We review the status of searches for sterile neutrinos in the ∼1eV range, with an emphasis on the latest results from short baseline oscillation experiments and how they fit within sterile neutrino ...oscillation models. We present global fit results to a three-active-flavor plus one-sterile-flavor model (3+1), where we find an improvement of Δχ2=35 for 3 additional parameters compared to a model with no sterile neutrino. This is a 5σ improvement, indicating that an effect that is like that of a sterile neutrino is highly preferred by the data. However we note that separate fits to the appearance and disappearance oscillation data sets within a 3+1 model do not show the expected overlapping allowed regions in parameter space. This “tension” leads us to explore two options: 3+2, where a second additional mass state is introduced, and a 3+1+decay model, where the ν4 state can decay to invisible particles. The 3+1+decay model, which is also motivated by improving compatibility with cosmological observations, yields the larger improvement, with a Δχ2=8 for 1 additional parameter beyond the 3+1 model, which is a 2.6σ improvement. Moreover the tension between appearance and disappearance experiments is reduced compared to 3+1, although disagreement remains. In these studies, we use a frequentist approach and also a Bayesian method of finding credible regions.
With respect to this tension, we review possible problems with the global fitting method. We note multiple issues, including problems with reproducing the experimental results, especially in the case of experiments that do not provide adequate data releases. We discuss an unexpected 5 MeV excess, observed in the reactor flux energy spectrum, that may be affecting the oscillation interpretation of the short baseline reactor data. We emphasize the care that must be taken in mapping to the true neutrino energy in the case of oscillation experiments that are subject to multiple interaction modes and nuclear effects. We point to problems with the “Parameter-Goodness-of-Fit test” that is used to quantify the tension. Lastly, we point out that analyses presenting limits often receive less scrutiny that signals.
While we provide a snapshot of the status of sterile neutrino searches today and global fits to their interpretation, we emphasize that this is a fast-moving field. We briefly review experiments that are expected to report new data in the immediate future. Lastly, we consider the 5-year horizon, where we propose that decay-at-rest neutrino sources are the best method of finally resolving the confusing situation.
High-energy muon and electron neutrinos yield a non-negligible flux of tau neutrinos as they propagate through Earth. In this Letter, we address the impact of this additional component in the PeV and ...EeV energy regimes for the first time. Above 300 TeV, this contribution is predicted to be significantly larger than the atmospheric background, and it alters current and future neutrino telescopes' capabilities to discover a cosmic tau-neutrino flux. Further, we demonstrate that Earth-skimming neutrino experiments, designed to observe tau neutrinos, will be sensitive to cosmogenic neutrinos even in extreme scenarios without a primary tau-neutrino component.
The motion of S-stars around the Galactic center implies that the central gravitational potential is dominated by a compact source, Sagittarius A* (Sgr A*), which has a mass of about 4 × 10
6
M
⊙
and ...is traditionally assumed to be a massive black hole (BH). The explanation of the multiyear accurate astrometric data of the S2 star around Sgr A*, including the relativistic redshift that has recently been verified, is particularly important for this hypothesis and for any alternative model. Another relevant object is G2, whose most recent observational data challenge the scenario of a massive BH: its post-pericenter radial velocity is lower than expected from a Keplerian orbit around the putative massive BH. This scenario has traditionally been reconciled by introducing a drag force on G2 by an accretion flow. As an alternative to the central BH scenario, we here demonstrate that the observed motion of both S2 and G2 is explained in terms of the
dense core – diluted halo
fermionic dark matter (DM) profile, obtained from the fully relativistic Ruffini-Argüelles-Rueda (RAR) model. It has previously been shown that for fermion masses 48−345 keV, the RAR-DM profile accurately fits the rotation curves of the Milky Way halo. We here show that the solely gravitational potential of such a DM profile for a fermion mass of 56 keV explains (1) all the available time-dependent data of the position (orbit) and line-of-sight radial velocity (redshift function
z
) of S2, (2) the combination of the special and general relativistic redshift measured for S2, (3) the currently available data on the orbit and
z
of G2, and (4) its post-pericenter passage deceleration without introducing a drag force. For both objects, we find that the RAR model fits the data better than the BH scenario: the mean of reduced chi-squares of the time-dependent orbit and
z
data are ⟨
χ
̄
2
⟩
S2,RAR
≈ 3.1 and ⟨
χ
̄
2
⟩
S2,BH
≈ 3.3 for S2 and ⟨
χ
̄
2
⟩
G2,RAR
≈ 20 and ⟨
χ
̄
2
⟩
G2,BH
≈ 41 for G2. The fit of the corresponding
z
data shows that while for S2 we find comparable fits, that is,
χ
̄
2
z,RAR
≈ 1.28 and
χ
̄
2
z,BH
≈ 1.04, for G2 the RAR model alone can produce an excellent fit of the data, that is,
χ
̄
2
z,RAR
≈ 1.0 and
χ
̄
2
z,BH
≈ 26. In addition, the critical mass for gravitational collapse of a degenerate 56 keV-fermion DM core into a BH is ∼ 10
8
M
⊙
. This result may provide the initial seed for the formation of the observed central supermassive BH in active galaxies, such as M 87.
Abstract
Nonlinear structure formation for fermionic dark matter particles leads to dark matter density profiles with a degenerate compact core surrounded by a diluted halo. For a given fermion mass, ...the core has a critical mass that collapses into a supermassive black hole (SMBH). Galactic dynamics constraints suggest a ∼100 keV/
c
2
fermion, which leads to ∼10
7
M
⊙
critical core mass. Here, we show that baryonic (ordinary) matter accretion drives an initially stable dark matter core to SMBH formation and determines the accreted mass threshold that induces it. Baryonic gas density
ρ
b
and velocity
v
b
inferred from cosmological hydrosimulations and observations produce sub-Eddington accretion rates triggering the baryon-induced collapse in less than 1 Gyr. This process produces active galactic nuclei in galaxy mergers and the high-redshift Universe. For TXS 2116–077, merging with a nearby galaxy, the observed 3 × 10
7
M
⊙
SMBH, for
Q
b
=
ρ
b
/
v
b
3
=
0.125
M
⊙
/
(
100
km
s
−
1
pc
)
3
, forms in ≈0.6 Gyr, consistent with the 0.5–2 Gyr merger timescale and younger jet. For the farthest central SMBH detected by the Chandra X-ray satellite in the
z
= 10.3 UHZ1 galaxy observed by the James Webb Space Telescope (JWST), the mechanism leads to a 4 × 10
7
M
⊙
SMBH in 87–187 Myr, starting the accretion at
z
= 12–15. The baryon-induced collapse can also explain the ≈10
7
–10
8
M
⊙
SMBHs revealed by JWST at
z
≈ 4–6. After its formation, the SMBH can grow to a few 10
9
M
⊙
in timescales shorter than 1 Gyr via sub-Eddington baryonic mass accretion.
Hinting a dark matter nature of Sgr A via the S-stars Becerra-Vergara, E A; Argüelles, C R; Krut, A ...
Monthly Notices of the Royal Astronomical Society Letters,
07/2021, Letnik:
505, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
The motion data of the S-stars around the Galactic Centre gathered in the last 28 yr imply that Sgr A* hosts a supermassive compact object of about $4 \times 10^6\, {\rm M}_{\odot }$, a ...result awarded with the Nobel Prize in Physics 2020. A non-rotating black hole (BH) nature of Sgr A* has been uncritically adopted since the S-star orbits agree with Schwarzschild geometry geodesics. The orbit of S2 has served as a test of general relativity predictions such as the gravitational redshift and the relativistic precession. The central BH model is, however, challenged by the G2 post-peripassage motion and by the lack of observations on event-horizon-scale distances robustly pointing to its univocal presence. We have recently shown that the S2 and G2 astrometry data are better fitted by geodesics in the spacetime of a self-gravitating dark matter core–halo distribution of 56 keV-fermions, ‘darkinos’, which also explains the outer halo Galactic rotation curves. This letter confirms and extends this conclusion using the astrometry data of the 17 best-resolved S-stars, thereby strengthening the alternative nature of Sgr A* as a dense core of darkinos.
•Parkinsonian disorders are associated with atrophy in striatal regions.•Thalamic and putaminal atrophy is greatest in PSP patients relative to controls.•Caudal & putamen atrophy correlates with NPI ...scores when controlling for diagnosis.•Striatal regions have greater morphological changes in PSP over PD, MSA, and HCs.
Parkinson's disease (PD), multisystem atrophy (MSA), and progressive supranuclear palsy (PSP) present similarly with bradykinesia, tremor, rigidity, and cognitive impairments. Neuroimaging studies have found differential changes in the nigrostriatal pathway in these disorders, however whether the volume and shape of specific regions within this pathway can distinguish between atypical Parkinsonian disorders remains to be determined. This paper investigates striatal and thalamic volume and morphology as distinguishing biomarkers, and their relationship to neuropsychiatric symptoms. Automatic segmentation to calculate volume and shape analysis of the caudate nucleus, putamen, and thalamus were performed in 18 PD patients, 12 MSA, 15 PSP, and 20 healthy controls, then correlated with clinical measures. PSP bilateral thalami and right putamen were significantly smaller than controls, but not MSA or PD. The left caudate and putamen significantly correlated with the Neuropsychiatric Inventory total score. Bilateral thalamus, caudate, and left putamen had significantly different morphology between groups, driven by differences between PSP and healthy controls. This study demonstrated that PSP patient striatal and thalamic volume and shape are significantly different when compared with controls. Parkinsonian disorders could not be differentiated on volumetry or morphology, however there are trends for volumetric and morphological changes associated with PD, MSA, and PSP.
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