162,949 research outputs found
Brane gravity, massless bulk scalar and self-tuning of the cosmological constant
We show that a self-tuning mechanism of the cosmological constant could work
in 5D non-compact space-time with a symmetry in the presence of a
massless scalar field. The standard model matter fields live only on the 4D
brane. The change of vacuum energy on the brane (brane cosmological constant)
by, for instance, electroweak and QCD phase transitions, just gives rise to
dynamical shifts of the profiles of the background metric and the scalar field
in the extra dimension, keeping 4D space-time flat without any fine-tuning. To
avoid naked singularities in the bulk, the brane cosmological constant should
be negative. We introduce an additional brane-localized 4D Einstein-Hilbert
term so as to provide the observed 4D gravity with the non-compact extra
dimension. With a general form of brane-localized gravity term allowed by the
symmetries, the low energy Einstein gravity is successfully reproduced on the
brane at long distances. We show this phenomenon explicitly for the case of
vanishing bulk cosmological constant.Comment: 1+15 pages, no figure, Version to appear in PR
WHOLE FARM RISK-RATING MICROCOMPUTER MODEL
The Risk-Rating Model is designed to give extension specialists, teachers, and producers a method to analyze production, marketing, and financial risks. These risks may be analyzed either individually or simultaneously. The risk associated with each enterprise, for all combinations of enterprises, and for any combination of marketing strategies is estimated. Optimistic, expected, and pessimistic returns above variable cost and/or total cost are presented in the results. The probability that total return will be equal to or greater than variable cost and/or total cost is also estimated.Farm Management, Risk and Uncertainty,
High-performance Schottky diodes endure high temperatures
Fabrication process and aluminum/GaAs (gallium arsenide) coupling are used to produce Schottky diodes that have high cutoff frequencies and can withstand operating temperatures in excess of 500 C
Betweenness centrality correlation in social networks
Scale-free (SF) networks exhibiting a power-law degree distribution can be
grouped into the assortative, dissortative and neutral networks according to
the behavior of the degree-degree correlation coefficient. Here we investigate
the betweenness centrality (BC) correlation for each type of SF networks. While
the BC-BC correlation coefficients behave similarly to the degree-degree
correlation coefficients for the dissortative and neutral networks, the BC
correlation is nontrivial for the assortative ones found mainly in social
networks. The mean BC of neighbors of a vertex with BC is almost
independent of , implying that each person is surrounded by almost the
same influential environments of people no matter how influential the person
is.Comment: 4 pages, 4 figures, 1 tabl
Study of a water-vapor electrolysis unit
Sulfuric acid type water vapor electrolysis module for oxygen generation in advanced life support system
Universality Class of One-Dimensional Directed Sandpile Models
A general n-state directed `sandpile' model is introduced. The stationary
properties of the n-state model are derived for n < infty, and analytical
arguments based on a central limit theorem show that the model belongs to the
universality class of the totally asymmetric Oslo model, with a crossover to
uncorrelated branching process behavior for small system sizes. Hence, the
central limit theorem allows us to identify the existence of a large
universality class of one-dimensional directed sandpile models.Comment: 4 pages, 2 figure
Gauges in the Bulk II: Models with Bulk Scalars
Extending previous work in Randall-Sundrum type models, we construct
low-energy effective actions for braneworlds with a bulk scalar field, with
special attention to the case of BPS branes. Holding the branes at fixed
coordinate position with a general ansatz for the bulk metric, and imposing the
Einstein frame as a gauge condition, we obtain a scalar-tensor theory with only
one scalar degree of freedom related to the proper brane separation. The
formalism is applicable even when there is direct coupling of the bulk scalar
and brane matter, as in the Horava-Witten model. We further show that the usual
moduli space approximation actually describes a non-BPS three-brane system.Comment: LaTeX file of 18 page
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