We analyze the computation of $n$-point correlation functions in de Sitter spacetime, including loop corrections, using the wave function of the universe approach. This method consists of two stages employing distinct Feynman rules. First, one must compute the wave-function coefficients using interactions as vertices. Then, in the second stage, one computes correlation functions using wave-function coefficients as vertices. For massless fields, loop corrections in the first stage are free of infrared (IR) divergences, which leads to the question of how this matches the well-known IR behavior of correlators obtained via other methods. By considering a scalar field with an arbitrary potential, we compute $n$-point correlation functions to first order in the potential but to all orders in loops. We find that although loop integrals in the first stage are indeed IR convergent, the second procedure reintroduces the IR divergence. We discuss how this induces renormalization of the interaction potential such that the final result combining both steps exactly matches the form of $n$-point functions previously calculated with other methods.

In the present article, we propose a very simple parametrization of the Hubble function without parametrizing the dark components of the Universe. One of the novelties of the parametrization is that it may include a wide variety of the cosmological models, such as dark energy (both noninteracting and interacting fluids), modified gravity, cosmological matter creation, and other known scenarios. The model is constrained with the latest astronomical probes from Hubble parameter measurements, three distinct versions of type Ia Supernovae ($\mathrm{Pantheon}+$, DESY5, Union3) and baryon acoustic oscillations from Sloan Digital Sky Survey and Dark Energy Spectroscopic Instrument data releases 1 and 2. Our results suggest a mild deviation from the standard $\mathrm{\Lambda }\mathrm{CDM}$ cosmological model for most of the combined datasets. We also find that our model is thermodynamically consistent and performs well in the model comparison tests.

Under $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$), recent baryon acoustic oscillation (BAO) distance measures from DESI, which favor a low matter density ${\mathrm{\Omega }}_m$, are in moderate $2–3\sigma$ tension with cosmic microwave background (CMB) observations. This tension appears alternately as a preference for the sum of neutrino masses dropping below the $\sum m_{\nu }=0.06\mathrm{eV}$ value required by neutrino oscillation measurements to formally negative values; a discrepant value of ${\mathrm{\Omega }}_m$ at 0.06 eV; or preference for dynamical dark energy beyond $\mathrm{\Lambda }\mathrm{CDM}$. We show that this tension largely arises from the CMB lensing constraints on the calibration of the sound horizon for geometric measurements and relies on the measurement of the reionization optical depth $\tau$ from large-angle CMB polarization to set the lensing amplitude. Dropping these constraints removes the neutrino tension at $\sum m_{\nu }=0.06\mathrm{eV}$ entirely, favoring $\tau =0.091\pm 0.011$ in $\mathrm{\Lambda }\mathrm{CDM}$. Beyond $\mathrm{\Lambda }\mathrm{CDM}$, it brings the preference for $w_0-w_a$ dynamical dark energy to below 95% CL. We explore the freedom in interpreting the low-$\ell$ EE polarization constraint due to analysis choices and reionization modeling beyond the standard step-function assumption and find that this drops the neutrino tension in $\mathrm{\Lambda }\mathrm{CDM}$ to below 95% CL. Alternately, this raising of $\tau$ can also be achieved by the same reduction in large-scale curvature fluctuations that also ameliorates the low-$\ell$ temperature anomaly.

Using lattice field simulations of the Abelian-Higgs model, we characterize the simultaneous emission of (scalar and gauge) particles and gravitational waves (GWs) by local string loops. We use network loops created in a phase transition, and artificial loops formed by either crossing straight-boosted or curved-static infinite strings. Loops decay via both particle and GW emission, on timescales $\mathrm{\Delta }{t}_{\mathrm{dec}}\propto L^p$, where $L$ is the loop length. For particle production, we find $p\simeq 2$ for artificial loops and $p\simeq 1$ for network loops, whilst for GW emission, we find $p\simeq 1$ for all loops. We find that below a critical length, artificial loops decay primarily through particle production, whilst for larger loops GW emission dominates. However, for network loops, which represent more realistic configurations, particle emission always dominates, as supported by our data with length-to-core ratios up to $L/r_{\mathrm{c}}\lesssim 6000$. Our results indicate that the GW background from a local string network should be greatly suppressed compared to estimations that ignore particle emission.

The thermal Sunyaev-Zel’dovich (tSZ) effect, the inverse-Compton scattering of cosmic microwave background (CMB) photons off high-energy electrons, is a powerful probe of hot, ionized gas in the Universe. It is often measured via cross-correlations of CMB data with large-scale structure (LSS) tracers to constrain gas physics and improve cosmological constraints. The largest source of bias to these measurements is the leakage of poorly understood thermal dust emission from star-forming galaxies—the cosmic infrared background (CIB)—into the tSZ maps. This CIB contamination is difficult to clean via multifrequency component separation methods, such as internal linear combination (ILC), due to uncertainty in its spectral energy distribution (SED), which exhibits spatial and line-of-sight variation and decorrelation. Thus, improved ILC-based techniques have been developed to null (“deproject”) both the CIB and its first moment with respect to the emissivity index $\beta$ in order to robustly remove the CIB despite the lack of first-principles knowledge of its SED. While decreasing the bias, such procedures can significantly increase the noise in the resulting ILC maps. In this paper, we develop a data-driven algorithm for determining the optimal CIB SED to deproject when measuring a tSZ-LSS cross-correlation, obviating the need to deproject the first moment in the ILC map used for such a measurement. Our method gives an unbiased cross-correlation with increased signal-to-noise. We demonstrate its efficacy on simulations, finding a 60% improvement in the signal-to-noise ratio for an example tSZ cross-correlation with a halo sample at redshifts $0.8<z<1.8$, as compared to moment deprojection approaches. Though used here for CIB removal in tSZ cross-correlations, our method is broadly applicable to minimizing contaminant leakage in ILC maps. Our code is publicly available in cib-deproj.

https://github.com/kmsurrao/CIB-deproj

Recently, results from the Atacama Cosmology Telescope (ACT) DR6 have shown a preference for isotropic cosmic birefringence, consistent with previous analyses based on Planck and WMAP data. Separately, the Dark Energy Spectroscopic Instrument (DESI) DR2 results suggest that dark energy evolves over cosmic history, pointing to new physics in the late-time universe. In this paper, we propose that domain walls associated with the string axion can naturally explain the isotropic cosmic birefringence, focusing on the case in which the axion starts near a hilltop. Interestingly, to avoid the domain wall problem, these walls must form well after recombination. The predicted rotation angle, $\beta \approx 0.21c_{\gamma }$ degrees (with anomaly coefficient $c_{\gamma }\approx 1$), is in excellent agreement with observations. This scenario can be further tested by probing anisotropic birefringence of photons emitted long after recombination, as well as gravitational waves. Moreover, starting the axion oscillation from a hilltop naturally enhances its abundance via anharmonic effects, thus contributing to the dark energy component. We discuss how this hilltop axion scenario may connect with the DESI results.

Dark matter overdensities around black holes can be searched for by looking at the characteristic imprint they leave on the gravitational waveform of binary black hole mergers. Current theoretical predictions of the density profile of dark matter overdensities are based on highly idealized formation scenarios, in which black holes are assumed to grow adiabatically from an infinitesimal seed to their final mass, compressing dark matter cusps at the center of galactic halos into very dense spikes. These scenarios were suitable for dark matter indirect detection studies, since annihilating dark matter cannot reach very high densities, but they fail to capture the dark matter distribution in the innermost regions where the gravitational wave signal is produced. We present here a more realistic formation scenario where black holes form from the collapse of supermassive stars, and follow the evolution of the dark matter density as the supermassive star grows and collapses to a black hole. We show that in this case dark matter forms shallower mounds, instead of spikes, on scales comparable with the size of the supermassive stars originating them. We discuss the implications for the detectability of these systems.

The detection of gravitational waves (GWs) by LIGO-Virgo and pulsar timing arrays has opened a new window into early Universe cosmology. Yet, the origin of large-scale magnetic fields and the dynamics of the reheating epoch remain poorly understood. In this work, we study the generation of secondary GWs (SGWs) sourced by primordial magnetic fields produced via a Sawtooth-type coupling during reheating with a general background evolution. We show that the reheating equation of state significantly influences the spectral shape and amplitude of the magnetic fields. While a scale-invariant spectrum is typically needed to match observational bounds, this coupling naturally produces a strongly blue-tilted spectrum that remains consistent with current constraints. Crucially, the magnetic field continues to grow during reheating, leading to a GW signal with a broken power-law spectrum and a distinctive blue tilt on superhorizon scales. This SGW signal can fall within the sensitivity of upcoming detectors such as LISA, DECIGO, and BBO. The unique spectral features make this scenario distinguishable from other sources, offering a viable mechanism for cosmic magnetogenesis and a novel probe of the reheating era through GW observations.

Any attempt to understand the ubiquitous nature of the magnetic field in the present Universe seems to lead us toward its primordial origin. For large-scale magnetic fields, however, their strength and length scale may not necessarily originate from a singular primordial mechanism—namely, inflationary magnetogenesis—which has been a popular consideration in the literature. In this paper, we propose a minimal scenario wherein a large-scale magnetic field is generated from the inflationary perturbation without any nonconformal coupling. Due to their origin in the inflationary scalar spectrum, these primordial fields are inherently weak, with their strength suppressed by the small amplitude of scalar fluctuations. We then consider the coupling between this large-scale weak primordial magnetic field and a light axion of mass $<{10}^{-28}\mathrm{eV}$, which is assumed to be frozen in a misaligned state until the photon decoupling. After the decoupling, when the Universe enters the dark ages, the light axion coherently oscillates. By appropriately tuning the axion-photon coupling parameter $\alpha$, we demonstrate that a large-scale magnetic field of sufficient strength can indeed be generated through tachyonic resonance. We further show that the produced magnetic field induces a unique spectrum with multiple peaks of secondary gravitational waves, which the upcoming CMB-S4 can probe through B-mode polarization. The strength can be sufficient enough to violate the Planck bound on the tensor-to-scalar ratio $r\lesssim 0.036$. Such a violation leads to a constraint on $\alpha \lesssim 80$. With this limiting value of the coupling, we find that present-day magnetic field strength could be as high as ${10}^{-10}$ gauss at the megaparsec scale, consistent with observation.

Primordial black holes (PBHs) constitute a compelling dark matter candidate whose gravitational effects could significantly influence early cosmic structure formation. We investigate the impact of PBHs on population III star formation through detailed $N$-body and hydrodynamic simulations, extending beyond previous semianalytical approaches. Our results reveal a mass-dependent dichotomy in PBH effects: massive PBHs ($M_{\mathrm{PBH}}\gtrsim {10}^2{M}_{\odot }$) with sufficient abundance can accelerate structure formation and shift pop III formation to higher redshifts, potentially conflicting with observational constraints from high-redshift galaxy surveys. Conversely, lower-mass PBHs can induce tidal disruption of gas-rich minihalos, suppressing star formation and delaying the cosmic dawn depending on their abundance. We quantify these competing effects to derive new constraints on the PBH mass function and their contribution to the total dark matter density, with implications for forthcoming observations with the James Webb Space Telescope and 21-cm cosmology experiments.

In this paper, we take a close look at the interaction between the TeV–PeV energy astrophysical neutrinos and a hypothetical cosmic sterile-neutrino background. These interactions yield absorption features, also called “dips”, in the astrophysical neutrino spectrum, which are studied using the deposited energy distribution of high-energy starting events (HESE) in the IceCube detector. We improve upon the previous analysis by including the effects of regeneration and a realistic source distribution on the propagation of astrophysical neutrinos. We use the latest 7.5-year HESE dataset and include the observation of Glashow resonance in our analysis. We evaluate the impact of these dips on the inferred spectral index and overall normalization of the astrophysical neutrinos. We find a mild preference for dips in the 300–800 TeV range, and the best-fit parameters for the mass of sterile-neutrino and the mediator are 0.5 eV and 23 MeV, respectively. We find that the inclusion of these absorption features lowers the spectral index of astrophysical neutrinos to ${2.60}_{-0.16}^{+0.19}$. We show qualitatively that the lower spectral index from the HESE sample can reduce the disagreement with the Northern Tracks sample. We also forecast the event spectrum for IceCube-Gen2 for the two different fits.

Models of blazar jets, which explain observations of their photon spectra, typically predict too few neutrinos to be possibly seen by existing telescopes. In particular, they fall short in reproducing the first neutrino ever detected from a blazar, TXS $0506+056$, by IceCube in 2017. We predict larger neutrino fluxes by using the same jet models, extended to include deep inelastic scatterings between protons within the jets and sub-GeV dark matter (DM) around the central black holes of blazars. In this way we succeed in explaining neutrino observations of TXS $0506+056$, for DM parameters allowed by all laboratory, direct, and indirect searches. Our proposal will be tested by DM searches, as well as by the observation of more neutrinos from blazars. Our findings motivate one to implement DM-nuclei interactions in jet models and to improve our knowledge of DM spikes around active galactic nuclei.

The next generation of gravitational-wave detectors, such as the Einstein Telescope, is designed to reduce noise in a wide band of frequencies compared to the current generation, through the use of new technologies. ETpathfinder, designed as an R&D facility for these technologies, is a prototype for which the mirrors were chosen to be made of crystalline silicon, produced by the Leibniz-Institut für Kristallzüchtung. This material choice was made to pave the way for a low thermal noise level at cryogenic temperatures in the Einstein Telescope. This paper shows the mechanical loss of silicon designated to become the test masses for ETpathfinder in the range between room temperature and 53 K. In addition, the effect of the anisotropic nature of silicon on the measurement procedure is addressed. Predictions are made of the contribution of the mirror substrate material to the overall ETpathfinder noise budget.

Paleodetection has been proposed as a competitive method for detecting dark matter and other new physics interactions, complementing conventional direct-detection experiments. In this work, we utilize trim simulations to improve the modeling of track-length distributions. Our findings suggest that previous studies have overestimated the number of tracks caused by weakly interacting particles, and that the lowest observable dark matter mass should be higher than previously predicted. These differences are mainly attributed to the fact that (a) the recoil energy–track-length relation is not one to one, (b) at low recoil energies, a substantial fraction of recoils do not yield any tracks, and (c) at high energies, electronic stopping becomes dominant, resulting in a track-length barrier at $\sim 200\mathrm{nm}$. In addition to WIMPs, we also modeled tracks from generalized coherent elastic neutrino nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) via new light mediators and estimated the projected sensitivity for these interactions.

Neutrinos experience collective flavor conversion in extreme astrophysical environments such as core-collapse supernovae (CCSNe). One manifestation of collective conversion is slow flavor conversion (SFC), which has recently attracted renewed interest owing to its ubiquity across different regions of the supernova environment. In this study, we systematically examine the evolution of kinematic decoherence in a dense neutrino gas undergoing SFC, considering lepton number asymmetries as large as 30%. Our findings show that the neutrino gas asymptotically evolves toward a generic state of coarse-grained flavor equilibration which is constrained by approximate lepton number conservation. The equilibration occurs within a few factors of the inverse vacuum oscillation frequency, ${\omega }^{-1}$, which corresponds to (anti)neutrinos reaching near flavor equipartition after a few kilometers for typical supernova neutrino energies. Notably, the quasisteady state of the neutrino number densities can be quantitatively described by the neutrino-antineutrino number density ratio $n_{{\overline{\nu }}_e}/n_{{\nu }_e}$ alone. Such a simple estimation opens new opportunities for incorporating SFC into CCSN simulations, particularly in regions where SFC develops on scales much shorter than those of collisions.

If particle dark matter (DM) and primordial black holes (PBHs) coexist, PBHs will be surrounded by particle DM, forming celestial objects known as dressed PBHs (dPBHs). These structures suggest a scenario in which PBHs and DM can exist simultaneously. However, in the high-frequency regime, the gravitational lensing effect of bare PBHs is similar to that of dPBHs. Ground-based gravitational wave (GW) detectors are particularly sensitive to high-frequency GW signals. In this regime, the lensing effect of a point-mass lens with a mass in the range of ${10}^{-1}-{10}^2{M}_{\odot }$ becomes significant. In this work, we incorporate dPBH models with GW observations and employ Bayesian inference techniques to distinguish PBHs from dPBHs. Using the third-generation ground-based GW detectors, Einstein Telescope (ET) and Cosmic Explorer (CE), as examples, we demonstrate that these detectors can effectively differentiate the lensing effects of dPBHs from those of PBHs across a broad frequency range. Furthermore, we find that with a larger black hole mass inside the surrounding particle DM, ET and CE can distinguish these two lensed models with even greater precision.

We present the full release of the atlas of continuous gravitational waves, covering frequencies from 20 to 1700 Hz and spin downs from $-5\times {10}^{-10}$ to $5\times {10}^{-10}\mathrm{Hz}/\mathrm{s}$. Compared to the early atlas release, we have extended the frequency range and have performed follow-up on the outliers. Conducting continuous wave searches is computationally intensive and time-consuming. The atlas facilitates the execution of new searches with relatively minimal computing resources.

We study the spin-entangled mixed state of a spin-$1/2$ baryon–antibaryon pair produced in the process $e^{+}{e}^{-}\to J/\psi ,{\psi }^{\prime }\to \mathcal{B}\overline{\mathcal{B}}$. We show that the spin entanglement of the system can increase following the decays $\mathcal{B}\to \mathcal{b}+M$ and $\overline{\mathcal{B}}\to \overline{\mathcal{b}}+\overline{M}$, where $\mathcal{b},\overline{\mathcal{b}}$ are spin-$1/2$ baryons and $M,\overline{M}$ are spin-0 mesons. This phenomenon, known as entanglement autodistillation, manifests as a probabilistic amplification of entanglement during the decay process. We analyze the underlying mechanism and show that this phenomenon depends only on the initial state of the $\mathcal{B}\overline{\mathcal{B}}$ system and the decay parameter ${\alpha }_D$, but not on the decay parameter ${\varphi }_D$. This effect only arises when parity is violated in the decay, when ${\alpha }_D\ne 0$.

We conducted a study using the modified Godfrey-Isgur quark model and quark pair creation model to investigate the spectrum and two-body strong decays of the newly discovered $\kappa (2600)$ resonance by the LHCb collaboration. Our analysis revealed that this resonance can be assigned as the fourth radial excitation within the $0^{+}$ light strange meson family. Furthermore, we predicted additional radial excitations in this meson family and systematically discussed their spectra, decay behaviors, and branching ratios. These results provide critical guidance for future to identify their signatures in experiments.

Scalar nonstandard interactions (SNSI) present an exciting pathway for probing potential new physics that extends beyond the Standard Model (BSM). The scalar coupling of neutrinos with matter can appear as a subdominant effect that can impact the neutrino oscillation probabilities. The uniqueness of these interactions lies in their direct effect on the neutrino mass matrix, which makes oscillations sensitive to the absolute neutrino mass. The impact of SNSI scales linearly with matter density, which motivates its exploration in the long-baseline sector. The presence of SNSI can influence the key measurements in the field of neutrino physics, including the determination of the leptonic $CP$ phase (${\delta }_{CP}$), neutrino mass ordering, and ${\theta }_{23}$ octant. The precise determination of ${\delta }_{CP}$ is one of the major goals of the Deep Underground Neutrino Experiment (DUNE), which is an upcoming long-baseline experiment. A better understanding of the impact of SNSI on $CP$ measurement sensitivities is crucial for accurate interpretation of ${\delta }_{CP}$ phase. We have analytically explored the dependence of probabilities on the absolute $\nu$ masses and fundamental mixing parameters in the presence of SNSI. We observe that the presence of off-diagonal SNSI elements $|{\eta }_{\alpha \beta }|$ and their associated phases ${\varphi }_{\alpha \beta }$ can significantly affect the $CP$-measurement sensitivities at DUNE. We note that $CP$-violation sensitivities also depend on the absolute neutrino masses. We look for constraining the off-diagonal parameters for different lightest neutrino masses. We observe that $|{\eta }_{\alpha \beta }|$ is more tightly constrained if the neutrino mass is higher. We also explore their correlation with ${\delta }_{CP}$, investigating potential degeneracies that can arise due to SNSI phases (${\varphi }_{\alpha \beta }$). We also perform a correlation study among different SNSI elements.