179 research outputs found
Three-point correlators: Examples from Lunin-Maldacena background
Recently there has been progress on the calculation of three-point functions
with two "heavy" operators via semiclassical methods. We extend this analysis
to the case of the Lunin-Maldacena background, and examine the suggested
procedure for several simple string solutions. By making use of AdS/CFT
duality, we derive the relevant correlation functions of operators belonging to
the dual N=1 superconformal gauge theory, and recover an important relation
connecting the dimensions of "heavy" states and the structure constants.Comment: 11 pages, no figures, incorrect subsection removed, typos fixed,
references added and update
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
Influence of thickeners (microfibrillated cellulose, starch, xanthan gum) on rheological, tribological and sensory properties of low-fat mayonnaises
Microfibrillated cellulose (MFC) is obtained by high-shear treatment of cellulose. MFC is suitable for use as clean-label, low-calorie thickener in semi-solid foods such as mayonnaises due to its high water holding capacity. The aim of this study was to determine the effect of type and concentration of thickener on rheological, tribological and sensory properties of low-fat mayonnaises. Low-fat mayonnaises were prepared with four types of thickeners (MFC, chemically modified starch, native waxy corn starch, xanthan gum) at three concentrations. Higher biopolymer concentrations resulted in increased shear viscosities, G′ and G″, yield stress and enhanced lubrication (i.e. lower friction coefficients). Mayonnaises with modified starch and xanthan gum generally had higher shear viscosity and yield stress compared to mayonnaises with comparable concentrations of MFC and waxy corn starch. MFC-thickened mayonnaises had highest G’, G” and boundary friction coefficients. Sensory properties of mayonnaises were determined using the Rate-All-That-Apply (RATA) method (n = 80). Addition of xanthan gum induced high sliminess and pulpiness, and low melting, creaminess and smoothness. Sensory properties of mayonnaises with MFC were generally similar to those with modified and waxy corn starch, despite differences in appearance (increased yellowness and slightly lower glossiness). Multiple Factor Analysis revealed that more shear-thinning mayonnaises were perceived as slimy. Boundary friction was negatively correlated with stickiness, while friction at the start of the hydrodynamic regime was positively correlated with melting sensations. We conclude that microfibrillated cellulose can be used as a thickener in low-fat mayonnaise as an alternative to commercially used chemically modified starch without considerably affecting its sensory texture properties
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
Energy transfer and energy level decay processes in Tm3+-doped tellurite glass
The primary excited state decay and energy transfer processes in singly Tm3Ăľ-doped TeO2:ZnO:Bi2O3:GeO2 (TZBG) glass relating to the 3F4 ! 3H6 1.85 lm laser transition have been investigated in detail using time-resolved fluorescence spectroscopy. Selective laser excitation of the 3H4 manifold at 794 nm, the 3H5 manifold at 1220 nm, and 3F4 manifold at 1760 nm has established that the 3H5 manifold is entirely quenched by multiphonon relaxation in tellurite glass. The luminescence from the 3H4 manifold with an emission peak at 1465 nm suffers strong suppression due to cross relaxation that populates the 3F4 level with a near quadratic dependence on the Tm3Ăľ concentration. The 3F4 lifetime becomes longer as the Tm3Ăľ concentration increases due to energy migration and decreases to 2.92 ms when [Tm3Ăľ]ÂĽ4 mol. % as a result of quasi-resonant energy transfer to free OH radicals present in the glass at concentrations between 11018 cm3 and 21018 cm3. Judd-Ofelt theory in conjunction with absorption measurements were used to obtain the radiative lifetimes and branching ratios of the energy levels located below 25 000 cm1. The spectroscopic parameters, the cross relaxation and Tm3Ăľ(3F4) ! OH energy transfer rates were used in a numerical model for laser transitions emitting at 2335 nm and 1865 n
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
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