155 research outputs found
Semiclassical strings in marginally deformed toric AdS/CFT
We study string solutions in the beta-deformed Sasaki-Einstein gauge/gravity
dualities. We find that the BPS point-like strings move in the submanifolds
where the two U(1) circles shrink to zero size. In the corresponding T^3
fibration description, the strings live on the edges of the polyhedron, where
the T^3 fibration degenerates to T^1. Moreover, we find that for each deformed
Sasaki-Einstein manifold the BPS string solutions exist only for particular
values of the deformation parameter. Our results imply that in the dual field
theory the corresponding BPS operators exist only for these particular values
of the deformation parameter we find. We also examine the non-BPS strings,
derive their dispersion relations and compare them with the undeformed ones.
Finally, we comment on the range of the validity of our solutions and their
dependence on the deformation parameter.Comment: 29 pages, 9 figure
IxodIdae tIcks of small rumInants In the regIon of ParvomaI, southern BulgarIa
, 2014. ixodidae ticks of small ruminants in the region of parvomai, Southern Bulgaria. Bulg. J. Agric. Sci., The species composition and the distribution of ticks from the family Ixodidae, invading domestic goats (Capra aegagrus hircus) and sheep (Ovis aries) near parvomay (region of plovdiv) were studied. The indicators of an invasion (extension invasion and intensity of invasion) and the seasonal changes in the invasion of goats and sheep by tick species were found out. The daily activity of Ixodes ricinus in a habitat near the Gradina village was observed. 637 specimens of goats and 810 specimens of sheep from 12 farms in different villages in the parvomay Municipality were examined, the study was conducted in all four seasons. it is found out that goats and sheep in the regions investigated is invaded by 7 species of ixodidae ticks -Rhipicephalus bursa, Rhipicephalus sanguineus, Ixodes ricinus, Dermacentor marginatus, Haemaphysalis sulcata, Haemaphysalis punctata and Hyaloma plumbeum. The predominant invasive species in both animals is Rhipicephalus bursa. The maximum of invasion in both host species was identified -in the spring by Ixodes ricinus and Dermacentor marginatus; in the summer -the species Rhipicephalus bursa and Rhipicephalus sanguineus; in the spring and autumn seasons -by Haemaphysalis sulcata and Haemaphysalis punctata. Single specimens from the species Hyaloma plumbeum were found in March and november. Changes in the daily activity of ticks of the species Ixodes ricinus were reported -related to the fluctuations of temperature and relative humidity and the solar radiation
Holographic 3-point function at one loop
We explore the recent weak/strong coupling match of three-point functions in
the AdS/CFT correspondence for two semi-classical operators and one light
chiral primary operator found by Escobedo et al. This match is between the
tree-level three-point function with the two semi-classical operators described
by coherent states while on the string side the three-point function is found
in the Frolov-Tseytlin limit. We compute the one-loop correction to the
three-point function on the gauge theory side and compare this to the
corresponding correction on the string theory side. We find that the
corrections do not match. Finally, we discuss the possibility of further
contributions on the gauge theory side that can alter our results.Comment: 24 pages, 2 figures. v2: Typos fixed, Ref. added, figure improved.
v3: Several typos and misprints fixed, Ref. updated, figures improved, new
section 2.3 added on correction from spin-flipped coherent state,
computations on string theory side improve
Micromechanical fatigue experiments for validation of microstructure-sensitive fatigue simulation models
Crack initiation governs high cycle fatigue life and is sensitive to microstructural details. While corresponding microstructure-sensitive models are available, their validation is difficult. We propose a validation framework where a fatigue test is mimicked in a sub-modeling simulation by embedding the measured microstructure into the specimen geometry and adopting an approximation of the experimental boundary conditions. Exemplary, a phenomenological crystal plasticity model was applied to predict deformation in ferritic steel (EN1.4003). Hotspots in commonly used fatigue indicator parameter maps are compared with damage segmented from micrographs. Along with the data, the framework is published for benchmarking future micromechanical fatigue models
Micromechanical fatigue experiments for validation of microstructure-sensitive fatigue simulation models
Crack initiation governs high cycle fatigue life and is sensitive to microstructural details. While corresponding microstructure-sensitive models are available, their validation is difficult. We propose a validation framework where a fatigue test is mimicked in a sub-modeling simulation by embedding the measured microstructure into the specimen geometry and adopting an approximation of the experimental boundary conditions. Exemplary, a phenomenological crystal plasticity model was applied to predict deformation in ferritic steel (EN1.4003). Hotspots in commonly used fatigue indicator parameter maps are compared with damage segmented from micrographs. Along with the data, the framework is published for benchmarking future micromechanical fatigue models
Holographic three-point functions for short operators
We consider holographic three-point functions for operators dual to short
string states at strong coupling in N=4 super Yang-Mills. We treat the states
as point-like as they come in from the boundary but as strings in the
interaction region in the bulk. The interaction position is determined by
saddle point, which is equivalent to conservation of the canonical momentum for
the interacting particles, and leads to conservation of their conformal
charges. We further show that for large dimensions the rms size of the
interaction region is small compared to the radius of curvature of the AdS
space, but still large compared to the string Compton wave-length. Hence, one
can approximate the string vertex operators as flat-space vertex operators with
a definite momentum, which depends on the conformal and R-charges of the
operator. We then argue that the string vertex operator dual to a primary
operator is chosen by satisfying a twisted version of Q^L=Q^R, up to spurious
terms. This leads to a unique choice for a scalar vertex operator with the
appropriate charges at the first massive level. We then comment on some
features of the corresponding three-point functions, including the application
of these results to Konishi operators.Comment: 24 pages; v2: References added, typos fixed, minor change
Matching three-point functions of BMN operators at weak and strong coupling
The agreement between string theory and field theory is demonstrated in the
leading order by providing the first calculation of the correlator of three
two-impurity BMN states with all non-zero momenta. The calculation is performed
in two completely independent ways: in field theory by using the large-
perturbative expansion, up to the terms subleading in finite-size, and in
string theory by using the Dobashi-Yoneya 3-string vertex in the leading order
of the Penrose expansion. The two results come out to be completely identical.Comment: 14 pages, 1 figur
Investigation of melt-grown dilute GaAsN and GaInAsN nanostructures for photovoltaics
AbstractThe present work demonstrates the possibility to use liquid phase epitaxy to incorporate nitrogen in epitaxial GaAsN/GaAs and GaInAsN/GaAs heterostructures, including nanoscaled ones. The structures are grown from Ga - and GaIn - melts containing polycrystalline GaN as a nitrogen source. The red shift of the absorption spectra corresponds to nitrogen content in the epitaxial layers near or less than 0.2 at %. Photoluminescence spectra of dilute nitride GaAsN and GaInAsN show emission from localized nitrogen states - N-nanoclusters of more than two N atoms. These studies show that the melt grown dilute GaAsN and GaInAsN nanostructures can be used for solar cells with extended long wavelength edge
Three Spin Spiky Strings in beta-deformed Background
We study rigidly rotating strings in -deformed
background with one spin along AdS and two angular momenta along . We
find the spiky string solutions and present the dispersion relation among
various charges in this background. We further generalize the result to the
case of four angular momenta along .Comment: 12 pages, minor corrections, added references, to appear in JHE
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