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Tkachev, Igor

Last name
Tkachev
First name
Igor
Country
-
  • Phenomenology of Axion Miniclusters

    I review possible observational phenomena appearing in models leading to dense small-scale substructures in the axionic dark matter. Also, I discuss their imaginable implications for the direct dark matter searches in the laboratory.

    What if Dark matter is Bosonic and self-interacting

    Recently the problem of singular galactic cores and over-abundant formation of dwarf galaxies, inherent to the standard cold dark matter model, had attracted a great deal of attention. One scenario which may be free of these problems invokes a self-interacting Bose-field. We find the limiting core density in this model due to the self-annihilation of the scalar field into its own relativistic quanta. The limiting density may correspond to the observable one if there is only one dark matter co...

    The nuMSM, inflation, and dark matter

    We show how to enlarge the νMSM (the minimal extension of the Standard Model by three right-handed neutrinos) to incorporate inflation and provide a common source for electroweak symmetry breaking and for right-handed neutrino masses. In addition to inflation, the resulting theory can explain simultaneously dark matter and the baryon asymmetry of the Universe; it is consistent with experiments on neutrino oscillations and with all astrophysical and cosmological constraints on sterile neutrino...

    The $\nu$ MSM, Inflation, and Dark Matter

    We show how to enlarge the $\nu$MSM (the minimal extension of the standard model by three right-handed neutrinos) to incorporate inflation and provide a common source for electroweak symmetry breaking and for right-handed neutrino masses. In addition to inflation, the resulting theory can explain simultaneously dark matter and the baryon asymmetry of the Universe; it is consistent with experiments on neutrino oscillations and with all astrophysical and cosmological constraints on sterile neut...

    LATTICEEASY: A Program for Lattice Simulations of Scalar Fields in an Expanding Universe

    We describe a C++ program that we have written and made available for calculating the evolution of interacting scalar fields in an expanding universe. The program is particularly useful for the study of reheating and thermalization after inflation. The program and its full documentation are available on the Web at http://physics.stanford.edu/gfelder/latticeeasy/ . In this paper we provide a brief overview of what the program does and what it is useful for.

    Signatures of a Graviton Mass in the Cosmic Microwave Background

    There exist consistent low energy effective field theories describing gravity in the Higgs phase that allow the coexistence of massive gravitons and the conventional 1/r potential of gravity. In an effort to constrain the value of the graviton mass in these theories, we study the tensor contribution to the CMB temperature anisotropy and polarization spectra in the presence of a non-vanishing graviton mass. We find that the observation of a B-mode signal consistent with the spectrum predicted ...

    Neutrinos in IceCube from AGN's

    Recently IceCube collaboration has reported first evidence for the astrophysical neutrinos. Observation corresponds to the total astrophysical neutrino flux of the order of $3 \cdot 10^{-8}$ $GeV/cm^2/s/sr$ in a PeV energy range. Active Galactic Nuclei (AGN) are natural candidate sources for such neutrinos. To model the neutrino creation in AGNs we study photopion production processes on the radiation field of the Shakura-Sunyaev accretion disks in the black hole vicinity. We show that this m...

    Comment on "Correlation of the Highest-Energy Cosmic Rays with Nearby Extragalactic Objects"

    We argue that the data published by the Pierre Auger Collaboration (arXiv:0711.2256) disfavor at 99% confidence level their hypothesis that most of the highest-energy cosmic rays are protons from nearby astrophysical sources, either Active Galactic Nuclei or other objects with a similar spatial distribution.

    Constrained Simulations of the Magnetic Field in the Local Universe and the Propagation of UHECRs

    We use simulations of LSS formation to study the build-up of magnetic fields (MFs) in the ICM. Our basic assumption is that cosmological MFs grow in a MHD amplification process driven by structure formation out of a seed MF present at high z. Our LCDM initial conditions for the density fluctuations have been statistically constrained by the observed galaxies, based on the IRAS 1.2-Jy all-sky redshift survey. As a result, prominent galaxy clusters in our simulation coincide closely with their ...

    Tidal streams from axion miniclusters and direct axion searches

    In some axion dark matter models a dominant fraction of axions resides in dense small-scale substructures, axion miniclusters. A fraction of these substructures is disrupted and forms tidal streams where the axion density may still be an order of magnitude larger than the average. We discuss implications of these streams for the direct axion searches. We estimate the fraction of disrupted miniclusters and the parameters of the resulting streams, and find that stream-crossing events would occu...
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