High Energy Neutrinos: Sources and Fluxes

We discuss briefly the potential sources of high energy astrophysical neutrinos and show estimates of the neutrino fluxes that they can produce. A special attention is paid to the connection between the highest energy cosmic rays and astrophysical neutrinos.Comment: 7 pages, 2 figures, submitted to the Proceedings of TAUP 2005 workshop, corrected left panel of figure

On some problems of gamma-astronomy

Gamma ray emissions from young supernova remnants are discussed and calculated. The positron annihilation line is also calculated. Decay of charged pions in remnants cause generation of high energy neutrinos. This emission of neutrinos is reviewed. The CR origin and gamma emission from Magellanic clouds help to establish the intensity gradient in the galaxy. This gamma astronomical data is briefly discussed

Higgs-inspired corrections to the RG flow in the finite-temperature 3D Georgi-Glashow model and its SU(N)-generalization

The Berezinsky-Kosterlitz-Thouless (BKT) RG flow in the ensemble of monopoles existing in the finite-temperature (2+1)D Georgi-Glashow model is explored in the regime when the Higgs field is not infinitely heavy, but its mass is rather of the same order of magnitude as the mass of the W-boson. The corrections to the standard RG flow are derived to the leading order in the inverse mass of the Higgs boson. According to the obtained RG equations, the scaling of the free-energy density in the critical region and the value of the critical temperature of the phase transition are found to be unaffected by the finiteness of the Higgs-boson mass. The evolution of the Higgs mass itself is also investigated and shown to be rather weak, that enables one to treat this parameter as a constant. The same analysis is further performed in the SU(N)-case at N>2, where the RG invariance is demonstrated to hold only approximately, in a certain sense. Modulo this approximation, the critical behaviour of the SU(N)-model turns out to be identical to that of the SU(2)-one.Comment: 12 pages, LaTeX2e, no figure

Signatures of Topological Defects

We argue that due to various restrictions cosmic strings and monopole-string networks are not likely to produce the observed flux of ultra-high energy cosmic rays (UHECR). Among the topological defects studied so far, the most promising UHECR sources are necklaces and monopolonia. Other viable sources which are similar to topological defects are relic superheavy particles. All these sources have an excess of pions (and thus photons) over nucleons at production. We demonstrate that in the case of necklaces the diffuse proton flux can be larger than photon flux, due to absorption of the latter on radiobackground, while monopolonia and relic particles are concentrated in the Galactic halo, and the photon flux dominates. Another signature of the latter sources is anisotropy imposed by asymmetric position of the sun in the Galactic halo. In all cases considered so far, including necklaces, photons must be present in ultra-high energy radiation observed from topological defects, and experimental discrimination between photon-induced and proton-induced extensive air showers can give a clue to the origin of ultra-high energy cosmic rays.Comment: version accepted for publication in Phys. Rev. D. No changes in the conclusions and in figure

Primordial pairing and binding of superheavy charge particles in the early Universe

Primordial superheavy particles, considered as the source of Ultra High Energy Cosmic Rays (UHECR) and produced in local processes in the early Universe, should bear some strictly or approximately conserved charge to be sufficiently stable to survive to the present time. Charge conservation makes them to be produced in pairs, and the estimated separation of particle and antiparticle in such pair is shown to be in some cases much smaller than the average separation determined by the averaged number density of considered particles. If the new U(1) charge is the source of a long range field similar to electromagnetic field, the particle and antiparticle, possessing that charge, can form primordial bound system with annihilation timescale, which can satisfy the conditions, assumed for this type of UHECR sources. These conditions severely constrain the possible properties of considered particles.Comment: Latex, 4 pages. The final version to appear in Pis'ma ZhETF (the conditions for the primordial binding are specified, some refs added

High Energy Cosmic Rays from Local GRBs

We have developed a model that explains cosmic rays with energies E between \~0.3 PeV and the energy of the second knee at E_2 ~ 3*10^{17} eV as originating from a recent Galactic gamma-ray burst (GRB) that occurred ~1 Myr ago within 1 kpc from Earth. Relativistic shocks from GRBs are assumed to inject power-law distributions of cosmic rays (CRs) to the highest energies. Diffusive propagation of CRs from the local GRB explains the CR spectrum near and above the first knee at E_1 ~ 3*10^{15} eV. The first and the second knees are explained as being directly connected with the injection of plasma turbulence in the interstellar medium on a ~1 pc and ~100 pc scales, respectively. Transition to CRs from extragalactic GRBs occurs at E > E_2. The origin of the ankle in the CR spectrum at E ~ 4*10^{18} eV is due to photopair energy losses of UHECRs on cosmological timescales, as also suggested by Berezinsky and collaborators. Any significant excess flux of extremely high energy CRs deviating from the exponential cutoff behavior at E> E_{GZK} = 6*10^{19} eV would imply a significant contribution due to recent GRB activity on timescales t < 10^8 yrs from local extragalactic sources within ~10 Mpc.Comment: 10 pages, 5 figures; to appear in the Proceedings of the Aspen2005 Workshop ``Physics at the End of the Galactic Cosmic Ray Spectrum'' (Aspen, April 2005

Electroweak jet cascading in the decay of superheavy particles

We study decays of superheavy particles $X$ into leptons. We show that they initiate cascades similar to QCD parton jets, if m_X\gsim 10^6 GeV. Electroweak cascading is studied and the energy spectra of the produced leptons are calculated in the framework of a broken SU(2) model of weak interactions. As application, important for the Z-burst model for ultrahigh energy cosmic rays, we consider decays of superheavy particles coupled on tree-level only to neutrinos and derive stringent limit for these decays from the observed diffuse extragalactic $\gamma$-ray flux.Comment: 4 pages, 1 eps figur

Method to extract the primary cosmic ray spectrum from very high energy gamma-ray data and its application to SNR RX J1713.7-3946

Supernova remnants are likely to be the accelerators of the galactic cosmic rays. Assuming the correctness of this hypothesis, we develop a method to extract the parent cosmic ray spectrum from the VHE gamma ray flux emitted by supernova remnants (and other gamma transparent sources). Namely, we calculate semi-analytically the (inverse) operator which relates an arbitrary gamma ray flux to the parent cosmic ray spectrum, without relying on any theoretical assumption about the shape of the cosmic ray and/or photon spectrum. We illustrate the use of this technique by applying it to the young SNR RX J1713.7-3946 which has been observed by H.E.S.S. experiment during the last three years. Specific implementations of the method permit to use as an input either the parameterized VHE gamma ray flux or directly the raw data. The possibility to detect features in the cosmic rays spectrum and the error in the determination of the parent cosmic ray spectrum are also discussed.Comment: 20 pages, 6 figures, version accepted for publication in Phys.ReV.

On astrophysical solution to ultra high energy cosmic rays

We argue that an astrophysical solution to UHECR problem is viable. The pectral features of extragalactic protons interacting with CMB are calculated in model-independent way. Using the power-law generation spectrum $\propto E^{-\gamma_g}$ as the only assumption, we analyze four features of the proton spectrum: the GZK cutoff, dip, bump and the second dip. We found the dip, induced by electron-positron production on CMB, as the most robust feature, existing in energy range $1\times 10^{18} - 4\times 10^{19}$ eV. Its shape is stable relative to various phenomena included in calculations. The dip is well confirmed by observations of AGASA, HiRes, Fly's Eye and Yakutsk detectors. The best fit is reached at $\gamma_g =2.7$, with the allowed range 2.55 - 2.75. The dip is used for energy calibration of the detectors. After the energy calibration the fluxes and spectra of all three detectors agree perfectly, with discrepancy between AGASA and HiRes at $E> 1\times 10^{20}$ eV being not statistically significant. The agreement of the dip with observations should be considered as confirmation of UHE proton interaction with CMB. The dip has two flattenings. The high energy flattening at $E \approx 1\times 10^{19}$ eV automatically explains ankle. The low-energy flattening at $E \approx 1\times 10^{18}$ eV provides the transition to galactic cosmic rays. This transition is studied quantitatively. The UHECR sources, AGN and GRBs, are studied in a model-dependent way, and acceleration is discussed. Based on the agreement of the dip with existing data, we make the robust prediction for the spectrum at $1\times 10^{18} - 1\times 10^{20}$ eV to be measured in the nearest future by Auger detector.Comment: Revised version as published in Phys.Rev. D47 (2006) 043005 with a small additio

Critical behavior of the (2+1)-dimensional Thirring model

We investigate chiral symmetry breaking in the (2+1)-dimensional Thirring model as a function of the coupling as well as the Dirac flavor number Nf with the aid of the functional renormalization group. For small enough flavor number Nf < Nfc, the model exhibits a chiral quantum phase transition for sufficiently large coupling. We compute the critical exponents of this second order transition as well as the fermionic and bosonic mass spectrum inside the broken phase within a next-to-leading order derivative expansion. We also determine the quantum critical behavior of the many-flavor transition which arises due to a competition between vector and chiral-scalar channel and which is of second order as well. Due to the problem of competing channels, our results rely crucially on the RG technique of dynamical bosonization. For the critical flavor number, we find Nfc ~ 5.1 with an estimated systematic error of approximately one flavor.Comment: 28 pages, 14 figure