A recent proposal to connect the loop quantization with the spin foam model for cosmology via the path integral is hereby adapted to the case of mechanical systems within the framework of the so-called polymer quantum mechanics. The mechanical models we consider are deparametrized and thus the group averaging technique is used to deal with the corresponding constraints. The transition amplitudes are written in a vertex expansion form used in the spin foam models, where here a vertex is actually a jump in position. Polymer propagators previously obtained by spectral methods for a nonrelativistic polymer particle, both free and in a box, are regained with this method and as a new result we obtain the polymer propagator of the relativistic particle. All of them reduce to their standard form in the continuum limit for which the length scale parameter of the polymer quantization is taken to be small. Our results are robust thanks to their analytic and exact character which in turn come from the fact that presented models are solvable. They lend support to the vertex expansion scheme of the polymer path integral explored before in a formal way for cosmological models. Some possible future developments are commented upon in the discussion.

We investigate the strong gravitational lensing for black holes with scalar charge in massive gravity. We find that the scalar charge and the type of the black hole significantly affect the radius of the photon sphere, deflection angle, angular image position, angular image separation, relative magnifications, and time delay in strong gravitational lensing. Our results can be reduced to those of the Schwarzschild and Reissner-Nordström black holes in some special cases.

We focus on the massive gauge theory formulation of axion monodromy inflation. We argue that a gauge symmetry hidden in these models is the key mechanism protecting inflation from dangerous field theory and quantum gravity corrections. The effective theory of large-field inflation is dual to a massive $U(1)$ 4-form gauge theory, which is similar to a massive gauge theory description of superconductivity. The gauge theory explicitly realizes the old Julia-Toulouse proposal for a low-energy description of a gauge theory in a defect condensate. While we work mostly with the example of quadratic axion potential induced by flux monodromy, we discuss how other types of potentials can arise from the inclusion of gauge-invariant corrections to the theory.

Gravitational waves (GWs) generated by axisymmetric rotating collapse, bounce, and early postbounce phases of a galactic core-collapse supernova are detectable by current-generation gravitational wave observatories. Since these GWs are emitted from the quadrupole-deformed nuclear-density core, they may encode information on the uncertain nuclear equation of state (EOS). We examine the effects of the nuclear EOS on GWs from rotating core collapse and carry out 1824 axisymmetric general-relativistic hydrodynamic simulations that cover a parameter space of 98 different rotation profiles and 18 different EOS. We show that the bounce GW signal is largely independent of the EOS and sensitive primarily to the ratio of rotational to gravitational energy, $T/|W|$, and at high rotation rates, to the degree of differential rotation. The GW frequency ($f_{\text{peak}}\sim 600–1000\mathrm{Hz}$) of postbounce core oscillations shows stronger EOS dependence that can be parametrized by the core’s EOS-dependent dynamical frequency $\sqrt{G{\overline{\rho }}_c}$. We find that the ratio of the peak frequency to the dynamical frequency $f_{\text{peak}}/\sqrt{G\overline{{\rho }_c}}$ follows a universal trend that is obeyed by all EOS and rotation profiles and that indicates that the nature of the core oscillations changes when the rotation rate exceeds the dynamical frequency. We find that differences in the treatments of low-density nonuniform nuclear matter, of the transition from nonuniform to uniform nuclear matter, and in the description of nuclear matter up to around twice saturation density can mildly affect the GW signal. More exotic, higher-density physics is not probed by GWs from rotating core collapse. We furthermore test the sensitivity of the GW signal to variations in the treatment of nuclear electron capture during collapse. We find that approximations and uncertainties in electron capture rates can lead to variations in the GW signal that are of comparable magnitude to those due to different nuclear EOS. This emphasizes the need for reliable experimental and/or theoretical nuclear electron capture rates and for self-consistent multidimensional neutrino radiation-hydrodynamic simulations of rotating core collapse.

Light is the richest information retriever for most physical systems, particularly so for astronomy and cosmology, in which gravitation is of paramount importance, and also for solid state defects and metamaterials, in which some effects can be mimicked by non-Euclidean or even non-Riemannian geometries. Thus, it is expedient to probe light motion in geometrical backgrounds alternative to that of general relativity. Here we investigate this issue in generic metric-affine theories and derive (i) the expression, in the geometrical optics (eikonal) limit, for light trajectories, showing that they still are null (extremal) geodesics and thus, in general, no longer autoparallels, (ii) a generic formula to obtain the relation between source (galaxy) and reception (observer) angular size (area) distances, generalizing Etherington’s original distance reciprocity relation (DRR), and then applying it to two particular representative non-Riemannian geometries. First in metric-compatible, completely antisymmetric torsion geometries, the generalized DRR is not changed at all, and then in Weyl integrable spacetimes, the generalized DRR assumes a specially simple expression.

In this paper, we present the results from phenomenological analysis of $Z$-boson pair hard diffractive production at the LHC. The calculation is based on the Regge factorization approach. Diffractive parton density functions extracted by the H1 Collaboration at DESY-HERA are used. The multiple Pomeron exchange corrections are considered through the rapidity gap survival probability factor. We give numerical predictions for single diffractive as well as double Pomeron exchange cross sections and compare with the photon-induced and nondiffractive ones. The contributions from quark-antiquark collision and gluon-gluon fusion are displayed. Various kinematical distributions are presented. We make predictions which could be compared to future measurements at the LHC, where forward proton detectors are installed and detector acceptances are considered.

We improve and extend our study of the complex in-medium heavy-quark potential and its Debye mass $m_D$ in a gluonic medium with a finer scan around the deconfinement transition and newly generated ensembles closer to the thermodynamic limit. On the lattices with larger physical volume, $\mathrm{Re}[\mathrm{V}]$ shows signs of screening, i.e. a finite $m_D$, only in the deconfined phase, reminiscent of a genuine phase transition. Consistently $\mathrm{Im}[\mathrm{V}]$ exhibits nonzero values also only above $T_C$. We compare the behavior of $\mathrm{Re}[\mathrm{V}]$ with the color singlet free energies that have been used historically to extract the Debye mass. An effective coupling constant is computed to assess the residual influence of the confining part of the potential at $T>0$. Our previous finding of a gradual screening of $\mathrm{Re}[\mathrm{V}]$ around $T_C$ on finer lattices is critically reassessed and interpreted to originate from finite volume artifacts. We discuss that deficiency of the $\beta =7$, ${\xi }_b=3.5$ parameter set at $N_s=32$, which has been in deployed in the literature before.

We present a calculation of the $\eta \text{−}{\eta }^{\prime }$ mixing in the framework of large-$N_c$ chiral perturbation theory. A general expression for the $\eta \text{−}{\eta }^{\prime }$ mixing at next-to-next-to-leading order (NNLO) is derived, including higher-derivative terms up to fourth order in the 4-momentum, kinetic terms, and mass terms. In addition, the axial-vector decay constants of the $\eta \text{−}{\eta }^{\prime }$ system are determined at NNLO. The numerical analysis of the results is performed successively at leading order, next-to-leading order, and NNLO. We investigate the influence of one-loop corrections, Okubo-Zweig-Iizuka rule-violating parameters, and $\mathcal{O}(N_c{p}^6)$ contact terms.

This paper is a continuation of a previous work where we presented a unified two-fermion covariant scheme which produced very precise results for the masses of light and heavy mesons. We extend the analysis to some radiative decays of mesons $\mathrm{\Upsilon }$, ${\chi }_{b2}$, $h_b$, ${\chi }_{b1}$, ${\chi }_{b0}$, and ${\eta }_b$, and we calculate their branching ratios and their widths. For most of them, we can make a comparison with experimental data, finding a good agreement. For the decays for which data are not available, we compare ours with other recent theoretical previsions.

Double field theory (DFT) is a low-energy effective theory of a manifestly $O(D,D)$-invariant formulation of the closed-string theory. The theory is based on a doubling of the $D$-dimensional spacetime structure and, in order to preserve the gauge symmetry provided by the invariance under generalized diffeomorphisms, a constraint has to be imposed on fields and gauge parameters. In this paper, we consider a DFT-inspired supergravity by using a suitable commutative star product of fields and gauge parameters with the aim of studying the corresponding algebraic structure. This star product is not associative, implying the nonclosure of the gauge transformations. Despite this, we get a consistent theory in which an orthogonality condition of momenta associated with double fields is also necessary to have a closed gauge algebra. We first start from the simplest case of one compact spatial dimension. Then, the extension to the case of $d$ spatial dimensions is taken into consideration.

Adiabatic regularization for quantum field theory in conformally flat spacetime is known for scalar and Dirac fermion fields. In this paper, we complete the construction by establishing the adiabatic regularization scheme for the gauge field. We show that the adiabatic expansion for the mode functions and the adiabatic vacuum can be defined in a similar way using Wentzel-Kramers-Brillouin-type (WKB-type) solutions as the scalar fields. As an application of the adiabatic method, we compute the trace of the energy momentum tensor and reproduce the known result for the conformal anomaly obtained by the other regularization methods. The availability of the adiabatic expansion scheme for the gauge field allows one to study various renormalized physical quantities of theories coupled to (non-Abelian) gauge fields in conformally flat spacetime, such as conformal supersymmetric Yang Mills, inflation, and cosmology.

We evaluate the Hadamard function, the vacuum expectation values (VEVs) of the field squared and the energy-momentum tensor for a massive scalar field with a general curvature coupling parameter in the geometry of two parallel plates on a spatially flat Friedmann-Robertson-Walker background with a general scale factor. On the plates, the field operator obeys the Robin boundary conditions with the coefficients depending on the scale factor. In all the spatial regions, the VEVs are decomposed into the boundary-free and boundary-induced contributions. Unlike the problem with the Minkowski bulk, in the region between the plates, the normal stress is not homogeneous and does not vanish in the geometry of a single plate. Near the plates, it has different signs for accelerated and decelerated expansions of the Universe. The VEV of the energy-momentum tensor, in addition to the diagonal components, has a nonzero off-diagonal component describing an energy flux along the direction normal to the boundaries. Expressions are derived for the Casimir forces acting on the plates. Depending on the Robin coefficients and on the vacuum state, these forces can be either attractive or repulsive. An important difference from the corresponding result in the Minkowski bulk is that the forces on the separate plates, in general, are different if the corresponding Robin coefficients differ. We give the applications of general results for the class of $\alpha$ vacua in the de Sitter bulk. It is shown that, compared with the Bunch-Davies vacuum state, the Casimir forces for a given $\alpha$ vacuum may change the sign.

The era of gravitational-wave astronomy started with the discovery of the binary black hole coalescences (BBH) GW150914 and GW151226 by the LIGO instruments. These systems allowed for the first direct measurement of masses and spins of black holes. The component masses in each of the systems have been estimated with uncertainties of over 10%, with only weak constraints on the spin magnitude and orientation. In this paper we show how these uncertainties are typical for this type of source when using advanced detectors. Focusing, in particular, on heavy BBH of masses similar to GW150914, we find that typical uncertainties in the estimation of the source-frame component masses will be around 40%. We also find that for most events the magnitude of the component spins will be estimated poorly: for only 10% of the systems, the uncertainties in the spin magnitude of the primary (secondary) BH will be below 0.7 (0.8). Conversely, the effective inspiral spin along the angular momentum can be estimated more precisely than either spins, with uncertainties below 0.16 for 10% of the systems. We also quantify how often large or negligible primary spins can be excluded and how often the sign of the effective spin can be measured. We show how the angle between the spin and the orbital angular momentum can only seldom be measured with uncertainties below 60 °. We then investigate how the measurement of spin parameters depends on the inclination angle and the total mass of the source. We find that when precession is present, uncertainties are smaller for systems observed close to edge-on. Contrarily to what happens for low-mass, inspiral-dominated sources, for heavy BBH we find that large spins aligned with the orbital angular momentum can be measured with a small uncertainty. We also show how spin uncertainties increase with the total mass. Finally, considering a simple toy model, we show how detections can be combined to infer properties of the underlying population.

The two binary black hole (BBH) coalescences detected by LIGO, GW150914, and GW151226, were relatively nearby sources, with a redshift of $\sim 0.1$. As the sensitivity of Advanced LIGO and Virgo increases in the next few years, they will eventually detect stellar-mass BBHs up to redshifts of $\sim 1$. However, these are still relatively small distances compared with the size of the Universe, or with those encountered in most areas of astrophysics. In order to study BBH during the epoch of reionization, or black holes born from population III stars, more sensitive instruments are needed. Third-generation gravitational-wave detectors, such as the Einstein Telescope or the Cosmic Explorer, are already in an advanced R&D stage. These detectors will be roughly a factor of 10 more sensitive in strain than the current generation, and they will be able to detect BBH mergers beyond a redshift of 20. In this paper we quantify the precision with which these new facilities will be able to estimate the parameters of stellar-mass, heavy, and intermediate-mass BBHs as a function of their redshifts and the number of detectors. We show that having only two detectors would result in relatively poor estimates of black hole intrinsic masses: a situation improved with three or four instruments. Larger improvements are visible for the sky localization, although it is not yet clear whether BBHs are luminous in the electromagnetic or neutrino band. The measurement of the spin parameters, on the other hand, does not improve significantly as more detectors are added to the network since redshift information is not required to measure spin.

We investigate a new class of scalar multi-Galileon models, which is not included in the commonly admitted general formulation of generalized multi-Galileons. The Lagrangians of this class of models, some of them having already been introduced in previous works, are specific to multi-Galileon theories, and vanish in the single Galileon case. We examine them in detail, discussing in particular some hidden symmetry properties which can be made explicit by adding total derivatives to these Lagrangians. These properties allow us to describe the possible dynamics for these new Lagrangians in the case of multi-Galileons in the fundamental representation of a $\mathrm{SO}(N)$ and $\mathrm{SU}(N)$ global symmetry group, as well as in the adjoint representation of a $\mathrm{SU}(N)$ global symmetry group. We perform in parallel an exhaustive examination of some of these models, finding a complete agreement with the dynamics obtained using the symmetry properties. Finally, we conclude by discussing what could be the most general multi-Galileon theory, as well as the link between scalar and vector multi-Galileon models.

We show that the radial acceleration relation for rotationally supported galaxies may be explained, in the absence of cold dark matter, by a nonminimally coupled scalar field, whose fifth forces are partially screened on galactic scales by the symmetron mechanism. In addition, we show that sufficient energy is stored in the symmetron field to explain the dynamic stability of galactic disks.

In the present work, we investigate wormhole structures and the energy conditions supporting them in Einstein-Cartan theory. The matter content consists of a Weyssenhoff fluid along with an anisotropic matter which together generalize the anisotropic energy momentum tensor in general relativity (GR) to include spin effects. Assuming that the radial pressure and energy density obey a linear equation of state, we introduce exact asymptotically flat and anti–de-Sitter spacetimes that admit traversable wormholes and respect energy conditions. Such wormhole solutions are studied in detail for two specific forms for the redshift function, namely a constant redshift function and the one with power law dependency.

We present cosmological constraints from the combination of the full mission nine-year WMAP release and small-scale temperature data from the pre-Planck Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) generation of instruments. This is an update of the analysis presented in Calabrese et al. [Phys. Rev. D 87, 103012 (2013)], and highlights the impact on $\mathrm{\Lambda }\mathrm{CDM}$ cosmology of a 0.06 eV massive neutrino—which was assumed in the Planck analysis but not in the ACT/SPT analyses—and a Planck-cleaned measurement of the optical depth to reionization. We show that cosmological constraints are now strong enough that small differences in assumptions about reionization and neutrino mass give systematic differences which are clearly detectable in the data. We recommend that these updated results be used when comparing cosmological constraints from WMAP, ACT and SPT with other surveys or with current and future full-mission Planck cosmology. Cosmological parameter chains are publicly available on the NASA’s LAMBDA data archive.

We examine the effect of the stress tensor of a quantum matter field, such as the electromagnetic field, on the spectrum of primordial gravity waves expected in inflationary cosmology. We find that the net effect is a small reduction in the power spectrum, especially at higher frequencies, but which has a different form from that described by the usual spectral index. Thus, this effect has a characteristic signature, and is, in principle, observable. The net effect is a sum of two contributions, one of which is due to quantum fluctuations of the matter field stress tensor. The other is a quantum correction to the graviton field due to coupling to the expectation value of this stress tensor. Both contributions are sensitive to initial conditions in the very early universe, so this effect has the potential to act as a probe of these initial conditions.

We investigate the bounce and cyclicity realization in the framework of weakly broken Galileon theories. We study bouncing and cyclic solutions at the background level, reconstructing the potential and the Galileon functions that can give rise to a given scale factor and presenting analytical expressions for the bounce requirements. We proceed to a detailed investigation of the perturbations, which after crossing the bouncing point give rise to various observables, such as the scalar and tensor spectral indices and the tensor-to-scalar ratio. Although the scenario at hand shares the disadvantage of all bouncing models, namely that it provides a large tensor-to-scalar ratio, introducing an additional light scalar significantly reduces it through the kinetic amplification of the isocurvature fluctuations.