We introduce a new technique for dealing with the matrix elements of the Hamiltonian operator in loop quantum gravity, based on the use of intertwiners projected on coherent states of angular momentum. We give explicit expressions for the projections of intertwiners on the spin coherent states in terms of complex numbers describing the unit vectors which label the coherent states. Operators such as the Hamiltonian can then be reformulated as differential operators acting on polynomials of these complex numbers. This makes it possible to describe the action of the Hamiltonian geometrically, in terms of the unit vectors originating from the angular momentum coherent states, and opens up a way towards investigating the semiclassical limit of the dynamics via asymptotic approximation methods.

We use the method of characteristics to study superluminal graviton (which we call the swift graviton) propagation in theories of higher-curvature gravity of the form $(\text{Riemann}{)}^2$, $(\text{Riemann}{)}^3$, ${\nabla }^2(\text{Riemann}{)}^2$ and $(\text{Riemann}{)}^4$. We consider a $pp$-wave background. When probed by gravitons with an appropriate polarization, several of the gravitational theories under consideration exhibit characteristic hypersurfaces outside the flat spacetime light cone.

An algorithm is used to generate new solutions of the scalar-field equations in homogeneous and isotropic universes. Solutions can be found for pure scalar fields with various potentials in the absence and presence of spatial curvature and other perfect fluids. A series of generalizations of the Chaplygin gas and bulk viscous cosmological solutions for inflationary universes are found. Furthermore other closed-form solutions which provide inflationary universes are presented. We also show how the Hubble slow-roll parameters can be calculated using the solution algorithm and we compare these inflationary solutions with the observational data provided by the Planck 2015 collaboration in order to constrain and rule out some of these models.

We present the results of a cross-correlation search for gravitational waves from SNR 1987A using the second year of LIGO science run 5 data. The frequency band 75–450 Hz is searched. No evidence of gravitational waves is found. A 90% confidence upper limit of $h_0\le 3.8\times {10}^{-25}$ is placed on the gravitational-wave strain at the most sensitive frequency near 150 Hz. This corresponds to an ellipticity of $\epsilon \le 8.2\times {10}^{-4}$ and improves on previously published strain upper limits by a factor of approximately 4. We perform a comprehensive suite of validations of the search algorithm and identify several computational savings that marginally sacrifice sensitivity in order to streamline the parameter space being searched. We estimate detection thresholds and sensitivities through Monte Carlo simulations.

We point out that a distinctive monotop signature is present in natural supersymmetry scenarios when a scalar top quark and Higgsinos are almost mass degenerate. This signature originates from a supersymmetric counterpart of the $t\overline{t}H$ process, i.e. $pp\to \tilde{t}t\tilde{h}$. Unlike monojet signatures exploiting initial state radiation, this channel can be regarded as a clear signature of a light stop and Higgsinos, allowing a direct probe of the stop and neutralino sectors. The production rate of this channel largely depends on the up-type Higgsino components in the neutralinos while the stop sector is sensitive to angular distributions of the top-quark’s decay products. We develop an optimal search strategy to capture the supersymmetric $t\overline{t}H$ process and find that a high luminosity LHC can probe the stop and Higgsino sectors with $m_{{\tilde{t}}_1}\lesssim 380\mathrm{GeV}$ and $m_{{\tilde{t}}_1}-m_{{\tilde{\chi }}_1^0}\lesssim m_W$. Additionally, we propose a kinematic variable with which one can measure the stop mixing in this channel.

We derive the electric permittivity $\epsilon$ and magnetic permeability ${\mu }_M$ of the quark-gluon plasma (QGP) with the kinetic theory associated with a Bhatnagar-Gross-Krook (BGK) collisional kernel. Based on them, we study the effect of collisions on the refractive index of QGP. Compared to the collisionless case, collisions change the $\omega$-behavior of $\epsilon$ and ${\mu }_M$ dramatically, which is responsible for the fact that the real and imaginary parts of $n^2$ and the Depine-Lakhtakia index $n_{\mathrm{DL}}$ are smooth functions of $\omega$. For a small collision rate $\nu$, the Depine-Lakhtakia index $n_{\mathrm{DL}}$ is negative in some frequency range. When the collision rate increases, the frequency range for $n_{\mathrm{DL}}<0$ becomes narrower. Numerical results show a critical collision rate $\nu \sim 0.2m_D$, above which the Depine-Lakhtakia index $n_{\mathrm{DL}}$ is positive for all frequency regions, which indicates a normal refractive index. In contrast to the collisionless case, there exists some frequency range in which $n_{\mathrm{DL}}<0$ and the propagating mode may satisfy the dispersion relation $n^2{\omega }^2=k^2$ simultaneously, which implies the existence of a negative refractive index.

We show that the braneworld rotating Kerr-Newman black hole and naked singularity spacetimes with both positive and negative braneworld tidal charge parameters can be separated into 14 classes according to the properties of circular geodesics governing the Keplerian accretion. We determine the efficiency of the Keplerian accretion disks for all braneworld Kerr-Newman spacetimes. We demonstrate the occurrence of an infinitely deep gravitational potential in Kerr-Newman naked singularity spacetimes having the braneworld dimensionless tidal charge $b\in (1/4,1)$ and the dimensionless spin $a\in (2\sqrt{b}-\sqrt{b(4b-1)}$, $2\sqrt{b}+\sqrt{b(4b-1)})$, implying unbound efficiency of the Keplerian accretion and the possibility of extracting the whole naked singularity mass. Therefore, we call them braneworld “mining-unstable” Kerr-Newman naked singularity spacetimes. Fundamental restriction on the relevance of the extraordinary—but fully classical—phenomenon of the mining instability is given by validity of the assumption of geodesic motion of the accreting matter.

Collaborative international efforts under the name of the Event Horizon Telescope project, using sub-mm very long baseline interferometry, are soon expected to provide the first images of the shadow cast by the candidate supermassive black hole in our Galactic center, Sagittarius A*. Observations of this shadow would provide direct evidence of the existence of astrophysical black holes. Although it is expected that astrophysical black holes are described by the axisymmetric Kerr solution, there also exist many other black hole solutions, both in general relativity and in other theories of gravity, which cannot presently be ruled out. To this end, we present calculations of black hole shadow images from various metric theories of gravity as described by our recent work on a general parametrization of axisymmetric black holes [R. Konoplya, L. Rezzolla, and A. Zhidenko, Phys. Rev. D 93, 064015 (2016).]. An algorithm to perform general ray-tracing calculations for any metric theory of gravity is first outlined and then employed to demonstrate that even for extremal metric deformation parameters of various black hole spacetimes, this parametrization is both robust and rapidly convergent to the correct solution.

Recent observational progress has led to the establishment of the standard $\mathrm{\Lambda }\mathrm{CDM}$ model for cosmology. This development is based on different cosmological probes that are usually combined through their likelihoods at the latest stage in the analysis. We implement here an integrated scheme for cosmological probes, which are combined in a common framework starting at the map level. This treatment is necessary as the probes are generally derived from overlapping maps and are thus not independent. It also allows for a thorough test of the cosmological model and of systematics through the consistency of different physical tracers. As a first application, we combine current measurements of the cosmic microwave background (CMB) from the Planck satellite, and galaxy clustering and weak lensing from SDSS. We consider the spherical harmonic power spectra of these probes including all six auto- and cross-correlations along with the associated full Gaussian covariance matrix. This provides an integrated treatment of different analyses usually performed separately including CMB anisotropies, cosmic shear, galaxy clustering, galaxy-galaxy lensing and the integrated Sachs-Wolfe effect with galaxy and shear tracers. We derive constraints on $\mathrm{\Lambda }\mathrm{CDM}$ parameters that are compatible with existing constraints and highlight tensions between data sets, which become apparent in this integrated treatment. We discuss how this approach provides a complete and powerful integrated framework for probe combination and how it can be extended to include other tracers in the context of current and future wide-field cosmological surveys.

After the discovery of the Higgs boson, understanding the nature of electroweak symmetry breaking and the associated electroweak phase transition has become the most pressing question in particle physics. Answering this question is a priority for experimental studies. Data from the LHC and future lepton collider-based Higgs factories may uncover new physics coupled to the Higgs boson, which can induce the electroweak phase transition to become first order. Such a phase transition generates a stochastic background of gravitational waves, which could potentially be detected by a space-based gravitational wave interferometer. In this paper, we survey a few classes of models in which the electroweak phase transition is strongly first order. We identify the observables that would provide evidence of these models at the LHC and next-generation lepton colliders, and we assess whether the corresponding gravitational wave signal could be detected by eLISA. We find that most of the models with first-order electroweak phase transition can be covered by the precise measurements of Higgs couplings at the proposed Higgs factories. We also map out the model space that can be probed with gravitational wave detection by eLISA.

A classically scale invariant (CSI) extension of the standard model (SM) induces radiative electroweak symmetry breaking and predicts anomalously large Higgs self-interactions. Hence, $W_L{W}_L$ scattering processes can be a good probe of the symmetry breaking mechanism. We develop a theoretical framework for perturbative computation and calculate $WW$ scattering amplitudes in a CSI model. We show that $W_L{W}_L$ scattering amplitudes satisfy the equivalence theorem and that a large deviation of $W_L{W}_L$ differential cross sections from the SM predictions is predicted depending on the c.m. energy and scattering angle. The results are more accurate than those based on the effective-potential approach. A prescription to implement predictions of the CSI model to Monte Carlo event generators is also presented.

In the present work we consider the phenomenological consequences of a predictive formulation of the Nambu–Jona-Lasinio (NJL) model at the one loop level of perturbative calculations. The investigation reported here can be considered as an extension of previously made ones on the same issue. In the study made in this work we have included vector and tensor couplings, simultaneously, as well as $SU(2)$ isospin symmetry breaking terms. As a consequence of the last ingredient mentioned, there are different masses in the model amplitudes. In spite of this, within the context of the adopted procedure, we verify that it is possible to eliminate unphysical dependencies on the arbitrary choices for the routing of internal lines momenta as well as Ward identities violating contributions and scale ambiguous terms, from the corresponding one loop amplitudes, through the simple and universal Consistency Relations. The total content of divergence of the amplitudes is reduced to only two basic divergent objects. They are related to two inputs of the model in a way that, due to their scale properties, an unique arbitrariness remains. However, due to the critical condition found in the mechanism which generates the constituent quark mass, within our approach, this arbitrariness is also removed turning the model predictive in the sense that its phenomenological consequences is not dependent in possible choices made in intermediary steps of the calculations, as occurs in usual treatments. In this scenario, we investigate the most typical static properties of the scalar, pseudoscalar, vector and axial-vector mesons at low-energy. Special attention is given to the consequences of the $SU(2)$ isospin symmetry breaking for the phenomenological predictions. The implications of the tensor couplings for the model observables, which can be considered an original contribution of the present work, at the level of the content and not only in the form, is analyzed in a detailed way. The found values are in good accordance with the expectations and are globally consistent, having the obvious advantage that the predictions are not dependent in parameters aliens to the model Lagrangian as occurs in traditional approaches based in regularizations.

Motivated by the recent discoveries of binary black-hole mergers by the Advanced Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO), we investigate the prospects of ground-based detectors to perform a spectroscopic analysis of signals emitted during the ringdown of the final Kerr black hole formed by a stellar mass binary black-hole merger. Although it is unlikely that Advanced LIGO can measure multiple modes of the ringdown, assuming an optimistic rate of $240{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$, upgrades to the existing LIGO detectors could measure multiple ringdown modes in $\sim 6$ detections per year. New ground-based facilities such as Einstein Telescope or Cosmic Explorer could measure multiple ringdown modes in over 300 events per year. We perform Monte Carlo injections of $10^6$ binary black-hole mergers in a search volume defined by a sphere of radius 1500 Mpc centered at the detector, for various proposed ground-based detector models. We assume a uniform random distribution in component masses of the progenitor binaries, sky positions and orientations to investigate the fraction of the population that satisfies our criteria for detectability and resolvability of multiple ringdown modes. We investigate the detectability and resolvability of the subdominant modes $l=m=3$, $l=m=4$ and $l=2$, $m=1$. Our results indicate that the modes with $l=m=3$ and $l=2$, $m=1$ are the most promising candidates for subdominant mode measurability. We find that for stellar mass black-hole mergers, resolvability is not a limiting criteria for these modes. We emphasize that the measurability of the $l=2$, $m=1$ mode is not impeded by the resolvability criterion.

We compute the relation between heavy quark masses defined in the modified minimal subtraction and the on-shell schemes. Detailed results are presented for all coefficients of the $\mathrm{SU}(N_c)$ color factors. The reduction of the four-loop on-shell integrals is performed for a general QCD gauge parameter. Altogether there are about 380 master integrals. Some of them are computed analytically, others with high numerical precision using Mellin-Barnes representations, and the rest numerically with the help of FIESTA. We discuss in detail the precise numerical evaluation of the four-loop master integrals. Updated relations between various short-distance masses and the $\overline{\mathrm{MS}}$ quark mass to next-to-next-to-next-to-leading order accuracy are provided for the charm, bottom and top quarks. We discuss the dependence on the renormalization and factorization scale.

We argue that lepton flavor violating (LFV) decays $M\to {\ell }_1{\overline{\ell }}_2$ of quarkonium states $M$ with different quantum numbers could be used to put constraints on the Wilson coefficients of effective operators describing LFV interactions at low energy scales. We note that restricted kinematics of the two-body quarkonium decays allows us to select operators with particular quantum numbers, significantly reducing the reliance on the single operator dominance assumption that is prevalent in constraining parameters of the effective LFV Lagrangian. We shall also argue that studies of radiative lepton flavor violating $M\to \gamma {\ell }_1{\overline{\ell }}_2$ decays could provide important complementary access to those effective operators.

In order to imitate the anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in the low frequency limit shows a Drude peak and that, in the intermediate frequency regime, it reveals the power law behavior. Specifically, when the anisotropy increases, the exponent of the power law becomes smaller. In addition, we find that a critical value for the anisotropy exists at which the dc conductivity reaches to its maximum value.

We show that Friedmann-Robertson-Walker geometry with a flat spatial section in quantized (Wheeler deWitt quantization) Brans-Dicke (BD) theory reveals a rich phase structure owing to anomalous breaking of a classical symmetry, which maps the scale factor $a\mapsto \lambda a$ for some constant $\lambda$. In the weak coupling ($\omega$) limit, the theory goes from a symmetry preserving phase to a broken phase. The existence of a phase boundary is an obstruction to another classical symmetry [see V. Faraoni, Phys. Rev. D 59, 084021 (1999).] (which relates two BD theories with different couplings) admitted by BD theory with scale invariant matter content, i.e., ${T^{\mu }}_{\mu }=0$. Classically, this prohibits the BD theory from reducing to general relativity (GR) for scale invariant matter content. We show that a strong coupling limit of both BD and GR preserves the symmetry involving the scale factor. We also show that with scale invariant matter content (radiation, i.e., $P=\frac{1}{3}\rho$), the quantized BD theory does reduce to GR as $\omega \to \infty$, which is in sharp contrast to classical behavior. This is a first known illustration of a scenario where quantized BD theory provides an example of anomalous symmetry breaking and resulting binary phase structure. We make a conjecture regarding the strong coupling limit of the BD theory in a generic scenario.

We consider a scenario where the inflaton decays to a hidden sector thermally decoupled from the visible Standard Model sector. A tiny portal coupling between the hidden and the visible sectors later heats the visible sector so that the Standard Model degrees of freedom come to dominate the energy density of the Universe before big bang nucleosynthesis. We find that this scenario is viable, although obtaining the correct dark matter abundance and retaining successful big bang nucleosynthesis is not obvious. We also show that the isocurvature perturbations constituted by a primordial Higgs condensate are not problematic for the viability of the scenario.

In this work, we systematically study the strong decay behavior of the charmed mesons $D_1^{*}(2680)$, $D_3^{*}(2760)$, and $D_2^{*}(3000)$ reported by the LHCb Collaboration. By comparing the masses and the decay properties with the results of the experiment, we assign these newly observed mesons as the $2S\frac{1}{2}{1}^{-}$, $1D\frac{5}{2}{3}^{-}$, and $1F\frac{5}{2}{2}^{+}$ states, respectively. As a byproduct, we also study the strong decays of the unobserved $2P\frac{3}{2}{2}^{+}$, $2F\frac{5}{2}{2}^{+}$, and $3P\frac{3}{2}{2}^{+}$ charmed mesons, which is useful for future experiments in searching for these charmed mesons.

We present the first study of the process $J/\psi \to \gamma \eta {\pi }^0$ using $(223.7\pm 1.4)\times 10^6$ $J/\psi$ events accumulated with the BESIII detector at the BEPCII facility. The branching fraction for $J/\psi \to \gamma \eta {\pi }^0$ is measured to be $\mathcal{B}(J/\psi \to \gamma \eta {\pi }^0)=(2.14\pm 0.18(\text{stat})\pm 0.25(\text{syst}))\times 10^{-5}$. With a Bayesian approach, the upper limits of the branching fractions $\mathcal{B}(J/\psi \to \gamma a_0(980),a_0(980)\to \eta {\pi }^0)$ and $\mathcal{B}(J/\psi \to \gamma a_2(1320),a_2(1320)\to \eta {\pi }^0)$ are determined to be $2.5\times 10^{-6}$ and $6.6\times 10^{-6}$ at the 95% confidence level, respectively. All of these measurements are given for the first time.