23,513 research outputs found
Late Time Behaviors of an Inhomogeneous Rolling Tachyon
We study an inhomogeneous decay of an unstable D-brane in the context of
Dirac-Born-Infeld~(DBI)-type effective action. We consider tachyon and
electromagnetic fields with dependence of time and one spatial coordinate, and
an exact solution is found under an exponentially decreasing tachyon potential,
, which is valid for the description of the late time
behavior of an unstable D-brane. Though the obtained solution contains both
time and spatial dependence, the corresponding momentum density vanishes over
the entire spacetime region. The solution is governed by two parameters. One
adjusts the distribution of energy density in the inhomogeneous direction, and
the other interpolates between the homogeneous rolling tachyon and static
configuration. As time evolves, the energy of the unstable D-brane is converted
into the electric flux and tachyon matter.Comment: 17 pages, 1 figure, version to appear in PR
Stability and asymptotic behavior of periodic traveling wave solutions of viscous conservation laws in several dimensions
Under natural spectral stability assumptions motivated by previous
investigations of the associated spectral stability problem, we determine sharp
estimates on the linearized solution operator about a multidimensional
planar periodic wave of a system of conservation laws with viscosity, yielding
linearized stability for all and dimensions and nonlinear stability and
-asymptotic behavior for and . The behavior can in
general be rather complicated, involving both convective (i.e., wave-like) and
diffusive effects
On-chip differential interference contrast microscopy using lensless digital holography.
We introduce the use of a birefringent crystal with lensless digital holography to create an on-chip differential interference contrast (DIC) microscope. Using an incoherent source with a large aperture, in-line holograms of micro-objects are created, which interact with a uniaxial crystal and an absorbing polarizer, encoding differential interference contrast information of the objects on the chip. Despite the fact that a unit fringe magnification and an incoherent source with a large aperture have been used, holographic digital processing of such holograms rapidly recovers the differential phase contrast image of the specimen over a large field-of-view of approximately 24 mm(2)
Higgs bosons of a supersymmetric model at the Large Hadron Collider
It is found that CP symmetry may be explicitly broken in the Higgs sector of
a supersymmetric model with two extra neutral gauge bosons at the
one-loop level. The phenomenology of the model, the Higgs sector in particular,
is studied for a reasonable parameter space of the model, in the presence of
explicit CP violation at the one-loop level. At least one of the neutral Higgs
bosons of the model might be produced via the fusion process at the Large
Hadron Collider.Comment: 23 pages, 5 figures, JHE
BPS D-branes from an Unstable D-brane
We search for exact tachyon kink solutions of DBI type effective action
describing an unstable D-brane with worldvolume gauge field turned in both the
flat and a curved background. There are various kinds of solutions in the
presence of electromagnetic fields in the flat space, such as periodic arrays,
topological tachyon kinks, half kinks, and bounces. We identify a BPS object,
D(-1)F1 bound state, which describes a thick brane with string flux density.
The curved background of interest is the ten-dimensional lift of the
Salam-Sezgin vacuum and, in the asymptotic limit, it approaches . The solutions in the curved
background are identified as composites of lower-dimensional D-branes and
fundamental strings, and, in the BPS limit, they become a D4D2F1 composite
wrapped on where is inside .Comment: 4 pages, to appear in the proceeding of PASCOS 2005, Gyeongju, Korea,
May 30-June 4, 200
Humidity contribution to C_n^2 over a 600m pathlength in a tropical marine environment
We present new optical turbulence structure parameter measurements, C_n^2,
over sea water between La Parguera and Magueyes Island (17.6N 67W) on the
southwest coast of Puerto Rico. The 600 meter horizontal paths were located
approximately 1.5 m and 10 m above sea level. No data of this type has ever
been made available in the literature. Based on the data, we show that the
C_n^2 measurements are about 7 times less compared to equivalent land data.
This strong evidence reinforces our previous argument that humidity must be
accounted for to better ascertain the near surface atmospheric turbulence
effects, which current visible / near infrared C_n^2 bulk models fail to do. We
also explore the generalised fractal dimension of this littoral data and
compare it to our reference land data. We find cases that exhibit monofractal
characteristics, that is to say, the effect of rising temperatures during the
daylight hours upon turbulence are counterbalanced by humidity, leading to a
single characteristic scale for the measurements. In other words, significant
moisture changes in the measurement volume cancels optical turbulence increases
due to temperature rises. Figures available as JPG only.Comment: 7 pages, 4 figures, 1 table, SPIE Photonics West 2007, paper 6457B-2
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