394 research outputs found
MHD power-law fluid flow and heat transfer over a non-isothermal stretching sheet
This article presents a numerical solution for the magnetohydrodynamic (MHD) non-Newtonian power-law fluid flow over a semi-infinite non-isothermal stretching sheet with internal heat generation/absorption. The flow is caused by linear stretching of a sheet from an impermeable wall. Thermal conductivity is assumed to vary linearly with temperature. The governing partial differential equations of momentum and energy are converted into ordinary differential equations by using a classical similarity transformation along with appropriate boundary conditions. The intricate coupled non-linear boundary value problem has been solved by Keller box method. It is important to note that the momentum and thermal boundary layer thickness decrease with increase in the power-law index in presence/absence of variable thermal conductivity
Dynamically Induced Spontaneous Symmetry Breaking in 3-3-1 Models
We show that in SU(3)_C X SU(3)_L X U(1)_N (3-3-1) models embedded with a
singlet scalar playing the role of the axion, after imposing scale invariance,
dynamical symmetry breaking of Peccei-Quinn symmetry occurs through the
one-loop effective potential for the singlet field. We, then, analyze the
structure of spontaneous symmetry breaking by studying the new scalar potential
for the model, and verify that electroweak symmetry breaking is tightly
connected to the 3-3-1 breaking by the strong constraints among their vacuum
expectation values. This offers a valuable guide to write down the correct
pattern of symmetry breaking for multi-scalar theories. We also obtained that
the accompanying massive pseudo-scalar, instead of acquiring mass of order of
Peccei-Quinn scale as we would expect, develops a mass at a much lower scale, a
consequence solely of the dynamical breaking.Comment: 12 pages, typos corrected, improved text, conclusions unchange
Gravitational couplings of charged leptons in a medium
We calculate the leading order matter-induced corrections to the
gravitational interactions of charged leptons and their antiparticles in a
medium that contains electrons but not the other charged leptons, such as
normal matter. The gravitational coupling, which is universal at the tree
level, is found to be flavor-dependent, and also different for the
corresponding antiparticles, when the corrections of are taken into
account. General expressions are obtained for the matter-induced corrections to
the gravitational mass in a generic matter background, and explicit formulas
for those corrections are given in terms of the macroscopic parameters of the
medium for particular conditions of the background gases.Comment: Latex, axodraw, 39 pages. Added a few stylistic corrections and
clarifying statements in the treatment of the photon tadpole diagra
Naturally light right-handed neutrinos in a 3-3-1 Model
In this work we show that light right-handed neutrinos, with mass in the
sub-eV scale, is a natural outcome in a 3-3-1 model. By considering effective
dimension five operators, the model predicts three light right-handed
neutrinos, weakly mixed with the left-handed ones. We show also that the model
is able to explain the LSND experiment and still be in agreement with solar and
atmospheric data for neutrino oscillation.Comment: About 5 pages, no-figure
A solution of the coincidence problem based on the recent galactic core black hole mass density increase
A mechanism capable to provide a natural solution to two major cosmological
problems, i.e. the cosmic acceleration and the coincidence problem, is
proposed. A specific brane-bulk energy exchange mechanism produces a total dark
pressure, arising when adding all normal to the brane negative pressures in the
interior of galactic core black holes. This astrophysically produced negative
dark pressure explains cosmic acceleration and why the dark energy today is of
the same order to the matter density for a wide range of the involved
parameters. An exciting result of the analysis is that the recent rise of the
galactic core black hole mass density causes the recent passage from cosmic
deceleration to acceleration. Finally, it is worth mentioning that this work
corrects a wide spread fallacy among brane cosmologists, i.e. that escaping
gravitons result to positive dark pressure.Comment: 14 pages, 3 figure
Turbulent Compressible Convection with Rotation - Penetration above a Convection Zone
We perform Large eddy simulations of turbulent compressible convection in
stellar-type convection zones by solving the Navi\'{e}r-Stokes equations in
three dimensions. We estimate the extent of penetration into the stable layer
above a stellar-type convection zone by varying the rotation rate
({\boldmath}), the inclination of the rotation vector () and
the relative stability () of the upper stable layer. The computational
domain is a rectangular box in an f-plane configuration and is divided into two
regions of unstable and stable stratification with the stable layer placed
above the convectively unstable layer. Several models have been computed and
the penetration distance into the stable layer above the convection zone is
estimated by determining the position where time averaged kinetic energy flux
has the first zero in the upper stable layer. The vertical grid spacing in all
the model is non-uniform, and is less in the upper region so that the flows are
better resolved in the region of interest. We find that the penetration
distance increases as the rotation rate increases for the case when the
rotation vector is aligned with the vertical axis. However, with the increase
in the stability of the upper stable layer, the upward penetration distance
decreases. Since we are not able to afford computations with finer resolution
for all the models, we compute a number of models to see the effect of
increased resolution on the upward penetration. In addition, we estimate the
upper limit on the upward convective penetration from stellar convective cores.Comment: Accepted for Publication in Asttrophysics & Space Scienc
Development of soil and terrain digital database for major food-growing regions of India for resource planning
Soil information system in SOTER (soil and terrain digital database) framework is developed for the Indo-Gangetic Plains (IGP) and black soil regions (BSR) of India with the help of information from 842 georeferenced soil profiles including morphological, physical and chemical properties of soils in addition to the site characteristics and climatic information. The database has information from 82 climatic stations that can be linked with the other datasets. The information from this organized database can be easily retrieved for use and is compatible with the global database. The database can be updated with recent and relevant data as and when they are available. The database has many applications such as inputs for refinement of agro-ecological regions and sub-regions, studies on carbon sequestration, land evaluation and land (crop) planning, soil erosion, soil quality, carbon and crop modelling and other climate change related research. This warehouse of information in a structured framework can be used as a data bank for posterity
Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV
We present the first measurement of directed flow () at RHIC. is
found to be consistent with zero at pseudorapidities from -1.2 to 1.2,
then rises to the level of a couple of percent over the range . The latter observation is similar to data from NA49 if the SPS rapidities
are shifted by the difference in beam rapidity between RHIC and SPS.
Back-to-back jets emitted out-of-plane are found to be suppressed more if
compared to those emitted in-plane, which is consistent with {\it jet
quenching}. Using the scalar product method, we systematically compared
azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow
from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure
Azimuthal anisotropy: the higher harmonics
We report the first observations of the fourth harmonic (v_4) in the
azimuthal distribution of particles at RHIC. The measurement was done taking
advantage of the large elliptic flow generated at RHIC. The integrated v_4 is
about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8)
harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
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