Abstracts of Interest
Selected by:
Hayden James
Abstract: 2503.06961
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Title:A new rotating black hole from the Newman-Janis algorithm
View PDF HTML (experimental)Abstract:We present a new rotating black hole solution to the Einstein equations as an extension of the Kerr spacetime. To derive this solution, we use the Newman-Janis algorithm as a mathematical tool that reduces a general rotating metric into a tractable form by applying simple physical requirements. Interestingly, the solution we found may not be uniquely characterized by asymptotic parameters such as mass, angular momentum, and charge, thereby challenging the no-hair theorem. We also analyze in detail how this additional characteristics (``hair") affects the thermodynamic properties of the black hole.
Abstract: 2503.07218
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Title:Cosmic Ray bubbles from nova super remnants and their contribution to local cosmic ray spectra
View PDF HTML (experimental)Abstract:Context: Several new phenomena have been surrounding the area of study of the repeating thermonuclear explosions called novae. For example, recurrent novae have been proven to be efficient cosmic ray hadronic accelerators thanks to the recent observations of RS Ophiuchi by different gamma-ray instruments. Novae have also demonstrated to have the ability to carve large cavities into the Interstellar Medium with parallelisms with the remnants of supernovae. We aim at calculating what is the effect of novae in their surrounding media and to which distances these effects dominate over the average quantities that are measured in the ISM. We calculate the filling factor of novae and their contribution to cosmic ray fluxes using cosmic ray propagation codes. To limit what is the atomic density of the Interstellar Medium (ISM) surrounding the region around RS Oph, we use Fermi-LAT observations of the region. The filling factor of novae in the Galaxy is not significant under all assumptions done in the paper. They do not dominate over the local cosmic ray fluxes, even at the lowest energies, for distances larger than a few parsec. The particle density of the ISM surrounding them is, however, very much modified, lowering it more than one order of magnitude with respect to galactic averages, confirming estimates done using other observatories. As a conclusion, even though at global galactic distances, novae do not seem to be dominating cosmic ray transport, they have the power to modify the conditions of their surrounding ISM over parsec distances.
Abstract: 2503.07277
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Title:Emulating the Non-Linear Matter Power-Spectrum in Mixed Axion Dark Matter Models
View PDF HTML (experimental)Abstract:In order to constrain ultra light dark matter models with current and near future weak lensing surveys we need the predictions for the non-linear dark matter power-spectrum. This is commonly extracted from numerical simulations or from using semi-analytical methods. For ultra light dark matter models such numerical simulations are often very expensive due to the need of having a very low force-resolution often limiting them to very small simulation boxes which do not contain very large scales. In this work we take a different approach by relying on fast, approximate $N$-body simulations. In these simulations, axion physics are only included in the initial conditions, allowing us to run a large number of simulations with varying axion and cosmological parameters. From our simulation suite we use machine learning tools to create an emulator for the ratio of the dark matter power-spectrum in mixed axion models - models where dark matter is a combination of CDM and axion - to that of $\Lambda$CDM. The resulting emulator only needs to be combined with existing emulators for $\Lambda$CDM to be able to be used in parameter constraints. We compare the emulator to semi-analytical methods, but a more thorough test to full simulations to verify the true accuracy of this approach is not possible at the present time and is left for future work.
Abstract: 2503.07531
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Title:Predicted Neutrino Signal Features of Core-Collapse Supernovae
View PDF HTML (experimental)Abstract:In this paper, we examine the neutrino signals from 24 initially non-rotating, three-dimensional core-collapse supernova (CCSN) simulations carried to late times. We find that not only does the neutrino luminosity signal encode information about each stage of the CCSN process, but that the monotonic dependence of the luminosity peak height with compactness enables one to infer the progenitor core structure from the neutrino signal. We highlight a systematic relationship between the luminosity peak height with its timing. Additionally, we emphasize that the total energy radiated in neutrinos is monotonic with progenitor compactness, and that the mean neutrino energy contains a unique spiral SASI signature for nonexploding, BH-forming models. We also find that neutrino emissions are not isotropic and that the anisotropy increases roughly with progenitor compactness. To assess the detectability of these neutrino signal features, we provide examples of the event rates for our models for the JUNO, DUNE, SK, and IceCube detectors using the SNEWPY software, and find that many of the trends in the luminosity signal can be detectable across several detectors and oscillation models. Finally, we discuss correlations between the radiated neutrino energy and the evolution of the gravitational-wave f-mode.
Abstract: 2503.07713
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Title:$ν$ limits from Super-Kamiokande on dark matter-electron scattering in the Sun
View PDF HTML (experimental)Abstract:Particle dark matter scattering on electrons in the Sun may gravitationally capture and self-annihilate inside it to neutrinos and anti-neutrinos, or other final states that in turn decay to them. Using up-to-date measurements by Super-Kamiokande of the fluxes of atmospheric electron-type and muon-type neutrinos, we set the most stringent limits on the electron scattering cross sections of dark matter down to about $10^{-40}-10^{-39}$ cm$^2$ over a mass range of 4$-$200 GeV. These outdo direct searches for dark matter-electron scattering and previously set limits at IceCube. We also derive corresponding reaches at Hyper-K, and show that atmospheric neutrino observations restricted to the direction of the Sun can improve sensitivities.
Abstract: 2503.07867
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Title:The Pierre Auger Observatory and Physics Beyond the Standard Mode
View PDF HTML (experimental)Abstract:The Pierre Auger Observatory, the world's largest cosmic ray detector, plays a pivotal role in exploring the frontiers of physics beyond the standard model of particle physics. By the observation of ultra-high energy cosmic rays, Auger provides critical insights into two major scenarios: super heavy dark matter and Lorentz invariance violation. Super heavy dark matter, hypothesized to originate in the early universe, offers a compelling explanation for the dark matter problem and is constrained by Auger through searches for photons and neutrinos resulting from its decay. Lorentz invariance violations, motivated by quantum gravity theories implying deviations from fundamental symmetries, are probed by Auger through alterations of the particle dispersion relation and the energy thresholds of their interactions with astrophysical photons backgrounds.
Abstract: 2503.08439
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Title:Testing the dark origin of neutrino masses with oscillation experiments
View PDF HTML (experimental)Abstract:The origin of neutrino masses remains unknown to date. One popular idea involves interactions between neutrinos and ultralight dark matter, described as fields or particles with masses $m_\phi \ll 10\,\mathrm{eV}$. Due to the large phase-space number density, this type of dark matter exists in coherent states and can be effectively described by an oscillating classical field. As a result, neutrino mass-squared differences undergo field-induced interference in spacetime, potentially generating detectable effects in oscillation experiments. We demonstrate that if $m_\phi\gg 10^{-14}\,\mathrm{eV}$, the mechanism becomes sensitive to dark matter density fluctuations, which suppresses the oscillatory behavior of flavor-changing probabilities as a function of neutrino propagation distance in a model-independent way, thereby ruling out this regime. Furthermore, by analyzing data from the Kamioka Liquid Scintillator Antineutrino Detector (KamLAND), a benchmark long-baseline reactor experiment, we show that the hypothesis of a dark origin for the neutrino masses is disfavored for $m_\phi \ll 10^{-14}\,\mathrm{eV}$, compared to the case of constant mass values in vacuum. This result holds at more than the 4$\sigma$ level across different datasets and parameter choices. The mass range $10^{-17}\,\mathrm{eV} \lesssim m_\phi \lesssim 10^{-14}\,\mathrm{eV}$ can be further tested in current and future oscillation experiments by searching for time variations (rather than periodicity) in oscillation parameters.
Abstract: 2503.08667
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Title:Extreme Jet Beaming Observed in Neutrino-Associated Blazars
View PDF HTML (experimental)Abstract:Bright blazars were found to be prominent neutrino sources, and a number of IceCube events were associated with them over recent years. A particularly strong observational connection is present between neutrinos and blazars with bright, Doppler-boosted, parsec-scale radio emission. In this work, we further explore the nature of this connection by examining the jet geometry and kinematics of neutrino-associated blazars. We find that these blazars demonstrate remarkably strong jet beaming, even compared to other radio-bright sources. Their Doppler and Lorentz factors are larger, and viewing angles are smaller than for other blazars in the complete uniformly selected MOJAVE sample. Observationally, this serves as yet another piece of evidence for blazars forming a major population of neutrino sources. The strong neutrino-beaming correlation indicates that high-energy neutrino velocity is predominantly oriented along the jet, and the original PeV-scale protons exhibit a relativistic bulk motion along the jet. It suggests that neutrino production happens not too close to the black hole, but rather at sub-parsec distances, where the jet is already accelerated.
Abstract: 2503.08787
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Title:Echoes of Self-Interacting Dark Matter from Binary Black Hole Mergers
View PDF HTML (experimental)Abstract:Dark matter (DM) environments around black holes (BHs) can influence their mergers through dynamical friction, causing gravitational wave (GW) dephasing during the inspiral phase. While this effect is well studied for collisionless dark matter (CDM), it remains unexplored for self-interacting dark matter (SIDM) due to the typically low DM density in SIDM halo cores. In this work, we show that SIDM models with a massive force mediator can support dense enough DM spikes, significantly affecting BH mergers and producing a distinct GW dephasing. Using ${N}$-body simulations, we analyze GW dephasing in binary BH inspirals within CDM and SIDM spikes. By tracking the binary's motion in different SIDM environments, we show that the Laser Interferometer Space Antenna (LISA) can distinguish DM profiles shaped by varying DM interaction strengths, revealing detailed properties of SIDM.
Abstract: 2503.09137
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Title:"Dark comet" 2005 VL$_1$ is unlikely to be the lost Soviet-era probe Venera 2
View PDF HTML (experimental)Abstract:Loeb & Cloete (2025) intriguingly suggest that the near-Earth object 2005 VL$_1$ could be the lost Soviet probe Venera 2. Here I evaluate the plausibility of such a claim against the available data. I have re-determined the orbit of 2005 VL$_1$ (including a non-gravitational acceleration component) using the astrometric observations retrieved from the Minor Planet Center (MPC) database. By propagating the orbit of 2005 VL$_1$ over the period of the Venera 2 mission, I compare this object's distance from the Earth and from Venus at the times of the probe's launch and flyby with Venus, respectively. My analysis, which takes into account realistic uncertainties on both the orbit of 2005 VL1 and the position of Venera 2, decisively rules out the proposed identification. My approach relies entirely on open-source software and publicly available data, and could represent a viable method to assess similar claims in the future.
Abstract: 2503.09295
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Title:Strong Field QED, Astrophysics, and Laboratory Astrophysics
View PDF HTML (experimental)Abstract:Astrophysical compact objects, such as magnetars, neutron star mergers, etc, have strong electromagnetic fields beyond the Schwinger field ($B_c = 4.4 \times 10^{13}\, {\rm G}$). In strong electric fields, electron-positron pairs are produced from the vacuum, gamma rays create electron-positron pairs in strong magnetic fields, and propagating photons experience vacuum refringence, etc. Astrophysical compact objects with strong electromagnetic fields open a window for probing fundamental physics beyond weak field QED. Ultra-intense lasers and high-energy charged particles may simulate extreme astrophysical phenomena.
Abstract: 2503.09685
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Title:Sub-GeV Dark Matter Direct Detection with Neutrino Observatories
View PDF HTML (experimental)Abstract:We present a new technique for sub-GeV dark matter (DM) searches and a new use of neutrino observatories. DM-electron scattering can excite or ionize target molecules in the observatory, which then produce light that can be detected by its photomultiplier tubes (PMTs). While individual DM scatterings are undetectable, the aggregate rate from many independent scatterings can be isolated from the total PMT dark rate using the expected DM annual modulation. We showcase this technique with the example of JUNO, a 20,000 ton scintillator detector, showing that its sensitivity in some mass ranges exceeds all other techniques and reaches key particle-theory targets.
Abstract: 2503.09804
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Title:Calculation of Dark Matter as a Feature of Space-Time
View PDFAbstract:We derive the first analytical formula for the density of "Dark Matter" (DM) at all length scales, thus also for the rotation curves of stars in galaxies, for the baryonic Tully-Fisher relation and for planetary systems, from Einstein's equations (EE) and classical approximations, in agreement with observations. DM is defined in Part I as the energy of the coherent gravitational field of the universe, represented by the additional equivalent ordinary matter (OM), needed at all length scales, to explain classically, with inclusion of the OM, the observed coherent gravitational field. Our derivation uses both EE and the Newtonian approximation of EE in Part I, to describe semi-classically in Part II the advection of DM, created at the level of the universe, into galaxies and clusters thereof. This advection happens proportional with their own classically generated gravitational field g, due to self-interaction of the gravitational field. It is based on the universal formula rD=lgg'g' for the density rD of DM advected into medium and lower scale structures of the observable universe, where l is a universal constant fixed by the Tully-Fisher relations. Here g' is the gravitational field of the universe; g' is in main part its own source, as implied in Part I from EE. We start from a simple electromagnetic analogy that helps to make the paper generally accessible. This paper allows for the first time the exact calculation of DM in galactic halos and at all levels in the universe, based on EE and Newtonian approximations, in agreement with observations.
Abstract: 2503.10795
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Title:A Hierarchical Shock Model of Ultra-High-Energy Cosmic Rays
View PDF HTML (experimental)Abstract:We propose that a hierarchical shock model$\unicode{x2014}$including supernova remnant shocks, galactic wind termination shocks, and accretion shocks around cosmic filaments and galaxy clusters$\unicode{x2014}$can naturally explain the cosmic ray spectrum from ~1 GeV up to ~200 EeV. While this framework applies to the entire cosmic ray spectrum, in this work, we focus on its implications for ultra-high-energy cosmic rays (UHECRs). We perform a hydrodynamic cosmological simulation to investigate the power processed at shocks around clusters and filaments. The downstream flux from nearby shocks around the local filament accounts for the softer, lower-energy extragalactic component around the ankle, and the upstream escaping flux from nearby clusters accounts for the transition to a hard spectral component at the highest energies. This interpretation is in agreement with UHECR observations. We suggest that a combination of early-Universe galactic outflows, cosmic ray streaming instabilities, and a small-scale turbulent dynamo can increase magnetic fields enough to attain the required rigidities. Our simulation suggests that the available volume-averaged power density of accretion shocks exceeds the required UHECR luminosity density by three orders of magnitude. We show that microgauss magnetic fields at these shocks could explain both the origin of UHECRs and the as-yet unidentified source of the diffuse radio synchrotron background below 10 GHz. The shock-accelerated electrons produce a hard radio background without overproducing diffuse inverse Compton emission. These results motivate further observational tests with upcoming facilities to help distinguish accretion shocks from other UHECR sources.
This page created: Thu 20 Mar 10:53:58 ACDT 2025 by Hayden James
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