We perform a thorough analysis of the $\eta -{\eta }^{\prime }$ mixing effects on the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\eta }^{{(}^{\prime })}$ decays based on the perturbative QCD (PQCD) factorization approach. Branching ratios, up-down asymmetries, and direct $CP$ asymmetries are computed by considering four popular mixing schemes, such as $\eta -{\eta }^{\prime }$, $\eta -{\eta }^{\prime }-{\eta }_c$, $\eta -{\eta }^{\prime }-G$, and $\eta -{\eta }^{\prime }-G-{\eta }_c$ mixing formalisms, where $G$ represents the physical pseudoscalar glueball. The PQCD predictions with the four mixing schemes does not change much for the $\eta$ channel but changes significantly for the ${\eta }^{\prime }$ one. In particular, the value of $\mathcal{B}({\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\eta }^{\prime })$ in the $\eta -{\eta }^{\prime }-G-{\eta }_c$ mixing scheme exceeds the present experimental bound by a factor of 2, indicating the related mixing angles may be overestimated. Because of the distinctive patterns of interference between $S$-wave and $P$-wave amplitudes, the predicted up-down asymmetries for the two modes differ significantly. The obvious discrepancies among different theoretical analyses should be clarified in the future. The direct $CP$ violations are predicted to be at the level of a few percent mainly because the tree contributions of the strange and nonstrange amplitudes suffer from the color suppression and CKM suppression. Finally, as a by-product, we investigate the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\eta }_c$ process, which has a large branching ratio of order ${10}^{-4}$, promising to be measured by the LHCb experiment. Our findings are useful for constraining the mixing parameters, comprehending the ${\eta }^{{(}^{\prime })}$ configurations, and instructing experimental measurements.

We present localized “particlelike” states composed of a pair of neutral fermions interacting with a scalar Higgs field and the metric of spacetime, extending the Einstein-Dirac formalism introduced by Finster et al. [Particlelike solutions of the Einstein-Dirac equations, Phys. Rev. D 59, 104020 (1999)]. We demonstrate that, when the coupling between the fermions and the Higgs field is strong, there is a class of states in which the total (ADM) mass no longer increases proportionally to the mass of the constituent fermions; indeed it decreases. This phenomenon enables fermionic particles with much larger masses than in the Higgs-free case to form localized states.

We investigate quantum field theories in two dimensions (2D) with an underlying Bondi–van der Burgh–Metzner-Sachs symmetry augmented by $\mathfrak{u}(1)$ currents. These field theories are expected to holographically capture features of charged versions of cosmological solutions in asymptotically flat 3D spacetimes called flat space cosmologies. We conduct a study of the modular properties of these field theories. The characters for the highest weight representations of the symmetry algebra are constructed, and the partition function of the theory is obtained from them. We derive the density of (primary) states and find the entropy and asymptotic values of the structure constants exploiting the modular properties of the partition function and the torus one-point function. The expression for the asymptotic structure constants shows shifts in the weights and one of the central terms and an extra phase compared to the earlier results in the literature for Bondi–van der Burgh–Metzner-Sachs invariant theories without $\mathfrak{u}(1)$ currents present. We reproduce our field results for the structure constants by a bulk computation involving a scalar probe in the background of a charged flat space cosmology.

We study Wilson loops in holographic duals of the $\mathcal{N}=4$ SYM quark-gluon plasma. For this we consider the Schwarzschild-${\mathrm{AdS}}_5$ and Kerr-${\mathrm{AdS}}_5$ black holes, which are dual to the nonrotating and rotating quark-gluon plasmas, correspondingly. From temporal Wilson loops we find the heavy quark potentials in both backgrounds. For the temperature above the critical one we observe the Coulomb-like behavior of the potentials. We find that increasing the rotation the interquark distance decreases, we also see that the increase of the temperature yields the similar behavior. Moreover, at high temperatures values of the potentials in Kerr-${\mathrm{AdS}}_5$ are close to that one calculated in the Schwarzschild-${\mathrm{AdS}}_5$ black hole. We also explore holographic lightlike Wilson loops from which the jet-quenching parameters of a fast parton propagating in the QGP are extracted. We find that the rotation increases the value of the jet-quenching parameter. However, at high temperatures the jet-quenching parameters have a cubic dependence on the temperature as for the AdS black brane.

We consider resolved imaging of faint sources with the solar gravitational lens (SGL) while treating the Sun as an extended gravitating body. We use our new diffraction integral that describes how a spherical electromagnetic wave is modified by the static gravitational field of an extended body, represented by series of multipole moments characterizing its interior mass distribution. Dominated by the solar quadrupole moment, these deviations from spherical symmetry significantly perturb the image that is projected by the Sun into its focal region, especially at solar equatorial latitudes. To study the optical properties of the quadrupole SGL, we develop an approximate solution for the point spread function of such an extended lens. We also derive semianalytical expressions to estimate signal levels from extended targets. With these tools, we study the impact of solar oblateness on imaging with the SGL. Given the small value of the solar quadrupole moment, the majority of the signal photons arriving from an extended target still appear within the image area projected by the monopole lens. However, these photons are scrambled, thus reducing the achievable signal-to-noise ratio during the image recovery process (i.e., deconvolution). We also evaluate the spectral sensitivity for high-resolution remote sensing of exoplanets with the extended SGL. We assess the impact on image quality and demonstrate that despite the adverse effects of the quadrupole moment, the SGL remains uniquely capable of delivering high-resolution imaging and spectroscopy of faint, small, and distant targets, notably terrestrial exoplanets within $\sim 30–100\mathrm{parsec}$ from us.

We obtain charged spherically symmetric black holes in the two-component scalar Einstein-Maxwell-Friedberg-Lee-Sirlin model with a symmetry breaking potential. These asymptotically flat black holes carry resonant scalar Q-hair. As expected, these hairy black holes give rise to nonuniqueness. When comparing these solutions with the corresponding charged boson stars and Reissner-Nordström black holes, we find a different pattern in the case of a massive real scalar component and a massless one. We demonstrate that, as the real component becomes massless, the resonant hairy black holes bifurcate from Reissner-Nordström black holes for sufficiently small gravitational coupling.

In this paper, we show that similar open-source codes for general relativistic (magneto)hydrodynamic [GR(M)HD] produce different results for key features of binary neutron star mergers. First, we present a new open-source version of the publicly available illinoisgrmhd code that provides support for realistic, finite temperature equations of state. After stringent tests of our upgraded code, we perform a code comparison between grhydro, illinoisgrmhd, spritz, and whiskythc, which implement the same physics, but slightly different computational methods. The benefit of the comparison is that all codes are embedded in the einstein toolkit suite, hence their only difference is algorithmic. We find similar convergence properties, fluid dynamics, and gravitational waves, but different merger times, remnant lifetimes, and gravitational wave phases. Such differences must be resolved before the postmerger dynamics modeled with such simulations can be reliably used to infer the properties of nuclear matter especially in the era of precision gravitational wave astronomy.

We study the existence and stability of $Q$-balls in noncanonical scalar field theories, $K(|\mathrm{\Phi }{|}^2,X)$, where $\mathrm{\Phi }$ is the complex scalar field and $X$ is the kinetic term. We extend the Vakhitov-Kolokolov stability criterion to $K$-field theories. We derive the condition for the perturbations to have a well-posed Cauchy problem. We find that $K_{,X}>0$ and $K_{,X}+X{K}_{,XX}>0$ are necessary but not sufficient conditions. The perturbations define a strongly hyperbolic system if $(K_{,X}-2{\varphi }^{\prime 2}{K}_{,XX})(K_{,X}+2{\omega }^2{\varphi }^2{K}_{,XX})>0$. For all modifications studied, we found that perturbations propagate at a speed different from light. Generically, the noncanonical scalar field can lower the charge and energy of the $Q$-ball and therefore improves its stability.

Thermal evolution of neutron stars is studied in the $f(R)=R+\alpha R^2$ theory of gravity. We first review the equations of stellar structure and evolution for a spherically symmetric spacetime plus a perfect fluid at rest. We then present numerical results for the structure of neutron stars using four nucleonic dense matter equations of state and a series of gravity theories for $\alpha$ ranging from zero, i.e., general relativity, up to $\alpha \approx {10}^{16}{\mathrm{cm}}^2$. We emphasize properties of these neutron star models that are of relevance for their thermal evolution as the threshold masses for enhanced neutrino emission by the direct Urca process, the proper volume of the stellar cores where this neutrino emission is allowed, the crust thickness, and the surface gravitational acceleration that directly impact the observable effective temperature. Finally, we numerically solve the equations of thermal evolution and explicitly analyze the effects of altering gravity. We find that uncertainties in the dense matter microphysics, such as the core chemical composition and superfluidity/superconductivity properties, as well as the astrophysical uncertainties on the chemical composition of the surface layers, have a much stronger impact than possible modifications of gravity within the studied family of $f(R)$ theories. We conclude that within this family of gravity theories, conclusions from previous studies of neutron star thermal evolution are not significantly altered by modification of gravity theory. Conversely, this implies that neutron star cooling modeling may not be a useful tool to constrain deviations of gravity from Einstein theory unless these are much more radical than in the $f(R)=R+\alpha R^2$ framework.

The Advanced LIGO/Virgo interferometers have observed $\sim 100$ gravitational-wave transients enabling new questions to be answered about relativity, astrophysics, and cosmology. However, many of our current procedures for computing these constraints will not scale well with the increased size of future transient catalogs. We introduce a novel hybrid sampling method in order to more efficiently perform parameterized tests of general relativity with gravitational-wave signals. Applying our method to the binary black hole merger GW150914 and simulated signals we find that our method is approximately an order of magnitude more efficient than the current method with conservative settings for our hybrid analysis. While we have focused on the specific problem of measuring potential deviations from relativity, our method is of much wider applicability to any problem that can be decomposed into a simple and more complex model(s).

We consider two models which couple derivatives of the inflaton to ordinary matter, both to fermions and to scalars. Such couplings induce changes to the inflaton kinetic energy, analogous to the cosmological Coleman-Weinberg potentials which come from nonderivative couplings. Our purpose is to investigate whether these quantum-induced $k$-essence models can provide efficient reheating without affecting the observational constraints on primordial inflation. Our numerical studies show that it is difficult to preserve both properties.

Large-scale primordial magnetic fields (PMFs) threading the intergalactic medium are observed ubiquitously in the Universe playing a key role in the cosmic evolution. Their origin is still debated constituting a very active field of research. In the present article, we propose a novel natural ab initio mechanism for the origin of such PMFs through the portal of supermassive primordial black holes (PBHs) forming between the big bang nucleosynthesis and the recombination era. In particular, by considering PBHs furnished with a locally isothermal disk we study the generation of a Biermann battery induced seed magnetic field (MF) due to the vortexlike motion of the primordial plasma around the black hole. Finally, by considering monochromatic PBH mass distributions and deriving the relevant MF power spectrum we make a conservative estimate for the seed PMF in intergalactic scales and at redshift $z=30$, when typical galaxies are considered to form, which reads as $B\simeq {10}^{-30}\mathrm{G}{(\frac{{\ell }_{\mathrm{R}}}{{10}^6})}^2{(\frac{M_{\mathrm{PBH}}}{{10}^{14}{M}_{\odot }})}^{5/2}$, where $M_{\mathrm{PBH}}$ is the PBH mass and ${\ell }_{\mathrm{R}}\equiv R_{\mathrm{d}}/R_{\mathrm{ISCO}}$, is the ratio of the radius of the disk, $R_{\mathrm{d}}$ over the radius of the innermost stable circular orbit, $R_{\mathrm{ISCO}}$. Interestingly enough, by requiring to seed a PMF of the order of ${10}^{-30}\mathrm{G}$ necessary to give rise to a present day ${10}^{-18}\mathrm{G}$ in intergalactic scales, we find a lower bound on the PBH mass within the range $[{10}^{10}–{10}^{16}]M_{\odot }$ depending on the radius of the PBH disk.

We explore observational constraints on a cosmological model with an interaction between dark energy (DE) and dark matter (DM), using a compilation of 15 measurements of the 2D baryon acoustic oscillation (BAO) (i.e., transversal) scale in combination with Planck-CMB data, to explore the parametric space of a class of interacting DE (IDE) models. We find that 2D BAO measurements can generate different observational constraints compared to the traditional approach of studying the matter clustering in the 3D BAO measurements. Contrary to the observations for the $\mathrm{\Lambda }\mathrm{CDM}$ and IDE models when analyzed with $\mathrm{Planck}\text{−}\mathrm{CMB}+3\mathrm{D}$ BAO data, we note that $\mathrm{Planck}\text{−}\mathrm{CMB}+2\mathrm{D}$ BAO data favor high values of the Hubble constant $H_0$. From the joint analysis with $\mathrm{Planck}\text{−}\mathrm{CMB}+2\mathrm{D}$ $\mathrm{BAO}+\text{Gaussian}$ prior on $H_0$, we find $H_0=73.4\pm 0.88\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. We conclude that the $H_0$ tension is solved in the IDE model with strong statistical evidence (more than $3\sigma$) for the IDE cosmologies.

Ultrahigh-energy cosmic rays are almost exclusively detected through extensive air showers, which they initiate upon interaction with the atmosphere. The longitudinal development of these air showers can be directly observed using fluorescence detector telescopes, such as those employed at the Pierre Auger Observatory or the Telescope Array. In this article, we discuss the properties of the Greisen function, which was initially derived as an approximate solution to the electromagnetic cascade equations, and its ability to describe the longitudinal shower profiles. We demonstrate that the Greisen function can be used to describe longitudinal air-shower profiles, even for hadronic air showers. Furthermore, we discuss the possibility to discriminate between hadrons and photons from the shape of air-shower profiles using the Greisen function.

We propose a way to constrain the primordial black hole (PBH) abundance in the range of PBH masses $m$ around ${10}^{20}\mathrm{g}$ based on their capture by Sun-like stars in dwarf galaxies, with subsequent star destruction. We calculate numerically the probability of a PBH capture by a star at the time of its formation in an environment typical of dwarf galaxies. Requiring that no more than a fraction $\xi$ of stars in a dwarf galaxy is destroyed by PBHs translates into an upper limit on the PBH abundance. For the parameters of Triangulum II and $\xi =0.5$, we find that no more than $\sim 35\%$ of dark matter can consist of PBHs in the mass range ${10}^{18}–(\text{a few})\times {10}^{21}\mathrm{g}$. The constraints depend strongly on the parameter $\xi$ and may significantly improve if smaller values of $\xi$ are established from observations. An accurate determination of $\xi$ from dwarf galaxy modeling is thus of major importance.

Neutron stars can accumulate asymmetric dark matter (ADM) in their interiors, which affects the neutron star’s measurable properties and makes compact objects prime targets to search for ADM. In this work, we use Bayesian inference to explore potential neutron star mass-radius measurements, from current and future x-ray telescopes, to constrain the bosonic ADM parameters for the case where bosonic ADM has accumulated in the neutron star interior. We find that the current uncertainties in the baryonic equation of state do not allow for constraints on the ADM parameter space to be made. However, we also find that ADM cannot be excluded and the inclusion of bosonic ADM in neutron star cores relaxes the constraints on the baryonic equation of state space. If the baryonic equation of state were more tightly constrained independent of ADM, we find that statements about the ADM parameter space could be made. In particular, we find that the high bosonic ADM particle mass ($m_{\chi }$) and low effective self-interaction strength $(g_{\chi }/m_{\varphi })$ regime is disfavored due to the observationally and theoretically motivated constraint that neutron stars must have at least a mass of $1M_{\odot }$. However, within the remaining parameter space, $m_{\chi }$ and $g_{\chi }/m_{\varphi }$ are individually unconstrained. On the other hand, the ADM mass-fraction, i.e., the fraction of ADM mass inside the neutron star, can be constrained by such neutron star measurements.

Starting from the modified Maxwell equations in Carroll-Field-Jackiw electrodynamics we study the electromagnetic radiation in chiral matter characterized by an axion coupling $\theta (x)=b_{\mu }{x}^{\mu }$, with $b_{\mu }=(0,\mathbf{b})$, which gives rise to the magnetoelectric effect. Employing the stationary phase approximation we construct the Green’s matrix in the radiation zone which allows the calculation of the corresponding electromagnetic potentials and fields for arbitrary sources. We obtain a general expression for the angular distribution of the radiated energy per unit frequency. As an application we consider a charge moving at constant velocity parallel to $\mathbf{b}$ in the medium and discuss the resulting Cherenkov radiation. We recover the vacuum Cherenkov radiation. For the case of a material with refraction index $n>1$ we find that zero, one or two Cherenkov cones can appear. The spectral distribution of the radiation together with the comparison of the radiation output of each cone are presented, as well as some angular plots showing the appearance of the cones.

The emergence of domain walls is a well-known problem in Majoron models for neutrino mass generation. Here, we present extensions of the Majoron model by right-handed doublets and triplets that prevent domain walls from arising. These extensions are highly interesting in the context of leptogenesis, as they impact the conversion of a lepton asymmetry to a baryon asymmetry by sphaleron processes.

We study the effects of a static and uniform magnetic field on the evolution of energy density fluctuations present in a medium. By numerically solving the relativistic Boltzmann-Vlasov equation within the relaxation time approximation, we explicitly show that magnetic fields can affect the characteristics of energy density fluctuations at the timescale the system achieves local thermodynamic equilibrium. A detailed momentum mode analysis of fluctuations reveals that a magnetic field increases the damping of mode oscillations, especially for the low momentum modes. This leads to a reduction in the ultraviolet (high momentum) cutoff of fluctuations and also slows down the dissipation of relatively low momentum fluctuation modes. We discuss the phenomenological implications of our study on various sources of fluctuations in relativistic heavy-ion collisions.

We study corrections to observables related to the muon in the context of models of new physics which generate mass-enhanced corrections to the muon dipole moments. Working in the Standard Model effective theory, we demonstrate a correlation between the decay of the Higgs boson to muons and the magnetic and electric dipole moments of the muon generated by the dominant matching corrections. This defines a novel way to classify predictions for a wide variety of models of new physics based on the pattern of deviations of these three observables. In particular, when applied to specific models, we find that this correlation has a potential to rule out whole models or set upper bounds on the scale of new physics motivated by the muon anomalous magnetic moment.