143,465 research outputs found

### Power Spectrum of Cosmic Momentum Field Measured from the SFI Galaxy Sample

We have measured the cosmic momentum power spectrum from the peculiar
velocities of galaxies in the SFI sample. The SFI catalog contains field spiral
galaxies with radial peculiar velocities derived from the I-band Tully-Fisher
relation. As a natural measure of the large-scale peculiar velocity field, we
use the cosmic momentum field that is defined as the peculiar velocity field
weighted by local number of galaxies. We have shown that the momentum power
spectrum can be derived from the density power spectrum for the constant linear
biasing of galaxy formation, which makes it possible to estimate \beta_S =
\Omega_m^{0.6} / b_S parameter precisely where \Omega_m is the matter density
parameter and b_S is the bias factor for optical spiral galaxies. At each
wavenumber k we estimate \beta_S(k) as the ratio of the measured to the derived
momentum power over a wide range of scales (0.026 h^{-1}Mpc <~ k <~ 0.157
h^{-1}Mpc) that spans the linear to the quasi-linear regimes. The estimated
\beta_S(k)'s have stable values around 0.5, which demonstrates the constancy of
\beta_S parameter at scales down to 40 h^{-1}Mpc. We have obtained
\beta_S=0.49_{-0.05}^{+0.08} or \Omega_m = 0.30_{-0.05}^{+0.09} b_S^{5/3}, and
the amplitude of mass fluctuation as
\sigma_8\Omega_m^{0.6}=0.56_{-0.21}^{+0.27}. The 68% confidence limits include
the cosmic variance. We have also estimated the mass density power spectrum.
For example, at k=0.1047 h Mpc^{-1} (\lambda=60 h^{-1}Mpc) we measure
\Omega_m^{1.2} P_{\delta}(k)=(2.51_{-0.94}^{+0.91})\times 10^3 (h^{-1}Mpc)^3,
which is lower compared to the high-amplitude power spectra found from the
previous maximum likelihood analyses of peculiar velocity samples like Mark
III, SFI, and ENEAR.Comment: 12 pages, 9 figures, accepted for publication in Ap

### Isospin-violating dark matter from a double portal

We study a simple model that can give rise to isospin-violating interactions
of Dirac fermion asymmetric dark matter to protons and neutrons through the
interference of a scalar and U(1)$'$ gauge boson contribution. The model can
yield a large suppression of the elastic scattering cross section off Xenon
relative to Silicon thus reconciling CDMS-Si and LUX results while being
compatible with LHC findings on the 126 GeV Higgs, electroweak precision tests
and flavour constraints.Comment: 25 pages, 7 figure

### The strongest experimental constraints on SU(5)xU(1) supergravity models

We consider a class of well motivated string-inspired flipped $SU(5)$
supergravity models which include four supersymmetry breaking scenarios:
no-scale, strict no-scale, dilaton, and special dilaton, such that only three
parameters are needed to describe all new phenomena $(m_t,\tan\beta,m_{\tilde
g})$. We show that the LEP precise measurements of the electroweak parameters
in the form of the $\epsilon_1$ variable, and the CLEOII allowed range for
\bsg are at present the most important experimental constraints on this class
of models. For m_t\gsim155\,(165)\GeV, the $\epsilon_1$ constraint (at
90(95)\%CL) requires the presence of light charginos
(m_{\chi^\pm_1}\lsim50-100\GeV depending on $m_t$). Since all sparticle
masses are proportional to $m_{\tilde g}$, m_{\chi^\pm_1}\lsim100\GeV
implies: m_{\chi^0_1}\lsim55\GeV, m_{\chi^0_2}\lsim100\GeV, m_{\tilde
g}\lsim360\GeV, m_{\tilde q}\lsim350\,(365)\GeV, m_{\tilde
e_R}\lsim80\,(125)\GeV, m_{\tilde e_L}\lsim120\,(155)\GeV, and
m_{\tilde\nu}\lsim100\,(140)\GeV in the no-scale (dilaton) flipped $SU(5)$
supergravity model. The \bsg constraint excludes a significant fraction of
the otherwise allowed region in the $(m_{\chi^\pm_1},\tan\beta)$ plane
(irrespective of the magnitude of the chargino mass), while future experimental
improvements will result in decisive tests of these models. In light of the
$\epsilon_1$ constraint, we conclude that the outlook for chargino and
selectron detection at LEPII and at HERA is quite favorable in this class of
models.Comment: CTP-TAMU-40/93, Latex, 13 pages, 10 figures (available as uuencoded
0.963MB file from [email protected]

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