We study the absorption of massless scalar waves in a geometry that interpolates between the Schwarzschild solution and a wormhole that belongs to the Morris-Thorne class of solutions. In the middle of the interpolation branch, this geometry describes a regular black hole. We use the partial wave approach to compute the scalar absorption cross section in this geometry. Our results show that black holes and wormholes present distinctive absorption spectra. We conclude, for instance, that the wormhole results are characterized by the existence of quasibound states which generate Breit-Wigner-like resonances in the absorption spectrum.

The Laser Interferometer Space Antenna (LISA) will be able to detect massive black hole mergers throughout the visible Universe. These observations will provide unique information about black hole formation and growth, and the role black holes play in galaxy evolution. Here we develop several key building blocks for detecting and characterizing black hole binary mergers with LISA, including fast heterodyned likelihood evaluations, and efficient stochastic search techniques.

It is well known that in order to make the action well defined, one may employ different kinds of boundary conditions (BCs) accompanied by the appropriate Gibbons-Hawking-York (GHY) terms. In this paper we investigate the role of the selected BC and the corresponding GHY terms on the black hole (BH) entropy. Our result shows, regardless of the kind of BC, the BH entropy in all cases is the same as the one obtained under the Dirichlet BC from the Wald formula or semiclassical approximation method. We consider the Schwarzschild solution for $f(R)$-gravity and general relativity in standard dimensions as special models.

The next generation of ground-based cosmic microwave background (CMB) experiments aim to measure temperature and polarization fluctuations up to ${\ell }_{\max }\approx 5000$ over half of the sky. Combined with Planck data on large scales, this will provide improved constraints on primordial non-Gaussianity. However, the impressive resolution of these experiments will come at a price. Besides signal confusion from galactic foregrounds, extragalactic foregrounds, and late-time gravitational effects, gravitational lensing will introduce large non-Gaussianity that can become the leading contribution to the bispectrum covariance through the connected four-point function. Here, we compute this effect analytically for the first time on the full sky for both temperature and polarization. We compare our analytical results with those obtained directly from map-based simulations of the CMB sky for several levels of instrumental noise. Of the standard shapes considered in the literature, the local shape is most affected, resulting in a 35% increase of the estimator standard deviation for an experiment such as the Simons Observatory (SO) and a 110% increase for a cosmic-variance limited experiment, including both temperature and polarization modes up to ${\ell }_{\max }=3800$. Because of the nature of the lensing four-point function, the impact on other shapes is reduced while still non-negligible for the orthogonal shape. Two possible avenues to reduce the non-Gaussian contribution to the covariance are proposed: First by marginalizing over lensing contributions, such as the Integrated Sachs Wolfe (ISW)-lensing three-point function in temperature, and second by delensing the CMB. We show the latter method can remove almost all extra covariance, reducing the effect to below $<5\%$ for local bispectra. At the same time, delensing would remove signal biases from secondaries induced by lensing, such as ISW lensing. We aim to apply both techniques directly to the forthcoming SO data when searching for primordial non-Gaussianity.

We discuss spectral distortions, time delays, and refraction of light in an axion or axion-plasma background. This involves solving the full set of geodesic equations associated to the system of Hamiltonian optics, allowing us to self-consistently take into account the evolution of the frequency, momentum, and position of photons. We support our arguments with analytic approximations and full numerical solutions. We also describe both nonintegrated and integrated versions of these effects, the latter of which depends on the whole history of the photon trajectory through the axion background. Remarkably, the introduction of a plasma enhances the sensitivity to axion-induced optical phenomena, allowing chiral refraction, integrated time delays, and integrated frequency shifts to occur at first order in the axion-photon coupling. This suggests a general enhancement of many axion-induced dispersive effects when the background refractive index is different from 1.

Observations of neutron stars, whether in binaries or in isolation, provide information about the internal structure of the most extreme material objects in the Universe. In this work, we combine information from recent observations to place joint constraints on the properties of neutron star matter. We use (i) lower limits on the maximum mass of neutron stars obtained through radio observations of heavy pulsars, (ii) constraints on tidal properties inferred through the gravitational waves neutron star binaries emit as they coalesce, and (iii) information about neutron stars’ masses and radii obtained through X-ray emission from surface hot spots. In order to combine information from such distinct messengers while avoiding the kind of modeling systematics intrinsic to parametric inference schemes, we employ a nonparametric representation of the neutron-star equation of state based on Gaussian processes conditioned on nuclear theory models. We find that existing astronomical observations imply $R_{1.4}=12.32_{-1.47}^{+1.09}\mathrm{km}$ for the radius of a $1.4{\mathrm{M}}_{\odot }$ neutron star and $p(2{\rho }_{\mathrm{nuc}})=3.8_{-2.9}^{+2.7}\times 10^{34}\mathrm{dyn}/{\mathrm{cm}}^2$ for the pressure at twice nuclear saturation density at the 90% credible level. The upper bounds are driven by the gravitational wave observations, while X-ray and heavy pulsar observations drive the lower bounds. Additionally, we compute expected constraints from potential future astronomical observations and find that they can jointly determine $R_{1.4}$ to $\mathcal{O}(1)\mathrm{km}$ and $p(2{\rho }_{\mathrm{nuc}})$ to 80% relative uncertainty in the next five years.

We present bounds on mirror dark matter derived by using the effect of mirror matter on the luminosity of the Sun. In the perturbative regime where the mirror matter concentration is small relative to the ordinary matter, we estimate the heat transfer from ordinary matter to the mirror sector by simple analytic consideration. That amount of heat transfer is radiated via mirror photons and increases the required energy production in order to maintain the observed luminosity. We then present more detailed numerical calculations of the total amount of this energy transfer.

We combine hierarchical Bayesian modeling with a flow-based deep generative network, in order to demonstrate that one can efficiently constraint numerical gravitational-wave (GW) population models at a previously intractable complexity. Existing techniques for comparing data to simulation, such as discrete model selection and Gaussian process regression, can only be applied efficiently to moderate-dimension data. This limits the number of observable (e.g., chirp mass, spins.) and hyperparameters (e.g., common envelope efficiency) one can use in a population inference. In this study, we train a network to emulate a phenomenological model with 6 observables and 4 hyper-parameters, use it to infer the properties of a simulated catalogue and compare the results to using a phenomenological model. We find that a 10-layer network can emulate the phenomenological model accurately and efficiently. Our machine enables simulation-based GW population inferences to take on data at a new complexity level.

We derive the low-temperature behavior of the Casimir-Polder free energy for a polarizable atom interacting with graphene sheet which possesses the nonzero energy gap $\mathrm{\Delta }$ and chemical potential $\mu$. The response of graphene to the electromagnetic field is described by means of the polarization tensor in the framework of the Dirac model on the basis of first principles of thermal quantum field theory in the Matsubara formulation. It is shown that the thermal correction to the Casimir-Polder energy consists of three contributions. The first of them is determined by the Matsubara summation using the polarization tensor defined at zero temperature, whereas the second and third contributions are caused by an explicit temperature dependence of the polarization tensor and originate from the zero-frequency Matsubara term and the sum of all Matsubara terms with nonzero frequencies, respectively. The asymptotic behavior for each of the three contributions at low temperature is found analytically for any value of the energy gap and chemical potential. According to our results, the Nernst heat theorem for the Casimir-Polder free energy and entropy is satisfied for both $\mathrm{\Delta }>2\mu$ and $\mathrm{\Delta }<2\mu$. We also reveal an entropic anomaly arising in the case $\mathrm{\Delta }=2\mu$. The obtained results are discussed in connection with the long-standing fundamental problem in Casimir physics regarding the proper description of the dielectric response of matter to the electromagnetic field.

We consider the possibility of explaining the recent $R_K$ and $R_{K^{*}}$ anomalies in a two-Higgs doublet model, known as aligned, combined with a low-scale seesaw mechanism generating light neutrino masses and mixings. In this class of models, a large Yukawa coupling allows for significant nonuniversal leptonic contributions, through box diagrams mediated by charged Higgs bosons and right-handed neutrinos, to the $b\to s{\ell }^{+}{\ell }^{-}$ transition that can then account for both $R_K$ and $R_{K^{*}}$ anomalies.

We propose a novel approach to compute the cross section of near-threshold $J/\psi$ and $\mathrm{\Upsilon }$ production in electron-proton scattering at large photon virtualities $Q^2$ based on an operator product expansion. We show that the process can be used to extract the gluon part of the D-term gravitational form factor of the proton. At the subleading level, it is also sensitive to the trace anomaly effect of QCD.

Large rapidity gap diffraction processes are considered in multichannel eikonal models. It is shown that shadow corrections to overfast rising contribution of the input supercritical Pomeron (with $\alpha (0)>1$), originating from the Pomeron rescatterings or, equivalently, accounting survival probability factor, do not solve the Finkelstein-Kajantie problem. Therefore, in our opinion, another method of unitarization of supercritical Pomeron should be developed.

Recent observations of neutron stars with radio, x rays, and gravitational waves have begun to constrain the equation of state for nuclear matter beyond the nuclear saturation density. To one’s surprise, there exist approximate universal relations connecting certain bulk properties of neutron stars that are insensitive to the underlying equation of state and having important applications on probing fundamental physics including nuclear and gravitational physics. To date, analytic works on universal relations for realistic neutron stars are lacking, which may lead to a better understanding of the origin of the universality. Here, we focus on the universal relations between the compactness ($\mathcal{C}$), the moment of inertia ($I$), and the tidal deformability (related to the Love number) and derive analytic, approximate I-Love-C relations. To achieve this, we construct slowly rotating and tidally deformed neutron star solutions analytically starting from an extended Tolman VII model that accurately describes nonrotating realistic neutron stars, which allows us to extract the moment of inertia and the tidal deformability on top of the compactness. We solve the field equations analytically by expanding them about the Newtonian limit and keeping up to sixth order in the stellar compactness. Based on these analytic solutions, we can mathematically demonstrate the $\mathcal{O}(10\%)$ equation-of-state variation in the I-C and Love-C relations and the $\mathcal{O}(1\%)$ variation in the I-Love relation that have previously been found numerically. Our new analytic relations agree more accurately with numerical results for realistic neutron stars (especially the I-C and Love-C ones) than the analytic relations for constant-density stars derived in previous work. Based on these analytic findings, we attribute a possible origin of the universality for the I-C and Love-C relations to the fact that the energy density of realistic neutron stars can be approximated as a quadratic function, as is the case for the Tolman VII solution.

We study the gravitational field of the NUT-like source in the linearized (ghost-free) infinite derivative gravity. Such a source is equivalent to the spinning semi-infinite cosmic string with no tension. In general relativity, the linearized (massless) Taub-NUT solution has a curvature singularity as well as a topological defect corresponding to distributional curvature on one half of the symmetry axis called the Misner string. We find the NUT-charged spacetime in the linearized infinite derivative gravity. We show that it is free from curvature singularities as well as Misner strings. We also discuss an asymptotic limit along the symmetry axis that leads to the spacetime of a spinning cosmic string of infinite length.

In the presence of an external magnetic field, the axion and the photon mix. In particular, the dispersion relation of a longitudinal plasmon always crosses the dispersion relation of the axion (for small axion masses), thus leading to a resonant conversion. Using thermal field theory, we concisely derive the axion emission rate, applying it to astrophysical and laboratory scenarios. For the Sun, depending on the magnetic field profile, plasmon-axion conversion can dominate over Primakoff production at low energies ($\lesssim 200\mathrm{eV}$). This both provides a new axion source for future helioscopes and, in the event of discovery, would probe the magnetic field structure of the Sun. In the case of white dwarfs (WDs), plasmon-axion conversion provides a pure photon coupling probe of the axion, which may contribute significantly for low-mass WDs. Finally, we rederive and confirm the axion absorption rate of the recently proposed plasma haloscopes.

We show that the “defective” terms in the expression that Dondera [Phys. Rev. D 98, 096008 (2018)] obtained for the momentum of the retarded field of an accelerating point charge are mathematically well justified. The repair should not be sought in assigning an accelerating “bare” charge ad hoc compensating attributes. We advance a conjecture, supported by published work, concerning the Hadamard finite part of the divergent integral for the retarded-field momentum in question.

Even if the concerns related to the naturalness of the electroweak scale are repressed, the Higgs mass and stability of the electroweak vacuum do not allow arbitrarily large supersymmetry breaking scale, $M_S$, in the minimal models with split or high-scale supersymmetry. We show that $M_S$ can be raised to the grand unified theory (GUT) scale if the theory below $M_S$ contains a Higgs doublet, a pair of TeV scale Higgsino and widely separated gauginos in addition to the Standard Model particles. The presence of wino and gluino below $\mathcal{O}(100)\mathrm{TeV}$ leads to precision unification of the gauge couplings consistent with the current limits on the proton lifetime. Wino, at this scale, renders the Higgsino as pseudo-Dirac dark matter which in turn evades the existing constraints from the direct detection experiments. Bino mass scale is required to be $\gtrsim {10}^{10}\mathrm{GeV}$ to get the observed Higgs mass respecting the current limit on the charged Higgs mass. The framework predicts, $1\lesssim \tan \beta \lesssim 2.2$ and $\tau [p\to e^{+}{\pi }^0]<7\times {10}^{35}\mathrm{years}$, almost independent of values of the other parameters. The electroweak vacuum is found to be stable or metastable. The underlying framework provides an example of a viable sub-GUT scale theory of supersymmetric grand unified theory in which supersymmetry and unified gauge symmetry are broken at a common scale.

In light of no new physics being discovered at the LHC, ideas which tackle the hierarchy problem without novelties around the TeV scale must be taken seriously. Such is a cosmological relaxation model of the Higgs boson mass, proposed in the pre-LHC era, which does not rely on new physics below the Planck scale. This scenario introduces a different notion of naturalness according to which the vacuum with a small expectation value of the Higgs field corresponds to an infinitely enhanced entropy point of the vacuum landscape that becomes an attractor of cosmological inflationary evolution. In this framework we study numerically the evolution of the Higgs vacuum expectation value (VEV). We model the inflationary vacuum-to-vacuum transitions that are triggered by nucleation of branes charged under three-form fields as a random walk. In particular, we investigate the impact of the number of coupled three-forms on the convergence rate of the Higgs VEV. We discover an enhanced rate when increasing the number of brane charges. Moreover, we show that for late times the inclusion of more charges is equivalent to additional brane nucleations.

We analyze patterns from $CP$–violating new physics (NP) in hadronic and semileptonic rare charm $|\mathrm{\Delta }c|=|\mathrm{\Delta }u|=1$ transitions. Observation of direct $CP$ violation in hadronic decays, as in $\mathrm{\Delta }{A}_{CP}$, provides opportunities for $c\to u{\ell }^{+}{\ell }^{-}$, $\ell =e,\mu$ transitions, and vice versa. For the concrete case of flavorful, anomalyfree $Z^{\prime }$–models a NP–interpretation of $\mathrm{\Delta }{A}_{CP}$ suggests measurable $CP$ asymmetries in semileptonic decays such as $D\to \pi {\ell }^{+}{\ell }^{-}$ or $D\to \pi \pi {\ell }^{+}{\ell }^{-}$. Conversely, an observation of $CP$ violation in $c\to u{e}^{+}{e}^{-}$ or $c\to u{\mu }^{+}{\mu }^{-}$ decays supports a NP–interpretation of $\mathrm{\Delta }{A}_{CP}$. Flavorful $U(1{)}^{\prime }$–extensions provide explicit U–spin and isospin breaking which can be probed in patterns of hadronic decays of charm mesons. We work out signatures for $CP$ asymmetries in $D^0\to {\pi }^{+}{\pi }^{-}$, $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^0{\pi }^0$, $D^{+}\to {\pi }^{+}{\pi }^0$ decays, which can be probed in the future at LHCb and Belle II and provide further informative cross checks.