The first measurements from the CIBER experiment of extragalactic background light (EBL) in near-infrared (NIR) band exhibit a higher intensity than those inferred through $\gamma$-ray observations. Recent theoretical-EBL intensities are typically consistent with the very high energy (VHE) $\gamma$-ray observations. Yet, it is possible that the excess NIR radiation is a new component of EBL and not in tension with the TeV spectra of distant blazars, since the hypothetical axionlike particle (ALP) may lead to a reduced opacity of the Universe for VHE $\gamma$-rays. In order to probe whether the excess component arises mainly from EBL, thirteen observed spectra in high energy and VHE ranges from ten distant TeV BL Lac objects are fitted by four theoretical spectra which involve theoretical EBL (Gilmore et al.), Gilmore’s EBL model including photon/ALP coupling, Gilmore’s EBL with CIBER excess and the latter including photon/ALP coupling respectively. We find the goodness of fit for the model with CIBER excess can be improved with a significance of $7.6\sigma$ after including the photon/ALP coupling. Thus, the ALP/photon mixing mechanism can effectively alleviate the tension; However, the Gilmore EBL model, on the whole, is more compatible with the observed spectra compared to those with ALP, although individual blazars such as PKS $1424+240$ and 1ES 1101-232 prefer the ALP-model. Our results suggest that the recent EBL models can solely explain the VHE $\gamma$-ray observations, and assuming the existence of the ALP to alleviate the tension is not required in a statistical sense, thus the excess over the EBL models is less likely to be a new EBL component.

We investigate gravitational UV/IR mixing models that predict a breakdown of low energy effective field theory, from loop-level, nonlocal gravitational corrections to particle processes. We determine how the choice of IR cutoff in these theories alters predictions for lepton magnetic moments. Using Brookhaven E821 muon magnetic moment data, we exclude models of UV/IR mixing with an IR cutoff set by a spherical volume enclosing the experiment. On the other hand, an IR cutoff defined by the simply connected spatial volume containing the trajectories of the muons implies a correction to the muon magnetic moment which may have already been observed.

We show that primordial (nearly) extremal black holes with a wide range of masses from the Planck scale to around ${10}^9\mathrm{g}$ could be cosmologically stable and provide a viable explanation for dark matter, given a dark electromagnetism and a heavy dark electron. Hawking radiation and Schwinger discharge processes are suppressed by near extremality and the heaviness of the dark electron, respectively. The merger events of binary systems with opposite charges generate nonextremal black holes, whose subsequent Hawking evaporation produces transient neutrino and gamma ray signals to be observed at telescopes like IceCube and HAWC. The relationship between the near-extremal black hole and dark electron masses could also shed light on the weak gravity conjecture.

Because of their tiny band gaps Dirac materials promise to improve the sensitivity for dark matter particles in the sub-MeV mass range by many orders of magnitude. We study several candidate materials and calculate the expected rates for dark matter scattering via light and heavy dark photons as well as for dark photon absorption. A particular emphasis is placed on how to distinguish a dark matter signal from background by searching for the characteristic daily modulation of the signal, which arises from the directional sensitivity of anisotropic materials in combination with the rotation of Earth. We revisit and improve previous calculations and propose two new candidate Dirac materials: bis(naphthoquinone)-tetrathiafulvalene (BNQ-TTF) and ${\mathrm{Yb}}_3\mathrm{PbO}$. We perform detailed calculations of the band structures of these materials and of ${\mathrm{ZrTe}}_5$ based on density functional theory and determine the band gap, the Fermi velocities, and the dielectric tensor. We show that in both ${\mathrm{ZrTe}}_5$ and BNQ-TTF the amplitude of the daily modulation can be larger than 10% of the total rate, allowing us to probe the preferred regions of parameter space even in the presence of sizable backgrounds. BNQ-TTF is found to be particularly sensitive to small dark matter masses (below 100 keV for scattering and below 50 meV for absorption), while ${\mathrm{Yb}}_3\mathrm{PbO}$ performs best for heavier particles.

Within the framework of three-channel Ross-Shaw effective range theory, we derive the constraints among different parameters of the theory in the case of a narrow resonance close to the threshold of the third channel, which is relevant for the resonancelike structure $Z_c(3900)$. The usage of these constraint relations, together with the multichannel Lüscher formula in lattice QCD calculations are also discussed and the strategies are outlined.

We calculate the Sivers asymmetry in the photoproduction of almost back-to-back $J/\psi$-jet pair in the process $e{p}^{\uparrow }\to J/\psi +\text{jet}+X$, which will be possible at the future planned Electron-Ion Collider (EIC). We use the framework of a generalized parton model and nonrelativistic QCD for calculating the $J/\psi$ production rate. We include contributions from both color singlet and color octet states in the asymmetry. We obtain sizable Sivers asymmetry that can be promising to determine the gluon Sivers function. We also investigate the effect of transverse momentum dependent evolution on the asymmetry.

We discuss systematic uncertainties in the chemical freeze-out parameters from the ${\chi }^2$ analysis of hadron multiplicity ratios in the heavy-ion collision experiments. The systematics due to the choice of specific hadron ratios are found to lie within the experimental uncertainties. The variations obtained by removing the usual constraints on the conserved charges show similar behavior. The net charge to net baryon ratios in such unconstrained systems are commensurate with the expected value obtained from the protons and neutrons of the colliding nuclei up to the center of mass energies $\sim 40\mathrm{GeV}$. Beyond that the uncertainties in this ratio gradually increases, possibly indicating the reduction in baryon stopping.

LUX-ZEPLIN (LZ) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with weakly interacting massive particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6-tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above $1.4\times {10}^{-48}{\mathrm{cm}}^2$ for a $40\mathrm{GeV}/c^2$ mass WIMP. Additionally, a $5\sigma$ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of $2.3\times {10}^{-43}{\mathrm{cm}}^2$ ($7.1\times {10}^{-42}{\mathrm{cm}}^2$) for a $40\mathrm{GeV}/c^2$ mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020.

We present upper limits on the production of heavy neutral leptons (HNLs) decaying to $\mu \pi$ pairs using data collected with the MicroBooNE liquid-argon time projection chamber (TPC) operating at Fermilab. This search is the first of its kind performed in a liquid-argon TPC. We use data collected in 2017 and 2018 corresponding to an exposure of $2.0\times {10}^{20}$ protons on target from the Fermilab Booster Neutrino Beam, which produces mainly muon neutrinos with an average energy of $\approx 800\mathrm{MeV}$. HNLs with higher mass are expected to have a longer time of flight to the liquid-argon TPC than Standard Model neutrinos. The data are therefore recorded with a dedicated trigger configured to detect HNL decays that occur after the neutrino spill reaches the detector. We set upper limits at the 90% confidence level on the element $|U_{\mu 4}{|}^2$ of the extended PMNS mixing matrix in the range $|U_{\mu 4}{|}^2<(6.6–0.9)\times {10}^{-7}$ for Dirac HNLs and $|U_{\mu 4}{|}^2<(4.7–0.7)\times {10}^{-7}$ for Majorana HNLs, assuming HNL masses between 260 and 385 MeV and $|U_{e4}{|}^2=|U_{\tau 4}{|}^2=0$.

In this paper, we discuss the implications of the recently proposed trans-Planckian Censorship Conjecture (TCC) for holographic cosmology. For models of holographic inflation that are dual to inverse renormalization group (RG) flows, assuming the TCC to be true, we found a bound on the running of the field theory coupling and the corresponding maximum energy scale above which the RG flow should be modified. We also discuss on the trans-Planckian problem in nongeometrical holographic models.

We propose a new class of gravity theories which are characterized by a nontrivial coupling between the gravitational metric and matter mediated by an auxiliary rank-2 tensor. The actions generating the field equations are constructed so that these theories are equivalent to general relativity in a vacuum, and only differ from general relativity theory within a matter distribution. We analyze in detail one of the simplest realizations of these generalized coupling theories. We show that in this case the propagation speed of gravitational radiation in matter is different from its value in vacuum and that this can be used to weakly constrain the (single) additional parameter of the theory. An analysis of the evolution of homogeneous and isotropic spacetimes in the same framework shows that there exist cosmic histories with both an inflationary phase and a dark era characterized by a different expansion rate.

We investigate the generalized cubic covariant Galileon model, a kinetically driven dark energy model within the Horndeski class of theories. The model extends the cubic covariant Galileon by including power laws of the field derivatives in the K-essence and cubic terms which still allow for tracker solutions. We study the shape of the viable parameter space by enforcing stability conditions which include the absence of ghost, gradient and tachyon instabilities and the avoidance of strong coupling at early time. We study here the relevant effects of the modifications induced by the model on some cosmological observables such as the cosmic microwave background (CMB), the lensing potential autocorrelation and the matter power spectrum. For this goal, we perform parameter estimation using data of CMB temperature and polarization, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa) and Cepheids. Data analysis with CMB alone finds that the today’s Hubble parameter $H_0$ is consistent with its determination from Cepheids at $1\sigma$, resolving the famous tension of the cosmological standard models. The joint analysis of CMB, BAO, RSD and SNIa sets a lower bound for the sum of neutrino masses which is $\mathrm{\Sigma }{m}_{\nu }>0.11\mathrm{eV}$ at $1\sigma$, in addition to the usual upper limit. The model selection analysis based on the effective ${\chi }_{\mathrm{eff}}^2$ and deviance information criterion is not able to clearly identify the statistically favored model between $\mathrm{\Lambda }\mathrm{CDM}$ and the generalized cubic covariant Galileon, from which we conclude that the latter model deserves further studies.

Recent work has shown that modified gravitational wave (GW) propagation can be a powerful probe of dark energy and modified gravity, specific to GW observations. We use the technique of Gaussian processes, which allows the reconstruction of a function from the data without assuming any parametrization, to measurements of the GW luminosity distance from simulated joint GW-gamma-ray-burst detections, combined with measurements of the electromagnetic luminosity distance by simulated data from the dark energy survey (DES). For the GW events, we consider both a second-generation LIGO/Virgo/Kagra (HVLKI) network, and a third-generation detector such as the Einstein Telescope. We find that the HVLKI network at target sensitivity, with $O(15)$ neutron star binaries with an electromagnetic counterpart, could already detect deviations from general relativity at a level predicted by some modified gravity models, and a third-generation detector such as the Einstein Telescope would have a remarkable discovery potential. We discuss the complementarity of the Gaussian processes technique to the $({\mathrm{\Xi }}_0,n)$ parametrization of modified GW propagation.

In the peak approach, the formation sites of observable structures in the Universe are identified as peaks in the matter density field. The statistical properties of the clustering of peaks are particularly important in this respect. In this paper, we investigate the large-separation expansion of the correlation function of peaks in Gaussian random fields. The analytic formula up to third order is derived, and the resultant expression can be evaluated by a combination of one-dimensional fast Fourier transforms, which are evaluated very fast. The analytic formula obtained perturbatively in the large-separation limit is compared with a method of Monte Carlo integrations, and a complementarity between the two methods is demonstrated.

We explore whether nonstandard dark sector physics might be required to solve the existing cosmological tensions. The properties we consider in combination are (a) an interaction between the dark matter and dark energy components and (b) a dark energy equation of state $w$ different from that of the canonical cosmological constant $w=-1$. In principle, these two parameters are independent. In practice, to avoid early-time, superhorizon instabilities, their allowed parameter spaces are correlated. Moreover, a clear degeneracy exists between these two parameters in the case of cosmic microwave background (CMB) data. We analyze three classes of extended interacting dark energy models in light of the 2019 Planck CMB results and Cepheid-calibrated local distance ladder $H_0$ measurements of Riess et al. (R19), as well as recent baryon acoustic oscillation (BAO) and type Ia supernovae (SNeIa) distance data. We find that in quintessence coupled dark energy models, where $w>-1$, the evidence for a nonzero coupling between the two dark sectors can surpass the $5\sigma$ significance. Moreover, for both $\mathrm{Planck}+\mathrm{BAO}$ or $\mathrm{Planck}+\mathrm{SNeIa}$, we find a preference for $w>-1$ at about three standard deviations. Quintessence models are, therefore, in excellent agreement with current data when an interaction is considered. On the other hand, in phantom coupled dark energy models, there is no such preference for a nonzero dark sector coupling. All the models we consider significantly raise the value of the Hubble constant, easing the $H_0$ tension. In the interacting scenario, the disagreement between $\mathrm{Planck}+\mathrm{BAO}$ and R19 is considerably reduced from $4.3\sigma$ in the case of the $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model to about $2.5\sigma$. The addition of low-redshift BAO and SNeIa measurements leaves, therefore, some residual tension with R19 but at a level that could be justified by a statistical fluctuation. Bayesian evidence considerations mildly disfavor both the coupled quintessence and phantom models, while mildly favoring a coupled vacuum scenario, even when late-time datasets are considered. We conclude that nonminimal dark energy cosmologies, such as coupled quintessence, phantom, or vacuum models, are still an interesting route toward softening existing cosmological tensions, even when low-redshift datasets and Bayesian evidence considerations are taken into account.

Magnetohydrodynamics (MHD) turbulence is likely to play an important role in several astrophysical scenarios, where the magnetic Reynolds is very large. Numerically, these cases can be studied efficiently by means of large-eddy simulations, in which the computational resources are used to evolve the system only up to a finite grid size. The resolution is not fine enough to capture all the relevant small-scale physics at play, which is instead effectively modeled by a set of additional terms in the evolution equations, dubbed as subgrid-scale model. Here we extend such approach, commonly used in nonrelativistic/nonmagnetic/incompressible fluid dynamics, to any general set of equation written in conservative form. We apply the so-called gradient model, giving recipes for these general balance-law systems, including the relevant case in which a nontrivial inversion of conserved to primitive fields is needed. In particular, we focus on the relativistic compressible ideal MHD scenario, by providing for the first time and for any equation of state, all the additional nontrivial subgrid-scale terms. As an application, we consider box simulations of the relativistic Kelvin-Helmholtz instability, which is also the first mechanism responsible for the magnetic field amplification in binary neutron star mergers and cannot be captured by the finest grid and longest simulations available (currently and in the near future). We numerically assess the performance of our model, by comparing it to the residuals coming from the filtering of high-resolution simulations. We find that the model can fit very well the residuals coming from filtering simulations with a resolution a few times higher. The application shown here explicitly considers the Minkovski metric, but it can be directly extended to general relativity, thus settling the basis to implement for the first time the gradient subgrid model in a general relativistic magnetohydrodynamics (GRMHD) binary merger large-eddy simulations. Our results suggest that this approach will be potentially able to unveil much better the small-scale dynamics achievable of full GRMHD simulations, or equivalently, to obtain the same results but saving a considerable amount of computational time.

We investigate the ability of the Laser Interferometer Space Antenna (LISA) to measure the center of mass acceleration of stellar-origin black hole binaries emitting gravitational waves. Our analysis is based on the idea that the acceleration of the center of mass induces a time variation in the redshift of the gravitational wave, which in turn modifies its waveform. We confirm that while the cosmological acceleration is too small to leave a detectable imprint on the gravitational waveforms observable by LISA, larger peculiar accelerations may be measurable for sufficiently long lived sources. We focus on stellar-mass black hole binaries, which will be detectable at low frequencies by LISA and near coalescence by ground based detectors. These sources may have large peculiar accelerations, for instance, if they form in nuclear star clusters or in active galactic nucleus (AGN) accretion disks. If that is the case, we find that in an astrophysical population calibrated to the LIGO-Virgo observed merger rate, LISA will be able to measure the peculiar acceleration of a small but significant fraction of the events if the mission lifetime is extended beyond the nominal duration of 4 years. In this scenario LISA will be able to assess whether black hole binaries form close to galactic centers, particularly in AGN disks, and will thus help discriminate between different formation mechanisms. Although for a nominal 4-year LISA mission the peculiar acceleration effect cannot be measured, a consistent fraction of events may be biased by strong peculiar accelerations which, if present, may imprint large systematic errors on some waveform parameters. In particular, estimates of the luminosity distance could be strongly biased and consequently induce large systematic errors on LISA measurements of the Hubble constant with stellar-mass black hole binaries.

We predict the masses of the low-lying $B_c$ mesons with $J^P=0^{-},1^{-},0^{+},1^{+},2^{+}$, using a flavor-dependent interaction pattern which gives an unified successful description of the light, heavy-light, and heavy mesons and is also applicable to the radial excited heavy mesons. The errors are controlled carefully. With the errors from the rainbow ladder (RL) approximation subdued, our predictions are consistent with the lattice QCD (lQCD) and quark model results, which support strongly that the flavor-dependent interaction pattern is reasonable. Our predictions provide significant guides to the experiment search of the $B_c$ mesons.

Sub-GeV dark matter (DM) which interacts with electrons can excite electrons occupying molecular orbitals in a scattering event. In particular, aromatic compounds such as benzene or xylene have an electronic excitation energy of a few eV, making them sensitive to DM as light as a few MeV. These compounds are often used as solvents in organic scintillators, where the deexcitation process leads to a photon which propagates until it is absorbed and reemitted by a dilute fluor. The fluor photoemission is not absorbed by the bulk, but is instead detected by a photon detector such as a photomultiplier tube. We develop the formalism for DM–electron scattering in aromatic organic molecules, calculate the expected rate in p-xylene, and apply this calculation to an existing measurement of the single photo-electron emission rate in a low-background EJ-301 scintillator cell. Despite the fact that this measurement was performed in a shallow underground laboratory under minimal overburden, the DM–electron scattering limits extracted from these data are already approaching leading constraints in the 3–100 MeV DM mass range. We discuss possible next steps in the evolution of this direct detection technique, in which scalable organic scintillators are used in solid or liquid crystal phases and in conjunction with semiconductor photodetectors to improve sensitivity through directional signal information and potentially lower dark rates.