| 1. |
- Barack, Leor, et al.
(författare)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Forskningsöversikt (refereegranskat)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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| 2. |
- Bartsch, Adam, et al.
(författare)
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Head impact doses and 'no-go' deficits in Olympic and Non-Olympic sport athletes
- 2021
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Konferensbidrag (refereegranskat)abstract
- Background: The relationship between head impact dose andobservable functional deficits remains unclear. While studieshave almost exclusively examined American football athletes,in Olympic athletes there are almost no data that explore thisrelationship.Objective: We aimed to use an impact monitoring mouthguard(IMM) to quantify head impact doses in Olympic and non-Olympic Sports, identifying high-energy impacts on video as‘No-go’ per the NFL protocol.Design: Retrospective meta-analysis from American football,basketball, boxing, ice hockey, karate, lacrosse, mixed martialarts, rugby, tae-kwon-do, soccer.Setting: Sporting field.Patients (or Participants): 4500 impacts over 800 player-games.Interventions (or Assessment of Risk Factors): Impact doseswhere the athlete was observed as ‘no-go’.Main Outcome Measurements: Kinetic energy transfer (KE),risk-weighted exposure (RWE), peak scalar linear acceleration(PLA), peak scalar linear velocity (PLV), peak scalar angularacceleration (PAA), peak scalar angular velocity (PAV), impactlocation, impact direction, ‘No-go’ status.Results: The median KE, RWE, PLA, PAA, PLV and PAV was 5J, 0.0002, 20 g, 1500 rad/s2, 10 rad/s and 1.5 m/s, respectively.American football athletes sustained the highest energyimpact doses, boxers and mixed-martial artists sustained thehighest cumulative dose for a day of competition. Ice hockeyhad the highest rate of ‘no-go’ impacts versus total impactscollected. Karate had the highest rotational kinematics. Of thenine (9) highest energy impacts to the side and rear of thehead, all were ‘no-go’ impacts. Of the top eight (8) highestenergy impacts to the front of the head, none were ‘no-go’impacts.Conclusions: ‘No-go’ observations occurred in high energyimpact doses to the rear and the sides of the head, while similarimpact doses to the forehead seemed tolerable. ProspectiveOlympic athlete impact monitoring could help identify riskyexposures.
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| 3. |
- Calore, Francesca, et al.
(författare)
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3D template-based Fermi-LAT constraints on the diffuse supernova axion-like particle background
- 2022
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 105:6
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Tidskriftsartikel (refereegranskat)abstract
- Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae (SNe); hence, the cumulative signal from all past supernova (SN) events can create a diffuse flux peaked at energies of about 25 MeV. We improve upon the modeling of the ALPs flux by including a set of CC SN models with different progenitor masses, as well as the effects of failed CC SNe, which yield the formation of black holes instead of explosions. Relying on the coupling strength of ALPs to photons and the related Primakoff process, the diffuse SN ALP flux is converted into gamma rays while traversing the magnetic field of the Milky Way. The spatial morphology of this signal is expected to follow the shape of the Galactic magnetic field lines. We make use of this via a template-based analysis that utilizes 12 years of Fermi-LAT data in the energy range from 50 MeV to 500 GeV. In our benchmark case of the realization of astrophysical and cosmological parameters, we find an upper limit of gaγ≲3.76×10−11 GeV−1 at a 95% confidence level for ma≪10−11 eV, while we find that systematic deviations from this benchmark scenario induce an uncertainty as large as about a factor of two. Our result slightly improves the CAST bound, while still being a factor of six (baseline scenario) weaker than the SN1987A gamma-ray burst limit.
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| 4. |
- Calore, Francesca, et al.
(författare)
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Uncovering axionlike particles in supernova gamma-ray spectra
- 2024
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 109:4
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Tidskriftsartikel (refereegranskat)abstract
- A future Galactic supernova (SN) explosion can lead to a gamma-ray signal induced by ultralight axionlike particles (ALPs) thermally produced in the SN core and converted into high-energy photons in the Galactic magnetic field. The detection of such a signal is in the reach of the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope. The observation of gamma-ray emission from a future SN has a sensitivity to gaγ≳4×10−13 GeV−1 for a SN at fiducial distance of 10 kpc and would allow us to reconstruct the ALP-photon coupling within a factor of ∼2, mainly due to the uncertainties on the modeling of the Galactic magnetic field.
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| 5. |
- Caron, Sascha, et al.
(författare)
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Mind the gap: the discrepancy between simulation and reality drives interpretations of the Galactic Center Excess
- 2023
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2023:6
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Tidskriftsartikel (refereegranskat)abstract
- The Galactic Center Excess (GCE) in GeV gamma rays has been debated for over a decade, with the possibility that it might be due to dark matter annihilation or undetected point sources such as millisecond pulsars (MSPs). This study investigates how the gamma-ray emission model (γEM) used in Galactic center analyses affects the interpretation of the GCE's nature. To address this issue, we construct an ultra-fast and powerful inference pipeline based on convolutional Deep Ensemble Networks. We explore the two main competing hypotheses for the GCE using a set of γEMs with increasing parametric freedom. We calculate the fractional contribution (f src) of a dim population of MSPs to the total luminosity of the GCE and analyze its dependence on the complexity of the γEM. For the simplest γEM, we obtain f src = 0.10 ± 0.07, while the most complex model yields f src = 0.79 ± 0.24. In conclusion, we find that the statement about the nature of the GCE (dark matter or not) strongly depends on the assumed γEM. The quoted results for f src do not account for the additional uncertainty arising from the fact that the observed gamma-ray sky is out-of-distribution concerning the investigated γEM iterations. We quantify the reality gap between our γEMs using deep-learning-based One-Class Deep Support Vector Data Description networks, revealing that all employed γEMs have gaps to reality. Our study casts doubt on the validity of previous conclusions regarding the GCE and dark matter, and underscores the urgent need to account for the reality gap and consider previously overlooked “out of domain” uncertainties in future interpretations.
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| 6. |
- Eckner, Christopher, et al.
(författare)
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Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre
- 2022
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Ingår i: 37th International Cosmic Ray Conference (ICRC2021) - GAI - Gamma Ray Indirect. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 395
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Konferensbidrag (refereegranskat)abstract
- High-energy gamma rays are promising tools to constrain or reveal the nature of dark matter, in particular Weakly Interacting Massive Particles. Being well into its pre-construction phase, the Cherenkov Telescope Array (CTA) will soon probe the sky in the 20 GeV - 300 TeV energy range. Thanks to its improved energy and angular resolutions as well as significantly larger effective area when compared to the current generation of Cherenkov telescopes, CTA is expected to probe heavier dark matter, with unprecedented sensitivity, reaching the thermal annihilation cross-section at 1 TeV. This talk will summarise the planned dark matter search strategies with CTA, focusing on the signal from the Galactic centre. As observed with the Fermi LAT at lower energies, this region is rather complex and CTA will be the first ground-based observatory sensitive to the large scale diffuse astrophysical emission from that region. We report on the collaboration effort to study the impact of such extended astrophysical backgrounds on the dark matter search, based on Fermi-LAT data in order to guide our observational strategies, taking into account various sources of systematic uncertainty. © Copyright owned by the author(s) under the terms of the Creative Commons.
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| 7. |
- Müller, Eike, 1995-, et al.
(författare)
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Investigating the gamma-ray burst from decaying MeV-scale axion-like particles produced in supernova explosions
- 2023
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Ingår i: Journal of Cosmology and Astroparticle Physics. - 1475-7516. ; 2023:07
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the characteristics of the gamma-ray signal following the decay of MeV-scale Axion-Like Particles (ALPs) coupled to photons which are produced in a Supernova (SN) explosion. This analysis is the first to include the production of heavier ALPs through the photon coalescence process, enlarging the mass range of ALPs that could be observed in this way and giving a stronger bound from the observation of SN 1987A. Furthermore, we present a new analytical method for calculating the predicted gamma-ray signal from ALP decays. With this method we can rigorously prove the validity of an approximation that has been used in some of the previous literature, which we show here to be valid only if all gamma rays arrive under extremely small observation angles (i.e. very close to the line of sight to the SN). However, it also shows where the approximation is not valid, and offers an efficient alternative to calculate the ALP-induced gamma-ray flux in a general setting when the observation angles are not guaranteed to be small. We also estimate the sensitivity of the Fermi Large Area Telescope (Fermi-LAT) to this gamma-ray signal from a future nearby SN and show that in the case of a non-observation the current bounds on the ALP-photon coupling gaγ are strengthened by about an order of magnitude. In the case of an observation, we show that it may be possible to reconstruct the product gaγ2ma, with ma the mass of the ALP.
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| 8. |
- Panes, Boris, et al.
(författare)
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Identification of point sources in gamma rays using U-shaped convolutional neural networks and a data challenge
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 656, s. A62-
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Tidskriftsartikel (refereegranskat)abstract
- Context. At GeV energies, the sky is dominated by the interstellar emission from the Galaxy. With limited statistics and spatial resolution, accurately separating point sources is therefore challenging. Aims. Here we present the first application of deep learning based algorithms to automatically detect and classify point sources from gamma-ray data. For concreteness we refer to this approach as AutoSourceID. Methods. To detect point sources, we utilized U-shaped convolutional networks for image segmentation and k-means for source clustering and localization. We also explored the Centroid-Net algorithm, which is designed to find and count objects. Using two algorithms allows for a cross check of the results, while a combination of their results can be used to improve performance. The training data are based on 9.5 years of exposure from The Fermi Large Area Telescope (Fermi-LAT) and we used source properties of active galactic nuclei (AGNs) and pulsars (PSRs) from the fourth Fermi-LAT source catalog in addition to several models of background interstellar emission. The results of the localization algorithm are fed into a classification neural network that is trained to separate the three general source classes (AGNs, PSRs, and FAKE sources). Results. We compared our localization algorithms qualitatively with traditional methods and find them to have similar detection thresholds. We also demonstrate the robustness of our source localization algorithms to modifications in the interstellar emission models, which presents a clear advantage over traditional methods. The classification network is able to discriminate between the three classes with typical accuracy of similar to 70%, as long as balanced data sets are used in classification training. We published online our training data sets and analysis scripts and invite the community to join the data challenge aimed to improve the localization and classification of gamma-ray point sources.
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| 9. |
- Ravensburg, Eike, 1995-, et al.
(författare)
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Constraining MeV-scale axionlike particles with Fermi-LAT observations of SN 2023ixf
- 2024
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 109:2
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Tidskriftsartikel (refereegranskat)abstract
- The Fermi-LAT observations of SN 2023ixf, a type II supernova in the nearby Pinwheel Galaxy, Messier 101 (M101), presents us with an excellent opportunity to constrain MeV-scale axionlike particles (ALPs). By examining the photon decay signature from heavy ALPs that could be produced in the explosion, the existing constraints on the ALP-photon coupling can be improved, under optimistic assumptions, by up to a factor of ∼2 for masses ma≲3 MeV. Under very conservative assumptions, we find a bound that is slightly weaker than the existing ones for ma≲0.5 MeV. The exact reach of these searches depends mostly on properties of the SN progenitor. This study demonstrates the relevance of core-collapse supernovae, also beyond the Magellanic Clouds, as probes of fundamental physics.
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