We show that all algebraic type-$O$, type-$N$ and type-$D$ and some Kundt-type solutions of topologically massive gravity are inherited by its holographically well-defined deformation, that is, the recently found minimal massive gravity. This construction provides a large class of constant scalar curvature solutions to the theory. We also study the consistency of the field equations both in the source-free and matter-coupled cases. Since the field equations of MMG do not come from a Lagrangian that depends on the metric and its derivatives only, it lacks the Bianchi identity valid for all nonsingular metrics. But it turns out that for the solutions of the equations, the Bianchi identity is satisfied. This is a necessary condition for the consistency of the classical field equations but not a sufficient one, since the rank-two tensor equations are susceptible to double divergence. We show that for the source-free case the double divergence of the field equations vanishes for the solutions. In the matter-coupled case, we show that the double divergences on the left-hand side and the right-hand side are equal to each other for the solutions of the theory. This construction completes the proof of the consistency of the field equations.

We consider the Casimir interaction mediated by massless fermions, between a spherical defect and a flat potential barrier, assuming hard (bag-type) boundary conditions at both the barrier and the surface of the sphere. The computation of the quantum interaction energy is carried out using the multiple scattering approach adapted here to the setup in question. We find an exact integral formula for the energy, from which we extract both the large- and short-distance asymptotic behavior. At large distance the fermionic contribution is found to scale as $L^{-3}$, in contrast to that of electromagnetic vacuum fluctuations that, assuming perfectly conducting boundaries, scale as $L^{-4}$. At short distance, we compute the leading and subleading contribution to the vacuum energy. The leading one coincides with what it is expected from the proximity force approximation, while the subleading term gives, contrary to the electromagnetic case, a positive correction to the proximity force result.

We consider the decay of “false kinks,” that is, kinks formed in a scalar field theory with a pair of degenerate symmetry-breaking false vacua in $1+1$ dimensions. The true vacuum is symmetric. A second scalar field and a peculiar potential are added in order for the kink to be classically stable. We find an expression for the decay rate of a false kink. As with any tunneling event, the rate is proportional to $\exp (-S_E)$ where $S_E$ is the Euclidean action of the bounce describing the tunneling event. This factor varies wildly depending on the parameters of the model. Of interest is the fact that for certain parameters $S_E$ can get arbitrarily small, implying that the kink is only barely stable. Thus, while the false vacuum itself may be very long-lived, the presence of kinks can give rise to rapid vacuum decay.

We identify the quantum channels corresponding to the interaction of a Gaussian quantum state with an already formed Schwarzschild black hole. Using recent advances in the classification of one-mode bosonic Gaussian channels, we find that (with one exception) the black hole Gaussian channels lie in the nonentanglement breaking subset of the lossy channels $\mathcal{C}(\text{loss})$, amplifying channels $\mathcal{C}(\mathrm{amp})$ and classical-noise channels ${\mathcal{B}}_2$. We show that the channel parameters depend on the black hole mass and the properties of the potential barrier surrounding it. This classification enables us to calculate the classical and quantum capacity of the black hole and to estimate the quantum capacity where no tractable quantum capacity expression exists today. We discuss these findings in the light of the black hole quantum information loss problem.

Using the Batalin-Vilkovisky formalism, we study the Ward identities and the equations of gauge dependence in potentially anomalous general gauge theories, renormalizable or not. A crucial new term, absent in manifestly nonanomalous theories, is responsible for interesting effects. We prove that gauge invariance always implies gauge independence, which in turn ensures perturbative unitarity. Precisely, we consider potentially anomalous theories that are actually free of gauge anomalies thanks to the Adler-Bardeen theorem. We show that when we make a canonical transformation on the tree-level action, it is always possible to re-renormalize the divergences and re-fine-tune the finite local counterterms, so that the renormalized $\mathrm{\Gamma }$ functional of the transformed theory is also free of gauge anomalies, and is related to the renormalized $\mathrm{\Gamma }$ functional of the starting theory by a canonical transformation. An unexpected consequence of our results is that the beta functions of the couplings may depend on the gauge-fixing parameters, although the physical quantities remain gauge independent. We discuss nontrivial checks of high-order calculations based on gauge independence and determine how powerful they are.

We consider here a full study of stellar dynamics from the brane-world point of view in the case of constant density and of a polytropic fluid. We start our study cataloguing the minimal requirements to obtain a compact object with a Schwarzschild exterior, highlighting the low and high energy limit, the boundary conditions, and the appropriate behavior of Weyl contributions inside and outside of the star. Under the previous requirements we show an extensive study of stellar behavior, starting with stars of constant density and its extended cases with the presence of nonlocal contributions. Finally, we focus our attention to more realistic stars with a polytropic equation of state, especially in the case of white dwarfs, and study their static configurations numerically. One of the main results is that the inclusion of the Weyl functions from brane-world models allows the existence of more compact configurations than within general relativity.

First order Lagrangians for the Weyl invariant formulation of unimodular gravity are proposed. Several alternatives are examined; in some of them, first and second order are equivalent in a certain gauge only.

We discuss the boundary effect of anomaly-induced action in two-dimensional spacetime, which is ignored in previous studies. Anomaly-induced action, which gives the stress tensor with the same trace as the trace anomaly, can be represented in terms of local operators by introducing an auxiliary scalar field. Although the degrees of freedom of the auxiliary field can in principle describe the quantum states of the original field, the principal relation between them was unclear. We show here that, by considering the boundary effect, the solutions of classical auxiliary fields are naturally related to the quantum states of the original field. We demonstrate this conclusion via several examples such as the flat, black hole, and the de Sitter spacetime.

Analogue systems are a powerful instrument to investigate and understand in a controlled setting many general-relativistic effects. Here, we focus on superradiant-triggered instabilities and quasinormal modes. We consider a compressible hydrodynamic vortex characterized by a polytropic equation of state, the polytropic hydrodynamic vortex, a purely circulating system with an ergoregion but no event horizon. We compute the quasinormal modes of this system numerically with different methods, finding excellent agreement between them. When the fluid velocity is larger than the speed of sound, an ergoregion appears in the effective spacetime, triggering an “ergoregion instability.” We study the details of the instability for the polytropic vortex, and in particular find analytic expressions for the marginally stable configuration.

We study the binding of a small black hole to a positive-tension brane in the second Randall-Sundrum scenario (RS2) with orbifold symmetry. We find that a small black hole on the brane has substantial binding energy to the brane, and is stable against escaping into the bulk. This result can be applied in other models with an orbifold-symmetric brane. We also find a novel static black hole, which is completely localized off the brane and is unstable against translations transverse to the brane. Our results are obtained analytically by applying a variational principle to black hole initial data. This paper is the second in a series on asymptotically RS black holes.

We give a new, intrinsic, mass definition for spacetimes asymptotic to the Randall-Sundrum braneworld models, RS1 and RS2. For this mass, we prove a first law for static black holes, including variations of the bulk cosmological constant, brane tensions, and RS1 interbrane distance. Our first law defines a thermodynamic volume and a gravitational tension that are braneworld analogs of the corresponding quantities in asymptotically AdS black hole spacetimes and asymptotically flat compactifications, respectively. We also prove the following related variational principle for asymptotically RS black holes: instantaneously static initial data that extremizes the mass yields a static black hole, for variations at fixed apparent horizon area, AdS curvature length, cosmological constant, brane tensions, and RS brane warp factors. This variational principle is valid with either two branes (RS1) or one brane (RS2), and is applicable to variational trial solutions.

We explore the implications of hidden symmetries present in a particular quantum cosmological setting, extending the results reported in Jalalzadeh and Moniz [Phys. Rev. D 89, 083504 (2014)] and Jalalzadeh et al. [Eur. Phys. J. C 75, 38 (2015)]. In more detail, our case study is constituted by a spatially closed Friedmann-Lemaître-Robertson-Walker universe, in the presence of a conformally coupled scalar field. The $su(1,1)$ hidden symmetries of this model, together with the Hamiltonian constraint, lead to the gauge invariance of its corresponding Bargmann indices. We subsequently show that some factor-ordering choices can be related to the allowed spectrum of Bargmann indices and, hence, to the hidden symmetries. Moreover, the presence of those hidden symmetries also implies a set of appropriate boundary conditions to choose from. In summary, our results suggest that factor ordering and boundary conditions can be intertwined when a quantum cosmological model has hidden symmetries.

In this work we study different classes of effective composite metrics proposed in the context of one-loop quantum corrections in bimetric gravity. For this purpose we consider contributions of the matter loops in the form of cosmological constants and potential terms yielding two types of effective composite metrics. This guarantees a nice behavior at the quantum level. However, the theoretical consistency at the classical level needs to be ensured additionally. It turns out that among all these possible couplings, only one unique effective metric survives these criteria at the classical level.

Thermoelastic distortion resulting from optical absorption by transmissive and reflective optics can cause unacceptable changes in optical systems that employ high-power beams. In advanced-generation laser-interferometric gravitational wave detectors, for example, optical absorption is expected to result in wavefront distortions that would compromise the sensitivity of the detector, thus necessitating the use of adaptive thermal compensation. Unfortunately, these systems have long thermal time constants, and so predictive feed-forward control systems could be required, but the finite-element analysis is computationally expensive. We describe here the use of the Betti-Maxwell elastodynamic reciprocity theorem to calculate the response of linear elastic bodies (optics) to heating that has arbitrary spatial distribution. We demonstrate, using a simple example, that it can yield accurate results in computational times that are significantly less than those required for finite-element analyses.

Gravitational waves (GWs) from the early universe and unresolved astrophysical sources are expected to create a stochastic GW background (SGWB). The GW radiometer algorithm is well suited to probe such a background using data from ground-based laser interferometric detectors. Radiometer analysis can be performed in different bases, e.g., isotropic, pixel or spherical harmonic. Each of these analyses possesses a common temporal symmetry which we exploit here to fold the whole data set for every detector pair, typically a few hundred to a thousand days of data, to only one sidereal day, without any compromise in precision. We develop the algebra and a software pipeline needed to fold data, accounting for the effect of overlapping windows and nonstationary noise. We implement this on LIGO’s fifth science run data and validate it by performing a standard anisotropic SGWB search on both folded and unfolded data. Folded data not only leads to orders of magnitude reduction in computation cost, but it results in a conveniently small data volume of few gigabytes, making it possible to perform an actual analysis on a personal computer, as well as easy movement of data. A few important analyses, yet unaccomplished due to computational limitations, will now become feasible. Folded data, being independent of the radiometer basis, will also be useful in reducing processing redundancies in multiple searches and provide a common ground for mutual consistency checks. Most importantly, folded data will allow vast amount of experimentation with existing searches and provide substantial help in developing new strategies to find unknown sources.

We perform Bayesian analysis of gravitational-wave signals from nonspinning, intermediate-mass black-hole binaries (IMBHBs) with observed total mass, $M_{\mathrm{obs}}$, from $50{\mathrm{M}}_{\odot }$ to $500{\mathrm{M}}_{\odot }$ and mass ratio 1–4 using advanced LIGO and Virgo detectors. We employ inspiral-merger-ringdown waveform models based on the effective-one-body formalism and include subleading modes of radiation beyond the leading (2,2) mode. The presence of subleading modes increases signal power for inclined binaries and allows for improved accuracy and precision in measurements of the masses as well as breaking of degeneracies in distance, orientation and polarization. For low total masses, $M_{\mathrm{obs}}\lesssim 50{\mathrm{M}}_{\odot }$, for which the inspiral signal dominates, the observed chirp mass ${\mathcal{M}}_{\text{obs}}=M_{\mathrm{obs}}{\eta }^{3/5}$ ($\eta$ being the symmetric mass ratio) is better measured. In contrast, as increasing power comes from merger and ringdown, we find that the total mass $M_{\mathrm{obs}}$ has better relative precision than ${\mathcal{M}}_{\text{obs}}$. Indeed, at high $M_{\mathrm{obs}}$ ($\ge 300{\mathrm{M}}_{\odot }$), the signal resembles a burst and the measurement thus extracts the dominant frequency of the signal that depends on $M_{\mathrm{obs}}$. Depending on the binary’s inclination, at signal-to-noise ratio (SNR) of 12, uncertainties in $M_{\mathrm{obs}}$ can be as large as $\sim 20–25\%$ while uncertainties in ${\mathcal{M}}_{\text{obs}}$ are $\sim 50–60\%$ in binaries with unequal masses (those numbers become $\sim 17\%$ vs. $\sim 22\%$ in more symmetric mass-ratio binaries). Although large, those uncertainties in $M_{\mathrm{obs}}$ will establish the existence of IMBHs. We find that effective-one-body waveforms with subleading modes are essential to confirm a signal’s presence in the data, with calculated Bayesian evidences yielding a false alarm probability below ${10}^{-5}$ for $\mathrm{SNR}\gtrsim 9$ in Gaussian noise. Our results show that gravitational-wave observations can offer a unique tool to observe and understand the formation, evolution and demographics of IMBHs, which are difficult to observe in the electromagnetic window.

We consider a simplified model for self-induced flavor conversions of a dense neutrino gas in two dimensions, showing new solutions that spontaneously break the spatial symmetries of the initial conditions. As a result of the symmetry breaking induced by the neutrino-neutrino interactions, the coherent behavior of the neutrino gas becomes unstable. This instability produces large spatial variations in the flavor content of the ensemble. Furthermore, it also leads to the creation of domains of different net lepton number flux. The transition of the neutrino gas from a coherent to incoherent behavior shows an intriguing analogy with a streaming flow changing from laminar to turbulent regime. These findings would be relevant for the self-induced conversions of neutrinos streaming-off a supernova core.

We study strings between static quarks in QCD with $n_f$ adjoint fermions, including $\mathcal{N}=1$ supersymmetric Yang-Mills (SYM), in the calculable regime on ${\mathbb{R}}^3\times {\mathbb{S}}_L^1$, which shares many features with the XY-spin model. We find that they have many qualitatively new features not previously known. The difference from other realizations of Abelian confinement is due to the composite nature of magnetic bions, whose Dirac quantum with fundamental quarks is two, and to the unbroken part of the Weyl group. In particular we show that strings are composed of two domain walls, that quarks are not confined on domain walls, that strings can end on domain walls, and that “Y” or “$\mathrm{\Delta }$” baryons can form. By similar argumentation, liberation of vortices on domain walls in the condensed matter counterparts may have important implications in the physics of transport. In the gauge theory we briefly discuss the lightest modes of strings and the decompactification limit.

We present a complete phenomenological model accounting for the evolution of the cosmic ray spectrum and composition with energy, based on the available data over the entire spectrum. We show that there is no need to postulate any additional component, other than one single Galactic component depending on rigidity alone and one extragalactic component, the characteristics of which are similar to those derived from a study of particle acceleration at mildly relativistic shocks in a gamma-ray burst environment (Globus et al., 2015). In particular, we show that the resulting cosmic ray spectrum and composition satisfy the various constraints derived from the current data in the Galactic/extragalactic transition region, notably from the measurements of KASCADE Grande and Auger. Finally, we derive some generic features that a working phenomenological scenario may exhibit to give a global account of the cosmic ray data with a minimum number of free parameters.