We report the observation of Higgs boson decays to $W{W}^{*}$ based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of $25{\mathrm{fb}}^{-1}$ from $\sqrt{s}=7$ and 8 TeV $pp$ collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is $1.09_{-0.15}^{+0.16}{(\mathrm{stat})}_{-0.14}^{+0.17}(\text{syst})$. The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are $1.02\pm 0.19{(\mathrm{stat})}_{-0.18}^{+0.22}(\text{syst})$ and $1.27_{-0.40}^{+0.44}{(\mathrm{stat})}_{-0.21}^{+0.30}(\text{syst})$, respectively. At $\sqrt{s}=8\mathrm{TeV}$, the total production cross sections are measured to be $\sigma (gg\to H\to W{W}^{*})=4.6\pm 0.9{(\mathrm{stat})}_{-0.7}^{+0.8}(\text{syst})\mathrm{pb}$ and $\sigma (\mathrm{V}\mathrm{B}\mathrm{F}\hspace{0.17em}\hspace{0.17em}H\to W{W}^{*})=0.51_{-0.15}^{+0.17}{(\mathrm{stat})}_{-0.08}^{+0.13}(\text{syst})\mathrm{pb}$. The fiducial cross section is determined for the gluon-fusion process in exclusive final states with zero or one associated jet.

We investigate the phase diagram of QCD with heavy quarks at finite temperature and chemical potential in the context of background field methods. In particular, we use a massive extension of the Landau-DeWitt gauge which is motivated by previous studies of the deconfinement phase transition in pure Yang-Mills theories. We show that a simple one-loop calculation is able to capture the richness of the phase diagram in the heavy quark region, both at real and imaginary chemical potential. Moreover, dimensionless ratios of quantities directly measurable in numerical simulations are in good agreement with lattice results.

We investigate dynamics of magnetic thin-shells in three dimensional anti-de Sitter background. Because of the magnetic field, an oscillatory solution is possible. This oscillating shell can tunnel to a collapsing shell or a bouncing shell, where both tunnelings induce an event horizon and a singularity. In the entire path integral, via the oscillating solution, there is a nonzero probability to maintain a trivial causal structure without a singularity. Therefore, due to the path integral, the entire wave function can conserve information. Since an oscillating shell can tunnel after a number of oscillations, in the end, it will allow an infinite number of different branchings to classical histories. This system can be a good model of the effective loss of information, where information is conserved by a solution that is originated from gauge fields.

We study scaling and renormalization in two dimensional quantum gravity in a covariant framework. After reviewing the definition of a proper path integral measure, we use scaling arguments to rederive the Knizhnik-Polyakov-Zamolodchikov relations, the fractal dimension of the theory and the scaling of the reparametrization-invariant two point function. Then we compute the scaling exponents entering in these relations by means of the functional renormalization group. We show that a key ingredient to obtain the correct results already known from Liouville theory is the use of the exponential parametrization for metric fluctuations. We also show that with this parametrization we can recover the correct finite part of the effective action as the $\epsilon \to 0$ limit of quantum gravity in $d=2+\epsilon$.

We study how quantum fluctuations of the metric in covariant Horava-Lifshitz gravity influence the propagation of classical fields (complex scalar and photon). The effective Lorentz symmetry violation induced by the breaking of four-dimensional diffeomorphism is then evaluated, by comparing the dressed dispersion relations for both external fields. The constraint of a vanishing three-dimensional Ricci scalar is imposed in the path integral, which therefore explicitly depends on two propagating gravitational degrees of freedom only. Because the matter fields are classical, the present model contains only logarithmic divergences. Furthermore, it imposes the characteristic Horava-Lifshitz scale, to be smaller than ${10}^{10}\mathrm{GeV}$, if one wishes not to violate the current bounds on Lorentz symmetry violation.

We investigate two classes of models of quintessential inflation, based upon canonical as well as noncanonical scalar fields. In particular, introducing potentials steeper than the standard exponential, we construct models that can give rise to a successful inflationary phase, with signatures consistent with Planck 2015 results. Additionally, using nonminimal coupling of the scalar field with massive neutrino matter, we obtain the standard thermal history of the Universe, with late-time cosmic acceleration as the last stage of evolution. In both cases, inflation and late-time acceleration are connected by a tracker solution.

Cosmic strings are expected to form loops. These can act as seeds for accretion of dark matter, leading to the formation of ultracompact minihalos (UCMHs). We perform a detailed study of the accretion of dark matter onto cosmic string loops and compute the resulting mass distribution of UCMHs. We then apply observational limits on the present-day abundance of UCMHs to derive corresponding limits on the cosmic string tension $G\mu$. The bounds are strongly dependent upon the assumed distribution of loop velocities and their impacts on UCMH formation. Under the assumption that a loop can move up to a thousand times its own radius and still form a UCMH, we find a limit of $G\mu \le 1\times {10}^{-7}$. We show, in opposition to previous results, that strong limits on the cosmic string tension are not obtainable from UCMHs when more stringent (and realistic) requirements are placed on loop velocities.

In this Reply, we respond to the Comment [Phys. Rev. D 92, 018501 (2015)]. Our computation [Phys. Rev. D 91, 074512 (2015)] only took into account pure QCD effects, arising from quark mass differences, so it is not surprising that there are discrepancies in isospin splittings and in the $\mathrm{\Sigma }\text{−}\mathrm{\Lambda }$ mixing angle. We expect that these discrepancies will be smaller in a full calculation incorporating QED effects.

A recent lattice QCD (LQCD) calculation of $\mathrm{\Sigma }\text{−}\mathrm{\Lambda }$ mixing by the QCDSF-UKQCD Collaboration [Phys. Rev. D 91, 074512 (2015)] finds a mixing angle about half of that found from the Dalitz–Von Hippel (DvH) flavor SU(3) mass formula which relates the $\mathrm{\Sigma }\text{−}\mathrm{\Lambda }$ mixing matrix element to known octet baryon mass differences and which has been used widely to evaluate charge symmetry breaking effects in $\mathrm{\Lambda }$ hypernuclei. We show that the LQCD-calculated $\mathrm{\Sigma }\text{−}\mathrm{\Lambda }$ mixing matrix element and octet baryon masses satisfy the DvH mass formula, concluding thereby that a good LQCD evaluation of $\mathrm{\Sigma }\text{−}\mathrm{\Lambda }$ mixing requires an equally good reproduction of octet baryon mass differences which is yet to be demonstrated.

Following the 12 GeV upgrade, a dedicated experiment is planned with the Hall B CLAS12 detector at Jefferson Laboratory, with the aim to study electroproduction of nucleon resonances at high photon virtualities up to $Q^2=12{\mathrm{GeV}}^2$. In this work we present a QCD-based approach to the theoretical interpretation of these upcoming results in the framework of light cone sum rules that combine perturbative calculations with dispersion relations and duality. The form factors are thus expressed in terms of $N^{*}(1535)$ light-front wave functions at small transverse separations, called distribution amplitudes. The distribution amplitudes can therefore be determined from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. The results of the corresponding next-to-leading order calculation are presented and compared with the existing data. We find that the form factors are dominated by the twist-four distribution amplitudes that are related to the $\mathit{p}$-wave three-quark wave functions of the $N^{*}(1535)$, i.e. to contributions of orbital angular momentum.

Under rather generic assumptions, we show that, in asymmetric dark matter (ADM) scenarios in which the ADM sector was in chemical equilibrium with the standard model sector in early epochs, the sign of the $\mathrm{B}-\mathrm{L}$ asymmetry stored in the dark matter sector and the standard model sector are always the same. One particularly striking consequence of this result is that, when such an ADM decays or annihilates in the present universe, the resulting final state always involves an antineutrino. As a concrete example, we construct a composite ADM model and explore the feasibility of detecting such an antineutrino signal in atmospheric neutrino detectors.

In the context of an exactly soluble out of equilibrium (quenched) model, we study an extension of the fluctuation-dissipation relation. This involves a modified differential form of this relation, with an effective temperature which may have an explicit dependence on time scales.

We calculate finite-temperature corrections to the decay rate of a generic neutral (pseudo)scalar particle that decays into (pseudo)scalars or fermion-antifermion pairs. The ratio of the finite-temperature decay rate to the zero-temperature decay rate is presented. Thermal effects are largest in the limit where the decaying particle is nonrelativistic but with a mass well below the background temperature, but significant effects are possible even when we relax the former assumption. Thermal effects are reduced for the case of nonzero momentum of the decaying particle. We discuss cosmological scenarios under which significant finite-temperature corrections to the decay rate can be achieved.

Nonminimal matter couplings have recently been considered in the context of massive gravity and multigravity. These couplings are free of the Boulware-Deser ghost in the decoupling limit and can thus be considered within an effective field theory setup. Beyond the decoupling limit the ghost was shown to reemerge in the metric formulation of the theory. Recently it was argued that this pathology is absent when formulated in terms of unconstrained vielbeins. We investigate this possibility and show that the Boulware-Deser ghost is always present beyond the decoupling limit in any dimension larger than 2. We also show that the metric and vielbein formulations have an identical ghost-free decoupling limit. Finally we extend these arguments to more generic multigravity theories and argue that for any dimension larger than 2 a ghost is also present in the vielbein formulation whenever the symmetric vielbein condition is spoiled and the equivalence with the metric formulation is lost.

We study an electric field created by a static electric charge near the higher-dimensional Reissner-Nordström black hole. The relation between the static Green functions on the $D$-dimensional Reissner-Nordström background and on the $(D+2)$-dimensional homogeneous Bertotti-Robinson spacetime is found. Using the biconformal symmetry we obtain a simple integral representation for the static Maxwell Green functions in arbitrary dimensions. We show that in a four-dimensional spacetime the static Green function obtained by the biconformal method correctly reproduces known results. We also find a closed form for the exact static Green functions and vector potentials in the five-dimensional Reissner-Nordström spacetime.

A check of the validity of the distance-duality relation (DDR) is necessary since a violation of one of the assumptions underlying this relation might be possible. In this paper, we test the DDR by combining the Union2.1 type Ia supernovae (SNIa) and five angular diameter distance data from the baryonic acoustic oscillation (BAO) measurements. We find that the DDR is consistent with the observations at the $2\sigma$ confidence level (CL) for the case of the Hubble constant $h=0.7$, and the consistency is improved to be $1\sigma$ CL when $h=0.7$ is replaced by the latest constraint from the Planck satellite, i.e., $h=0.678$, or $h$ is marginalized. Our results show that the BAO measurement is a very powerful tool to test the DDR. With more and more BAO data being released in the future, we are expecting a better validity check of the DDR.

We study force-free magnetospheres in the Blandford-Znajek process from rapidly rotating black holes by adopting the near horizon geometry of near-extreme Kerr black holes (near-NHEK). It is shown that the Znajek regularity condition on the horizon can be directly derived from the resulting stream equation. In terms of the condition, we split the full stream equation into two separate equations. Approximate solutions around the rotation axis are derived. They are found to be consistent with previous solutions obtained in the asymptotic region. The solutions indicate energy and angular-momentum extraction from the hole.

The onset of electron captures by nuclei in dense matter, which is known to limit the stability of the most massive white dwarfs, is studied considering that electrons are interacting with an ionic mixture and allowing for the presence of a strong magnetic field. To this end, the instability condition traditionally formulated in the context of the simple Chandrasekhar model is generalized. General analytical expressions for the threshold mass density and pressure are obtained in the ultrarelativistic regime in the absence of magnetic fields, and in the limiting case of strongly quantizing magnetic fields. Numerical results are also presented for different stellar compositions and magnetic field strengths. The threshold density and pressures are found to be increased due to electron-ion interactions, and the heavier the elements the larger this shift: from less than 13% for elements lighter than magnesium, up to 23% for iron. The resulting increase of the maximum white dwarf mass turns out to be more important than that due to general relativity for stars made of heavy elements like sulfur, calcium and iron. Nevertheless, the overall effect amounts to about 2% at most. Electron captures accompanying pycnonuclear fusion reactions may have a more substantial impact. Moreover, the onset of electron captures is found to be shifted to either higher or lower densities in the presence of a strong magnetic field. In the strongly quantizing regime, the threshold density and pressure increase almost linearly with the magnetic field strength. The implications for magnetic white dwarfs are briefly discussed.

We derive an analytic expression for one-loop effective action of $\mathrm{QCD}+\mathrm{QED}$ at zero and finite temperatures by using the Schwinger proper time method. The result is a nonlinear effective action not only for electromagnetic and chromo-electromagnetic fields but also for the Polyakov loop, and thus reproduces the Euler-Heisenberg action in QED, QCD, and $\mathrm{QED}+\mathrm{QCD}$, and also the Weiss potential for the Polyakov loop at finite temperature. As applications of this “Euler-Heisenberg-Weiss” action in $\mathrm{QCD}+\mathrm{QED}$, we investigate quark pair productions induced by $\mathrm{QCD}+\mathrm{QED}$ fields at zero temperature and the Polyakov loop in the presence of strong electromagnetic fields. Quark one-loop contribution to the effective potential of the Polyakov loop explicitly breaks the center symmetry, and is found to be enhanced by the magnetic field, which is consistent with the inverse magnetic catalysis observed in lattice QCD simulation.