| 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. |
- Di Bernardo, Giuseppe, et al.
(författare)
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“Cosmic Ray Electrons, Positrons and the Synchrotron emission of the Galaxy: consistent analysis and implications”
- 2013
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516 .- 1475-7516. ; 2013:3
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Tidskriftsartikel (refereegranskat)abstract
- A multichannel analysis of cosmic ray electron and positron spectra and of the diffuse synchrotron emission of the Galaxy is performed by using the DRAGON code. This study is aimed at probing the interstellar electron source spectrum down to E ~ 1 GeV and at constraining several propagation parameters. We find that above 4 GeV the electron source spectrum is compatible with a power-law of index -2.5. Below 4 GeV instead it must be significantly suppressed and the total lepton spectrum is dominated by secondary particles. The positron spectrum and fraction measured below a few GeV are consistently reproduced only within low reacceleration models. We also constrain the scale-height zt of the cosmic-ray distribution using three independent (and, in two cases, original) arguments, showing that values of z_t < 2 kpc are excluded. This result may have strong implications for particle dark matter searches.
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| 3. |
- Gaggero, Daniele, 1982, et al.
(författare)
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PAMELA and AMS-02 positron and electron spectra are reproduced by three-dimensional cosmic-ray modeling
- 2014
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Ingår i: Physical Review D. Particles and fields. - 0556-2821. ; 89:8
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Tidskriftsartikel (refereegranskat)abstract
- The PAMELA collaboration recently released the e+ absolute spectrum between 1 and 300 GeV in addition to the positron fraction and the e− spectrum previously measured in the same period. We use the newly developed three-dimensional upgrade of the dragon package to model those data. This code allows us to consider a realistic spiral-arm source distribution in the Galaxy, which impacts the high-energy shape of the propagated spectra. At low energy we treat solar modulation with the HelioProp code and compare its results with those obtained using the usual force-field approximation. We show that all PAMELA data sets can be consistently, and accurately, described in terms of a standard background on top of which a charge symmetric e++e− extra component with harder injection spectrum is added; this extra contribution is peaked at ∼1–10 TeV and may originate from a diffuse population of sources located in the Galactic arms. For the first time, we compute the energy required to sustain such a relevant positron flux in the Galaxy, finding that it is naturally compatible with an astrophysical origin. We considered several reference propagation setups; we find that models with a low (or null) reacceleration—tuned against light nuclei data—nicely describe both PAMELA leptonic and hadronic data with no need to introduce a low-energy break in the proton and Helium spectra, as it would be required for high reacceleration models. We also compare our models with the preliminary e− and e+ absolute spectra recently measured by AMS-02. We find that those data, differently from what is inferred from the positron fraction alone, favor a high energy cutoff ∼10 TeV of the extra component if this is uniquely generated in the Galactic arms. A lower cutoff may be allowed if a relevant contribution from powerful e−+e+ nearby accelerators (e.g., one or few pulsars) is invoked.
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| 4. |
- Gaggero, Daniele, 1981, et al.
(författare)
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“Three-Dimensional Model of Cosmic-Ray Lepton Propagation Reproduces Data from the Alpha Magnetic Spectrometer on the International Space Station”
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:2
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Tidskriftsartikel (refereegranskat)abstract
- We study the compatibility of Alpha Magnetic Spectrometer (AMS-02) data on the cosmic-ray (CR) positron fraction with data on the CR electron and positron spectra provided by PAMELA and Fermi LAT. We do that in terms of a novel propagation model in which sources are distributed in spiral arm patterns in agreement with astrophysical observations. While former interpretations assumed an unrealistically steep injection spectrum for astrophysical background electrons, the enhanced energy losses experienced by CR leptons due to the larger average source distance from Earth allow us to reproduce the data with harder injection spectra as expected in a shock acceleration scenario. Moreover, we show that in this approach, and accounting for AMS-02 results, the contribution of nearby accelerators to the fluxes at very high energy can be significantly reduced, thus avoiding any tension with anisotropy upper limits.
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