We introduce and validate a delensing framework for the Simons Observatory (SO), which will be used to improve constraints on inflationary gravitational waves by reducing the lensing noise in measurements of the $B$ modes in CMB polarization. SO will initially observe CMB by using three small aperture telescopes and one large-aperture telescope. While polarization maps from small-aperture telescopes will be used to constrain inflationary gravitational waves, the internal CMB lensing maps used to delens will be reconstructed from data from the large-aperture telescope. Since lensing maps obtained from the SO data will be noise dominated on subdegree scales, the SO lensing framework constructs a template for lensing-induced $B$ modes by combining internal CMB lensing maps with maps of the cosmic infrared background from Planck as well as galaxy density maps from the LSST survey. We construct a likelihood for constraining the tensor-to-scalar ratio $r$ that contains auto and cross spectra between observed $B$ modes and the lensing $B$-mode template. We test our delensing analysis pipeline on map-based simulations containing survey nonidealities, but that, for this initial exploration, does not include contamination from Galactic and extragalactic foregrounds. We find that the SO survey masking and inhomogeneous and atmospheric noise have very little impact on the delensing performance, and the $r$ constraint becomes $\sigma (r)\approx 0.0015$ which is close to that obtained from the idealized forecasts in the absence of the Galactic foreground and is nearly a factor of 2 tighter than without delensing. We also find that uncertainties in the external large-scale structure tracers used in our multitracer delensing pipeline lead to bias much smaller than the $1\sigma$ statistical uncertainties.

We investigate the ability of the Laser Interferometer Space Antenna (LISA) to detect a stochastic gravitational-wave background (GWB) produced by cosmic strings, and to subsequently estimate the string tension $G\mu$ in the presence of instrument noise, an astrophysical background from compact binaries, and the galactic foreground from white dwarf binaries. Fisher Information and Markov Chain Monte Carlo methods provide estimates of the LISA noise and the parameters for the different signal sources. We demonstrate the importance of including the galactic foreground as well as the astrophysical background for LISA to detect a cosmic string produced GWB and estimate the string tension. Considering the expected astrophysical background and a galactic foreground, a cosmic string tension in the $G\mu \approx {10}^{-16}$ to $G\mu \approx {10}^{-15}$ range or bigger could be measured by LISA, with the galactic foreground affecting this limit more than the astrophysical background. The parameter estimation methods presented here can be applied to other cosmological backgrounds in the LISA observation band.

We discuss the axion dark matter (DM) condensate and the consequences the interactions of dark matter would have on the spectrum of collective modes. We find that DM self-interactions change the spectrum of excitations from a quadratic to a linearlike dispersion with velocity $v_s$ which is set by the interactions, but dominated by gravity. For typical DM densities and interactions we find $v_s\sim {10}^{-12}c$. This soundlike mode corresponds to DM density oscillations just like in any other Bose liquid, hence we call it dark sound (DS). The DS mode is well defined and describes stable density oscillations at intermediate length scales $k\ge k_{\min }\sim {10}^4{\mathrm{lyr}}^{-1}$. In the extreme long-wavelength limit gravity dominates and leads to Jeans instability of the sound mode at the scale of clump formation $k\le k_{\min }$. We also discuss the possible observable consequences of the DS, including quantized DS modes inside clumps, their characteristic energy, and noise features that might facilitate the observation of DM.

We determine the master integrals for vertex and propagator diagrams that appear in effective field theories containing heavy fields. The integrals involve at least one heavy line, and the standard lines include an arbitrary mass scale. The evaluation is done analytically with modern techniques. We employ the methods of differential equations and dimensional recurrence relations to evaluate said integrals up to two-loop order.

We propose a self-interacting dark matter (DM) scenario with a right handed neutrino (RHN) portal to the standard model (SM). The dark sector consists of a particle DM, assumed to be a Dirac fermion, and a light mediator in terms of a dark Abelian vector boson to give rise the required velocity-dependent self-interactions in agreement with astrophysical observations. Irrespective of thermal or nonthermal production of such a DM, its final relic remains underabundant due to efficient annihilation rates of DM into light mediators by virtue of large self-interaction coupling. We then show that a feeble portal of DM-SM interaction via a RHN offers a possibility to fill the relic deficit of DM via the late decay of a RHN. As RHNs also arise naturally in seesaw models explaining the origin of light neutrino masses, we outline two UV-complete realizations of the minimal setup in terms of scotogenic and gauged $B-L$ frameworks where connection to neutrino mass and other phenomenology like complementary discovery prospects are discussed.

We compute the second moments of pion and rho parton distribution functions in lattice QCD with $N_f=2+1$ flavors of improved Wilson fermions. We determine both singlet and nonsinglet flavor combinations and, for the first time, take disconnected contributions fully into account. In the case of the rho, we also calculate the additional contribution arising from the $b_1$ structure function. The numerical analysis includes 26 ensembles, mainly generated by the CLS effort, with pion masses ranging from 420 down to 214 MeV and with 5 different lattice spacings in the range of 0.1 to 0.05 fm. This enables us to take the continuum limit, as well as to resolve the quark mass dependencies reliably. Additionally we discuss the contaminations of rho correlation functions by two-pion states.

We study the $D_s^{*}{\overline{D}}^{*}$ system in connection with the $J/\psi K^{*}$ in coupled channels and observe that, within reasonable values of the cutoff used to regularize the loops, the system does not develop a bound state. However, the $J^P=2^{+}$ channel has enough attraction to create a strong cusp structure that shows up in the $J/\psi K^{+}$ invariant mass distribution in the $B^{+}\to J/\psi \varphi K^{+}$ decay at the $D_s^{*}{\overline{D}}^{*}$ threshold. Such structure is visible in the experimental $B^{+}\to J/\psi \varphi K^{+}$ and ${\overline{B}}^0\to J/\psi K^{+}{K}^{-}$ decays, with small statistics, and our results should stimulate further measurements around this region, given the fact that cusp effects provide as valuable information on hadron dynamics as resonances themselves.

In this paper we study how the exact nonperturbative integrability methods in $4D$ $\mathcal{N}=4$ super-Yang-Mills can work efficiently together with the numerical conformal bootstrap techniques to go beyond the spectral observables and access previously unreachable quantities such as correlation functions at finite coupling. In the setup of 1D defect conformal field theory living on a Maldacena-Wilson line, we managed to compute with good precision a nonsupersymmetric structure constant for a wide range of the ‘t Hooft coupling. Our result is particularly precise at strong coupling and matches well with the recent analytic results of Meneghelli and Ferrero.

In the present paper we address double parton scattering (DPS) in quasireal photon-proton interactions. By using electromagnetic and hadronic models of the photon light cone wave functions, we compute the so-called effective cross section, ${\sigma }_{\mathrm{eff}}^{\gamma p}$ which allows us to calculate the DPS contribution to these processes under dedicated assumptions. In particular, for the four-jet photoproduction in HERA kinematics we found a sizeable DPS contribution. We show that if the photon virtuality $Q^2$ could be measured and thus the dependence of ${\sigma }_{\mathrm{eff}}^{\gamma p}$ on such a parameter exposed, information on the transverse distance between partons active in proton could be extracted. To this aim, we set lower limits on the integrated luminosity needed to observe such an effect which would allow the extraction of novel information on the proton structure.

We study exponentiated soft exchange in ($d+2$)-dimensional gauge and gravitational theories using the celestial conformal field theory formalism. These models exhibit spontaneously broken asymptotic symmetries generated by gauge transformations with noncompact support, and the effective dynamics of the associated Goldstone “edge” mode is expected to be $d$-dimensional. The introduction of an infrared regulator also explicitly breaks these symmetries so the edge mode in the regulated theory is really a $d$-dimensional pseudo-Goldstone boson. Symmetry considerations determine the leading terms in the effective action, whose coefficients are controlled by the infrared cutoff. Computations in this model reproduce the Abelian infrared divergences in $d=2$ and capture the resummed (infrared finite) soft exchange in higher dimensions. The model also reproduces the leading soft theorems in gauge and gravitational theories in all dimensions. Interestingly, we find that it is the shadow transform of the Goldstone mode that has local $d$-dimensional dynamics: the effective action expressed in terms of the Goldstone mode is nonlocal for $d>2$. We also introduce and discuss new magnetic soft theorems. Our analysis demonstrates that symmetry principles suffice to calculate soft exchange in gauge theory and gravity.

We use Higgs bundles to study the 3D $\mathcal{N}=1$ vacua obtained from M-theory compactified on a local $Spin(7)$ space given as a four-manifold $M_4$ of ADE singularities with further generic enhancements in the singularity type along one-dimensional subspaces. There can be strong quantum corrections to the massless degrees of freedom in the low energy effective field theory, but topologically robust quantities such as “parity” anomalies are still calculable. We show how geometric reflections of the compactification space descend to 3D reflections and discrete symmetries. The parity anomalies of the effective field theory descend from topological data of the compactification. The geometric perspective also allows us to track various perturbative and nonperturbative corrections to the 3D effective field theory. We also provide some explicit constructions of well-known 3D theories, including those which arise as edge modes of 4D topological insulators, and 3D $\mathcal{N}=1$ analogs of grand unified theories. An additional result of our analysis is that we are able to track the spectrum of extended objects and their transformations under higher-form symmetries.

The recently developed worldline quantum field theory (WQFT) formalism for the classical gravitational scattering of massive bodies is extended to massive, charged point particles coupling to biadjoint scalar field theory, Yang-Mills theory, and dilaton-gravity theory. We establish a classical double copy relation in these WQFTs for classical observables (deflection, radiation). The biadjoint scalar field theory fixes the locality structure of the double copy from Yang-Mills to dilaton gravity. Using this, the eikonal scattering phase (or free energy of the WQFT) is computed to next-to-leading order (NLO) in coupling constants using the double copy as well as directly finding full agreement. We clarify the relation of our approach to previous studies in the effective field theory formalism. Finally, the equivalence of the WQFT double copy to the double copy relation of the classical limit of quantum scattering amplitudes is shown explicitly up to NLO.

We suggest the $su(1,N|M)$ superconformal mechanics formulated in terms of phase superspace given by the noncompact analogue of complex projective superspace. We parametrized this phase space by the specific coordinates allowing us to interpret it as a higher-dimensional superanalogue of the Lobachevsky plane parametrized by lower half-plane (Klein model). Then we introduced the canonical coordinates corresponding to the known separation of the “radial” and “angular” parts of (super)conformal mechanics. Relating the “angular” coordinates with action-angle variables, we demonstrated that the proposed scheme allows us to construct the $su(1,N|M)$ supeconformal extensions of wide class of superintegrable systems. We also proposed the superintegrable oscillator- and Coulomb-like systems with a $su(1,N|M)$ dynamical superalgebra and found that oscillatorlike systems admit deformed $\mathcal{N}=2M$ Poincaré supersymmetry, in contrast with Coulomb-like ones.

Recent observations of several peculiar over- and underluminous type Ia supernovae infer indirect evidence for the violation of the Chandrasekhar mass limit by suggesting the existence of super- and sub-Chandrasekhar limiting mass white dwarfs. In an attempt to explain these phenomena in the context of general relativistic extensions, we study these objects in Palatini $f(R)$ gravity. We obtain the super- and sub-Chandrasekhar limiting masses as well as the dynamical instability criteria for white dwarfs in the given gravitational theory. We further demonstrate that the conventional positivity condition $\partial M/\partial {\rho }_{\mathrm{c}}>0$ with $M$ being the WD’s mass with central density ${\rho }_{\mathrm{c}}$ is also a valid criterion for stability in Palatini gravity.

We consider a class of stationary and axisymmetric wormhole spacetimes that is closely related to, but not identical with, the class of Teo wormholes. We fix a point $p$ (observation event) and a timelike curve $\gamma$ (worldline of a light source), and we characterize the set of all past-oriented lightlike geodesics from $p$ to $\gamma$. As any such geodesic corresponds to an image of the light source on the observer’s sky, this allows us to investigate the lensing properties of the wormhole. As a main result, we prove with the help of Morse theory that, under very mild conditions on $\gamma$, the observer always sees infinitely many images of $\gamma$. Moreover, we study some qualitative features of the lightlike geodesics with the help of two potentials that determine the sum of centrifugal and Coriolis forces of observers in circular motion for the case that the observers’ velocity approaches the velocity of light. We exemplify the general results with two specific wormhole spacetimes.

The superradiant instability of Kerr-anti–de Sitter black holes is studied by numerically solving the full $3+1$ dimensional Einstein equations. We find that the superradiant instability results in a two stage process with distinct initial and secondary instabilities. At the end of the secondary instability the geometry oscillates at several distinct fundamental frequencies—a multioscillating black hole. The multioscillating black hole is remarkably close to a black resonator, albeit with a bit of gravitational hair. During the hairy black resonator epoch, the evolution of the horizon area is consistent with the exponential approach to a constant. By employing different seed perturbations in the initial Kerr-anti–de Sitter geometry, we also demonstrate that the black resonator’s hair is not unique. In the dual quantum field theory description, rotation invariance is spontaneously broken and the energy density is negative in some regions, signaling an exotic state of matter which does not relax to a stationary configuration.

We consider an action for gravity that, in addition to the Einstein-Hilbert term, contains a function of the Ricci scalar and the Gauss-Bonnet invariant. The specific form of the function considered is motivated by holographic cosmology. At background level the field equations imply modified Friedmann equations of the same form as those in the holographic cosmology. We calculate the cosmological perturbations and derive the corresponding power spectra assuming a general $k$-inflation. We find that the resulting power spectra differ substantially from those obtained in both holographic and standard cosmology. The estimated spectral index and tensor-to-scalar ratio are confronted with the Planck results.

Early dark energy that relieves Hubble tension leaves a fingerprint in the primordial stochastic gravitational wave background that originates from cosmic string network. The signal is not only detectable with future planned gravitational wave experiments, but also distinguishable from other astrophysical and cosmological signals in the gravitational wave frequency spectrum. We find that the cosmic string gravitational wave spectrum can probe other new physics that are generated in post-big bang nucleosynthesis, which extends GW cosmic archaeology search region.

Stochastic gravitational wave backgrounds receive increasing attention and provide a new possibility to directly probe the early Universe. In the preheating process at the end of inflation, parametric resonance can generate large energy density perturbations and efficiently produce gravitational waves (GWs) which carry unique information about inflation. Since the peak frequency of such GWs is approximately proportional to the inflationary energy scale, ${\mathrm{\Lambda }}_{\inf }$, GWs from preheating are expected to be observed by interferometer GW detectors in low-scale inflationary models. We investigate a class of preheating models where the effective potential has a quadratic minimum, and the dependence of the amplitude of such GWs on ${\mathrm{\Lambda }}_{\inf }$, then find that the present energy spectrum of these GWs does not depend on ${\mathrm{\Lambda }}_{\inf }$ except in the case where ${\mathrm{\Lambda }}_{\inf }$ is above a critical value ${\mathrm{\Lambda }}_c$—a parameter depending on the resonance strength. We numerically obtain ${\mathrm{\Lambda }}_c$ in terms of the model parameters in a linear approximation and then conduct lattice simulations to verify this result. For ${\mathrm{\Lambda }}_{\inf }\lesssim {\mathrm{\Lambda }}_c$, the amplitude of GWs quickly decreases with ${\mathrm{\Lambda }}_{\inf }$ and becomes challenging to observe. In turn, observing such GWs in interferometer detectors also helps to determine ${\mathrm{\Lambda }}_{\inf }$ and the resonance strength during the preheating.