While I didn't have strong expectations one way or the other, this paper's conclusion is potentially important to understanding galaxy formation, and tends to disfavor a purely accretion hypothesis.
In contrast, the fairly strong correlation between central black hole size and galaxy size tends to argue for a very important role of central black holes in the galaxy formation process, because black holes only make up ca. 1% of a galaxy's mass.
The paper also makes notable observations about other aspects of spiral galaxy geometry.
We compare the apparent directions of rotation in the plane of the sky of active galactic nuclei (AGNs) and their host galaxies. The direction of rotation of the galaxy was inferred from the direction of the spiral arms, while the direction of rotation of the AGN was inferred from spectropolarimetry, where the change in relative polarization position angle (PA) across broad lines is believed to be caused by equatorial scattering. The numbers of co-rotating and counter-rotating AGNs are equal.
Studies of the relative position angles of radio jets have implied that there is a "zone of avoidance" where jets avoid being in the plane of disk galaxies. We point out that bi-conical narrow-line-region outflows also avoid the plane of the host galaxy.
The equal numbers of co-rotating and counter-rotating AGNs exclude the hypothesis that the "zone of avoidance" is due to a lack of large tilts of the black hole rotating axis relative to the host galaxy rotation axis. Our results imply that the relative orientations of spin axes are random, at least for the black hole mass range we consider.
We propose that changes in the broad-line polarization PA with wavelength that do not closely follow the predictions of the simple equatorial scattering model are a consequence of the scattering dust being clumpy. We note a couple of cases of possible changes in PA over several years, which, if real, could be due to motions of the dust clumps or changing anisotropy of the continuum emission.
Loren Gigi, C. Martin Gaskell, "The direction of rotation of supermassive black holes is unrelated to the direction of rotation of the host galaxy" arXiv:2607.06902 (July 8, 2026).
9 comments:
your thoughts about this
https://indico.cern.ch/event/1654737/contributions/7161458/attachments/3311293/5926155/hep2026_antonelli.pdf
Improving experiments is always good. The money quote on the work so far is:
"Run III Results Excess observed, 2.5 π local, 1.8(2) π global significance corresponding to mass ππ=16.9 πππ ππ£π = 5 × 10−4 Second excess present at ππ≅17.1 πππ and a coupling ππ£π , with a local (global) probability of ∼ 8% (40%) " So, consistent with no X17.
Run IV is suppose to reduce uncertainties enough to turn a statistically insignificant signal into a statistically significant signal (but not enough to reach the gold standard of 5 sigma for a discovery), if there really is a signal.
A dual excess about 200 keV apart is also weird and would suggest a pair of almost degenerate particles rather than a single new particle, if it is really a particle resonance.
We know that the X17 can't interact via the weak force, or it would show up in W and Z boson decays which it doesn't. It has to be electromagnetically neutral if it exists. There is really no plausible way that it could interact via the strong force. Way too strong to be a graviton, which also shouldn't have a massive carrier boson since it is unlimited in range.
So, it would have to be the dual carrier of a fifth force that doesn't interact with any of the other SM forces if it existed. We do have an example of the force with more than one carrier boson at more than one mass that is kind of close together (the weak force with the W and the Z).
17 ± 0.1 MeV is a mass with not a lot of background noise. Muons (105 MeV) are much more massive. Electrons (0.511 MeV) and neutrinos (less than 0.45-0.51 eV) are much less massive. The gap between the two peaks isn't about 40% of the electron mass (and is electromagnetically charged) so can't correspond to an electron although the uncertainties are big enough that it could almost fit an electron mass sized gap.
Hypothetical free up quarks (2.3 MeV) and down quarks (4.5 MeV) are much less massive and a hypothetical free strange quark is much too massive (95 MeV) But the neutral pion which is the lightest hadron, is much more massive (135 MeV) although with the benefit that it really is an emergent force carrying boson.
So, really, nothing in that mass range to provide background noise, which makes the low significance of the results so far more problematic. The lack of an estimated resonance width is also an issue. Is it supposed to be stable or meta-stable? Longer lived than a free neutron?
Still it seems much more likely to be a modeling error of the nuclear processes attributed to it, as those models are far from an exact science, rather than a pair of almost degenerate fundamental bosons. Lots of false alarms in recent history had a similar origin when they were ultimately figured out.
Also, definitely not a dark matter particle candidate.
Per the Wikipedia X17 particle entry:
"f X17 is a spin-1 particle, it likely possesses "chiral" or "axial-vector" couplings to quarks and leptons—similar to the Standard Model's weak force—to evade strict limits set by pion decay experiments . . . . An alternative theoretical approach argues that X17 is not a new fundamental particle belonging to a "dark sector" at all. Physicist Cheuk-Yin Wong has proposed that the 17 MeV signal represents a previously unobserved "confined state" of Quantum Electrodynamics (QED)—essentially an isoscalar QED meson." Neither of these hypotheses is well motivated or plausible.
QED binding energy would have to be 6 MeV to bind a down quark and an antidown quark, which seems high. The proton-neutron mass difference is 1.3 MeV and the QED binding energy in protons and neutrons is less than 6 MeV. Also, you'd expect annihilation and hadroniziation in what would basically be QED quarkonium for a very short lifetime and an explosive end.
thanks for reading it.
still a sharp peak exactly where the original ATOMKI Collaboration experiment 16.9 mev is still encouraging, and attempt to get to 5 sigma requires better noise to signal ratio which they are attempting.
The Run IV data needed to clarify
• Improve sensitivity (higher statistics and better control of systematics)
aiming at a factor of 2 error reduction
• New Micromegas tracker were installed to measure the absolute ee/????????
cross section allowing combined analysis
• Redundant beam parameter measurements also with TMM to the end
of the line for beam monitor
• Signal yield increased by a factor of ∼ 2.5 wrt Run III
"On the basis of the ongoing analysis of Run IV and during the test runs, we are currently evaluating the
possibilities to significantly increase the sensitivity of the experiment in future running campaign
(using lighter materials for target, reduce passive material in the tracker to mitigate multiple scattering)"
it sounds to me that Run IV is still seeing this signal, they just need to improve sensitivity to get to 5 sigma, perhaps in Run V
the initial results of Run IV is causing PADME is still investing solely in X17 with a list of proposals to get to 5 sigma in their next run.
also,
Physics > Instrumentation and Detectors
[Submitted on 17 Jun 2026]
Track and energy reconstruction algorithms for a time projection chamber with orthogonal fields
Martin VΓt VavΕΓk, Babar Ali, Hugo Natal da Luz, Olivier Rousselle, TomΓ‘Ε‘ SΓ½kora
In this work, we describe the development of track- and energy-reconstruc-tion algorithms for atypical Time Projection Chambers (TPCs) that will be used at the Institute of Experimental and Applied Physics, Czech Technical University in Prague, to search for the anomalous internal pair creation reported by the ATOMKI group. These chambers operate with an inhomogeneous toroidal magnetic field oriented orthogonally to the electric field; we therefore refer to them as Orthogonal-Field TPCs (OFTPCs). Although this configuration distorts the drift of ionization electrons and complicates the resulting electron and positron trajectories, it also offers several practical advantages. We present the most effective of several tested approaches, which employs a simulated ionization-electron drift map for track reconstruction and a Runge--Kutta-based fit for energy reconstruction. Using simulations, we demonstrate that -- under idealized conditions, namely an ideal charge readout with no amplification and no noise and with known initial track positions and directions -- it is possible to achieve a fitted Gaussian width (sigma) better than 1\% in relative energy for both electrons and positrons, after applying corrections for systematic effects that depend on the track parameters.
also, there have been newer papers that gravity is not a fundamental force but emergent, so apparently no gravitons
might have implications on theories that involve graviton-graviton interaction if gravitons don't exist and gravity isn't fundamental
I don't think emergent in this case implies it's a field without a particle.
Einstein Equations from Quantum Relative Entropy imply that gravity is not fundamental field - perhaps conflict with Deur graviton self interaction and string theory
Post a Comment