39,094 research outputs found
High-frequency sound propagation in a spatially varying mean flow
An equation for acoustic ray paths in a spatially varying mean flow was examined to determine some of the characteristics of the flow gradient effects on sound propagation. In a potential flow, the acoustic rays are deflected in the direction of increasing mean flow, and the gradient of the mean flow speed is the dominant factor causing the ray deflection. In contrast, in a sheared mean flow, the vorticity is the dominant factor in deflection of the acoustic rays
Light bottom squark and gluino confront electroweak precision measurements
We address the compatibility of a light sbottom (mass 2\sim 5.5 \gev) and a
light gluino (mass 12\sim 16 \gev) with electroweak precision measurements.
Such light particles have been suggested to explain the observed excess in the
quark production cross section at the Tevatron. The electroweak observables
may be affected by the sbottom and gluino through the SUSY-QCD corrections to
the vertex. We examine, in addition to the SUSY-QCD corrections, the
electroweak corrections to the gauge boson propagators from the stop which are
allowed to be light from the SU(2) symmetry. We find that this scenario is
strongly disfavored from electroweak precision measurements unless the heavier
sbottom mass eigenstate is lighter than 180\gev and the left-right mixing in
the stop sector is sufficiently large. This implies that one of the stops
should be lighter than about 98\gev.Comment: 4 pages, revtex, 2 figures. Reference added, version to appear in
Phys.Rev.Let
Lineal Trails of D2-D2bar Superstrings
We study the superstrings suspended between a D2- and an anti-D2-brane. We
quantize the string in the presence of some general configuration of gauge
fields over the (anti-)D-brane world volumes. The interstring can move only in
a specific direction that is normal to the difference of the electric fields of
each (anti-)D-branes. Especially when the electric fields are the same, the
interstring cannot move. We obtain the condition for the tachyons to disappear
from the spectrum.Comment: 15 pages with 4 figures, referenced added, Sec. 5 on the spectrum
made cleare
Super Jackstraws and Super Waterwheels
We construct various new BPS states of D-branes preserving 8 supersymmetries.
These include super Jackstraws (a bunch of scattered D- or (p,q)-strings
preserving supersymmetries), and super waterwheels (a number of D2-branes
intersecting at generic angles on parallel lines while preserving
supersymmetries). Super D-Jackstraws are scattered in various dimensions but
are dynamical with all their intersections following a common null direction.
Meanwhile, super (p,q)-Jackstraws form a planar static configuration. We show
that the SO(2) subgroup of SL(2,R), the group of classical S-duality
transformations in IIB theory, can be used to generate this latter
configuration of variously charged (p,q)-strings intersecting at various
angles. The waterwheel configuration of D2-branes preserves 8 supersymmetries
as long as the `critical' Born-Infeld electric fields are along the common
direction.Comment: 23 pages, 10 figure
Quarkonium Wave Functions at the Origin
We tabulate values of the radial Schr\"{o}dinger wave function or its first
nonvanishing derivative at zero quark-antiquark separation, for ,
, and levels that lie below, or just above, flavor
threshold. These quantities are essential inputs for evaluating production
cross sections for quarkonium states.Comment: 9 pages, RevTeX, no figure
Geometrization of the Gauge Connection within a Kaluza-Klein Theory
Within the framework of a Kaluza-Klein theory, we provide the geometrization
of a generic (Abelian and non-Abelian) gauge coupling, which comes out by
choosing a suitable matter fields dependence on the extra-coordinates.
We start by the extension of the Nother theorem to a multidimensional
spacetime being the direct sum of a 4-dimensional Minkowski space and of a
compact homogeneous manifold (whose isometries reflect the gauge symmetry); we
show, how on such a ``vacuum'' configuration, the extra-dimensional components
of the field momentum correspond to the gauge charges. Then we analyze the
structure of a Dirac algebra as referred to a spacetime with the Kaluza-Klein
restrictions and, by splitting the corresponding free-field Lagrangian, we show
how the gauge coupling terms outcome.Comment: 10 pages, no figure, to appear on Int. Journ. Theor. Phy
String Pair Creations in D-brane Systems
We investigate the criterion, on the Born-Infeld background fields, for the
open string pair creation to occur in D-(anti-)D-brane systems. Although
the pair creation occurs generically in both D-D and D-anti-D
systems for the cases which meet the criterion, it is more drastic in
D-anti-D-brane systems by some exponential factor depending on the
background fields. Various configurations exhibiting pair creations are
obtained via duality transformations. These include the spacelike scissors and
two D-strings (slanted at different angles) passing through each other. We
raise the scissors paradox and suggest a resolution based on the triple
junction in IIB setup.Comment: V2. 1+28 pages, 5 figures in JHEP3, minor changes, added reference
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