Deep convolutional neural networks (CNNs) show strong promise for analyzing scientific data in many domains including particle imaging detectors such as a liquid argon time projection chamber (LArTPC). Yet the high sparsity of LArTPC data challenges traditional CNNs which were designed for dense data such as photographs. A naive application of CNNs on LArTPC data results in inefficient computations and a poor scalability to large LArTPC detectors such as the Short Baseline Neutrino Program and Deep Underground Neutrino Experiment. Recently, submanifold sparse convolutional networks (SSCNs) have been proposed to address this class of challenges. We report their performance on a three-dimensional (3D) semantic segmentation task on simulated LArTPC samples. In comparison with standard CNNs, we observe that the computation memory and wall-time cost for inference are reduced by a factor of 364 and 33, respectively, without loss of accuracy. The same factors for 2D samples are found to be 93 and 3.1, respectively. Using SSCN and public 3D LArTPC samples, we present the first machine learning-based approach to the reconstruction of Michel electrons, a standard candle for energy calibration in LArTPC due to their very well-understood energy spectrum. We find a Michel electrons identification efficiency of 93.9% and a 96.7% purity. Reconstructed Michel electron clusters yield 95.4% in average pixel clustering efficiency and 95.5% in purity. The results are compelling in showing the strong promise of scalable data reconstruction technique using deep neural networks for large scale LArTPC detectors.

In this work we define a new type of flux operators on the Hilbert space of loop quantum gravity. We use them to solve an equation of the form $F(A)=c\mathrm{\Sigma }$ in loop quantum gravity. This equation, which relates the curvature of a connection $A$ with its canonical conjugate $\mathrm{\Sigma }=*E$, plays an important role for spherically symmetric isolated horizons, and, more generally, for maximally symmetric geometries and for the Kodama state. If the equation holds, the new flux operators can be interpreted as a quantization of surface holonomies from higher gauge theory. Also, they represent a kind of quantum deformation of SU(2). We investigate their properties and discuss how they can be used to define states that satisfy the isolated horizon boundary condition in the quantum theory.

Direct detection of dark energy or modified gravity may finally be within reach due to ultrasensitive instrumentation such as atom interferometry capable of detecting incredibly small scale accelerations. Forecasts, constraints and measurement bounds can now too perhaps be estimated from accurate numerical simulations of the fifth force and its Laplacian field at solar system scales. The cubic Galileon gravity scalar field model (CGG), which arises in various massive gravity models including the Dvali-Gabadadze-Porrati (DGP) braneworld model, describes modified gravity incorporating a Vainshtein screening mechanism. The nonlinear derivative interactions in the CGG equation suppress the field near regions of high density, thereby restoring general relativity (GR) while far from such regions, field enhancement is comparable to GR and the equation is dominated by a linear term. This feature of the governing equation poses some numerical challenges for computation of the scalar potential, force and Laplacian fields even under stationary conditions. Here we present a numerical method based on finite differences for solution of the static CGG scalar field for a 2D axisymmetric Sun-Earth system and a 3D Cartesian Sun-Earth-Moon system. The method relies on gradient descent of an integrated residual based on the normal attractive branch of the CGG equation. The algorithm is shown to be stable, accurate and rapidly convergent toward the global minimum state. We hope this numerical study, which can easily be extended to include smaller bodies such as detection satellites, will prove useful to future measurement of modified gravity force fields at solar system scales.

We investigate stationary, spherically symmetric accretion of the relativistic Vlasov gas on Reissner-Nordström black holes. The model is based on a recent analysis done by Rioseco and Sarbach for the Schwarzschild spacetime. Both models share many common features: The gas characterized by the Maxwell-Jüttner distribution at infinity is no longer in thermal equilibrium in the vicinity of the black hole. The radial pressure at the black hole horizon can even be an order of magnitude smaller than the tangential pressure. Quantitative characteristics of the Reissner-Nordström model depend on the charge parameter. For black holes with fixed asymptotic mass, the mass accretion rate decreases with the increasing black hole charge. The ratio of the tangential pressure to the radial pressure at the horizon also decreases with the increasing charge. On the other hand, the particle density at the horizon (normalized by its asymptotic value) grows with the black hole charge parameter.

The tidal deformations of neutron stars within an inspiraling compact binary alter the orbital dynamics, imprinting a signature on the gravitational wave signal. Modeling this signal could be done with numerical-relativity simulations, but these are too computationally expensive for many applications. Analytic post-Newtonian treatments are limited by unknown higher-order nontidal terms. This paper further builds upon the “tidal splicing” model in which post-Newtonian tidal terms are “spliced” onto numerical relativity simulations of black-hole binaries. We improve on previous treatments of tidal splicing by including spherical harmonic modes beyond the (2,2) mode, expanding the post-Newtonian expressions for tidal effects to 2.5 order, including dynamical tide corrections, and adding a partial treatment of the spin-tidal dynamics. Furthermore, instead of numerical relativity simulations, we use the spin-aligned binary black hole (BBH) surrogate model “NRHybSur3dq8” to provide the BBH waveforms that are input into the tidal slicing procedure. This allows us to construct spin-aligned, inspiraling TaylorT2 and TaylorT4 splicing waveform models that can be evaluated quickly. These models are tested against existing binary neutron star and black hole–neutron star simulations. We implement the TaylorT2 splicing model as an extension to “NRHybSur3dq8,” creating a model that we call “NRHybSur3dq8Tidal.”

The paper studies a new type of dark energy, a scalar field with positive or negative kinetic energy, generically coupled to a term which is composed by specific contractions of the Riemann tensor. After presenting the resulting field equations, we have analyzed the physical characteristics of the corresponding model by implementing the linear stability theory. In the case of an exponential coupling function and exponential potential energy, we have deduced the phase space characteristics, analyzing the critical points obtained which can represent specific eras in the evolution of the Universe. The analytical study is showing that this model can represent a feasible cosmological setup, having various epochs which correspond to stiff-fluid, matter domination, and dark energy eras, pointing toward the emergence of the accelerated expansion as a geometrical effect.

The hypothesis that pulsar wind nebulae (PWNe) can significantly contribute to the excess of the positron ($e^{+}$) cosmic-ray flux has been consolidated after the observation of a $\gamma$-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe, and at GeV energies for Geminga at a much larger extension. The $\gamma$-ray halos around these PWNe are interpreted as due to electrons ($e^{-}$) and $e^{+}$ accelerated and escaped by their PWNe, and inverse Compton scattering low-energy photons of the interstellar radiation fields. The extension of these halos suggests that the diffusion around these PWNe is suppressed by 2 orders of magnitude with respect to the average in the Galaxy. We implement a two-zone diffusion model for the propagation of $e^{+}$ accelerated by the Galactic population of PWNe. We consider pulsars from source catalogs and build up simulations of the PWN Galactic population. In both scenarios, we find that within a two-zone diffusion model, the total contribution from PWNe and secondary $e^{+}$ is at the level of AMS-02 data, for an efficiency of conversion of the pulsar spin-down energy in $e^{\pm }$ of $\eta \sim 0.1$. For the simulated PWNe, a $1\sigma$ uncertainty band is determined, which is of at least 1 order of magnitude from 10 GeV up to few TeV. The hint for a decreasing $e^{+}$ flux at TeV energies is found, even if it is strongly connected to the chosen value of the radius of the low diffusion bubble around each source.

In this work we study the production of $K^{*}(4307)$ in $B$ decays by determining the $J/\psi {\pi }^{+(0)}{K}^0$ and $J/\psi {\pi }^{-}{K}^{+}$ invariant mass distributions of the processes $B^{+}\to J/\psi {\pi }^{+}{\pi }^0{K}^0$ and $B^{+}\to J/\psi {\pi }^{+}{\pi }^{-}{K}^{+}$, respectively. Such $K^{*}(4307)$ has been recently predicted as a three-body state originating from the dynamics involved in the $KD{\overline{D}}^{*}$ system, with the $KD$ subsystem forming the $D_{s0}^{*}(2317)$ in isospin 0, and the $D{\overline{D}}^{*}$ subsystem generating the $X(3872)$ in isospin 0 and the $Z_c(3900)$ in isospin 1. The hidden charm content of $K^{*}(4307)$ favors its decay to a state like $J/\psi \pi K$ and the study of $B$ decays with these particles in their final states can constitute a way of finding experimental evidence for such an exotic vector meson, whose width—in spite of its large mass—is still quite narrow (around 18 MeV).

A zero initial velocity of the axion field is assumed in the conventional misalignment mechanism. We propose an alternative scenario where the initial velocity is nonzero, which may arise from an explicit breaking of the Peccei-Quinn (PQ) symmetry in the early Universe. We demonstrate that, depending on the specifics of the initial velocity and the time order of the PQ symmetry breaking vs inflation, this new scenario can either enhance or suppress the axion relic abundance relative to the conventional prediction. As a result, new viable parameter regions for axion dark matter may open up.

We present an effective field theory for doubly heavy baryons that goes beyond the compact heavy diquark approximation. The heavy quark distance $r$ is only restricted to $m_Q\gg 1/r\gg E_{\text{bin}}$, where $m_Q$ is the mass of the heavy quark and $E_{\text{bin}}$ the typical binding energy. This means that the size of the heavy diquark can be as large as the typical size of a light hadron. We start from nonrelativistic QCD, and build the effective field theory at next-to-leading order in the $1/m_Q$ expansion. At leading order the effective field theory reduces to the Born-Oppenheimer approximation. The Born-Oppenheimer potentials are obtained from available lattice QCD data. The spectrum for double charm baryons below threshold is compatible with most of the lattice QCD results. We present for the first time the full spin averaged double bottom baryon spectrum below threshold based on QCD. We also present model-independent formulas for the spin splittings.

We propose an effective field theory to describe hadrons with two heavy quarks without any assumption on the typical distance between the heavy quarks with respect to the typical hadronic scale. The construction is based on nonrelativistic QCD and inspired in the strong coupling regime of potential nonrelativistic QCD. We construct the effective theory at leading and next-to-leading order in the inverse heavy quark mass expansion for arbitrary quantum numbers of the light degrees of freedom. Hence our results hold for hybrids, tetraquarks, double heavy baryons and pentaquarks, for which we also present the corresponding operators at a nonrelativistic level. At leading order, the effective theory enjoys heavy quark spin symmetry and corresponds to the Born-Oppenheimer approximation. At next-to-leading order, spin and velocity-dependent terms arise, which produce splittings in the heavy quark spin symmetry multiplets. A concrete application to double heavy baryons is presented in an accompanying paper.

The cross section of neutrino-induced neutral-current coherent ${\pi }^0$ production on a carbon-dominated target is measured in the NOvA near detector. This measurement uses a narrow-band neutrino beam with an average neutrino energy of 2.7 GeV, which is of interest to ongoing and future long-baseline neutrino oscillation experiments. The measured, flux-averaged cross section is $\sigma =13.8\pm 0.9(\mathrm{stat})\pm 2.3(\mathrm{syst})\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleus}$, consistent with model prediction. This result is the most precise measurement of neutral-current coherent ${\pi }^0$ production in the few-GeV neutrino energy region.

To model the interior of a black hole, a study is made of a spin system with long-range random four-spin couplings that exhibits quantum chaos. The black hole limit corresponds to a system where the microstates are approximately degenerate and equally likely, corresponding to the high temperature limit of the spin system. At the leading level of approximation, reconstruction of bulk physics implies that local probes of the black hole should exhibit free propagation and unitary local evolution. We test the conjecture that a particular mean field Hamiltonian provides such a local bulk Hamiltonian by numerically solving the exact Schrodinger equation and comparing the time evolution to the approximate mean field time values. We find excellent agreement between the two time evolutions for timescales smaller than the scrambling time. In earlier work, it was shown bulk evolution along comparable time slices is spoiled by the presence of the curvature singularity, thus the matching found in the present work provides evidence of the success of this approach to interior holography. The numerical solutions also provide a useful testing ground for various measures of quantum chaos and global scrambling. A number of different observables, such as entanglement entropy, out-of-time-order correlators, and trace distance are used to study these effects. This leads to a suitable definition of scrambling time, and evidence is presented showing a logarithmic variation with the system size.

We explore the interplay of matter with quantum gravity with a preferred frame to highlight that the matter sector cannot be protected from the symmetry-breaking effects in the gravitational sector. Focusing on Abelian gauge fields, we show that quantum gravitational radiative corrections induce Lorentz-invariance-violating couplings for the Abelian gauge field. In particular, we discuss how such a mechanism could result in the possibility to translate observational constraints on Lorentz violation in the matter sector into strong constraints on the Lorentz-violating gravitational couplings.

The notion of a unique integrand does not a priori makes sense in field theory: different Feynman diagrams have different loop momenta and there should be no reason to compare them. In string theory, however, a global integrand is natural and allows one, for instance, to make explicit the separation between left- and right-moving degrees of freedom. However, the significance of this integrand had not really been investigated so far. It is even more important in view of the recently discovered loop monodromies that are related to the duality between color and kinematics in gauge and gravity loop amplitudes. This paper intends to start filling this gap, by presenting a careful definition of the loop momentum in string theory and describing precisely the resulting global integrand obtained in the field-theory limit. We will then apply this technology to write down some monodromy relations at two and three loops and make contact with the color-kinematics duality.

We consider black hole interiors of arbitrary genus number within the paradigm of noncommutative geometry. The study is performed in two ways: One way is a simple smearing of a matter distribution within the black hole. The resulting structure is often known in the literature as a “model inspired by noncommutative geometry.” The second method involves a more fundamental approach, in which the Hamiltonian formalism is utilized and a nontrivial Poisson bracket is introduced between the configuration degrees of freedom, as well as between the canonical momentum degrees of freedom. This is done in terms of connection variables instead of the more common ADM variables. Connection variables are utilized here since noncommutative effects are usually inspired from the quantum theory, and it is the connection variables that are used in some of the more promising modern theories of quantum gravity. We find that in the first study, the singularity of the black holes can easily be removed. In the second study, we find that introducing a nontrivial bracket between the connections (the configuration variables) may delay the singularity, but not necessarily eliminate it. However, by introducing a nontrivial bracket between the densitized triads (the canonical momentum variables), the singularity can generally be removed. In some cases, new horizons also appear due to the noncommutativity.

In a recent paper [R. Brandenberger and Z. Wang, Phys. Rev. D 101, 063522 (2020)] we proposed a mechanism for a continuous transition between a contracting ekpyrotic phase and the standard big bang phase of expansion: the bounce is generated by an S-brane which represents the effects of higher-mass string states in the low-energy effective field theory. We showed that gravitational waves on cosmological scales obtain a nearly scale-invariant spectrum. Here, we study the cosmological fluctuations in this setup, assuming that the S-brane has zero shear. We find a nearly scale-invariant spectrum of cosmological perturbations with a slight red tilt. The scenario yields two consistency relations for cosmological observations: one relating the tensor-to-scalar ratio with the scalar spectral tilt, and one relating the tensor tilt to the scalar tilt. The predicted tensor-to-scalar ratio is within the reach of upcoming cosmic microwave background observations. The tensor tilt is blue.

The baryon acoustic oscillation (BAO) scale acts as a standard ruler for measuring cosmological distances and has therefore emerged as a leading probe of cosmic expansion history. However, any physical effect that alters the length of the ruler can lead to a bias in our determination of distance and expansion rate. One of these physical effects is the streaming velocity, the relative velocity between baryons and dark matter in the early Universe, which couples to the BAO scale due to their common origin in acoustic waves at recombination. In this work, we investigate the impact of streaming velocity on the BAO feature of the Lyman-$\alpha$ forest auto-power spectrum, one of the main tracers being used by the recently commissioned Dark Energy Spectroscopic Instrument (DESI). To do this, we develop a perturbative model for Lyman-$\alpha$ flux fluctuations which is complete to second order for a certain set of fields, and applicable to any redshift-space tracer of structure since it is based only on symmetry considerations. We find that there are 8 biasing coefficients through second order. We find streaming velocity-induced shifts in the BAO scale of 0.081%–0.149% (transverse direction) and 0.053%–0.058% (radial direction), depending on the model for the biasing coefficients used. These are smaller than, but not negligible compared to, the DESI Lyman-$\alpha$ BAO error budget, which is 0.46% on the overall scale. The sensitivity of these results to our choice of bias parameters underscores the need for future work to measure the higher-order biasing coefficients from simulations, especially for future experiments beyond DESI.

Supermassive black holes are commonly found in the centers of galaxies and evolve with their hosts. Supermassive binary black holes (SMBBH) are thus expected to exist in close galaxy pairs; however, none has been unequivocally detected. The square kilometer array (SKA) is a multipurpose radio telescope with a collecting area approaching ${10}^6$ square meters, with great potential for detecting nanohertz gravitational waves (GWs). In this paper, we quantify the GW detectability by SKA for a realistic SMBBH population using a pulsar timing array (PTA) technique, and we quantify its impact on revealing SMBBH evolution with redshift for the first time. With only $\sim 20$ pulsars, a much smaller requirement than in previous work, the SKAPTA is expected to obtain detection within about 5 years of operation and to achieve a detection rate of more than 100 SMBBHs/yr after about 10 years. Although beyond the scope of this paper, we must acknowledge that the presence of persistent red noise will reduce the number of expected detections here. It is thus imperative to understand and mitigate red noise in the PTA data. The GW signatures from a few well-known SMBBH candidates, such as OJ 287, 3C 66B, NGC 5548, and Ark 120, will be detected given the currently best-known parameters of each system. Within 30 years of operation, about 60 individual SMBBH detections with $z<0.05$ and more than ${10}^4$ with $z<1$ are expected. The detection rate drops precipitately beyond $z=1$. The substantial number of expected detections and their discernible evolution with redshift by the SKAPTA will make SKA a significant tool for studying SMBBHs.

We consider a general class of axion models, including the QCD and string axion, in which the PQ symmetry is broken before or during inflation. Assuming the axion is the dominant component of the dark matter, we discuss axion star formation in virialized dark minihalos around primordial black holes through gravitational Bose-Einstein condensation. We determine the conditions for minihalos to kinetically produce axion stars before galaxy formation. Today, we expect up to $\sim {10}^{17}$ ($\sim {10}^9$) axion stars in a radius of 100 parsecs around the Sun for the case of the QCD (string) axion.