4,943 research outputs found
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
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
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
Oblique DLCQ M-theory and Multiple M2-branes
We propose an oblique DLCQ as a limit to realize a theory of multiple
M2-branes in M(atrix)-theory context. The limit is a combination of an infinite
boosting of a space-like circle and a tuned tilting of the circle direction. We
obtain a series of supergravity solutions describing various dual
configurations including multiple M2-branes. For an infinite boosting along a
circle wrapped obliquely around a rectangular torus, Seiberg's DLCQ limit
distorts the torus modulus. In the context of supergravity, we show explicitly
how this torus modulus of -theory is realized as the
vacuum modulus of dual IIB-theory.Comment: v3: 25pages, extended version, References adde
The Entropy Function for the Black Holes of Nariai Class
Based on the fact that the near horizon geometry of the extremal
Schwarzschild-de Sitter black holes is Nariai geometry, we define the black
holes of Nariai class as the configuration whose near-horizon geometry is
factorized as two dimensional de Sitter space-time and some compact topology,
that is Nariai geometry. We extend the entropy function formalism to the case
of the black holes of Nariai class. The conventional entropy function (for the
extremal black holes) is defined as Legendre transformation of Lagrangian
density, thus the `Routhian density', over two dimensional anti-de Sitter. As
for the black holes of Nariai class, it is defined as {\em minus} `Routhian
density' over two dimensional de Sitter space-time. We found an exact agreement
of the result with Bekenstein-Hawking entropy. The higher order corrections are
nontrivial only when the space-time dimension is over four, that is, .
There is a subtlety as regards the temperature of the black holes of Nariai
class. We show that in order to be consistent with the near horizon geometry,
the temperature should be non-vanishing despite the extremality of the black
holes.Comment: references added, compatible with the published versio
Atomic structure, energetics, and dynamics of topological solitons in Indium chains on Si(111) surfaces
Based on scanning tunneling microscopy and first-principles theoretical
studies, we characterize the precise atomic structure of a topological soliton
in In chains grown on Si(111) surfaces. Variable-temperature measurements of
the soliton population allow us to determine the soliton formation energy to be
~60 meV, smaller than one half of the band gap of ~200 meV. Once created, these
solitons have very low mobility, even though the activation energy is only
about 20 meV; the sluggish nature is attributed to the exceptionally low
attempt frequency for soliton migration. We further demonstrate local electric
field-enhanced soliton dynamics.Comment: 5 pages, 3 figure
Large capacitance-voltage hysteresis loops in SiO[sub 2] films containing Ge nanocrystals produced by ion implantation and annealing
Metal-oxide-semiconductorstructures containing Genanocrystals (NCs) of 3–4nm diameter and 2×10¹²cm⁻² density are shown to exhibit capacitance-voltage hysteresis of 20.9V, one of the largest observed in Ge-NC based nonvolatile memories. The Ge NCs were fabricated in an oxide of 30nm thickness by ion implantation with 30keV Ge₂⁻ ions to an equivalent fluence of 1×10¹⁶Gecm⁻² followed by annealing at 950 °C for 10min. Secondary ion mass spectroscopy and transmission electron microscopy demonstrate the existence of Ge NCs whose average distance from the SiO₂∕Siinterface is about 6.7nm. It is shown that the memory effect is a likely consequence of charge trapping at Ge NCs and that it is enhanced by accurately controlling the distribution of Ge NCs with respect to the Si∕SiO₂interface.This work was partially supported by the QuantumFunctional
Semiconductor Research Center in Dongguk University
and by the National Program for Tera Level Nano
Devices through MOST. S.-H.C. acknowledges partial support
from the National Research Program for the 0.1 Terabit
Non-Volatile Memory Development sponsored by Korea
Ministry of Science & Technology. R.G.E. additionally acknowledges
the Australian Research Council for their partial
financial support of this work
Experimental validation of sound field control with a circular double-layer array of loudspeakers.
Dual neutral variables and knot solitons in triplet superconductors
In this paper we derive a dual presentation of free energy functional for
spin-triplet superconductors in terms of gauge-invariant variables. The
resulting equivalent model in ferromagnetic phase has a form of a version of
the Faddeev model. This allows one in particular to conclude that spin-triplet
superconductors allow formation of stable finite-length closed vortices (the
knotted solitons).Comment: Replaced with version published in PRL (added a discussion of the
effect of the coupling of the fields {\vec s} and {\vec C} on knot
stability). Latest updates of the paper and miscellaneous links related to
knotted solitons are also available at the homepage of the author
http://www.teorfys.uu.se/PEOPLE/egor/ . Animations of knotted solitons by
Hietarinta and Salo are available at
http://users.utu.fi/h/hietarin/knots/c45_p2.mp
- …