We have studied a large number of elliptical galaxies and found a correlation between their dark matter content and the ellipticity of their visible shape. The galaxies were strictly selected so that ...only typical medium-size elliptical galaxies were considered. Galaxies with unusual characteristics were rejected to minimize point-to-point data scatter and avoid systematic biases. Data from six different techniques of extracting the galactic dark matter content were used to avoid methodological biases. A thorough investigation of the interrelation between attributes of elliptical galaxies was carried out to assess whether the correlation originates from an observational bias, but no such origin could be identified. At face value, the correlation found implies that at equal luminosities, rounder medium-size elliptical galaxies appear to contain less dark matter than flatter elliptical galaxies, e.g. the rounder galaxies are on average four times less massive than the flatter ones. This is puzzling in the context of the conventional model of cosmological structure formation.
ABSTRACT
We investigate a correlation between the dark matter content of elliptical galaxies and their ellipticity ϵ that was initially reported in 2014. We use new determinations of dark matter and ...ellipticities that are posterior to that time. Our data set consists of 237 elliptical galaxies passing a strict set of criteria that selects a homogeneous sample of typical elliptical galaxies. We find a relation between the mass-to-light ratio and ellipticity ϵ that is well fitted by M/L = (14.1 ± 5.4)ϵ, which agrees with the result reported in 2014. Our analysis includes 135 galaxies that were not in the 2014 analysis, and includes data sets with refined versions of previous methods. The consistency between the present and 2014 analyses reduces the possibility that the initial observation of the correlation came from approximations in the methods used to estimate dark matter content or lower resolution data, thereby lending support to a physical origin.
Graviballs and dark matter Guiot, B.; Borquez, A.; Deur, A. ...
The journal of high energy physics,
11/2020, Letnik:
2020, Številka:
11
Journal Article
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A
bstract
We investigate the possible existence of graviballs, a system of bound gravitons, and show that two gravitons can be bound together by their gravitational interaction. This idea connects to ...black hole formation by a high-energy 2 →
N
scattering and to the gravitational geon studied by Brill and Hartle. Our calculations rely on the formalism and techniques of quantum field theory, specifically on low-energy quantum gravity. By solving numerically the relativistic equations of motion, we have access to the space-time dynamics of the (2-gravitons) graviball formation. We argue that the graviball is a viable dark matter candidate and we compute the associated gravitational lensing.
Establishing an explicit connection between the long distance physics of confinement and the dynamical interactions of quarks and gluons at short distances has been a long-sought goal of quantum ...chromodynamics. Using holographic QCD, we derive a direct analytic relation between the scale κ which determines the masses of hadrons and the scale Λs which controls the predictions of perturbative QCD at very short distances. The resulting prediction Λs=0.341±0.032 GeV in the MS‾ scheme agrees well with the experimental average 0.339±0.016 GeV. We also derive a relation between Λs and the QCD string tension σ. This connection between the fundamental hadronic scale underlying the physics of quark confinement and the perturbative QCD scale controlling hard collisions can be carried out in any renormalization scheme.
Our present understanding of the universe requires the existence of dark matter and dark energy. We describe here a natural mechanism that could make exotic dark matter and possibly dark energy ...unnecessary. Graviton–graviton interactions increase the gravitational binding of matter. This increase, for large massive systems such as galaxies, may be large enough to make exotic dark matter superfluous. Within a weak field approximation we compute the effect on the rotation curves of galaxies and find the correct magnitude and distribution without need for arbitrary parameters or additional exotic particles. The Tully–Fisher relation also emerges naturally from this framework. The computations are further applied to galaxy clusters.
We present a new extraction of the effective strong coupling constant αs,g1(Q2). The result agrees with a previous determination and extends the measurement of the low and high Q2 behavior of ...αs,g1(Q2) that was previously deduced from sum rules. In particular, it experimentally verifies the lack of Q2-dependence of αs,g1(Q2) in the low Q2 limit. This fact is necessary for application of the AdS/CFT correspondence to QCD calculations. We provide a parameterization of αs,g1(Q2) that can equivalently be used to parameterize the Q2-dependence of the generalized Gerasimov–Drell–Hearn and Bjorken sums.
We present a first attempt to experimentally extract an effective strong coupling constant that we define to be a low Q2 extension of a previous definition by S. Brodsky et al. following an initial ...work of G. Grunberg. Using Jefferson Lab data and sum rules, we establish its Q2-behavior over the complete Q2-range. The result is compared to effective coupling constants inferred from different processes and to calculations based on Schwinger–Dyson equations, hadron spectroscopy or lattice QCD. Although the connection between the experimentally extracted effective coupling constants and the calculations is not established it is interesting to note that their behaviors are similar.
We present new data on the Bjorken sum Γ‾1p−n(Q2) at 4-momentum transfer 0.021≤Q2≤0.496 GeV2. The data were obtained in two experiments performed at Jefferson Lab: EG4 on polarized protons and ...deuterons, and E97110 on polarized 3He from which neutron data were extracted. The data cover the domain where chiral effective field theory (χEFT), the leading effective theory of the Strong Force at large distances, is expected to be applicable. We find that our data and the predictions from χEFT are only in marginal agreement. This is somewhat surprising as the contribution from the Δ(1232) resonance is suppressed in this observable, which should make it more reliably predicted by χEFT than quantities in which the Δ contribution is important. The data are also compared to a number of phenomenological models with various degrees of agreement.
New York City Environmental Protection in conjunction with City College of New York assessed the application of the anammox process in the reject water treatment using a moving bed biofilm reactor ...(MBBR) located at the 26th Ward wastewater treatment plant, in Brooklyn, NY. The single-stage nitritation/anammox MBBR was seeded with activated sludge and consequently was enriched with its own 'homegrown' anammox bacteria (AMX). Objectives of this study included collection of additional process kinetic and operating data and assessment of the effect of nitrogen loading rates on process performance. The initial target total inorganic nitrogen removal of 70% was limited by the low alkalinity concentration available in the influent reject water. Higher removals were achieved after supplementing the alkalinity by adding sodium hydroxide. Throughout startup and process optimization, quantitative real-time polymerase chain reaction (qPCR) analyses were used for monitoring the relevant species enriched in the biofilm and in the suspension. Maximum nitrogen removal rate was achieved by stimulating the growth of a thick biofilm on the carriers, and controlling the concentration of dissolved oxygen in the bulk flow and the nitrogen loading rates per surface area; all three appear to have contributed in suppressing nitrite-oxidizing bacteria activity while enriching AMX density within the biofilm.
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