We consider several families of functions $f(\alpha )$ that appear in the Bona-Masso slicing condition for the lapse function $\alpha$. Focusing on spherically symmetric and time-independent slices we apply these conditions to the Schwarzschild spacetime in order to construct analytical expressions for the lapse $\alpha$ in terms of the areal radius $R$. We then transform to isotropic coordinates and determine the dependence of $\alpha$ on the isotropic radius $r$ in the vicinity of the black-hole puncture. We propose generalizations of previously considered functions $f(\alpha )$ for which, to leading order, the lapse is proportional to $r$ rather than a noninteger power of $r$. We also perform dynamical simulations in spherical symmetry and demonstrate advantages of the above choices in numerical simulations employing spectral methods.

The origin of the $\mu \mathrm{G}$ magnetic fields observed in galaxies is unknown. One promising scenario is that magnetic fields generated during inflation, larger than 0.1 nG on Mpc scales, were adiabatically compressed to $\mu \mathrm{G}$ strengths in galaxies during structure formation. Thus, detecting a scale-invariant primordial magnetic field (PMF) above 0.1 nG on Mpc scales just after recombination would indicate an inflationary origin of galactic magnetic fields. This would also provide compelling evidence that inflation occurred since only an inflationary mechanism could generate such a strong, scale-invariant magnetic field on Mpc scales. In contrast, constraining the scale-invariant PMF strength to be below 0.1 nG would imply an inflationary scenario is not the primary origin, since such weak PMFs cannot be amplified enough via adiabatic compression to produce the strength of the galactic fields we observe today. We find that measurements of anisotropic birefringence by future CMB surveys will be able to improve the sensitivity to Mpc-scale inflationary PMFs by an order of magnitude, and, in particular, that CMB-HD would lower the upper bound to 0.072 nG at the 95% C.L., which is below the critical 0.1 nG threshold for ruling out a purely inflationary origin. If inflationary PMFs exist, we find that a CMB-HD survey would be able to detect them with about $3\sigma$ significance or higher, providing evidence for inflation itself.

We present a new publicly available code, class_rot, which modifies class to enable fast nonperturbative calculation of cosmic microwave background polarization power spectra due to both isotropic and anisotropic polarization rotation from cosmic birefringence. Cosmic birefringence can arise from new parity-violating physics such as axion dark matter with a Chern-Simons coupling to photons or Faraday rotation due to a primordial magnetic field. Constraints on these effects can be obtained by comparing measurements to precise numerical calculations of the polarization power spectra. We describe the implementation of class_rot in terms of both mathematical formalism and coding architecture.

Early dark energy (EDE) offers a particularly interesting theoretical approach to the Hubble tension, albeit one that introduces its own set of challenges, including a new “why then” problem related to the EDE injection time at matter-radiation equality, and a mild worsening of the large-scale structure (LSS) tension. Both these challenges center on the properties of dark matter, which becomes the dominant component of the Universe at EDE injection and is also responsible for seeding LSS. Motivated by this, we present the potential of couplings between EDE and dark matter to address these challenges, focusing on a mechanism similar to chameleon dark energy theories, deeming this chameleon early dark energy (CEDE). We present relevant background and perturbation equations and study the dynamics of the case of a quartic scalar potential and an exponential coupling.

The primordial universe might be highly inhomogeneous. We perform the $(3+1)\mathrm{D}$ numerical relativity simulation for the evolution of scalar field in an initial inhomogeneous expanding universe, and investigate how it populates the landscape with both de Sitter (dS) and anti–de Sitter (AdS) vacua. The simulation results show that eventually either the field in different region separates into different vacua, so that the expanding dS or AdS bubbles (the bubble wall is expanding but the spacetime inside AdS bubbles is contracting) come into being with clear boundaries, or overall region is dS expanding with a few smaller AdS bubbles (which collapsed into black holes) or inhomogeneously collapsing.

It is well known that enhancement in the primordial scalar perturbations over small scales generates detectable amplitudes of secondary gravitational waves (GWs), by sourcing the tensor perturbations at the second order. These stochastic gravitational waves are expected to carry the imprints of primordial non-Gaussianities. The scalar bispectrum that is typically produced in models of inflation leading to significant secondary GWs is nontrivial and highly scale dependent. In this work, we present a method to account for such general scale-dependent scalar bispectrum arising from inflationary models in the calculation of the spectral density of secondary GWs. Using this method, we compute the contributions arising from the scalar bispectrum to the amplitude of secondary GWs in two specific models of inflation driven by the canonical scalar field. We find that these non-Gaussian contributions can be highly model dependent and have to be consistently taken into account while estimating the total amplitude of the secondary GWs. Beyond the models considered, we emphasize that the method discussed is robust and free from assumptions about the shape of the bispectrum and generalizes earlier approaches adopted in the literature. We argue that this method of accounting for the scalar bispectrum shall be helpful in future computations for exotic models generating larger amplitudes of scalar non-Gaussianities along with a significant amount of secondary GWs.

We examine the dynamics of Friedmann-Lemaitre-Robertson-Walker cosmologies in which the vacuum interacts with a perfect fluid through an energy exchange, focusing on the exploration of nonsingular configurations, including cyclic and bouncing models. We consider two specific choices for the energy transfer. In the first case, the energy transfer is proportional to a linear combination of the vacuum and fluid energy densities which makes the conservation equations exactly integrable. The resulting Friedmann equation can be interpreted as an energy constraint equation with an effective potential for the scale factor that may include an infinite barrier forcing a bounce at small values of the scale factor, as well as a potential well allowing for cycling solutions. In the second case, the energy transfer is a nonlinear combination of the vacuum and fluid energy densities. Nonetheless even in this case the dynamics can be partially integrated, leading to a first integral, reducing the number of degrees of freedom. We show that also in this nonlinear case bouncing and cycling cosmologies may arise. In both cases the structure of the resulting phase space allows for nonsingular orbits with an early accelerated phase around a single bounce, connected via a decelerated matter-dominated era to a late-time accelerated phase dominated by an effective cosmological constant.

We provide a new constraint on the small-scale density fluctuations, evaluating the diffuse background free-free emission from dark matter halos in the dark ages. If there exists a large amplitude of the matter density fluctuations on small scales, the excess enhances the early formation of dark matter halos. When the virial temperature is sufficiently high, the gas in a halo is heated up and ionized by thermal collision. The heated ionized gas emits photons by the free-free process. We would observe the sum of these photons as the diffuse background free-free emission. Assuming the analytical dark matter halo model including the gas density and temperature profile, we calculate the intensity of the diffuse background free-free emission from early-formed dark matter halos in the microwave frequency range. Comparing with the recent foreground analysis on cosmic microwave background, we obtain the constraint on the excess of the density fluctuations on small scales. Our constraint corresponds to $P_{\zeta }\lesssim {10}^{-7}$ for $k\simeq 1–100{\mathrm{Mpc}}^{-1}$ with assuming the delta-function-type curvature power spectrum. Therefore, our constraint is the most stringent constraint on the perturbations below 1 Mpc scales.

We propose a novel scenario of dark matter production naturally connected with generation of gravitational waves. Dark matter is modeled as a real scalar, which interacts with the hot primordial plasma through a portal coupling to another scalar field. For a particular sign of the coupling, this system exhibits an inverse second order phase transition. The latter leads to an abundant dark matter production, even if the portal interaction is so weak that the freeze-in mechanism is inefficient. The model predicts domain wall formation in the Universe, a long time before the inverse phase transition. These domain walls have a tension decreasing with time and completely disappear at the inverse phase transition so that the problem of overclosing the Universe is avoided. The domain wall network emits gravitational waves with characteristics defined by those of dark matter. In particular, the peak frequency of gravitational waves is determined by the portal coupling constant and falls in the observable range for currently planned gravitational wave detectors.

Over the last several decades, radio detection of air showers has been widely used to detect ultrahigh-energy cosmic rays. We developed an experiment under controlled laboratory conditions at SLAC with which we measured the radio-frequency radiation from a charged particle shower produced by bunches of electrons as primaries with known energy. The shower took place in a target made of high density polyethylene located in a strong magnetic field. The experiment was designed so that Askaryan and magnetically-induced components of the radio emission could be measured independently. At the same time, we performed a detailed simulation of this experiment to predict the radio signal using two microscopic formalisms, endpoint and ZHS. In this paper, we present the simulation scheme and make a comparison with data characteristics such as linearity with magnetic field and amplitude. The simulations agree with the measurements within uncertainties and present a good description of the data. In particular, reflections within the target that accounted for the largest systematic uncertainties are addressed. The prediction of the amplitude of Askaryan emission agrees with measurements to within 5% for the endpoint formalism and 11% for the ZHS formalism. The amplitudes of magnetically-induced emission agree to within 5% for the endpoint formalism and less than 1% for the ZHS formalism. The agreement of the absolute scale of emission gives confidence in state-of-the-art air shower simulations which are based on the applied formalisms.

Coherent WaveBurst is a generic, multidetector gravitational wave burst search based on the excess power approach. The coherent WaveBurst algorithm currently employed in the all-sky short-duration gravitational wave burst search uses a conditional approach on selected attributes in the multidimensional event attribute space to distinguish between noisy events from that of astrophysical origin. We have been developing a supervised machine learning approach based on the Gaussian mixture modeling to model the attribute space for signals as well as noise events to enhance the probability of burst detection [Gayathri et al.Phys. Rev. D 102, 104023 (2020)]. We further extend the Gaussian mixture model approach to the all-sky short-duration coherent WaveBurst search as a postprocessing step on events from the first half of the third observing run (O3a). We show an improvement in sensitivity to generic gravitational wave burst signal morphologies as well as the astrophysical source such as core-collapse supernova models due to the application of our Gaussian mixture model approach to coherent WaveBurst triggers. The Gaussian mixture model method recovers the gravitational wave signals from massive compact binary coalescences identified by coherent WaveBurst targeted for binary black holes in GWTC-2, with better significance than the all-sky coherent WaveBurst search. No additional significant gravitational wave bursts are observed.

Motivated by finding a way to construct the universal relations between the neutron star properties and obtaining the application scope of the universal relations, the linear correlation properties between several properties of neutron stars are analyzed. Based on this, several existing universal relations are tested and several new universal relations are predicted. The results show that in the whole typical central density range of neutron stars, the better the linear correlation properties between the combinations of physical quantities are, the better the universality of the universal relations will be. It is shown that the quantities possessing desired linear correlation properties are the compactness $\beta$, moment of inertia $I$, gravitational redshift $z$ and gravitational binding energy $E_g$, etc. Based on the linear correlation analysis of the above acquired quantities, several existing universal relations about the dimensionless gravitational binding energy and several new universal relations about the dimensionless moment of inertia are tested and predicted respectively. Moreover, the moment of inertia of PSR $\mathrm{J}0030+0451$ can be constrained by the newly discovered universal relation. In conclusion, the linear correlation analysis of the neutron star properties is an effective and feasible method to explore the universal relations.

We estimate the stochastic gravitational-wave background arising from all stellar core-collapse events in the universe based on the gravitational-wave signal predictions of recent numerical simulations. We focus on waveforms from slowly or nonrotating stars and include rapidly rotating, highly massive progenitors as extreme case limits. Our most realistic estimates are more than one hundred times below the sensitivity of third-generation terrestrial gravitational-wave detectors and likely weaker than cosmological contributions to the stochastic gravitational-wave background.

We present new constraints on the merging rates of planetary-mass and asteroid-mass primordial black hole binaries using limits on continuous waves (quasimonochromatic, quasi-infinite duration signals) derived from an all-sky search for isolated compact objects in the first six months of the third observing run (O3a) of LIGO/Virgo. We calculate the merging rates of these binaries in a model-independent way, and convert them to constraints on the primordial black hole abundance with minimal modeling assumptions. Our results show that all-sky searches are sensitive to sources at most $\mathcal{O}(10\mathrm{pc})$ away for systems with chirp masses of $\mathcal{O}({10}^{-5}{M}_{\odot })$ at gravitational-wave frequencies around 30 Hz–40 Hz. These results also show that continuous-wave searches could in the future directly probe the existence of planetary-mass and asteroid-mass primordial black holes, especially those in binaries with asymmetric mass ratios. Furthermore, they demonstrate that new methods accounting for the full nonlinear gravitational-wave frequency evolution are needed to improve constraints on primordial black holes.

We study the transverse polarization of hyperons produced in semi-inclusive deep inelastic scattering, $ep\to e{\mathrm{\Lambda }}^{\uparrow }X$, in the framework of the collinear twist-3 factorization. The cross section from the twist-3 distribution functions and the twist-3 quark fragmentation functions is computed in the leading order with respect to the QCD coupling constant. The constraint relations among the twist-3 FFs are taken into account to simplify the formula. The formula is relevant to large-$P_T$ hyperon production in the future Electron Ion Collider experiment.

We evaluate the contribution of scalar mesons to the hadronic light-by-light piece of the muon anomalous magnetic moment, using a warped five-dimensional model and holographic methods. We assess the contribution of the lightest, sub-GeV scalars $\sigma (500)$, $a_0(980)$, and $f_0(980)$ together with their associated towers of excited states, which the model generates automatically. Our results point at a clearly negative contribution, overwhelmingly dominated by the $\sigma (500)$ meson, that we estimate at $a_{\mu }^{\mathrm{HLbL},\mathrm{S}}=-9(2)\times {10}^{-11}$. This number is in very good agreement with the most recent determinations from dispersive analyses.

We first show that the effective nonrelativistic theory of gravitationally interacting, massive integer-spin fields (spin-0, 1, and 2 in particular) is described by a $2s+1$ component Schrödinger-Poisson action, where $s$ is the spin of the field. We then construct $s+1$ distinct, gravitationally supported solitons in this nonrelativistic theory from identically polarized plane waves. Such solitons are extremally polarized, with macroscopically large spin, but no orbital angular momentum. These $s+1$ solitons form a basis set, out of which partially polarized solitons can be constructed. All such solitons are ground states, have a spherically symmetric energy density but not field configurations. We discuss how solitons in higher-spin fields can be distinguished from scalar solitons, and potential gravitational and nongravitational probes of them.

Fully polarized nonlinear Breit-Wheeler pair production from a beam of polarized seed photons is investigated in pulsed plane wave backgrounds. The particle (electron and positron) spin and photon polarization are comprehensively described with the theory of the density matrix. The compact expressions for the energy spectrum and spin polarization of the produced particles, depending on the initial polarization of the seed photon beam, are derived and discussed in both linearly and circularly polarized laser backgrounds. The numerical results suggest an appreciable improvement of the positron yield by orthogonalizing the photon polarization to the laser polarization, and the generation of a highly polarized positron beam from a beam of circularly polarized seed photons. The locally monochromatic approximation and the locally constant field approximation are derived and benchmarked with the full quantum electrodynamic calculations.

The growing interest in the interactions between dark matter particles and electrons has received a further boost by the observation of an excess in electron recoil events in the XENON1T experiment. Of particular interest are dark matter models in which the scattering process is inelastic, such that the ground state can upscatter into an excited state. The subsequent exothermic downscattering of such excited states on electrons can lead to observable signals in direct detection experiments and gives a good fit to the XENON1T excess. In this work, we study terrestrial upscattering, i.e., inelastic scattering of dark matter particles on nuclei in the Earth, as a plausible origin of such excited states. Using both analytical and Monte Carlo methods, we obtain detailed predictions of their density and velocity distribution. These results enable us to explore the time dependence of the flux of excited states resulting from the rotation of the Earth. For the case of XENON1T, we find the resulting daily modulation of the electron recoil signal to be at the level of 10% with a strong dependence on the dark matter mass.

We study the modular symmetric standard model effective field theory. We employ the stringy Ansatz on coupling structure that 4-point couplings $y^{(4)}$ of matter fields are written by a product of 3-point couplings $y^{(3)}$ of matter fields, i.e., $y^{(4)}=y^{(3)}{y}^{(3)}$. In this framework, we discuss the flavor structure of bilinear fermion operators and 4-fermion operators, where the holomorphic and antiholomorphic modular forms appear. From the Ansatz, the $A_4$ modular-invariant semileptonic four-fermion operator $[{\overline{E}}_R\mathrm{\Gamma }{E}_R][{\overline{D}}_R\mathrm{\Gamma }{D}_R]$ does not lead to the flavor changing (FC) processes since this operator would be constructed in terms of gauge couplings $g$ as $y^{(3)}\sim g$. The chirality flipped bilinear operator $[{\overline{D}}_R\mathrm{\Gamma }{D}_L]$ also does not lead FC if the mediated mode corresponds to the Higgs boson $H_d$. In this case, the flavor structure of this operator is the exactly same as the mass matrix. On the other hand, if the flavor structure of the operator is not the exactly same as the mass matrix, the situation would change drastically. Then, we obtain the nontrivial relations of FC transitions at nearby fixed points $\tau =i,\omega ,i\infty$, which are testable in the future. As an application, we discuss the relations of the lepton flavor violation processes $\mu \to e\gamma ,\tau \to \mu \gamma$ and $\tau \to e\gamma$ at nearby ${\tau }_e=i$, where the successful lepton mass matrix was obtained. We also study the flavor changing 4-quark operators in the $A_4$ modular symmetry of quarks. As a result, the minimal flavor violation could be realized by taking relevant specific parameter sets of order one.