65,530 research outputs found

### On the tau-functions of the Degasperis-Procesi equation

The DP equation is investigated from the point of view of
determinant-pfaffian identities. The reciprocal link between the
Degasperis-Procesi (DP) equation and the pseudo 3-reduction of the $C_{\infty}$
two-dimensional Toda system is used to construct the N-soliton solution of the
DP equation. The N-soliton solution of the DP equation is presented in the form
of pfaffian through a hodograph (reciprocal) transformation. The bilinear
equations, the identities between determinants and pfaffians, and the
$\tau$-functions of the DP equation are obtained from the pseudo 3-reduction of
the $C_{\infty}$ two-dimensional Toda system.Comment: 27 pages, 4 figures, Journal of Physics A: Mathematical and
Theoretical, to be publishe

### Mastering the Master Space

Supersymmetric gauge theories have an important but perhaps under-appreciated
notion of a master space, which controls the full moduli space. For
world-volume theories of D-branes probing a Calabi-Yau singularity X the
situation is particularly illustrative. In the case of one physical brane, the
master space F is the space of F-terms and a particular quotient thereof is X
itself. We study various properties of F which encode such physical quantities
as Higgsing, BPS spectra, hidden global symmetries, etc. Using the plethystic
program we also discuss what happens at higher number N of branes. This letter
is a summary and some extensions of the key points of a longer companion paper
arXiv:0801.1585.Comment: 10 pages, 1 Figur

### The Toric Phases of the Y^{p,q} Quivers

We construct all connected toric phases of the recently discovered $Y^{p,q}$
quivers and show their IR equivalence using Seiberg duality. We also compute
the R and global U(1) charges for a generic toric phase of $Y^{p,q}$.Comment: 14 pages, 3 figure

### Solar stereoscopy - where are we and what developments do we require to progress?

Observations from the two STEREO-spacecraft give us for the first time the
possibility to use stereoscopic methods to reconstruct the 3D solar corona.
Classical stereoscopy works best for solid objects with clear edges.
Consequently an application of classical stereoscopic methods to the faint
structures visible in the optically thin coronal plasma is by no means straight
forward and several problems have to be treated adequately: 1.)First there is
the problem of identifying one dimensional structures -e.g. active region
coronal loops or polar plumes- from the two individual EUV-images observed with
STEREO/EUVI. 2.) As a next step one has the association problem to find
corresponding structures in both images. 3.) Within the reconstruction problem
stereoscopic methods are used to compute the 3D-geometry of the identified
structures. Without any prior assumptions, e.g., regarding the footpoints of
coronal loops, the reconstruction problem has not one unique solution. 4.) One
has to estimate the reconstruction error or accuracy of the reconstructed
3D-structure, which depends on the accuracy of the identified structures in 2D,
the separation angle between the spacecraft, but also on the location, e.g.,
for east-west directed coronal loops the reconstruction error is highest close
to the loop top. 5.) Eventually we are not only interested in the 3D-geometry
of loops or plumes, but also in physical parameters like density, temperature,
plasma flow, magnetic field strength etc. Helpful for treating some of these
problems are coronal magnetic field models extrapolated from photospheric
measurements, because observed EUV-loops outline the magnetic field. This
feature has been used for a new method dubbed 'magnetic stereoscopy'. As
examples we show recent application to active region loops.Comment: 12 Pages, 9 Figures, a Review articl

### Z-D Brane Box Models and Non-Chiral Dihedral Quivers

Generalising ideas of an earlier work \cite{Bo-Han}, we address the problem of constructing Brane Box Models of what we call the Z-D Type from a new point of view, so as to establish the complete correspondence between these brane setups and orbifold singularities of the non-Abelian G generated by Z_k and D_d under certain group-theoretic constraints to which we refer as the BBM conditions. Moreover, we present a new class of ${\cal N}=1$ quiver theories of the ordinary dihedral group d_k as well as the ordinary exceptionals E_{6,7,8} which have non-chiral matter content and discuss issues related to brane setups thereof

### The Splitting of Branes on Orientifold Planes

Continuing the study in hep-th/0004092 and hep-th/0004092, we investigate a
non-trivial string dynamical process related to orientifold planes, i.e., the
splitting of physical NS-branes and D(p+2)-branes on orientifold Op-planes.
Creation or annihilation of physical Dp-branes usually accompanies the
splitting process. In the particular case p=4, we use Seiberg-Witten curves as
an independent method to check the results.Comment: 34 pages, 9 figure

### Asymmetry of the electron spectrum in hole-doped and electron-doped cuprates

Within the t-t'-J model, the asymmetry of the electron spectrum and
quasiparticle dispersion in hole-doped and electron-doped cuprates is
discussed. It is shown that the quasiparticle dispersions of both hole-doped
and electron-doped cuprates exhibit the flat band around the (\pi,0) point
below the Fermi energy. The lowest energy states are located at the
(\pi/2,\pi/2) point for the hole doping, while they appear at the (\pi,0) point
in the electron-doped case due to the electron-hole asymmetry. Our results also
show that the unusual behavior of the electron spectrum and quasiparticle
dispersion is intriguingly related to the strong coupling between the electron
quasiparticles and collective magnetic excitations.Comment: 8 pages, 3 figures, typo corrected, added detailed calculations and
updated figure 3 and references, accepted for publication in Phys. Lett.

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