Cosmic Web Dissection in Fuzzy Dark Matter Cosmologies

On large cosmological scales, anisotropic gravitational collapse is manifest in the dark cosmic web. Its statistical properties are little known for alternative dark matter models such as fuzzy dark matter (FDM). In this work, we assess for the first time the relative importance of cosmic nodes, filaments, walls and voids in a cosmology with primordial small-scale suppression of power. We post-process $N$-body simulations of FDM-like cosmologies with varying axion mass $m$ at redshifts $z\sim 1.0-5.6$ using the NEXUS+ Multiscale Morphology Filter technique at smoothing scale $\Delta x = 0.04 \ h^{-1}$Mpc. The formation of wall and void halos is more suppressed than naively expected from the half-mode mass $M_{1/2}$. Also, we quantify the mass and volume filling fraction of cosmic environments and find that 2D cosmic sheets host a larger share of the matter content of the Universe as $m$ is reduced, with an $\sim 8-12$\% increase for the $m=7 \times 10^{-22}$ eV model compared to CDM. We show that in FDM-like cosmologies, filaments, walls and voids are cleaner and more pronounced structures than in CDM, revealed by a strong mid-range peak in the conditioned overdensity PDFs $P(\delta)$. At high redshift, low-density regions are more suppressed than high-density regions. Furthermore, skewness estimates $S_3$ of the total overdensity PDF in FDM-like cosmologies are consistently higher than in CDM, especially at high redshift $z\sim 5.6$ where the $m=10^{-22}$ eV model differs from CDM by $\sim 6 \sigma$. Accordingly, we advocate for the usage of $P(\delta)$ as a testbed for constraining FDM and other alternative dark matter models.Comment: 16 pages, 7 figure

Quantum Carousel: The Fate of a Bound State Attached to a Linear Rotor

We study the angulon problem -- a linear rotor in a bosonic bath -- in the regime where attractive impurity-boson interactions can support a shallow bound state. To study the fate of the angulon in the vicinity of bound-state formation, we formulate a beyond-linear-coupling model. First, we consider attractive, spherically symmetric impurity-boson interactions for which the linear rotor can be mapped onto a static impurity. The well-known polaron formalism provides an adequate description in this limit. For anisotropic potentials, the presence of a shallow bound state with pronounced anisotropic character leads to a many-body instability that washes out the angulon dynamics

Cosmological Structure Formation and Soliton Phase Transition in Fuzzy Dark Matter with Axion Self-Interactions

We investigate cosmological structure formation in Fuzzy Dark Matter (FDM) with an attractive self-interaction (SI) with numerical simulations. Such a SI would arise if the FDM boson were an ultra-light axion, which has a strong CP symmetry-breaking scale (decay constant). Although weak, the attractive SI may be strong enough to counteract the quantum 'pressure' and alter structure formation. We find in our simulations that the SI can enhance small-scale structure formation, and soliton cores above a critical mass undergo a phase transition, transforming from dilute to dense solitons.Comment: 10 pages, 3 figures, submitted to mnra

Third EuCAPT Annual Symposium

Fuzzy dark matter (FDM) modifies the internal properties of dark matter halos and large-scale cosmic environments. In this talk I will share selected insights from recent work based on cosmological $N$-body simulations. We find that the concentration of FDM-like halos peaks around two decades above the half-mode mass, breaking the approximate universality of halo density profiles observed in ΛCDM. Shape parameter profiles (intermediate-to-major and minor-to-major axis ratios) of FDM-like halos are more elongated around the virial radius and less elongated near the center, deviating from the monotonicity observed in ΛCDM. We reassess intrinsic alignment correlations in FDM-like cosmologies and comment on their importance in upcoming weak lensing surveys. Finally, the cosmic web itself sees its mass distribution gradually reshuffled as the axion mass is reduced, leading to changes in the cosmic tidal fields. We quantify the mass and volume filling fractions of cosmic environments and find that in FDM-like cosmologies, 2D cosmic sheets host a larger share of the matter content of the Universe compared to ΛCDM. We show that FDM-like cosmologies exhibit more peaked log overdensity probability distribution functions and systematically higher skewness estimates compared to ΛCDM, particularly at high redshift. These results suggest that the internal properties of dark matter halos and large-scale cosmic environments may offer powerful constraints on FDM and other alternative dark matter models

Linear rotor in an ideal Bose gas near the threshold for binding

We study a linear rotor in a bosonic bath within the angulon formalism. Our focus is on systems where isotropic or anisotropic impurity-boson interactions support a shallow bound state. To study the fate of the angulon in the vicinity of bound-state formation, we formulate a beyond-linear-coupling angulon Hamiltonian. First, we use it to study attractive, spherically symmetric impurity-boson interactions for which the linear rotor can be mapped onto a static impurity. The well-known polaron formalism provides an adequate description in this limit. Second, we consider anisotropic potentials, and show that the presence of a shallow bound state with pronounced anisotropic character leads to a many-body instability that washes out the angulon dynamics

On the cosmic web elongation in fuzzy dark matter cosmologies: Effects on density profiles, shapes, and alignments of haloes

ABSTRACT The fuzzy dark matter (FDM) scenario has received increased attention in recent years due to the small-scale challenges of the vanilla Lambda cold dark matter (ΛCDM) cosmological model and the lack of any experimental evidence for any candidate particle. In this study, we use cosmological N-body simulations to investigate high-redshift dark matter haloes and their responsiveness to an FDM-like power spectrum cutoff on small scales in the primordial density perturbations. We study halo density profiles, shapes, and alignments in FDM-like cosmologies (the latter two for the first time) by providing fits and quantifying departures from ΛCDM as a function of the particle mass m. Compared to ΛCDM, the concentrations of FDM-like haloes are lower, peaking at an m-dependent halo mass and thus breaking the approximate universality of density profiles in ΛCDM. The intermediate-to-major and minor-to-major shape parameter profiles are monotonically increasing with ellipsoidal radius in N-body simulations of ΛCDM. In FDM-like cosmologies, the monotonicity is broken, haloes are more elongated around the virial radius than their ΛCDM counterparts and less elongated closer to the centre. Finally, intrinsic alignment correlations, stemming from the deformation of initially spherically collapsing haloes in an ambient gravitational tidal field, become stronger with decreasing m. At z ∼ 4, we find a 6.4σ-significance in the fractional differences between the isotropized linear alignment magnitudes Diso in the m = 10−22 eV model and ΛCDM. Such FDM-like imprints on the internal properties of virialized haloes are expected to be strikingly visible in the high-z Universe.</jats:p

Star-crossed? The association of the 5-HTTLPR s allele with season of birth in a healthy female population, and possible consequences for temperament, depression and suicide

BACKGROUND: Birth season has well-known effects on neuropsychiatric disorders, and may also influence genotype distribution by possibly influencing chance of conception via parental idiosyncratic conception patterns or survival of foetuses or infants. The 5-HTTLPR is associated with phenomena including affective temperaments or suicide which are also associated with birth season. Our aim was to investigate the association of 5- HTTLPR genotype and birth season in a healthy female population. METHODS: Birth date and 5-HTTLPR genotype was determined for 327 psychiatrically healthy women. The association between presence of s allele and time of birth was analysed using generalized linear models. RESULTS: A significant association between s allele frequency and time of birth was detected. S allele carrier frequency was marginally significantly higher in July borns and significantly lower in autumn borns. LIMITATIONS: We investigated an adult sample so genotype frequency data do not reflect birth frequencies. Our sample consisted exclusively of females. CONCLUSIONS: There is no clear explanation for the observed association, although idiosyncratic parental conception patterns, the association of 5-HTTLPR with sudden infant/intrauterine death, or other s allele-mediated behaviours may play a role. Our results are strikingly parallel with earlier data reporting a higher risk of completed suicide in July borns, and higher scores of July borns and lower scores of autumn borns on certain affective temperament scales, both of which are also associated with the s allele of 5-HTTLPR. Thus our results may add to the growing body of evidence regarding the etiological background of affective disorders

Cosmological structure formation and soliton phase transition in fuzzy dark matter with axion self-interactions

We investigate cosmological structure formation in fuzzy dark matter (FDM) with the attractive self-interaction (SI) with numerical simulations. Such a SI would arise if the FDM boson were an ultra-light axion, which has a strong CP symmetry-breaking scale (decay constant). Although weak, the attractive SI may be strong enough to counteract the quantum ‘pressure’ and alter structure formation. We find in our simulations that the SI can enhance small-scale structure formation, and soliton cores above a critical mass undergo a phase transition, transforming from dilute to dense solitons