Considerations of high energies in quantum field theories on smooth manifolds have led to generalized uncertainty principles and the possibility of a physical minimal length in quantum gravitational scenarios. In these models, the minimal length would be a physical limit, not just a mathematical tool, and should be Lorentz invariant. In this paper, we study two-qubit communication and entanglement harvesting in a field subject to a covariant bandlimit (minimum length) and present the changes induced by this bandlimit. We find the bandlimit introduces nonlocality and acausal communication in a manner unlike noncovariant bandlimits or other quantum optical approximations. We also observe that this covariant bandlimit introduces uncertainties in time and temporal ordering with the unusual behavior attributed to the behavior of virtual particles being modified by the covariant cutoff.

Current searches for gravitational waves (GWs) from black hole binaries using the LIGO and Virgo observatories are limited to analytical models for systems with black hole spins aligned (or antialigned) with the orbital angular momentum of the binary. Detecting black hole binaries with precessing spins (spins not aligned or antialigned with the orbital angular momentum) is crucial for gaining unique astrophysical insights into the formation of these sources. Therefore, it is essential to develop a search strategy capable of identifying compact binaries with precessing spins. Aligned-spin waveform models are inadequate for detecting compact binaries with high precessing spins. While several efforts have been made to construct template banks for detecting precessing binaries using matched filtering, this approach requires many templates to cover the entire search parameter space, significantly increasing the computational cost. This work explores the detection of GW signals from binary black holes (BBH) with both aligned and precessing spins using a convolutional neural network (CNN). We frame the detection of GW signals from aligned or precessing BBH systems as a hierarchical binary classification problem. The first CNN model classifies strain data as either pure noise or noisy signals (GWs from BBH). A second CNN model then classifies the detected noisy signal data as originating from either precessing or nonprecessing (aligned/antialigned) systems. Using simulated data, the trained classifier distinguishes between noise and noisy GW signals with more than 99% accuracy. The second classifier further differentiates between aligned and highly precessing signals with around 95% accuracy. We extended our analysis to a multidetector framework by performing a coincident test. Additionally, we tested the performance of our trained architecture on data from the first three observation runs (O1, O2, and O3) of LIGO and Virgo to identify detected BBH events as either aligned or precessing.

Gravitational waves from inspiraling binary neutron stars provide unique access to ultradense nuclear matter and offer the ability to constrain the currently unknown neutron star equation-of-state through tidal measurements. This, however, requires the availability of accurate and efficient tidal waveform models. In this paper we present phenomgsf, a new phenomenological tidal phase model for the inspiral of neutron stars in the frequency domain, which captures the gravitational self-force informed tidal contributions of the time-domain effective-one-body model teobresums. phenomgsf is highly faithful and computationally efficient, and by choosing a modular approach, it can be used in conjunction with any frequency-domain binary black hole waveform model to generate the complete phase for a binary neutron star inspiral. phenomgsf is valid for neutron star binaries with unequal masses and mass ratios between 1 and 3, and dimensionless tidal deformabilities up to 5000. Furthermore, phenomgsf does not assume universal relations or parametrized equations of state, hence allowing for exotic matter analyses and beyond standard model physics investigations. We demonstrate the efficacy and accuracy of our model through comparisons against teobresums, numerical relativity waveforms and full Bayesian inference, including a reanalysis of the binary neutron star observation GW170817.

We study the effect of adding an interaction in the $G_3$ term of Horndeski theory, where the propagation of gravitational waves is not modified. We derive the background and perturbation equations of motion from the action. We also derive the no-ghost and Laplacian instability conditions for tensor modes and scalar mode propagation. Then we study the evolution of the matter perturbation in the quasistatic approximation. We find that the gravitational couplings to the baryonic and cold dark matter over density are modified in this theory. We introduce a concrete model of the free function in the theory and study the background and linear perturbation dynamics. We then use the genetic algorithm to test the model. We compare the $H(z)$ function of the model and the $H(z)$ curve predicted by the genetic algorithm, using the $H(z)$ data. For the perturbation sector, we compute the $f{\sigma }_8$ observable for the model and compare it with the predicted function from the genetic algorithm from the $f{\sigma }_8$ data.

The circular polarization of the stochastic gravitational wave background (SGWB) is a key observable for characterizing the origin of the signal detected by Pulsar Timing Array (PTA) collaborations. Both the astrophysical and the cosmological SGWB can have a sizeable amount of circular polarization, due to Poisson fluctuations in the source properties for the former, and to parity violating processes in the early universe for the latter. Its measurement is challenging since PTA are blind to the circular polarization monopole, forcing us to turn to anisotropies for detection. We study the sensitivity of current and future PTA datasets to circular polarization anisotropies, focusing on realistic modelling of intrinsic and kinematic anisotropies for astrophysical and cosmological scenarios respectively. Our results indicate that the expected level of circular polarization for the astrophysical SGWB should be within the reach of near future datasets, while for cosmological SGWB circular polarization is a viable target for more advanced SKA-type experiments.

We describe quantization schemes for scalar field cosmology in the metric variables with fundamental discreteness imposed with a lattice. The variables chosen for quantization determine the lattice, and each lattice produces distinct effective equations derived from semiclassical states. We show that requiring a bounce at the Planck density uniquely selects the volume lattice and gives the same effective Friedmann equation as that obtained in loop quantum cosmology. We also present conditions for the validity of the effective equations.

We investigate the potential of gravitational-wave background searches to constrain cosmic histories characterized by a stiff equation of state, preceded by a period of matter domination. Such a scenario leads to a characteristic peak in the primordial gravitational-wave spectrum originating from cosmological inflation. Assuming instant transitions between distinct epochs, which allows for an analytical treatment of the gravitational-wave spectrum, we perform a Bayesian inference analysis to derive constraints from the first three observing runs of the LIGO-Virgo-KAGRA Collaboration. Additionally, we consider a smooth transition, employing an axionlike particle physics model, and highlight the differences compared to the instant transition approximation. Finally, we forecast detection prospects for such a cosmic history through future gravitational-wave experiments.

We study the gravitational wave (GW) emission of sources perturbed by periodic dynamical forces that do not cause secular evolution in the orbital elements. We construct a corresponding post-Newtonian waveform model and provide estimates for the detectability of the resulting GW phase perturbations, for both space-based and future ground-based detectors. We validate our results by performing a set of Bayesian parameter recovery experiments with post-Newtonian waveforms. We find that, in stark contrast to the more commonly studied secular dephasing, periodic phase perturbations do not suffer from degeneracies with any of the tested vacuum binary parameters. We discuss the applications of our findings to a range of possible astrophysical scenarios, finding that such periodic perturbations may be detectable for massive black hole binaries embedded in circumbinary disks and extreme mass-ratio inspirals in accretion disks, as well as stellar-mass compact objects perturbed by tidal fields. We argue that modeling conservative suborbital dynamics opens up a promising new avenue to detect environmental effects in binary sources of GWs that should be included in state-of-the-art waveform templates.

In this work, we study the impact of anisotropy on slowly rotating neutron stars by extending the Hartle–Thorne formalism in general relativity to include anisotropy in pressure up to second order in the angular velocity. We assess the presence of anisotropy within the star by employing a quasi-local relationship. Our results show that the ratio between the gravitational mass of the fastest anisotropic rotating configurations and the corresponding nonrotating ones ranges from 1.12 to 1.25, consistent with recent findings. We develop universal relations for the moment of inertia, binding energy, and quadrupole moment of the rotating stars. These relations are tested against various equations of state, which were modeled by a piecewise polytropic function with continuous sound speed.

High-frequency gravitational waves are the subject of rapidly growing interest in the theoretical and experimental community. In this work we calculate the resonant conversion of gravitational waves into photons in the magnetospheres of neutron stars via the inverse Gertsenshtein mechanism. The resonance occurs in regions where the vacuum birefringence effects cancel the classical plasma contribution to the photon dispersion relation, leading to a massless photon in the medium which becomes kinematically matched to the graviton. We set limits on the amplitude of a possible stochastic background of gravitational waves using X-ray and IR flux measurements of neutron stars. Using Chandra (2–8 keV) and NuSTAR (3–79 keV) observations of RX J1856.6-3754, we set strain limits $h_c^{\lim }\simeq {10}^{-26}–{10}^{-24}$ in the frequency range $5\times {10}^{17}\mathrm{Hz}\lesssim f\lesssim 2\times {10}^{19}\mathrm{Hz}$. Our limits are many orders of magnitude stronger than existing constraints from individual neutron stars at the same frequencies. We also use recent JWST observations of the Magnetar 4U $0142+61$ in the range $2.7\times {10}^{13}\mathrm{Hz}\lesssim f\lesssim 5.9\times {10}^{13}\mathrm{Hz}$, setting a limit $h_{\mathrm{c}}^{\lim }\simeq 5\times {10}^{-19}$. These constraints are in complementary frequency ranges to laboratory searches with CAST, OSQAR and ALPS II. We expect these limits to be improved both in reach and breadth with a more exhaustive use of telescope data across the full spectrum of frequencies and targets.

Astrophysical scenarios for the formation and evolution of intermediate-mass black holes (IMBHs) in the mass range ${10}^2{M}_{\odot }\lesssim M\lesssim {10}^6{M}_{\odot }$ remain uncertain, but future ground-based gravitational-wave (GW) interferometers will probe the lower end of the IMBH mass range. We study the detectability of IMBH binary mergers and the measurability of their parameters with next-generation ground-based detector networks consisting of various combinations of Cosmic Explorer (CE) and Einstein Telescope (ET) interferometers. We find that, for binaries with component masses $m_{1,2}\sim 1000M_{\odot }$, an optimal 3-detector network can constrain the masses with errors $\lesssim 0.1\%$ ($\lesssim 1\%$) at $z=0.5$ ($z=2$), and the source redshift can be measured with percent-level accuracy or better at $z\lesssim 2$. The redshift of lighter binaries ($m_{1,2}\lesssim 300M_{\odot }$) can still be measured with $\mathcal{O}(10)\%$ accuracy even at $z=10$. Binaries with $z\lesssim 0.5$ can be localized within $1{\mathrm{deg}}^2$ for $m_{1,2}\lesssim 1000M_{\odot }$, and within $0.1{\mathrm{deg}}^2$ for comparable mass systems. The sky localization is good enough that it may be possible to cross-correlate GW searches with galaxy catalogs and to search for electromagnetic counterparts to IMBH mergers. We also point out that the low-frequency sensitivity of the detectors is crucial for IMBH detection and parameter estimation. It will be interesting to use our results in conjunction with population synthesis codes to constrain astrophysical IMBH formation models.

We revisit the computation of the beta function in the two-dimensional $\mathbb{CP}(1)$ sigma model. We show that in different schemes, different diagrams are responsible for the running, such as momentum-independent tadpoles or even UV-finite bubble diagrams. We also comment on the relation between the beta functions and the energy dependence of scattering amplitudes.

This work is the first, to the best of our knowledge, to study synchrotron radiation (SR) from a massless charged electron based on the quantum theory of radiation using exact solutions of the Dirac equation in a constant magnetic field. The cases of ($2+1$)-dimensional and ($3+1$)-dimensional quantum electrodynamics are considered separately, and the calculation of synchrotron radiation of conduction electrons in single-layer graphene is presented. A comparative analysis of two types of quantum effects in massive and massless theories of synchrotron radiation is carried out. Analytical expressions obtained for the spectral distribution and total radiation power for all the processes are considered. It is shown that the SR of a massless charged electron is a purely quantum process in both $QE{D}_{2+1}$ and $QE{D}_{3+1}$.

Physical systems in real life are inextricably linked to their surroundings and never completely separated from them. Truly closed systems do not exist. The phenomenon of decoherence, which is brought about by the interaction with the environment, removes the relative phase of quantum states in superposition and makes them incoherent. In neutrino physics, decoherence, although extensively studied has only been analyzed thus far exclusively in terms of its dissipative characteristics. While it is true that dissipation, or the exponential suppression, eventually is the main observable effect, the exchange of energy between the medium and the system, is an important factor that has been overlooked up until now. In this work, we introduce this term and analyze its consequences.

Thousands of person years have been invested in searches for new physics (NP), the majority of them motivated by theoretical considerations. Yet, no evidence of beyond the Standard Model physics has been found. This suggests that model-agnostic searches might be an important key to explore NP, and help discover unexpected phenomena which can inspire future theoretical developments. A possible strategy for such searches is identifying asymmetries between data samples that are expected to be symmetric within the Standard Model. We propose exploiting neural networks (NNs) to quickly fit and statistically test the differences between two samples. Our method is based on an earlier work, originally designed for inferring the deviations of an observed dataset from that of a much larger reference dataset. We present a symmetric formalism, generalizing the original one, avoiding fine-tuning of the NN parameters and any constraints on the relative sizes of the samples. Our formalism could be used to detect small symmetry violations, extending the discovery potential of current and future particle physics experiments.

We present a class of supersymmetric (SUSY) GUT models that can explain the apparent discrepancy between the SM predictions and experimental values of muon $g-2$ while providing testable signals for lepton flavor violation in charged lepton decays. Moreover, these models predict LSP neutralino abundance that is compatible with the Planck dark matter bounds. We find that scenarios in the framework of $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$ unification, with additional symmetries to explain fermion masses and neutrino oscillations, provide interesting benchmarks for the search of SUSY by correlating a possible manifestation of it in dark matter, rare lepton decays, and LHC signals.

We explore the irreducible cosmological implications of a singlet real scalar field. Our focus is on theories with an approximate and spontaneously broken ${\mathbb{Z}}_2$ symmetry where quasistable domain walls can form at early times. This seemingly simple framework bears a wealth of phenomenological implications that can be tackled by means of different cosmological and astrophysical probes. We elucidate the connection between domain wall dynamics and the production of dark matter and gravitational waves. In particular, we identify three main benchmark scenarios. The gravitational wave signal observed by pulsar timing arrays can be generated by the domain walls if the mass of the singlet is $m_s\sim \mathrm{PeV}$. For lower masses, but with $m_s\gtrsim 10\mathrm{GeV}$, scalars produced in the annihilation of the domain walls can be dark matter with a distinctive feature in their power spectrum. Finally, the thermal bath provides an unavoidable source of unstable scalars via the freeze-in mechanism whose subsequent decays can be tested by their imprints on cosmological and terrestrial observables.

In this paper we compute the next-to-leading order (NLO) QCD corrections for the inclusive nonleptonic decay rates of $B$ hadrons at subleading power of the heavy quark expansion. In particular, we discuss the coefficient of the chromomagnetic moment parameter ${\mu }_G$, which has a large uncertainty at leading order due to its dependence on the renormalization scale. We find that the renormalization-scale dependence of this coefficient is significantly reduced, thereby reducing the theoretical uncertainty of the coefficient and, consequently, the rates. The sign of the coefficient becomes stable, and we estimate that the NLO corrections will increase the decay rates by around 2%.

We extract the leading Fock-state light front wave functions of heavy flavor-asymmetric pseudoscalar mesons $D$, $B$, and $B_c$ from their Bethe-Salpeter wave functions, based on the Dyson-Schwinger equations approach. We then study their leading-twist parton distribution amplitudes, generalized parton distribution functions, and transverse momentum-dependent parton distributions. The spatial distributions of the quark and antiquark on the transverse plane are presented, along with their charge and energy distributions on the light front. We find that in the considered mesons, the heavier quarks carry most of the longitudinal momentum fraction, resulting in narrow $x$ distributions, while the lighter quarks play an active role in shaping the transverse distributions in both spatial and momentum space, exhibiting a duality that embodies characteristics of both light mesons and heavy quarkonium.