We show that primordial black holes can be produced from the collapse of large isocurvature perturbations of the cold dark matter. We develop a novel procedure to compute the resulting black hole abundance by studying matched perturbations of matter-only universes, and we use our procedure to translate observational constraints on black hole abundances into model-independent constraints on cold dark matter isocurvature perturbations over a wide range of scales. The constraint on the typical amplitude of the primordial perturbations weakens slightly slower than linearly on small scales.

In the fuzzy dark matter (FDM) model, dark matter is composed of ultralight particles with a de Broglie wavelength of $\sim \mathrm{kpc}$, above which it behaves like cold dark matter. Due to this, FDM suppresses the growth of structure on small scales, which delays the onset of the cosmic dawn and the subsequent epoch of reionization. This leaves potential signatures in the sky averaged 21-cm signal (global), as well as in the 21-cm fluctuations, which can be sought for with ongoing and future 21-cm global and intensity mapping experiments. To do so reliably, it is crucial to include effects such as the dark-matter/baryon relative velocity and Lyman-Werner star-formation feedback, which also act as delaying mechanisms, as well as cosmic microwave background and Lyman-$\alpha$ heating effects, which can significantly change the amplitude and timing of the signal, depending on the strength of x-ray heating sourced by the remnants of the first stars. Here we model the 21-cm signal in FDM cosmologies across cosmic dawn and epoch of reionization using a modified version of the public code 21cmvfast that accounts for all these additional effects, and is directly interfaced with the Boltzmann code class so that degeneracies between cosmological and astrophysical parameters can be fully explored. We examine the prospects to distinguish between the cold dark matter and FDM models and forecast joint astrophysical, cosmological and FDM parameter constraints achievable with intensity mapping experiments such as HERA and global signal experiments like EDGES. We demonstrate that HERA will be sensitive to FDM particle masses, most optimistically up to $m_{\mathrm{FDM}}\sim {10}^{-19}\mathrm{eV}–{10}^{-18}\mathrm{eV}$, depending on foreground assumptions and limited in practice by uncertainty in the astrophysical parameter values, despite the mitigating effect of the delaying and heating mechanisms included in the analysis.

Primordial black holes are a possible component of dark matter and a most promising way of investigating them is through the product of their Hawking evaporation. As a result of this process, any species lighter than the Hawking temperature is emitted, including possible new particles beyond the Standard Model. These can then be detected in laboratory-based experiments via their interaction with the Standard Model particles. In a previous work, we have first proposed and studied this scenario in the presence of an interaction between the light new species and nucleons. Here we extend this discussion to include the case of interaction with electrons. We show that the simultaneous presence of primordial black holes and species lighter than about 100 MeV can be constrained by the measurements of direct detection experiments, such as XENON1T, and water Cherenkov neutrino detectors, such as Super-Kamiokande. Our results provide a complementary and alternative way of investigation with respect to cosmological and collider searches.

We present an analytic study of the dispersion relation for an isotropic magnetized plasma interacting with axions. We provide a quantitative picture of the electromagnetic plasma oscillations in both the ultrarelativistic and nonrelativistic regimes and considering both nondegenerate and degenerate media, accounting for the dispersion curves as a function of the plasma temperature and the ratio of the plasma phase velocity to the characteristic velocity of particles. We include the modifications on the Landau damping of plasma waves induced by the presence of the axion field, and we comment on the effects of damping on subluminal plasma oscillations.

A gauged U(1) extension of the Standard Model (SM) is a simple and anomaly-free framework where three generations of Majorana type right-handed neutrinos (RHNs) are introduced to generate light neutrino mass and flavor mixings through the seesaw mechanism. We investigate such models at different hadron and lepton colliders via $Z^{\prime }$ induced Majorana type RHNs pair production. We derive bounds on U(1) gauge coupling $(g^{\prime })$ comparing the model cross sections with experimentally observed data for different $Z^{\prime }$ mass $(M_{Z^{\prime }})$ and RHNs mass $(M_N)$. Using these limits we estimate the allowed RHN pair production cross section which can be manifested by lepton number violating signatures in association with fat-jets at the hadron colliders depending on the mass of the RHNs. Hence we study dilepton and trilepton modes with fat-jet/s of the signal for different benchmark values of $M_{Z^{\prime }}$ and $M_N$. Using fat-jet signatures and studying the signal and corresponding SM backgrounds, we estimate bounds on $M_N\text{−}{M}_{Z^{\prime }}$ plane at different center of mass energies which could be probed at different hadron colliders. In the context of the lepton colliders we consider electron positron initial states where Majorana type RHNs can be produced from $Z^{\prime }$ manifesting same sign dilepton plus jets signature and trilepton plus jets in association with missing energy. Studying the signal and corresponding SM backgrounds we estimate the bounds on the $M_N\text{−}{M}_{Z^{\prime }}$ plane for different center of mass energies. In the context of the U(1) extension of the SM there is a SM singlet BSM scalar which couples with the RHNs. We can probe the Majorana nature of RHNs via this BSM scalar production at electron positron colliders.

The QCD axion is a promising candidate of the dark matter. In this paper, we discuss elastic scattering processes between nucleons and the QCD axion dark matter. We point out that the cross section can be enhanced by more than $\mathcal{O}({10}^{25})$ by the coherent effect, compared to classical processes. As a result, for example, we show that QCD axions may scatter at the sun with $\mathcal{O}(1)$ probability for $f_a\lesssim {10}^{11}\mathrm{GeV}$. In addition, one may expect stimulated emission effects can also enhance the cross section because the number density of the axion DM is very large. The enhancement factor can be as large as another $\mathcal{O}({10}^{25})$ and, if the factor exists, the force from the dark matter wind may be detected via, e.g., torsion balance experiments. However, it is also found that there is a cancellation of the stimulated emission factor and the force is too small to be detected.

Inspired by the LHCb’s discovery of hidden-charm pentaquarks, the anticharmed strange pentaquarks $P_{\overline{c}s}$ in a favor of the hadronic molecule picture are investigated from the one-boson-exchange model. Similar to the hidden-charm pentaquarks, three molecular bound states, one with spin parity $J^P=1/2^{-}$ below the $\overline{D}\mathrm{\Sigma }$ threshold and another two with $J^P=\{1/2^{-},3/2^{-}\}$ below the ${\overline{D}}^{*}\mathrm{\Sigma }$ threshold, are predicted at 3–3.2 GeV mass region. The mass ordering of the later two states can be interchanged by different reductions of the $\delta (\mathit{r})$ term. Furthermore, resonances associated with these three bound states are examined by considering $D_s^{-}N-\overline{D}\mathrm{\Lambda }-\overline{D}\mathrm{\Sigma }-{\overline{D}}^{*}\mathrm{\Lambda }-{\overline{D}}^{*}\mathrm{\Sigma }$ coupled-channel dynamics, and decay widths of them are predicted. Our study indicates that the $D_s^{-}p$ invariant mass spectrum in the ${\overline{B}}_s^0\to \overline{n}{D}_s^{-}p$ decay is an appropriate place to detect the $P_{\overline{c}s}$ pentaquarks.

We develop the analysis of diphoton exclusive photoproduction in the kinematics where a collinear QCD factorization framework applies, namely nearly forward large invariant mass diphoton production. We work at the leading twist level and at the next-to-leading order (NLO) in the strong coupling constant ${\alpha }_S$. We compare our predictions for cross sections with Born order calculations for the experimental conditions accessible to JLab experiments and show the interesting sensitivity of our results to various models of generalized parton distributions (GPDs). The NLO corrections are rather large and negative but do not prevent the studied reaction from being a promising tool for the extraction of $C$–odd GPDs, which do not contribute to either spacelike or timelike deeply virtual Compton scattering amplitudes.

We systematically investigate the speed of sound in QCD matter under different conditions in the grand canonical ensemble within the Polyakov loop improved Nambu–Jona-Lasinio (PNJL) model. The numerical results indicate that the dependence of speed of sound on parameters like temperature and chemical potential can be indicative of QCD phase transition. Some new features of speed of sound are discovered, for instance, the hierarchy of sound velocity for $u(d)$ and $s$ quark at low temperature with the increasing chemical potential and the squared sound velocity approaching to almost zero in the critical region. We also formulate the relations between differently defined sound velocity using the fundamental thermodynamic relations. Some conclusions derived are useful for hydrodynamics simulation and calculation of transport coefficient of bulk viscosity.

We present a new calculation of $W^{+}{W}^{-}$ production in the semiexclusive channel, that is either with intact outgoing protons or rapidity gaps present in the final state, and with no color flow between the colliding protons. This study provides the first complete prediction of the $W^{+}{W}^{-}$ semiexclusive cross section, as well as the breakdown between elastic and proton dissociative channels. It combines the structure function calculation for a precise modeling of the region of low momentum transfers with a parton-level calculation in the region of high momentum transfers; in the latter case the impact of additional diagrams that are not purely photon–initiated has been appropriately evaluated for the first time. The survival factor probability of no additional proton-proton interactions has for the first time been fully accounted for, including its kinematic and process dependence. We analyze in detail the role that the pure photon-initiated ($\gamma \gamma \to W^{+}{W}^{-}$) subprocess plays, a comparison that is only viable by working in the electroweak axial gauge. In this way, we find that the dominance of this is not complete in the proton dissociative cases, although once $Z$–initiated production is included a significantly better matching to the complete calculation is achieved. A direct consequence of this is that the relative elastic, single and double dissociative fractions are in general different in comparison to the case of lepton pair production. We present a direct comparison to the recent ATLAS data on semiexclusive $W^{+}{W}^{-}$ production, finding excellent agreement within uncertainties. Our calculation is provided in the publicly available superchic 4.1 Monte Carlo (MC) generator, and can be passed to a general purpose MC for showering and hadronization of the final state.

The feasibility of observing true tauonium, the bound state of two tau leptons, ${\mathcal{T}}_0\equiv ({\tau }^{+}{\tau }^{-}{)}_0$, via photon-photon collisions at $e^{+}{e}^{-}$ colliders and at the LHC, is studied. The production cross sections of the process $\gamma \gamma \to {\mathcal{T}}_0\to \gamma \gamma$—as well as those of all relevant backgrounds: spin-0 and 2 charmonium resonances decaying to diphotons, and light-by-light scattering—are computed in the equivalent photon approximation for $e^{+}{e}^{-}$ collisions at BES III ($\sqrt{s}=3.8\mathrm{GeV}$), Belle II ($\sqrt{s}=10.6\mathrm{GeV}$), and FCC-ee ($\sqrt{s}=91.2\mathrm{GeV}$), as well as for ultraperipheral p-p, p-Pb, and Pb-Pb collisions at the LHC. Despite small ${\mathcal{T}}_0$ production cross sections and a final state swamped by decays from overlapping pseudoscalar and tensor charmonium states—the ${\chi }_{\mathrm{c}2}$, ${\eta }_{\mathrm{c}}(2\mathrm{S})$, and ${\chi }_{\mathrm{c}0}$ states have masses only 2.5, 84, and 139 MeV away, respectively, from the ${\mathcal{T}}_0$ peak—evidence and observation of the ground state of the heaviest leptonium appears feasible at Belle II and FCC-ee, respectively, with in-situ high-precision measurements of the irreducible backgrounds.

We report measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for inclusive jet and dijet production in polarized proton-proton collisions at midrapidity and center-of-mass energy $\sqrt{s}=510\mathrm{GeV}$, using the high luminosity data sample collected by the STAR experiment in 2013. These measurements complement and improve the precision of previous STAR measurements at the same center-of-mass energy that probe the polarized gluon distribution function at partonic momentum fraction $0.015\lesssim x\lesssim 0.25$. The dijet asymmetries are separated into four jet-pair topologies, which provide further constraints on the $x$ dependence of the polarized gluon distribution function. These measurements are in agreement with previous STAR measurements and with predictions from current next-to-leading-order global analyses. They provide more precise data at low dijet invariant mass that will better constrain the shape of the polarized gluon distribution function of the proton.

Supposing only that there is an effective charge which defines an evolution scheme for parton distribution functions (DFs) that is all-orders exact, strict lower and upper bounds on all Mellin moments of the valence-quark DFs of pionlike systems are derived. Exploiting contemporary results from numerical simulations of lattice-regularized quantum chromodynamics (QCD) that are consistent with these bounds, parameter-free predictions for pion valence, glue, and sea DFs are obtained. The form of the valence-quark DF at large values of the light-front momentum fraction is consistent with predictions derived using the QCD-prescribed behavior of the pion wave function.

We study numerically the first order radiative corrections to the self-energy, in covariant loop quantum gravity. We employ the recently developed sl2cfoam-next spinfoam amplitudes library and some original numerical methods. We analyze the scaling of the divergence with the infrared cutoff, for which previous analytical estimates provided widely different lower and upper bounds. Our findings suggest that the divergence is approximately linear in the cutoff. We also investigate the role of the Barbero-Immirzi parameter in the asymptotic behavior, the dependence of the scaling on some boundary data, and the expectation values of boundary operators.

We consider a real Klein-Gordon field in the Poincaré patch of ($d+1$)-dimensional anti–de Sitter spacetime, ${\mathrm{PAdS}}_{d+1}$, and impose a dynamical boundary condition on the asymptotic boundary of ${\mathrm{PAdS}}_{d+1}$ that depends explicitly on the second time derivative of the field at the boundary. This boundary condition is of generalized Wentzell type. We construct the Wightman two-point function for the ground state of the Klein-Gordon theory whenever the parameters of the theory (the field mass, curvature coupling, and boundary condition parameters) render such a ground state admissible. In the cases in which the mass of the Klein-Gordon field and the curvature coupling term yield an effectively massless theory, we can define a boundary field whose dynamics are ruled by the dynamical boundary condition and construct, in addition to the Wightman function for the Klein-Gordon field, boundary-to-boundary, boundary-to-bulk, and bulk-to-boundary propagators.

We study the influence of the relativistic redshift on Hong-Ou-Mandel (HOM) interference and present a genuine quantum test of general relativity. We use Glauber’s theory of quantum coherence to predict the coincidence probability of realistic broadband photons in HOM experiments in a nonrelativistic setting. We extend the quantum field theoretical framework previously developed to describe the deformation of the spectral profile of single photons in curved spacetimes to a multiphoton framework, which is exact for inertial observers in a flat spacetime and an approximation when observers are located in a curved spacetime. We find that, in case of frequency entangled photons, a mutual redshift between the sender and the receiver can change the coincidence statistics from photon bunching to photon antibunching and vice versa. This implies that the (anti)symmetry of the photonic spectral wave function is an observer dependent notion and that this can be probed via HOM experiments in a relativistic setting.

We study the Vainshtein screening mechanism in Horndeski theories in the presence of a scalar field $\varphi$ nonminimally and kinetically coupled to ordinary matter field. A general interacting Lagrangian describing this coupling is characterized by energy transfer $f_1$ and momentum exchange $f_2$. For a spherically symmetric configurations on top of the cosmological background, we investigate the static perturbations in linear and nonlinear regimes with respect to the scalar field perturbation. In the former regime, the parametrized post-Newtonian parameter generally deviates from unity as long as the matter coupling or $G_{4,\varphi }$ exists. On the other hand, in the latter regime, we show that the nonlinear self-interaction term of scalar field successfully activates the Vainshtein mechanism even in the presence of the couplings $f_1$ and $f_2$. The gravitational potentials recover the Newtonian behavior deep inside the Vainshtein radius. The bounds on coupling terms not to substantially change the Vainshtein radius are also given.

We consider the motion of nonspinning compact objects orbiting around a Kerr black hole with tidal couplings. The tide-induced quadrupole moment modifies both the orbital energy and outgoing fluxes, so that over the inspiral timescale there is an accumulative shift in the orbital and gravitational wave phase. Previous studies on compact object tidal effects have been carried out in the post-Newtonian (PN) and effective-one-body (EOB) formalisms. In this work, within the black-hole perturbation framework, we propose to characterize the tidal influence in the expansion of mass ratios, while higher-order PN corrections are naturally included. For the equatorial and circular orbit, we derive the leading-order frequency dependent tidal phase shift which agrees with the post-Newtonian result at low frequencies but deviates at high frequencies. We also find that such phase shift has weak dependence ($\le 10\%$) on the spin of the primary black hole. Combining this black-hole perturbation waveform with the post-Newtonian waveform, we have developed a theoretical framework towards a frequency-domain hybrid waveform. The comparison with a limited number of numerical relativity waveform shows an almost comparable phase error to the EOB waveform in characterizing the tidal effects, although more systematic tests within the parameter space are needed to faithfully address the accuracy of this waveform model. Further improvement is expected as the next-to-leading order in mass ratio and the higher-PN tidal corrections are included. This hybrid approach is also applicable for generating binary black-hole waveforms.

Quasinormal modes of scalar and electromagnetic field perturbations in Finslerian Reissner-Nordström black holes with a cosmological constant are investigated in this paper. We analyze the fundamental frequencies and dynamical evolution of quasinormal modes using the WKB approximation and finite difference method, respectively. Both approaches show that the periods of oscillation of quasinormal modes increase with higher Finslerian parameter ${\epsilon }^2$ if the multipole quantum number $l\ge 2$. Using the Prony method, we show that the results obtained from the finite difference method are consistent with the results obtained from the WKB approximation. Quasinormal modes of Finslerian black holes possess spectrum splitting, which reflects the fact that the spherical symmetry of the Finslerian black holes is broken. The effects of the Finslerian parameter ${\epsilon }^2$ on the late-time tails of scalar and electromagnetic field perturbations are shown. The late-time tails of the Finslerian Reissner-Nordström black holes possess a power-law falloff. The power-law index has a discontinuous jump, while the Finslerian parameter ${\epsilon }^2$ varies from 0 to nonzero. Such a fact reflects the fact that asymptotic-infinity behaviors of the Finslerian Reissner-Nordström black holes are different from their counterparts in general relativity.

Strong lensing of fast radio bursts (FRBs) has been proposed as a relatively clean probe of primordial black hole (PBH) dark matter. Recently, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) published a first catalog of 536 FRBs, 62 of which are from repeating sources. In light of this new data, we reexamine the prospects to constrain the abundance of PBHs via FRBs. Extending previous forecasts, we calculate a PBH dark matter bound using the intrinsic burst width and a calibrated flux-ratio threshold per FRB. In addition, we take into account the uncertainty in the relation between the FRB dispersion measure and source redshift. We outline an algorithm to detect lensed FRBs and a method to simulate its performance on real data and set a flux-ratio threshold for each event, which we use to infer realistic forecasts. We then attempt to extract a preliminary bound using the publicly available CHIME data. Unfortunately, both instrumental noise and the provided $\sim 1\mathrm{ms}$ time-resolution of the public data hinder this effort. We identify one candidate event where a double burst could be explained via strong lensing by a $\mathcal{O}(10M_{\odot })$-mass PBH, which will require follow-up study at higher time resolution to either confirm or discard. We show that with a few times the size of the first catalog—sampled at the full instrumental time-resolution so that candidates can be efficiently scrutinized—CHIME will be able to find strong evidence for or robustly rule out PBHs with mass above $\sim 10M_{\odot }$ as the dark matter. Finally, we demonstrate that stacking repeating FRBs can improve the constraints, especially for lower masses.