We examine some features of the nonrenormalizability induced through the use of low-energy effective Lagrangians in loop diagrams, in the context of a scalar model which is ultraviolet finite and partially soluble. In this framework, one can directly demonstrate the mechanism leading to the nonrenormalizability of the effective theory. This behavior is generated by approximations that are applicable at low energies but are generally inappropriate for evaluating loop diagrams that contain virtual high-energy particles. However, it is explicitly shown that one can match the results obtained in the renormalized effective theory with those found in the full theory at low energy. We argue that the infrared sectors of these theories are inherently similar, independently of the matching procedure. A closed-form expression is obtained, to leading order in the energy expansion, for the complete effective Lagrangian at all orders in perturbation theory. The model may be useful to clarify certain aspects of realistic, but more complex, effective field theories.

We present an exact time-dependent solution for a charged scalar field on a two-dimensional cylinder, that can be interpreted as representing a long-standing excitation on a $S$-wave superconducting state, which propagates along a nanotube constructed out of twisted bilayer graphene. The solution has a topological charge characterized by an integer number, which counts the winding of the Higgs phase winds around the cylinder. The resulting electric current generates its own electromagnetic field in a self-consistent way, without the need of any external fields to keep it alive.

The NASA Discovery-class mission VERITAS, selected in June 2021, will be launched toward Venus after 2027. In addition to the science instrumentation that will build global foundational geophysical datasets, VERITAS proposed to conduct a technology demonstration for the Deep Space Atomic Clock (DSAC-2). A first DSAC successfully operated in low-Earth orbit for more than two years, demonstrated the trapped ion atomic clock technology, and established a new level of performance for clocks in space. DSAC-2 would have further improvements in size, power, and performance. It would host a $1\times {10}^{-13}$ grade USO to produce a frequency output with short-term stability of less than $2\times {10}^{-13}/\sqrt{\tau }$ (where $\tau$ is the averaging time). However, due to funding shortfalls, DSAC-2, had to be canceled. The initially foreseen presence of an atomic clock on board the probe, however, raised the question whether this kind of instrumentation could be useful not only for navigation and time transfer but also for fundamental physics tests. In this work, we consider the DSAC-2 atomic clock and VERITAS mission as a specific example to measure possible discrepancies in the redshift predicted by general relativity by using an atomic clock onboard an interplanetary spacecraft. In particular we investigate the possibility of measuring possible violations of the local Lorentz invariance and local position invariance principles. We perform accurate simulations of the experiment during the VERITAS cruise phase. We consider different parametrizations of the possible violations of the general relativity, different operational conditions, and several different assumptions on the expected measurement performance. We show that DSAC-2 onboard VERITAS would provide new and improved constraints with respect to the current knowledge. Our analysis shows the scientific value of atomic clocks like DSAC-2 hosted onboard interplanetary spacecraft.

An effective-field theory framework, the Standard Model Extension, is used to investigate the existence of Lorentz and $CPT$-violating effects during gravitational wave propagation. We implement a modified equation for the dispersion of gravitational waves that includes isotropic, anisotropic and birefringent dispersion. Using the LIGO-Virgo-KAGRA algorithm library suite, we perform a joint Bayesian inference of the source parameters and coefficients for spacetime-symmetry breaking. From a sample of 45 high-confidence events selected in the GWTC-3 catalog, we obtain a maximal bound of $3.19\times {10}^{-15}\mathrm{m}$ at 90% CI for the isotropic coefficient $k_{(V)00}^{(5)}$ when assuming the anisotropic coefficients to be zero. The combined measurement of all the dispersion parameters yields limits on the order of ${10}^{-13}\mathrm{m}$ for the 16 $k_{(V)ij}^{(5)}$ coefficients. We study the robustness of our inference by comparing the constraints obtained with different waveform models, and find that a lack of physics in the simulated waveform may appear as spacetime-symmetry breaking-induced dispersion for a subset of events.

Thanks to their interpretation as the first order correction of general relativity at high energies, quadratic theories of gravity have gained much attention in recent times. Particular attention has been drawn to the Einstein-Weyl theory, where the addition of the squared Weyl tensor to the action opens the possibility of having non-Schwarzschild black holes in the classical spectrum of the theory. Static and spherically symmetric solutions of this theory have been studied and classified in terms of their small scales behavior; however, a classification of these solutions in terms of the asymptotic gravitational field is still lacking. In this paper we address this point and present a phase diagram of the theory, where the different types of solutions are shown in terms of their mass and the strength of a Yukawa-like correction to the gravitational field. In particular we will show that, in the case of compact stars, different equations of state imply different Yukawa corrections to the gravitational potential, with possible phenomenological implications.

We study the problem of plane monochromatic scalar waves impinging upon a Schwarzschild dirty black hole—a Schwarzschild black hole surrounded by a thin spherical shell of matter—using the complex angular momentum approach. We first recall general results concerning the differential scattering cross section in the classical limit through a null geodesic analysis by exploring different configurations of the shell. In particular, we show that dirty black hole spacetimes may exhibit various critical effects for geometrical optics. We compute the Regge pole spectrum for various shell configurations and show that it exhibits two or three distinct branches of poles, labeled inner surface waves, broad resonances and outer surface waves. In the latter, two subfamilies have been identified, the surface waves associated with the outer light-ring and the creeping modes associated with the surface of the shell. We show, using WKB analysis, that the position of the shell sets the real part of the broad resonances while its energy-momentum and the discontinuity of the potential at the shell’s surface set their imaginary part. Next, we provide the complex angular momentum representation of the differential scattering cross section and examine the role of the different Regge pole branches. We compute the differential scattering cross section for various configurations at several frequencies and show a very good agreement with the partial-wave calculations. Finally, we highlight the role of the critical effects, i.e., orbiting, glory, grazing, and rainbow scattering, and their impact on the differential scattering cross section.

We show that asymptotically de Sitter black holes of negative mass can exist in Lovelock gravity. Such black holes have horizon geometries with nonconstant curvature and are known as exotic black holes. We explicitly examine the case of Gauss-Bonnet gravity. We briefly discuss the positive mass case where we show how the transverse space geometry affects whether a black hole will exist or not. For negative mass solutions we show how three different black hole spacetimes are possible depending on the transverse space geometry. We also provide closed form bounds for the geometric parameters to ensure that a black hole spacetime is observed. We close with a discussion of the massless case, where there are many different spacetimes that are permitted.

We establish the Einstein-Euler-Heisenberg system of field equations with cosmological constant (EEH-$\mathrm{\Lambda }$) for type-$D$ metrics within the null tetrad formalism. Then we determine all type-$D$ solutions to the EEH-$\mathrm{\Lambda }$ equations; among the derived solutions are the Einstein-Euler-Heisenberg-$\mathrm{\Lambda }$ generalizations of the Bertotti-Robinson, Reissner-Nordström, Newman-Unti-Tamburino-B $(\mathrm{NUT}\text{−}\mathrm{B})(+)$, and Kerr-Newman solutions. Moreover it is shown that the (static) C–metric is not compatible with the Euler-Heisenberg electrodynamics.

We use physics-informed neural networks (PINNs) to compute the first quasinormal modes of the Kerr geometry via the Teukolsky equation. This technique allows us to extract the complex frequencies and separation constants of the equation without the need for sophisticated numerical techniques, and with an almost immediate implementation under the pytorch framework. We are able to compute the oscillation frequencies and damping times for arbitrary black hole spins and masses, with accuracy typically below the percentual level as compared to the accepted values in the literature. We find that PINN-computed quasinormal modes are indistinguishable from those obtained through existing methods at signal-to-noise ratios (SNRs) larger than 100, making the former reliable for gravitational-wave data analysis in the mid term, before the arrival of third-generation detectors like LISA or the Einstein Telescope, where SNRs of $\mathcal{O}(1000)$ might be achieved.

We study the nonequilibrium dynamics of axionlike particles (ALP) coupled to Standard Model degrees of freedom in thermal equilibrium. The quantum master equation (QME) for the ALP reduced density matrix is derived to leading order in the coupling of the ALP to the thermal bath, but to all orders of the bath couplings to degrees of freedom within or beyond the Standard Model other than the ALP. The QME describes the damped oscillation dynamics of an initial misaligned ALP condensate, thermalization with the bath, decoherence, and entropy production within a unifying framework. The ALP energy density $\mathcal{E}(t)$ features two components: a “cold” component from the misaligned condensate and a “hot” component from thermalization with the bath, with $\mathcal{E}(t)={\mathcal{E}}_c{e}^{-\gamma (T)t}+{\mathcal{E}}_h(1-e^{-\gamma (T)t})$ thus providing a “mixed dark matter” scenario. Relaxation of the ALP condensate, thermalization, decoherence, and entropy production occur on similar timescales. An explicit example with ALP-photon coupling, valid post recombination yields a relaxation rate $\gamma (T)$ with a substantial enhancement from thermal emission and absorption. A misaligned condensate is decaying at least since recombination and on the same timescale thermalizing with the cosmic microwave background (CMB). Possible consequences for birefringence of the CMB and ALP contribution to the effective number of ultrarelativistic species and galaxy formation are discussed.

In the procedure of constraining the cosmological parameters with the observational Hubble data (OHD), the combination of masked autoregressive flow (MAF) and denoising autoencoder (DAE_ can perform with good result. The above combination extracts the features from OHD with DAE, and estimates the posterior distribution of $H_0$, ${\mathrm{\Omega }}_m$, ${\mathrm{\Omega }}_{\mathrm{\Lambda }}$ with MAF. We ask whether we can find a better tool to compress large data in order to gain better results while constraining the cosmological parameters. Information maximizing neural networks (IMNN), a kind of simulation-based machine learning technique, was proposed at an earlier time. In a series of numerical examples, the results show that IMNN can find optimal, nonlinear summaries robustly. In this work, we mainly compare the dimensionality reduction capabilities of IMNN and DAE. We use IMNN and DAE to compress the data into different dimensions and set different learning rates for MAF to calculate the posterior. Meanwhile, the training data and mock OHD are generated with a simple Gaussian likelihood, the spatially flat $\mathrm{\Lambda }\mathrm{CDM}$ model and the real OHD data. To avoid the complex calculation in comparing the posterior directly, we set different criteria to compare IMNN and DAE.

We numerically examine the exterior solution of spherically symmetric and static configuration in scalar-tensor theories by using the nonminimally coupled scalar field with zero potential as our sample model. Our main purpose in this work is to fit the resulting data of the numerical solutions in the interested region by seeking for approximate analytical expressions which are weakly dependent of the parameters of a model, such as the nonminimal coupling constant in the present case. To this end, we determine the main forms of the mass and the metric functions in terms of the scalar field and their surface values. Then, we provide a function for the scalar field that contains only the mass and the radius of the configuration together with the surface and the asymptotic values of the scalar field. Therefore, we show that the exterior solution can be expressed in a form which does not depend on the parameters of a chosen model up to an order of accuracy around ${10}^{-5}$.

Gravitationally bound clumps of dark matter axions in the form of “miniclusters” or even denser “axion stars” can generate strong radio signals through axion-photon conversion when encountering highly magnetized neutron star magnetospheres. We systematically study encounters of axion clumps with neutron stars and characterize the axion infall, conversion and the subsequent propagation of the photons. We show that the high density and low escape velocity of the axion clumps lead to strong, narrow, and temporally characteristic transient radio lines with an expected duration varying from seconds to months. Our work comprises the first end-to-end modeling pipeline capable of characterizing the radio signal generated during these transient encounters, quantifying the typical brightness, anisotropy, spectral width, and temporal evolution of the radio flux. The methods developed here may prove essential in developing dedicated radio searches for transient radio lines arising from miniclusters and axion stars.

We generalize existing constraints on primordial black holes to dark objects with extended sizes using the aLIGO design sensitivity. We show that LIGO is sensitive to dark objects with radius $O(10-{10}^3\mathrm{km})$ if they make up more than $\sim O({10}^{-2}-{10}^{-3})$ of dark matter.

Soliton in the hostile turbulent wave dark matter ($\mathrm{\Psi }\mathrm{DM}$) halo of a galaxy agitates with various kinds of excitation, and the soliton even breathes heavily under great stress. A theory of collective excitation for a $\mathrm{\Psi }\mathrm{DM}$ soliton is presented. The collective excitation has different degrees of coupling to negative energy modes, where lower-order excitation generally necessitates more negative energy coupling. A constrained variational principle is developed to assess the frequencies and mode structures of small-amplitude perturbations. The predicted frequencies are in good agreement with those found in simulations. Soliton breathing at amplitudes on the verge of breakup is also a highlight of this work. Even in this extreme nonlinear regime, the wave function perturbation amplitudes are moderate. The simulation data show a stable oscillation with frequency weakly dependent on the oscillation amplitude and hint at a self-consistent quasilinear model for the wave function that accounts for modifications in the ground-state wave function and the equilibrium density. The mock solution, constructed from the simulation data, can shed light on the dynamics of the large-amplitude breathing soliton and support the quasilinear model, as evidenced by its ability to predict well the nonlinear eigenfrequency shifts and large-amplitude breathing frequency observed in simulations.

Celestial capture of dark matter provides a useful handle for constraining its particulate properties. The capture formalism is sensitive to the phase space distribution of dark matter in the vicinity of the celestial object. This article aims to systematically study the impact of uncertainties and the influence of cosmological simulations on the rate at which dark matter particles are captured inside a variety of celestial objects. Going beyond the framework of the Maxwell-Boltzmann distribution or the standard halo model, we take up pragmatic dark matter velocity distributions motivated by observations or cosmological simulations. Within the limits of the standard halo model, we report a maximum $\sim 20\%$ change in the capture rate. This number can go up to $\sim 200\%$ if dark matter particles within the galactic halo are favored to have an empirical velocity distribution profile when well-resolved and sophisticated cosmological simulations are employed to extract their parametric values.

We generalize the vacuum-Unruh effect to arbitrary excited states in the Fock space and find that the Unruh mode at the horizon induces coherent excitation on the canonical background ensemble measured by an accelerated observer. When there is only one type of Unruh mode in the system, for example, the ones outgoing from a black hole horizon, the mapping from an arbitrary density matrix on the maximal foliation to a vector space spanned by the pseudothermal density matrix on the partitioned spacetime wedge is one-to-one. Hence, we propose that the information of the particles that is inside a collapsing shell; thus, inside the asymptotic black hole horizon is at least partially retrievable by measuring the deviation of the Hawking radiation from the blackbody radiation spectrum. This work shows that the long-standing black hole information confusion might come from overlooking the possibility that the information could be preserved much better than we have expected in a seemingly nonunitary process when the partitions of the system are strongly entangled.

The European Spallation Source (ESS), currently under construction in Sweden, will provide an intense pulsed neutrino flux allowing for high-statistics measurements of coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) with advanced nuclear recoil detectors. In this paper, we investigate in detail the possibility of constraining nonstandard neutrino interactions (NSIs) through such precision $\mathrm{CE}\nu \mathrm{NS}$ measurements at the ESS, considering the different proposed detection technologies, either alone or in combination. We first study the sensitivity to neutral-current NSI parameters that each detector can reach in 3 years of data taking. We then show that operating two detectors simultaneously can significantly improve the expected sensitivity on flavor-diagonal NSI parameters. Combining the results of two detectors turns out to be even more useful when two NSI parameters are assumed to be nonvanishing at a time. In this case, suitably chosen detector combinations can reduce the degeneracies between some pairs of NSI parameters to a small region of the parameter space.

We demonstrate the use of symbolic regression in deriving analytical formulas, which are needed at various stages of a typical experimental analysis in collider phenomenology. As a first application, we consider kinematic variables like the stransverse mass, $M_{T2}$, which are defined algorithmically through an optimization procedure and not in terms of an analytical formula. We then train a symbolic regression and obtain the correct analytical expressions for all known special cases of $M_{T2}$ in the literature. As a second application, we reproduce the correct analytical expression for a next-to-leading order (NLO) kinematic distribution from data, which is simulated with a NLO event generator. Finally, we derive analytical approximations for the NLO kinematic distributions after detector simulation, for which no known analytical formulas currently exist.