We compute the bound state properties of three-dimensional scalar ${\varphi }^4$ theory in the broken phase. To this end, we extend the recently developed technique of spectral Dyson-Schwinger equations to solve the Bethe-Salpeter equation and determine the bound state spectrum. We employ consistent truncations for the two-, three- and four-point functions of the theory that recover the scaling properties in the infinite coupling limit. Our result for the mass of the lowest-lying bound state in this limit agrees very well with lattice determinations.

The gravitational wave (GW) spectrum at frequencies above a kHz is a largely unexplored frontier. We show that detectors with sensitivity to single-phonon excitations in crystal targets can search for GWs with frequencies, $1\mathrm{THz}\lesssim f\lesssim 100\mathrm{THz}$, corresponding to the range of optical phonon energies, $1\mathrm{meV}\lesssim \omega \lesssim 100\mathrm{meV}$. Such detectors are already being built to search for light dark matter (DM), and therefore sensitivity to high-frequency GWs will be achieved as a byproduct. We begin by deriving the absorption rate of a general GW signal into single phonons. We then focus on carefully defining the detector sensitivity to monochromatic and chirp signals, and compute the detector sensitivity for many proposed light DM detection targets. The detector sensitivity is then compared to the signal strength of candidate high-frequency GW sources, e.g., superradiant annihilation and black hole inspiral, as well as other recent detector proposals in the $1\mathrm{MHz}\lesssim f\lesssim 100\mathrm{THz}$ frequency range. With a judicious choice of target materials, a collection of detectors could optimistically achieve sensitivities to monochromatic signals with $h_0\sim {10}^{-23}-{10}^{-25}$ over $1\mathrm{THz}\lesssim f\lesssim 100\mathrm{THz}$.

We propose a framework to account for neutrino masses at the two-loop level. This mechanism introduces new scalars and Majorana fermions to the Standard Model. It assumes the existence of a global $\mathrm{U}(1)\times {\mathcal{Z}}_2$ symmetry which after partial breaking provides the stability of the dark matter candidates of the theory. The rich structure of the potential allows for the possibility of first-order phase transitions (FOPTs) in the early Universe which can lead to the generation of primordial gravitational waves. Taking into account relevant constraints from lepton flavor violation, neutrino physics, as well as the trilinear Higgs couplings at next-to-leading order accuracy, we have found a wide range of possible FOPTs which are strong enough to be probed at the proposed gravitational-wave interferometer experiments such as LISA.

In this article, we study associated production of prompt $J/\psi (\mathrm{\Upsilon })$ and $D$ mesons in the improved color evaporation model using the high-energy factorization approach as it is realized in the Monte Carlo event generator KaTie. The modified Kimber-Martin-Ryskin-Watt model for unintegrated parton distribution functions is used. We predict cross sections for associated $J/\psi (\mathrm{\Upsilon })$ and $D$ meson hadroproduction via the single and double parton scattering mechanisms using the set of model parameters which has been fixed early for description of prompt single and pair heavy quarkonium production at the LHC energies. We found the results of calculations agree with the LHCb Collaboration data at the energies $\sqrt{s}=7$, 8 TeV and we present theoretical predictions for the energy $\sqrt{s}=13\mathrm{TeV}$.

We propose new cross section ratios in ultraperipheral $\mathrm{A}+\mathrm{A}$ and $p+\mathrm{A}$ collisions (UPCs) as a potential experimental signal of saturation physics. We consider the ratio $R_1$ of elastic vector meson photoproduction cross section to the inclusive hadron or jet photoproduction cross section. The ratio can be measured in the $\gamma +\mathrm{A}$ and $\gamma +p$ collisions taking place in the UPCs. We label the ratios $R_1(\mathrm{A})$ and $R_1(p)$, respectively. Constructing the double ratio $R_{\mathrm{UPC}}(\mathrm{A})=R_1(\mathrm{A})/R_1(p)$, and performing a small-$x$ calculation both in the quasiclassical approximation and by including small-$x$ evolution, we observe that $R_{\mathrm{UPC}}(\mathrm{A})$ exhibits a markedly different dependence on the nuclear atomic number inside and outside the saturation region. This result indicates that $R_{\mathrm{UPC}}(\mathrm{A})$ and $R_1(\mathrm{A})$ measurements in UPCs may help in the experimental searches for the evidence of saturation physics.

The recent pulsar timing arrays (PTAs) nano-Hz gravitational wave (GW) background signal can be naturally induced by the annihilation of domain walls (DWs) formed at a symmetry-breaking scale $f\simeq 200\mathrm{TeV}$ in the clockwork axion framework. Based on our first successful and precise prediction, we, for the first time, suggest that the recent PTA observations strongly support the novel mechanism of the QCD instanton-induced DW annihilation in the clockwork axion framework. We also, for the first time, discover a novel correlation between dark matter relic abundance and nano-Hz GW background, which in turn indicates a natural connection between the axion decay constant and the symmetry-breaking scale in the clockwork framework. We find that the GW signal has a peak $h^2{\mathrm{\Omega }}_{\mathrm{GW}}\simeq {10}^{-6.6}-{10}^{-6.1}$ at about 50 nHz, which is definite and testable for future PTA data at frequencies $\gtrsim 25\mathrm{nHz}$ and CMB-S4 experiment. We also propose various phenomena that may appear in PTAs and future GW interferometers.

We study the information paradox of Reissner-Nordström anti–de Sitter black holes in the large dimension limit by using the island formula. The entanglement entropy of Hawking radiation is calculated both for the nonextremal and the extremal cases, in which the boundary of the radiation region is close to the outer horizon. For the nonextremal case, the entanglement entropy of Hawking radiation obeys the Page curve, i.e., the entanglement entropy of Hawking radiation increases with time and reaches saturation about twice Bekenstein-Hawking entropy at the Page time. For the extremal case, the entanglement entropy of Hawking radiation becomes ill defined in the absence of the island due to the appearance of the singularity at the origin of the radial coordinate, while when the island exists, the entanglement entropy is found to be equal to the Bekenstein-Hawking entropy. In addition, for the case where the boundary of the radiation region is close to the horizon, there are some obvious constraints required by the existence of the island solution for both nonextremal and extremal cases, which can be utilized to put constraints on the size of the black hole. These results reveal new features of the semiclassical large $D$ black holes from the island perspective.

The weak-field limit of Einstein-Cartan (EC) relativity is studied. The equations of EC theory are rewritten such that they formally resemble those of Einstein general relativity (EGR); this allows ideas from post-Newtonian theory to be imported without essential change. The equations of motion are then written both at first post-Newtonian (1PN) order and at 1.5PN order. EC theory’s 1PN equations of motion are found to be those of a micropolar/Cosserat elastic medium, along with a decoupled evolution equation for nonclassical, spin-related fields. It seems that a necessary condition for these results to hold is that one chooses the nonclassical fields to scale with the speed of light in a certain empirically reasonable way. Finally, the 1.5PN equations give greater insight into the coupling between energy-momentum and spin within slowly moving, weakly gravitating matter. Specifically, the weakly relativistic modifications to Cosserat theory involve a gravitational torque and an augmentation of the gravitational force due to a dynamic mass moment density with an accompanying dynamic mass moment density flux, and new forms of linear momentum density captured by a dynamic mass density flux and a dynamic momentum density.

We study the shadows cast by rotating hairy black holes with two nontrivial time-periodic scalar fields having a nonflat Gaussian curvature of the target space spanned by the scalar fields. Such black holes are a viable alternative to the Kerr black hole, having a much more complicated geodesic structure and resulting shadows. We investigate how a nontrivial Gauss curvature alters the pictures for different amounts of scalar hair around the black holes, quantified by a normalized charge. Our results show that for high values of this charge, close to a boson star limit, chaotic shadows are observed with multiple small disconnected components for all considered Gaussian curvatures. For moderately large amounts of scalar hair and corresponding normalized charge, although the shadows still exhibit chaotic behavior, a dominant shadow component emerges, the size and shape of which are substantially influenced by the Gaussian curvature. For instance, highly chaotic shadows for flat target space, start developing a large central shadow region with the increase of the Gauss curvature even for black holes with substantially heavy scalar hair. For lower values of the normalized charge, the shadows resemble qualitatively the Kerr black hole while the Gaussian curvature has a small impact on their properties.

We investigate quadratic quasinormal mode coupling in black hole spacetime through numerical experiments of single perturbed black holes using both numerical relativity and second-order black hole perturbation theory. Focusing on the dominant $\ell =|m|=2$ quadrupolar modes, we find good agreement (within $\sim 10\%$) between these approaches, with discrepancies attributed to truncation error and uncertainties from mode fitting. Our results align with earlier studies extracting the coupling coefficients from select binary black hole merger simulations, showing consistency for the same remnant spins. Notably, the coupling coefficient is insensitive to a diverse range of initial data, including configurations that led to a significant (up to 5%) increase in the remnant black hole mass. These findings present opportunities for testing the nonlinear dynamics of general relativity with ground-based gravitational wave observatories. Lastly, we provide evidence of a bifurcation in coupling coefficients between counterrotating and corotating quasinormal modes as black hole spin increases.

We explore a self-interacting neutrino cosmology in which neutrinos experience a delayed onset of free-streaming. We use the effective field theory of large-scale structure (LSS) to model matter distribution on mildly nonlinear scales within the self-interacting neutrino cosmology for the first time. We perform the first combined likelihood analysis of BOSS full-shape galaxy clustering, weak lensing, and Lyman-$\alpha$ forest measurements, together with the cosmic microwave background (CMB) data from Planck. We find that the full dataset strongly favors presence of a flavor-universal neutrino self-interaction, with a characteristic energy scale of order 10 MeV. The preference is at the $\sim 5\sigma$ level and is primarily driven by the Lyman-$\alpha$ forest measurements and, to a lesser extent, the weak lensing data from the Dark Energy Survey (DES). The self-interacting neutrino model eases both the Hubble tension and the $S_8$ tension between different cosmological datasets, but it does not resolve either. Finally, we note a preference for a nonzero sum of neutrino masses at the level of $\sim 0.3\mathrm{eV}$ under this model, consistent with previous bounds. These results call for further investigation in several directions, and may have significant implications for neutrino physics and for future new-physics searches with galaxy surveys.

We present an extensive study of the effects of neutrino transport in three-dimensional general relativistic radiation hydrodynamics (GRHD) simulations of binary neutron star (BNS) mergers using our moment-based, energy-integrated neutrino radiation transport (M1) scheme. We consider a total of eight BNS configurations, while varying equation of state models, mass ratios, and grid resolutions, for a total of 16 simulations. We find that M1 neutrino transport is crucial in modeling the local absorption of neutrinos and the deposition of lepton number throughout the medium. We provide an in-depth look at the effects of neutrinos on the fluid dynamics and luminosity during the late inspiral and postmerger phases, the properties of ejecta and outflow, and the postmerger nucleosynthesis. The simulations presented in this work comprise an extensive study of the combined effect of the equation of state and M1 neutrino transport in GRHD simulations of BNS mergers, and establish that the solution provided by our M1 scheme is robust across system properties.

The first stars are expected to form through molecular-hydrogen (${\mathrm{H}}_2$) cooling, a channel that is especially sensitive to the thermal and ionization state of gas, and can thus act as a probe of exotic energy injection from decaying or annihilating dark matter (DM). Here, we use a toy halo model to study the impact of DM-sourced energy injection on the ${\mathrm{H}}_2$ content of the first galaxies, and thus estimate the threshold mass required for a halo to form stars at high redshifts. We find that currently allowed DM models can significantly change this threshold, producing both positive and negative feedback. In some scenarios, the extra heating of the gas raises the halo mass required for collapse, whereas in others, energy injection lowers the threshold by increasing the free-electron fraction and catalyzing ${\mathrm{H}}_2$ formation. The direction of the effect can be redshift-dependent. We also bracket the self-shielding uncertainties on the impact of the Lyman-Werner radiation from DM. Hence, exotic energy injection can both delay and accelerate the onset of star formation; we show how this can impact the timing of 21-cm signals at cosmic dawn. We encourage detailed simulation follow-ups in the most promising regions of parameter space identified in this work.

The equations of state (EOSs) governing neutron star (NS) matter obtained for both nonrelativistic and relativistic mean-field models are systematically confronted with a diverse set of terrestrial data and astrophysical observations within the Bayesian framework. The terrestrial data, spanning from bulk properties of finite nuclei to the heavy-ion collisions, constrain the symmetric nuclear matter EOS and the symmetry energy up to twice the saturation density (${\rho }_0=0.16{\mathrm{fm}}^{-3}$). The astrophysical observations encompass the NS radius, the tidal deformability, and the lower bound on maximum mass. Three distinct posterior distributions of EOSs are generated by gradually updating the priors with different constraints: (i) only the maximum NS mass, (ii) incorporating additional terrestrial data, and (iii) combining both the terrestrial data and astrophysical observations. These EOS distributions are then compared using the Kullback-Liebler divergence which highlights the significant constraints imposed on the EOSs by the currently available lower bound of NS maximum mass and terrestrial data. The remaining astrophysical observations marginally refine the EOS within the density range $\sim 2–3{\rho }_0$. It is observed that the relativistic mean-field model yields stiffer EOS around the saturation density but predicts smaller values of the speed of sound and proton fraction in the interior of massive stars.

We analyze how entanglement is generated and distributed in a Bhabha scattering process $(e^{-}{e}^{+}\to e^{-}{e}^{+})$ at tree level. In our setup an electron $A$ scatters with a positron $B$, which is initially entangled with another electron $C$ (spectator), that does not participate directly to the process. We find that the QED scattering generates and distributes entanglement in a nontrivial way among the three particles; the correlations in the output channels $AB$, $AC$, and $BC$ are studied in detail as functions of the scattering parameters and of the initial entanglement weight. Although derived in a specific case, our results exhibit some general features of other similar QED scattering processes, for which the extension of the present analysis is straightforward.

In earlier papers it was shown that the correct kinetic term for scalar, vector gauge field and the spin two field in ${\mathrm{AdS}}_{D+1}$ space is obtained starting from the exact renormalization group (ERG) equation for a ${\mathrm{CFT}}_D$ perturbed by scalar composite, conserved vector current, and conserved traceless energy momentum tensor respectively. In this paper interactions are studied, and it is shown that a flipped version of the Polchinski ERG equation that evolves toward the UV can be written down and is useful for making contact with the usual AdS/CFT prescriptions for correlation function calculations. The scalar-scalar-spin-2 interaction in the bulk is derived from the ERG equation in the large $N$ semiclassical approximation. It is also shown that after mapping to AdS the interaction is local on a scale of the bare cutoff rather than the moving cutoff (which would have corresponded to the anti–de Sitter scale). The map to ${\mathrm{AdS}}_{D+1}$ plays a crucial role in this locality. The local nature of the coupling ensures that this interaction term in the bulk action is obtained by gauge fixing a general coordinate invariant scalar kinetic term in the bulk action. A wave function renormalization of the scalar field is found to be required for a mutually consistent map of the two fields to ${\mathrm{AdS}}_{D+1}$.

We critically examine the applicability of the effective potential within dynamical situations and find, in short, that the answer is negative. An important caveat of the use of an effective potential in dynamical equations of motion is an explicit violation of energy conservation. An adiabatic effective potential is introduced in a consistent quasistatic approximation, and its narrow regime of validity is discussed. Two ubiquitous instances in which even the adiabatic effective potential is not valid in dynamics are studied in detail: parametric amplification in the case of oscillating mean fields, and spinodal instabilities associated with spontaneous symmetry breaking. In both cases profuse particle production is directly linked to the failure of the effective potential to describe the dynamics. We introduce a consistent, renormalized, energy conserving dynamical framework that is amenable to numerical implementation. Energy conservation leads to the emergence of asymptotic highly excited, entangled stationary states from the dynamical evolution. As a corollary, decoherence via dephasing of the density matrix in the adiabatic basis is argued to lead to an emergent entropy, formally equivalent to the entanglement entropy. The results suggest novel characterization of asymptotic equilibrium states in terms of order parameter vs energy density.

We numerically simulate the motion of a black hole as it plunges radially through an ultralight dark matter (ULDM) soliton. We investigate the timescale in which dynamical friction reduces the kinetic energy of the black hole to a minimum and consider the sensitivity of this timescale to changes in the ULDM particle mass, the total soliton mass, and the mass of the black hole. We contrast our numerical results with a semianalytic treatment of dynamical friction and find that the latter is poorly suited to this scenario. In particular, we find that the backreaction of the soliton to the presence of the black hole is significant, resulting in oscillations in the coefficient of dynamical friction which cannot be described in the simple semianalytical framework. Furthermore, we observe a late-time reheating effect, in which a significant amount of kinetic energy is transferred back to the black hole after an initial damping phase. This complicates the discussion of ULDM dynamical friction on the scales relevant to the final parsec problem.

We present general relativistic magnetohydrodynamic simulations of merging equal-mass spinning black holes embedded in an equatorial thin slab of magnetized gas. We explore configurations with black holes that are nonspinning, with spins aligned to the orbital angular momentum, and with misaligned spins. The rest-mass density of the gas slab follows a Gaussian profile symmetric relative to the equatorial plane and it is initially either stationary or with Keplerian rotational support. As part of our diagnostics, we track the accretion of matter onto the black hole horizons and the Poynting luminosity. Throughout the inspiral phase, configurations with nonzero spins display modulations in the mass accretion rate that are proportional to the orbital frequency and its multiples. Frequency analysis suggests that these modulations are a generic feature of inflows on merging binaries. In contrast to binary models evolved in a gas cloud scenario, we do not observe a significant increase in the mass accretion rate after the merger in any of our simulations, suggesting the possibility of not detecting a peak luminosity at the time of merger in future electromagnetic observations.

We study a three-dimensional holographic conformal field theory under the influence of a background electric field on a spacetime containing two black hole horizons. The electric background is fixed such that there is potential difference between the two boundary black holes, inducing a conserved current. By constructing the holographic duals to this setup, which are solutions to the Einstein-Maxwell equations with a negative cosmological constant in four dimensions, we calculate, to a fully nonlinear level, the conductivity of the conformal field theory in this background. Interestingly, we find that the conductivity depends nontrivially on the potential difference. The bulk solutions are flowing geometries containing black hole horizons which are non-Killing and have nonzero expansion. We find a novel property that the past boundary of the future horizon lies deep in the bulk and show this property remains present after small perturbations of the temperature difference of the boundary black holes.