1,260 research outputs found
Amelioration of Little Hierarchy Problem in SU(4)_c x SU(2)_L x SU(2)_R
The little hierarchy problem encountered in the constrained minimal
supersymmetric model (CMSSM) can be ameliorated in supersymmetric models based
on the gauge symmetry G_{422} \equiv SU(4)_c x SU(2)_L x SU(2)_R. The standard
assumption in CMSSM (and in SU(5) and SO(10)) of universal gaugino masses can
be relaxed in G_{422}, and this leads to a significant improvement in the
degree of fine tuning required to implement radiative electroweak breaking in
the presence of a characteristic supersymmetry breaking scale of around a TeV.
Examples of Higgs and sparticle mass spectra realized with 10% fine tuning are
presented.Comment: 14 pages, 5 figures, 2 table
On the Impact of Antenna Topologies for Massive MIMO Systems
Approximate expressions for the spatial correlation of cylindrical and
uniform rectangular arrays (URA) are derived using measured distributions of
angles of departure (AOD) for both the azimuth and zenith domains. We examine
massive multiple-input-multiple-output (MIMO) convergence properties of the
correlated channels by considering a number of convergence metrics. The
per-user matched filter (MF) signal-to-interference-plus-noise ratio (SINR)
performance and convergence rate, to respective limiting values, of the two
antenna topologies is also explored.Comment: 6 pages, 6 figure
On the Convergence of Massive MIMO Systems
In this paper we examine convergence properties of massive MIMO systems with
the aim of determining the number of antennas required for massive MIMO gains.
We consider three characteristics of a channel matrix and study their
asymptotic behaviour. Furthermore, we derive ZF SNR and MF SINR for a scenario
of unequal receive powers. In our results we include the effects of spatial
correlation. We show that the rate of convergence of channel metrics is much
slower than that of the ZF/MF precoder properties.Comment: 6 pages, 6 figures, ICC 201
Pursuing Parameters for Critical Density Dark Matter Models
We present an extensive comparison of models of structure formation with
observations, based on linear and quasi-linear theory. We assume a critical
matter density, and study both cold dark matter models and cold plus hot dark
matter models. We explore a wide range of parameters, by varying the fraction
of hot dark matter , the Hubble parameter and the spectral
index of density perturbations , and allowing for the possibility of
gravitational waves from inflation influencing large-angle microwave background
anisotropies. New calculations are made of the transfer functions describing
the linear power spectrum, with special emphasis on improving the accuracy on
short scales where there are strong constraints. For assessing early object
formation, the transfer functions are explicitly evaluated at the appropriate
redshift. The observations considered are the four-year {\it COBE} observations
of microwave background anisotropies, peculiar velocity flows, the galaxy
correlation function, and the abundances of galaxy clusters, quasars and damped
Lyman alpha systems. Each observation is interpreted in terms of the power
spectrum filtered by a top-hat window function. We find that there remains a
viable region of parameter space for critical-density models when all the dark
matter is cold, though must be less than 0.5 before any fit is found and
significantly below unity is preferred. Once a hot dark matter component is
invoked, a wide parameter space is acceptable, including . The
allowed region is characterized by \Omega_\nu \la 0.35 and 0.60 \la n \la
1.25, at 95 per cent confidence on at least one piece of data. There is no
useful lower bound on , and for curious combinations of the other parameters
it is possible to fit the data with as high as 0.65.Comment: 19 pages LaTeX file (uses mn.sty). Figures *not* included due to
length. We strongly recommend obtaining the full paper, either by WWW at
http://star-www.maps.susx.ac.uk/papers/lsstru_papers.html (UK) or
http://www.bartol.udel.edu/~bob/papers (US), or by e-mailing ARL. Final
version, to appear MNRAS. Main revision is update to four-year COBE data.
Miscellaneous other changes and reference updates. No significant changes to
principal conclusion
Non-Minimal Chaotic Inflation, Peccei-Quinn Phase Transition and non-Thermal Leptogenesis
We consider a phenomenological extension of the minimal supersymmetric
standard model (MSSM) which incorporates non-minimal chaotic inflation, driven
by a quadratic potential in conjunction with a linear term in the frame
function. Inflation is followed by a Peccei-Quinn phase transition, based on
renormalizable superpotential terms, which resolves the strong CP and mu
problems of MSSM and provide masses lower than about 10^12 GeV for the
right-handed (RH) (s)neutrinos. Baryogenesis occurs via non-thermal
leptogenesis, realized by the out-of-equilibrium decay of the RH sneutrinos
which are produced by the inflaton's decay. Confronting our scenario with the
current observational data on the inflationary observables, the light neutrino
masses, the baryon asymmetry of the universe and the gravitino limit on the
reheat temperature, we constrain the strength of the gravitational coupling to
rather large values (~45-2950) and the Dirac neutrino masses to values between
about 1 and 10 GeV.Comment: Final versio
Fermion Masses and Mixings in GUTs with Non-Canonical U(1)_Y
We discuss fermion masses and mixings in models derived from orbifold GUTs
such that gauge coupling unification is achieved without low energy
supersymmetry by utilizing a non-canonical U(1)_Y. A gauged U(1)_X flavor
symmetry plays an essential role, and the Green-Schwarz mechanism is invoked in
anomaly cancellations. Models containing vector-like particles with masses
close to M_{GUT} are also discussed.Comment: 18 page
The Hot and Cold Outflows of NGC 3079
Very deep neutral hydrogen (HI) observations of the edge-on spiral galaxy NGC
3079 with the Westerbork Synthesis Radio Telescope (WSRT) are presented. The
galaxy has been studied extensively in different wavelengths and known for its
several unique and complex features. However, the new data still revealed
several new features and show that the galaxy is even more complicated and
interesting than previously thought. In the new data a large stream of gas,
encircling the entire galaxy, was discovered, while the data also show, for the
first time, that not only hot gas is blown into space by the starburst/AGN, but
also large amounts of cold gas, despite the high energies involved in the
outflow.Comment: To appear in the Proceedings of the "Galaxy Wars: Stellar Populations
and Star Formation in Interacting Galaxies" Conference, B. Smith, N. Bastian,
J. Higdon and S. Higdon eds, in pres
Gravitational GUT Breaking and the GUT-Planck Hierarchy
It is shown that non-renormalizable gravitational interactions in the Higgs
sector of supersymmetric grand unified theories (GUT's) can produce the
breaking of the unifying gauge group at the GUT scale ~GeV. Such a breaking offers an attractive alternative to the
traditional method where the superheavy GUT scale mass parameters are added ad
hoc into the theory. The mechanism also offers a natural explanation for the
closeness of the GUT breaking scale to the Planck scale. A study of the minimal
SU(5) model endowed with this mechanism is presented and shown to be
phenomenologically viable. A second model is examined where the Higgs doublets
are kept naturally light as Goldstone modes. This latter model also achieves
breaking of at but cannot easily satisfy the current
experimental proton decay bound.Comment: 11 pages, REVTeX, 1 figure included as an uuencoded Z-compressed
PostScript file. Our Web page at
http://physics.tamu.edu/~urano/research/gutplanck.html contains ready to
print PostScript version (with figures) as well as color version of plot
Effect of different solvent extracted sample of Allium sativum (Linn) on bacteria and fungi
This study was aimed to evaluate the antimicrobial activity of garlic-extracted samples against bacteria and fungi at different concentration, in various polar solvents. For this purpose, six different extracts were prepared, using five different polar solvents (methanol, ethyl acetate, petroleum ether, chloroforms and butanol) and water. Two different concentrations (1 and 2 mg disc-1) of each extract were subjected for preliminary antibacterial screening against seven pathogenic bacteria by Kirby- Bauer disk diffusion method. The result of in vitro antibacterial screening showed that 6 extracts from garlic had different ranges of antibacterial activities. When garlic extracts were studied for their antibacterial potential against Gram-positive bacteria and Gram-negative bacteria, the butanol extracted samples showed the highest inhibitory effect against B. cereus (76% ZI at 2 mg disc-1 concentration). Water extracted samples indicated a good range of inhibitory effect against Salmonella typhi (73% ZI at 2 mg disc-1) and butanol extracted sample showed highest activity against Erwinia carotovora (75% ZI). The data also showed that of petroleum ether, methanol and water did not show any inhibitory effect against the tested microbes.Key words: Solvent, bacteria, fungi, Allium sativum
Monopole-antimonopole bound states as a source of ultra-high-energy cosmic rays
The electromagnetic decay and final annihilation of magnetic
monopole-antimonopole pairs formed in the early universe has been proposed as a
possible mechanism to produce the highest energy cosmic rays. We show that for
a monopole abundance saturating the Parker limit, the density of magnetic
monopolonium formed is many orders of magnitude less than that required to
explain the observed cosmic ray flux. We then propose a different scenario in
which the monopoles and antimonopoles are connected by strings formed at a low
energy phase transition (~ 100 GeV). The bound states decay by gravitational
radiation, with lifetimes comparable with the age of the universe. This
mechanism avoids the problems of the standard monopolonium scenario, since the
binding of monopoles and antimonopoles is perfectly efficient.Comment: 10 pages, RevTeX, no figure
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