ABSTRACT
We present a novel procedure to estimate the equation of state of the intergalactic medium in the quasi-linear regime of structure formation based on Ly α forest tomography and apply it to ...21 high-quality quasar spectra from the UVES_SQUAD survey at redshift z = 2.5. Our estimation is based on a full tomographic inversion of the line of sight. We invert the data with two different inversion algorithms, the iterative Gauss–Newton method and the regularized probability conservation approach, which depend on different priors and compare the inversion results in flux space and in density space. In this way our method combines fitting of absorption profiles in flux space with an analysis of the recovered density distributions featuring prior knowledge of the matter distribution. Our estimates are more precise than existing estimates, in particular on small redshift bins. In particular, we model the temperature–density relation with a power law and observe for the temperature at mean density $T_0 = 13\,400^{+1700}_{-1300}\, \mathrm{K}$ and for the slope of the power law (polytropic index) γ = 1.42 ± 0.11 for the power-law parameters describing the temperature–density relation. Moreover, we measure an photoionization rate $\Gamma _{-12} = 1.1^{+0.16}_{-0.17}$. An implementation of the inversion techniques used will be made publicly available.
It is shown how the time series obtained from searches for ultralight bosonic dark matter (DM), such as the axion, can be used to determine whether it is in a coherent or incoherent quantum state. ...The example is essentially trivial, but it is hoped that explicitly addressing it will provoke experimental exploration. In the standard coherent state, O(1)$\mathcal {O}(1)$ oscillations in the number density occur over the coherence time, τc=h/mv2$\tau _{\rm c}=h/m v^2$, where m is the particle mass and v is the galactic virial velocity, leading to a reduction in the constraining power of experiments operating on timescales T<τc$T<\tau _{\rm c}$, due to the unknown global phase. On the other hand, if the DM is incoherent then no such strong number oscillations occur since the ensemble average over particles in different streams gives an effective phase average. If an experiment detects a signal then the coherent or incoherent nature of DM can be determined by time series analysis over the coherence time. This finding is observationally relevant for DM masses, 10−17eV≲m≲10−11eV$10^{-17}\text{ eV}\lesssim m\lesssim 10^{-11}\text{ eV}$ (corresponding to coherence times between a year and 100 s).
It is demonstrated how the time series obtained from searches for ultralight bosonic dark matter, such as the axion, can be used to determine whether it is in a coherent or incoherent quantum state.
ABSTRACT
Many models of high energy physics suggest that the cosmological dark sector consists of not just one, but a spectrum of ultralight scalar particles with logarithmically distributed masses. ...To study the potential signatures of low concentrations of ultralight axion (also known as fuzzy) dark matter, we modify Lagrangian perturbation theory (LPT) by distinguishing between trajectories of different dark matter species. We further adapt LPT to include the effects of a quantum potential, which is necessary to generate correct initial conditions for ultralight axion simulations. Based on LPT, our modified scheme is extremely efficient on large scales and it can be extended to an arbitrary number of particle species at very little computational cost. This allows for computation of self-consistent initial conditions in mixed dark matter models. Additionally, we find that shell-crossing is delayed for ultralight particles and that the deformation tensor extracted from LPT can be used to identify the range of redshifts and scales for which the Madelung formalism of fuzzy dark matter can lead to divergences.
In many environmental scenarios, the fate and impact of polymer nanocomposites (PNCs) that contain carbon nanotubes (CNT/PNCs) will be influenced by their interactions with microorganisms, with ...implications for antimicrobial properties and the long-term persistence of PNCs. Using oxidized single-wall (O-SWCNTs) and multi-wall CNTs (O-MWCNTs), we explored the influence that CNT loading (mass fraction≤0.1%-10%) and type have on the initial interactions of Pseudomonas aeruginosa with O-CNT/poly(vinyl alcohol) (PVOH) nanocomposites containing well-dispersed O-CNTs. LIVE/DEAD staining revealed that, despite oxidation, the inclusion of O-SWCNTs or O-MWCNTs caused PNC surfaces to exhibit antimicrobial properties. The fraction of living cells deposited on both O-SWCNT and O-MWCNT/PNC surfaces decreased exponentially with increasing CNT loading, with O-SWCNTs being approximately three times more cytotoxic on a % w/w basis. Although not every contact event between attached microorganisms and CNTs led to cell death, the cytotoxicity of the CNT/PNC surfaces scaled with the total contact area that existed between the microorganisms and CNTs. However, because the antimicrobial properties of CNT/PNC surfaces require direct CNT-microbe contact, dead cells were able to shield living cells from the cytotoxic effects of CNTs, allowing biofilm formation to occur on CNT/PNCs exposed to Pseudomonas aeruginosa for longer time periods.
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