The most promising indirect search for the existence of axion dark matter uses radio telescopes to look for narrow spectral lines generated from the resonant conversion of axions in the magnetospheres of neutron stars. Unfortunately, a large list of theoretical uncertainties has prevented this search strategy from being fully accepted as robust. In this work we attempt to address major outstanding questions related to the role and impact of the plasma, including: (i) does refraction and reflection of radio photons in the magnetosphere induce strong inhomogeneities in the flux, (ii) can refraction induce premature axion-photon dephasing, (iii) to what extent do photon-plasma interactions induce a broadening of the spectral line, (iv) does the flux have a strong time dependence, and ($v$) can radio photons sourced by axions be absorbed by the plasma. We present an end-to-end analysis pipeline based on ray-tracing that exploits a state-of-the-art auto-differentiation algorithm to propagate photons from the conversion surface to asymptotically large distances. Adopting a charge symmetric Goldreich-Julian model for the magnetosphere, we show that for reasonable parameters one should expect a strong anisotropy of the signal, refraction induced axion-photon dephasing, significant line-broadening, a variable time-dependence of the flux, and, for large enough magnetic fields, anisotropic absorption. Our simulation code is flexible enough to serve as the basis for follow-up studies with a large range of magnetosphere models.

We produce the light-front wave functions (LFWFs) of the nucleon from a basis light-front approach in the leading Fock-sector representation. We solve for the mass eigenstates from a light-front effective Hamiltonian, which includes a confining potential adopted from light-front holography in the transverse direction, a longitudinal confinement, and a one-gluon exchange interaction with fixed coupling. We then employ the LFWFs to obtain the electromagnetic and axial form factors, the parton distribution functions (PDFs), and the generalized parton distribution functions for the nucleon. The electromagnetic and axial form factors of the proton agree with the experimental data, whereas the neutron form factors deviate somewhat from the experiments in the low-momentum transfer region. The unpolarized, the helicity, and the transversity valence quark PDFs, after QCD scale evolution, are fairly consistent with the global fits to the data at the relevant experimental scales. The helicity asymmetry for the down quark also agrees well with the measurements; however, the asymmetry for the up quark shows a deviation from the data, especially in the small $x$ region. We also find that the tensor charge agrees well with the extracted data and the lattice QCD predictions, while the axial charge is somewhat outside the experimental error bar. The electromagnetic radii of the protons, the magnetic radius of the neutron, and the axial radius are in excellent agreement with the measurements, while the neutron charge radius deviates from the experiment.

Some parts of the substellar evolution, such as fragmentation of a gaseous cloud and a Jupiter-like planet’s cooling, are demonstrated to be impacted by Palatini $f(\overline{R})$ gravity. Using simple models describing those processes we show that the opacity mass limit as well as cooling time of jovian planets differ in modified gravity.

We investigate the minimal theory of massive gravity (MTMG) in the light of different observational datasets that are in tension within the $\mathrm{\Lambda }$ cold dark matter cosmology. In particular, we analyze the MTMG model, for the first time, with the Planck–cosmic microwave background (CMB) data, and how these precise measurements affect the free parameters of the theory. The MTMG model can affect the CMB power spectrum at large angular scales and cause a suppression on the amplitude of the matter power spectrum. We find that on adding Planck-CMB data, the graviton has a small, positive, but nonzero mass at 68% confidence level, and from this perspective, we show that the tension between redshift space distortions measurements and Planck-CMB data in the parametric space $S_8-{\mathrm{\Omega }}_m$ can be resolved within the MTMG scenario. Through a robust and accurate analysis, we find that the $H_0$ tension between the CMB and the local distance ladder measurements still remains but can be reduced to $\sim 3.5\sigma$ within the MTMG theory. The MTMG is very well consistent with the CMB observations, and undoubtedly, it can serve as a viable candidate among other modified gravity theories.

We study stable circular orbits (SCO) around static spherically symmetric configuration of general relativity with a nonlinear scalar field (SF). The configurations are described by solutions of the Einstein-SF equations with monomial SF potential $V(\varphi )=|\varphi {|}^{2n}$, $n>2$, under the conditions of the asymptotic flatness and behavior of SF $\varphi \sim 1/r$ at spatial infinity. We proved that under these conditions, the solution exists and is uniquely defined by the configuration mass $M>0$ and scalar “charge” $Q$. The solutions and the space-time geodesics have been investigated numerically in the range $n\le 40$, $|Q|\le 60$, $M\le 60$. We focus on how nonlinearity of the field affects properties of SCO distributions (SCOD), which, in turn, affect topological form of the thin accretion disk around the configuration. Maps are presented showing the location of possible SCOD types for different $M$, $Q$, $n$. We found a lot of differences from the Fisher-Janis-Newman-Winicour metric (FJNW) dealing with the linear SF, though basic qualitative properties of the configurations have much in common with the FJNW case. For some values of $n$, a topologically new SCOD type was discovered that is not available for the FJNW metric. Like FJNW, all images of accretion disks have a dark spot in the center (mimicking the ordinary black hole), either because there is no SCO near the center or due to the strong deflection of photons near the singularity, although fine features other than a black hole can appear with a special choice of $M$, $Q$.

The Radar Echo Telescope for Cosmic Rays (RET-CR) is a recently funded experiment designed to detect the englacial cascade of a cosmic ray-initiated air shower via in-ice radar, toward the goal of a full-scale, next-generation experiment to detect ultrahigh energy neutrinos in polar ice. For cosmic rays with a primary energy greater than 10 PeV, roughly 10% of an air shower’s energy reaches the surface of a high elevation ice sheet ($\gtrsim 2\dot{\mathrm{k}}\mathrm{m}$) concentrated into a radius of roughly 10 cm. This penetrating shower core creates an in-ice cascade orders of magnitude more dense than the preceding in-air cascade. This dense cascade can be detected via the radar echo technique, where transmitted radio waves are reflected from the ionization deposit left in the wake of the cascade. RET-CR will test the radar echo method in nature, with the in-ice cascade of a cosmic ray-initiated air shower serving as a test beam. We present the projected event rate and sensitivity based upon a three part simulation using corsika, geant4, and radioscatter. RET-CR expects $\sim 1\mathrm{rad}\mathrm{ar}$ echo event per day.

We reanalyze the results of the searches for Heavy Neutral Leptons (HNLs) by the CHARM experiment. We study HNL decay channel $N\to e^{+}{e}^{-}\nu /{\mu }^{+}{\mu }^{-}\nu$ and show that, in addition to the constraints on the HNL’s mixings with ${\nu }_e$ or ${\nu }_{\mu }$, the same data also implies limits on the HNLs that mix only with ${\nu }_{\tau }$ and have masses in the range $290\mathrm{MeV}<m_N\lesssim 1.6\mathrm{GeV}$: the region in the parameter space that was considered in the literature as a target for HNLs searches.

In the future, ab initio quantum simulations of heavy ion collisions may become possible with large-scale fault-tolerant quantum computers. We propose a quantum algorithm for studying these collisions by looking at a class of observables requiring dramatically smaller volumes: transport coefficients. These form nonperturbative inputs into theoretical models of heavy ions; thus, their calculation reduces theoretical uncertainties without the need for a full-scale simulation of the collision. We derive the necessary lattice operators in the Hamiltonian formulation and describe how to obtain them on quantum computers. Additionally, we discuss ways to efficiently prepare the relevant thermal state of a gauge theory.

The hidden-charm tetraquarks with strangeness, $c\overline{c}s\overline{q}$ ($q=u$, $d$), in $J^P=0^{+}$, $1^{+}$, and $2^{+}$ are systematically investigated in the framework of real- and complex-scaling range of a chiral quark model, whose parameters have been fixed in advance describing hadron, hadron-hadron, and multiquark phenomenology. Each tetraquark configuration, compatible with the quantum numbers studied, is taken into account; this includes meson-meson, diquark-antidiquark, and K-type arrangements of quarks with all possible color wave functions in the four-body sector. Among the different numerical techniques to solve the Schrödinger-like four-body bound state equation, we use a variational method in which the trial wave function is expanded in complex-range Gaussian basis functions, which is characterized by its simplicity and flexibility. This theoretical framework has already been used to study different kinds of multiquark systems, such as the hidden-charm pentaquarks $P_c^{+}$ and doubly charmed tetraquarks $T_{cc}^{+}$. The recently reported $Z_{cs}$ states by the BESIII and LHCb Collaborations could be associated, in our investigation, with either compact tetraquark or hadronic molecular resonance configurations. However, it is fair to recognize that our complex poles survive when either the $(c\overline{c})(s\overline{q})$ or $(c\overline{q})(s\overline{c})$ configuration is preserved, but most of them get diluted when both are considered at the same time, indicating that such states seem to be very unstable. Finally, we mention that similar types of structures are also found in the mass range between 3.8 and 4.6 GeV.

Inverse muon decay, ${\nu }_{\mu }{e}^{-}\to {\mu }^{-}{\nu }_e$, is a reaction whose cross section can be predicted with very small uncertainties. It has a neutrino energy threshold of $\approx 11\mathrm{GeV}$ and can be used to constrain the high-energy part of the flux in the NuMI neutrino beam. This reaction is the dominant source of events which only contain high-energy muons nearly parallel to the direction of the neutrino beam. We have isolated a sample of hundreds of such events in neutrino and antineutrino enhanced beams, and have constrained the predicted high-energy flux.

LUX-ZEPLIN is a dark matter detector expected to obtain world-leading sensitivity to weakly-interacting massive particles interacting via nuclear recoils with a $\sim 7$-tonne xenon target mass. This paper presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment, and 2) an effective neutrino millicharge, both for $pp$-chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axionlike particles forming the Galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6 t 1000 d exposure and low expected rate of electron-recoil backgrounds in the $<100\mathrm{keV}$ energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout.

By using the quantum extremal island formula, we perform a simple calculation of the generalized entanglement entropy of Hawking radiation from the two-dimensional Liouville black hole. No reasonable island was found when extremizing the generalized entropy. We explain qualitatively the reason why the page curve cannot be reproduced in the present model. This suggests that the islands may not necessarily save the information paradox for the Liouville black holes.

The vacuum transition probabilities for anisotropic universes in the presence of a scalar field potential in the Wentzel-Kramers-Brillouin approximation are studied. We follow the work by Cespedes et al. [Phys. Rev. D 104, 026013 (2021)], which discuss these transitions in the isotropic context using the Wheeler-DeWitt equation, the Lorentzian Hamiltonian approach and the thin wall limit. First, we propose a general procedure to adapt their formalism to compute the decay rates for any superspace model. Then we apply it to compute the transition probabilities of an Friedmann-Lemaitre-Robertson-Walker (FLRW) metric with both positive and zero curvature, reproducing in this way one of the results obtained at Cespedes et al. We then proceed to apply the formalism to three anisotropic metrics, namely, Kantowski-Sachs, Bianchi III and biaxial Bianchi IX to compute the rate decays for these three cases. In the process we find that this method involves some conditions which relates the effective number of independent degrees of freedom resulting on all probabilities being described with only two independent variables. For the Bianchi III metric, we find that a general effect of anisotropy is to decrease the transition probability as the degree of anisotropy is increased, having as the isotropic limit the flat FLRW result.

We consider the communication of classical and quantum information between two arbitrary observers in asymptotically flat spacetimes (possibly containing black holes) and investigate what the energy cost is for such information transmission. By means of localized two-level quantum systems, sender and receiver can use a quantum scalar field as a communication channel. As we have already shown in a previous paper, such a channel has nonvanishing classical capacity as well as entanglement-assisted classical and quantum capacities. Here we will show that the change in the expectation value of the energy of the system during the communication process can be separated in (i) a contribution coming from the particle creation due to the change of the spacetime, (ii) a contribution associated with the energy needed to switch on or off each qubit, and (iii) a term which comes from the communication process itself. For the quantum channel considered here, we show that the extra energy cost needed for communication vanishes. As a result, if one has already created a system of qubits for some specific task (e.g., quantum computation), one can also reliably convey information between its parts with no extra energy cost. We conclude the paper by illustrating the form of the channel capacities and energy contributions in two paradigmatic cases in Minkowski spacetime: (i) sender and receiver in inertial motion and (ii) sender in inertial motion while the receiver is uniformly accelerated.

Recently it was shown that the scaling dimension of the operator ${\varphi }^n$ in $\lambda (\overline{\varphi }\varphi {)}^2$ theory may be computed semiclassically at the Wilson-Fisher fixed point in $d=4-\epsilon$, for generic values of $\lambda n$, and this was verified to two loop order in perturbation theory at leading and subleading $n$. This result was subsequently generalized to operators of fixed charge $Q$ in $O(N)$ theory and verified up to four loops in perturbation theory at leading and subleading $Q$. More recently, similar semiclassical calculations have been performed for the classically scale-invariant $U(N)\times U(N)$ theory in four dimensions, and verified up to two loops, once again at leading and subleading $Q$. Here we extend this verification to four loops. We also consider the corresponding classically scale-invariant theory in three dimensions, similarly verifying the leading and subleading semiclassical results up to four loops in perturbation theory.

We investigate thermodynamic aspects of black holes in the recently formulated four-dimensional Gauss-Bonnet theory of gravity, focusing on its asymptotically de Sitter ($\mathrm{\Lambda }>0$) solutions. We take a Euclidean path integral approach, where thermodynamic data is fixed at a finite radius “cavity” outside the black hole to achieve equilibrium in the presence of the cosmological horizon. Working in the extended phase space where the cosmological constant is treated as a thermodynamic pressure, we study the phase structure of both uncharged and charged solutions, uncovering a wealth of phenomena. In the uncharged case, black holes are found to undergo either the standard Hawking-Page-like transition to empty de Sitter space or a small-large transition (akin to those seen in charged AdS black holes in pure Einstein gravity) depending on the pressure. We also find a triple point where the radiation, small, and large black hole phases coexist, and a zeroth-order phase transition within a narrow range of the Gauss-Bonnet coupling parameter. Reentrant phase transitions between radiation and a small black hole also exist inside a certain parameter range. Similar phenomena are found in the charged case, with the charge parameter playing a role analogous to the Gauss-Bonnet coupling in determining the phase structure.

Inferring the source properties of a gravitational wave signal has traditionally been very computationally intensive and time consuming. In recent years, several techniques have been developed that can significantly reduce the computational cost while delivering rapid and accurate parameter inference. One of the most powerful of these techniques is the heterodyned likelihood, which uses a reference waveform to base band the likelihood calculation. Here, an efficient implementation of the heterodyned likelihood is presented that can be used for a wide range of signal types and for both ground-based and space-based interferometers. The computational savings relative to direct calculation of the likelihood vary between two and four orders of magnitude depending on the system. The savings are greatest for low mass systems such as neutron star binaries. The heterodyning procedure can incorporate marginalization over calibration uncertainties and the noise power spectrum.