Many inflationary theories predict a non-Gaussian spectrum of primordial tensor perturbations, sourced from nonstandard vacuum fluctuations, modified general relativity, or new particles such as gauge fields. Several such models also predict a chiral spectrum in which one polarization state dominates. In this work, we place constraints on the non-Gaussianity and parity properties of primordial gravitational waves utilizing the Planck PR4 temperature and polarization data set. Using recently developed quasioptimal bispectrum estimators, we compute binned parity-even and parity-odd bispectra for all combinations of cosmic microwave background (CMB) $T$-, $E$-, and $B$-modes with $2\le \ell <500$, and perform both blind tests, sensitive to arbitrary three-point functions, and targeted analyses of a well-motivated equilateral gravitational-wave template (sourced by gauge fields) with amplitude $f_{\mathrm{NL}}^{ttt}$. This is the first time $B$-modes have been included in primordial non-Gaussianity analyses; they are found to strengthen constraints on the parity-even sector by $\simeq 30\%$ and dominate the parity-odd bounds, without inducing bias. We report no detection of non-Gaussianity (of either parity), with the template amplitude constrained to $f_{\mathrm{NL}}^{ttt}=900\pm 700$ (stable with respect to a number of analysis variations), compared to $1300\pm 1200$ in Planck 2018. The methods applied herein can be reapplied to upcoming CMB data sets such as LiteBIRD, with the inclusion of $B$-modes poised to dramatically improve future bounds on tensor non-Gaussianity.

Extreme mass-ratio inspirals (EMRIs), namely binary systems composed of a massive black hole and a compact stellar-mass object, are anticipated to be among the gravitational wave (GW) sources detected by the Laser Interferometer Space Antenna (LISA). Similarly to compact binary mergers detected by current GW detectors, EMRIs can be used as cosmic rulers to probe the expansion of the Universe. Motivated by tensions in current cosmological observations as well as by alternative models of dark energy, modified gravity theories can affect the propagation of GWs across cosmological distances, with modifications commonly parametrized in terms of two phenomenological parameters, ${\mathrm{\Xi }}_0$ and $n$. In this work, we adopt a Bayesian approach to constrain for the first time parametrized deviations from general relativity using the loudest simulated EMRIs detected by LISA as dark sirens with a simulated galaxy catalog. Assuming all the cosmological parameters except ${\mathrm{\Xi }}_0$ are already tightly constrained, our forecasts show that ${\mathrm{\Xi }}_0$ can be constrained to a few percent level (90% C.I.) with 4 years of LISA observations, unless EMRI detection rates turn out to be closer to current pessimistic expectations. These results quickly degrade if additional cosmological parameters are inferred simultaneously but become more robust with an extended LISA observation period of 10 years. Overall, we find that EMRIs with LISA are better at constraining modified GW propagation than current second-generation ground-based GW detectors, but they will only be comparable to third-generation detectors in the most optimistic scenarios.

The cosmic string contributes to our understanding and revelation of the fundamental structure and evolutionary patterns of the Universe, unifying our knowledge of the cosmos and unveiling new physical laws and phenomena. Therefore, we anticipate the detection of stochastic gravitational wave background (SGWB) signals generated by cosmic strings in space-based detectors. We have analyzed the detection capabilities of individual space-based detectors, LISA and Taiji, as well as the joint space-based detector network, LISA-Taiji, for SGWB signals produced by cosmic strings, taking into account other astronomical noise sources. The results indicate that the LISA-Taiji network exhibits superior capabilities in detecting SGWB signals generated by cosmic strings and can provide strong evidence. The LISA-Taiji network can achieve an uncertainty estimation of $\mathrm{\Delta }G\mu /G\mu <0.5$ for cosmic string tension $G\mu \sim {10}^{-18}$, and can provide evidence for the presence of SGWB signals generated by cosmic strings at $G\mu \ge {10}^{-17}$, and strong evidence at $G\mu \ge {10}^{-16}$. Even in the presence of only SGWB signals, it can achieve a relative uncertainty of $\mathrm{\Delta }G\mu /G\mu <0.5$ for cosmic string tension $G\mu <{10}^{-18}$, and provide strong evidence at $G\mu \ge {10}^{-17}$.

The source of the tension between local Supernova (SN) Ia based Hubble constant measurements and those from the cosmic microwave background or (baryon acoustic oscillation+big bang nucleosynthesis) measurements is one of the most interesting unknowns of modern cosmology. Sample variance forms a key component of the error on the local measurements, and will dominate the error budget in the future as more SNe Ia are observed. Many methods have been proposed to estimate sample variance in many contexts, and we compared results from a number of approximate methods to estimates from $N$-body simulations in a previous paper, confirming that sample variance for the Pantheon SNe Ia sample does not solve the Hubble tension. We now extend this analysis to include the more accurate analytic method based on calculating correlations between the radial peculiar velocities of SNe Ia, comparing this technique with results from numerical simulations. We consider the dependence of these errors on the linear power spectrum and how nonlinear velocities contribute to the error. Using this technique, and matching sample variance errors from more approximate methods, we can define an effective volume for SNe Ia samples, finding that the Pantheon sample is equivalent to a top-hat sphere of radius $\sim 220h^{-1}\mathrm{Mpc}$. We use this link between sample-variance errors to compute $\mathrm{\Delta }{H}_0$ for idealized surveys with particular angular distributions of SNe Ia. For example, a half-sky survey at the Pantheon depth has the potential to suppress the sample variance of $H_0$ to $\sim 0.1\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, a significant improvement compared with the current result. Finally, we consider the strength of large-scale velocity power spectrum required to explain the Hubble tension using sample variance, finding it requires an extreme model well beyond that allowed by other observations.

Gravitational waves are emitted from deep within a core-collapse supernova, which may enable us to determine the mechanism of the explosion from a gravitational-wave detection. Previous studies suggested that it is possible to determine if the explosion mechanism is neutrino-driven or magneto-rotationally powered from the gravitational-wave signal. However, long duration magneto-rotational waveforms, that cover the full explosion phase, were not available during the time of previous studies, and explosions were just assumed to be magneto-rotationally driven if the model was rapidly rotating. Therefore, we perform an updated study using new 3D long-duration magneto-rotational core-collapse supernova waveforms that cover the full explosion phase, injected into noise for the Advanced LIGO, Einstein Telescope and NEMO gravitational-wave detectors. We also include a category for failed explosions in our signal classification results. We then determine the explosion mechanism of the signals using three different methods: Bayesian model selection, dictionary learning, and convolutional neural networks. The three different methods are able to distinguish between neutrino-driven explosions and magneto-rotational explosions, even if the neutrino-driven explosion model is rapidly rotating. However they can only distinguish between the nonexploding and neutrino-driven explosions for signals with a high signal to noise ratio.

It has been known for quite some time that neutron stars (NSs) can play a role in dark matter (DM) detectors due to many unique features of NSs. We apply these (previously developed) ideas to a specific form of the DM when it is represented by a composite object, rather than by a local fundamental field (such as WIMPs). To be more precise we consider the so-called axion quark nuggets (AQN) dark matter model, when the “nonbaryonic” dark matter in fact is made of quarks and gluons which are in dense quark phase (similar to the old idea of the Witten’s strangelets). We argue that the interaction of the AQNs with NSs material may lead to many profound observable effects, which are dramatically different from the conventional picture when DM particles are represented by WIMPs. In particular, we argue that the AQNs may serve as the triggers for the magnetic reconnection to heat the NSs’ surface. This effect may strongly alleviate (or even completely remove) the observed inconsistencies between the predicted and observed surface temperatures for many old NSs. This heating mechanism is always accompanied by the hard x-ray emission, which may serve as an indicator of the proposed mechanism.

The recent analysis on the central compact object in the HESS J1731-347 remnant suggests interestingly small values for its mass and radius. Such an observation favors soft nuclear models that may be challenged by the observation of massive compact stars. In contrast, the recent PREX-II experiment, concerning the neutron skin thickness of ${}^{208}\mathrm{Pb}$, points toward stiff equations of state that favor larger compact star radii. In the present study, we aim to explore the compatibility between stiff hadronic equations of state (favored by PREX-II) and the HESS J1731-347 remnant in the context of hybrid stars. For the construction of hybrid equations of state we use three widely employed Skyrme models combined with the well-known vector MIT bag model. Furthermore we consider two different scenarios concerning the energy density of the bag. In the first case, that of a constant bag parameter, we find that the resulting hybrid equations of state (which satisfy the HESS J1731-347 constraints) are strongly disfavored by the observation of $\sim 2M_{\odot }$ pulsars. However, the introduction of a Gaussian density dependence yields results that are compatible with the conservative $2M_{\odot }$ constraint. The utilization of recent data based on the observation of PSR $\mathrm{J}0030+0451$, PSR J0952-0607, and GW190814 allows for the imposition of additional constraints on the relevant parameters and the stiffness of the two phases. Interestingly, we find that the derived hybrid equations of state do not satisfy the PSR $\mathrm{J}0030+0451$ constraints in $1\sigma$ and only marginally agree with the $2\sigma$ estimations. In addition, we estimate that the observation of massive pulsars, like PSR J0952-0607, in combination with the existence of HESS J1731-347, may require a strong phase transition below $\sim 1.7n_0$. Finally, we show that the supermassive compact object ($2.5-2.67M_{\odot }$) involved in GW190814 could potentially be explained as a rapidly rotating hybrid star.

Ultralight dark matter (ULDM) is one of the most promising DM candidates. Because of the Bose enhancement, we find the annihilation rate of ULDM in the presence of background photon radiation can be greatly enhanced and produce a distinctive reflected electromagnetic wave with an angular frequency equal to the ULDM mass. We propose to utilize such stimulated annihilation to probe the ULDM with the electromagnetic quadratic coupling by emitting a radio beam into space. With a power of a 50 MW emitter, we forecast the sensitivity of quadratic coupling in different local halo models for low-frequency radio telescopes, such as LOFAR, UTR-2, and ngLOBO.

We present a comprehensive analysis of a supersymmetric SO(10) grand unified theory, which is broken to the Standard Model via the breaking of two intermediate symmetries. The spontaneous breaking of the first intermediate symmetry, $B-L$, leads to the generation of cosmic strings and right-handed neutrino masses and further to an observable cosmological background of gravitational waves and generation of light neutrino masses via type-I seesaw mechanism. Supersymmetry breaking manifests as sparticle masses below the $B-L$ breaking but far above the electroweak scale due to proton decay limits. This naturally pushes the $B-L$ breaking scale close to the grand unified theory scale, leading to the formation of metastable cosmic strings, which can provide a gravitational wave spectrum consistent with the recent pulsar timing arrays observation. We perform a detailed analysis of this model using two-loop renormalization group equations, including threshold corrections, to determine the symmetry-breaking scale consistent with the recent pulsar timing arrays signals such as NANOGrav 15-year data and testable by the next-generation limits on proton decay from Hyper-K and JUNO. Simultaneously, we find the regions of the model parameter space that can predict the measured quark and lepton masses and mixing, baryon asymmetry of our Universe, a viable dark matter candidate and can be tested by a combination of neutrinoless double beta decay searches and limits on the sum of neutrinos masses.

Ultraprecise mechanical sensors offer an exciting avenue for testing new physics. While many of these sensors are tailored to detect inertial forces, magnetically levitated (Maglev) systems are particularly interesting, in that they are also sensitive to electromagnetic forces. In this work, we propose the use of magnetically levitated superconductors to detect dark-photon and axion dark matter through their couplings to electromagnetism. Several existing laboratory experiments search for these dark-matter candidates at high frequencies, but few are sensitive to frequencies below 1 kHz (corresponding to dark-matter masses $m_{\mathrm{DM}}\lesssim {10}^{-12}\mathrm{eV}$). As a mechanical resonator, magnetically levitated superconductors are sensitive to lower frequencies, and so can probe parameter space currently unexplored by laboratory experiments. Dark-photon and axion dark matter can source an oscillating magnetic field that drives the motion of a magnetically levitated superconductor. This motion is resonantly enhanced when the dark matter Compton frequency matches the levitated superconductor’s trapping frequency. We outline the necessary modifications to make magnetically levitated superconductors sensitive to dark matter, including specifications for both broadband and resonant schemes. We show that in the $\mathrm{Hz}\lesssim f_{\mathrm{DM}}\lesssim \mathrm{kHz}$ frequency range our technique can achieve the leading sensitivity among laboratory probes of both dark-photon and axion dark matter.

Using a simplified lattice version of the electroweak sector of the standard model, with dynamical fermions excluded, we determine at fixed Weinberg angle the transition line between the confined phase and the Higgs phase, the latter defined as the region where the global center subgroup of the gauge group is spontaneously broken, and “separation of charge” confinement disappears. We then search, via lattice Monte Carlo simulations, for possible neutral vector bosons in the Higgs region, apart from the photon and Z. There are numerical indications of a “light Z” in the lattice data (along with the photon and the Z), but a lack of the expected scaling of the light mass particle excludes any firm conclusions about the physical spectrum.

We update our extraction of parton-to-charged hadron fragmentation functions at next-to-leading order accuracy in quantum chromodynamics (QCD), focusing on the wealth of data collected at the Large Hadron Collider over the past decade. We obtain an accurate description of single-inclusive processes involving unidentified charged hadrons produced at different rapidities and transverse momenta in proton-proton collisions in a wide range of center-of-mass system energies between 0.9 and 13 TeV, along with measurements performed in proton-antiproton collisions at the Tevatron Collider in the past. Next-to-leading order estimates of charged hadron production rates agree best with data when the theoretical factorization scales are selected similar to those optimized for identified pions, kaons, and protons in a recent global QCD analysis.

In boundary conformal field theories, global symmetries can be broken by boundary conditions, generating a homogeneous conformal manifold. We investigate these geometries, showing they have a coset structure, and give fully worked out examples in the case of free fields of spin zero and one-half. These results give a simple illustration of the salient features of conformal manifolds while generalizing to interacting and more intricate setups. Our work was inspired by Drukker et al. [Phys. Rev. Lett. 129, 201603 (2022)].

We study a class of time-dependent backgrounds in string theory which consist of marginal deformations of minimal strings on ${\mathrm{AdS}}_3$. For such backgrounds, we compute the three-point amplitudes and analyze their properties.

We provide the first example of a geometric transition that resolves the Schwarzschild black hole into a smooth microstructure in eleven-dimensional supergravity on a seven-torus. The geometry is indistinguishable from a Schwarzschild black hole dressed with a scalar field in four dimensions, referred to as a Schwarzschild scalarwall. In eleven dimensions, the scalar field arises as moduli of the torus. The resolution occurs at an infinitesimal scale above the horizon, set by the size of the internal torus, where it transitions to a smooth bubbling spacetime supported by M2-brane flux.

The half-Bogomolny-Prasad-Sommerfield (BPS) Wilson line operators in the irreducible representations labeled by the Young diagrams for $\mathcal{N}=4$ $U(N)$ super Yang-Mills theory have gravity dual descriptions. When the number $k$ of boxes of the diagram grows as $k\sim N^2$, the bubbling geometries emerge. We evaluate the spectra of quantum fluctuations on the particular bubbling geometry involving the largest degeneracy from the large $N$ and large $k$ limit of the supersymmetric indices decorated by the Wilson lines. The spectra of excitations over multiparticle $1/8$- and $1/2$-BPS states agree with the numbers of conjugacy classes of general linear group over finite fields while degeneracies of single particle BPS states are given by the general necklace polynomial. The bubbling geometry exhibits a new class of asymptotic degeneracy of states.

A recently introduced functional renormalization group (RG) provides a new tool to explore nonperturbative and covariant RG flows in Lorentzian spacetimes. We apply it for the first time to investigate the ultraviolet limit of quantum gravity. While the RG flow is state dependent, it is possible to evaluate state- and background-independent contributions to the flow. Taking into account only these universal terms, the RG flow exhibits a nontrivial fixed point in the Einstein-Hilbert truncation, providing a mechanism for asymptotic safety in Lorentzian quantum gravity.

We show that the d’Alembertian operator with a possible mass term in the anti–de Sitter (AdS) soliton and more general confining gravity dual backgrounds admits infinitely many different spectra. These can be interpreted as different theories in the infrared and correspond to multitrace deformations of either the Dirichlet or the Neumann theory. We prove that all these fluctuations are normalizable and provide examples of their spectra. Therefore, the AdS soliton can be interpreted as giving a holographic Renormalization Group flow between a universal UV theory at the AdS boundary and these infinitely many possibilities in the IR, obtained by deformations. The massive spectrum of the double trace deformation in ${\mathrm{AdS}}_5$ allows the matching of the large-$N$ glueball masses of lattice ${\mathrm{QCD}}_3$; the ratio of the ground states of the $2^{++}$ and $0^{++}$ channels are in full agreement with the lattice prediction. When considering ${\mathrm{AdS}}_7$ and the four-dimensional pure glue theory, a remarkably general picture emerges, where we can write formulas for the fluctuations that are in agreement with ones from holographic high-energy scattering and from $\mathrm{AdS}/\mathrm{CFT}$ with IR and UV cutoff. We point out that this log branch in the IR in $D$ dimensions can be seen as the usual logarithmic branch of scalar fields saturating the Breitenlohner-Freedman bound in a conformally rescaled metric, with ${\mathrm{AdS}}_{D-1}\times S^1$ asymptotics.

We study $T\overline{T}$-deformed $O(N)$ scalar field theory in two-dimensional spacetime using the functional renormalization group. We derive the $\beta$ functions for the couplings in the system and explore the fixed points. In addition to the Gaussian (trivial) fixed point, we find a nontrivial fixed point at which a new universality class exists. The deformation parameter becomes relevant at the nontrivial fixed point. Therefore, the $T\overline{T}$-deformed scalar field theory in two-dimensional spacetime could be defined as a nonperturbatively renormalizable theory.

We discuss the structure of the mixing among dimension-eight operators in the Standard Model effective field theory relying on the positivity of two-to-two forward scattering amplitudes. We uncover tens of new nontrivial zeros as well as hundreds of terms with definite sign in (a particular basis of) the corresponding anomalous dimension matrix. We highlight that our results are not immediately apparent from the Feynman diagrammatic perspective, nor from on-shell amplitude methods. As a by-product of this work, we provide positivity bounds not previously derived in the literature, as well as explicit values of certain elements of the anomalous dimension matrix that serve as a cross-check of our results.