3,465 research outputs found
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
Phase transition in the Sznajd model with independence
We propose a model of opinion dynamics which describes two major types of
social influence -- conformity and independence. Conformity in our model is
described by the so called outflow dynamics (known as Sznajd model). According
to sociologists' suggestions, we introduce also a second type of social
influence, known in social psychology as independence. Various social
experiments have shown that the level of conformity depends on the society. We
introduce this level as a parameter of the model and show that there is a
continuous phase transition between conformity and independence
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
Supersymmetric Boost on Intersecting D-branes
We study the effect of the Born-Infeld electric field on the supersymmetric
configuration of various composite D-branes. We show that the generic values of
the electric field do not affect the supersymmetry but, as it approaches
keeping the magnetic field finite, various combinations of the
magnetic fields allow up to 8 supersymmetries. We also explore the unbroken
supersymmetries for two intersecting D-strings which are in uniform or relative
motion. For a finite uniform Lorentz boost, 16 supersymmetries are guaranteed
only when they are parallel. For an infinite one, 8 supersymmetries are
preserved only when both the D-strings are oriented to the forward or backward
direction of the boost. Under a finite relative boost, 8 supersymmetries are
preserved only when the intersecting angle is less than and the
intersecting point moves at the speed of light. As for an infinite relative
boost, 8 supersymmetries are preserved regardless of the values of the
intersecting angle.Comment: 27 pages using REVTeX4, 7 figure
Reverse geometric engineering of singularities
One can geometrically engineer supersymmetric field theories theories by
placing D-branes at or near singularities. The opposite process is described,
where one can reconstruct the singularities from quiver theories. The
description is in terms of a noncommutative quiver algebra which is constructed
from the quiver diagram and the superpotential. The center of this
noncommutative algebra is a commutative algebra, which is the ring of
holomorphic functions on a variety V. If certain algebraic conditions are met,
then the reverse geometric engineering produces V as the geometry that D-branes
probe. It is also argued that the identification of V is invariant under
Seiberg dualities.Comment: 17 pages, Latex. v2: updates reference
Elliptic supertube and a Bogomol'nyi-Prasad-Sommerfield D2-brane--anti-D2-brane Pair
An exact solution, in which a D2-brane and an anti-D2-brane are connected by
an elliptically tubular D2-brane, is obtained without any junction condition.
The solution is shown to preserve one quarter of the supersymmetries of the
type-IIA Minkowski vacuum. We show that the configuration cannot be obtained by
"blowing-up" from some inhomogeneously D0-charged superstrings. The BPS bound
tells us that it is rather composed of D0-charged D2-brane-anti-D2-brane pair
and a strip of superstrings connecting them. We obtain the correction to the
charges of the string end points in the constant magnetic background.Comment: v3. 12 pages, journal version; title changed, length trimmed to fit
for Rapid Communication forma
The Hamiltonian Dynamics of Bounded Spacetime and Black Hole Entropy: The Canonical Method
From first principles, I present a concrete realization of Carlip's idea on
the black hole entropy from the conformal field theory on the horizon in any
dimension. New formulation is free of inconsistencies encountered in Carlip's.
By considering a correct gravity action, whose variational principle is well
defined at the horizon, I a correct Virasoro generator for
the surface deformations at the horizon through the canonical method. The
existence of the classical Virasoro algebra is crucial in obtaining an operator
Virasoro algebra, through canonical quantization, which produce the right
central charge and conformal weight for the semiclassical
black hole entropy. The coefficient of proportionality depends on the choice of
ground state, which has to be put in by hand to obtain the correct numerical
factor 1/4 of the Bekenstein-Hawking (BH) entropy. The appropriate ground state
is different for the rotating and the non-rotating black holes but otherwise it
has a for a wide variety of black holes. As a byproduct of my
results, I am led to conjecture that {\it non-commutativity of taking the limit
to go to the horizon and computing variation is proportional to the Hamiltonian
and momentum constraints}. It is shown that almost all the known uncharged
black hole solutions satisfy the conditions for the universal entropy formula.Comment: Much details omitted, references added, accepted in Nucl. Phys.
Hawking Temperature in Taub-NUT (A)dS spaces via the Generalized Uncertainty Principle
Using the extended forms of the Heisenberg uncertainty principle from string
theory and the quantum gravity theory, we drived Hawking temperature of a
Taub-Nut-(A)dS black hole. In spite of their distinctive natures such as
asymptotically locally flat and breakdown of the area theorem of the horizon
for the black holes, we show that the corrections to Hawking temperature by the
generalized versions of the the Heisenberg uncertainty principle increases like
the Schwarzschild-(A)dS black hole and give the reason why the Taub-Nut-(A)dS
metric may have AdS/CFT dual picture.Comment: version published in General Relativity and Gravitatio
Speciation of phosphorus in a fertilized, reduced-till soil system: in-field treatment incubation study
Citation: Khatiwada, Raju, Ganga M. Hettiarachchi, David B. Mengel, and Mingwei Fei. âSpeciation of Phosphorus in a Fertilized, Reduced-Till Soil System: In-Field Treatment Incubation Study.â Soil Science Society of America Journal 76, no. 6 (2012): 2006â18. https://doi.org/10.2136/sssaj2011.0299.Phosphorus management in reduced-tillage systems is a great concern for farmers. Conclusive positive results of deep-banding P fertilizers compared with broadcast application and the chemistry of reduced-tillage systems remain unclear. Knowledge of the dominant solid P species present in soil following application of P fertilizers and the resulting potential P availability would help us understand and efficiently manage P in reduced-tillage systems. The objective of this research was to study the influence of placement (broadcast vs. deep-band P), fertilizer source (granular vs. liquid P), and time on the reaction products of P under field conditions. Changes in soil pH, resin-extractable P, total P, and speciation of P were determined at different distances from the point of fertilizer application at 5 wk and 6 mo after P application at a rate of 75 kg haâ1 to a soil system that was under long-term reduced tillage. Resin-extractable P was lower for broadcast treatments compared with deep-band treatments for both time periods. Resin-extractable P was greater in the liquid P-treated soils than in the granular P-treated soils. Speciation results showed that granular P fertilizers tended to form FeâP-like forms, whereas liquid forms remained in adsorbed P-like forms in the soil 5 wk after application; moreover, speciation results showed granular P fertilizers precipitated less when deep-banded. During the 6-mo period following application, reaction products of broadcast granular, broadcast liquid, and deep-band granular fertilizers transformed to Ca-phosphate or mixtures of Ca-, Fe- and adsorbed-phosphate-like forms, whereas deep-band liquid P remained as mainly adsorbed P-like forms. Deep-banding of P would most likely provide a solution that is both agronomically and environmentally efficient for reduced-till farmers
Super D-Helix
We study `Myers effect' for a bunch of -branes with superstrings
moving in one direction along the branes. We show that the `blown-up'
configuration is the helical -brane, which is self-supported from collapse
by the axial momentum flow. The tilting angle of the helix is determined by the
number of -branes. The radius of the helix is stabilized to a certain value
depending on the number of -branes and the momentum carried by
superstrings. This is actually T-dual version of the supertube recently found
as the `blown-up' configuration of a bunch of superstrings carrying
-brane charge. It is found that the helical configuration preserves
one quarter of the supersymmetry of vacuum.Comment: 13 pages using REVTeX macro, V.3: added references, corrected typos
in the Killing spinor relations, and added discussions on D1/D
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