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Theoretical Astroparticle Physics

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Theoretical Astroparticle Physics Theoretical Astroparticle Physics Contents 1. Topics 1339 2. Participants 1341 2.1. ICRANetparticipants. 1341 2.2. Pastcollaborators . 1341 2.3. Ongoingcollaborations. 1342 2.4. Students ............................... 1342 3. Brief description 1343 3.1. Electron-positronplasma. 1343 3.1.1. Thermalization of mildly relativistic plasma with pro- tonloading ......................... 1343 3.1.2. Pairplasmarelaxationtimescales. 1344 3.1.3. HydrodynamicphaseofGRBsources . 1345 3.2. Neutrinosincosmology . 1345 3.2.1. Massive neutrino and structure formation . 1347 3.2.2. CellularstructureoftheUniverse . 1347 3.2.3. LeptonasymmetryoftheUniverse . 1348 3.2.4. MassVaryingNeutrinos . 1348 3.3. IndirectDetectionofDarkMatter . 1349 3.4. AlternativeCosmologicalModels. 1350 4. Publications 1353 4.1. Publicationsbefore2005 . 1353 4.2. Publications(2005-2008) . 1356 4.3. Publications(2009) . 1362 4.4. Invitedtalksatinternationalconferences . 1365 5. APPENDICES 1369 A. Pair plasma relaxation timescales 1371 B.HydrodynamicphaseofGRBsources 1379 B.1. Introduction ............................. 1379 B.2. Kineticandhydrodynamicalphases . 1381 B.3. Physicalevolution. 1383 1335 Contents B.4. Results ................................ 1385 B.4.1. Constant baryonic distribution profile . 1385 B.4.2. c)Hybridprofile . 1387 B.5. Conclusions ............................. 1389 B.6. Numericalapproach . 1390 B.6.1. Finitedifferenceformofequations . 1392 B.6.2. Numericalissues . 1393 B.7. test .................................. 1395 B.7.1. a)Piran’sprofile . 1395 C. Cosmological structure formation 1397 C.0.2. TheCosmologicalPrinciple . 1397 C.1. Two-pointCorrelationFunction . 1399 C.1.1. ObservedGalaxyDistribution . 1400 C.1.2. PowerLawClusteringandFractals . 1401 D.MassivedegenerateneutrinosinCosmology 1403 D.1. Neutrinodecoupling . 1403 D.2. Theredshiftedstatistics . 1404 D.3. Energydensityofneutrinos . 1405 D.3.1. Neutrinomass . 1406 D.3.2. Chemicalpotential . 1407 D.3.3. Neutrinooscillations . 1408 D.4. TheJeansmassofneutrinos . 1408 D.5. Joint constraints on the lepton asymmetry of the Universe and neutrino mass from the Wilkinson Microwave Anisotropy Probe1411 D.5.1. Introduction. 1411 D.5.2. Motivationforthiswork. 1414 D.5.3. Basicformulae . 1415 D.5.4. Effectofanon-nullchemicalpotential . 1419 D.5.5. Method............................ 1421 D.5.6. Resultsanddiscussion . 1424 D.5.7. Conclusionsandperspectives . 1428 D.6. Model independent constraints on mass-varying neutrino sce- narios................................. 1431 D.6.1. Introduction. 1431 D.6.2. Mass-varyingneutrinos . 1433 D.6.3. Modelindependentapproach. 1435 D.6.4. ResultsandDiscussion. 1442 D.6.5. Concludingremarks . 1448 1336 Contents E. Indirect Detection of Dark Matter 1455 E.1. Boosting the WIMP annihilation through the Sommerfeld en- hancement .............................. 1455 E.1.1. TheSommerfeldenhancement . 1456 E.1.2. Theleptonicbranchingratio . 1461 E.1.3. CDM substructure: enhancing the Sommerfeld boost . 1463 E.1.4. Discussion. .. .. .. .. .. .. .. 1465 E.2. Constraining the dark matter annihilation cross-section with Cherenkov telescope observations of dwarf galaxies . 1468 E.2.1. Introduction. 1468 E.2.2. γ-ray flux from Dark Matter annihilation in Draco and Sagittarius .......................... 1470 E.2.3. Comparisonwiththeexperimentaldata . 1480 E.2.4. Conclusions . 1485 F. Alternative Cosmological Models 1489 Bibliography 1493 1337 1. Topics Electron-positron plasma • – Thermalization of mildly relativistic plasma with proton loading – Relaxation timescales in the pair plasma – Hydrodynamic phase of GRB sources Neutrinos in cosmology • – Massive neutrino and structure formation – Cellular structure of the Universe – Lepton asymmetry of the Universe – Mass Varying Neutrinos Indirect Detection of Dark Matter • Alternative Cosmological Models • 1339 2. Participants 2.1. ICRANet participants Carlo Luciano Bianco • Massimiliano Lattanzi • Remo Ruffini • Gregory Vereshchagin • She-Sheng Xue • 2.2. Past collaborators Marco Valerio Arbolino (DUNE s.r.l., Italy) • Andrea Bianconi (INFN Pavia, Italy) • Neta A. Bahcall (Princeton University, USA) • Daniella Calzetti (University of Massachusets, USA) • Jaan Einasto (Tartu Observatory, Estonia) • Roberto Fabbri (University of Firenze, Italy) • Long-Long Feng (University of Science and Technology of China, China) • Jiang Gong Gao (Xinjiang Institute of Technology, China) • Mauro Giavalisco (University of Massachusets, USA) • Gabriele Ingrosso (INFN, University of Lecce, Italy) • Yi-peng Jing (Shanghai Astronomical Observatory, China) • Hyung-Won Lee (Inje University, South Korea) • Marco Merafina (University of Rome “Sapienza”, Italy) • Houjun Mo (University of Massachusetts, USA) • 1341 2. Participants Enn Saar (Tartu Observatory, Estonia) • Jay D. Salmonson (Livermore Lab, USA) • Luis Alberto Sanchez (National University Medellin, Colombia) • Costantino Sigismondi (ICRA and University of Rome ”La Sapienza”, • Italy) Doo Jong Song (Korea Astronomy Observatory, South Korea) • Luigi Stella (Astronomical Observatory of Rome, Italy) • William Stoeger (Vatican Observatory, University of Arizona USA) • Sergio Taraglio (ENEA, Italy) • Gerda Wiedenmann (MPE Garching, Germany) • Jim Wilson (Livermore Lab, USA) • Roustam Zalaletdinov (Tashkent University, Uzbekistan) • 2.3. Ongoing collaborations Alexey Aksenov (ITEP, Russia) • Valeri Chechetkin (Keldysh Institute, Russia) • Urbano Franc¸a (Instituto de F´ısica Corpuscular, Valencia, Spain) • Julien Lesgourgues (CERN, Theory Division, Geneva, Switzerland) • Alessandro Melchiorri (Univ. “Sapienza” di Roma, Italy) • Lidia Pieri (Institute d’Astrophysique, Paris, France) • Sergio Pastor (Instituto de F´ısica Corpuscolar, Valencia, Spain) • Joseph Silk (Oxford University, UK) • 2.4. Students Gustavo de Barros (IRAP PhD, Brazil) • Luis Juracy Rangel Lemos (IRAP PhD, Brazil) • Stefania Pandolfi (IRAP PhD, Italy) • Ivan Siutsou (IRAP PhD, Belarus) • 1342 3. Brief description Astroparticle physics is a new field of research emerging at the intersection of particle physics, astrophysics and cosmology. Theoretical development in these fields is mainly triggered by the growing amount of experimental data of unprecedented accuracy, coming both from the ground based laboratories and from the dedicated space missions. 3.1. Electron-positron plasma Electron-positron plasma is of interest in many fields of astrophysics, e.g. in the early universe, gamma-ray bursts, active galactic nuclei, the center of our Galaxy, hypothetical quark stars. It is also relevant for the physics of ultrain- tense lasers and thermonuclear reactions. We study some properties of dense and hot electron-positron plasmas. In particular, we are interested in the is- sues of its creation and relaxation, its kinetic properties and hydrodynamic description, baryon loading, transition to transparency and radiation from such plasmas. Two completely different states exist for electron-positron plasma: opti- cally thin and optically thick. Optically thin pair plasma may exist in active galactic nuclei and in X-ray binaries. The theory of relativistic optically thin nonmagnetic plasma and especially its equilibrium configurations was es- tablished in the 80s by Svensson, Lightman, Gould and others. It was shown that relaxation of the plasma to some equilibrium state is determined by a dominant reaction, e.g. Compton scattering or bremsstrahlung. Developments in the theory of gamma ray bursts from one side, and ob- servational data from the other side, unambiguously point out on existence of optically thick pair dominated non-steady phase in the beginning of for- mation of GRBs. The spectrum of radiation from optically thick plasma is assumed to be thermal. However, in such a transient phenomena as gamma- ray bursts there could be not enough time for the plasma to relax into equi- librium. 3.1.1. Thermalization of mildly relativistic plasma with proton loading One of crucial assumptions adopted in the literature on gamma-ray bursts (Ruffini et al. (1999),Ruffini et al. (2000)) is that initial state of the pair plasma, 1343 3. Brief description formed in the source of the gamma-ray burst is supposed to be thermal, with equal temperature of pairs and photons. This assumption was ana- lyzed by Aksenov et al. (2007),Aksenov et al. (2008). The electron-positron- photon plasma was assumed to be homogeneous and isotropic, in the ab- sence of magnetic fields, with average energy per particle bracketing electron rest mass, in the range 0.1MeV . ǫ . 10MeV. Relativistic Boltzmann equa- tions were solved numerically for pairs and photons, starting from arbitrary initial configurations described by the corresponding distribution functions. All binary and triple collisions were accounted for, by the corresponding col- lisional integrals. Proton loading of electron-positron plasma was considered byAksenov et al. (2009c) (2009). This paper systematically presents details of the computa- tional scheme used by Aksenov et al. (2007), as well as generalizes the treat- ment, considering proton loading of the pair plasma. When proton loading is large, protons thermalize first by proton-proton scattering, and then with the electron-positron-photon plasma by proton-electron scattering. In the oppo- site case of small proton loading proton-electron scattering dominates over proton-proton one. Thus in all cases the plasma, even with proton admix- 11 ture, reaches thermal equilibrium configuration on a timescale t < 10− sec. We show that it is crucial to account for not only binary
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