Canonical quantization of gravitational systems is obstructed by the problem of time. Due to diffeomorphism symmetry the Hamiltonian vanishes: dynamics with respect to a background time parameter appears “frozen.” Two strategies towards the quantization of such systems are the identification of a clock degree of freedom before quantization (deparametrization), and quantization on a kinematical Hilbert space which is subject to constraints (Dirac quantization). The usual canonical quantization in quantum field theory is analogous to deparametrization. Here we introduce a frozen formalism and Dirac quantization for a complex Klein–Gordon scalar field, and show that the resulting theory is equivalent to usual canonical quantization. We then apply the formalism to the group field theory formalism for quantum gravity, for which both deparametrization and a “timeless” quantization have been proposed in past work. We show how a frozen formalism for group field theory links between these two existing approaches, and illustrate in particular the construction of physical observables. We derive effective cosmological dynamics for group field theory in the new formalism and compare these to previous work. The frozen formalism could be extended to other approaches to quantum gravity that do not use a preferred time parameter.

We study the six-dimensional $\mathcal{N}=(1,0)$ supersymmetric model of the interacting gauge multiplet and hypermultiplet with arbitrary self-coupling. Using the background-field method in the harmonic superspace, we calculate the divergent part of the one-loop effective action and discuss the possible finite contribution to the low-energy effective action. We demonstrate that the one-loop divergences do not vanish even in the case of the on-shell background superfields. An application of the developed technique to the hypermultiplet model in four dimensions is briefly discussed.

Using the formalism of the third quantization in canonical quantum gravity, the entropy of entanglement of a pair of universes created in the multiverse from the vacuum has recently been calculated. Here, we examine the differences between considering a scalar field as quantum or classical on the entanglement entropy of three different pairs: de Sitter universes, flat stiff matter dominated universes, and closed universes with a scalar field. We find that the entanglement entropy is unchanged, zero, or dependent on the treatment of the scalar field, respectively.

We discuss cosmological solutions for a diffeomorphism invariant gauge theory of the noncompact Lorentz group $SO(1,3)$. Besides the gauge bosons our model of pregeometry contains a vector field in the vector representation of $SO(1,3)$ and a scalar singlet. General relativity and variable gravity emerge as effective theories for large distances and times in Planck units. We propose an approximation to the effective action with up to two derivatives. For a suitable range of parameters the universe approaches for large times stable Minkowski space. For late cosmology the model predicts dynamical dark energy and provides for a candidate for dark matter. Early cosmology is characterized by an inflationary epoch. The beginning of the universe in the infinite past is great emptiness, corresponding to an ultraviolet fixed point with the associated quantum scale symmetry. The beginning universe is a vacuum state with vanishing expectation values and finite nonvanishing correlation functions for the fluctuations of all fields. There is no physical big bang singularity.

In this paper we analyze the propagation of a charged scalar field in a Reissner-Nordström black hole endowed with one anisotropic fluid that can play the role of a cosmological term for a certain set of parameters. The evolution of a scalar wave scattering is examined, giving rise to the same superradiant scattering condition as in the de Sitter case. In addition, an analysis of the modes coming from the application of quasinormal boundary conditions is presented. Some special cases displaying analytical solutions for the quasinormal frequencies are discussed. Moreover, the superradiant condition is adapted to the quasinormal problem triggering unstable modes, what is confirmed by our numerical analysis.

The rapid accumulation of observed fast radio bursts (FRBs) originating from cosmological distances makes it likely that some will be strongly lensed by intervening matter along the line of sight. Detection of lensed FRB repeaters, which account for a noteworthy fraction of the total population, will allow not only an accurate measurement of the lensing time delay, but also follow-up high-resolution observations to pinpoint the location of the lensed images. Recent works proposed to use such strongly lensed FRBs to derive constraints on the current expansion rate $H_0$ as well as on cosmic curvature. Here, we study the prospects for placing constraints on departures from general relativity via such systems. Using an ensemble of simulated events, we focus on the gravitational slip parameter ${\gamma }_{\mathrm{PN}}$ in screened modified gravity models and show that FRB time-delay measurements can yield constraints as tight as $|{\gamma }_{\mathrm{PN}}-1|\lesssim 0.04\times (\mathrm{\Lambda }/100\mathrm{kpc})\times [N/10{]}^{-1/2}$ at $1\sigma$ with ten detections.

We present cosmological parameter measurements from the effective field theory–based full-shape analysis of the power spectrum of emission line galaxies (ELGs). First, we perform extensive tests on simulations and determine appropriate scale cuts for the perturbative description of the ELG power spectrum. We study in detail nonlinear redshift-space distortions (“fingers of God”) for this sample and show that they are somewhat weaker than those of luminous red galaxies. This difference is not significant for current data but may become important for future surveys like Euclid/DESI. Then, we analyze recent measurements of the ELG power spectrum from the Extended Baryon Acoustic Oscillation Spectroscopic Survey (eBOSS) within the $\nu \mathrm{\Lambda }\mathrm{CDM}$ model. Combined with the big bang nucleosynthesis (BBN) baryon density prior, the ELG pre- and postreconstructed power spectra alone constrain the matter density ${\mathrm{\Omega }}_m=0.257_{-0.045}^{+0.031}$, the current mass fluctuation amplitude ${\sigma }_8=0.571_{-0.076}^{+0.052}$, and the Hubble constant $H_0={84.5}_{-7}^{+5.8}\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ (all at 68% C.L.). Combining with other full-shape and baryon acoustic oscillation (BAO) data, we measure ${\mathrm{\Omega }}_m=0.321_{-0.016}^{+0.013}$, ${\sigma }_8=0.662_{-0.042}^{+0.038}$, and $H_0={68.9}_{-1.1}^{+1}\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. The total neutrino mass is constrained to be $M_{\mathrm{tot}}<0.64\mathrm{eV}$ (95% C.L.) from the BBN, full-shape, and BAO data only. Finally, we discuss the apparent $\sim 3\sigma$ discrepancy in the inferred clustering amplitude between our full shape analysis and the cosmic microwave background data.

Two models that unify warm inflation with dark matter and dark energy are proposed. In the models, a single scalar field is responsible for the early expansion of the Universe through the process of dissipative warm inflation, and then acts as both dark matter and dark energy in subsequent stages. The first model is based on a noncanonical field with the Lagrangian density $\mathcal{L}=F(X)-V(\varphi )$, where the potential is dominant at the slow-roll inflationary epoch and negligible in subsequent stages. The second model takes advantage of a $k$-essence Lagrangian density having the coupled form $\mathcal{L}=F(X)V(\varphi )$. For both models, equations of the evolution for the fields and observational constraints are presented, and an evolution law describing how the energy density $\rho$ and state parameter $w$ scale with the scale factor $a$ is obtained.

We study the observational constraints on single-field inflationary models achievable with the next generation of cosmic microwave background (CMB) experiments. We focus on a Stage IV (S4)-like experiment and forecast its constraints on inflationary parameters in the context of $\alpha$-attractor inflation comprising a large class of single-field models. To tailor our forecasts, we use as a fiducial model the results obtained with current CMB and LSS data, assuming the $\alpha$ model a priori. We find that current CMB data are able to place a tight bound on the ratio of the tensor amplitude with the alpha parameter $r/\alpha =3.87_{-0.94}^{+0.78}\times {10}^{-3}$ and on the running of the scalar index ${\alpha }_S=-6.4_{-1.3}^{+1.6}\times {10}^{-4}$ with a value of the scalar index consistent with current constraints. These tight constraints are the result of the strong bound imposed on $n_s$ by the current cosmological data and the theoretical prior of $\alpha$-attractor models on inflationary observables. This bound can also be translated into an upper bound for $\alpha$. We find $\alpha <25$ and $\alpha <15$, given $r<0.1$ and $r<0.06$ for Planck 2018 and Planck 2018 and BICEP/Keck 2015 data, respectively. In the optimistic scenario of detection of primordial gravitational waves in the CMB $B$-mode polarization, CMB-S4 will be able to achieve a 15% bound on the value of the $\alpha$ parameter. This bound clearly shows the ability of CMB-S4 to constrain not only the energy scale of inflation but also the shape of its potential. Enlarging the baseline model to also include the neutrino sector merely reduces the accuracy on $\alpha$ by about 5%, and thus our main conclusions are still valid. Conversely, in the pessimistic scenario of no detection, a CMB-S4-like experiment will reduce the upper bound on $\alpha$ by around an order of magnitude, leading to a possible exclusion of the Starobinsky model at the level of 6 standard deviations.

We perform the first numerical calculation of the interplay between thermal and black hole induced leptogenesis, demonstrating that the right-handed neutrino surplus produced during the evaporation only partially mitigates the entropy dilution suffered by the thermal component. As such, the intermediate-mass regime of the right-handed neutrinos, ${10}^6\mathrm{GeV}\lesssim M_N\lesssim {10}^9\mathrm{GeV}$, could not explain the observed baryon asymmetry even for fine-tuned scenarios if there existed a primordial black hole dominated era, consistent with initial black hole masses of $M_i\gtrsim \mathcal{O}(1)\mathrm{kg}$ and initial energy density fractions larger than ${\beta }^{\prime }\gtrsim {10}^{-6}$. A possible detection of the gravitational waves emitted from the same primordial black holes would place intermediate-scale thermal leptogenesis under tension. https://github.com/earlyuniverse/ulysses

A non-negligible fraction of the QCD axion dark matter may form gravitationally bound Bose Einstein condensates, which are commonly known as axion stars or axion clumps. Such astrophysical objects have been recently proposed as the cause for the single candidate event reported by Subaru Hyper Suprime-Cam (HSC) microlensing search in the Andromeda galaxy. Depending on the breaking scale of the Peccei-Quinn symmetry and the details of the dark matter scenario, QCD axion clumps may form via gravitational condensation during radiation domination, in the dense core of axion miniclusters, or within axion minihalos around primordial black holes. We analyze all these scenarios and conclude that the microlensing candidate detected by the Subaru HSC survey is likely not caused by QCD axion stars.

As an extension of weak perturbation theory obtained in a recent analysis of infinite-derivative nonlocal non-Abelian gauge theories motivated from $p$-adic string field theory, and postulated as a direction of UV completion in four-dimensional quantum field theory, here we investigate the confinement conditions and $\beta$ function in the strong coupling regime. We extend the confinement criterion, previously obtained by Kugo and Ojima for the local theory based on the Becchi-Rouet-Stora-Tyutin invariance, to the nonlocal theory by using a set of exact solutions of the corresponding local theory. We show that the infinite derivatives which are active in the UV provide finite contributions also in the infrared limit and provide a proof of confinement, granted by the absence of the Landau pole. We also show that in the limit of the energy scale of nonlocality $M\to \infty$ we reproduce the local theory results and see how asymptotic freedom is properly recovered.

Based on the fact that the constituent quark model reproduces the recent lattice result on baryon-baryon repulsion at short distance and that it includes the quark dynamics with confinement, we analyze to what extent the quarkyonic modes appear in the phase space of baryons as one increases the density before only quark dynamics and hence deconfinement occurs. We find that as one increases the baryon density, the initial quark mode that appears will involve the $d(u)$ quark from a neutron (proton), which will leave the most attractive ($ud$) diquark intact.

We investigate the rare electromagnetic decays of neutral vector mesons (exemplified by $J/\psi$, $\mathrm{\Upsilon }$, ${\rho }^0$, $\omega ,\varphi$, …) into four charged leptons [$2(e^{+}{e}^{-})$, $2({\mu }^{+}{\mu }^{-})$, $2({\tau }^{+}{\tau }^{-})$, $e^{+}{e}^{-}{\mu }^{+}{\mu }^{-}$, $e^{+}{e}^{-}{\tau }^{+}{\tau }^{-}$, …] at lowest order in QED. In contrast to the case of vector meson decay into a single pair of leptons, the lepton mass must be retained in these four-lepton decay channels to cut off the mass singularity. Owing to more pronounced collinear enhancement, the branching fractions of vector mesons decays into $2(e^{+}{e}^{-})$ are considerably greater than those for decays into $2({\mu }^{+}{\mu }^{-})$. The decay channels $J/\psi (\mathrm{\Upsilon })\to 2(e^{+}{e}^{-}),e^{+}{e}^{-}{\mu }^{+}{\mu }^{-}$ are predicted to have branching fractions of order ${10}^{-5}$, which appear to have bright observation prospect at BESIII, Belle 2, and LHC experiments.

In the context of the longitudinally boost-invariant Bjorken flow with transverse expansion, we use three different numerical methods to analyze the emergence of attractor solutions in an ideal gas of massless particles exhibiting constant shear viscosity to entropy density ratio $\eta /s$. The fluid energy density is initialized using a Gaussian profile in the transverse plane, while the ratio $\chi ={\mathcal{P}}_L/{\mathcal{P}}_T$ between the longitudinal and transverse pressures is set at initial time ${\tau }_0$ to a constant value ${\chi }_0$ throughout the system employing the Romatschke-Strickland distribution. We introduce the hydrodynamization time $\delta {\tau }_H=({\tau }_H-{\tau }_0)/{\tau }_0$ based on the time ${\tau }_H$ when the standard deviation $\sigma (\chi )$ of a family of solutions with different ${\chi }_0$ reaches a minimum value at the point of maximum convergence of the solutions. In the $0+1\mathrm{D}$ setup, $\delta {\tau }_H$ exhibits scale invariance, being a function only of $(\eta /s)/({\tau }_0{T}_0)$. With transverse expansion, we find a similar $\delta {\tau }_H$ computed with respect to the local initial temperature, $T_0(r)$. We highlight the transition between the regimes where the longitudinal and transverse expansions dominate. We find that the hydrodynamization time required for the attractor solution to be reached increases with the distance from the origin, as expected based on the properties of the $0+1\mathrm{D}$ system defined by the local initial conditions. We argue that hydrodynamization is predominantly the effect of the longitudinal expansion, being significantly influenced by the transverse dynamics only for small systems or for large values of $\eta /s$.

We extend the geneva Monte Carlo framework using the transverse momentum of a color-singlet system as the resolution variable. This allows us to use next-to-next-to-next-to-leading-logarithm (${\mathrm{N}}^3\mathrm{LL}$) resummation via the radish formalism to obtain precise predictions for any color-singlet production process at the fully exclusive level. Thanks to the implementation of two different resolution variables within the geneva framework, we are able to assess the impact of such a choice on differential observables for the first time. As a first application, we present predictions for Drell-Yan lepton-pair production at next-to-next-to-leading order (NNLO) in QCD interfaced to a parton shower simulation that includes additional all-order radiative corrections. We provide fully showered and hadronized events using pythia8, while retaining the NNLO QCD accuracy for observables which are inclusive over the additional radiation. We also show that it is possible to obtain a numerically good agreement between showered geneva predictions and the ${\mathrm{N}}^3\mathrm{LL}$ resummation for the transverse momentum spectrum by choosing a more local recoil scheme. We compare our final predictions to LHC data at 13 TeV, finding good agreement across several distributions.

We propose a unitarity method for determining $\tau$ neutrino appearance probability $P({\nu }_{\mu }\to {\nu }_{\tau })$ in long-baseline (LBL) accelerator experiments and atmospheric neutrino observations. When simultaneous in situ measurements of $P({\nu }_{\mu }\to {\nu }_{\mu })$ and $P({\nu }_{\mu }\to {\nu }_e)$ proceed, as is typical in the LBL experiments, one can use unitarity to “measure” $P({\nu }_{\mu }\to {\nu }_{\tau })$. A theorists’ toy analysis for the model-independent determination of $P({\nu }_{\mu }\to {\nu }_{\mu })$ and $P({\nu }_{\mu }\to {\nu }_e)$ is presented by using the NOvA data. It is shown in our analysis that $\lesssim 5\%$ (8%) measurement of $\tau$ neutrino appearance probability in neutrino (antineutrino) mode is possible in the peak region $1.5\lesssim E_{\nu }\lesssim 2.5\mathrm{GeV}$. The $\nu \mathrm{SM}$-independent nature of determination of the probabilities is emphasized.

We continue the study of supersymmetric domain wall solutions in six-dimensional maximal gauged supergravity. We first give a classification of viable gauge groups with the embedding tensor in ${\mathbf{5}}^{+7}$, ${\overline{\mathbf{5}}}^{+3}$, ${\mathbf{10}}^{-1}$, ${\mathbf{24}}^{-5}$, and ${\overline{\mathbf{45}}}^{+3}$ representations of the off-shell symmetry $GL(5)\subset SO(5,5)$. We determine an explicit form of the embedding tensor for gauge groups arising from each representation together with some examples of possible combinations among them. All of the resulting gauge groups are of a non-semisimple type with Abelian factors and translational groups of different dimensions. We find $\frac{1}{2}$- and $\frac{1}{4}$-supersymmetric domain walls with $SO(2)$ symmetry in $SO(2)⋉{\mathbb{R}}^8$ and $SO(2)⋉{\mathbb{R}}^6$ gauge groups from the embedding tensor in ${\mathbf{24}}^{-5}$ representation and in $CSO(2,0,2)⋉{\mathbb{R}}^4$, $CSO(2,0,2)⋉{\mathbb{R}}^2$, and $CSO(2,0,1)⋉{\mathbb{R}}^4$ gauge groups with the embedding tensor in ${\overline{\mathbf{45}}}^{+3}$ representations. These gauge groups are parametrized by a traceless matrix and electrically and magnetically embedded in $SO(5,5)$ global symmetry, respectively.

We compute the cosmological reduction of general string theories, including bosonic, heterotic, and type II string theory to order ${\alpha }^{\prime 3}$, i.e., with up to eight derivatives. To this end, we refine recently introduced methods that allow one to bring the reduced theory in one dimension to a canonical form with only first-order time derivatives. The resulting theories are compatible with a continuous $O(d,d,\mathbb{R})$ invariance, which in turn fixes the B-field couplings.

We extend the Kerr-Schild double copy to the case of a probe particle moving in the Kerr-Schild background. In particular, we solve Wong’s equations for a test color charge in a Coulomb non-Abelian potential ($\sqrt{\text{Schw}}$) and on the equatorial plane for the potential generated by a rotating disk of charge known as the single copy of the Kerr background ($\sqrt{\text{Kerr}}$). The orbits, as the corresponding geodesics on the gravity side, feature elliptic, circular, hyperbolic and plunge behavior for the charged particle. We then find a new double copy map between the conserved charges on the gauge theory side and the gravity side, which enables us to fully recover geodesic equations for Schwarzschild and Kerr. Interestingly, the map works naturally for both bound and unbound orbits.