We consider Einstein gravity in general dimensions, coupled to a scalar field either minimally or nonminimally, together with a generic scalar potential. By making appropriate choices of the scalar potential, we obtain large classes of new scalar hairy black holes that are asymptotic to planar anti–de Sitter spacetimes. For some classes of solutions, we can promote the scalar charge to be dependent on the advanced or retarded times in the Eddington-Finkelstein coordinates and obtain exact dynamic solutions. In particular, one class of the collapse solutions describes the evolution from the AdS vacua to some stable black hole states, driven by a conformally massless scalar. It is an explicit demonstration of nonlinear instability of the AdS vacuum that is stable at the linear level.

In a quantum theory of gravity spacetime behaves classically when quantum probabilities are high for histories of geometry and field that are correlated in time by the Einstein equation. Probabilities follow from the quantum state. This quantum perspective on classicality has important implications. (a) Classical histories are generally available only in limited patches of the configuration space on which the state lives. (b) In a given patch, states generally predict relative probabilities for an ensemble of possible classical histories. (c) In between patches classical predictability breaks down and is replaced by quantum evolution connecting classical histories in different patches. (d) Classical predictability can break down on scales well below the Planck scale, and with no breakdown in the classical equations of motion. We support and illustrate (a)–(d) by calculating the quantum transition across the de Sitter-like throat connecting asymptotically classical, inflating histories in the no-boundary quantum state. This supplies probabilities for how a classical history on one side transitions and branches into a range of classical histories on the opposite side. We also comment on the implications of (a)–(d) for the dynamics of black holes and eternal inflation.

It has been argued that the small perturbations to the homogeneous and isotropic configurations of a canonical scalar field in an expanding universe do not grow. We show that this is not true in general, and clarify the root of the misunderstanding. We revisit a simple model in which the zero mode of a free scalar field oscillates with high frequency around the minimum of the potential. Under this assumption the linear perturbations grow like those in the standard cold dark matter scenario, but with a Jeans length at the scale of the Compton wavelength of the scalar particle. Contrary to previous analyses in the literature our results do not rely on time averages and/or fluid identifications, and instead we solve both analytically (in terms of a well-defined series expansion) and numerically the linearized Einstein-Klein-Gordon system. Also, we use gauge-invariant fields, which makes the physical analysis more transparent and simplifies the comparison with previous works carried out in different gauges. As a byproduct of this study we identify a time-dependent modulation of the different physical quantities associated to the background as well as the perturbations with potential observational consequences in dark matter models.

We study quantized solutions of the Wheeler de Witt (WdW) equation describing a closed Friedmann-Robertson-Walker universe with a $\mathrm{\Lambda }$ term and a set of massless scalar fields. We show that when $\mathrm{\Lambda }\ll 1$ in the natural units and the standard in-vacuum state is considered, either wave function of the universe, $\mathrm{\Psi }$, or its derivative with respect to the scale factor, $a$, behave as random quasiclassical fields at sufficiently large values of $a$. The former case is realized when $1\ll a\ll e^{\frac{2}{3\mathrm{\Lambda }}}$, while the latter is valid when $a\gg e^{\frac{2}{3\mathrm{\Lambda }}}$. The statistical rms value of the wave function is proportional to the Hartle-Hawking wave function for a closed universe with a $\mathrm{\Lambda }$ term. Alternatively, the behavior of our system at large values of $a$ can be described in terms of a density matrix corresponding to a mixed state, which is directly determined by statistical properties of $\mathrm{\Psi }$. Similar to $\mathrm{\Psi }$, the density matrix can be considered as a c-number valued in the position and momentum representations. The probability distribution to find a universe with particular values of the scale factor and field amplitudes following from this density matrix is again proportional to that of the Hartle-Hawking wave function, while the probability distribution over field velocities is nontrivial and different from what follows from the Hartle and Hawking formalism. We suppose that a similar behavior of $\mathrm{\Psi }$ can be found in all models exhibiting copious production of excitations with respect to the out-vacuum state associated with classical trajectories at large values of $a$. Thus, the third quantization procedure may provide a “boundary condition” for classical solutions of the WdW equation. Contrary to the previous proposals, in our case two equivalent descriptions of this classical solutions are possible. Either $\mathrm{\Psi }$ can be regarded as a stochastic classical quantity or the system can be viewed as being in a mixed state defined over classical solutions to the WdW equation.

We investigate the influence on the inflationary predictions from the reheating processes characterized by the $e$-folding number $N_{\mathrm{reh}}$ and the effective equation-of-state parameter $w_{\mathrm{reh}}$ during the reheating phase. For the first time, reheating processes can be constrained in the $N_{\mathrm{reh}}-w_{\mathrm{reh}}$ plane from Planck 2015. We find that for Higgs inflation with a nonminimal coupling to gravity, the predictions are insensitive to the reheating phase for current CMB measurements. We also find that the spontaneously broken SUSY inflation and axion monodromy inflation with ${\varphi }^{2/3}$ potential, which with instantaneous reheating lie outside or at the edge of the 95% confidence region in the $n_s-r$ plane from Planck 2015 TT, TE, $\mathrm{EE}+\mathrm{lowP}$, can well fit the data with the help of reheating processes. Future CMB experiments would put strong constraints on reheating processes.

We present joint constraints on the number of effective neutrino species $N_{\mathrm{eff}}$ and the sum of neutrino masses $\sum m_{\nu }$, based on a technique which exploits the full information contained in the one-dimensional Lyman-$\alpha$ forest flux power spectrum, complemented by additional cosmological probes. In particular, we obtain $N_{\mathrm{eff}}=2.91_{-0.22}^{+0.21}$ (95% C.L.) and $\sum m_{\nu }<0.15\mathrm{eV}$ (95% C.L.) when we combine BOSS Lyman-$\alpha$ forest data with CMB ($\text{Planck}+\mathrm{ACT}+\mathrm{SPT}+\mathrm{WMAP}$ polarization) measurements, and $N_{\mathrm{eff}}=2.88\pm 0.20$ (95% C.L.) and $\sum m_{\nu }<0.14\mathrm{eV}$ (95% C.L.) when we further add baryon acoustic oscillations. Our results provide strong evidence for the cosmic neutrino background from $N_{\mathrm{eff}}\sim 3$ ($N_{\mathrm{eff}}=0$ is rejected at more than $14\sigma$), and rule out the possibility of a sterile neutrino thermalized with active neutrinos (i.e., $N_{\mathrm{eff}}=4$)—or more generally any decoupled relativistic relic with $\mathrm{\Delta }{N}_{\mathrm{eff}}\simeq 1$—at a significance of over $5\sigma$, the strongest bound to date, implying that there is no need for exotic neutrino physics in the concordance $\mathrm{\Lambda }\mathrm{CDM}$ model.

Superposition of gravitational waves generated by astrophysical sources is expected to give rise to the stochastic gravitational-wave background. We focus on the background generated by the ring-down of black holes produced in the stellar core collapse events, which is one of several mechanisms for gravitational wave production in the stellar core collapse process. We systematically study the parameter space in this model, including the most recent information about the star formation rate and about the population of black holes as a function of redshift and of metallicity. We find that the upcoming second and third generation gravitational-wave detectors will be able to observe this stochastic background if the black hole ring-down efficiency at producing gravitational waves is sufficiently high, namely $\sim {10}^{-4}$ and $\sim {10}^{-6}$ of the black hole rest energy, respectively.

We derive the Edgeworth streaming model (ESM) for the redshift space correlation function starting from an arbitrary distribution function for biased tracers of dark matter by considering its two-point statistics and show that it reduces to the Gaussian streaming model (GSM) when neglecting non-Gaussianities. We test the accuracy of the GSM and ESM independent of perturbation theory using the Horizon Run 2 $N$-body halo catalog. While the monopole of the redshift space halo correlation function is well described by the GSM, higher multipoles improve upon including the leading order non-Gaussian correction in the ESM: the GSM quadrupole breaks down on scales below $30\mathrm{Mpc}/h$ whereas the ESM stays accurate to 2% within statistical errors down to $10\mathrm{Mpc}/h$. To predict the scale-dependent functions entering the streaming model we employ convolution Lagrangian perturbation theory (CLPT) based on the dust model and local Lagrangian bias. Since dark matter halos carry an intrinsic length scale given by their Lagrangian radius, we extend CLPT to the coarse-grained dust model and consider two different smoothing approaches operating in Eulerian and Lagrangian space, respectively. The coarse graining in Eulerian space features modified fluid dynamics different from dust while the coarse graining in Lagrangian space is performed in the initial conditions with subsequent single-streaming dust dynamics, implemented by smoothing the initial power spectrum in the spirit of the truncated Zel’dovich approximation. Finally, we compare the predictions of the different coarse-grained models for the streaming model ingredients to $N$-body measurements and comment on the proper choice of both the tracer distribution function and the smoothing scale. Since the perturbative methods we considered are not yet accurate enough on small scales, the GSM is sufficient when applied to perturbation theory.

We write a renormalization group equation for the function $f$ in a theory of gravity in the $f(R)$ truncation. Our equation differs from previous ones due to the exponential parametrization of the quantum fluctuations and to the choice of gauge. The cutoff procedure depends on three free parameters, and we find that there exist discrete special choices of parameters for which the flow equation has fixed points where $f=f_0+f_{1}R+f_2{R}^2$. For other values of the parameters the solution seems to be continuously deformed.

Adding a fermion to the standard model particle content which is a fiveplet under $SU(2{)}_L$ gives a dark matter candidate. The lightest state in the multiplet is neutral and automatically stable. The charged component of the multiplet is only slightly heavier and can travel a finite distance in the LHC detectors before decaying, leaving a charged track which disappears before the edge of the detector. We use the recent ATLAS and CMS searches to exclude a Majorana fiveplet with a mass up to 267 GeV. We estimate that with $3{\mathrm{ab}}^{-1}$ of $\sqrt{s}=14\mathrm{TeV}$ data this could be pushed to a mass of 520 GeV. These exclusions are $\sim 10\%$ greater than what is achieved for winolike dark matter. We also discuss how the doubly charged states could be used to distinguish a disappearing track signal from that given by a triplet such as the pure wino.

We revise the analysis of the bottomonium hyperfine splitting within the lattice nonrelativistic QCD. The Wilson coefficients of the radiatively improved lattice action are evaluated by a semianalytic approach based on the asymptotic expansion about the continuum limit. The nonrelativistic renormalization group is used to estimate the high-order radiative corrections. Our result for the $1S$ hyperfine splitting is $M_{\mathrm{\Upsilon }(1S)}-M_{{\eta }_b(1S)}=52.9\pm 5.5\mathrm{MeV}$. It reconciles the predictions of the continuum and lattice QCD and is in very good agreement with the most accurate experimental measurement by the Belle collaboration.

Recently the Yang-Mills gradient flow of pure SU(3) lattice gauge theory has been calculated in the range from $\beta =6/g_0^2=6.3$ to 7.5 (Asakawa et al.), where $g_0^2$ is the bare coupling constant of the SU(3) Wilson action. Estimates of the deconfining phase transition are available from $\beta =5.7$ to 6.8 (Francis et al.). Here it is shown that the entire range from 5.7 to 7.5 is well described by a power series of the lattice spacing $a$ times the lambda lattice mass scale ${\mathrm{\Lambda }}_L$, using asymptotic scaling in the 2-loop and 3-loop approximations for $a{\mathrm{\Lambda }}_L$. In both cases identical ratios for gradient flows versus deconfinement observables are obtained. Differences in the normalization constants with respect to ${\mathrm{\Lambda }}_L$ give a handle on their systematic errors.

To address a question of whether the chiral magnetic current is a static polarization or a genuine flow of charged particles, we elucidate the numerical formulation to simulate the net production of right-handed particles and anomalous currents with $CP$-breaking background fields which cause an imbalance between particles and antiparticles. For a concrete demonstration we numerically impose pulsed electric and magnetic fields to confirm our answer to the question that the produced net particles flow in the dynamical chiral magnetic effect. The rate for the particle production and the chiral magnetic current generation is quantitatively consistent with the axial anomaly, while they appear with a finite response time. We emphasize the importance to quantify the response time that would suppress observable effects of the anomalous current.

The semianalytical $O({\alpha }_s^4)$ expression for the renormalization group $\beta$ function in the $V$ scheme is obtained in the case of the $SU(N_c)$ gauge group. In the process of calculations we use the existing information about the three-loop perturbative approximation for the QCD static potential, evaluated in the $\overline{\mathrm{MS}}$ scheme. The comparison of the numerical values of the third and fourth coefficients for the QCD RG $\beta$ functions in the gauge-independent $V$ and $\overline{\mathrm{MS}}$ schemes and in the minimal momentum scheme in the Landau gauge is presented. The phenomenologically oriented comparisons for the coefficients of $O({\alpha }_s^4)$ expression for the $e^{+}{e}^{-}$-annihilation R-ratio in these schemes are presented. It is shown that taking into account these QCD contributions is of vital importance and leads to a drastic decrease of the scheme-dependence ambiguities of the fourth-order perturbative QCD approximations for the $e^{+}{e}^{-}$-annihilation R-ratio for the number of active flavors, $n_f=5$ in particular. We demonstrate that in the case of QED with $N$-types of leptons the coefficients of the ${\beta }^V$ function are closely related to the ones of the Gell-Mann–Low $\mathrm{\Psi }$ function and emphasize that they start to differ from each other at the fourth order due to the appearance of the extra $N^2$-contribution in the $V$ scheme. The source of this extra correction is clarified. The general all-order QED relations between the coefficients of the ${\beta }^V$ and $\mathrm{\Psi }$ functions are discussed.

We calculate several differential cross sections for $Z_0$ and high-$p_T$ jet production in the forward rapidity region at the LHC using the hybrid high energy factorization. We test various unintegrated gluon distributions involving subleading Balitski-Fadin-Kuraev-Lipatov effects (such as kinematic constraint, running strong coupling and Dokshitzer-Gribov-Lipatov-Altarelli-Parisi correction) and compare the results with experimental data obtained by the LHCb experiment. We find that the hard scale dependence of unintegrated gluon distributions, which effectively resums the Sudakov-type logarithms on the top of the resummation of the small $x$ logarithms, is essential to describe the normalized azimuthal decorrelations between the $Z_0$-boson and the jet.

The simplest realization of the inverse seesaw mechanism in a $SU(3{)}_C\otimes SU(3{)}_L\otimes U(1{)}_X$ gauge theory offers striking flavor correlations between rare charged lepton flavor violating decays and the measured neutrino oscillations parameters. The predictions follow from the gauge structure itself without the need for any flavor symmetry. Such tight complementarity between charged lepton flavor violation and neutrino oscillations renders the scenario strictly testable.

The associated production of a $W$ boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and $2.0{\mathrm{fb}}^{-1}$ collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The $W$ bosons are reconstructed using the $W\to \mu \nu$ decay and muons with a transverse momentum, $p_{\mathrm{T}}$, larger than 20 GeV in the pseudorapidity range $2.0<\eta <4.5$. The partons are reconstructed as jets with $p_{\mathrm{T}}>20\mathrm{GeV}$ and $2.2<\eta <4.2$. The sum of the muon and jet momenta must satisfy $p_{\mathrm{T}}>20\mathrm{GeV}$. The fraction of $W+\text{jet}$ events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the $W+b$ and $W+c$ production cross sections. The ratio of the $W+\text{jet}$ to $Z+\text{jet}$ production cross sections is also measured using the $Z\to \mu \mu$ decay. All results are in agreement with Standard Model predictions.

In this paper, we extend our study of the holographic Rényi entropy of single interval on a torus to the conformal field theory with $\mathcal{W}$ symmetry. To read the possible corrections from $\mathcal{W}$ fields clearly, we compute the thermal correction to the Rényi entropy up to the order $e^{-8\pi /TL}$. In the field theory, this requires us to compute the contribution from all the level 4 states, from both the vacuum module and $\mathcal{W}$ primaries. On the gravity side, after computing the eigenvalue of single Schottky generators to the order $e^{-4\pi /TL}$, we obtain the 1-loop quantum correction to the holographic Rényi entropy. We find complete agreement between the bulk and boundary theories.

Standard methods for calculating the black hole entropy beyond general relativity are ambiguous when the horizon is nonstationary. We fix these ambiguities in all quadratic curvature gravity theories, by demanding that the entropy be increasing at every time, for linear perturbations to a stationary black hole. Our result matches with the entropy formula found previously in holographic entanglement entropy calculations. We explicitly calculate the entropy increase for Vaidya-like solutions in Ricci-tensor gravity to show that (unlike the Wald entropy) the holographic entropy obeys a second law.

We study the vacuum stability of a minimal Higgs portal model in which the standard model (SM) particle spectrum is extended to include one complex scalar field and one Dirac fermion. These new fields are singlets under the SM gauge group and are charged under a global $U(1)$ symmetry. Breaking of this $U(1)$ symmetry results in a massless Goldstone boson, a massive $CP$-even scalar, and splits the Dirac fermion into two new mass eigenstates, corresponding to Majorana fermions. The lightest Majorana fermion $(w)$ is absolutely stable, providing a plausible dark matter (DM) candidate. We show that interactions between the Higgs sector and the lightest Majorana fermion which are strong enough to yield a thermal relic abundance consistent with observation can easily destabilize the electroweak vacuum or drive the theory into a nonperturbative regime at an energy scale well below the Planck mass. However, we also demonstrate that there is a region of the parameter space which develops a stable vacuum (up to the Planck scale), satisfies the relic abundance, and is in agreement with direct DM searches. Such an interesting region of the parameter space corresponds to DM masses $350\mathrm{GeV}\lesssim m_w\lesssim 1\mathrm{TeV}$. The region of interest is within reach of second-generation DM direct detection experiments.