24,133 research outputs found
Meta-Stable Brane Configurations by Higher Order Polynomial Superpotential
We construct the type IIA nonsupersymmetric meta-stable brane configuration
consisting of (2k+1) NS5-branes and D4-branes where the electric gauge theory
superpotential has an order (2k+2) polynomial for the bifundamentals. We find a
rich pattern of nonsupersymmetric meta-stable states as well as the
supersymmetric stable ones. By adding the orientifold 4-plane to this brane
configuration, we also describe the intersecting brane configuration of type
IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of
corresponding gauge theory.Comment: 27pp, 8 figures; some footnotes added; to appear in IJMP
The Full Structure of Quantum Super- Algebra
We present the complete structure of the nonlinear super extension of
Polyakov-Bershadsky, , algebra with the generic central charge, ,
at the {\it quantum} level. It contains extra two pairs of fermionic currents
with integer spins 1 and 2, besides the currents of superconformal and
algebras. For limit, the algebra reduces to
the classical one, which has been studied previously. The 'hybrid' field
realization of this algebra is also discussed.Comment: 8 pages, latex, no figure
Explicit Construction of Spin 4 Casimir Operator in the Coset Model
We generalize the Goddard-Kent-Olive (GKO) coset construction to the
dimension 5/2 operator for and compute the fourth order
Casimir invariant in the coset model with the generic unitary minimal
series that can be viewed as perturbations of the
limit, which has been investigated previously in the realization of
free fermion model.Comment: 11 page
Quantum N=2 super Algebra In Superspace
We discuss the N=2 extension of Polyakov-Bershadsky algebra with
the generic central charge, , at the quantum level in superspace. It
contains, in addition to the spin 1 N=2 stress tensor, the spins
bosonic and spins fermionic supercurrents satisfying the first class
nonlinear chiral constraints. In the limit, the ``classical''
N=2 algebra is recovered.Comment: 8 pages, LaTeX, name of the first author extende
Maximum Matching in Turnstile Streams
We consider the unweighted bipartite maximum matching problem in the one-pass
turnstile streaming model where the input stream consists of edge insertions
and deletions. In the insertion-only model, a one-pass -approximation
streaming algorithm can be easily obtained with space , where
denotes the number of vertices of the input graph. We show that no such result
is possible if edge deletions are allowed, even if space is
granted, for every . Specifically, for every , we show that in the one-pass turnstile streaming model, in order to compute
a -approximation, space is
required for constant error randomized algorithms, and, up to logarithmic
factors, space is sufficient. Our lower bound result is
proved in the simultaneous message model of communication and may be of
independent interest
More on Meta-Stable Brane Configuration
We describe the intersecting brane configuration of type IIA string theory
corresponding to the meta-stable nonsupersymmetric vacua in four dimensional
N=1 supersymmetric SU(N_c) gauge theory with an antisymmetric flavor, a
conjugate symmetric flavor, eight fundamental flavors, m_f fundamental flavors
and m_f antifundamental flavors. This is done by analyzing the N=1
supersymmetric SU(2m_f-N_c+4) magnetic gauge theory with dual matters and the
corresponding dual superpotential.Comment: 20 pp, 3 figures; Pages 11,12, and 14 improved; to appear in CQ
Meta-Stable Brane Configurations with Seven NS5-Branes
We present the intersecting brane configurations consisting of NS-branes,
D4-branes(and anti D4-branes) and O6-plane, of type IIA string theory
corresponding to the meta-stable nonsupersymmetric vacua in four dimensional
N=1 supersymmetric SU(N_c) x SU(N_c') x SU(N_c'') gauge theory with a symmetric
tensor field, a conjugate symmetric tensor field and bifundamental fields. We
also describe the intersecting brane configurations of type IIA string theory
corresponding to the nonsupersymmetric meta-stable vacua in the above gauge
theory with an antisymmetric tensor field, a conjugate symmetric tensor field,
eight fundamental flavors and bifundamentals. These brane configurations
consist of NS-branes, D4-branes(and anti D4-branes), D6-branes and O6-planes.Comment: 34pp, 9 figures; Improved the draft and added some footnotes; Figure
1, footnote 7 and captions of Figures 7,8,9 added or improved and to appear
in CQ
Local order measurement in SnGe alloys and monolayer Sn films on Si with reflection electron energy loss spectrometry
Measurements of local order are demonstrated in Sn-containing alloys and epitaxial monolayer thickness films by analysis of extended-edge energy loss fine structure (EXELFS) data obtained by reflection electron energy loss spectrometry (REELS). These measurements of short-range order provide a complement to the chemical information obtained with REELS and long-range order obtained using reflection high energy electron diffraction. The results suggest that EXELFS measurements are practical for samples mounted on the growth manipulator in a molecular beam epitaxy chamber. Advantages and limitations of reflection EXELFS are discussed
Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites
Neutron scattering measurements on a magnetoresistive manganite
La(CaSr)MnO show that uncorrelated
dynamic polaronic lattice distortions are present in both the orthorhombic (O)
and rhombohedral (R) paramagnetic phases. The uncorrelated distortions do not
exhibit any significant anomaly at the O-to-R transition. Thus, both the
paramagnetic phases are inhomogeneous on the nanometer scale, as confirmed
further by strong damping of the acoustic phonons and by the anomalous
Debye-Waller factors in these phases. In contrast, recent x-ray measurements
and our neutron data show that polaronic correlations are present only in the O
phase. In optimally doped manganites, the R phase is metallic, while the O
paramagnetic state is insulating (or semiconducting). These measurements
therefore strongly suggest that the {\it correlated} lattice distortions are
primarily responsible for the insulating character of the paramagnetic state in
magnetoresistive manganites.Comment: 10 pages, 8 figures embedde
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