We present the connected even-parity galaxy 4-Point Correlation Function (4PCF) of DESI Year 1 (Y1) Luminous Red Galaxies (LRGs). This is one of the first measurements of the connected 4PCF on data, and shows a clear detection at ∼12 to 17σ in the full-sky analysis. We test the robustness of the signal by varying three factors: hemisphere (north vs. south), redshift range (either the full range 0.4 < z < 1.1 or the higher-number-density interval 0.4 < z < 0.8), and sample completeness (the full sample vs. only the most complete regions within the number density-motivated cut). Finally, we cross-correlate different patches that are spatially well-separated, and thus should have largely independent noise. This approach, at leading order, is able to remove mismatch between the covariance matrix of the data and that of the mocks; however, in certain cases at the cost of sensitivity. We find ∼15σ evidence for an even-parity 4PCF in this approach. Overall, the studies of the 4PCF presented here probe sensitively any mismatch between mock catalogs and data, and also open up the prospect of fitting a model, constraining cosmological parameters and galaxy biases, and searching for Baryon Acoustic Oscillation (BAO) features.

Fuzzy Dark Matter (FDM), composed of ultra-light axions (m_a ∼ 1 × 10^-22 eV), exhibits wave-like properties that can significantly impact early-universe star formation. Using the arepo code with the axirepo module, we simulate the assembly of haloes across a range of axion masses (1 × 10^-22 eV ≤ m_a ≤ 7 × 10^-22 eV) and halo masses (3 × 10^8 M_⊙≤ M_h ≤ 8 × 10^9 M_⊙). We investigate how small-scale dynamics of the FDM density field affect the accumulation of cold, dense gas. We find that the delay in star formation scales inversely with both halo mass and axion mass. While the static, cored geometry of the soliton primarily sets the timing of the initial collapse, we identify a secondary dynamical barrier driven by stochastic fluctuations that is most potent at the low-mass end of our parameter space. These dynamics dictate the spatial scale of dense gas by injecting kinetic energy and inducing significant angular momentum, which can rotationally stabilize gas out to the soliton radius. This wave-driven stirring leads to the formation of extended H_2 plumes and promotes dynamical mixing, effectively starving the central regions and forcing gas to cool in a more fragmented, diffuse manner. Our results indicate a shift from the monolithic central star formation seen in CDM toward lower-mass, fragmented clusters. These internal inefficiencies provide a physical mechanism for delaying Cosmic Dawn beyond the effects of the power spectrum cut-off, which is essential for refining observational constraints on the axion mass.

We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight axion-like component with mass m =10^-24.5eV constitutes a fraction f ≤ 0.3 of the total dark matter. To enable consistent halo identification in mixed-species scenarios, we develop a grid-based halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass haloes and modifying the HMF in a manner dependent on redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored (1 ≤ z ≤ 4, f ≤ 0.3). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation.

Here we report the first measurement of the parity-violating (PV) 4-Point Correlation Function (4PCF) of the Dark Energy Spectroscopic Instrument's Year 1 Luminous Red Galaxy (DESI Y1 LRG) sample, motivated by the potential detection of the PV 4PCF in the Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (SDSS BOSS) galaxies. In our auto-correlation ("auto") analysis, we find a statistically significant excess of the PV signal compared to mocks without any PV, at 4-10σ depending on details of the analysis. This could arise either from genuine PV or from an underestimation of the variance in the mocks; it is unlikely to arise, at the signal level, from a systematic. We then cross-correlate ("cross") the putative PV signal between different, independent patches of sky, and there find no detection of parity violation. The two measurements are in significant tension: while the cross has somewhat larger error bars than the auto, this is not sufficient to explain the discrepancy. We thus present the current work as an intriguing addition to the PV work on BOSS and as motivation for exploring further the relationship between the auto and cross PV 4PCF analyses.

We explore the growth of structure in wave-like dark matter models, where the field and density spectra are peaked at sub-horizon wavenumbers. Starting with the Schrödinger-Poisson system, we derive the scale-dependent evolution of the matter power spectrum during radiation and matter domination. We find a suppression of adiabatic perturbations during radiation domination, controlled by a free-streaming length, and scale-dependent growth of the initially white-noise isocurvature power, controlled by a Jeans scale during matter domination. The results are in qualitative, and in some regimes quantitative, agreement with the quasi-particle picture. We verify the analytic results of the power spectrum with 3+1-dimensional cosmological Schrödinger-Poisson simulations. We propose an analytic formula for the halo mass function, which is in rough agreement with the simulation results at early times after matter-radiation equality. Our simulations show that early halos typically host a soliton.

The particle mass of dark matter (DM) was previously constrained using kinematics of ultra-faint dwarf galaxies to m > 3 × 10^-19 eV. This constraint, which excludes the "fuzzy" range of ultra-light dark matter from comprising all of the DM, relies on an estimate of the heating rate from fuzzy dark matter (FDM) wave interference using linear perturbation theory. Here, we compare the results of this perturbative calculation to full Schrödinger-Poisson simulations of the evolution of star particles in FDM halos. This comparison confirms theoretical expectations that FDM heating is stronger in fully nonlinear simulations due to the formation of a dense central soliton whose fluctuations enhance gravitational perturbations, and that bounds on the DM particle mass using this perturbative method are indeed conservative. We also show that these bounds are not affected by possible tidal stripping, since for dwarf satellites like Segue 1, the tidal radius is much larger than the observed size of the galaxy. We further show that the constraints on the mass cannot be evaded by invoking DM self-interactions, due to constraints on the self-interaction from large-scale structure. Lastly, we show that if the recently discovered system Ursa Major III/UNIONS I is a galaxy, the observed properties of this object strengthen the lower bound on the DM mass by over an order of magnitude, to m > 8 × 10^-18 eV, at 95

We show that the gravothermal collapse of self-interacting dark matter (SIDM) halos can deviate from local thermodynamic equilibrium. As a consequence, the self-similar evolution predicted by the commonly adopted conducting fluid model can be altered or broken. Our results are obtained using a novel, efficient kinetic solver called KiSS-SIDM for tracing the gravothermal evolution based on the direct simulation Monte Carlo framework. In the long mean free path stage, the code is a viable alternative to the fluid model, yet requires no calibration parameters. Further, this method enables a fully kinetic treatment well into the late, short mean free path, stage of the collapse. We apply the method to a canonical case with isotropic, velocity independent scattering. We find that although a fluid treatment is appropriate deep in the short mean free path core, departures from local thermodynamic equilibrium develop in the intermediate mean free path region bounding the core, which modify the late-time evolution.

We study the implications of relaxing the requirement for ultralight axions to account for all dark matter in the Universe by examining mixed dark matter (MDM) cosmologies with axion fractions f <= 0.3 within the fuzzy dark matter window 10(-25) eV less than or similar to m less than or similar to 10(-23) eV. Our simulations, using a new MDM gravity solver implemented in AxiREPO, capture wave dynamics across various scales with high accuracy down to redshifts z approximate to 1. We identify haloes with Rockstar using the cold dark matter component and find good agreement of inferred halo mass functions and concentration-mass relations with theoretical models across redshifts z=1-10. This justifies our halo finder approach a posteriori as well as the assumptions underlying the MDM halo model AxionHMcode. Using the inferred axion halo mass-cold halo mass relation Ma(Mc) and calibrating a generalized smoothing parameter alpha to our MDM simulations, we present a new version of AxionHMcode. The code exhibits excellent agreement with simulations on scales k<20hcMpc(-1) at redshifts z=1-3.5 for f <= 0.1 around the fiducial axion mass m=10(-24.5)eV=3.16x10(-25)eV, with maximum deviations remaining below 10 per cent. For axion fractions f <= 0.3, the model maintains accuracy with deviations under 20 per cent at redshifts z approximate to 1 and scales k<10hcMpc(-1), though deviations can reach up to 30 per cent for higher redshifts when f=0.3. Reducing the run-time for a single evaluation of AxionHMcode to below 1 min, these results highlight the potential of AxionHMcode to provide a robust framework for parameter sampling across MDM cosmologies in Bayesian constraint and forecast analyses.

Recent studies have found evidence for parity violation in the BOSS spectroscopic galaxy survey, with statistical significance as high as 7 sigma. sigma . These analyses assess the significance of the parity-odd four-point correlation function (4PCF) with a statistic called chi 2 . This statistic is biased if the parity-even eight-point correlation function (8PCF) of the data differs from the mock catalogs. We construct new statistics chi 2 x , chi 2null that separate the parity violation signal from the 8PCF bias term, allowing them to be jointly constrained. Applying these statistics to BOSS, we find that the parity violation signal ranges from 0 to 2.5 sigma . 5 sigma depending on analysis choices, whereas the 8PCF bias term is similar to 6 sigma. sigma . We conclude that there is no compelling evidence for parity violation in BOSS. Our new statistics can be used to search for parity violation in future surveys, such as DESI, without 8PCF biases.

Using a single gravitational lens system observed at $\lesssim5$ milli-arcsecond resolution with very long baseline interferometry (VLBI), we place a lower bound on the mass of the fuzzy dark matter (FDM) particle, ruling out $m_\chi \leq 4.4\times10^{-21}~\mathrm{eV}$ with a 20:1 posterior odds ratio relative to a smooth lens model. We generalize our result to non-scalar and multiple-field models, such as vector FDM, with $m_{\chi,\mathrm{vec}} > 1.4 \times 10^{-21}~\mathrm{eV}$. Due to the extended source structure and high angular resolution of the observation, our analysis is directly sensitive to the presence of granule structures in the main dark matter halo of the lens, which is the most generic prediction of FDM theories. A model based on well-understood physics of ultra-light dark matter fields in a gravitational potential well makes our result robust to a wide range of assumed dark matter fractions and velocity dispersions in the lens galaxy. Our result is competitive with other lower bounds on $m_\chi$ from past analyses, which rely on intermediate modelling of structure formation and/or baryonic effects. Higher resolution observations taken at 10 to 100 GHz could improve our constraints by up to 2 orders of magnitude in the future.

Dark matter as scalar particles consisting of multiple species is well motivated in string theory where axion fields are ubiquitous. A two-field fuzzy dark matter (FDM) model features two species of ultralight axion particles with different masses, $m_1 \neq m_2$, which is extended from the standard one-field model with $m_a \sim 10^{-22}\,{\rm eV}$. Here we perform numerical simulations to explore the properties of two-field FDM haloes. We find that the central soliton has a nested structure when $m_2 \gg m_1$, which is distinguishable from the generic flat-core soliton in one-field haloes. However, the formation of this nested soliton is subject to many factors, including the density fraction and mass ratio of the two fields. Finally, we study non-linear structure formation in two-field cosmological simulations with self-consistent initial conditions and find that the small-scale structure in two-field cosmology is also distinct from the one-field model in terms of DM halo counts and soliton formation time.

ABSTRACT Fuzzy dark matter (FDM) is a dark matter candidate consisting of ultralight scalar particles with masses around $10^{-22}\, \mathrm{eV}/c^2$, a regime where cold bosonic matter behaves as a collective wave rather than individual particles. Although constraints on FDM are accumulating in many different contexts, very few have been verified by self-consistent numerical simulations. We present new large numerical simulations of cosmic structure formation with FDM, solving the full Schrödinger–Poisson (SP) equations using the AxiREPO code, which implements a pseudo-spectral numerical method. Combined with our previous simulations, they allow us to draw a four-way comparison of matter clustering, contrasting results (such as power spectra) for each combination of initial conditions (ICs; FDM versus cold dark matter, CDM) and dynamics (SP versus N-body). By disentangling the impact of ICs and non-linear dynamics in this manner, we can gauge the validity of approximate methods used in previous works, such as ordinary N-body simulations with an FDM initial power spectrum. Due to the comparatively large volume achieved in our FDM simulations, we are able to measure the FDM halo mass function from full wave simulations for the first time, and compare to previous results obtained using analytic or approximate approaches. We also investigate the density profiles of these filaments and compare to their ΛCDM counterparts.

ABSTRACT In the fuzzy dark matter (FDM) model, gravitationally collapsed objects always consist of a solitonic core located within a virialized halo. Although various numerical simulations have confirmed that the collapsed structure can be described by a cored Navarro–Frenk–White-like density profile, there is still disagreement about the relation between the core mass and the halo mass. To fully understand this relation, we have assembled a large sample of cored haloes based on both idealized soliton mergers and cosmological simulations with various box sizes. We find that there exists a sizeable dispersion in the core–halo mass relation that increases with halo mass, indicating that the FDM model allows cores and haloes to coexist in diverse configurations. We provide a new empirical equation for a core–halo mass relation with uncertainties that can encompass all previously found relations in the dispersion, and emphasize that any observational constraints on the particle mass m using a tight one-to-one core–halo mass relation should suffer from an additional uncertainty of the order of 50 per cent for halo masses ${\gtrsim} 10^9 \, [8\times 10^{-23} \, \mathrm{eV}/(mc^2)]^{3/2} \, \mathrm{M}_\odot$. We suggest that tidal stripping may be one of the effects contributing to the scatter in the relation.

ABSTRACT An ultralight bosonic particle of mass around $10^{-22}\, \mathrm{eV}/c^2$ is of special interest as a dark matter candidate, as it both has particle physics motivations, and may give rise to notable differences in the structures on highly non-linear scales due to the manifestation of quantum-physical wave effects on macroscopic scales, which could address a number of contentious small-scale tensions in the standard cosmological model, ΛCDM. Using a spectral technique, we here discuss simulations of such fuzzy dark matter (FDM), including the full non-linear wave dynamics, with a comparatively large dynamic range and for larger box sizes than considered previously. While the impact of suppressed small-scale power in the initial conditions associated with FDM has been studied before, the characteristic FDM dynamics are often neglected; in our simulations, we instead show the impact of the full non-linear dynamics on physical observables. We focus on the evolution of the matter power spectrum, give first results for the FDM halo mass function directly based on full FDM simulations, and discuss the computational challenges associated with the FDM equations. FDM shows a pronounced suppression of power on small scales relative to cold dark matter (CDM), which can be understood as a damping effect due to ‘quantum pressure’. In certain regimes, however, the FDM power can exceed that of CDM, which may be interpreted as a reflection of order-unity density fluctuations occurring in FDM. In the halo mass function, FDM shows a significant abundance reduction below a characteristic mass scale only. This could in principle alleviate the need to invoke very strong feedback processes in small galaxies to reconcile ΛCDM with the observed galaxy luminosity function, but detailed studies that also include baryons will be needed to ultimately judge the viability of FDM.

minimal-lagrangians is a Python program which allows one to specify the field content of an extension of the Standard Model of particle physics and, using this information, to generate the most general renormalizable Lagrangian that describes such a model. As the program was originally created for the study of minimal dark matter models with radiative neutrino masses, it can handle additional scalar or Weyl fermion fields which are SU(3)(C) singlets, SU(2)(L) singlets, doublets or triplets, and can have arbitrary U(1)(Y) hypercharge. It is also possible to enforce an arbitrary number of global U(1) symmetries (with Z(2) as a special case) so that the new fields can additionally carry such global charges. In addition to human-readable and (LTEX)-T-A output, the program can generate SARAH model files containing the computed Lagrangian, as well as information about the fields after electroweak symmetry breaking (EWSB), such as vacuum expectation values (VEVs) and mixing matrices. This capability allows further detailed investigation of the model in question, with minimal-lagrangians as the first component in a tool chain for rapid phenomenological studies of "minimal" dark matter models requiring little effort and no unnecessary input from the user. Program summary Program title: minimal-lagrangians CPC Library link to program files: https://doi.org/10.17632/4mm2zk5r84.1 Licensing provisions: GPLv3 Programming language: Python Nature of problem: Given a quantum field theory's gauge group, it is sufficient to specify the particle (field) content in order to identify the full renormalizable theory, up to the parameters in its Lagrangian. However, the process of determining the Lagrangian manually is not only tedious and error-prone, but also involves additional complications such as redundant terms or the question of whether the theory is anomaly-free. Solution method: minimal-lagrangians generates the complete renormalizable Lagrangian for a given model with the Standard Model gauge group SU(3)(C) x SU(2)(L) x U(1)(Y), including interaction terms. Redundant terms in the Lagrangian are eliminated in order to avoid duplicated parameters. The particle content is also checked for gauge anomalies, including the Witten SU(2) anomaly [1]. The model will automatically be modified to make fermions vector-like if necessary. The generated Lagrangian can be output in SARAH [2,3] model file format so that the model is immediately available for detailed phenomenological study using the capabilities of SARAH. Additional comments including restrictions and unusual features: Instead of manually determining the details of a model, the only input to the program minimal-lagrangians is the particle content. Using the output to SARAH, minimal-lagrangians thus forms the first step in a tool chain which enables the complete implementation and study of a new model with minimal effort and no "boilerplate'' user input. The focus is on "minimal" dark matter models, i.e. those with the Standard Model gauge group (no additional gauge fields), where the new fields are color singlets and at most triplets under SU(2)(L). (C) 2020 Elsevier B.V. All rights reserved.

In this master's thesis, the minimal dark matter models with radiative neutrino masses introduced in arXiv:1308.3655 are examined both in general and, using the model T1-3-B ($\alpha = 0$) as a representative, in more detail. In the process, it is both shown how such models are built and a numerical analysis tool chain is established, automating as many steps as possible from the very beginning (deriving the Lagrangian from a given field content) to the very end (calculating observables such as the dark matter relic density, the direct detection cross section and the neutrino masses and mixing matrices). As an important result in laying out the mathematical groundwork, a convention for representations of SU(2) is established which, in this form, is not found in previous works. Another major result is the development of the program minimal-lagrangians, whose capabilities are described in the thesis. It is of great use both for the construction of Lagrangians for new models as well their verification or quick surveys. minimal-lagrangians can be applied to any model within the class it is designed to handle, extending its utility far beyond a one-time result that is only obtained for a single model. Finally, the first steps in the analysis of the model T1-3-B ($\alpha = 0$) are taken. It is shown that the model can reproduce both the singlet-doublet fermion dark matter model and the inert triplet model in the appropriate limits. Moreover, the neutrino mass matrix is found and it is demonstrated that the model can accommodate current constraints on the neutrino masses. Lastly, the behavior of the dark matter relic density as it depends on the parameter responsible for the generation of neutrino masses is investigated. Further in-depth study of the model T1-3-B ($\alpha = 0$) was performed in a separate publication (arXiv:1812.11133).

In these proceedings, we present a study of a combined singlet–doublet fermion and triplet scalar model for dark matter (DM). Together, these models form a simple extension of the Standard Model (SM) that can account for DM and explain the existence of neutrino masses, which are generated radiatively. However, this also implies the existence of lepton flavour violating (LFV) processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new ℤ_2 symmetry to stabilise the DM candidate. We analyse the DM, neutrino mass and LFV aspects, exploring the viable parameter space of the model. This is done using a numerical random scan imposing successively the neutrino mass and mixing, relic density, Higgs mass, direct detection, collider and LFV constraints. We find that DM in this model is fermionic for masses below about 1 TeV and scalar above. We observe a high degree of complementarity between direct detection and LFV experiments, which should soon allow to fully probe the fermionic DM sector and at least partially the scalar DM sector.