Recently, it has been argued that near-horizon modifications of the standard (classical) black hole spacetime could lead to observable alterations of the gravitational waveform generated by a binary black hole coalescence. Such modifications can be inspired by quantum gravity considerations, resulting in speculative horizonless exotic compact objects (ECOs) with no singularities, which may be an alternative to the classical black hole solution. A largely model-independent description of these objects proposed in the literature relies on the introduction of a partially reflective wall at some small distance away from the “would-be” horizon. The inspiral-merger ringdown of a pair of such objects would be subject to possibly detectable deviations from the black hole case due to matter effects. In particular, the ringdown phase would be modified by the late emergence of so-called “echoes” in the waveform, but most studies so far have considered spherically symmetric backgrounds. We use an in-falling scalar charge as an initial perturbation to simulate the excitation of the echoes of a rotating ECO, and we explore both the corotating and counterrotating cases, which provide distinct signals. In particular, rotation breaks the symmetry between positive and negative frequencies and introduces a subdominant frequency contribution in each echo, which we examine here for the first time. Our results follow consistently from the solution of the Teukolsky equation using the MST method developed by Mano, Suzuki, and Takasugi and the construction of the complex Green’s function integrated over different particle geodesics.

Observations of neutron star mergers in the late universe have given significant restrictions to the class of viable scalar-tensor theories. In this paper we construct black holes within the “self-tuning” class of this restricted set, whereby the bare cosmological constant is absorbed by the dynamics of the scalar, giving a lower effective cosmological constant. We use analytic expansions at the singularity, black hole and cosmological horizon, and asymptotic region, coupled with numerical solutions, to find well-behaved black holes that asymptote to the self-tuned de Sitter geometry. The geometry differs from standard general relativity black holes near the horizon, and the scalar field velocity provides a hair for the black holes.

We consider $R^2$ inflation in the Palatini gravity assuming the existence of scalar fields coupled to gravity in the most general manner. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$-inflation models. We apply this formalism for the study of popular inflationary models, whose potentials are monomials, $V\sim h^n$, with $n$ a positive even integer. We also study the Higgs model nonminimally coupled to gravity. Although these have been recently studied, in the framework of the Palatini approach, we show that the scalar power spectrum severely constrains these models. Although we do not propose a particular reheating mechanism, we show that the quadratic $\sim h^2$ and the Higgs model can survive these constraints with a maximum reheating temperature as large as $\sim {10}^{15}\mathrm{GeV}$ when reheating is instantaneous. However, this can be attained only at the cost of a delicate fine-tuning of couplings. Deviations from these fine-tuned values can still yield predictions compatible with the cosmological data for couplings that lie in very tight range, giving lower reheating temperatures.

Anti-de Sitter (AdS) vacua, being theoretically important, might have an unexpected impact on the observable Universe. We find that in early dark energy (EDE) scenarios the existence of AdS vacua around recombination can effectively lift the CMB-inferred $H_0$ value. As an example, we study a phenomenological EDE model with an AdS phase starting at the redshift $z\sim 2000$ and ending shortly after recombination (hereafter the universe will settle down in a $\mathrm{\Lambda }>0$ phase until now), and obtain a best-fit $H_0=72.74\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ without degrading the CMB fit compared with the standard $\mathrm{\Lambda }\mathrm{CDM}$ model.

In this work we consider a cosmological model in which dark energy is portrayed by a canonical scalar field which is allowed to couple to the other species by means of a disformal transformation of the metric. We revisit the current literature by assuming that the disformal function in the metric transformation can depend both on the scalar field itself and on its derivatives, encapsulating a wide variety of scalar-tensor theories. This generalization also leads to new and richer phenomenology, explaining some of the features found in previously studied models. We present the background equations and perform a detailed dynamical analysis, from where new disformal fixed points emerge, that translate into novel cosmological features. These include early scaling regimes between the coupled species and broader stability parameter regions. However, viable cosmological models seem to have suppressed disformal late-time contributions.

We determine the relationship between the turnaround radius, $R_{\mathrm{t}}$, and mass, $M_{\mathrm{t}}$, in $\mathrm{\Lambda }\mathrm{CDM}$, and in dark energy scenarios, using an extended spherical collapse model taking into account the effects of shear and vorticity. We find a more general formula than that usually described in literature, showing a dependence of $R_{\mathrm{t}}$ from shear, and vorticity. The $R_{\mathrm{t}}-M_{\mathrm{t}}$ relation differs from that obtained not taking into account shear, and rotation, especially at galactic scales, differing $\simeq 30\%$ from the result given in literature. This has effects on the constraint of the $w$ parameter of the equation of state. We compare the $R_{\mathrm{t}}-M_{\mathrm{t}}$ relationship obtained for the $\mathrm{\Lambda }\mathrm{CDM}$, and different dark energy models to that obtained in the $f(R)$ modified gravity (MG) scenario. The $R_{\mathrm{t}}-M_{\mathrm{t}}$ relationship in $\mathrm{\Lambda }\mathrm{CDM}$, and dark energy scenarios are tantamount to the prediction of the $f(R)$ theories. Then, the $R_{\mathrm{t}}-M_{\mathrm{t}}$ relationship is not a good probe to test gravity theories beyond Einstein’s general relativity.

We present a joint analysis of the Planck cosmic microwave background (CMB) and Baryon Oscillation Spectroscopic Survey (BOSS) final data releases. A key novelty of our study is the use of a new full-shape (FS) likelihood for the redshift-space galaxy power spectrum of the BOSS data, based on an improved perturbation theory template. We show that the addition of the redshift-space galaxy clustering measurements breaks degeneracies present in the CMB data alone and tightens constraints on cosmological parameters. Assuming the minimal $\mathrm{\Lambda }\mathrm{CDM}$ cosmology with massive neutrinos, we find the following late-Universe parameters: the Hubble constant $H_0=67.95_{-0.52}^{+0.66}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, the matter density fraction ${\mathrm{\Omega }}_m=0.3079_{-0.0085}^{+0.0065}$, the mass fluctuation amplitude ${\sigma }_8=0.8087_{-0.0072}^{+0.012}$, and an upper limit on the sum of neutrino masses $M_{\mathrm{tot}}<0.16\mathrm{eV}$ (95% C.L.). This can be contrasted with the Planck-only measurements: $H_0=67.14_{-0.72}^{+1.3}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, ${\mathrm{\Omega }}_m=0.3188_{-0.016}^{+0.0091}$, ${\sigma }_8=0.8053_{-0.0091}^{+0.019}$, and $M_{\mathrm{tot}}<0.26\mathrm{eV}$ (95% C.L.). Our bound on the sum of neutrino masses relaxes once the hierarchy-dependent priors from the oscillation experiments are imposed. The addition of the new FS likelihood also constrains the effective number of extra relativistic degrees of freedom, $N_{\mathrm{eff}}=2.88\pm 0.17$. Our study shows that the current FS and the pure baryon acoustic oscillation data add a similar amount of information in combination with the Planck likelihood. We argue that this is just a coincidence given the BOSS volume and efficiency of the current reconstruction algorithms. In the era of future surveys FS will play a dominant role in cosmological parameter measurements.

Macroscopic dark matter—“macros”—refers to a broad class of alternative candidates to particle dark matter with still unprobed regions of parameter space. These candidates would transfer energy primarily through elastic scattering with approximately their geometric cross section. For sufficiently large cross sections, the linear energy deposition could produce observable signals if a macro were to pass through compact objects such as white dwarfs or neutron stars in the form of thermonuclear runaway, leading to a type Ia supernova or superburst, respectively. We update the constraints from white dwarfs. These are weaker than previously inferred in important respects because of more careful treatment of the passage of a macro through the white dwarf and greater conservatism regarding the size of the region that must be heated to initiate runaway. On the other hand, we place more stringent constraints on macros at a low cross section, using new data from the Montreal White Dwarf Database. New constraints are inferred from the low mass x-ray binary 4U 1820-30, in which more than a decade passed between successive superbursts. Updated microlensing constraints are also reported.

We examine the maximum possible strength of the global 21-cm absorption dip on the cosmic background radiation at high-redshift caused by the atomic intergalactic medium, when the Lyman-$\alpha$ coupling is maximum, assuming no exotic cooling mechanisms from interactions with dark matter. This maximum absorption is limited by three inevitable factors that need to be accounted for: (a) heating by energy transferred from the cosmic background radiation to the hydrogen atoms via 21-cm transitions, dubbed as 21-cm heating; (b) $\mathrm{Ly}\alpha$ heating by scatterings of $\mathrm{Ly}\alpha$ photons from the first stars; (c) the impact of the expected density fluctuations in the intergalactic gas in standard cold dark matter theory, which reduces the mean 21-cm absorption signal. Inclusion of this third novel effect reduces the maximum global 21-cm absorption by $\sim 10\%$. Overall, the three effects studied here reduce the 21-cm global absorption by $\sim 20\%$ at $z\simeq 17$.

We present a semianalytical method for the calculation of coherent Askaryan radiation in showers induced by neutrinos of any flavor in ice. We compare our results with those of a full Monte Carlo simulation based on the zhaires code. This approach is able to reproduce the vector potential and hence electric field at any experimentally relevant observer position in the time domain. This work extends published results only valid for electron-induced showers. We establish the validity of the semianalytical calculation of the radio signal produced by all types of neutrino-induced showers in ice. The method is computationally efficient and only requires as inputs the longitudinal charge excess profile of the showers and a parametrization of the vector potential in the far-field region of the shower at the Cherenkov angle that we also provide. Our methodology avoids tracking the contributions to the electric field from millions of particles every time the radio pulse has to be calculated at a given observer position. These results can be readily used in the interpretation of the data taken by experiments, and in the planning and design of future initiatives based on the radio technique in ice.

Very high energy photons from cosmological gamma-ray bursts (GRBs) are expected to interact with extragalactic background light (EBL) and produce electron-positron pairs when they propagate through intergalactic medium (IGM). These relativistic pairs will then up-scatter cosmic microwave background (CMB) photons and emit secondary GeV emission. Meanwhile, the motion of these pairs are deflected by intergalactic magnetic field (IGMF), so the secondary GeV photons arrive later than the primary emission. It has been suggested that the properties of the secondary GeV emission can be used to constrain IGMF. Recently, TeV gamma-ray emission has been detected, for the first time, from a GRB (GRB 190114C) by the MAGIC telescope and its steep $\gamma$-ray spectrum shows a clear evidence of absorption by EBL. We then constrain the IGMF with the GeV flux limit obtained from the Fermi-LAT observations. We find a limit of $>{10}^{-19.5}\mathrm{G}$ for the coherence length of $\lambda \le 1\mathrm{Mpc}$. Although this limit is weaker than that obtained by using blazars, it represents the first limit from $\gamma$-ray observations of GRBs, which provides an independent constraint on IGMF. We also find that, for transient $\gamma$-ray sources, one can choose a favorable time window to search for the echo emission at a particular energy.

An influence of a magnetic field on beta-processes is investigated under conditions of a core-collapse supernova. For realistic magnetic fields reachable in astrophysical objects we obtain simple analytical expressions for reaction rates of beta-processes as well as the energy and momentum transferred from neutrinos and antineutrinos to the matter. Based on the results of one-dimensional simulations of a supernova explosion, we found that, in the magnetic field with the strength $B\sim {10}^{15}\mathrm{G}$, the quantities considered are modified by a few percents only and, as a consequence, the magnetic-field effects can be safely neglected, considering neutrino interaction and propagation in a supernova matter. The analytical results can be also applied for accretion discs formed at a merger of compact objects in close binary systems.

As evidenced by the coincident detections of GW170817 and GRB 170817A, short gamma-ray bursts are likely associated with neutron star–neutron star merger events. Although rare, some bursts display episodes of early emission, with precursor flares being observed up to $\sim 10\mathrm{seconds}$ prior to the main burst. As the stars inspiral due to gravitational wave emission, the exertion of mutual tidal forces leads to the excitation of stellar oscillation modes, which may come into resonance with the orbital motion. Mode amplitudes increase substantially during a period of resonance as tidal energy is deposited into the star. The neutron-star crust experiences shear stress due to the oscillations and, if the resonant amplitudes are large enough, may become overstrained. This overstraining can lead to fractures or quakes which release energy, thereby fueling precursor activity prior to the merger. Using some simple Maclaurin spheroid models, we investigate the influence of magnetic fields and rapid rotation on tidally forced $f$ and $r$ modes, and connect the associated eigenfrequencies with the orbital frequencies corresponding to precursor events seen in, for example, GRB 090510.

While a fully-coherent all-sky search is known to be optimal for detecting gravitational wave signals from compact binary coalescences, its high computational cost has limited current searches to less sensitive coincidence-based schemes. Following up on previous work that has demonstrated the effectiveness of particle swarm optimization (PSO) in reducing the computational cost of this search, we present an implementation that achieves near real-time computational speed. This is achieved by combining the search efficiency of PSO with a significantly revised and optimized numerical implementation of the underlying mathematical formalism along with additional multithreaded parallelization layers in a distributed computing framework. For a network of four second-generation detectors with 60 min data from each, the runtime of the implementation presented here ranges between $\approx 1.4$ to $\approx 0.5$ times the data duration for network signal-to-noise ratios (SNRs) of $\gtrsim 10$ and $\gtrsim 12$, respectively. The reduced runtimes are obtained with small to negligible losses in detection sensitivity: for a false alarm rate of $\simeq 1$ event per year in Gaussian stationary noise, the loss in detection probability is $\le 5\%$ and $\le 2\%$ for SNRs of 10 and 12, respectively. Using the fast implementation, we are able to quantify frequentist errors in parameter estimation for signals in the double neutron star mass range using a large number of simulated data realizations. A clear dependence of parameter estimation errors and detection sensitivity on the condition number of the network antenna pattern matrix is revealed. Combined with previous work, this paper securely establishes the effectiveness of PSO-based fully-coherent all-sky search across the entire binary inspiral mass range that is relevant to ground-based detectors.

We present results from analytic solutions to the running coupling, full next-to-leading order, and collinearly improved next-to-leading order Balitsky-Kovchegov equations in the saturation region with the smallest dipole size QCD running coupling prescription. The analytic results of the $S$ matrix of the latter two equations show that the $\exp (-\mathcal{O}(Y^{3/2}))$ rapidity dependence of the solutions is replaced by $\exp (-\mathcal{O}(Y))$ dependence once the running coupling prescription is switched from parent dipole to the smallest dipole prescription, which indicates that the $S$ matrix has a strong dependence on the choice of running coupling prescription. We compute the numerical solutions of these Balitsky-Kovchegov equations with the smallest and parent dipole running coupling prescriptions; the numerical results confirm the analytic outcomes. The rare fluctuations of the $S$ matrix on top of full next-to-leading order corrections are also studied under the smallest dipole running coupling prescription in the center of mass frame. It shows that the rare fluctuations are strongly suppressed and less important in the smallest dipole running coupling prescription case as compared to the parent dipole running coupling prescription case.

We demonstrate that solitons of a simple real scalar field model that are static and linearly stable do exist when considered in a ($3+1$)-dimensional, spatially compact space-time background, the static Einstein universe, which is a good approximation to the observed Universe for sufficiently small time intervals. We study the properties of these solutions for a ${\mathrm{\Phi }}^4$-potential and demonstrate that next to the fundamental solutions, excited configurations exist. We also investigate general perturbations about the solitons, determine their eigenfrequency spectra, and compare them to those of the perturbations about the vacua of the model. We find that the degeneracy with respect to the multipoles of the perturbation, which is present for the vacua, no longer exists in the presence of the soliton. Moreover, specific perturbations correspond to zero modes of the system. Our results have applications in condensed matter physics as well as computations of quantum effects (e.g., the Casimir energy) in spatially compact space-times in the presence of solitonlike objects.

The possibility of the Y(4260) being the molecular state of $D{\overline{D}}_1(2420)+\mathrm{c}.\mathrm{c}.$ is investigated in the one boson exchange model. It turns out that the potential of $J^{PC}=1^{--}$ state formed by $D{\overline{D}}_1(2420)+\mathrm{c}.\mathrm{c}.$ is attractive and strong enough to bind them together when the momentum cutoff $\mathrm{\Lambda }\gtrsim 1.4\mathrm{GeV}$. To produce the Y(4260) with correct binding energy, we need $\mathrm{\Lambda }\approx 2.25\mathrm{GeV}$. Besides, $D{\overline{D}}_1(2420)+\mathrm{c}.\mathrm{c}.$ can also form a state with exotic quantum numbers, $J^{PC}=1^{-+}$, and its potential is more attractive than that of the $J^{PC}=1^{--}$ state. Therefore, an exotic state with mass around 4240 MeV [called ${\eta }_{c1}(4240)$] is expected to exist. Our estimation of the mass of the $J^{PC}=1^{-+}$ state in charmonium region is in agreement with those predicted by the chiral quark model and the lattice QCD. The possible decay modes and their relative widths are estimated and the results suggest that this exotic state can be searched for in $\eta {\eta }_c$ and $\eta {\chi }_{c1}$ channels.

We present a model of vector dark matter that interacts through a low-mass vector mediator based on the Higgsing of an SU(2) dark sector. The dark matter is charged under a U(1) gauge symmetry. Even though this symmetry is broken, the residual global symmetries of the theory prevent dark matter decay. We present the behavior of the model subject to the assumption that the dark matter abundance is due to thermal freeze out, including self-interaction targets for small scale structure anomalies and the possibility of interacting with the Standard Model through the vector mediator.

In the framework of the representation theory of finite groups, it was recently shown that a fully constrained complex-symmetric mass matrix can be conveniently mapped into a sextet of $\mathrm{\Sigma }(72\times 3)$. In this paper, we introduce an additional flavor group $X_{24}$ in the model so that the vacuum alignment of the $\mathrm{\Sigma }(72\times 3)$ sextet is determined not only by the symmetries of $\mathrm{\Sigma }(72\times 3)$ but also by that of $X_{24}$. We define several flavons which transform as multiplets under $\mathrm{\Sigma }(72\times 3)$ as well as $X_{24}$. The vacuum alignment of each of these flavons is obtained as a simultaneous invariant eigenstate of specific elements of the groups $\mathrm{\Sigma }(72\times 3)$ and $X_{24}$; i.e., the vacuum alignment is fully determined by its residual symmetries. These flavons couple together uniquely resulting in the fully constrained sextet of $\mathrm{\Sigma }(72\times 3)$. Through this work we propose a general formalism in which the flavor symmetry group ($G_f$) is obtained as the direct product, $G_f=G_r\times G_x$. Fermions transform nontrivially only under $G_r$ while they remain invariant under $G_x$. Flavons, on the other hand, transform nontrivially under both $G_r$ and $G_x$. The vacuum alignment of each flavon multiplet transforming irreducibly under $G_r\times G_x$ is uniquely identified by its corresponding residual symmetry (a subgroup of $G_r\times G_x$). Several such flavons couple together to form an effective multiple of $G_r$ which remains invariant under $G_x$. This effective multiplet couples to the fermions.

The origin of the low-lying nature of the $N^{*}(1440)$, or Roper resonance, has been the subject of significant interest for many years, including several investigations using lattice QCD. The majority of lattice studies have not observed a low-lying excited state energy level in the region of the Roper resonance. However, it has been claimed that chiral symmetry could play an important role in our understanding of this resonance. The purpose of this study is to systematically examine the role of chiral symmetry in the low-lying nucleon spectrum by directly comparing the clover and overlap fermion actions. To ensure any differences in results are attributable to the choice of fermion action, simulations are performed on the same set of gauge field configurations at matched pion masses. Correlation matrix techniques are employed to determine the excitation energy of the first positive-parity excited state for each action. The clover and overlap actions show a remarkable level of agreement. We do not find any evidence that fermion action chiral symmetry plays a significant role in understanding the Roper resonance on the lattice.