19,185 research outputs found
D-brane Bound States and the Generalised ADHM Construction
We discuss the sigma model description of a D-string bound to k D-fivebranes
in type I string theory. The effective theory is an (0,4) supersymmetric
hyper-Kahler with torsion sigma model on the moduli space of Sp(k) instantons
on R^4. Upon toroidal compactification to five dimensions the model is related
to the type II picture where the target space is a symmetric product of K3's.Comment: 17 pages Phyzzx. Minor corrections, to appear in Nucl. Phys.
Emergent Time and the M5-Brane
We consider the maximal super-Yang-Mills theory in 5 Euclidean dimensions
with SO(5) R-symmetry and 16 supersymmetries. We argue that the strong coupling
limit of this theory (with a possible UV completion) has an emergent time
dimension and gives a description of the 5+1 dimensional Lorentz invariant
(2,0) theory of the M5-brane, compactified on a timelike circle with radius
R=g^2/4\pi^2 . Our discussion involves issues of quantization of Euclidean
theories without time.Comment: 1+40 page
Non-Abelian Born-Infeld Action and Solitons for Critical Non-BPS Branes
The non-abelian flat directions in the tachyon potential of stable non-BPS
branes recently found are shown to persist to all orders in alpha' at tree
level in the string coupling. We also obtain the non-abelian Born-Infeld action
including the tachyon potential for a stack of stable non-BPS branes on a
critical orbifold. Finally we discuss stable soliton states on the non-BPS
brane.Comment: 12+1 pages, Latex. Typos, a reference and the discussion of the
monopole solution are correcte
Ring element dynamic stresses
The stresses in the CTRAPRG and CTRIARG ring elements are not calculated for any of the dynamic solutions in the current COSMIC version of NASTRAN. A DMAP alter sequence for Solution 8 and post-processing program, NASTPOST, are presented to calculate these stresses. Test cases are used which describe the method. The stiffness and the consistent versus concentrated mass problems ascribed to this element are reviewed. The DMAP alter sequence introduces Solution 8 displacements to a Solution 1 module to calculate real and imaginary stress components during the execution of Solution 8. The post-processor, NASTPOST, calculates the magnitude/phase stress results. The DMAP sequence was written specifically for level 52 MSC/NASTRAN, but can certainly be used for any COSMIC version with slight modification
M-Theory and Hypercharge
We discuss the possibility that the electro-weak and strong interactions
arise as the low energy effective description of branes in M-theory. As a step
towards constructing such a model we show how one can naturally obtain
SU(N_1)\times SU(N_2)\times U(1) gauge theories from branes, including matter
in the bi-fundamental representation of SU(N_1)\times SU(N_2) which are
fractionally charged under U(1).Comment: 29 pages Phyzzx. Two figure
High-resolution spectroscopy of V854 Cen in decline - Absorption and emission lines of C_2 molecules
High-resolution optical spectra of the R Coronae Borealis (RBC) star V854
Centauri in the early stages of a decline show, in addition to the features
reported for other RCBs in decline, narrow absorption lines from the C_2
Phillips system. The low rotational temperature, T_rot = 1150K, of the C_2
ground electronic state suggests the cold gas is associated with the developing
shroud of carbon dust. These absorption lines were not seen at a fainter
magnitude on the rise from minimum light nor at maximum light. This is the
first detection of cold gas around a RCB star.Comment: 5 pages, 5 figures, accepted for publication by Monthly Notices of
the Royal Society of Astronom
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