4,453 research outputs found
D-branes in Massive IIA and Solitons in Chern-Simons Theory
We investigate D2-branes and D4-branes parallel to D8-branes. The low energy
world volume theory on the branes is non-supersymmetric Chern-Simons theory. We
identify the fundamental strings as the anyons of the 2+1 Chern-Simons theory
and the D0-branes as solitons. The Chern-Simons theory with a boundary is
modeled using NS 5-branes with ending D6-branes. The brane set-up provides for
a graphical description of anomaly inflow. We also model the 4+1 Chern-Simons
theory using branes and conjecture that D4-branes with a boundary describes a
supersymmetric version of Kaplan's theory of chiral fermions.Comment: 22 pages, 4 figures, harvmac, epsf, references added, sec 4.2 adde
True Airspeed Measurement by Ionization-Tracer Technique
Ion bundles produced in a pulse-excited corona discharge are used as tracers with a radar-like pulse transit-time measuring instrument in order to provide a measurement of airspeed that is independent of all variables except time and distance. The resulting instrumentation need not project into the air stream and, therefore, will not cause any interference in supersonic flow. The instrument was tested at Mach numbers ranging from 0.3 to 3.8. Use of the proper instrumentation and technique results in accuracy of the order of 1 percent
Type IIA Superstrings, Chiral Symmetry, and N=1 4D Gauge Theory Dualities
We study N=1 four dimensional gauge theories as the world volume theory of
D4-branes between NS 5-branes. We find constructions for a number of known
field theory dualities involving groups, coupled by
matter fields F in the representation, in terms of branes of
type IIA string theory. The dual gauge group follows from simply reversing the
ordering of the NS 5-branes and the D6-branes while conserving magnetic charge
on the world volume of the branes. We interpret many field theory phenomena
such as deformation of the superpotential W = \Tr (F\tilde F)^{k+1} in terms
of the position of branes. By looking to D-branes for guidance, we find new N=1
dualities involving arbitrary numbers of gauge groups. We propose a mechanism
for enhanced chiral symmetry in the brane construction which, we conjecture, is
associated with tensionless threebranes in six dimensions.Comment: 32 pages, 9 figures, uses harvmac, tables, and eps
Surprisingly Little Population Genetic Structure In A Fungus-Associated Beetle Despite Its Exploitation Of Multiple Hosts
In heterogeneous environments, landscape features directly affect the structure of genetic variation among populations by functioning as barriers to gene flow. Resource-associated population genetic structure, in which populations that use different resources (e.g., host plants) are genetically distinct, is a well-studied example of how environmental heterogeneity structures populations. However, the pattern that emerges in a given landscape should depend on its particular combination of resources. If resources constitute barriers to gene flow, population differentiation should be lowest in homogeneous landscapes, and highest where resources exist in equal proportions. In this study, we tested whether host community diversity affects population genetic structure in a beetle (Bolitotherus cornutus) that exploits three sympatric host fungi. We collected B.cornutus from plots containing the three host fungi in different proportions and quantified population genetic structure in each plot using a panel of microsatellite loci. We found no relationship between host community diversity and population differentiation in this species; however, we also found no evidence of resource-associated differentiation, suggesting that host fungi are not substantial barriers to gene flow. Moreover, we detected no genetic differentiation among B.cornutus populations separated by several kilometers, even though a previous study demonstrated moderate genetic structure on the scale of a few hundred meters. Although we found no effect of community diversity on population genetic structure in this study, the role of host communities in the structuring of genetic variation in heterogeneous landscapes should be further explored in a species that exhibits resource-associated population genetic structure
Exact Solutions of Exceptional Gauge Theories from Toric Geometry
We derive four dimensional gauge theories with exceptional groups ,
, , and with matter, by starting from the duality between the
heterotic string on and F-theory on a elliptically fibered Calabi-Yau
3-fold. This configuration is compactified to four dimensions on a torus, and
by employing toric geometry, we compute the type IIB mirrors of the Calabi-Yaus
of the type IIA string theory. We identify the Seiberg-Witten curves describing
the gauge theories as ALE spaces fibered over a base.Comment: 18 pages, 5 figures, uses harvmac and eps
Patterns of Duality in N=1 SUSY Gauge Theories
We study the patterns in the duality of a wide class of N=1 supersymmetric
gauge theories in four dimensions. We present many new generalizations of the
classic duality models of Kutasov and Schwimmer, which have themselves been
generalized numerous times in works of Intriligator, Leigh and the present
authors. All of these models contain one or two fields in a two-index tensor
representation, along with fields in the defining representation. The
superpotential for the two-index tensor(s) resembles A_k or D_k singularity
forms, generalized from numbers to matrices. Looking at the ensemble of these
models, classifying them by superpotential, gauge group, and ``level'' -- for
terminology we appeal to the architecture of a typical European-style theatre
-- we identify emerging patterns and note numerous interesting puzzles.Comment: 34 pages, 4 figures, uses harvmac and table
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