25,339 research outputs found
Perturbing Around A Warped Product Of AdS_4 and Seven-Ellipsoid
We compute the spin-2 Kaluza-Klein modes around a warped product of AdS_4 and
a seven-ellipsoid. This background with global G_2 symmetry is related to a
U(N) x U(N) N=1 superconformal Chern-Simons matter theory with sixth order
superpotential. The mass-squared in AdS_4 is quadratic in G_2 quantum number
and KK excitation number. We determine the dimensions of spin-2 operators using
the AdS/CFT correspondence. The connection to N=2 theory preserving SU(3) x
U(1)_R is also discussed.Comment: 21pp; The second and last paragraphs of section 2, the footnotes 1
and 2 added and to appear in JHE
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
Geometrically Induced Phase Transitions at Large N
Utilizing the large N dual description of a metastable system of branes and
anti-branes wrapping rigid homologous S^2's in a non-compact Calabi-Yau
threefold, we study phase transitions induced by changing the positions of the
S^2's. At leading order in 1/N the effective potential for this system is
computed by the planar limit of an auxiliary matrix model. Beginning at the two
loop correction, the degenerate vacuum energy density of the discrete confining
vacua split, and a potential is generated for the axion. Changing the relative
positions of the S^2's causes discrete jumps in the energetically preferred
confining vacuum and can also obstruct direct brane/anti-brane annihilation
processes. The branes must hop to nearby S^2's before annihilating, thus
significantly increasing the lifetime of the corresponding non-supersymmetric
vacua. We also speculate that misaligned metastable glueball phases may
generate a repulsive inter-brane force which stabilizes the radial mode present
in compact Calabi-Yau threefolds.Comment: 47 pages, 7 figure
Meta-Stable Brane Configurations by Adding an Orientifold-Plane to Giveon-Kutasov
In hep-th/0703135, they have found the type IIA intersecting brane
configuration where there exist three NS5-branes, D4-branes and anti-D4-branes.
By analyzing the gravitational interaction for the D4-branes in the background
of the NS5-branes, the phase structures in different regions of the parameter
space were studied in the context of classical string theory. In this paper, by
adding the orientifold 4-plane and 6-plane to the above brane configuration, we
describe the intersecting brane configurations of type IIA string theory
corresponding to the meta-stable nonsupersymmetric vacua of these gauge
theories.Comment: 21 pp, 6 figures; reduced bytes of figures, DBI action analysis added
and to appear in JHE
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
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
Efficient Schemes for Reducing Imperfect Collective Decoherences
We propose schemes that are efficient when each pair of qubits undergoes some
imperfect collective decoherence with different baths. In the proposed scheme,
each pair of qubits is first encoded in a decoherence-free subspace composed of
two qubits. Leakage out of the encoding space generated by the imperfection is
reduced by the quantum Zeno effect. Phase errors in the encoded bits generated
by the imperfection are reduced by concatenation of the decoherence-free
subspace with either a three-qubit quantum error correcting code that corrects
only phase errors or a two-qubit quantum error detecting code that detects only
phase errors, connected with the quantum Zeno effect again.Comment: no correction, 3 pages, RevTe
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