1,030 research outputs found
Geometric Aspects of D-branes and T-duality
We explore the differential geometry of T-duality and D-branes. Because
D-branes and RR-fields are properly described via K-theory, we discuss the
(differential) K-theoretic generalization of T-duality and its application to
the coupling of D-branes to RR-fields. This leads to a puzzle involving the
transformation of the A-roof genera in the coupling.Comment: 26 pages, JHEP format, uses dcpic.sty; v2: references added, v3:
minor change
On the multiplicity of the O-star Cyg OB2 #8A and its contribution to the gamma-ray source 3EG J2033+4118
We present the results of an intensive spectroscopic campaign in the optical
waveband revealing that Cyg OB2 #8A is an O6 + O5.5 binary system with a period
of about 21.9 d. Cyg OB2 #8A is a bright X-ray source, as well as a non-thermal
radio emitter. We discuss the binarity of this star in the framework of a
campaign devoted to the study of non-thermal emitters, from the radio waveband
to gamma-rays. In this context, we attribute the non-thermal radio emission
from this star to a population of relativistic electrons, accelerated by the
shock of the wind-wind collision. These relativistic electrons could also be
responsible for a putative gamma-ray emission through inverse Compton
scattering of photospheric UV photons, thus contributing to the yet
unidentified EGRET source 3EG J2033+4118.Comment: 8 pages, 4 figures, conference on "The Multiwavelength Approach to
Gamma-Ray Sources", to appear in Ap&S
Rare-earth doped chalcogenide glass fibre laser
We report on the first laser action in a rare-earth doped chalcogenide glass fibre. Laser action at 1080nm was obtained in a 22mm long gallium lanthanum sulphide glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour
Holographic Coulomb Branch Flows with N=1 Supersymmetry
We obtain a large, new class of N=1 supersymmetric holographic flow
backgrounds with U(1)^3 symmetry. These solutions correspond to flows toward
the Coulomb branch of the non-trivial N=1 supersymmetric fixed point. The
massless (complex) chiral fields are allowed to develop vevs that are
independent of their two phase angles, and this corresponds to allowing the
brane to spread with arbitrary, U(1)^2 invariant, radial distributions in each
of these directions. Our solutions are "almost Calabi-Yau:" The metric is
hermitian with respect to an integrable complex structure, but is not Kahler.
The "modulus squared" of the holomorphic (3,0)-form is the volume form, and the
complete solution is characterized by a function that must satisfy a single
partial differential equation that is closely related to the Calabi-Yau
condition. The deformation from a standard Calabi-Yau background is driven by a
non-trivial, non-normalizable 3-form flux dual to a fermion mass that reduces
the supersymmetry to N=1. This flux also induces dielectric polarization of the
D3-branes into D5-branes.Comment: 22 pages; harvmac. Typos corrected;small improvements in presentatio
Developing Antidote Controlled Antiplatelet Therapies By Targeting The Vwf ‐ Gp Ib‐Ix‐V Interaction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106054/1/jth02400.pd
Brane/Flux Annihilation and the String Dual of a Non-Supersymmetric Field Theory
We consider the dynamics of p anti-D3 branes inside the Klebanov-Strassler
geometry, the deformed conifold with M units of RR 3-form flux around the S^3.
We find that for p<<M the system relaxes to a nonsupersymmetric NS 5-brane
``giant graviton'' configuration, which is classically stable, but quantum
mechanically can tunnel to a nearby supersymmetric vacuum with M-p D3 branes.
This decay mode is exponentially suppressed and proceeds via the nucleation of
an NS 5-brane bubble wall. We propose a dual field theory interpretation of the
decay as the transition between a nonsupersymmetric ``baryonic'' branch and a
supersymmetric ``mesonic'' branch of the corresponding SU(2M-p)x SU(M-p) low
energy gauge theory. The NS 5-brane tunneling process also provides a simple
explanation of the geometric transition by which D3-branes can dissolve into
3-form flux.Comment: 27 pages, 4 figures, typo correcte
The (p,q) String Tension in a Warped Deformed Conifold
We find the tension spectrum of the bound states of p fundamental strings and
q D-strings at the bottom of a warped deformed conifold. We show that it can be
obtained from a D3-brane wrapping a 2-cycle that is stabilized by both electric
and magnetic fluxes. Because the F-strings are Z_M-charged with non-zero
binding energy, binding can take place even if (p,q) are not coprime.
Implications for cosmic strings are briefly discussed.Comment: 17 pages, 1 figur
Type IIA Orientifold Limit of M-Theory on Compact Joyce 8-Manifold of Spin(7)-Holonomy
We show that M-theory compactified on a compact Joyce 8-manifold of
-holonomy, which yields an effective theory in with = 1
supersymmetry, admits at some special points in it moduli space a description
in terms of type IIA theory on an orientifold of compact Joyce 7-manifold of
-holonomy. We find the evidence in favour of this duality by computing the
massless spectra on both M-thory side and type IIA side. For the latter, we
compute the massless spectra by going to the orbifold limit of the Joyce
7-manifold.Comment: 26 pages, 2 eps figures, Latex file, two references and one footnote
added, corrected some typo
Width of Sunspot Generating Zone and Reconstruction of Butterfly Diagram
Based on the extended Greenwich-NOAA/USAF catalogue of sunspot groups it is
demonstrated that the parameters describing the latitudinal width of the
sunspot generating zone (SGZ) are closely related to the current level of solar
activity, and the growth of the activity leads to the expansion of SGZ. The
ratio of the sunspot number to the width of SGZ shows saturation at a certain
level of the sunspot number, and above this level the increase of the activity
takes place mostly due to the expansion of SGZ. It is shown that the mean
latitudes of sunspots can be reconstructed from the amplitudes of solar
activity. Using the obtained relations and the group sunspot numbers by Hoyt
and Schatten (1998), the latitude distribution of sunspot groups ("the Maunder
butterfly diagram") for the 18th and the first half of the 19th centuries is
reconstructed and compared with historical sunspot observations.Comment: 16 pages, 11 figures; accepted by Solar Physics; the final
publication will be available at www.springerlink.co
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