Although spinning black holes are shown to be stable in vacuum in general relativity, exotic mechanisms have been speculated to convert the spin energy of black holes into gravitational waves. Such waves may be very weak in amplitude, since the spin-down could take a long time, therefore a direct search may not be feasible. We propose to search for the stochastic red gravitational-wave background associated with the spin-down, and we relate the level of this background to the formation rate of spinning black holes from the merger of binary black holes, as well as the energy spectrum of waves emitted by the spin-down process. We argue that current LIGO-Virgo observations are not inconsistent with the existence of a spin-down process, as long as it is slow enough. On the other hand, the background may still detectable as long as a moderate fraction of spin energy is emitted within Hubble time. This stochastic background could be one interesting target of next generation GW detector network, such as LIGO Voyager, and could be extracted from total stochastic background.

It is well known that the Reissner-Norstrom solution of Einstein-Maxwell theory cannot be cylindrically extended to a higher dimension, as with the black hole solutions in vacuum. In this paper we show that this result is circumvented in Lovelock gravity. We prove that the theory containing only the quadratic Lovelock term, the Gauss-Bonnet term, minimally coupled to a $U(1)$ field, admits homogeneous black string and black brane solutions characterized by the mass, charge and volume of the flat directions. We also show that theories containing a single Lovelock term of order $n$ in the Lagrangian coupled to a ($p-1$)-form field admit simple oxidations only when $n$ equals $p$, giving rise to new, exact, charged black branes in higher curvature gravity. For general relativity this stands for a Lagrangian containing the Einstein-Hilbert term coupled to a massless scalar field, and no-hair theorems in this case forbid the existence of black branes. In all these cases the field equations acquire an invariance under a global scaling scale transformation of the metric. As explicit examples we construct new magnetically charged black branes for cubic Lovelock theory coupled to a Kalb-Ramond field in dimensions $(3m+2)+q$, with $m$ and $q$ integers, and the latter denoting the number of extended flat directions. We also construct dyonic solutions in quartic Lovelock theory in dimension $(4m+2)+q$.

The study of the cosmic microwave background (CMB) lensing potential has established itself by now as a robust way of probing the physics of large-scale structure growth. The most common estimators of the lensing potential are derived under the assumption of Gaussianity of the matter distribution and in the Born approximation of the photon diffusion. In this paper we study the performance of quadratic estimators when applied to realistic sky maps extracted from multiple-lens ray tracing techniques in cosmological $N$-body simulations. These are expected to model accurately the effects due to the non-Gaussianity of the matter distribution induced by its nonlinearity and the deviation from the Born approximation. We show that both these effects on their own lead to reconstruction biases, but these tend to partially cancel each other when both these effects are considered together. We forecast the impact of these biases on the estimation of cosmological parameters for future high-sensitivity CMB experiments like CMB-S4. We find that the cold dark matter density, ${\mathrm{\Omega }}_{\mathrm{cdm}}$, the optical depth to reionization $\tau$, the amplitude of primordial inflationary perturbations, $A_s$, and the sum of neutrino masses, $M_{\nu }$, could be biased at the $1–2\sigma$ level, if no external data set is used. We also observe a reduction of the bias if external data like baryon acoustic oscillations is included.

21 cm intensity mapping has emerged as a promising technique to map the large-scale structure of the Universe, at redshifts $z$ from 1 to 10. Unfortunately, many of the key cross-correlations with the cosmic microwave background and photo-$z$ galaxies have been thought to be impossible due to the foreground contamination for radial modes with small wave numbers. In this paper, we apply tidal reconstruction to the simulated 21 cm fields and recover the lost large-scale radial modes successfully. We estimate the detectability of the cross-correlation signals and find they can be detected at high significance with current 21 cm experiments. The tidal field reconstruction method opens up a new set of possibilities to probe the Universe and is extremely valuable not only for 21 cm surveys but also for cosmic microwave background and photometric-redshift observations.

We study and analyze the dynamic properties of both canonical and noncanonical warm inflationary models with dissipative effects. We consider different models of canonical warm inflation with different dissipative coefficients and prove that the behavior at infinity of the quadratic dissipative model distinctly differs from that of the constant dissipative model, which means that quadratic dissipative coefficient increases the possibility of the occurrence of inflation. We also show that the different choice of combination of the parameters in noncanonical warm inflation exhibits dramatically different global phase portraits on the Poincaré disk. We try to illustrate that the noncanonical field will not expand the regime of inflation, but it will increase the possibility of the occurrence of inflation as well and the duration of inflation. Then, by dynamic analysis, we can exclude several inflationary models, like the warm inflation model, with negative dissipative coefficients, and explain that the model without potential is almost impossible. With relevant results, we give the condition when reheating occurs.

We simulate the formation and evolution of ultralight bosonic dark matter halos from cosmological initial conditions. Using zoom-in techniques, we are able to resolve the detailed interior structure of the halos. We observe the formation of solitonic cores and confirm the core-halo mass relation previously found by Schive et al. The cores exhibit strong quasinormal oscillations that remain largely undamped on evolutionary time scales. On the other hand, no conclusive growth of the core mass by condensation or relaxation can be detected. In the incoherent halo surrounding the cores, the scalar field density profiles and velocity distributions show no significant deviation from collisionless N-body simulations on scales larger than the coherence length. Our results are consistent with the core properties being determined mainly by the coherence length at the time of virialization, whereas the Schrödinger-Vlasov correspondence explains the halo properties when averaged on scales greater than the coherence length.

We present measurements of radio transmission in the $\sim 100\mathrm{MHz}$ range through a $\sim 100\mathrm{m}$ deep region below the surface of the ice at Summit Station, Greenland, called the firn. In the firn, the index of refraction changes due to the transition from snow at the surface to glacial ice below, affecting the propagation of radio signals in that region. We compare our observations to a finite-difference time-domain (FDTD) electromagnetic wave simulation, which supports the existence of three classes of propagation: a bulk propagation ray-bending mode that leads to so-called “shadowed” regions for certain geometries of transmission, a surface-wave mode induced by the ice/air interface, and an arbitrary-depth horizontal propagation mode that requires perturbations from a smooth density gradient. In the non-shadowed region, our measurements are consistent with the bulk propagation ray-bending mode both in timing and in amplitude. We also observe signals in the shadowed region, in conflict with a bulk-propagation-only ray-bending model, but consistent with FDTD simulations using a variety of firn models for Summit Station. The amplitude and timing of our measurements in all geometries are consistent with the predictions from FDTD simulations. In the shadowed region, the amplitude of the observed signals is consistent with a best-fit coupling fraction value of 2.4% (0.06% in power) or less to a surface or horizontal propagation mode from the bulk propagation mode. The relative amplitude of observable signals in the two regions is important for experiments that aim to detect radio emission from astrophysical high-energy neutrinos interacting in glacial ice, which rely on a radio propagation model to inform simulations and perform event reconstruction.

We investigate meson and nucleon dynamics at finite baryon density and temperature by coupling the nucleon field and the omega meson to the three-flavor linear sigma model and calculate hadronic properties around the nuclear liquid-gas transition. We apply the functional renormalization group method, and find that mesonic fluctuations increase the strength of the coefficient of the $U_A(1)$ breaking determinant operator as a function of the chiral condensate. As a consequence, we find that the actual value of the anomaly increases discontinuously at the first order nuclear liquid-gas transition. We calculate how mesonic masses and partial restoration of chiral symmetry are modified due to such an effect.

In this paper, we obtain a nonrelativistic Hamiltonian from the Lorentz-violating (LV) scalar Lagrangian in the minimal standard model extension (SME). The Hamiltonian is obtained by two different methods. One is through the usual ansatz $\mathrm{\Phi }(t,\overrightarrow{r})=e^{-imt}\mathrm{\Psi }(t,\overrightarrow{r})$ applied to the LV-corrected Klein-Gordon equation, and the other is the Foldy-Wouthuysen transformation. The consistency of our results is also partially supported by the comparison with the spin-independent part of the fermion Hamiltonian. In this comparison, we can also establish a relation between the set of scalar LV coefficients with their fermion counterparts. Using a pedagogical definition of the weak equivalence principle (WEP), we further point out that the LV Hamiltonian not only necessarily violates universal free fall, which is clearly demonstrated in the geodesic deviation, but also violates WEP in a semiclassical setting. As a bosonic complement, this method can be straightforwardly applicable to the spin-1 case, which shall be useful in the analysis of atomic tests of WEP, such as the case of the ${{}^{87}\mathrm{Rb}}_1$ atom.

In this work, we present a systematic study on the feasibility of probing the largely unexplored transverse-momentum-dependent gluon Sivers function (GSF) in open charm production, and high-$p_T$ charged dihadron and dijet production at a future high-energy, high-luminosity electron-ion collider (EIC). The Sivers function is a measure for the anisotropy of the parton distributions in momentum space inside a transversely polarized nucleon. It is proposed that it can be studied through single spin asymmetries in the photon-gluon fusion subprocess in electron-proton collisions at the EIC. Using a well-tuned Monte Carlo model for deep inelastic scattering, we estimate the possible constraints of the GSF from the future EIC data. A comparison of all the accessible measurements illustrates that the dijet channel is the most promising way to constrain the magnitude of the GSF over a wide kinematic range.

We quantify the importance of dynamical spin effects in the holographic light-front wavefunctions of the pion, kaon, $\eta$ and ${\eta }^{\prime }$. Using a universal AdS/QCD scale and constituent quark masses, we find that such effects are maximal in the pion where they lead to an excellent simultaneous description of a wide range of data: the decay constant, charge radius, spacelike EM and transition form factors, as well as, after QCD evolution, both the parton distribution function and the parton distribution amplitude data from Fermilab. These dynamical spin effects lead up to a 30% chance of finding the valence quark and antiquark with aligned spins in the pion. The situation is very different for the kaon, where a simultaneous description of the available data (decay constant, radius and spacelike EM form factor) prefer no dynamical spin effects at all. The situation is less clear for the $\eta$ and ${\eta }^{\prime }$: while their radiative decay widths data are consistent with dynamical spin effects only in ${\eta }^{\prime }$, the data on their spacelike transition form factors clearly favor maximal dynamical spin effects in both mesons.

The one-loop effective action of quantum electrodynamics in four dimensions is shown to be controlled by the Euclidean Dirac propagator $G$ in a background potential. After separating the photon self-energy and photon-photon scattering graphs from the effective action the remainder is known to be the logarithm of an entire function of the electric charge of order 4 under mild regularity assumptions on the potential. This input together with quantum electrodynamics’ (QED) lack of an ultrastable vacuum constrain the strong field behavior of $G$. It is shown that $G$ vanishes in the strong field limit. The relevance of this result to the decoupling of QED from the remainder of the electroweak model for large amplitude variations of the Maxwell field is discussed.

We further develop a simple and compact technique for calculating the three flavor neutrino oscillation probabilities in uniform matter density. By performing additional rotations instead of implementing a perturbative expansion we significantly decrease the scale of the perturbing Hamiltonian and therefore improve the accuracy of zeroth order. We explore the relationship between implementing additional rotations and that of performing a perturbative expansion. Based on our analysis, independent of the size of the matter potential, we find that the first order perturbation expansion can be replaced by two additional rotations and a second order perturbative expansion can be replaced by one more rotation. Numerical tests have been applied and all the exceptional features of our analysis have been verified.

A concept of measuring the quantum distance between two different quantum states that is called quantum information metric has been presented. The holographic principle (anti–de Sitter/conformal field theory) suggests that the quantum information metric $G_{\lambda \lambda }$ between perturbed state and unperturbed state in field theory has a dual description in the classical gravity. In this work we calculate the quantum information metric of a theory that is dual to a conical defect geometry and we show that it is $n$ times the one of its covering space. We also give a holographic check for our result in the gravity side. Meanwhile, it was argued that $G_{\lambda \lambda }$ is dual to a codimension-one surface in spacetime and satisfies $G_{\lambda \lambda }=n_d·\mathrm{Vol}({\mathrm{\Sigma }}_{\max })/L^d$. We show that the coefficient $n_d$ for conical defect should be rescaled by $n^2$ from the one for anti–de Sitter space. A limit case of conical defect—the massless Banados-Teitelboim-Zannelli (BTZ) black hole—is also considered. We show that the quantum information metric of a massless BTZ black hole disagrees with the one obtained by taking the vanishing temperature limit in BTZ black hole. This provides a new arena in differentiating the different phases between BTZ spacetime and its massless cousin.

We hereby study the properties of a large class of weakly nonlocal gravitational theories around the (anti–) de Sitter spacetime background. In particular, we explicitly prove that the kinetic operator for the graviton field has the same structure as the one in Einstein-Hilbert theory around any maximally symmetric spacetime. Therefore, the perturbative spectrum is the same as standard general relativity, while the propagator on any maximally symmetric spacetime is a mere generalization of the one from Einstein’s gravity derived and extensively studied in several previous papers. At quantum level the range of theories presented here is superrenormalizable or finite when proper (not affecting the propagator) terms cubic or higher in curvatures are added. Finally, it is proven that for a large class of nonlocal theories, which in their actions do involve neither the Weyl nor the Riemann tensor, the theory is classically equivalent to the Einstein-Hilbert one with a cosmological constant by means of a metric field redefinition at any perturbative order.

Gravitational-wave echoes in the postmerger ringdown phase are under intense scrutiny as probes of near-horizon quantum structures and as signatures of exotic states of matter in ultracompact stars. We present an analytical template that describes the ringdown and the echo signal for nonspinning objects in terms of two physical parameters: the reflectivity and the redshift at the surface of the object. We characterize the properties of the template and adopt it in a preliminary parameter estimation with current (aLIGO) and future (Cosmic Explorer, Einstein Telescope, LISA) gravitational-wave detectors. For fixed signal-to-noise ratio in the postmerger phase, the constraints on the model parameters depend only mildly on the details of the detector sensitivity curve, but depend strongly on the reflectivity. Our analysis suggests that it might be possible to detect or rule out Planckian corrections at the horizon scale for perfectly reflecting ultracompact objects at $5\sigma$ confidence level with Advanced LIGO/Virgo. On the other hand, signal-to-noise ratios in the ringdown phase equal to $\approx 100$ (as achievable with future interferometers) might allow us to probe near-horizon quantum structures with reflectivity $\gtrsim 30\%$ ($\gtrsim 85\%$) at $2\sigma$ ($3\sigma$) level.

We analyze the gamma-ray sky at energies of 0.5 to 50 GeV using the undecimated wavelet transform on the sphere. Focusing on the inner $60°\times 60°$ of the sky, we identify and characterize four separate residuals beyond the expected Milky Way diffuse emission. We detect the Fermi bubbles, finding compelling evidence that they are diffuse in nature and contain very little small-scale structure. We detect the “cocoon” inside the southern bubble, and we also identify its northern counterpart above 2 GeV. The northern cocoon lies along the same axis but is $\sim 30\%$ dimmer than the southern one. We characterize the Galactic center excess, which we find extends up to 20° in $|b|$. At latitudes $|b|\le 5°$ we find evidence for power in small angular scales that could be the result of point-source contributions, but for $|b|\ge 5°$ the Galactic center excess is dominantly diffuse in its nature. Our findings show either that the Galactic center excess and Fermi bubbles connect smoothly or that the bubbles brighten significantly below 15° in latitude. We find that the Galactic center excess appears off-center toward negative $\ell$. Additionally, we find and characterize two emissions along the Galactic disk centered at $\ell \simeq +25°$ and $-20°$. These emissions are significantly more elongated along the Galactic disk than the Galactic center excess.

We observe the decay $\psi (3686)\to n\overline{n}$ for the first time and measure $\psi (3686)\to p\overline{p}$ with improved accuracy by using $1.07\times {10}^8$ $\psi (3686)$ events collected with the BESIII detector. The measured branching fractions are $\mathcal{B}(\psi (3686)\to n\overline{n})=(3.06\pm 0.06\pm 0.14)\times {10}^{-4}$ and $\mathcal{B}(\psi (3686)\to p\overline{p})=(3.05\pm 0.02\pm 0.12)\times {10}^{-4}$. Here, the first uncertainties are statistical, and the second ones are systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey $1+\alpha {\cos }^2\theta$, we determine the $\alpha$ parameters to be ${\alpha }_{n\overline{n}}=0.68\pm 0.12\pm 0.11$ and ${\alpha }_{p\overline{p}}=1.03\pm 0.06\pm 0.03$ for $\psi (3686)\to n\overline{n}$ and $\psi (3686)\to p\overline{p}$, respectively.

The results of a previous search by the CMS Collaboration for squarks and gluinos are reinterpreted to constrain models of leptoquark (LQ) production. The search considers jets in association with a transverse momentum imbalance, using the $M_{\mathrm{T}2}$ variable. The analysis uses proton-proton collision data at $\sqrt{s}=13\mathrm{TeV}$, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of $35.9{\mathrm{fb}}^{-1}$. Leptoquark pair production is considered with LQ decays to a neutrino and a top, bottom, or light quark. This reinterpretation considers higher mass values than the original CMS search to constrain both scalar and vector LQs. Limits on the cross section for LQ pair production are derived at the 95% confidence level depending on the LQ decay mode. A vector LQ decaying with a 50% branching fraction to $t\nu$, and 50% to $b\tau$, has been proposed as part of an explanation of anomalous flavor physics results. In such a model, using only the decays to $t\nu$, LQ masses below 1530 GeV are excluded assuming the Yang-Mills case with coupling $\kappa =1$, or 1115 GeV in the minimal coupling case $\kappa =0$, placing the most stringent constraint to date from pair production of vector LQs.