We demonstrate some shortcomings of “fixing the equations,” an increasingly popular remedy for time evolution problems of effective field theories (EFTs). We compare the EFTs and their “fixed” versions to the UV theories from which they can be derived in two cases: K-essence and nonlinear Proca theory. We find that when an EFT breaks down due to loss of hyperbolicity, fixing does not approximate the UV theory well if the UV solution does not quickly settle down to vacuum. We argue that this can be related to the EFT approximation itself becoming invalid, which cannot be rectified by fixing.

Light dark matter (DM) in the GeV ballpark faces weaker constraint from direct detection experiments. If such DM also has sufficient self-interactions due to a light mediator, it can alleviate the small-scale problems of the cold dark matter (CDM) paradigm while being consistent with the latter at large scales, as suggested by astrophysical observations. However, generating the correct thermal relic for such light DM is challenging. While GeV scale CDM typically leads to thermal overproduction due to the absence of sufficient annihilation channels, self-interacting dark matter (SIDM) typically has an under-abundant thermal relic due to its large annihilation rates into mediator particles. In this Letter, we propose a minimal realization of GeV scale SIDM with correct thermal relic, where one of the three singlet fermions, responsible for seesaw origin of light neutrino masses, assists in generating correct SIDM relic density via freeze-out. The setup thereby encompasses astrophysical as well as cosmological aspects of light DM while simultaneously providing a solution to the origin of light neutrino mass. Because of such a connection to several frontiers, there exist exciting discovery prospects in terms of direct and indirect search of DM, laboratory and cosmology based dark photon signatures and effective light neutrino mass.

We present an innovative approach to the linearly polarized gluons confined inside the unpolarized nucleon in lepton-nucleon scattering. Our method analyzes the correlation of energy flows at azimuthal separations $\varphi$. The interference of the spinning gluon with both positive and negative helicities translates into a $\cos (2\varphi )$ asymmetry imprinted on the detector. Unlike the conventional transverse momentum dependent probes, the $\cos (2\varphi )$ asymmetry in this approach is preserved by rotational symmetry, holds to all orders, and is free of radiation contamination and is thus expected to provide the exquisite signature of the nucleon linearly polarized gluons.

The electric dipole moment (EDM) of elementary particles, arising from flavor-diagonal $CP$ violation, serves as a powerful probe for new physics beyond the Standard Model and holds the potential to provide novel insights in unraveling the puzzle of the matter-dominated Universe. Hyperon EDM is a largely unexplored territory. In this paper, we present a comprehensive angular analysis that focuses on entangled hyperon-antihyperon pairs in $J/\psi$ decays for the indirect extraction of hyperon EDM. The statistical sensitivities are investigated for BESIII and the proposed Super Tau-Charm Facility (STCF). Leveraging the statistics from the BESIII experiment, the estimated sensitivity for $\mathrm{\Lambda }$ EDM can reach an impressive level of ${10}^{-19}e\mathrm{cm}$, achieving a 3-orders-of-magnitude improvement over the only existing measurement in a fixed-target experiment at Fermilab with similar statistics. The estimated sensitivities for the ${\mathrm{\Sigma }}^{+}$, ${\mathrm{\Xi }}^{-}$, and ${\mathrm{\Xi }}^0$ hyperons at the same level of ${10}^{-19}e\mathrm{cm}$ will mark the first-ever achievement and the latter two will be the first exploration of hyperons with two strange valence quarks. The EDM measurements for hyperons conducted at the BESIII experiment will be a significant milestone and serve as a litmus test for new physics such as supersymmetry and the left-right symmetrical model. Furthermore, at the STCF experiment, the sensitivity of hyperon EDM measurements can be further enhanced by 2 orders of magnitude. Additionally, this angular analysis enables the determination of $CP$ violation in hyperon decays, the effective weak mixing angle, and beam polarization.

Sign and magnitude of the thermodynamic curvature provides empirical information about the nature of microstructures of a general thermodynamic system. For charged black holes in anti–de Sitter (AdS), thermodynamic curvature is positive for large charge or chemical potential, and diverges for extremal black holes, indicating strongly repulsive nature. We compute the thermodynamic curvature at low temperatures, for charged black holes with ${\mathrm{AdS}}_2$ near horizon geometry, and containing a zero temperature horizon radius $r_h$, in a spacetime which asymptotically approaches ${\mathrm{AdS}}_D$ (for $D>3$). In the semiclassical analysis at low temperatures, the curvature shows a novel crossover from negative to positive side, indicating the shift from attraction to repulsion dominated regime near $T=0$, before diverging as $1/(\gamma T)$, where $\gamma$ is the coefficient of leading low temperature correction to entropy. Accounting for quantum fluctuations, the curvature computed in the canonical ensemble is positive, whereas the one in the grand canonical ensemble, shows a crossover from negative to positive side in the Schwarzian region. Moreover, the divergence of curvature at $T=0$ is cured irrespective of the ensemble used, resulting in a universal constant, inversely related to the number of symmetry generators of vacuum ${\mathrm{AdS}}_2$.

Within the framework of holographic duality, conditional mutual information (CMI) is often understood as a correlation between “region pairs” and is closely related to the concept of partial entanglement entropy (PEE). The main theme of this paper is to try to understand the rigorous physical meaning of such a region-pair correlation. This relies on the idea of holographic bit threads and the recently developed thread-state correspondence. In a sense, this effort also prompted us to give a definition of PEE based on the density matrices of the holographic distilled states. Specifically, drawing from experience with the locking multiflow configuration, we first provide a bipartite entanglement explanation for the $\mathrm{PEE}=\mathrm{CMI}$ scheme, but it leads to difficulties in characterizing the entanglement entropy of disconnected regions. We then introduce multipartite entanglement through the generalized $n$-thread/perfect tensor state correspondence to solve this problem and explain the coincidence between CMI and tripartite information in the holographic quantum systems.

We study $d$-dimensional scalar field theory in the local potential approximation of the functional renormalization group. Sturm-Liouville methods allow the eigenoperator equation to be cast as a Schrödinger-type equation. Combining solutions in the large field limit with the Wentzel-Kramers-Brillouin approximation, we solve analytically for the scaling dimension $d_n$ of high dimension potential-type operators ${\mathcal{O}}_n(\phi )$ around a nontrivial fixed point. We find that $d_n=n(d-d_{\phi })$ to leading order in $n$ as $n\to \infty$, where $d_{\phi }=\frac{1}{2}(d-2+\eta )$ is the scaling dimension of the field $\phi$ and determine the power-law growth of the subleading correction. For $O(N)$ invariant scalar field theory, the scaling dimension is just double this, for all fixed $N\ge 0$ and additionally for $N=-2,-4,\dots$. These results are universal, independent of the choice of cutoff function which we keep general throughout, subject only to some weak constraints.

Recently, it was shown that for a dynamical black hole in any higher-derivative theory of gravity, one could construct a spatial entropy current, characterizing the in/outflow of entropy at every point on the horizon, as long as the dynamics of the amplitude is small enough. However, the construction is very much dependent on how we choose the spatial slicing of the horizon along its null generators. In this paper, we show that although both the entropy density and the spatial entropy current change nontrivially under a reparametrization of the null generator, the net entropy production, (which is given by the “time” derivative of entropy density plus the divergence of the spatial current) is invariant. We have explicitly verified this claim for the particular case of dynamical black holes Einstein-Gauss-Bonnet theory.

The measurability of multiple quasinormal (QN) modes, including overtones and higher harmonics, with the Laser Interferometer Space Antenna is investigated by computing the gravitational wave (GW) signal induced by an intermediate or extreme mass ratio merger involving a supermassive black hole (SMBH). We confirm that the ringdown of rapidly spinning black holes are long-lived, and higher harmonics of the ringdown are significantly excited for mergers of small mass ratios. We investigate the measurability and separability of the QN modes for such mergers and demonstrate that the observation of GWs from rapidly rotating SMBHs has an advantage for detecting superposed QN modes and testing the no-hair theorem of black holes.

The bimetric theory of gravity is an extension of general relativity that describes a massive spin-2 particle in addition to the standard massless graviton. The theory is based on two dynamical metric tensors with their interactions constrained by requiring the absence of the so-called “Boulware-Deser ghost.” It has been realized that the quantum interactions of matter fields with gravity are bound to generate modifications to the standard Einstein-Hilbert action such as quadratic curvature terms. Such a quadratic Ricci scalar term is present in the so-called Starobinsky model, which has been proven to be rather robust in its inflationary predictions. In the present article, we study a generalization of the Starobinsky model within the bimetric theory and find that its inflationary behavior stays intact while keeping all consistency requirements of the bimetric framework. The interpretation of the massive spin-2 particle as dark matter remains a viable scenario, as in standard bigravity.

Modified gravity theories such as Einstein scalar Gauss Bonnet contain higher-derivative terms in the spacetime curvature in their action, which results in modifications to the Hamiltonian and momentum constraints of the theory. In principle, such modifications may affect the principal part of the operator in the resulting elliptic equations, and so further complicate the already highly nonlinear, coupled constraints that apply to the initial data in numerical relativity simulations of curved spacetimes. However, since these are effective field theories, we expect the additional curvature terms to be small, which motivates treating them simply as an additional source in the constraints, and iterating to find a solution to the full problem. In this work we implement and test a modification to the CTT/CTTK methods of solving the constraints for the case of the most general four derivative, parity invariant scalar-tensor theory, and show that solutions can be found in both asymptotically flat/black hole and periodic/cosmological spacetimes, even up to couplings of order unity in the theory. Such methods will allow for numerical investigations of a much broader class of initial data than has previously been possible in these theories, and should be straightforward to extend to similar models in the Horndeski class.

We report on critical phenomena in the gravitational collapse of the electromagnetic field in axisymmetry using cylindrical coordinates. We perform detailed numerical simulations of four families of dipole and quadrupole initial data fine-tuned to the onset of black hole formation. It has been previously observed that families that bifurcate into two on-axis critical solutions exhibit distinct growth characteristics from those that collapse at the center of symmetry. In contrast, our results indicate similar growth characteristics and periodicity across all families of initial data, including those examined in earlier works. More precisely, for all families investigated, we observe power-law scaling for the maximum of the electromagnetic field invariant ($\max |F_{\mu \nu }{F}^{\mu \nu }|\sim |p-p^{\star }{|}^{-2\gamma }$) with $\gamma \approx 0.149(9)$. We find evidence of approximate discrete self-similarity in near-critical time evolutions with a log-scale echoing period of $\mathrm{\Delta }\approx 0.62(8)$ across all families of initial data. Our methodology, while reproducing the results of prior studies up to a point, provides new insights into the later stages of critical searches and we propose a mechanism to explain the observed differences between our work and the previous calculations.

We consider the gravitational collapse of collisionless matter seeded by three crossed sine waves with various amplitudes and also in the presence of a linear external tidal field. We explore two theoretical methods that are more efficient than the standard Lagrangian perturbation theory (LPT) for resolving shell crossings, the crossing of particle trajectories. One of the methods completes the truncated LPT series for the displacement field far into the UV regime, thereby exponentially accelerating its convergence while at the same time removing pathological behavior of LPT observed in void regions. The other method exploits normal-form techniques known from catastrophe theory, which amounts here to replacing the sine-wave initial data by its second-order Taylor expansion in space at the shell-crossing location. This replacement leads to a speed-up in determining the displacement field by several orders of magnitudes, while still achieving permille-level accuracy in the prediction of the shell-crossing time. The two methods can be used independently, but the overall best performance is achieved when combining them. Lastly, we find accurate formulas for the nonlinear density and for the triaxial evolution of the fluid in the fundamental coordinate system, as well as report a newly established correspondence between perfectly symmetric sine-wave collapse and spherical collapse.

Superradiantly unstable ultralight particles around a classical rotating black hole (BH) can form an exponentially growing bosonic cloud, which have been shown to provide an astrophysical probe to detect ultralight particles and constrain their mass. However, the classical BH picture has been questioned, and different theoretical alternatives have been proposed. Exotic compact objects (ECOs) are horizonless alternatives to BHs featuring a reflective surface (with a reflectivity $\mathcal{K}$) in place of the event horizon. In this work, we study superradiant instabilities around ECOs, particularly focusing on the influence of the boundary reflection. We calculate the growth rate of superradiant instabilities around ECOs and show that the result can be related to the BH case by a correction factor $g_{\mathcal{K}}$, for which we find an explicit analytical expression and a clear physical interpretation. Additionally, we consider the time evolution of superradiant instabilities and find that the boundary reflection can either shorten or prolong the growth timescale. As a result, the boundary reflection alters the superradiance exclusion region on the Regge plane, potentially affecting constraints on the mass of ultralight particles. For a mildly reflective surface ($|\mathcal{K}|\lesssim 0.5$), the exclusion region is not substantially changed, while significant effects from the boundary reflection can occur for an extreme reflectivity ($|\mathcal{K}|\gtrsim 0.9$).

The annihilation of TeV-scale leptophilic dark matter into electron-positron pairs (hereafter $e^{+}{e}^{-}$) will produce a sharp cutoff in the local cosmic-ray $e^{+}{e}^{-}$ spectrum at an energy matching the dark matter mass. At these high energies, $e^{+}{e}^{-}$ cool quickly due to synchrotron interactions with magnetic fields and inverse-Compton scattering with the interstellar radiation field. These energy losses are typically modeled as a continuous process. However, inverse-Compton scattering is a stochastic energy-loss process where interactions are rare but catastrophic. We show that when inverse-Compton scattering is modeled as a stochastic process, the expected $e^{+}{e}^{-}$ flux from dark matter annihilation is about a factor of $\sim 2$ larger near the dark matter mass than in the continuous model. This greatly enhances the detectability of heavy dark matter annihilating to $e^{+}{e}^{-}$ final states.

Protoneutron stars formed during core-collapse supernovae are hot and dense environments that contain a sizable population of muons. If these interact with new long-lived particles with masses up to roughly 100 MeV, the latter can be produced and escape from the stellar plasma, causing an excessive energy loss constrained by observations of SN 1987A. In this article we calculate the emission of light dark fermions that are coupled to leptons via a new massive vector boson, and determine the resulting constraints on the general parameter space. We apply these limits to the gauged $L_{\mu }-L_{\tau }$ model with dark fermions, and show that the SN 1987A constraints exclude a significant portion of the parameter space targeted by future experiments. We also extend our analysis to generic effective four-fermion operators that couple dark fermions to muons, electrons, or neutrinos. We find that SN 1987A cooling probes a new physics scale up to $\sim 7\mathrm{TeV}$, which is an order of magnitude larger than current bounds from laboratory experiments.

Pulsar timing arrays (PTAs) have recently found evidence for a nanohertz-frequency stochastic gravitational-wave background (SGWB). Constraining its spectral characteristics will reveal its origins. In order to achieve this, we must understand how data and modeling conditions in each pulsar influence the precision and accuracy of SGWB spectral recovery. These goals typically require many Bayesian analyses on real data sets and large-scale simulations that are slow and computationally taxing. To combat this, we have developed several new rapid approaches that instead operate on intermediate SGWB analysis products. These techniques refit SGWB spectral models to previously-computed Bayesian posterior estimates of the timing power spectra. We test our new techniques on simulated PTA data sets and the NANOGrav 12.5-year data set, where in the latter our refit posterior achieves a Hellinger distance—bounded between 0 for identical distributions and 1 for zero overlap—from the current full production-level pipeline that is $\lesssim 0.1$. Our techniques are $\sim {10}^2–{10}^4$ times faster than the production-level likelihood, and scale much more favorably (sub-linearly) as a PTA is expanded with new pulsars or observations. Our techniques also allow us to demonstrate conclusively that SGWB spectral characterization in PTA data sets is driven by the longest-timed pulsars and the best-measured power spectral densities, which is not necessarily the case for SGWB detection that is predicated on correlating many pulsars. Indeed, the common-process spectral properties found in the NANOGrav 12.5-year data set are given by analyzing only the $\sim 14$ longest-timed pulsars out of the full 45 pulsar array, and we find that the “shallowing” of the common-process power-law model occurs when gravitational-wave frequencies higher than $\sim 50$ nanohertz are included. The implementation of our techniques is openly available as a software suite to allow fast and flexible PTA SGWB spectral characterization and model selection.

The Laser Interferometer Space Antenna (LISA) is a planned space-based gravitational wave telescope with the goal of measuring gravitational waves in the millihertz frequency band, which is dominated by millions of Galactic binaries. While some of these binaries produce signals that are loud enough to stand out and be extracted, most of them blur into a confusion foreground. Current methods for analyzing the full frequency band recorded by LISA to extract as many Galactic binaries as possible and to obtain Bayesian posterior distributions for each of the signals are computationally expensive. We introduce a new approach to accelerate the extraction of the best fitting solutions for Galactic binaries across the entire frequency band from data with multiple overlapping signals. Furthermore, we use these best fitting solutions to omit the burn-in stage of a Markov chain Monte Carlo method and to take full advantage of graphics processing unit (GPU)-accelerated signal simulation, allowing us to compute posterior distributions in 2 s per signal on a laptop-grade GPU.

Third generation gravitational-wave (GW) detectors are expected to detect a large number of binary black holes (BBHs) to large redshifts, opening up an independent probe of the large scale structure using their clustering. This probe will be complementary to the probes using galaxy clustering—GW events could be observed up to very large redshifts ($z\sim 10$) although the source localization will be much poorer at large distances ($\sim \mathrm{tens}$ of square degrees). We explore the possibility of probing the large scale structure from the spatial distribution of the observed BBH population, using their two-point (auto)correlation function. We find that we can estimate the bias factor of the population of BBHs (up to $z\sim 0.7$) with a few years of observations with these detectors. Our method relies solely on the source-location posteriors obtained from the GW events and does not require any information from electromagnetic observations. This will help in identifying the types of galaxies that host the BBH population, thus shedding light on their origins.