We study echoes of free massless scalar from dyonic black holes in Einstein-Maxwell gravity extended with the quasitopological electromagnetic term. These asymptotically flat black holes all satisfy the dominant energy condition. We find that for suitable parameters, the effective potential can have double peaks and consequently echoes of quasinormal modes arise. In general the echo frequency associated with the initial wave packet released inside the two peaks is about twice the frequency of the one released outside.

Quasitopological electromagnetism has an important influence on the strong gravity of dyonic black holes. For example, three photon spheres, with one being stable, are found, and we wish to test them with the observed black hole shadow. We are primarily concerned with the thermodynamics and phase transition for a dyonic anti–de Sitter (AdS) black hole when quasitopological electromagnetism is included. Unlike in a black hole solution without quasitopological electromagnetism, we observe a triple point phase structure by varying the coupling parameters. Of particular interest, for certain parameter values, two separate coexistence curves are present, which is an additional novel phase structure that is absent in a black hole solution without quasitopological electromagnetism. The critical exponents share the same values as mean field theory. These results uncover the intriguing properties of dyonic AdS black holes with quasitopological electromagnetism from a thermodynamic point of view.

We analyze whether a black hole can exist and survive in a universe that goes through a cosmological bounce. To this end, we investigate a central inhomogeneity embedded in a bouncing cosmological background modeled by the comoving generalized McVittie metric. Contrary to other dynamical metrics available in the literature, this solution allows for the interaction of the central object with the cosmological fluid. We show that the horizons associated with this metric change with cosmic time because they are coupled to the cosmic evolution as the mass of the central object is always proportional to the scale factor: it decreases during contraction and increases during expansion phases. After a full analysis of the causal structure of this spacetime, we determine that a dynamical black hole persists during the contraction, bounce, and expansion of the universe. This result implies that there is a class of bouncing models that admits black holes at all cosmological epochs. If these models are a correct approximation to the real universe, then black holes surviving a cosmic collapse could play some role in the subsequent expanding phase.

In this work, we deal with the QED interpretation of the Euler-Heisenberg nonlinear electrodynamics as the effective theory after a one-loop of nonperturbative quantization. It endows the vacuum with an effective dielectric constant, the polarizability and magnetizability of which are determined by clouds of virtual charges surrounding the real currents and charges. Therefore, we study the Euler-Heisenberg nonlinear electrodynamics as a screened Maxwell theory. We generate a rotating electrically charged Einstein-Euler-Heisenberg black hole solution and interpret it as a Kerr-Newman-like one with screened electric charge, as it happens for the static electrically charged black hole Einstein-Euler-Heisenberg solution, which is considered as a Reissner-Nordström-like solution with screened electric charge.

Compton scattering is a key process shaping spectra formation and accretion flow dynamics in accreting strongly magnetized neutron stars. A strong magnetic field affects the scattering cross section and makes it dependent on photon energy, momentum, and polarization state. Using Monte Carlo simulations, we investigate statistical features of Compton scattering of polarized x-ray radiation in a strong magnetic field. Our analysis is focused on photon gas behavior well inside the scattering region. We take into account the resonant scattering at the fundamental cyclotron frequency, thermal distribution of electrons at the ground Landau level, and bulk velocity of the electron gas. We show that (i) the photons scattered around the cyclotron energy by the electron gas at rest tend to acquire the final energy close to the cyclotron one with very small dispersion measure; (ii) the redistribution of photons within the Doppler core of cyclotron resonance differs significantly from the complete redistribution; (iii) the efficiency of momentum transfer from photons to the electron gas is affected by the temperature of electron gas both for photons at cyclotron energy and below it; (iv) the momentum transfer from photons to the electron gas of nonzero bulk velocity is more efficient in the case of magnetic scattering.

Detection of the global 21 cm signal arising from neutral hydrogen can revolutionize our understanding of the standard evolution of the Universe after recombination. In addition, it can also be an excellent probe of dark matter (DM). Among all the DM candidates, primordial black holes (PBHs) are one of the most well motivated. Hawking emission from low-mass PBHs can have a substantial effect on the thermal and ionization history of the early Universe, and that in turn can have an imprint on the global 21 cm signal. Recently EDGES has claimed a global 21 cm signal, though SARAS 3 has rejected that claim. In this work, we investigate the sensitivities on nonspinning and spinning PBHs arising from an EDGES-like measurement of the global 21 cm signal, and find that the sensitivities will be competitive with those arising from other astrophysical observables. We show that the sensitivities can be significantly strengthened depending on various uncertain astrophysical parameters. Besides, we also derive projections on the PBH density from the absorption trough expected during the Dark Ages. Our work shows that the near future unambiguous detection of the global 21 cm absorption troughs can be an excellent probe of PBH DM.

Quasinormal oscillation modes of neutron stars provide a means to probe their interior composition using gravitational wave astronomy. We compute the frequencies and damping times of composition-dependent core $g$-modes of neutron stars containing quark matter employing linearized perturbative equations of general relativity. We find that ignoring background metric perturbations due to the oscillating fluid, as in the Cowling approximation, underestimates the $g$-mode frequency by up to 10% for higher mass stars, depending on the parameters of the nuclear equation of state and how the mixed phase is constructed. The $g$-mode frequencies are well described by a linear scaling with the central lepton (or combined lepton and quark) fraction for nucleonic (hybrid) stars. Our findings suggest that neutron stars with and without quarks are manifestly different with regards to their quasinormal $g$-mode spectrum, and may thus be distinguished from one another in future observations of gravitational waves from merging neutron stars.

Dijet production in proton-nucleus ($p\mathrm{A}$) collisions at the LHC provides invaluable information on the underlying parton distributions in nuclei, especially the gluon distributions. Triple-differential dijet cross sections enable a well-controlled kinematic scan (over momentum fraction $x$ and probing scale $Q^2$) of the nuclear parton distribution functions (nPDFs), i.e., $f_i^{\mathrm{A}}(x,Q^2)$. In this work, we study several types of triple-differential cross sections for dijet production in proton-proton and proton-lead ($p\mathrm{Pb}$) collisions at the LHC, to next-to-leading order within the framework of perturbative quantum chromodynamics (pQCD). Four sets of nPDF parametrizations, EPPS16, nCTEQ15, TUJU19, and nIMParton16 are employed in the calculations for $p\mathrm{Pb}$ collisions. We show that the observable nuclear modification factor $R_{p\mathrm{Pb}}$ of such cross sections can serve as a nice image of the nuclear modifications on parton distributions, quantified by the ratio $r_i^{\mathrm{A}}(x,Q^2)=f_i^{A,\mathrm{proton}}(x,Q^2)/f_i^{\text{proton}}(x,Q^2)$. Considerable differences among the $R_{p\mathrm{Pb}}$ predicted by the four nPDF sets can be observed and intuitively understood. Future measurements of such observables are expected to not only constrain the nPDF parametrizations, but also help confirm various nuclear effects, e.g., shadowing, antishadowing, EMC, and Fermi motion in different regions of $x$ and their variations with probing scale $Q^2$.

If the masses of at least two generations of right-handed neutrinos (RHNs) are near degenerate, the scale of leptogenesis can be as low as $\sim 100\mathrm{GeV}$. In this work, we study probing such resonant leptogenesis in the $B-L$ model at the LHC and future multi-TeV muon colliders via the process $Z^{\prime }\to NN\to {\ell }^{\pm }{\ell }^{\pm }+\text{jets}$, with $Z^{\prime }$ the $U(1{)}_{B-L}$ gauge boson and $N$ the RHN. The same-sign dilepton feature of the signal makes it almost background-free, while the event number difference between positive and negative leptons is a hint for $CP$ violation, which is a key ingredient of leptogenesis. We found that resonant leptogenesis can be tested at the HL-LHC for $M_{Z^{\prime }}$ up to 12 TeV, while at a 10 (30) TeV muon collider the reach can be up to $M_{Z^{\prime }}\sim 30(100)\mathrm{TeV}$ via the off-shell production of $Z^{\prime }$.

Any axionlike particle (ALP) intrinsically possesses flavorful couplings to the standard model (SM) fermions arising as a consequence of the right-handed flavor rotation within the SM. In this paper we discuss this intrinsically flavored ALP, and explore the correlation of a minimal set of the couplings in a view of coherence in flavor physics observables. We focus particularly on the tau-lepton flavor violation (LFV). The ALP is assumed to be tau-philic on a current-eigenstate basis, a la Pecci-Quinn, and is allowed to couple also to muon and electron only in a right-handed specific manner. Several LFV processes are generated including radiative tau decays and also anomalous magnetic moments of electron and muon. We first pay attention to two separated limits: electron scenario with the ALP coupled to tau which mixes only with right-handed electron, and muon scenario as the muonic counterpart of the electron scenario. It turns out that those scenarios are highly constrained by existing experimental limits from the LFV processes and $(g-2)\mathrm{s}$, to require a mu or electron-tau flipped feature in the mass eigenbasis when coupled to the ALP. We then examine a hybrid scenario combining the two separated scenarios, and find a fully viable parameter space on the ALP mass-photon coupling plane, which limits the ALP mass to be around (1.7–10) GeV and the ALP decay constant $f_a$ to be (12.8–67.9) GeV. Discrimination of the present ALP from other light LFV particles are also discussed. We find that the same-sign multilepton signal at Belle II is a smoking-gun to probe the present ALP signal, and the polarization asymmetry in LFV radiative $\tau$ decay is a punchline, which definitely predicts preference of the right-handed polarization, in sharp contrast to the prediction of the SM plus massive Dirac neutrinos having the highly left-handed preference, and also other light-new physics candidates with the same mass scale as the present ALP. Possible model-building to underlie the intrinsically-flavorful third-generation specific ALP is also briefly addressed.

We investigate a simple variant of type-II seesaw, responsible for neutrino mass generation, where the particle spectrum is extended with one singlet right-handed neutrino and an inert Higgs doublet, both odd under an additional $Z_2$ symmetry. While the role of the dark matter is played by the lightest neutral component of the inert Higgs doublet (IHD), its interaction with the Standard Model lepton doublets and the right-handed neutrino turns out to be crucial in generating the correct baryon abundance of the Universe through flavored leptogenesis from the decay of the $SU(2{)}_L$ scalar triplet, involved in type-II framework. We observe a correlation between the smallness of the mass splitting, among the dark matter and the $CP$-odd neutral scalar from the IHD, and the largeness of the mass of the triplet followed from the dominance of the type-II mechanism over the radiative contribution to neutrino mass.

We present new sets of nuclear parton distribution functions (nPDFs) at next-to-leading order and next-to-next-to-leading order in perturbative QCD. Our analyses are based on deeply inelastic scattering data with charged-lepton and neutrino beams on nuclear targets, and experimental data from measurements of $W^{\pm },Z$ boson production in $\mathrm{p}+\mathrm{Pb}$ collisions at the LHC. In addition, a set of proton baseline PDFs is fitted within the same framework and with the same theoretical assumptions. The results of our global QCD analysis are compared to existing nPDF sets and to the previous nPDF set TUJU19, which was based on deep-inelastic scattering data only. Our work is performed using an open-source tool, xFitter, and the required extensions of the code are discussed as well. We find good agreement with the data included in the fit and a lower value for ${\chi }^2/N_{\mathrm{dp}}$ when performing the fit at next-to-next-to-leading order. We apply the resulting nuclear PDFs to electroweak boson production in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the LHC and compare the results to the most recent data from ATLAS and CMS.

Deep neural networks trained for jet tagging are typically specific to a narrow range of transverse momenta or jet masses. Given the large phase space that the LHC is able to probe, the potential benefit of classifiers that are effective over a wide range of masses or transverse momenta is significant. In this work we benchmark the performance of a number of methods for achieving accurate classification at masses distant from those used in training, with a focus on algorithms that leverage metalearning. We study the discrimination of jets from boosted $Z^{\prime }$ bosons against a QCD background. We find that a simple data augmentation strategy that standardizes the angular scale of jets with different masses is sufficient to produce strong generalization. The metalearning algorithms provide only a small improvement in generalization when combined with this augmentation. We also comment on the relationship between mass generalization and mass decorrelation, demonstrating that those models which generalize better than the baseline also sculpt the background to a smaller degree.

The general analysis of the differential cross section and various polarization observables is performed for the process $e^{+}+e^{-}\to N+\overline{N}+{\pi }^0$ assuming that the annihilation occurs through the exchange of one virtual photon. The dependence of the differential distributions over invariant variables is derived for the reaction $e^{+}+e^{-}\to N+\overline{N}+{\pi }^0$ in the so-called nonresonant mechanism, applying the conservation of the hadron electromagnetic currents and the P-invariance of the hadron electromagnetic interaction. The detection in an exclusive experimental setup where the nucleon (or antinucleon) and pion are detected in coincidence is considered. A number of single and double differential distributions have been calculated analytically and numerical estimates are given for the $p\overline{p}{\pi }^0$ and $n\overline{n}{\pi }^0$ channels, in the Born (nonresonant) approximation, in the energy range from threshold up to $s=16{\mathrm{GeV}}^2$.

We study all-charm tetraquarks in the front form of Hamiltonian dynamics using the many-body basis function approach known as basis light-front quantization. The model Hamiltonian contains transverse and longitudinal confining potentials and a one-gluon-exchange effective potential. We calculate masses of two-charm-two-anticharm states focusing on the lowest state. We also calculate two-quark and four-quark estimates of meson-meson breakup threshold. The results suggest that the lowest two-charm-two-anticharm state is not a tightly bound tetraquark. We discuss implications of the cluster decomposition principle for theories formulated on the light front and present our treatment of identical particles together with color-singlet restrictions on the space of quantum states.

We derive the twist-3 gluon fragmentation function (FF) contribution to the transversely polarized hyperon production in semi-inclusive deep inelastic scattering, $ep\to e{\mathrm{\Lambda }}^{\uparrow }X$, in the leading order (LO) with respect to the QCD coupling in the framework of the collinear twist-3 factorization. Together with the known result for the contribution from the twist-3 distribution in the proton and the twist-3 quark FFs for the hyperon, this completes the LO cross section for this process. The constraint relations among the twist-3 FFs are taken into account. The formula is relevant to large-$P_T$ hyperon production in the future electron-ion-collider experiment.

We consider dynamics of the massive minimally coupled scalar field theory in an expanding Friedmann-Lemaître-Robertson-Walker universe. We consider the standard toy model of the conformally flat space-time where the conformal factor becomes constant at the distant past and the distant future. Employing the Schwinger-Keldysh diagrammatic technique, we compute infrared loop corrections to the occupation number and anomalous quantum average of the scalar field and show that these corrections are growing with time. Using these observations, we demonstrate that the regularized stress-energy tensor at the distant future acquires substantial quantum corrections which exceed the long known tree-level contributions to the particle flux.

Tunneling between degenerate vacua is allowed in finite-volume quantum field theory, and it features remarkable energetic properties, which result from the competition of different dominant configurations in the partition function. We derive the one-loop effective potential based on two homogeneous vacua of the bare theory, and we discuss the resulting null energy condition violation in $O(4)$-symmetric Euclidean spacetime, as a result of a nonextensive effective action.

Superradiance has been studied quite extensively in the context of static (charged) and rotating black hole spacetime. In this paper, we report for the first time that for a minimally coupled scalar field, the absorption cross section of a Schwarzschild black hole in its ringdown phase can be superradiant. Treating the scattered scalar field as axion, we further computed its observable effects on the rotation of the plane of polarization of photon, neutron dipole moment, and fermionic spin precession. All those observables turned out to have interesting time dependence induced by the ringing black hole background. Our present result opens up an intriguing possibility of observing the black hole merging phenomena through other fundamental fields.

We present the marginal unbiased score expansion (MUSE) method, an algorithm for generic high-dimensional hierarchical Bayesian inference. MUSE performs approximate marginalization over arbitrary non-Gaussian latent parameter spaces, yielding Gaussianized asymptotically unbiased and near-optimal constraints on global parameters of interest. It is computationally much cheaper than exact alternatives like Hamiltonian Monte Carlo (HMC), excelling on funnel problems which challenge HMC, and does not require any problem-specific user supervision like other approximate methods such as variational inference or many simulation-based inference methods. MUSE makes possible the first joint Bayesian estimation of the delensed Cosmic Microwave Background (CMB) power spectrum and gravitational lensing potential power spectrum, demonstrated here on a simulated data set as large as the upcoming South Pole Telescope 3G $1500{\mathrm{deg}}^2$ survey, corresponding to a latent dimensionality of $\sim 6\mathrm{million}$ and of order 100 global bandpower parameters. On a subset of the problem where an exact but more expensive HMC solution is feasible, we verify that MUSE yields nearly optimal results. We also demonstrate that existing spectrum-based forecasting tools which ignore pixel-masking underestimate predicted error bars by only $\sim 10\%$. This method is a promising path forward for fast lensing and delensing analyses which will be necessary for future CMB experiments such as SPT-3G, Simons Observatory, or CMB-S4, and can complement or supersede existing HMC approaches. The success of MUSE on this challenging problem strengthens its case as a generic procedure for a broad class of high-dimensional inference problems.