. As the temperature is lowered, however, the transition line bends back to the lower chemical potential region, irrespective of the strength of the vector coupling. In our FRG calculations, the driving force of the low temperature first order line is the fluctuations rather than the quark density, and the effects of $\omega$ fields have little impact. At low temperature, the effective potential at small $\sigma$ field is very sensitive to the infrared cutoff scale, and this significantly affects our determination of the phase boundaries. The critical chemical potential at the tricritical point is affected by the $\omega$-field effects, but its critical temperature stays around the similar value. Some caveats are given in interpreting our model results.

Using the data samples of $1.31\times {10}^{9}J/\psi$ events and $4.48\times {10}^8\psi (3686)$ events collected with the BESIII detector, partial wave analyses on the decays $J/\psi$ and $\psi (3686)\to {\pi }^{+}{\pi }^{-}{\eta }^{\prime }$ are performed with a relativistic covariant tensor amplitude approach. The dominant contribution is found to be $J/\psi$ and $\psi (3686)$ decays to $\rho {\eta }^{\prime }$. In the $J/\psi$ decay, the branching fraction $\mathcal{B}(J/\psi \to \rho {\eta }^{\prime })$ is determined to be $(7.90\pm 0.19(\mathrm{stat})\pm 0.49(\mathrm{sys}))\times {10}^{-5}$. Two solutions are found in the $\psi (3686)$ decay, and the corresponding branching fraction $\mathcal{B}(\psi (3686)\to \rho {\eta }^{\prime })$ is $(1.02\pm 0.11(\mathrm{stat})\pm 0.24(\mathrm{sys}))\times {10}^{-5}$ for the case of destructive interference, and $(5.69\pm 1.28(\mathrm{stat})\pm 2.36(\mathrm{sys}))\times {10}^{-6}$ for constructive interference. As a consequence, the ratios of branching fractions between $\psi (3686)$ and $J/\psi$ decays to $\rho {\eta }^{\prime }$ are calculated to be $(12.9\pm 1.4(\mathrm{stat})\pm 3.1(\mathrm{sys}))\%$ and $(7.2\pm 1.6(\mathrm{stat})\pm 3.0(\mathrm{sys}))\%$, respectively. We also determine the inclusive branching fractions of $J/\psi$ and $\psi (3686)$ decays to ${\pi }^{+}{\pi }^{-}{\eta }^{\prime }$ to be $(1.36\pm 0.02(\mathrm{stat})\pm 0.08(\mathrm{sys}))\times {10}^{-4}$ and $(1.51\pm 0.14(\mathrm{stat})\pm 0.23(\mathrm{sys}))\times {10}^{-5}$, respectively.

We report an absolute calibration of the ionization yields ($Q_y$) and fluctuations for electronic recoil events in liquid xenon at discrete energies between 186 eV and 33.2 keV. The average electric field applied across the liquid xenon target is $180\mathrm{V}/\mathrm{cm}$. The data are obtained using low energy ${}^{127}\mathrm{Xe}$ electron capture decay events from the 95.0-day first run from LUX (WS2013) in search of weakly interacting massive particles. The sequence of gamma-ray and x-ray cascades associated with ${}^{127}\mathrm{I}$ deexcitations produces clearly identified two-vertex events in the LUX detector. We observe the K-(binding energy, 33.2 keV), L-(5.2 keV), M-(1.1 keV), and N-(186 eV) shell cascade events and verify that the relative ratio of observed events for each shell agrees with calculations. The N-shell cascade analysis includes single extracted electron (SE) events and represents the lowest-energy electronic recoil in situ measurements that have been explored in liquid xenon.

We develop off-shell formulations for $\mathcal{N}=1$ and $\mathcal{N}=2$ anti-de Sitter supergravity theories in three spacetime dimensions that contain gauge two-forms in the auxiliary field sector. These formulations are shown to allow consistent couplings of supergravity to the Green-Schwarz superstring with $\mathcal{N}=1$ or $\mathcal{N}=2$ spacetime supersymmetry. In addition to being $\kappa$-symmetric, the Green-Schwarz superstring actions constructed are also invariant under super-Weyl transformations of the target space. We also present a detailed study of models for spontaneously broken local supersymmetry in three dimensions obtained by coupling the known off-shell $\mathcal{N}=1$ and $\mathcal{N}=2$ supergravity theories to nilpotent Goldstino superfields.

We compute change in entanglement entropy for a single interval in the $1+1$-dimensional sine-Gordon model perturbatively in the coupling. The sine-Gordon perturbation can be thought of as deformation of the free conformal field theory by a primary operator with dimension $\mathrm{\Delta }$. In an independent computation we calculate holographic entanglement entropy for that interval from three-dimensional bulk anti–de Sitter space which has a massive scalar with its mass satisfying $m^2=\mathrm{\Delta }(\mathrm{\Delta }-2)$. We show that the two results match for near-marginal perturbations up to leading order in the coupling.

It is proved that spherically symmetric asymptotically flat neutral black holes cannot support spatially regular static configurations made of massive scalar fields with nonminimal coupling to gravity. Interestingly, our compact no-hair theorem is valid for generic values of the dimensionless physical parameter $\xi$ which quantifies the strength of coupling between the scalar field and the spacetime curvature.

In this paper, we study the hyperbolicity of the equations of motion for the most general Horndeski theory of gravity in a generic “weak field” background. We first show that a special case of this theory, namely Einstein–dilaton–Gauss-Bonnet gravity, fails to be strongly hyperbolic in any generalized harmonic gauge. We then complete the proof that the most general Horndeski theory which, for weak fields, is strongly hyperbolic in a generalized harmonic gauge is simply a “k-essence” theory coupled to Einstein gravity and that adding any more general Horndeski term will result in a weakly, but not strongly, hyperbolic theory.

We study a model of a cyclic, spatially homogeneous, anisotropic, “mixmaster” universe of Bianchi type IX, containing a radiation field with noncomoving (“tilted” with respect to the tetrad frame of reference) velocities and vorticity. We employ a combination of numerical and approximate analytic methods to investigate the consequences of the second law of thermodynamics on the evolution. We model a smooth cycle-to-cycle evolution of the mixmaster universe, bouncing at a finite minimum, by the device of adding a comoving “ghost” field with negative energy density. In the absence of a cosmological constant, an increase in entropy, injected at the start of each cycle, causes an increase in the volume maxima, increasing approach to flatness, falling velocities and vorticities, and growing anisotropy at the expansion maxima of successive cycles. We find that the velocities oscillate rapidly as they evolve and change logarithmically in time relative to the expansion volume. When the conservation of momentum and angular momentum constraints are imposed, the spatial components of these velocities fall to smaller values when the entropy density increases, and vice versa. Isotropization is found to occur when a positive cosmological constant is added because the sequence of oscillations ends and the dynamics expand forever, evolving towards a quasi–de Sitter asymptote with constant velocity amplitudes. The case of a single cycle of evolution with a negative cosmological constant added is also studied.

We study fermion condensation in the Randall-Sundrum background as a setting for composite Higgs models. We formalize the computation of the Coleman-Weinberg potential and present a simple, general formula. Using this tool, we study the competition of fermion multiplets with different boundary conditions, to find conditions for creating a little hierarchy with the Higgs field expectation value much smaller than the intrinsic Randall-Sundrum mass scale.

We study a scenario in which the only light new particles are a Majorana fermion dark matter candidate and one or more QCD-charged scalars, which couple to light quarks. This scenario has several interesting phenomenological features if the new particles are nearly degenerate in mass. In particular, LHC searches for the light scalars have reduced sensitivity, since the visible and invisible products tend to be softer. Moreover, dark matter-scalar coannihilation can allow even relatively heavy dark matter candidates to be consistent thermal relics. Finally, the dark matter nucleon scattering cross section is enhanced in the quasidegenerate limit, allowing direct detection experiments to use both spin-independent and spin-dependent scattering to probe regions of parameter space beyond those probed by the LHC. Although this scenario has a broad application, we phrase this study in terms of the minimal supersymmetric standard model, in the limit where the only light sparticles are a binolike dark matter candidate and light-flavored squarks.

Exact sum rules for the longitudinal and transverse part of the vector channel spectral functions at nonzero momentum are derived in the first part of the paper. The sum rules are formulated for the finite temperature spectral functions, from which the vacuum component has been subtracted, and represent a generalization of previous work in which sum rules were derived only for the zero-momentum limit. In the second part of the paper, we demonstrate how the sum rules can be used as constraints in spectral fits to lattice data at various temperatures, with the latest dynamical lattice quantum chromodynamics data at zero momentum.

We discuss the approaches by Deffayet et al. (DPSV) and Kobayashi et al. (KYY) to the analysis of linearized scalar perturbations about a spatially flat FLRW background in Horndeski theory. We identify additional, potentially important terms in the DPSV approach. However these terms vanish upon a judicious gauge choice. We derive a gauge invariant quadratic action for metric and Galileon perturbations in ${\mathcal{L}}_3$ and ${\mathcal{L}}_3+{\mathcal{L}}_4$ theories and show that actions obtained in the DPSV and KYY approaches follow from this gauge invariant action in particular gauges.

Bekenstein and Mayo proposed a generalized bound for the entropy, which implies some inequalities between the charge, energy, angular momentum, and size of the macroscopic system. Dain has shown that Maxwell’s electrodynamics satisfies all three inequalities. We investigate the validity of these relations in the context of nonlinear electrodynamics and show that Born-Infeld electrodynamics satisfies all of them. However, contrary to the linear theory, there is no rigidity statement in Born-Infeld. We study the physical meaning and the relationship between these inequalities, and in particular, we analyze the connection between the energy-angular momentum inequality and causality.

We present a robust method to characterize the gravitational wave emission from the remnant of a neutron star coalescence. Our approach makes only minimal assumptions about the morphology of the signal and provides a full posterior probability distribution of the underlying waveform. We apply our method on simulated data from a network of advanced ground-based detectors and demonstrate the gravitational wave signal reconstruction. We study the reconstruction quality for different binary configurations and equations of state for the colliding neutron stars. We show how our method can be used to constrain the yet-uncertain equation of state of neutron star matter. The constraints on the equation of state we derive are complementary to measurements of the tidal deformation of the colliding neutron stars during the late inspiral phase. In the case of nondetection of a post-merger signal following a binary neutron star inspiral, we show that we can place upper limits on the energy emitted.

We study a novel class of higher-curvature gravity models in $n$ spacetime dimensions which we call Ricci polynomial gravity. The action consists purely of a polynomial in Ricci curvature of order $N$. In the absence of the second-order terms in the action, the models are ghost free around the Minkowski vacuum. By appropriately choosing the coupling coefficients in front of each term in the action, it is shown that the models can have multiple vacua with different effective cosmological constants, and can be made free of ghost and scalar degrees of freedom around at least one of the maximally symmetric vacua for any $n>2$ and any $N\ge 4$. We also discuss some of the physical implications of the existence of multiple vacua in the contexts of black hole physics and cosmology.

We construct new black brane solutions in the context of Horndeski gravity, in particular, in its K-essence sector. These models are supported by axion scalar fields that depend only on the horizon coordinates. The dynamics of these fields is determined by a K-essence term that includes the standard kinetic term $X$ and a correction of the form $X^k$. We find both neutral and charged exact and analytic solutions in $D$-dimensions, which are asymptotically anti–de Sitter. Then, we describe in detail the thermodynamical properties of the four-dimensional solutions and we compute the dual holographic DC conductivity.

We investigate the possibility of observing very low frequency (VLF) electromagnetic radiation produced from the vacuum by gravitational waves. We review the calculations leading to the possibility of vacuum conversion of gravitational waves into electromagnetic waves and show how this process evades the well-known prohibition against particle production from gravitational waves. Using Newman-Penrose scalars, we estimate the luminosity of this proposed electromagnetic counterpart radiation coming from gravitational waves produced by neutron star oscillations. The detection of electromagnetic counterpart radiation would provide an indirect way of observing gravitational radiation with future spacecraft missions, especially lunar orbiting probes.