We study the chiral vortical effect far from equilibrium in a strongly coupled holographic field theory. Rotation is represented as a perturbation via a gravito-magnetic field on top of a five-dimensional charged AdS Vaidya metric. We also introduce a momentum relaxation mechanism by linear scalar field backgrounds and study the chiral vortical effects (CVE) dynamics as function of the charges, temperature and momentum relaxation. The far from equilibrium behavior shows that the CVE builds up with a significant delay in time compared to the quasi instantaneous equilibration of the background metric. We also pay special attention to the effects of the gravitational contribution to the axial anomaly in the CVE of the axial current. We develop an analytic estimate of this delay and also compute the quasinormal modes near equilibrium which determine the late time ring down.

We study and estimate probabilistic predictions for the duration of the preinflationary and slow-roll phases after the bounce in loop quantum cosmology, determining how the presence of radiation in the pre-bounce phase affects these results. We present our analysis for different classes of inflationary potentials that include the monomial power-law chaotic type of potentials, namely, for the quadratic, quartic, and sextic potentials and also for a Higgs-like symmetry-breaking potential, considering different values for the vacuum expectation value in the latter case. We obtain the probability density function for the number of inflationary $e$-folds and for other relevant quantities for each model and produce probabilistic results drawn from these distributions. This study allows us to discuss under which conditions each model could either eventually lead to observable signatures in the spectrum of the cosmic microwave background, or be excluded for not predicting a sufficient amount of accelerated expansion. The effect of radiation on the predictions for each model is explicitly quantified. The obtained results indicate that the number of inflationary $e$-folds in loop quantum cosmology is not a priori an arbitrary number, but can in principle be a predictable quantity, even though the results are dependent on the model and the amount of radiation in the Universe prior to the start of the inflationary regime.

We derive the equations of motion of dyonic black hole binaries with electric and magnetic charges and explore features of static orbits. By using a Newtonian method with the inclusion of radiation reaction, we calculate the total emission rate of energy and angular momentum due to gravitational radiation and electromagnetic radiation for circular orbits. Moreover, we obtain the evolutions of orbits and calculate merger times of dyonic binaries. We show that electric and magnetic charges significantly suppress the merger times of dyonic binaries. Our results provide rich information about dyonic binaries and can be used to test black holes with magnetic charges.

We present a novel machine-learning approach to estimate selection effects in gravitational-wave observations. Using techniques similar to those commonly employed in image classification and pattern recognition, we train a series of neural-network classifiers to predict the LIGO/Virgo detectability of gravitational-wave signals from compact-binary mergers. We include the effect of spin precession, higher-order modes, and multiple detectors and show that their omission, as it is common in large population studies, tends to overestimate the inferred merger rate in selected regions of the parameter space. Although here we train our classifiers using a simple signal-to-noise ratio threshold, our approach is ready to be used in conjunction with full pipeline injections, thus paving the way toward including actual distributions of astrophysical and noise triggers into gravitational-wave population analyses.

We investigate the effects of producing dark matter by the Hawking evaporation of primordial black holes (PBHs) in scenarios that may have a second well-motivated dark matter production mechanism, such as freeze-out, freeze-in, or gravitational production. We show that the interplay between PBHs and the alternative sources of dark matter can give rise to model-independent modifications to the required dark matter abundance from each production mechanism, which in turn affect the prospects for dark matter detection. In particular, we demonstrate that for the freeze-out mechanism, accounting for the evaporation of PBHs after freeze-out demands a larger annihilation cross section of dark matter particles than its canonical value for a thermal dark matter. For mechanisms lacking thermalization due to a feeble coupling to the thermal bath, we show that the PBH contribution to the dark matter abundance leads to the requirement of an even feebler coupling. Moreover, we show that when a large initial abundance of PBHs causes an early matter-dominated epoch, PBH evaporation alone cannot explain the whole abundance of dark matter today. In this case, an additional production mechanism is required, in contrast to the case when PBHs are formed and evaporate during a radiation-dominated epoch.

We propose a realistic theory of fermion masses and mixings using a five-dimensional warped scenario where all fermions propagate in the bulk and the Higgs field is localized on the IR brane. The assumed $T^{\prime }$ flavor symmetry is broken on the branes by flavon fields, providing a consistent scenario where fermion mass hierarchies arise from adequate choices of the bulk mass parameters, while quark and lepton mixing angles are restricted by the family symmetry. Neutrino mass splittings, mixing parameters and the Dirac $CP$ phase all arise from the type-I seesaw mechanism and are tightly correlated, leading to predictions for the neutrino oscillation parameters, as well as expected $0\nu \beta \beta$ decay rates within reach of upcoming experiments. The scheme also provides a good global description of flavor observables in the quark sector.

We present a high-statistics lattice QCD determination of the valence parton distribution function (PDF) of the pion, with a mass of 300 MeV, using two very fine lattice spacings of $\mathrm{a}=0.06\mathrm{fm}$ and 0.04 fm. We reconstruct the $x$-dependent PDF, as well as infer the first few even moments of the PDF using leading-twist 1-loop perturbative matching framework. Our analyses use both RI-MOM and ratio-based schemes to renormalize the equal-time bilocal quark-bilinear matrix elements of pions boosted up to 2.4 GeV momenta. We use various model-independent and model-dependent analyses to infer the large-$x$ behavior of the valence PDF. We also present technical studies on lattice spacing and higher-twist corrections present in the boosted pion matrix elements.

In gauge theories, charged particles obey modified dispersion due to medium interactions (forward scattering), leading at high energies $E\ge T$ to an asymptotic mass-squared $m_{\infty }^2$. We calculate the infrared part of this mass nonperturbatively for the theory of the strong interactions, QCD, through a lattice treatment of its low-energy effective description, electrostatic QCD. Incorporation of these results into a nonperturbative determination of the effective thermal mass will require a still-incomplete next-to-leading order perturbative matching of this quantity to full QCD.

The experimental search for the QCD critical point by means of relativistic heavy-ion collisions necessitates the development of dynamical models of fluctuations. In this work, we study the fluctuations of the net-baryon density near the critical point. Due to net-baryon number conservation, the correct dynamics is given by the fluid dynamical diffusion equation, which we extend by a white noise stochastic term to include intrinsic fluctuations. We quantify finite resolution and finite-size effects by comparing our numerical results to analytic expectations for the structure factor and the equal-time correlation function. In small systems, the net-baryon number conservation turns out to be quantitatively and qualitatively important, as it introduces anticorrelations at larger distances. Including nonlinear coupling terms in the form of a Ginzburg-Landau free energy functional, we observe non-Gaussian fluctuations quantified by the excess kurtosis. We study the dynamical properties of the system close to equilibrium, for a sudden quench in temperature and a Hubble-like temperature evolution. In the real-time dynamical systems, we find the important dynamical effects of critical slowing down, weakening of the extremal value and retardation of the fluctuation signal. In this work, we establish a set of general tests, which should be met by any model propagating fluctuations, including upcoming $3+1$ dimensional fluctuating fluid dynamics.

Under semiclassical evolution, black holes retain a smooth horizon but fail to return information. Yet, the Ryu-Takayanagi (RT) prescription computes the boundary entropy expected from unitary conformal field theory (CFT) evolution. We demonstrate this in a novel setting with an asymptotic bulk detector, eliminating an assumption about the entanglement wedge of auxiliary systems. We consider three interpretations of this result. (i) At face value, information is lost in the bulk but not in the CFT. This conflicts with the $\mathrm{AdS}/\mathrm{CFT}$ dictionary. (ii) No unique quantum field theory state (pure or mixed) governs all detector responses to the bulk Hawking radiation. This conflicts with the existence of an $S$ matrix. (iii) Nonlocal couplings to the black hole interior cause asymptotic detectors to respond as though the radiation was pure, even though it is naively thermal. This invalidates the standard interpretation of the semiclassical state, including its smoothness at the horizon. We conclude that unitary boundary evolution requires asymptotic bulk detectors to become unambiguously pure at late times. We ask whether the RT prescription can still reproduce the boundary entropy in this bulk scenario. We find that this requires a substantial failure of semiclassical gravity in a low-curvature region, such as a firewall that purifies the Hawking radiation. Finally, we allow that the dual to semiclassical gravity may be an ensemble of unitary theories. This appears to relax the tensions we find: the ensemble average of out states would be mixed, but the ensemble average of final entropies would vanish.

We consider different ways of modifying the mass spectrum of a strongly coupled gauge theory with confinement using the $\mathrm{AdS}/\mathrm{CFT}$ correspondence. Single- and multitrace deformations are introduced, such that the resulting theory has a mode lighter than the confinement scale. The multitrace deformation is shown to be a possible way of achieving a light composite mode, unlike the single-trace deformation where the light mode is an admixture of elementary and composite states.

The phase space of three-dimensional gravity with Compere-Song-Strominger (CSS) boundary conditions is endowed with asymptotic symmetries consisting in the semidirect product of a Virasoro and a $\widehat{u}(1)$ Kač-Moody algebra, and contains Bañados-Teitelboim-Zanelli (BTZ) black holes whose entropy can be accounted for by the degeneracy of states of a warped Conformal Field Theory (CFT). By embedding these boundary conditions in topologically massive gravity, we observe the existence of two special points in the space of couplings parametrized by the ${\mathrm{AdS}}_3$ radius $\ell$ and the Chern-Simons coupling $\mu$. When $\mu =\pm \frac{1}{\ell }$, the asymptotic symmetries reduce to either a chiral Virasoro algebra or a pure $\widehat{u}(1)$ Kač-Moody current algebra. At those points, black holes have positive energy while that of linearized excitations are non-negative.

Although the thermal and radiative effects associated with a two-level quantum system undergoing acceleration are now widely understood and accepted, a surprising amount of controversy still surrounds the simpler and older problem of an accelerated classical charge. We argue that the analogy between these systems is more than superficial; there is a sense in which a “UD detector” in a quantized scalar field effectively acts as a classical source for that field if the splitting of its energy levels is so small as to be ignored. After showing explicitly that a detector with unresolved inner structure does behave as a structureless scalar source, we use that analysis to rederive the scalar version of a previous analysis of the accelerated electromagnetic charge, without appealing to the troublesome concept of “zero-energy particles.” Then, we recover these results when the detector energy gap is taken to be zero from the beginning. This vindicates the informal terminology “zero-frequency Rindler modes” as a shorthand for “Rindler modes with arbitrarily small energy.” In an Appendix, the mathematical behavior of the normal modes in the limit of small frequency is examined in more detail than before. The vexed (and somewhat ambiguous) question of whether coaccelerating observers detect the acceleration radiation can then be studied on a sound basis.

We use galaxy-galaxy weak lensing data to perform a novel test on general relativity (GR) and $f(T)$ torsional gravity. In particular, we impose strong constraints using the torsional (teleparallel) formulation of gravity in which the deviation from GR is quantified by a single parameter $\alpha$, an approximation which is always valid at low-redshift Universe and weak gravitational fields. We calculate the difference in the deflection angle and eventually derive the modified excess surface density profile, which is mainly affected at small scales. Confronting the predictions with weak lensing data from the Sloan Digital Sky Survey Data Release 7, we obtain the upper bound on the deviation parameter, which, expressed via the dimensionless percentage in the Universe energy content, reads as ${\log }_{10}{\mathrm{\Omega }}_{\alpha }\le {-18.52}_{-0.42}^{+0.80}(\mathrm{stat}{)}_{-0.37}^{+1.50}(\mathrm{sys})[R_c/0.015R_{200}]$ with systematics mainly arising from the modeling that includes astrophysics effects, upon a reasonable choice of cutoff radius for $f(T)$ gravity in form of $T+\alpha T^2$. To our knowledge, this is the first time that GR is verified at such an accuracy at the corresponding scales.

Null infinity in asymptotically flat spacetimes posses a rich mathematical structure; including the Bondi-Metzner-Sachs (BMS) group and the Bondi news tensor that allow one to study gravitational radiation rigorously. However, Friedmann-Lemaître-Robertson-Walker (FLRW) spacetimes are not asymptotically flat because their stress-energy tensor does not decay sufficiently fast, and, in fact diverges, at null infinity. This class includes matter- and radiation-dominated FLRW spacetimes. We define a class of spacetimes whose structure at null infinity is similar to FLRW spacetimes: the stress-energy tensor is allowed to diverge and the conformal factor is not smooth at null infinity. Interestingly, for this larger class of spacetimes, the asymptotic symmetry algebra is similar to the BMS algebra but not isomorphic to it. In particular, the symmetry algebra is the semidirect sum of supertranslations and the Lorentz algebra, but it does not have any preferred translation subalgebra. Future applications include studying gravitational radiation in FLRW, the full nonlinear theory, including the cosmological memory effect, and also asymptotic charges in this framework.

In this work we demonstrate that it is possible to describe a primordial bounce with the dark energy era in a unified way, in the context of Gauss-Bonnet modified gravity. In particular, the early-time bounce has a nearly scale-invariant power spectrum of primordial scalar curvature perturbations, while the dark energy era is a viable one, meaning that it mimics the $\mathrm{\Lambda }$ cold dark matter model and is also compatible with the Planck 2018 data on cosmological parameters. In addition, our analysis indicates that the dark energy era is free from dark energy oscillations, which occur in the context of $f(R)$ gravity. We further address the latter issue by examining $f(R)$ extensions of Gauss-Bonnet models, and we show that the $f(R)$ gravity part of the action actually produces the dark energy oscillations at redshifts $z\sim 4$.

The region of spacetime near the event horizon of a black hole can be viewed as a deep potential well at large gravitational redshift relative to distant observers. However, matter orbiting in this region travels at relativistic speeds and can impart a significant Doppler shift to its electromagnetic emission, sometimes resulting in a net observed blueshift at infinity. Thus, a black hole broadens the line emission from monochromatic sources in its vicinity into a smoothly decaying “red wing”—whose flux vanishes at large redshift—together with a “blue blade” that retains finite flux up to a sharp edge corresponding to the maximum observable blueshift. In this paper, we study the blue blade produced by isotropic monochromatic emitters on circular equatorial orbits around a Kerr black hole, and we obtain simple relations describing how the maximum blueshift encodes black hole spin and inclination. We find that small values of the maximum blueshift yield an excellent probe of inclination, while larger values provide strong constraints on spin or inclination in terms of the other. These results bear direct relevance to ongoing and future observations aiming to infer the angular momenta of supermassive black holes from the broadening of their surrounding line emission.

We investigate the massless scalar field perturbations, including the quasinormal mode spectrum and the ringdown waveform, of a regular black hole spacetime that was derived via the loop quantum gravity inspired polymer quantization of spherical four-dimensional black holes. In contrast to most, if not all, of the other regular black holes considered in the literature, the resulting nonsingular spacetime has a single bifurcative horizon and hence no mass inflation. In the interior, the areal radius decreases to a minimum given by the polymerization constant, $k$, and then reexpands into a Kantowski-Sachs universe. We find indications that this black hole model is stable against small scalar perturbations. We also show that an increase in the magnitude of $k$ will decrease the height of the quasinormal mode potential and give oscillations with lower frequency and less damping.

We elaborate on the proposal of [Phys. Rev. Lett. 123, 131302 (2019).], about the possibility of hiding the cosmological constant in the complicated topology that one expects to exist at the Planck scale. We build a differential equation ruling the time evolution of $⟨K⟩$, the spatial average of the expansion scalar. Supposing that the solution $⟨K⟩=0$ exists despite the presence of a large cosmological constant $\mathrm{\Lambda }$, we show that such a solution seems to be unstable.