Narrow Results

We considered propagation of Ultra High Energy Cosmic Rays (UHECR) through the galaxy. We investigated models with sources of UHECR distributed in the same way as Cold Dark Matter (CDM) in a self-consistent way, taking into account both extra-galactic and Galactic contributions. Using a very simple toy model of galactic magnetic field we showed that in the case of galactic origin of UHECRs the anisotropy can reach considerable values. In the case of extragalactic UHECRs origin, the anisotropy appears to be nonvanishing only for electron and photon components due to synchrotron losses, but it can hardly be reassured. The reason is an extremely low flux of UHE electrons and a too low level of γ-ray anisotropy.

We consider models with a vectorlike confining gauge theory in the hidden sector, and demonstrate that the origin of the electroweak symmetry breaking (EWSB) is due to the dimensional transmutation in the hidden sector gauge theory, and the lightest mesons in the hidden sector could be a good cold dark matter (CDM) candidate. There would be more than one neutral Higgs-like scalar bosons, and they could decay mainly into the CDM pair, if that decay channel is kinemtically allowed.

Cold dark matter (DM) is conceived as a gas of massive particles that undergo collisions, interact gravitationally and exchange quanta of energy. A new nonrelativistic quantum theory is presented for this model of DM, based on a recently discovered equation for a spinless, no charge and free particle. This theory describes the quantum processes undergoing by the particles, specifies the required characteristic wavelength of the quanta of energy, gives constraints on the mass of DM particles, and predicts a detectable gravitational wave background associated with DM halos.

The present work deals with a detailed study of interacting holographic dark energy model for three common choices of the interaction term. Also, two standard choices of IR cut-off, namely, Ricci length scale and radius of the event horizon are considered here. Finally, the cosmographic parameters are presented both analytically and graphically.

We discuss the cosmological evolution of the interacting pilgrim dark energy (DE) with conformal age of the universe in flat FRW universe. We evaluate the equation of state (EoS) parameter for three different values of interacting parameter which evolutes the universe from matter dominated to phantom-like eras by evolving quintessence as well as vacuum DE eras. We also give the correspondence of the present DE model with quintessence, tachyon, k-essence, dilaton and DBI-essence scalar field models. We discuss the dynamics of scalar field and corresponding potentials. We find that the behavior of scalar field, corresponding potentials and kinetic energy terms (in k-essence and dilaton field) consistent with the present day observations. Also, cosmological planes such as and r - s planes corresponds to ΛCDM limit.

We show that the Ω_b - Ω_DM coincidence can naturally be explained in a framework where axino cold dark matter is predominantly produced in non-thermal processes involving decays of Q-balls formed in Affleck-Dine baryogenesis. In this approach the similarity between Ω_b and Ω_DM is a direct consequence of the (sub-)GeV scale of the mass of the axino.

The article describes the research program towards an experiment to observe coherent scattering between neutrinos and the nucleus at the power reactor. The motivations of studying this process are surveyed. In particular, a threshold of 100-200 eV has been achieved with an ultra-low-energy germanium detector prototype. This detection capability at low energy can also be adapted for searches of Cold Dark Matter in the low-mass region as well as to enhance the sensitivities in the study of neutrino magnetic moments.

The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed to measure charged cosmic rays spectra up to TV region, with high energy photon detection capability up to few hundred GeV. With the large acceptance, the long duration (3 years) and the state of the art particle identification techniques, AMS will provide the most sensitive search for the existence of antimatter nuclei and for the origin of dark matter. The detector is being constructed with an eight layers Silicon Tracker inside a large superconducting magnet, providing a ~ 0.8 Tm² bending power and an acceptance of ~ 0.5 m²sr. A Transition Radiation Detector and a 3D Electromagnetic Calorimeter allow for electron, positron and photon identification, while independent velocity measurements are performed by a Time of Flight scintillating system and a Ring Image Cherenkov detector. The overall construction is due to be completed by 2008.

The following sections are included:

• Basics
  • Friedmann–Lemaître–Robertson–Walker Universe
  • Energy forms
  • Future
  • Density perturbation
• Thermal production
  • Number density history
  • Decoupling temperature
  • Interaction and decay rates
• Cosmological nucleosynthesis
• Baryon number in the Universe
• Thermal WIMP production in the Universe
  • Heavy neutrino
  • Forces for weakly interacting massive particles
  • WIMP relic density
• Nonthermal production
  • Non-thermal WIMP production
  • E-WIMP production
  • ADM production
  • Axion production
  • Heavy lepton as WIMP
• References

I provide an introduction to experiments designed to detect WIMP dark matter directly, focussing on building intuitive understanding of the characteristics of potential WIMP signals and the experimental techniques. After deriving the characteristics of potential signals in direct-detection experiments for standard WIMP models, I summarize the general experimental methods shared by most direct-detection experiments and review the advantages, challenges, and status of such searches. Experiments are already probing SUSY models, with best limits on the spin-independent coupling below 10^-7 pb. Combined information from direct and indirect detection, along with detection at colliders, promises to teach us much about fundamental particle physics, cosmology, and astrophysics.

The free parameters of a flat accelerating model without dark energy are constrained by using Supernovae type Ia and observational H(z) data. Instead of the vacuum dominance, the present accelerating stage in this modified Einstein-de Sitter cosmology is a consequence of the gravitationally-induced particle production of cold dark matter. The model present a transition from a decelerating to an accelerating regime at low redshifts, and is also able to harmonize a cold dark matter picture with the latest measurements of the Hubble constant H₀, the Supernovae observations (Constitution sample), and the H(z) data.